Performance Improvement of the Solar Heat Pump Using Carbon Nanotubes in the Refrigerant and its Condenser Structure

Improving the performance of solar heat pumps has always been of interest to researchers. The purpose of this study has been to find the optimal state of carbon nanotube (CNT) concentration in the refrigerants and condenser copper tubes as well as the total tube length and the diameter of the condenser helical coil, in order to maximize the exergy and heat transfer. The investigation has been carried out by the numerical method using finite volume, unsteady and laminar flow. The genetic algorithm has been used to obtain the optimum choice for the condenser in two states of constant and variable diameter. Three concentrations of 0, 0.5 and 1 percent for the carbon nanotubes in the refrigerant, three concentrations of 0, 1 and 3 percent for the carbon nanotubes in the copper tube, three different values for the condenser diameter in each of the two states of constant and variable diameter, and three different condenser tube lengths have been investigated. The results show that the use of CNT in the refrigerant, always increases the Nusselt number and the exergy while, the use of CNT in the wall structure of the condenser copper tube reduces them. The results also show that the use of carbon nanotubes in the refrigerant increases the Nusselt number by 16% to 21%, and the exergy by 9% to 13%. However, using carbon nanotubes in the condenser copper tube wall reduces the Nusselt number and the exergy up to 9.5% and 18% respectively.