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  • 1.
    Alsmo, Thomas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    A Study of Sources of Airborne Pollutants and Poor Hygiene in Schools2010In: Indoor + Built Environment, ISSN 1420-326X, E-ISSN 1423-0070, Vol. 19, no 2, p. 298-304Article in journal (Refereed)
    Abstract [en]

    Poor indoor air quality is a large problem in Swedish schools, since the health of occupants may be affected. Resources are consumed without identification of utility indicators and there is risk of problems, even after remedial measures have been taken. This can mean both unnecessary suffering for many people and considerable resources being wasted. The building itself is often in focus and other building-related problems may be neglected. The hypothesis of the present work is that other factors than the building itself have decisive influence on indoor air quality. An assessment of these nonbuilding-related reasons for bad indoor air quality has been made in the present study using particle measurements. Results show that it is possible to decrease emissions in indoor air by over 90% through identifying and eliminating activity-related sources of airborne contaminants.

  • 2.
    Alsmo, Thomas
    et al.
    KTH, School of Technology and Health (STH), Fluid and Climate Technology (closed 20090101).
    Holmberg, Sture
    KTH, School of Technology and Health (STH), Fluid and Climate Technology (closed 20090101).
    Causes of Poor Air Quality in Swedish Schools2006Conference paper (Refereed)
    Abstract [en]

    This literature survey distinguishes between building and other factors influencing air quality. It does not identify building factors sufficient to account for occupant complaints. It concludes that buildings are often blamed for adverse health effects without sufficient grounds. The risk is there will be too much focusing on the wrong underlying problem when remedying so-called sick buildings. The study shows the importance of ensuring that factors independent of the school building, including the choices of environments and activities, are important for the indoor environment.

  • 3. Alsmo, Thomas
    et al.
    Holmberg, Sture
    KTH, School of Technology and Health (STH), Centres, Centre for Technology in Medicine and Health, CTMH.
    Sick buildings or not: Indoor air quality and health problems in schools2007In: Indoor + Built Environment, ISSN 1420-326X, E-ISSN 1423-0070, Vol. 16, no 6, p. 548-555Article in journal (Refereed)
    Abstract [en]

    Poor indoor air in schools has become a wide-spread problem with serious effects on occupant health. Resultant costs can be considerable at both local and national government levels. These include absenteeism and rehabilitation as well as building alterations and even demolition and rebuilding. This project aims to show factors contributing to health problems in Swedish schools. It includes a literature survey and particle measurements taken during various activities. Due to the fact that today there is no standard for indoor air quality (IAQ) in schools, in this project we used the outdoor air surrounding the building as an indicator. Results showed that indoor school environments had high airborne pollution levels, to a degree that probably causes health problems for many people. Regarding IAQ, this project shows the importance of taking into consideration choices in activities and furnishing of the building.

  • 4.
    Dermentzis, Georgios
    et al.
    University of Innsbruck.
    Gustafsson, Marcus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology. Högskolan Dalarna.
    Ochs, Fabian
    University of Innsbruck.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Feist, Wolfgang
    Passivhaus Institut.
    Calabrese, Toni
    University of Innsbruck.
    Oberrauch, Philipp
    University of Innsbruck.
    Evaluation of a versatile energy auditing tool2016Conference paper (Refereed)
    Abstract [en]

    Energy auditing can be an important contribution for identification and assessment of energy conservation measures (ECMs) in buildings. Numerous tools and software have been developed, with varying degree of precision and complexity and different areas of use.

     

    This paper evaluates PHPP as a versatile, easy-to-use energy auditing tool and gives examples of how it has been compared to a dynamic simulation tool, within the EU-project iNSPiRe. PHPP is a monthly balance energy calculation tool based on EN13790. It is intended for assisting the design of Passive Houses and energy renovation projects and as guidance in the choice of appropriate ECMs.

     

    PHPP was compared against the transient simulation software TRNSYS for a single family house and a multi-family house. It should be mentioned that dynamic building simulations might strongly depend on the model assumptions and simplifications compared to reality, such as ideal heating or real heat emission system. Setting common boundary conditions for both PHPP and TRNSYS, the ideal heating and cooling loads and demands were compared on monthly and annual basis for seven European locations and buildings with different floor area, S/V ratio, U-values and glazed area of the external walls.

     

    The results show that PHPP can be used to assess the heating demand of single-zone buildings and the reduction of heating demand with ECMs with good precision. The estimation of cooling demand is also acceptable if an appropriate shading factor is applied in PHPP. In general, PHPP intentionally overestimates heating and cooling loads, to be on the safe side for system sizing. Overall, the agreement with TRNSYS is better in cases with higher quality of the envelope as in cold climates and for good energy standards. As an energy auditing tool intended for pre-design it is a good, versatile and easy-to-use alternative to more complex simulation tools.

  • 5.
    Einberg, Gery
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Hagström, Kim H.
    Halton OY.
    Mustakallio, P.
    Halton OY.
    Koskela, Hannu
    Finnish Inst. of Occupational Health.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    CFD modelling of an industrial air diffuser: predicting velocity and temperature in the near zone2005In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 40, no 5, p. 601-615Article in journal (Refereed)
    Abstract [en]

    This article describes experimental and modelling results from CFD simulation of an air diffuser for industrial spaces. The main objective of this paper is to validate a manufacturer model of the diffuser. In the air diffuser, the low velocity part is placed on top of a multi-cone diffuser in order to increase airflow rates and maximize the cooling capacity of a single diffuser unit. This kind of configuration should ensure appropriate performance of industrial air diffusers, which is discussed briefly at the end of the article. The paper illustrates the importance of a simulation model jointly with the manufacturer's product model and the grid layout near the ventilation device to achieve accurate results. Parameters for diffuser modelling were adapted from literature and manufacturer's product data. Correct specification of diffuser geometry and numerical boundary conditions for CFD simulations are critical for prediction. The standard k-epsilon model was chosen to model turbulence because it represents the best-known model utilized and validated for air diffuser performance. CFD simulations were compared systematically with data from laboratory measurements; air velocity was measured by ultrasonic sensors. Results show that CFD simulation with a standard k-epsilon model accurately predicts non-isothermal airflow around the diffuser. Additionally, smoke tests revealed that the flow around the diffuser is not completely symmetrical as predicted by CFD. The cause of the observed asymmetry was not identified. This was the main reason why some simulation results deviate from the measured values.

