Numerical study on heat transfer characteristics of helically coiled grooved elliptical tube heat exchanger

Changing the shape of the heat exchanger tube is an effective method to improve the heat transfer performance of the heat exchanger. However, most of the new heat exchange tubes have complex structures and are difficult to manufacture and apply in engineering. In this paper, a novel type of helically coiled grooved elliptical tube heat exchanger (HCGETHE) which is easy to manufacture is proposed. Using methane as the working fluid, the effects of the dimensionless groove diameter (D_g = 0.222, 0.333, 0.444, 0.556, 0.667), the dimensionless groove height (H_g = 0.6, 0.8, 1.0, 1.2) and the ratio of major axis to minor axis (a/b = 1.440, 1.596, 1.778) on the flow and heat transfer characteristics of the shell side are investigated by numerical simulation in the Reynolds number (Re) range of 10000 ∼ 50000 under the condition of constant wall temperature (t_w = 300 K). The results show that when the working fluid flows through the groove of the grooved elliptical tube, backflow occurs and longitudinal vortices are formed in the groove, which improve heat transfer. As the dimensionless groove diameter increases, Nu decreases and f increases. The dimensionless groove height has little effect on Nu, but a significant effect on f. Both Nu and f decrease with the increase of the ratio of major axis to minor axis. Compared with the helically coiled circular tube heat exchanger (HCCTHE), the PEC of the HCGETHE can be increased by up to 59.53 %. The excellent thermal hydraulic performance proves that it has a good application prospect.