Abstract
Evacuated tube solar water heater systems are widely used in China due to their high thermal efficiency, simple construction requirements, and low manufacturing costs. CPC evacuated tube solar water heaters with a geometrical concentration ratio C of less than one are rare. A comparison of the experimental rig of evacuated tube solar water heater systems with and without a mini-CPC reflector was set up, with a series of experiments done in Hefei (31°53'N, 117°15'E), China. The first and second laws of thermodynamics were used to analyze and contrast their thermal performance. The water in the tank was heated from 26.9 to 55, 65, 75, 85, and 95 °C. Two types of solar water heater systems were used, and the data gathered for two days were compared. The results show that when attaining low temperature water, the evacuated tube solar water heater system without a mini-CPC reflector has higher thermal and exergy efficiencies than the system with a mini-CPC reflector, including the average and immediate values. On the other hand, when attaining high temperature water, the system with a mini-CPC reflector has higher thermal and exergy efficiencies than the other one. The comparison presents the advantages of evacuated tube solar water heater systems with and without a mini-CPC reflector, which can be offered as a reference when choosing which solar water system to use for actual applications.
Highlights
IntroductionEvacuated tube solar water heater systems are widely used in China
Greek letters absorptivity α emissivity ε η efficiency sun sys w_tank reflector the sun system water in the tank the start the end Evacuated tube solar water heater systems are widely used in China
Kim et al [6] examined four different shapes of absorber tube such as finned tubes, a U tube welded inside a circular fin, a U tube welded on a copper plate, and a U tube welded inside a rectangular duct using a numerical method, and they found the best absorber tube shape for a solar collector
Summary
Evacuated tube solar water heater systems are widely used in China Their advantages include their high thermal efficiency, simple construction requirements, and low manufacturing costs. Evacuated tube solar water heater systems with and without CPC reflectors have their respective advantages and application scopes. The former generally provides hot water or floor heating energy, whereas the latter provides higher temperature for other applications, such as industrial washing. When the temperature requirement in applications is low, the evacuated tube solar water heater system without a mini-CPC reflector offers some advantages. On the other hand, when the temperature requirement in applications is high, the evacuated tube solar water heater system with a mini-CPC reflector is more suitable
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