Abstract: In response to the current problem of high closed water temperature and poor user experience in instantaneous heating aluminum casting heating elements, a CFD model was established to study different performance parameters such as heating speed, closed water temperature rise, flow rate inside the bypass tube, and heating temperature field of the heating element under 2 mm, 3 mm, and 4 mm bypass tube diameters and 1 and 3 bend tube structures. The results of the study show that adding a bypass premix device to the heating element can effectively reduce the temperature rise of the heating element and improve the user's bathing experience. However, adding a bypass premix device will increase the surface temperature of the heating element and increase the heating speed of the heating element. In addition, it was found that reducing the diameter of the bypass pipe has a more significant impact on the flow rate changes inside the pipe than changing the structure of the bypass bend.

Key words: Instantaneous electric water heater, Cast aluminum heating element, Bypass premixed structure, Heating element performance