4023 -- Parametric Study of a Silica Gel-Water Adsorption Refrigeration Cycle - The Influence of Thermal Capacitance and Heat Exchanger UA-Values on Cooling Capacity, Power Density, and COP PDF

The influence of heat exchanger UA-values (adsorber/desorber, evaporator, and condenser) is investigated for an adsorption chiller, with consideration given to the thermal capacitance of the adsorber/desorber by means of a lumped-parameter cycle simulation model developed by the authors and co-workers for the single-stage silica gel-water adsorption chiller. The closed-cycle-type chiller, for use in air conditioning, is driven by low-grade waste heat (85degC [185deg]) and cooled by water at 31degC [88degF]) and operates on relatively short cycle times (420 seconds adsorption/desorption; 30 second adsorber/desorber sensible cooling and heating). The results showed cycle performance to be considerably affected by the thermal capacitance and UA-value of the adsorber/desorber, which is attributed to the severe sensible cooling/heating requirements resulting from batched cycle operation. The model is also sensitive to the evaporator UA-value - but to a lesser extent. The condenser UA-value is the least sensitive parameter due to the working pair adsorption behaviour in the temperature range defined for desorption and condensation.

KEYWORDS: year 1997, Adsorption, chillers, refrigeration, absorption refrigeration, desiccants, heat exchangers, calculating, air conditioning, heat recovery, performance, heat loss, heat flow, heat transfer coefficient