  • 6.
    Einberg, Gery
    et al.
    KTH, Superseded Departments, KTH Syd.
    Holmberg, Sture
    KTH, Superseded Departments, KTH Syd.
    Characteristics of Particles and their Behaviour in Ventilation Air2003In: The International Journal of Ventilation, ISSN 1473-3315, E-ISSN 2044-4044, Vol. 2, no 1, p. 45-54Article in journal (Refereed)
    Abstract [en]

    The behaviour of particles in air flow is important for identifying those in various locations in ventilated space. The main reason for this study is to propose a new modelling concept to determine a realistic distribution of particles of different sizes in a space. The goal for this investigation is to divide particles into groups according to their behaviour in air and to improve the existing settling model. The growth of particle aerodynamic diameter in higher relative humidity is also presented. Here, growth of diameter and coagulation is used to determine the control volume concentration. The finite volume method is used to describe the particle concentration in the computational domain. A background to particle properties and theory for calculations are given for this purpose. Results from the literature survey reveal that modelling needs a more systematic approach to cover all sizes of particles with clear classification by behaviour.

  • 7.
    Einberg, Gery
    et al.
    KTH, Superseded Departments, KTH Syd.
    Holmberg, Sture
    KTH, Superseded Departments, KTH Syd.
    Particle Filtration in a Ventilated Room2002In: Indoor Air 2002: 9th International Conference on Indoor Air Quality and Climate / [ed] Levin, H., 2002, p. 1070-1075Conference paper (Refereed)
    Abstract [en]

    Several studies based on analytical models and numerical simulations have shown that it is difficult to control airborne particle movements in a ventilated room. However, more knowledge and information on particle characteristics and particle movements, in combination with new numerical simulation tools, have recently made it easier to estimate particle patterns. In the present paper new information is used to evaluate the role of filtration and ventilation in the particle elimination process. Key parameters found include the particle aerodynamic diameter and the particle settling velocity governed by Stokes formula. Particle dispersion and settling are highly dependent on the ventilation airflow structure. Calculations with CFD (Computational Fluid Dynamics) show characteristic patterns of particle movements in rooms with displacement ventilation.

  • 8.
    Einberg, Gery
    et al.
    KTH, Superseded Departments, KTH Syd.
    Holmberg, Sture
    KTH, Superseded Departments, KTH Syd.
    Particle Removal Efficiency in a Numerical Test Room2003In: PROCEEDINGS OF THE 4TH INTERNATIONAL SYMPOSIUM ON HEATING, VENTILATING AND AIR CONDITIONING, VOLS 1 AND 2, 2003, p. 191-197Conference paper (Refereed)
    Abstract [en]

    Particle removal efficiency in a ventilated room is investigated. This paper reports the differences in particle removal efficiency with various locations of supply and exhaust devices. Numerical simulations are carried out in a simple test room to illustrate the particle concentrations with different configurations of room ventilation. Several particle sizes are used and the influence of different flow patterns and air change rates are investigated. Particles are supplied to the room with the incoming air. Isothermal conditions with varying air supply velocities are used. Preliminary results indicate that particle removal efficiency is not predominantly influenced by air exchange rate, also the location of the supply/exhaust device is underestimated as an indicator of ventilation effectiveness.

  • 9.
    Einberg, Gery
    et al.
    KTH, Superseded Departments, KTH Syd.
    Koskela, Hannu
    Finnish Inst. of Occupational Health (FIOH).
    Holmberg, Sture
    KTH, Superseded Departments, KTH Syd.
    CFD Simulation and Measurements in Near Zone of High Induction Swirl Diffuser2004In: Roomvent 2004: Proceedings of the 9th International Conference on Air Distribution in Rooms, 2004Conference paper (Refereed)
  • 10.
    Einberg, Gery
    et al.
    KTH, Superseded Departments, KTH Syd.
    Laine, Tuomas
    Holmberg, Sture
    KTH, Superseded Departments, KTH Syd.
    CFD Modelling as a Part of Integrated Design Process for Optimised Indoor EnvironmentIn: Automation in Construction, ISSN 0926-5805, E-ISSN 1872-7891Article in journal (Other academic)
  • 11.
    Granroth, Marko
    et al.
    KTH, School of Technology and Health (STH), Fluid and Climate Technology (closed 20090101).
    Holmberg, Sture
    KTH, School of Technology and Health (STH), Fluid and Climate Technology (closed 20090101).
    Health and productivity in commercial buildings: thermal and hygienic aspects2006Conference paper (Refereed)
  • 12.
    Granroth, Marko
    et al.
    KTH, School of Technology and Health (STH), Fluid and Climate Technology (closed 20090101).
    Holmberg, Sture
    KTH, School of Technology and Health (STH), Fluid and Climate Technology (closed 20090101).
    Ventilation Strategy to improve health and productivity conditions2006In: HB - Heal. Build.: Creating Heal. Indoor Environ. People, Proc., 2006, p. 421-424Conference paper (Refereed)
    Abstract [en]

    This paper was mainly based on a literature review and focused on control of emissions and on thermal comfort conditions in office buildings. The ultimate goal was to identify optimal conditions for both human health and work productivity in office room environments. Good indoor air quality (IAQ) was to be achieved at low emission rates and correct indoor air temperature. Different ventilation and air conditioning strategies were evaluated and compared. Both energy and environmental aspects were considered. Analyses were made for emission rates of various indoor sources such as outdoor pollution, construction materials, furnishings, office-equipment and consumer products.

  • 13.
    Granroth, Marko
    et al.
    KTH, School of Technology and Health (STH), Fluid and Climate Technology (closed 20090101).
    Holmberg, Sture
    KTH, School of Technology and Health (STH), Fluid and Climate Technology (closed 20090101).
    Ventilation Strategy to Improve Health and Productivity in Swedish Offices2006In: Healthy Buildings, 4-8 June, Lisbon, Portugal, 2006: Vol IV, Finland: International Society of Indoor Air Quality and Climate (ISIAQ) , 2006, p. 421-424Conference paper (Refereed)
    Abstract [en]

    This paper was mainly based on a literature review and focused on control of emissions and on thermal comfort conditions in office buildings. The ultimate goal was to identify optimal conditions for both human health and work productivity in office room environments. Good indoor air quality (IAQ) was to be achieved at low emission rates and correct indoor air temperature. Different ventilation and air conditioning strategies were evaluated and compared. Both energy and environmental aspects were considered. Analyses were made for emission rates of various indoor sources such as outdoor pollution, construction materials, furnishings, office-equipment and consumer products. 

