13 Space heating and cooling
condenser of the HVAC system and at the same time storing this waste heat in the aquifer. Cooling with groundwater at around 18°C instead of utilizing outside summer air at 30-35°C decreases consumption of electrical energy significantly. In addition, stored heat can be recovered when it is needed in winter. The HVAC system with ATES started operation in August 2001 in cooling mode with an average coefficient of performance (COP) of 4.18, which is almost 60% higher than a conventional system.
04/03020 Building design and energy end-use characteristics of high-rise residential buildings in Hong Kong Wan, K. S. Y. and Yik, F. W. H. Applied Energy, 2004, 78, (1), 19-36. Surveys have been conducted to obtain information about the building design and energy end-use characteristics of high-rise residential buildings in Hong Kong. The building design characteristics data obtained include the floor areas of residential flats, the ratios of the areas of bedrooms and living and dining rooms to the total flat area, the window-to-wall area ratios, the types of fenestration, and the external-shading devices in facades of residential buildings. The energy data obtained include the household energy and electricity uses, and the type and quantity of appliances used in residential units. The saturation rates of various domestic appliances and their utilization patterns, and the annual energy use for air-conditioning and water heating in residential units in Hong Kong have been estimated based on the collected data.
04•03021 Contribution of indoor exposed massive wood to a good indoor climate: in situ measurement campaign Hameury, S. and Lundstr6m, T. Energy and Buildings, 2004, 36, (3), 281-292. An indoor climate is mainly influenced by factors including heating, ventilation and air-conditioning, building envelope and materials, occupants, furniture, and service life of the building components. These last few years, the usual porous medium provided in wall and flooring constructions have been pointed out as possible passive systems capable of buffering the indoor climate variations in terms of temperature and humidity. The objective for the ongoing project is, therefore, to evaluate the possibility of ensuring an indoor climate within an acceptable range making use of large exposed massive wood surfaces. An experimental study, being performed in four occupied apartments of a multi-storey residential building in Sweden, is described in this paper. A brief analysis of the in sitn recordings is also included. The temperature and relative humidity recordings show fairly good agreement with the ASHRAE recommended values for a good indoor climate excepted during the cold periods revealing low indoor relative humidity. The first results show evidences that a large area of exposed massive wood contributes to buffer the indoor temperature variations. Furthermore, this far it does not shows evidences that a large area of exposed massive wood is able to damp the daily fluctuations in relative humidity.
04•03022 Cooling-load density optimization for a regenerated air refrigerator Zhou, S. et al. Applied Energy, 2004, 78, (3), 315-328. A performance analysis and optimization of a regenerated air refrigeration cycle with variable-temperature heat-reservoirs is carried out by taking the cooling-load density, i.e., the ratio of cooling load to the maximum specific volume in the cycle, as the optimization objective using finite-time thermodynamics (FTT) or entropy-generation mini- mization (EGM). The model of a regenerated air refrigerator is presented, and analytical relationships between cooling-load density and pressure ratio, as well as between coefficient of performance (COP) and pressure ratio are derived. The irreversibilities considered in the analysis include the heat-transfer losses in the hot- and cold-side heat-exchangers and the regenerator, the non-isentropic compression and expansion losses in the compressor and expander, and the pressure-drop losses in the piping. The cycle performance comparison under maximum cooling-load density and maximum cooling-load conditions is performed via detailed numerical calculations. The optimal performance characteristics of the cycle are obtained by optimizing the pressure ratio of the compressor, and searching for the optimum distribution of heat-conductances of the hot- and cold-side heat-exchangers and regenerator for the fixed total heat-exchanger inventory. The effect of heat capacity rate matching between the working fluid and heat reservoirs on the cooling-load density is analysed for the cycle. The influences of the effectiveness of the regenerator as well as the hot- and cold-side heat-exchangers, the efficiencies of the expander and the compressor, the pressure-recovery coefficient, and the temperature ratio of the heat reservoirs on the cooling-load density and COP are examined and illustrated by numerical examples.
