A Parametric Study on the Efficiency of a Solar Evacuated Tube Collector Using Phase Change Materials : A Transient Simulation

Evacuated solar collectors are systems that provide a considerable quantity of heat. However, this system is unable to provide energy in the absence of sunlight. Thus, this study attempts to numerically study a Solar Evacuated Tube Collector (ETC) performance using phase change materials (PCM). In the present investigation, the effect of variation of different variables, consisting of enthalpy, melting point, and conductivity of the PCM material on the system's performance, is evaluated. Also, the effects of some other factors, such as MWCNT nanoparticles dispersion in the base fluid and nanofluid mass flow rate on the performance of the ETC are studied. According to the results of the simulations, a reduction in PCM melting point from 50 ºC to 35 ºC, can elevate the efficiency of the ETC-PCM device. PCM with a high melting point remains solid during the day. Thus, its effect on the output of the system cannot be revealed. Moreover, it is found that the system by using PCM with the latent heat of 160 kJ/kg has the best performance among the studied cases. Besides, it is illustrated that rising the mass flow rate of working fluid and mass fraction of nanoparticles can enhance the system's proficiency