  • 14.
    Guha, Jaideep
    et al.
    KTH, School of Technology and Health (STH), Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Technology and Health (STH), Fluid and Climate Technology.
    A Numerical and Experimental Evaluation of a Natural Wind Driven Suction Cylinder for Building Ventilation2008In: The International Journal of Ventilation, ISSN 1473-3315, E-ISSN 2044-4044, Vol. 7, no 3, p. 197-206Article in journal (Refereed)
    Abstract [en]

    The suction cylinder described in this paper is a device to increase the ventilation flow rate, especially in naturally ventilated buildings. Outdoor wind is the driving force. The principle of operation is the development of a pressure drop created by the relative increase in flow velocity as wind driven air flows through a nozzle. This paper basically describes how this pressure drop and resultant momentum can be used to provide exhaust ventilation. The suction cylinder is particularly designed for natural and hybrid ventilation systems, especially for times when the temperature gradient between inside and outside is not enough to drive stack driven ventilation. A 1-dimensional analytical flow model was derived to establish a relationship between the volume of air entering through the inlet and the volume of air sucked by the suction cylinder. The commercial Computational Fluid Dynamics (CFD) code, Fluent, was used to visualise the flow system inside the suction cylinder. A corresponding wind tunnel experiment was also made. Preliminary results show advantages in using a suction cylinder for building ventilation.

  • 15.
    Guha, Jaideep
    et al.
    KTH, School of Technology and Health (STH), Fluid and Climate Technology (closed 20090101).
    Holmberg, Sture
    KTH, School of Technology and Health (STH), Fluid and Climate Technology (closed 20090101).
    Effectivity of a Suction Cylinder as Ventilation Equipment2006Conference paper (Refereed)
    Abstract [en]

    This paper proposes to use free wind to create suction pressure within a ventilation duct without consuming commercial energy. Like an ejector pump it creates suction pressure placed above the ventilation exhaust, which is used to draw exhaust air from the ventilation system. Discussing the possibilities of this suction cylinder concept in ventilation system is the objective of this paper. Here, a mathematical model was deduced for a suction cylinder and through CFD (Computational Fluid Dynamic) technique result was simulated later compared with theoretical model. GAMBIT was used as a preprocessor and for processing FLUENT, a commercial CFD code, was used for the simulation. Preliminary result clearly shows the positive advantages of using a suction cylinder as ventilation equipment.

  • 16.
    Guha, Jaideep
    et al.
    KTH, Superseded Departments, KTH Syd.
    Holmberg, Sture
    KTH, Superseded Departments, KTH Syd.
    Forcing natural ventilation resources in a hybrid ventilated facility at KTH2004In: Proceedings of the 9th International Conference on Air Distribution in Rooms, Coimbra, Portugal 5 - 8 Sept., 2004, 2004Conference paper (Refereed)
  • 17.
    Gustafsson, Marcus
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Service and Energy Systems. Högskolan Dalarna.
    Bales, Chris
    Högskolan Dalarna.
    Myhren, Jonn Are
    Högskolan Dalarna.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Service and Energy Systems.
    Techno-economic analysis of three HVAC retrofitting options2014Conference paper (Refereed)
    Abstract [en]

    Accounting for around 40% of the total final energy consumption, the building stock is an important area of focus on the way to reaching the energy goals set for the European Union. The relatively small share of new buildings makes renovation of existing buildings possibly the most feasible way of improving the overall energy performance of the building stock. This of course involves improvements on the climate shell, for example by additional insulation or change of window glazing, but also installation of new heating systems, to increase the energy efficiency and to fit the new heat load after renovation. In the choice of systems for heating, ventilation and air conditioning (HVAC), it is important to consider their performance for space heating as well as for domestic hot water (DHW), especially for a renovated house where the DHW share of the total heating consumption is larger.

    The present study treats the retrofitting of a generic single family house, which was defined as a reference building in a European energy renovation project. Three HVAC retrofitting options were compared from a techno-economic point of view: A) Air-to-water heat pump (AWHP) and mechanical ventilation with heat recovery (MVHR), B) Exhaust air heat pump (EAHP) with low-temperature ventilation radiators, and C) Gas boiler and ventilation with MVHR. The systems were simulated for houses with two levels of heating demand and four different locations: Stockholm, Gdansk, Stuttgart and London. They were then evaluated by means of life cycle cost (LCC) and primary energy consumption. Dynamic simulations were done in TRNSYS 17.

    In most cases, system C with gas boiler and MVHR was found to be the cheapest retrofitting option from a life cycle perspective. The advantage over the heat pump systems was particularly clear for a house in Germany, due to the large discrepancy between national prices of natural gas and electricity. In Sweden, where the price difference is much smaller, the heat pump systems had almost as low or even lower life cycle costs than the gas boiler system. Considering the limited availability of natural gas in Sweden, systems A and B would be the better options. From a primary energy point of view system A was the best option throughout, while system B often had the highest primary energy consumption. The limited capacity of the EAHP forced it to use more auxiliary heating than the other systems did, which lowered its COP. The AWHP managed the DHW load better due to a higher capacity, but had a lower COP than the EAHP in space heating mode. Systems A and C were notably favoured by the air heat recovery, which significantly reduced the heating demand.

    It was also seen that the DHW share of the total heating consumption was, as expected, larger for the house with the lower space heating demand. This confirms the supposition that it is important to include DHW in the study of HVAC systems for retrofitting.

  • 18.
    Gustafsson, Marcus
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Service and Energy Systems. Högskolan Dalarna.
    Dermentzis, Georgios
    University of Innsbruck.
    Myhren, Jonn Are
    Högskolan Dalarna.
    Bales, Chris
    Högskolan Dalarna.
    Ochs, Fabian
    Univeristy of Innsbruck.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Service and Energy Systems.
    Feist, Wolfgang
    Energy performance comparison of three innovative HVAC systems for renovation through dynamic simulation2014In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 82, p. 512-519Article in journal (Refereed)
    Abstract [en]

    In this paper, dynamic simulation was used to compare the energy performance of three innovativeHVAC systems: (A) mechanical ventilation with heat recovery (MVHR) and micro heat pump, (B) exhaustventilation with exhaust air-to-water heat pump and ventilation radiators, and (C) exhaust ventilationwith air-to-water heat pump and ventilation radiators, to a reference system: (D) exhaust ventilation withair-to-water heat pump and panel radiators. System A was modelled in MATLAB Simulink and systems Band C in TRNSYS 17. The reference system was modelled in both tools, for comparison between the two.All systems were tested with a model of a renovated single family house for varying U-values, climates,infiltration and ventilation rates.It was found that A was the best system for lower heating demand, while for higher heating demandsystem B would be preferable. System C was better than the reference system, but not as good as A or B.The difference in energy consumption of the reference system was less than 2 kWh/(m2a) betweenSimulink and TRNSYS. This could be explained by the different ways of handling solar gains, but also bythe fact that the TRNSYS systems supplied slightly more than the ideal heating demand.

