Abstract
The performance of a dual-function solar collector (DFSC) that can work as either water heater or air heater depending on seasonal requirement is investigated via both experimental and numerical approaches in this paper. The numerical results are well consistent with the experimental results. Daily efficiency of the thermosiphon system with DFSC is more than 55% in water heating mode and the instantaneous air heating efficiency of the collector reaches 60%. The effects of inner parameters on the thermal efficiency of the collector are analyzed by numerical simulations of the operation of DFSC in two working modes. It is found that the depths of the two air channels in DFSC have an optimal range suitable for both working modes. The thickness of back insulation should be no less than 0.06 m to prevent heat loss via backboard, and the diameter and number of copper tubes show notable effect on the efficiency of DFSC in water heating mode but slight effect in air heating mode.
Highlights
China is by far the largest market for solar water heaters
In cold days in these regions, energy consumption is prominent for space heating in buildings, an alternative solar collector named as dual-function solar collector (DFSC) has been proposed, which operates as air heater for space heating in cold winter and as water heater in other warm seasons [4,5,6]
The experimental results show that the daily efficiency of the thermosiphon system of DFSC in water heating is more than 55%, and the instantaneous efficiency of DFSC in air heating can reach 60.2%
Summary
China is by far the largest market for solar water heaters. Due to its advantage in adapting building envelope, flat-plate solar water heater is utilized widely in southern China to make domestic hot water. Influence of building integration on the performance of different solar collectors has been widely investigated [1, 2]. The gap between absorber plate and glazing should be of an appropriate value to curb heat losses via the top of solar water heater [12, 13]. These structural adjustments for solar air heater and water heater, are different and even contradictory and impossible to be directly applied to DFSC. Effect of different inner parameters on the efficiency of DFSC in two heating modes is analyzed based on numerical results
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