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00804 Demand controlled ventilation. A case study for existing Swedish multifamily buildings
13 Space heating and cooling 05•00803 Combined cogeneration and liquid-desiccant system applied in a demonstration building Liu, X. H. et al. Energy and Buildings, 2004, 36, (9), 945 953. A hybrid H V A C system, consisting of cogenerators, liquid-desiccant system (LDS), vapour compression and absorption chillers, gas boiler and storage tanks, is established in this paper, which is used to match the power and thermal demands of a 20 000 m s demonstration building in Beijing, China. Both power produced and waste heat exhausted from the cogenerators are fully used in different stages of the building energy demand according to their energy quality levels, where power is used to meet the electrical load and waste heat is used to regenerate desiccant, drive absorption chiller in summer and heat the building in winter. By applying independent humidity control strategy in this system, a higher indoor comfort level would be obtained. Simulation analysis is carried out to analyse the system performance under different operation modes and conditions. It shows that energy storage devices play an important role in the proposed system. Compared with the conventional H V A C system, the hybrid system is found to be more energy efficient and environmental friendly. It needs only 2 years to recover the extra initial cost and CO2 emission is reduced by about 4O%.
05•00804 Demand controlled ventilation. A case study for existing Swedish multifamily buildings Pavlovas, V. Energy and Buildings, 2004, 36, (10), 1029-1034. The aim of the work accounted for in this paper has been to investigate a demand controlled ventilation (DCV) system for a typical Swedish multifamily building with exhaust ventilation. Another aim has been to apply and evaluate the IDA Indoor Climate and Energy (ICE) simulation software in this application. The work has been related to a renovation project of a large number of apartments with exhaust ventilation systems recently carried out by a Swedish municipal housing association. A typical apartment, chosen among 1000 existing apartments, has been modelled using IDA Climate and Energy simulation software. Four exhaust ventilation system concepts have been evaluated: (1) reference system with constant air volume flow, (2) demand controlled ventilation system: carbon dioxide control, variable air flow, (3) demand controlled ventilation system: humidity control, variable air flow and (4) demand controlled ventilation system: occupancy control, variable air flow. The simulations show that it would be possible to achieve energy savings using occupancy and/or humidity controlled ventilation to reduce the average ventilation flow rate while keeping an acceptable indoor climate. Based on the simulation results, a demand controlled ventilation system is developed and implemented in occupied apartments in order to investigate the performance. A measurement based validation of the simulation program indicates that it can be applied reliably.
05•00805 Energy modelling of district cooling system for new urban development Chow, T. T. et al. Energy and Buildings, 2004, 36, (1 l), 1153-1162. District cooling technology is advantageous in warm and hot climatic regions, in that chilled water from a central refrigeration plant is delivered through a distribution network to groups of buildings. The technology is most suitable for new urban developments where system design and construction receive much freedom. With a focus on the energy use, this paper outlines an energy modelling methodology and decision approach to derive the most desirable scheme for a given project. The process involves a series of building design load computation, dynamic simulation, and plant energy consumption analyses for different phases of development. A proposed scheme for the South East Kowtoon Development Project in Hong Kong is quoted as an example to illustrate the approach.
05•00806 Exergoeconomic optimisation of an airconditioning rotary regenerator: effect of matrix thermal conductivity on its performance Jassim, R. K. and Khir, T. International Journal of Exergy, 2004, 1, (2), 215-236. The purpose of this paper is to demonstrate the importance of the use of exergoeconomic analysis in the optimization of the geometry of a rotary regenerator. The optimum geometry of a rotary regenerator is determined using the unit cost of the exergy of the warm air delivered as the objective function. The running cost is determined using different unit costs for the pressure component of exergy, /~Ap, and the thermal component of exergy,/)AT, which are evaluated separately. A mathematical model using a finite difference technique of matrix thermal conductivity and heat transfer is presented and the governing differential equations have been formulated in terms of the characteristic dimensionless groups (II,, At and Z,) and the effect of two different materials is examined. The effect of variation of the regenerator geometry on the objective function is examined and recommendations are made for the selection of the most appropriate parameters for a
118
Fuel and Energy Abstracts
March 2005
rotary regenerator. The results show that the effect of thermal conductivity on the minimum exergoeconomic objective function is slightly over 1% for mild steel and 3.374% for aluminium.
05•00807 Experimental heat transfer coefficients during refrigerant vaporisation and condensation inside herringbone-type plate heat exchangers with enhanced surfaces Longo, G. A. et al. International Journal of Heat and Mass Transfer, 2004, 47, (19-20), 4125-4136. This paper presents the experimental work carried out to apply 'crossgrooved' surfaces to refrigerant vaporization and condensation inside plate heat exchangers (PHE) with herringbone macro-scale corrugation. This paper also investigates the effect of an increase in the surface roughness of the plate on refrigerant two-phase heat transfer inside PHE. The enhanced surfaces are experimentally evaluated both in vaporization and condensation tests with refrigerant 22, and compared against a PHE with a smooth surface. The experimental results show that the 'cross-grooved' surface is useful both in vaporization and condensation, whereas the increase in surface roughness is useful only in vaporization. The 'cross-grooved' surface gives an increase in the heat transfer coefficient from 30% to 40% in vaporization to 60% in condensation with respect to a PHE with a smooth surface. The enhancement in heat transfer coefficient is higher than the simple increase in heat transfer surface area. A fair agreement was found between present experimental data and semi-empirical correlations both for condensation and vaporization inside PHE.
