01220 Application of CFD in evaluation and energy-efficient design of air curtains for horizontal refrigerated display cases

13 Space heating and cooling mounted in staggered pattern, are oriented parallel to the fluid flow and are soldered to the underside of absorber plate. They are characterized by high heat transfer area per unit volume. High thermal performances are obtained with low pressure losses and in consequence a low electrical power consumption by the fan in comparison to the flat plate collector. The experimental results are all so compared by using two types of transparent cover; double and triple.

13

SPACE HEATING A N D COOLING

05•01217 A feasibility study of using thermal energy storage in a conventional air-conditioning system Hussain, M. M. et al. International Journal of Energy Research, 2004, 28, (11), 955-967. This paper deals with the simulation of thermal energy storage (TES) system for H V A C applications. TES is considered to be one of the most preferred demand side management technologies for shifting cooling electrical demand from peak daytime hours to off peak night hours. TES is incorporated into the conventional H V A C system to store cooling capacity by chilling ethylene glycol, which is used as a storage medium. The thermodynamic performance is assessed using exergy and energy analyses. The effects of various parameters such as ambient temperature, cooling load, and mass of storage are studied on the performance of the TES. A full storage cycle, with charging, storing and discharging stages, is considered. In addition, energy and exergy analysis of the TES is carried out for system design and optimization. The temperature in the storage is found to be as low as 6.4°C after 1 day of charging without load for a mass of 250 000 kg. It is found that COP of the H V A C system increases with the decrease of storage temperature. Energy efficiency of the TES is found to be 80% for all the mass flow rate of the discharging fluid, whereas exergy efficiency varies from 14 to 0.5%. This is in fact due to the irreversibilities in a TES process destroy a significant amount of the input exergy, and the TES exergy efficiencies therefore become always lower than the corresponding energy efficiencies.

05101218 A heat transfer simulation study of a multicompartment isothermal liquid foodstuff tank tested according to the international ATP Agreement Chatzidakis, S. K. and Chatzidakis, K. S. Energy Conversion and Management, 2005, 46, (2), 197-221. Isothermal tanks are widely used for transport of perishable liquid foodstuffs like milk, wine, juice etc., and according to the international ATP Agreement, they have to be tested periodically in officially recognized national ATP Test Stations to ensure that they meet the specifications. The testing of a multi-compartment isothermal tank presents special difficulties in comparison to the testing of a refrigerated truck because of the number of compartments that have to be measured. The instrumentation needed for testing a specimen in these cases is complex and that is why only a few ATP Test Stations can conduct such tests. In this study, a heat transfer numerical simulation is described of a multi-compartment isothermal tank for the transport of perishable liquid foodstuffs tested at a new environmental ATP chamber recently constructed at the Zografou Campus of the National Technical University in Athens. The tests were conducted according to the regulations specified in the United Nations ATP Agreement. A transient finite difference model is developed for a typical specimen multi-compartment isothermal tank tested inside an ATP Testing Chamber. To adjust the cooling or heating system, a PI controller is used. The simulation results are compared to experimental measurements under real conditions and show good agreement. The study describes also a method for testing multi-compartment isothermal tanks according to the ATP specifications using only the measuring equipment normally existing in every ATP laboratory. With the proposed method, the testing of a three-compartment liquid foodstuff tank is possible using only one heating capacity adjuster, e.g. one PI controller and one thyristor instead of the three independent PI controllers and three thyristors normally needed in order to adjust the required heating capacity inside each compartment.

