A CFD-based study for understanding the relationship between geometric parameters of vertical helical coil with inner heat transfer coefficient

Worldwide there is an increase in demand for clean and renewable energy due to exacerbating climate conditions globally and increasing energy crisis in developing countries. To solve this problem Pakistan needs to adopt renewable energy technologies, while solar collectors are one of the most prominent solar technology. Collectors are normally attached to a water storage tank by means of a helical coil-based heat exchanger. Our research is to find the factors which affect the performance of helical coil-based heat exchangers. In our research, a vertical helical coiled-based water tank is modeled and validated with the experimental setup. The numerical model showed results with good accuracy having a percentage error of 4.93%, for the temperature of heat transfer fluid (HTF), at the outlet of the coil. Furthermore, by considering the validated model as a baseline model, a variety of geometric models were created by changing different geometric parameters of the coil and simulated further on varying flow rates to study the impact of different parameters on the inner heat transfer coefficient (HTC) of the helical coil. It was deduced, that the HTC decreases with the increase in diameter of the pipe and rises with the increase in length of the pipe. However, the pitch of the coil did not portray any significant role to predict the trend of the heat transfer coefficient. Lastly, the heat transfer coefficient also showed an increasing trend with the increase in curvature ratio of the coil, as it is also a significant parameter in determining the hydrodynamic nature of the flow.