05•00808 Heat transfer and fluid flow analysis in plate-fin and tube heat exchangers with a pair of block shape vortex generators Leu, J.-S. et al. International Journal q/' Heat and Mass Transfer, 2004, 47, (19-20), 43274338. Numerical and experimental analyses were carried out to study the heat transfer and flow in the plate-fin and tube heat exchangers with inclined block shape vortex generators mounted behind the tubes. The effects of different span angles a ( a = 3 0 °, 45 ° and 60 °) are investigated in detail for the Reynolds number ranging from 400 to 3000. Numerical simulation was performed by a 3D turbulence analysis of the heat transfer and fluid flow. Experiments were carried out by an infrared thermovision and a water tunnel system, respectively, to visualize the temperature distribution and local flow structure. The results indicated that the proposed heat transfer enhancement technique is able to generate longitudinal vortices and to improve the heat transfer performance in the wake regions. The case of a = 4 5 ° provides the best heat transfer augmentation. A reduction in fin area of 25% may be obtained if vortex generators embedded fins are used in place of plain fins at ReDh = 500.
05•00809 Investigation of indoor thermal comfort under transient conditions Kaynakli, O. and Kilic, M. Building and Environment, 2005, 40, (2), 165174. In industrialized countries about 90% of the time is spent indoors. In indoor, thermal comfort can be basically predicted by the environmental parameters such as temperature, humidity, air velocity and by the personal parameters as activity and clothing resistance. In this study, a mathematical model of thermal interaction between human body and environment was established and the effect of clothing and air velocity was examined under transient conditions. By the developed model, h u m a n body has been separated to 16 segments and possible local discomforts are taken into consideration. Using the model, changes in the sensible and latent heat losses, skin temperature and wettedness, thermal comfort indices were calculated. In a hot environment latent heat loss increases by means of sweating. Because of over wetted skin, comfort sense goes worse. Especially, at feet and pelvis skin wettedness reaches maximum level. Sensible and latent heat losses rise and the skin temperature and wettedness decrease with increasing air velocity.
05•00810 Life cycle assessment of residential ventilation units in a cold climate Nyman, M. and Simonson, C. J. Building and Environment, 2005, 40, (1), 15-27. The life cycle assessment (LCA) methodology is used in this paper to assess the environmental impacts of residential ventilation units over a 50-year life cycle in Finland. Quantifying the consumption of the energy and material resources during the life cycle permits the estimation of the harmful emissions into the environment (air, water and soil) and the potential changes in the environment (climate change, acidification and ozone production). Two different ventilation units are evaluated, both of which include air-to-air energy exchangers. The research demonstrates that a residential ventilation unit, with a function of providing 50 1/s of outdoor ventilation air, but not heating the air, has a net positive impact on the environment when it is
05•00804 Demand controlled ventilation. A case study for existing Swedish multifamily buildings Pavlovas, V. Energy and Buildings, 2004, 36, (10), 1029-1034. The aim of the work accounted for in this paper has been to investigate a demand controlled ventilation (DCV) system for a typical Swedish multifamily building with exhaust ventilation. Another aim has been to apply and evaluate the IDA Indoor Climate and Energy (ICE) simulation software in this application. The work has been related to a renovation project of a large number of apartments with exhaust ventilation systems recently carried out by a Swedish municipal housing association. A typical apartment, chosen among 1000 existing apartments, has been modelled using IDA Climate and Energy simulation software. Four exhaust ventilation system concepts have been evaluated: (1) reference system with constant air volume flow, (2) demand controlled ventilation system: carbon dioxide control, variable air flow, (3) demand controlled ventilation system: humidity control, variable air flow and (4) demand controlled ventilation system: occupancy control, variable air flow. The simulations show that it would be possible to achieve energy savings using occupancy and/or humidity controlled ventilation to reduce the average ventilation flow rate while keeping an acceptable indoor climate. Based on the simulation results, a demand controlled ventilation system is developed and implemented in occupied apartments in order to investigate the performance. A measurement based validation of the simulation program indicates that it can be applied reliably.
05•00805 Energy modelling of district cooling system for new urban development Chow, T. T. et al. Energy and Buildings, 2004, 36, (1 l), 1153-1162. District cooling technology is advantageous in warm and hot climatic regions, in that chilled water from a central refrigeration plant is delivered through a distribution network to groups of buildings. The technology is most suitable for new urban developments where system design and construction receive much freedom. With a focus on the energy use, this paper outlines an energy modelling methodology and decision approach to derive the most desirable scheme for a given project. The process involves a series of building design load computation, dynamic simulation, and plant energy consumption analyses for different phases of development. A proposed scheme for the South East Kowtoon Development Project in Hong Kong is quoted as an example to illustrate the approach.
