A High Efficiency Electric Heater Based on Dual-helical Tube and Screw-tape for Instant Water Heating

Abstract Waste of natural water resources is a serious worldwide challenge, especially in many water shortage countries. There is an urgent and widely known problem that cold-water needs to be released from the faucet before people need warm or hot water. Therefore, there is urgent need for a feasible and effective solution to tackle this problem. In this paper, we proposed a novel instant water-heater based on a dual-helical tube and screw-tape for application in faucets. The proposed water-heater includes four main parts: a control valve module, a cavity structure module, a heating module, and an electronic control module. The heating module is comprised of a dual-helical tube and screw-tape. The dual-helical tube increases the heating area, resulting in uniform heating. The screw-tape possesses a profitable characteristic in that it can make fluid tangential flow and lower the cross-sectional area of the fluid. Based on this advantage, the core region and wall region fluids are mixed, which significantly enhances the heat-transfer rate. The effects of a dual-helical tube and screw-tape with different helical pitch are examined. The experimental results are compared with those obtained using a helical tube/dual-helical tube alone. A 59.6% efficiency improvement is achieved comparing the dual-helical tube and screw-tape with the single helical tube, which suggests the proposed instant electric water-heater is highly efficient and energy saving.