A simulation-based parametric study for determining the relation between geometric parameters of a vertical helical coil with external heat transfer coefficient

Abstract

Globally there is an increase in demand for sustainable energy as compared to fossil fuels due to lesser carbon emissions. Moreover, an increase in the adoption of clean energy in underdeveloped countries is observed and sunlight-based energy technologies turned out to be emerging trends in developing countries. A solar collector is a widely used technology that typically uses helical coil-based heat exchangers to transport heat energy from the collector to the storage tank. Premises of our research is to determine the effects of different geometric parameter on heat transfer from the coil to the water inside the tank, and for this purpose, a validated CFD-based model is used. Geometric alternations were made to the validated model and 30 minutes flow time simulations were carried out for each model. It was discovered that an increase in diameter of the pipe, pitch & height of the coil results in a decrease in external heat transfer coefficient (HTC), and the inverse was studied for the length of the pipe. Although, the curvature ratio of the coil in comparison with HTC did not portray any specific trend. Lastly, the vertical gap between the coil and upper boundary of the tank, and the lateral gap between the coil and side wall of the tank turned out to be essential parameters. Both displayed increase in HTC with the increase in distance.