A New Model to Investigate Effect of Heat Conduction Between Tubes on Overall Performance of a Coil Absorber for Flat-Plate Solar Collectors

Solar heaters are a sustainable solution to lower operating heating costs for diverse applications. Improving the design of these devices promotes the adoption of this technology to reduce the environmental impact of traditional gas water heaters. The present paper studies heat transfer along the plate-fins of serpentine-type flat-plate solar collectors. The focus of this investigation is the analysis of tube-to-tube thermal conduction through the absorbent plate and its effect on the heat gain of the circulating fluid. The model used here does not consider the adiabatic boundary condition in the plate mid-distance between tubes but applies the prescribed temperatures of the tubes as a boundary condition for the plate-fins. This type of boundary condition allows for heat conduction between rows of tubes. The analysis demonstrates that tube-to-tube heat conduction along the absorber plate has a detrimental effect on the heat gain of the circulating fluid. This effect is responsible for a decrease of up to 10% of the circulating fluid heat gain. This investigation defines the set of parameters that affect the performance of plate solar heaters because of tube-to-tube thermal conduction along the plates, and it helps to choose operation and designs parameters, leading to better design of these devices.