05101219 A new solar powered adsorption refrigerator with high performance Hildbrand, C. et al. Solar Energy, 2004, 77, (3), 311-318. An adsorptive solar refrigerator was built in September 2000 in Yverdon-les-Bains, Switzerland. The adsorption pair is silicagel + water. The machine does not contain any moving parts, does not consume any mechanical energy except for experimental purposes and is relatively easy to manufacture. Cylindrical tubes function as both the adsorber system and the solar collector (flat-plate, 2 m e double glazed);

182

Fuel and Energy Abstracts May 2005

the condenser is air-cooled (natural convection) and the evaporator contains 40 1 of water that can freeze. This ice functions as a cold storage for the cabinet (320 1). The first tests (September 2000) showed a very promising performance, with a gross solar cooling COPsR of 0.19. After minor modifications, a second test series was carried out during summer 2001. This test series shows how the external parameters influence the machine with respect to the C O P s e (irradiation and external temperature). The latter varies between 0.10 and 0.25 with a mean value of 0.16. These values are higher than those obtained by earlier solar powered refrigerators (0.10-0.12). This paper describes the principle of the cycle, the different components of the machine, and the test procedure. The test procedure includes a constant daily cooling requirement. The experimental results presented were taken over a period of two months.

05101220 Application of CFD in evaluation and energyefficient design of air curtains for horizontal refrigerated display cases Cui, J. and Wang, S. International Journal of Thermal Sciences, 2004, 43, (10), 993-1002. Horizontal refrigerated display cases consume a large amount of energy and interact closely with the indoor environment in supermarkets. How to design a high energy-efficient display case has long been an important task of the industry and an important topic for research. This paper uses the computational fluid dynamics (CFD) method to evaluate the energy performance of the air curtain for horizontal refrigerated display cases and to optimize its design. The CFD method is also validated by comparing the CFD calculation results with experimental results. Using the CFD method, the key factors that influence the cooling load of the air curtain in the display cases are studied. Qualitative designs are then proposed to make the air curtain more energy-efficient.

05101221 Kong

Applying district-cooling technology in Hong

Chow, T. T. et al. Applied Energy, 2004, 79, (3), 275-289. Land reclamation has been a long-term government policy of expanding the Hong Kong urban areas along the waterfront. These flat pieces of land are ideal sites for the application of district-cooling technology. At a central refrigeration plant, chilled water is generated and supplied to a district to support the air-conditioning systems in buildings. Because of the large-scale production, together with the convenience of bringing in seawater for condenser cooling, the chiller plant is higher in efficiency than those in individual buildings. The customers can also use the building space of their own more effectively. In this paper, the technical requirements and the cooling scheme options in the context of the subtropical urban environment are discussed. A government-commissioned feasibility study of a proposed district-cooling site in Hong Kong, with an estimated 200 MW coolingplant capacity is then described. The proposed system and the methodology in predicting the thermal demand and the energy consumptions are introduced.

05101222 Assessment of productivity loss in airconditioned buildings using PMV index Kosonen, R. and Tan, F. Energy and Buildings, 2004, 36, (10), 987-993. This theoretical study reports on the assessment of productivity loss in air-conditioned office buildings using the PMV approach and makes use of previously published reviews as the basis to compare and to relate how the productivity loss could be minimized through improved thermal comfort design criteria. The finding shows that task-related performance is significant correlated with the human perception of thermal environment that in turn is dependent on temperatures. Different combinations of thermal criteria (air velocity, clo, metabolic, etc.) can lead to similar PMV value and the PMV equation is useful to predict productivity loss that is due to the rate of change in thermal conditions. The study also highlights the issues that remain to be resolved in future research.

05101223 Augmentation of the performance of solar regenerator of open absorption cooling system Kabeel, A. E. Renewable Energy, 2005, 30, (3), 327-338. In open cycle liquid desiccant air conditioning, the solar collector regenerator is one of the effective ways of regenerating liquid solution. In this work, the regeneration of liquid solution using cross flow of air stream with flowing film of desiccant on the surface of a solar collector/ regenerator has been investigated. To evaluate the effect of cross flow of air stream on the performance of the unit, two identical units are constructed and tested in the same conditions of operation. One of the two units was augmented with air blower. The absorber plate is a black cloth layer. The forced air stream, which flows across the absorber removes the moisture from the liquid solution. The regeneration in the other collector/regenerator unit is free. The results show enhancement of regeneration efficiency for the forced cross flow compared with the