  • 19.
    Gustafsson, Marcus
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology. Dalarna University, Sweden.
    Swing Gustafsson, Moa
    Högskolan Dalarna, Energiteknik; Mälardalens Högskola.
    Myhren, Jonn Are
    Högskolan Dalarna, Byggteknik.
    Bales, Chris
    Högskolan Dalarna, Energiteknik.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Techno-economic analysis of energy renovation measures for a district heated multi-family house2016In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 177, p. 108-116Article in journal (Refereed)
    Abstract [en]

    Renovation of existing buildings is important in the work towards increased energy efficiency and reduced environmental impact. The present paper treats energy renovation measures for a Swedish district heated multi-family house, evaluated through dynamic simulation. Insulation of roof and façade, better insulating windows and flow-reducing water taps, in combination with different HVAC systems for recovery of heat from exhaust air, were assessed in terms of life cycle cost, discounted payback period, primary energy consumption, CO₂ emissions and non-renewable energy consumption. The HVAC systems were based on the existing district heating substation and included mechanical ventilation with heat recovery and different configurations of exhaust air heat pump.

    Compared to a renovation without energy saving measures, the combination of new windows, insulation, flow-reducing taps and an exhaust air a heat pump gave up to 24% lower life cycle cost. Adding insulation on roof and façade, the primary energy consumption was reduced by up to 58%, CO₂ emissions up to 65% and non-renewable energy consumption up to 56%. Ventilation with heat recovery also reduced the environmental impact but was not economically profitable in the studied cases. With a margin perspective on electricity consumption, the environmental impact of installing heat pumps or air heat recovery in district heated houses is increased. Low-temperature heating improved the seasonal performance factor of the heat pump by up to 11% and reduced the environmental impact.

  • 20.
    Hesaraki, Arefeh
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Bourdakis, Eleftherios
    Ploskic, Adnan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Experimental study of energy performance in low-temperature hydronic heating systems2015In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 109, p. 108-114Article in journal (Refereed)
    Abstract [en]

    Energy consumption, thermal environment and environmental impacts were analytically and experimentally studied for different types of heat emitters. The heat emitters studied were conventional radiator, ventilation radiator, and floor heating with medium-, low-, and very-low-temperature supply, respectively. The ventilation system in the lab room was a mechanical exhaust ventilation system that provided one air change per hour of fresh air through the opening in the external wall with a constant temperature of 5 °C, which is the mean winter temperature in Copenhagen. The parameters studied in the climate chamber were supply and return water temperature from the heat emitters, indoor temperature, and heat emitter surface temperature. Experiments showed that the mean supply water temperature for floor heating was the lowest, i.e. 30 °C, but it was close to the ventilation radiator, i.e. 33 °C. The supply water temperature in all measurements for conventional radiator was significantly higher than ventilation radiator and floor heating; namely, 45 °C. Experimental results indicated that the mean indoor temperature was close to the acceptable level of 22 °C in all cases. For energy calculations, it was assumed that all heat emitters were connected to a ground-source heat pump. Analytical calculations showed that using ventilation radiator and floor heating instead of conventional radiator resulted in a saving of 17% and 22% in heat pump's electricity consumption, respectively. This would reduce the CO2 emission from the building's heating system by 21 % for the floor heating and by 18% for the ventilation radiator compared to the conventional radiator.

  • 21.
    Hesaraki, Arefeh
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Halilovic, Armin
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Basic science.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Low-temperature Heat Emission Combined with Seasonal Thermal Storage and Heat Pump2015In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 119, p. 122-133Article in journal (Refereed)
    Abstract [en]

    We studied the application of a stratified seasonal hot water storage tank with a heat pump connected to medium-, low- and very-low-temperature space heat emissions for a single-family house in Stockholm, Sweden. Our aim was to investigate the influence of heat emission design temperature on the efficiency and design parameters of seasonal storage in terms of collector area, the ratio of storage volume to collector area (RVA), and the ratio of height to diameter of storage tank. For this purpose, we developed a mathematical model in MATLAB to predict hourly heat demand in the building, heat loss from the storage tank, solar collector heat production, and heat support by heat pump as a backup system when needed. In total, 108 cases were simulated with RVAs that ranged from 2 to 5 (m3 m−2), collector areas of 30, 40, and 50 (m2), height-to-diameter-of-storage-tank ratios of 1.0, 1.5, and 2.0 (m m1), and various heat emissions with design supply/return temperatures of 35/30 as very-low-, 45/35 as low-, and 55/45 (°C) as medium-temperature heat emission. In order to find the best combination based on heat emission, we considered the efficiency of the system in terms of the heat pump work considering coefficient of performance (COP) of the heat pump and solar fraction. Our results showed that, for all types of heat emission a storage-volume-to-collector area ratio of 5 m3 m2, with a collector area of 50 m2, and a height-to-diameter ratio of 1.0 m m1 were needed in order to provide the maximum efficiency. Results indicated that for very-low-temperature heat emission the heat pump work was less than half of that of the medium-temperature heat emission. This was due to 7% higher solar fraction and 14% higher COP of heat pump connected to very-low-temperature heat emission compared to medium-temperature heat emission.

  • 22.
    Hesaraki, Arefeh
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    An investigation of energy efficient and sustainable heating systems for buildings: Combining photovoltaics with heat pump2013In: Sustainability in Energy and Buildings: Proceedings of the 4th International Conference in Sustainability in Energy and Buildings (SEB´12), Springer Berlin/Heidelberg, 2013, p. 189-197Conference paper (Refereed)
    Abstract [en]

    Renewable energy sources contribute considerable amounts of energy when natural phenomena are converted into useful forms of energy. Solar energy, i.e. renewable energy, is converted to electricity by photovoltaic systems (PV). This study was aimed at investigating the possibility of combining PV with Heat Pump (HP) (PV-HP system). HP uses direct electricity to produce heat. In order to increase the sustainability and efficiency of the system, the required electricity for the HP was supposed to be produced by solar energy via PV. For this purpose a newly-built semi-detached building equipped with exhaust air heat pump and low temperature-heating system was chosen in Stockholm, Sweden. The heat pump provides heat for Domestic Hot Water (DHW) consumption and space heating. Since selling the overproduction of PV to the grid is not yet an option in Sweden, the PV should be designed to avoid overproduction. During the summer, the HP uses electricity only to supply DHW. Hence, the PV should be designed to balance the production and consumption during the summer months. In this study two simulation programs were used: IDA Indoor Climate and Energy (ICE) as a building energy simulation tool to calculate the energy consumption of the building, and the simulation program WINSUN to estimate the output of the PV. Simulation showed that a 7.3 m2 PV area with 15 % efficiency produces nearly the whole electricity demand of the HP for DHW during summer time. As a result, the contribution of free solar energy in producing heat through 7.3 m2 fixed PV with 23o tilt is 17 % of the annual heat pump consumption. This energy supports 51 % of the total DHW demand.

