Heat transfer coefficients during laminar flow of microencapsulated PCM fluid

This paper presents an experimental study of heat transfer during laminar flow of a microencapsulated phase change material slurry (MPCMS). Working fluids using phase change material (PCM), are an alternative to currently used fluids such as water or glycols. Their greatest advantage is the enhancement of heat transfer and thermal energy storage capabilities. MPCMS include a base fluid, a shell that forms a microcapsule and a PCM material. We present the results of our experimental research on heat transfer using a test setup that includes a pump, a Coriolis flow meter, and a resistive exchanger as the measuring section. Our laboratory power supply enabled precise control of the heat flux supplied to the circular tube exchanger. This allowed us to observe thermal effects and phase transitions of the PCM in the test fluid. For comparison, we used distilled water as a well-known fluid to verify the accuracy of our measurements. The suspension we analyzed was based on the commercially available MicroCaps PCM31S-50 material, which uses paraffin as PCM with a mass content of 36-40% in concentrate and a melting range of 28-31 degrees C. The experiments were conducted for laminar flow with Reynolds number in the range of 1000-2000. Using thermocouples along the exchanger walls and at the inlet and outlet, we determined the Nusselt number and heat transfer coefficient for temperatures before, during, and after phase change. Our results show heat transfer coefficients ranging from 160 to 240 W/m(2)K.