Numerical investigation of thermal and hydraulic performance of tankless water heater tubes with various aspect ratio

A two-dimensional numerical model of tankless gas water heater (TGWH) is created to investigate the flow rate performance. The thermal and hydraulic performance for laminar flow over the water tube with different aspect ratios are studied numerically. The investigated variables are inlet hot air velocity and flat-tube aspect ratio. The Heat transfer coefficient from the present study is calculated and presented graphically. The results show that for input air velocities less than 1.5 m/s, the heat exchanger with the lower flat-tube aspect ratio provided a higher heat transfer coefficient; as the inlet air velocity increased, the heat exchanger with the higher flat-tube aspect ratio produced a higher heat transfer coefficient.