Heat Transfer Analysis of Stratified Chilled Water Storage Tank for District Cooling Systems

The cooling demand is rising exponentially across the globe due to adverse environmental conditions, Thus, needs more energy-efficient solutions for commercial and residential applications.District Cooling System (DCS) is a cost-effective method for providing comfort to consumers from a central plant through a distribution network improving the efficiency for reliable solutions in densely populated areas.The research work included designing, developing, and fabricating a DCS system for a 0.5 TR refrigeration system for learning thermal stratification in terms of thermocline thickness, figure of merit, and equivalent lost tank height for different volume flow rates of water.The system can perform experiments for charging and discharging operations to study district cooling systems.The system consists of three sections such as chiller, heating, and stratification.The stratification tank has centrally located ten temperature sensors to measure the temperature drop between the cold and warm water to measure the mixing intensity.It is found that the thermocline thickness is 0.175 m, the figure of merit for half-cycle is 0.9, and the equivalent lost tank height is 0.07 for a water flow rate of 100 LPH.Thus, with the DCS system, energy is saved over the conventional cooling methods with less impact on the atmosphere in terms of CO2 and GWP for sustainable growth.The CFD simulations of the thermal stratification phenomenon are performed with ANSYS to predict the performance during charging and discharging operations.CFD results are validated with the actual experimental observations for different flow rates.The relationship between mixing intensity and incoming flow is established to study thermal energy storage by stratification.It is found that a stratified chilled water storage system eliminates shortcomings of conventional ice bank storage systems due to higher power consumption for lower evaporating temperatures.Indian industry has now started using the concept of DCS system over other conventional methods as an energy conservation approach for residential and commercial heating, ventilation, air conditioning and refrigeration applications.