Numerical study on the improved design of the dimpled plate of gas-to-gas plate heat exchanger

Plate heat exchangers are often required for high performance during secondary energy utilization in recent years. The efficiency of energy utilization can greatly contribute to sustainable development, in response to the increasingly severe energy crises and environmental challenges. In this study, the numerical analysis was conducted on the flow and heat transfer in a gas-to-gas plate heat exchanger. The dimensions of the heat exchange plate were 1 530 mm in length and 750 mm in width, with a spacing of 12 mm between the plates. The cold and hot fluids were exchanged in the form of cross flow. The dimpled plate of the heat exchanger shared two dimpled heights of 6.0 and 3.5 mm. The structural parameters of the dimpled plate were then optimized for the high efficiency of heat exchange. Among them, the 6.0 mm concave pits and convex cells were the supporting contacts of the cold and hot fluid channels, respectively. Simulation analysis was conducted to take the high-temperature flue gas and air as the media of heat exchange. The better performance of heat transfer was achieved in the 6.0 mm concave pits and convex cells, compared with the 3.5 mm ones. Therefore, all 3.5 mm dimples were replaced with 6.0 mm dimples in the plates of heat exchange. Furthermore, the number of dimples of 6.0 mm increased from the original 42 to 189. The longitudinal, herring bone, and transverse arrangement were also optimized on the support contact of the hot fluid channel. Some parameters were calculated under different flow rates of flue gas, including the Nussel number, the flow resistance of the channel, the Performance Evaluation Criterion (PEC) of heat transfer performance, and the pressure difference between the two sides of the plate. The results indicate that better performance was achieved in the longitudinal arrangement of the improved dimpled plate in the heat exchanger under the design condition, compared with the original plate structure. Specifically, the PEC of heat transfer was 1.25, the pressure dropped from 277.02 Pa to 308.31 Pa, the increase rate was 11%, the Nu increased from 11.48 to 15.21, and the performance of heat transfer increased by 32%. The longitudinal arrangement shared the smallest values of the maximum pressure, compared with the rest heat exchangers. The best scheme was then obtained for the improved design. The key factors were also optimized after simulation, such as the heat transfer, flow, and pressure. The dimpled arrangement has significantly improved the performance of the plate heat exchanger. The practical significance and application were provided for the dimpled plate of the heat exchanger.