Experimental Investigation of Single and Multiple Atomized Water Spray Impingement for Efficient Solar Water Heating

Abstract In this experimental work, a novel design of a closed-loop flat plate solar water heater (FPSWH) of capacity 100 l is investigated for the thermal performance improvement. The investigated design abolished the convectional tube to flat absorber plate contact and implemented the direct water to flat absorber plate contact that results in improved heat transfer and thermal performance. Therefore, atomized water spray impingement is utilized as a single spray and a multiple spray array on the hot absorber plate of area 1 m2 that suppresses the thermal contact resistance due to impingement of high velocity droplets. Moreover, water atomization increases the surface area of a single droplet and consequently increases the heat transfer to the complete volume of the water. The collected hot spray water in the storage tank at the end of the cycle, and the heating duration will be used for thermal applications. However, the effect of the number of nozzles(1≤N≤9)), total mass flowrate (0.01kg/s≤m˙≤0.083kg/s), and distance of impingement (10cm≤S≤25cm) on the thermal performance is investigated. Moreover, the effect of the collector angle (0deg≤α≤40deg) is also studied as a part of this investigation. It is obtained that the physics of fluid flow and heat transfer largely change with the change in the value of S and α. The obtained results presented the thermal efficiency of about 90% and temperature gain of ΔT≈15.5∘C at N = 9, S = 25 cm, m˙=0.083kg/s, and α=40deg for 2 h of indoor heating at ≈1000W/m2. Under real outdoor conditions, for the present design of solar water heater (SWH), ΔT=25∘C and final water temperature, Tf=50∘C, are obtained at the optimum values of geometrical and flow parameters.