  • 23.
    Hesaraki, Arefeh
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Demand Controlled Ventilation in a Combined Ventilation and Radiator System2013In: Proceedings of International Conference CLIMA 13, 2013Conference paper (Other academic)
    Abstract [en]

    With growing concerns for efficient and sustainable energy treatment in buildings there is a need for balanced and intelligent ventilation solutions. This paper presents a strategy for demand controlled ventilation with ventilation radiators, a combined heating and ventilation system. The ventilation rate was decreased from normal requirements (per floor area) of 0.375 l·s-1·m-2 to 0.100 l·s-1·m-2 when the residence building was un-occupied. The energy saving potential due to decreased ventilation and fan power was analyzed by IDA Indoor Climate and Energy 4 (ICE) simulation program. The result showed that 16 % of the original energy consumption for space and ventilation heating could be saved by utilizing ventilation on demand.

  • 24.
    Hesaraki, Arefeh
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Demand-controlled ventilation in new residential buildings: consequences on indoor air quality and energy savings2015In: Indoor + Built Environment, ISSN 1420-326X, E-ISSN 1423-0070, Vol. 24, no 2Article in journal (Refereed)
    Abstract [en]

    The consequences on indoor air quality (IAQ) and potential of energy savings when using a variable airvolume (VAV) ventilation system were studied in a newly built Swedish building. Computer simulationswith IDA Indoor Climate and Energy 4 (ICE) and analytical models were used to study the IAQ andenergy savings when switching the ventilation flow from 0.375 ls1m2 to 0.100 ls1m2 duringunoccupancy. To investigate whether decreasing the ventilation rate to 0.1 ls1m2 during unoccupancy,based on Swedish building regulations, BBR, is acceptable and how long the reduction can lastfor an acceptable IAQ, four strategies with different VAV durations were proposed. This study revealedthat decreasing the flow rate to 0.1 ls1m2 for more than 4 h in an unoccupied newly built buildingcreates unacceptable IAQ in terms of volatile organic compounds concentration. Hence, if the durationof unoccupancy in the building is more than 4 h, it is recommended to increase the ventilation rate from0.100 ls1m2 to 0.375 ls1m2 before the home is occupied. The study showed that when the investigatedbuilding was vacant for 10 h during weekdays, increasing the ventilation rate 2 h before occupantsarrive home (low ventilation rate for 8 h) creates acceptable IAQ conditions. In this system, theheating requirements for ventilation air and electricity consumption for the ventilation fan weredecreased by 20% and 30%, respectively.

  • 25.
    Hesaraki, Arefeh
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Energy Performance Evaluation of New Residential Buildings with a Low-Temperature Heating System: Results from Site Measurements and Building Energy Simulations2012In: Proceedings of The Second International Conference on Building Energy and Environment, 2012Conference paper (Other academic)
    Abstract [en]

    The purpose of this study was to investigate the national energy requirements of a modern, newly built residential development including four semi-detached houses in Stockholm, Sweden. The apartments were equipped with heat pumps utilising exhaust heat, resulting in a hydronic heating system adapted to low supply temperature. Ventilation radiators as combined ventilation and heating systems were installed in the two upper floors. Efficient preheating of incoming ventilation air in the ventilation radiator was an expected advantage. Under-floor heating with traditional air supply above windows was used on the ground floor. Energy consumption was calculated by IDA ICE 4, a building energy simulation (BES) program. In addition site measurements were made for comparison and validation of simulation results. Total energy consumption was monitored in the indoor temperature controlled buildings during the heating season. Our results so far indicate that total energy requirements in the buildings can be met in a satisfactory manner.

  • 26.
    Hesaraki, Arefeh
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Energy performance of low temperature heating systems in five new-built swedish dwellings: A case study using simulations and on-site measurements2013In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 64, p. 85-93Article in journal (Refereed)
    Abstract [en]

    In Europe, high energy consumption in built environments has raised the need for developing low energy heating systems both in new building and in retrofitting of existing buildings. This paper aims to contribute by presenting annual results of calculated and measured energy consumption in five new-built semi-detached dwellings in Stockholm, Sweden. All buildings were equipped with similar low temperature heating systems combining under-floor heating and ventilation radiators. Exhaust ventilation heat pumps supported the low temperature heating system. Buildings were modeled using the energy simulation tool IDA Indoor Climate and Energy (ICE) 4, and energy consumption of the heat pumps was measured. Results showed that calculated and measured results were generally in agreement for all five dwellings, and that the buildings not only met energy requirements of the Swedish building regulations but also provided good thermal comfort.

  • 27.
    Hesaraki, Arefeh
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Haghighat, Fariborz
    Energy-Efficient and Sustainable Heating System for Buildings: Combining seasonal heat storage with heat pumps and low-temperature heating systems2014Conference paper (Refereed)
    Abstract [en]

    During gaps between high heating demand in winter and high heating production in summer, the application of seasonal thermal energy storage becomes important. However, heat loss from seasonal thermal energy storage has always been an issue. Therefore, in order to decrease heat loss and increase solar collector efficiency, low-temperature heat storage is recommended. Nevertheless, this temperature is not sufficient throughout the heating season, which means that a heat pump is recommended in order to use this low-grade source to produce a suitable temperature for the heating system. In addition, heat pumps have better efficiency when working with low-temperature heating systems. This study investigated the seasonal thermal storage in combination with heat pump and low-temperature heating systems, with the aim of finding a suitable size for thermal energy storage and collector area. The study showed that 300 m3 of storage volume and 55 m2 of collector area could cover 80 % of the total energy demand using solar energy.

  • 28.
    Hesaraki, Arefeh
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Haghighat, Fariborz
    Seasonal thermal energy storage with heat pumps and low temperatures in building projects-A comparative review2015In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 43, p. 1199-1213Article, review/survey (Refereed)
    Abstract [en]

    Application of seasonal thermal energy storage with heat pumps for heating and cooling buildings has received much consideration in recent decades, as it can help to cover gaps between energy availability and demand, e.g. from summer to winter. This has the potential to reduce the large proportion of energy consumed by buildings, especially in colder climate countries. The problem with seasonal storage, however, is heat loss. This can be reduced by low-temperature storage but a heat pump is then recommended to adjust temperatures as needed by buildings in use. The aim of this paper was to compare different seasonal thermal energy storage methods using a heat pump in terms of coefficient of performance (COP) of heat pump and solar fraction, and further, to investigate the relationship between those factors and the size of the system, i.e. collector area and storage volume based on past building projects including residences, offices and schools.

