The purpose of current study is investigation the use of ultrasonic energy and phase change materials (PCM) in cooling a hot plate. Hence an experimental setup is prepared and a PCM is placed between two aluminum plates in a way the upper plate is hot and the lower plate is cold. Water or CuO nanofluid flows in a container equipped with five 1.7 MHz piezoelectrics. The lower aluminum plate is cooled by cold vapor generated by an ultrasonic device, which increases the temperature gradient in the lower and upper layers of the PCM and simultaneously, the heat of the upper hot plate absorbs by PCM. To increase the thermal conductivity of PCM, different layers of metal matrix sheets (MMS) placed inside it. The effects of PCM thickness, weight fractions (%wt) of CuO nanoparticles (NPs) and number of MMS on the temperature of hot and cold plates is evaluated. The RSM method is used to design the experiments and obtain the optimal conditions of the proposed system. Results show that the use of pure PCM can decrease the hot plate temperature from 62.5 ◦C to 58.64 ◦C. Propagation of ultrasonic waves to the bottom plate intensified decrease in the hot plate temperature. In addition, increasing the weight fraction of NPs as well as the number of MMS have positive effects on reducing the hot plate temperature. Increasing the thickness of PCM from 1 to 2.5 cm reduces the temperature of the hot plate and has the opposite effect for its thickness from 2.5 to 3 cm. Finally, it can be found that under optimal conditions (4 MMS and 3.5 % NPs) the hot plate temperature could be decreased from 62.5 ◦C to 43.3 ◦C.
