Performance of ice storage system utilizing a combined partial and full storage strategy

A combined system is a new thermal storage strategy adopted in this study with which the two other known strategies namely, partial and full load, are compared. The results revealed that the combined system requires larger equipment size than that required by partial system to satisfy the same cooling load. Factors Fp and Ff that may be multiplied by the daily average cooling load to determine the optimum chillers size for a combined system are found. These factors are applicable for any cooling load and are based on a given chiller condensing and evaporating condition as used in this study. These factors are found to vary with the number of on-peak hours. Combined strategy required chiller size was found to decrease with decrease in on-peak period, hence the optimum chiller size for this new strategy was found to occur at zero on-peak hours, and i.e., when the combined system starts to operate as a partial strategy system.

1) Combined strategy system requires less chiller size than conventional system does. A reduction of about 28% may be achieved. 2) Partial chiller strategy requires less chiller size than combined system. 3) Combined strategy chiller size was found to decrease with decrease in on-peak period. 4) Factors Fp and Ff found in this study can be used with any other cooling load to estimate the minimum required chiller size. Nomenclature F h Q qt V factor refrigerant enthalpy kJ/kg chiller capacity kW hourly cooling load kW refrigerant volume flow rate (m3/s) Subscript av average com combined conv conventional f full storage mn minimum p partial chiller sf size of full strategy chiller sp size of partial strategy chiller Tp total chiller capacity for partial strategy total time inlet to compressor state outlet from expansion valve state Greek symbols r density (kg/m3) h volumetric efficiency