Enhancement of Heat Transfer in PCM by Cellular Zn-Al Structure

Development of open cellular metal foam technology based on investment casting applying the polyurethane pattern is discussed. Technological process comprises preparing of the ceramic mold applying PUR foam as the pattern, firing of the mold, pouring of the liquid Zn-Al alloy into the mold and washing out of the ceramic material from cellular casting. Critical parameters such as the temperature of mold and poured metal, design of gating system affected by metalostatic pressure allowed to produce castings with cellular structure characterized by the open porosity. Metal cellular foams with the open porosity embedded in phase change material (PCM) enhance heat transfer and reduce time operations in energy storage systems. Charging and discharging were performed at the laboratory accumulator by heating and cooling with flowing water characterized by the temperatures of 97-100ºC. Temperature measurements were collected from 7 different thermocouples located in the accumulator. In relation to the tests with pure paraffin, embedding of the metal Zn-Al cellular foam in paraffin significantly decreases temperature gradients and melting time of paraffin applied as PCM characterized by the low thermal conductivity. Similarly, reduction of discharging time by this method improves the efficiency of thermal energy storage system applied in solar power plants or for the systems of energy efficient buildings