  • 29.
    Hesaraki, Arefeh
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Myhren, Jonn Are
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Influence of Different Ventilation Levels on Indoor Air Quality and Energy Saving: a Case Study of a Renovated Single-family HouseManuscript (preprint) (Other academic)
  • 30.
    Hesaraki, Arefeh
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Myhren, Jonn Are
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Influence of different ventilation levels on indoor air quality and energy savings: A case study of a single-family house2015In: Sustainable cities and society, ISSN 2210-6707, Vol. 19, p. 165-172Article in journal (Refereed)
    Abstract [en]

    The influence of different ventilation levels on indoor air quality (IAQ) and energy savings were studied experimentally and analytically in a single-family house occupied by two adults and one infant, situated in Borlange, Sweden. The building studied had an exhaust ventilation system with a range of air flow rate settings. In order to find appropriate ventilation rates regarding CO2, relative humidity (RH) and temperature as indicators of IAQ, four ventilation levels were considered, as follows: (I) A very low ventilation rate of 0.10 L s(-1) m(-2); (II) A low ventilation rate of 0.20 L s(-1) m(-2); (III) A normal ventilation rate of 0.35 L s(-1) m(-2); (IV) A high ventilation rate of 0.70 L s(-1) m(-2). In all cases, the sensor was positioned in the exhaust duct exiting from habitable spaces. Measurements showed that, for case I, the CO2 concentration reached over 1300 ppm, which was higher than the commonly referenced threshold for ventilation control, i.e. 1000 ppm, showing unacceptable IAQQ. In case II, the CO2 level was always below 950 ppm, indicating that 0.20 L s(-1) m(-2) is a sufficient ventilation rate for the reference building. The case III showed that the ventilation rate of 0.35 L s(-1) m(-2) caused a maximum CO2 level of 725 ppm; showing the level recommended by Swedish regulations was high with respect to CO2 level. In addition, measurements showed that the RH and temperature were within acceptable ranges in all cases. An energy savings calculation showed that, in case II, the comparative savings of the combined energy requirement for ventilation fan and ventilation heating were 43% compared with case.

  • 31.
    Hesaraki, Arefeh
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Myhren, Jonn Are
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Multi-zone Demand-controlled Ventilation in Residential Buildings: An experimental case study2014Conference paper (Refereed)
    Abstract [en]

    Numerous studies have investigated the application of multi-zone demand-controlled ventilation for office buildings. However, although Swedish regulations allow ventilation rates in residential buildings to be decreased by 70 % during non-occupancy, this system is not very common in the sector. The main focus of the present study was to experimentally investigate the indoor air quality and energy consumption when using multi-zone demand-controlled ventilation in a residential building. The building studied was located in Borlänge, Sweden. This building was recently renovated with better windows with low U values, together with internally-added insulation materials. The building had natural ventilation, which decreased significantly after retrofitting and resulted in poor indoor air quality. Therefore, a controllable mechanical ventilation system was installed. The ventilation rate was controlled according to the demand in each zone of the building by CO2 concentration as an indicator of indoor air quality in habitable spaces and relative humidity and VOC level in the toilet and bathroom. The study showed that multi-zone demand-controlled ventilation significantly reduced the CO2 concentration leading to improvement in indoor air quality. However, building with demand-controlled ventilation consumed more energy than natural ventilation as it increases the ventilation loss by forcing more air into the building. Nevertheless, in the demand-controlled ventilation system, the energy consumption for the ventilation fan and ventilation loss was almost half of the constant high rate ventilation flow.

  • 32.
    Hesaraki, Arefeh
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Ploskic, Adnan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Integrating Low-temperature Heating Systems into Energy Efficient Buildings2015In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 78, p. 3043-3048Article in journal (Refereed)
    Abstract [en]

    Energy requirements for space heating and domestic hot water supplies in the Swedish building sector are responsible for almost 60 % of the total energy used. To decrease this enormous figure, energy saving measures are required, as well as opportunities to use low-temperature heating systems for increase sustainability. The present paper studies low-temperature heating systems, including heat production units (district heating or heat pumps) and heat emitting units in the room. The aim was to find an answer to the question of whether or not low-temperature heating systems are energy efficient and sustainable compared with conventional heating systems. To answer this question, we considered different efficiency aspects related to energy and exergy. The analysis showed that low-temperature heating systems are more energy efficient and environmentally friendly than conventional heating systems. This was attributed to heat pumps and district heating systems with lower temperature heat emitters using a greater share of renewable resources and less auxiliary fuels. This report discusses the pros and cons of different types of low-temperature heat emitters.

  • 33.
    Holmberg, Sture
    KTH, School of Technology and Health (STH), Fluid and Climate Technology (closed 20090101).
    Modelling of low-temperature heating systems in buildings2008In: World Renewable Energy Conference, WREC 2008, 2008Conference paper (Refereed)
  • 34.
    Holmberg, Sture
    KTH, School of Technology and Health (STH), Fluid and Climate Technology (closed 20090101).
    The influence of room air flow and turbulence on heat transfer from human body – a new comfort model consideration2008In: Indoor Air 2008, 11th International Conference on Indoor Air Quality and Climate, 2008Conference paper (Refereed)
  • 35.
    Holmberg, Sture
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Alenius, Sven
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Chen, Shih-Ying
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Drug-resistant bacteria in hospital wards - the role of ventilation2009In: 9th International Conference and Exhibition - Healthy Buildings 2009, HB 2009, 2009, p. 596-Conference paper (Refereed)
    Abstract [en]

    To limit the airborne spread of infectious agents (antibiotic-resistant bacteria) in hospital wards is an increasing world-wide concern. A multi-disciplinary Swedish research team is together with industry focusing on this problem. New knowledge is sought on how building ventilation services should be designed to minimize the risk of airborne infectious agents. In the literature there is strong and sufficient evidence to demonstrate the association between ventilation, air movements in buildings and the transmission/spread of diseases. There is, however, insufficient data to specify and quantify the minimum ventilation requirements in relation to the spread of infectious diseases via the airborne route. The latest developments in the advanced numerical simulation (CFD) methods offer new possibilities to follow the routes of airborne contaminants. Many ventilation parameters, including air flow rates, thermal and pressure conditions as well as the behavior of persons in the room are analyzed. The influence of both local air supply and local air exhaust has been analyzed and very promising results from this part of the work are presented. A bacterium spread from a patient confined to his bed was limited and for certain conditions almost eliminated. Ventilation and spatial parameter combinations to limit and prevent the spread of contaminants are mapped for different hospital wards. The risk of airborne transmission is modeled and discussed. Implementation in practice is sought via close collaboration with industry.

