Experimental and Numerical Investigation of the Thermal Performance of Spiral Type Solar Collector
Abstract
A spiral solar collector can be described as a particular type of solar collector that includes a pipe with many turns fixed inside a solar collector box. The thermal efficiency of a spiral-type solar collector is simulated numerically to predict the temperature distribution and thermal efficiency using ANSYS-FLUENT commercial software. The transient 3D energy equation is solved assuming that the working fluid is water and the flow is steady-state, incompressible, and turbulent using the (K-ε) model. The effects of changing the water flow rate, the direction of flow, and the pipe diameter on the distribution of the temperature and thermal efficiency are studied. Excellent agreement is obtained when comparing predicted results with measurements obtained from the experimental test using a spiral-type solar collector model made of a (15-turn) copper pipe of (23 m) in length and (7.75 mm) inside diameter. This spiral pipe is fixed on a flat copper plate of (65*65 cm2) fitted inside a wood box of (77*77 cm2) covered with a single layer of glass and insulated from the other side with fiberglass. A (17.8 lit.) water storage tank made of cork is connected to a D.C pump. This pump is supplied with electric power from a (100 W) photovoltaic cell. It is used to circulate the water with a flow of (0.0625 lit/sec and 0.03125 lit/sec) through the system. It was found that the optimum thermal efficiency is (82.5 %) when the water flow rate is (0.0625 lit/sec) flowing in a direction such that the water inlet port is located at the center of the spiral pipe. An enhancement of (34.6 %) increase in thermal efficiency is obtained compared with the worst case when the flow rate is the same value but the circumference entrance port.
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