Use of Heat Pipes in PCM Latent Heat Storage

The purpose of this study is to explore and document the heat transfer into a phase change thermal energy storage material using heat pipes. A phase change thermal energy storage material is a material that takes advantage of the energy accompanying a phase change in that material to store more thermal energy. Paraffin wax was chosen as the phase change fluid because its thermal properties are well documented, it is safe to use, has a desirable melting temperature of approximately 58^oC, and is readily available from numerous sources. A heat pipe is a device that utilizes both thermal conduction along the pipe as well as phase transfer of a working fluid inside the pipe to increase its heat flux compared to a traditional copper pipe. The test assembly consisted of two concentric cylinders, which was used in this study in order to simplify the problem to two-dimensional heat transfer. In the inner cylinder, water was heated up using a cartridge heater to a steady-state at 65^oC. Protruding out of the inner cylinder into the annulus containing the wax, there were two rows of four heat pipes placed at 90^o intervals. The outer cylinder annulus was filled with paraffin wax.  Temperatures  in the wax  were measured at different distances from the center using thermocouples.  This study has two phases, a heat loss phase (phase 1) and a testing phase (phase 2). In phase 1, the amount of heat lost in from the device was measured. This was done by allowing the system to reach a steady state and recording the difference in temperature at various radii. The second phase involved testing the effectiveness of the heat pipe in transferring heat into the on the paraffin wax.  Temperature measurements here were used to test the validity of a computational model.