  • 36.
    Holmberg, Sture
    et al.
    KTH, Superseded Departments.
    Chen, Q.
    Airflow and particle control with different ventilation systems in a classroom2003In: Indoor Air, ISSN 0905-6947, E-ISSN 1600-0668, Vol. 13, no 2, p. 200-204Article in journal (Refereed)
    Abstract [en]

    Most ventilation and air conditioning systems are designed without much concern about how settling particles behave in ventilation air flows. For displacement ventilation systems, designers normally assume that all pollutants follow the buoyant air flow into an upper zone, where they are evacuated. This is, however, not always true. Previous studies show that high concentrations of settling respirable particles can be found in the breathing zone, and that the exposure rates can be a health hazard to occupants. The emphasis here is on how ventilation systems should be designed to minimize respirable airborne particles in the breathing zone. The supply and exhaust conditions of the ventilation air flow are shown to play an important role in the control of air quality. Computer simulation programs of computational fluid dynamics (CFD) type are used. Particle concentrations, thermal conditions and modified ventilation system solutions are reported.

  • 37.
    Holmberg, Sture
    et al.
    KTH, Superseded Departments, KTH Syd.
    Einberg, Gery
    KTH, Superseded Departments, KTH Syd.
    Flow behaviour in a ventilated room: measurements and simulations2002In: Proceedings of Roomvent 2002: the 8th International Conference on Air Distribution in Rooms, 2002, p. 197-200Conference paper (Refereed)
  • 38.
    Holmberg, Sture
    et al.
    KTH, Superseded Departments, KTH Syd.
    Molin, Fredrik
    KTH, Superseded Departments, KTH Syd.
    Myhren, Jonn
    KTH, Superseded Departments, KTH Syd.
    Space heating at low temperature difference between heating unit and ambient air2004In: Proceedings of the 9th International Conference on Air Distribution in Rooms, Coimbra, Portugal 5 - 8 Sept., 2004, 2004Conference paper (Refereed)
    Abstract [en]

    Rising energy prices have contributed to the development of heat pump-based heating systems in Sweden. Low flow temperature in the secondary heat distribution system to rooms is a requirement for energy-efficient systems. This increases the thermal efficiency of the heat pump and decreases thermal losses in the distribution system. Flow temperatures in water-based systems for heat distribution in buildings have been decreased from 55°C to temperatures around 30°C. This is to maximize the efficiency of heating systems that are based on heat pump technology. Different technical solutions have been suggested to guarantee space-heating requirements with low temperature difference between heating units and ambient air. Floor heating has in many cases been considered a good option, and the popularity of such systems has dramatically increased. Complicated installation work, moisture problems and slow thermal control with floor heating are reasons enough to find alternative low-temperature units for heat distribution in rooms. This may result in a combined heating and ventilation system that operates with forced convection.

  • 39.
    Holmberg, Sture
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Myhren, Jonn Are
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Ploskic, Adnan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Low-temperature heat emission with integrated ventilation air supply2010In: Proceedings of International Conference Clima 2010, 2010Conference paper (Refereed)
  • 40.
    Jin, Quan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Simone, Angela
    Olesen, Bjarne W.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Bourdakis, Eleftherios
    Laboratory study of subjective perceptions to low temperature heating systems with exhaust ventilation in Nordic countries2017In: Science and Technology for the Built Environment, ISSN 2374-4731, E-ISSN 2374-474X, Vol. 23, no 3, p. 457-468Article in journal (Refereed)
    Abstract [en]

    Given the global trends of rising energy demand and the increasing utilization of low-grade renewable energy, low-temperature heating systems can play key roles in improving building energy efficiency while providing a comfortable indoor environment. To meet the need to retrofit existing buildings in Nordic countries for greater energy efficiency, this study focused on human subjects' thermal sensation, thermal comfort, thermal acceptability, draft acceptability, and perceived air quality when three low-temperature heating systems were used: conventional radiator, ventilation radiator, or floor heating with exhaust ventilation. Human subject tests were carried out in the climate chamber at the Technical University of Denmark. In total, 24 human subjects, 12 females and 12 males, participated in the tests during the winter season. The results show that no significant differences in thermal sensation and thermal comfort between the three heating systems. Ventilation radiator promised a comfortable indoor environment with a decreased water supply temperature and floor heating with exhaust ventilation can provide a basic thermal comfort level. Thermal acceptability and draft acceptability show variations in different heating systems. Gender has significant influences on thermal sensation, draft acceptability, and preference of clo values. Personal thermal preference is observed between males and females. The males prefer to dress lighter than the females, but both can get the same thermal comfort level. It is concluded that low-temperature heating systems using exhaust air ventilation are a potentially solution when buildings are being retrofitted for improved energy efficiency and comfort of the occupants.

  • 41.
    Myhren, Jonn Are
    et al.
    KTH, School of Technology and Health (STH), Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Technology and Health (STH), Fluid and Climate Technology.
    Comfort temperatures and operative temperatures in an office with different heating methods2006In: Proceedings of the Healthy Buildings Conference: Vol. 2: Indoor Climate, 2006, Vol. 2, p. 47-52Conference paper (Other academic)
  • 42.
    Myhren, Jonn Are
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Design considerations with ventilation-radiators: Comparisons to traditional two-panel radiators2009In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 41, no 1, p. 92-100Article in journal (Refereed)
    Abstract [en]

    Performance of heat emitters in a room is affected by their interaction with the ventilation system. A radiator gives more heat output with increased air flow along its heat transferring surface, and with increased thermal difference to surrounding air. Radiator heat output and comfort temperatures in a small one-person office were Studied using different positions for the ventilation air inlet. In two of the four test cases the air inlet was placed between radiator panels to form ventilation-radiator systems. Investigations were made by CFD (Computational Fluid Dynamics) simulations, and included visualisation of thermal comfort conditions, as well as radiator heat output comparisons. The room model was exhaust-ventilated, with an air exchange rate equal to what is recommended for Swedish offices (71 s(-1) per person) and cold infiltration air (-5 degrees C) typical of a winter day in Stockholm. Results showed that under these conditions ventilation-radiators were able to create a more stable thermal climate than the traditional radiator ventilation arrangements. In addition, when using ventilation-radiators the desired thermal climate could be achieved with a radiator surface temperature as Much as 7.8 degrees C lower. It was concluded that in exhaust-ventilated office rooms, ventilation-radiators can provide energy and environmental savings.

