Thermal performance and thermo-economics analysis of evacuated glass tube solar water heater with closed-loop pulsating heat pipe

Abstract

This research aims to design an optimal closed-loop pulsating heat pipe (CLPHP), which is applied as a heat transfer device to replace the thermosyphon in a commercial evacuated tube solar water heater system (ETSWH). It is evaluated by high thermal performance and maximum net saving as described by the Net Saving Method and economic analysis. The CLPHP samples were designed by varying the parameters such as 1.50 and 1.78 mm inner diameter, 1.00, 1.25 and 1.50 m evaporator length with 1, 2 and 4 sets of the CLPHP (20 turns per set). The adiabatic and condenser sections were 0.05 and 0.3 m in length, respectively. An ETSWH with various samples of CLPHP was tested using a solar simulator (Indoor) that followed the EN 12975-2 standard. The components of the optimal system consisted of 10 evacuated tubes. The water capacity was 100 L. The experimental results indicated that the optimal CLPHP consisted of 1.50 mm inner diameter, 1.25 m evaporator length and 4 sets. The overall heat rate of water obtained was 518 W, with a net saving of 901.4 USD over 10 years and an investment of 482.4 USD with a simple payback period of 3.3 years.