Laminar flow heat transfer enhancement in multy-start spirally corrugated tubes

Abstract

Heat transfer plays an important role in many aspects of human life, especially the forced convection type. Hence, it has become very important to invest resources and efforts in this vital field to make some difference. Recently, the trend of using compact heat transport devices is of great interest to obtain an efficient, low cost and small size product which requires less production time with fewer efforts. Employing of artificial roughness, such as corrugation, for heat transfer enhancement in heat exchanger and other industrial thermal devices have shown promising results, with good performance reliability at lower cost. Therefore, the current study aimed to investigate experimentally and numerically the heat transfer enhancement and pressure drop increase in tubes with a superior type of corrugation i.e. the spiral corrugation. The flow of ionised water as working fluid in tubes at low Reynolds number was constructed to investigate the laminar flow regime of 100= Re=1300. Five spirally corrugated tubes and one smooth tube under constant wall heat flux boundary condition with various thermo-physical properties was investigated through experimental test and computational fluid dynamics simulation. Different corrugation parameters, such as corrugation height to diameter and corrugation pitch to diameter ratios were studied in different corrugated tube sizes. The results showed that the severity index, which combines the effect of both corrugation height and pitch, has great effects on heat transfer rate, friction factor, and thermal performance of the flow inside spirally corrugated tubes. The heat transfer enhancement was in the range of 1.3-2 compared to a smooth tube, accompanied with an increase in friction factor in the range 1.1-1.9. The thermal performance range was found to be improved by 1.2-2.08 times. The heat transfer and friction factor correlation are proposed.