Parametric studies on thermally strati®ed chilled water storage systems

An analysis of the strati®cation decay in thermally strati®ed vertical cylindrical cool storage systems is presented using a one dimensional conjugate heat conduction model. The degree of thermal strati®cation depends upon the length to diameter ratio, wall thickness to length ratio, the thermo-physical properties of the material of the storage tank, the type and thickness of the insulation and the design of the admission system for both cold and warm water. A parametric study of the strati®ed chilled water storage tanks in charging, discharging and stagnation modes of operation is made. The thermoclines degrade due to the heat transfer from the ambient, thermal di€usion in the storage tank, axial wall conduction and mixing due to admission of the ̄uid in the storage tank during charging and discharging. The degree of thermal strati®cation in storage tanks is expressed in terms of either heat capacity (thermal capacitance ratio) or modi®ed Biot Number. A mixing parameter accounts for the e€ect of mixing on thermal strati®cation in both charge and discharge cycles. # 1998 Elsevier Science Ltd. All rights reserved.