426 Fuel and Energy Abstracts November 2004
04/03023 Development of an optimal preventive maintenance model based on the reliability assessment for air-conditioning facilities in office buildings Kwak, R.-Y.R.-Y. et al. Building and Environment, 2004, 39, (10), 1141 1156. The purpose of this study is to examine the failure trend of HVAC systems in high-rise office buildings using the reliability assessment, and propose a method of predicting an optimal inspection period for condition-based preventive maintenance (CBM) using the Monte Carlo method, in point of view of randomness and independency between failure and inspection. This study describes the probability process method of measuring the effect of condition-based preventive maintenance on HVAC system's reliability and optimization of condition-based preventive maintenance. A simulation model is presented to analyse condition-based preventive maintenance through a fixed-period maintenance inspection to detect failure occurring. Based on this simulation model, the effects of condition-based preventive maintenance on units of HVAC system's reliability are quantitatively obtained, and the mean time between failures of units under CBM action is suggested. In addition, the basic characteristics of the condition-based preventive maintenance are analysed by sensitivity analysis. As a result of this study, the method to predict an optimal inspection period is also suggested in order to increase the reliability of units, and effect on expected profit of optimal preventive maintenance inspection period is computed.
04/03024 Effects of a droplet on near-wall transport phenomena in turbulent downward liquid-liquid flow Hagiwara, Y. Journal of Enhanced Heat Transfer, 2003, 10, (1), 81-93. A visualization measurement was conducted for isothermal turbulent water downward flow with rising droplets. Wobbling motion is observed for the droplets near the duct wall. The droplet wake flow with the asymmetric evolution of vortices modifies the near-wall turbulence: the lift-up of low-speed fluid is not observed clearly near the droplet. A direct numerical simulation was also carried out for non- isothermal turbulent downward flow in a vertical channel with an immiscible droplet whose density is lower than that of the flowing fluid and found that low-temperature fluid is pushed into the buffer region by the wallward flow along the cap of the droplet. The outward flow in the droplet wake causes the liftup of the hot fluid adjacent to the wall. These flows enhance the near-wall heat transfer.
04/03025 Energy and chemical composition dependence of mass attenuation coefficients of building materials Singh, C. et al. Annals of Nuclear Energy, 2004, 31, (10), 1199-1205. Total and partial mass attenuation coefficients of different building materials (glass, concrete, marble, fly-ash, cement and lime) have been computed over a wide energy range of 10 keV to 100 GeV. For the total mass attenuation coefficient, ~ttota I a significant variation is observed in low and high energy regions whereas there is no notable change in ~total in the intermediate region. The results of ~ttota I have been discussed on the basis of obtained attenuation coefficients of different partial photon interaction processes.
04/03026 Enhanced heat transfer rates caused by magnetic field for natural convection of air in an inclined cubic enclosure Noda, R. et al. Journal of Enhaneed Heat Transfer, 2003, 10, (1), 159 170. Enhancement of heat transfer rates of natural convection of air was considered in a cubic enclosure heated from one vertical wall and cooled from an opposing wall with one magnetic coil placed on a plane with the top wall. With electric current in this coil, the magnetic field is induced in the enclosure to effect the natural convection of air. Magnetizing (or magnetic) force has been known to be proportional to the magnetic susceptibility and the gradient of a square of magnetic induction. In the momentum equation, this magnetizing force was considered. The magnetic induction was computed from Biot-Savart 's law. Characteristic dimensionless values are the Rayleigh number, the Prandtl number, and 7 which represents the strength of the magnetiz- ing force. Sample computations were carried out for the parameter ranges Pr = 0.71, Ra = 105, and 3' = 0-100. When the enclosure was kept horizontal, the average Nusselt number at Ra - i0 s was 4.48 at "7 = 0 without a magnetic field. Then it became 3.97 at ,,/ = 1,5.16 at 3' 10, and 12.5 at 3' = 100. When the enclosure was turned upside down, it became 4.89 at 3' - 1,6.97 at "/ - 10, and 13.0 at "7 = 100. The effect of inclination of the enclosure was further considered by keeping the hot and cold walls in a vertical gravitational direction.
04/03027 Enhancement of ventilation performance of a residential split-system air-conditioning unit Sekhar, S. C. Energy and Buildings, 2004, 36, (3), 273-279. The design of ventilation performance of air-conditioning systems in large commercial and office buildings is quite established. However, it is not the same with the designs of air-conditioning systems in most