05•00806 Exergoeconomic optimisation of an airconditioning rotary regenerator: effect of matrix thermal conductivity on its performance Jassim, R. K. and Khir, T. International Journal of Exergy, 2004, 1, (2), 215-236. The purpose of this paper is to demonstrate the importance of the use of exergoeconomic analysis in the optimization of the geometry of a rotary regenerator. The optimum geometry of a rotary regenerator is determined using the unit cost of the exergy of the warm air delivered as the objective function. The running cost is determined using different unit costs for the pressure component of exergy, /~Ap, and the thermal component of exergy,/)AT, which are evaluated separately. A mathematical model using a finite difference technique of matrix thermal conductivity and heat transfer is presented and the governing differential equations have been formulated in terms of the characteristic dimensionless groups (II,, At and Z,) and the effect of two different materials is examined. The effect of variation of the regenerator geometry on the objective function is examined and recommendations are made for the selection of the most appropriate parameters for a
118
Fuel and Energy Abstracts
March 2005
rotary regenerator. The results show that the effect of thermal conductivity on the minimum exergoeconomic objective function is slightly over 1% for mild steel and 3.374% for aluminium.
05•00807 Experimental heat transfer coefficients during refrigerant vaporisation and condensation inside herringbone-type plate heat exchangers with enhanced surfaces Longo, G. A. et al. International Journal of Heat and Mass Transfer, 2004, 47, (19-20), 4125-4136. This paper presents the experimental work carried out to apply 'crossgrooved' surfaces to refrigerant vaporization and condensation inside plate heat exchangers (PHE) with herringbone macro-scale corrugation. This paper also investigates the effect of an increase in the surface roughness of the plate on refrigerant two-phase heat transfer inside PHE. The enhanced surfaces are experimentally evaluated both in vaporization and condensation tests with refrigerant 22, and compared against a PHE with a smooth surface. The experimental results show that the 'cross-grooved' surface is useful both in vaporization and condensation, whereas the increase in surface roughness is useful only in vaporization. The 'cross-grooved' surface gives an increase in the heat transfer coefficient from 30% to 40% in vaporization to 60% in condensation with respect to a PHE with a smooth surface. The enhancement in heat transfer coefficient is higher than the simple increase in heat transfer surface area. A fair agreement was found between present experimental data and semi-empirical correlations both for condensation and vaporization inside PHE.
05•00808 Heat transfer and fluid flow analysis in plate-fin and tube heat exchangers with a pair of block shape vortex generators Leu, J.-S. et al. International Journal q/' Heat and Mass Transfer, 2004, 47, (19-20), 43274338. Numerical and experimental analyses were carried out to study the heat transfer and flow in the plate-fin and tube heat exchangers with inclined block shape vortex generators mounted behind the tubes. The effects of different span angles a ( a = 3 0 °, 45 ° and 60 °) are investigated in detail for the Reynolds number ranging from 400 to 3000. Numerical simulation was performed by a 3D turbulence analysis of the heat transfer and fluid flow. Experiments were carried out by an infrared thermovision and a water tunnel system, respectively, to visualize the temperature distribution and local flow structure. The results indicated that the proposed heat transfer enhancement technique is able to generate longitudinal vortices and to improve the heat transfer performance in the wake regions. The case of a = 4 5 ° provides the best heat transfer augmentation. A reduction in fin area of 25% may be obtained if vortex generators embedded fins are used in place of plain fins at ReDh = 500.
05•00809 Investigation of indoor thermal comfort under transient conditions Kaynakli, O. and Kilic, M. Building and Environment, 2005, 40, (2), 165174. In industrialized countries about 90% of the time is spent indoors. In indoor, thermal comfort can be basically predicted by the environmental parameters such as temperature, humidity, air velocity and by the personal parameters as activity and clothing resistance. In this study, a mathematical model of thermal interaction between human body and environment was established and the effect of clothing and air velocity was examined under transient conditions. By the developed model, h u m a n body has been separated to 16 segments and possible local discomforts are taken into consideration. Using the model, changes in the sensible and latent heat losses, skin temperature and wettedness, thermal comfort indices were calculated. In a hot environment latent heat loss increases by means of sweating. Because of over wetted skin, comfort sense goes worse. Especially, at feet and pelvis skin wettedness reaches maximum level. Sensible and latent heat losses rise and the skin temperature and wettedness decrease with increasing air velocity.
05•00810 Life cycle assessment of residential ventilation units in a cold climate Nyman, M. and Simonson, C. J. Building and Environment, 2005, 40, (1), 15-27. The life cycle assessment (LCA) methodology is used in this paper to assess the environmental impacts of residential ventilation units over a 50-year life cycle in Finland. Quantifying the consumption of the energy and material resources during the life cycle permits the estimation of the harmful emissions into the environment (air, water and soil) and the potential changes in the environment (climate change, acidification and ozone production). Two different ventilation units are evaluated, both of which include air-to-air energy exchangers. The research demonstrates that a residential ventilation unit, with a function of providing 50 1/s of outdoor ventilation air, but not heating the air, has a net positive impact on the environment when it is