ANALYSIS OF THE PERFORMANCES OF HEAT-EXCHANGERS USED IN HOT-WATER STORES

The thermal response of a hot-water store and the thermal discharge ch aracteristics from heat exchanger coils placed inside have been experi mentally investigated. The analysis of the experimental results shows that it is possible to describe the thermal behaviour of these systems by the use of a convenient set of dimensionless parameters. Two diffe rent geometric configurations of the heat-exchanger coils were investi gated, namely the classic cylindrical coil and the flat spiral coil, t his last one presenting a greater heat transfer efficiency. The hypoth esis of a lumped heat capacity for the thermal evolution of the water store enables the construction of a simplified theoretical model. The solution of which, obtained by a numerical method, predicts with reaso nable accuracy the time evolutions of both the average temperature of the water tank and of the inlet-outlet temperature difference of the c irculating water. Copyright (C) 1996 Elsevier Science Ltd