Analysis and Design of Compact Heat Exchanger for a Thermo-voltaic Power Generation System
摘要
Middle and low temperature geothermal power generation by thermoelectric materials receives increasingly attention, while the key difficulty involved is how to increase the thermoelectric conversion efficiency. This paper presents a conceptual design of heat exchanger on the basis of a Self-Similarity microchannel Heat Sink (SSHS) which can reduce the volume and weight of the system to a great extent and increase the thermo-electric conversion efficiency. With a heat exchanger of the hot side as an example, its heat transfer and flow resistance characteristics were numerically evaluated and compared with two traditional heat exchange structures. The calculation results indicate that the current design of SSHS has a better performance and uniformity in heat transfer. Under conditions of flow rates of 0.0103～0.0186 kg/s, heat flux of 2 W/cm<sup>2</sup> and entrance water temperature of 100 ℃, its heat transfer ability is over twice of that of a conventional heat exchanger, and average temperature of the heat release surface is raised by 5～10 K, and uniformity in temperature distribution is increased over 50%. As a consequence, an improved thermoelectric conversion efficiency is obtained, although a larger flow resistance is hard to avoid. For the current design the total pressure drop is no more than 450 Pa, it is still very suitable for a direct thermo-electric conversion system.