A study of energy performance of evacuated-tube solar water-heating collectors

Abstract

The study is to evaluate the performance of two types of evacuated tube thermosyphon solar collector as applied in thermosyphon solar water heating systems. The market of these two collector types, namely the single-phase natural circulation and two-phase heat pipe design, is growing in China, including Hong Kong. In this study, physical models for the two types of evacuated tube thermosyphon solar water heating system are developed, demonstrated to be of good quality, and with the computer simulations executed via the TRNSYS program. The evacuated tube thermosyphon solar water heating systems are found to have higher working efficiency than the flat plate thermosyphon systems when generating hot water at elevated temperature. Compared to the two-phase design, the single-phase thermosyphon system has the advantages of lower initial investment, and lower daily heat loss. It is more suitable for application in the relatively cold region as long as the water freezing problem in winter is not serious. On the other hand, the two-phase thermosyphon system is advantageous because of its higher efficiency achievable. Despite the slightly higher investment, it can be a good choice for the purpose of generating more hot water under the same weather condition. For all climate regions of China, the economic payback periods for these two types of evacuated tube thermosyphon system are found almost the same. Nevertheless, when compared with the payback period of the flat plate collector system which is applicable to the south of China region, they are relatively longer.

Date of Award	3 Oct 2011
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Tin Tai CHOW (Supervisor) & Chi Ming TAM (Co-supervisor)