  • 43.
    Myhren, Jonn Are
    et al.
    KTH, School of Technology and Health (STH), Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Technology and Health (STH), Fluid and Climate Technology.
    Energy savings and thermal comfort with ventilation radiators: a dynamic heating and ventilation system2007In: Proceedings of Clima 2007 WellBeing Indoors, 2007Conference paper (Other academic)
    Abstract [en]

    Studies indicate that a high ventilation rate with fresh air supply directly from outdoors gives better thermal comfort conditions, less SBS (Sick Building Syndrome) symptoms and increased work productivity. The drawbacks with a high ventilation rate in natural or exhaust ventilated buildings are normally increased energy use for heating and cold air draught. Such problems may be minimized with ventilation radiators, radiators where cold ventilation air is brought directly from outdoors through a wall channel into the radiator where it is heated before entering the room.

    This paper discusses advantages with ventilation radiators in comparison to those of traditional heating systems. Focus has been on energy aspects and thermal comfort. The main conclusions are that ventilation radiators may give a stable and uniform thermal indoor climate. The high thermal gradient between cold ventilation air and the radiator surface inside the ventilation channel also makes the ventilation radiator more efficient than other systems. A method to vary indoor climate on a daily basis according to where people stay is proposed for additional energy savings with ventilation radiators. The deductions were based on results from CFD simulations in a well validated office model.

  • 44.
    Myhren, Jonn Are
    et al.
    KTH, School of Technology and Health (STH), Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Technology and Health (STH), Fluid and Climate Technology.
    Flow patterns and thermal comfort in a room with panel, floor and wall heating2008In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 40, no 4, p. 524-536Article in journal (Refereed)
    Abstract [en]

    Thermal comfort aspects in a room vary with different space heating methods. The main focus in this study was how different heating systems and their position affect the indoor climate in an exhaust-ventilated office under Swedish winter conditions. The heat emitters used were a high and a medium-high temperature radiator, a floor heating system and large wall heating surfaces at low temperature. Computational fluid dynamics (CFD) simulations were used to investigate possible cold draught problems, differences in vertical temperature gradients, air speed levels and energy consumption. Two office rooms with different ventilation systems and heating needs were evaluated. Both systems had high air exchange rates and cold infiltration air.

    The general conclusions from this study were that low temperature heating systems may improve indoor climate, giving lower air speeds and lower temperature differences in the room than a conventional high temperature radiator system. The disadvantage with low temperature systems is a weakness in counteracting cold down-flow from ventilation supply units. For that reason the location of heat emitters and the design of ventilation systems proved to be of particular importance. Measurements performed in a test chamber were used to validate the results from the CFD simulations.

  • 45.
    Myhren, Jonn Are
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Improving the thermal performance of ventilation radiators: The role of internal convection fins2011In: International journal of thermal sciences, ISSN 1290-0729, E-ISSN 1778-4166, Vol. 50, no 2, p. 115-123Article in journal (Refereed)
    Abstract [en]

    This paper deals with heat output optimization of a ventilation radiator by varying the distribution of vertical longitudinal convection fins. A ventilation radiator, which combines ventilation air supply and heat emission to the room, has a higher driving force on air in between the radiator panels compared to traditional radiators and can for this reason have more heat transferring surfaces to improve thermal efficiency. Improving the thermal efficiency means a lower water temperature is required for heating and energy can be saved in production and distribution of heat in systems with heat pumps, district heating or similar. The investigation was made using Computational Fluid Dynamics (CFD) simulations while analytical calculations were used for verification of different flow and heat transfer mechanisms. Results showed that heat transfer can be increased in the section where ventilation air is brought into the room by slightly changing the geometry of the fins, decreasing the fin to fin distance and cutting off a middle section of the fin array. This change in internal design could mean considerable increase in thermal efficiency for the ventilation radiator as a whole.

  • 46.
    Myhren, Jonn Are
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Performance evaluation of ventilation radiators2010In: International journal of thermal sciences, ISSN 1290-0729, E-ISSN 1778-4166Article in journal (Refereed)
  • 47.
    Myhren, Jonn Are
    et al.
    KTH, School of Technology and Health (STH), Fluid and Climate Technology (closed 20090101).
    Holmberg, Sture
    KTH, School of Technology and Health (STH), Fluid and Climate Technology (closed 20090101).
    Summertime cooling with ventilation radiators2007In: IAQVEC 2007 Proceedings - 6th International Conference on Indoor Air Quality, Ventilation and Energy Conservation in Buildings: Sustainable Built Environment, 2007, p. 533-538Conference paper (Refereed)
    Abstract [en]

    Ventilation radiators, heat emitters where cold ventilation air is brought directly from outdoors into the room via heated radiator surfaces, are becoming more and more common in Scandinavia. Because these systems combine both heating and ventilation several interesting aspects arise that may be used to save energy and improve indoor thermal climate. The heating aspects in wintertime have been discussed in previous papers from KTH STH. This study investigates whether ventilation radiators may be used for cooling in summertime. Results from the study show that condensation of water is the main problem to tackle when ventilation radiators are used for cooling purposes. It is difficult to avoid condensation, especially inside the ventilation channel where incoming ventilation air comes into contact with chilled radiator surfaces. The problem increases with increased temperature difference between radiator surface and ventilation air. This is why ventilation radiators seem unsuitable for cooling in summertime without risking condensation of water. However, if condensation of water is allowed in the ventilation channel only, ventilation radiators may be functional for cooling. The trick is to find a way to drain water from the ventilation channel to avoid hygiene problems.

  • 48.
    Myhren, Jonn Are
    et al.
    KTH, School of Technology and Health (STH), Fluid and Climate Technology (closed 20090101).
    Holmberg, Sture
    KTH, School of Technology and Health (STH), Fluid and Climate Technology (closed 20090101).
    Thermal comfort with low temperature heating2006Conference paper (Other academic)
  • 49.
    Novakovic, Krsta
    et al.
    KTH, Superseded Departments, KTH Syd.
    Holmberg, Sture
    KTH, Superseded Departments, KTH Syd.
    The influence of air speed and turbulence intensity on thermal comfort in vehicles2004In: Proceedings of the 9th International Conference on Air Distribution in Rooms, Coimbra, Portugal 5 - 8 Sept., 2004, 2004Conference paper (Refereed)
  • 50.
    Pitsch, Stephan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Angster, Judit
    Fraunhofer Institute (Bauphysik).
    Research into the effects of temperature on organ tuning2010In: ISO journal: The magazine of the International Society of Organbuilders, ISSN 1017-7515, no 34, p. 34-44Article in journal (Refereed)
12 1 - 50 of 86
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