Experimental Study of the Effect of Straight-Section Length on Serpentine Tube Heat Exchanger with Sharp Turns

Compact-type heat exchangers are widely used in industry because of their small dimensions and lightweight with high heat transfer rates. This study aims to examine the effect of straight-section length on a serpentine tube heat exchanger with sharp turns. The heat exchanger used is made of galvanized pipe with an inner diameter of 20 mm and an outer diameter of 22 mm. The total length of the heat exchanger is 6 m with variations in the length of the straight section, namely 60, 45, 30, and 15 cm. Water with a temperature of 80 ℃ is flowed into the heat exchanger using a pump that is integrated with the heater. The flow of water entering the heat exchanger is 0.4 L/s. Water at room temperature is used as a cooling medium for the heat exchanger. The inlet and outlet temperatures of the heat exchanger were measured using a thermocouple, and the cooling water temperature was also measured using a thermocouple. The results showed that a heat exchanger with a straight-section length of 30 cm had the highest heat transfer rate and heat transfer coefficient compared to other heat exchangers. The rate of heat transfer in a heat exchanger with a straight-section length of 30 cm is 15.9% higher than that of a heat exchanger with a straight-section length of 15 cm, 56% higher than the heat exchanger with a straight-section length of 45 cm, and 78.5% higher than the heat exchanger with a straight-section length of 60 cm. The highest convection heat transfer coefficient is obtained in a heat exchanger with a straight-section length of 30 cm, and the average heat transfer coefficient is 1168.5 kW/m2·K.