SUMMARY

Latent heat thermal energy storage (TES) is becoming an increasingly popular approach for effective energy conservation. Significant energy can be stored in relatively small volumes of material by taking advantage of the high latent heat of solid-liquid phase change materials (PCMs). Storing large amounts of energy in this space-effective manner is very attractive for data center applications where considerable resources are expended to cool electronics. Because cold water is often used as the working fluid in a series of processes to cool servers within a data center, it is desirable to formulate a cost-effective way to chill the water.

Typically, a refrigeration cycle is employed for this water-chilling process, but electrical costs necessary to chill the water in this manner are undesirably high during peak hours of electrical usage when electricity is more expensive. Therefore, rather than using a costly refrigeration cycle during peak hours, a TES unit can be used to chill the water during this time of high electrical prices. This would allow the electrical load of the refrigeration cycle to shift to off-peak hours (such as nighttime) for charging the TES unit.

This thesis addresses the numerical and experimental investigation of a TES unit with water acting as the heat transfer fluid (HTF) in crossflow over a bank of PCM-filled tubes. The numerical simulations employ a fully-implicit one-dimensional control volume formulation that utilizes the enthalpy method for phase change. The phase change process for the tube bank is coupled with the conservation of energy to determine the bulk HTF temperature exiting each column of tubes and ultimately the tube bank. Experimentation has been performed for model validation, and the transient numerical simulation results are compared with the experimental findings.