Thermal performance of a compact design heat pipe solar collector with latent heat storage in charging/discharging modes

This paper reports an experimental investigation on a design of solar water heater system (SWH) employing evacuated tube heat pipe solar collectors (HPSCs) and a latent heat storage (LHS) tank. In this design, solar energy incident on the HPSC is collected and stored in the LHS tank via a heat pipe with fins attached to the condenser ends inside the LHS tank. The stored heat is then transferred to the supply water via a set of finned pipes located inside the LHS tank. In this paper, the design, the working principles and the experimental thermal operations of the charging only and discharging only modes are presented. The effects of weather conditions in a tropical region and supply water flowrates and hot water draw off time are also reported. The thermal efficiency of the system in sunny days is in the range of the 38%-42%, while in cloudy-rainy days this efficiency drop to the range of 34%-36%, which indicates a range of about 8% fluctuation in different conditions. It was illustrated that the flowrate has direct proportion on the overall efficiency of the system in the tested range. Advantages of the heat pipe and phase change material together cover their disadvantages like overheating of the heat pipe and low thermal conductivity of the phase change material. By this design for energy storage tank, the thermal stratification effect is completely removed. This system could be a stand-alone system for night hot-water demands or part of a SWH configuration. (C) 2017 Elsevier Ltd. All rights reserved.