电场对微细通道内 R141b 制冷剂流动沸腾压降的影响.

Microchannel heat exchanger is highly efficient in heat exchange due to its microscopic structure and large heat exchange surface area ratio. Compared with conventional heat exchanger, it not only improves heat exchange efficiency but also saves space and reduces the weight of heat dissipation equipment. In agriculture, microchannel heat dissipation technology has been widely used in cultivation, machinery, and product drying. Microchannel increases resistance to fluid flow and could thus result in an increase in energy consumption. It could also give rise to a pressure-drop oscillation affecting operation of the system. Previous work showed that electric field has a beneficial impact on heat transfer efficiency in the microchannel heat exchanger. The purpose of this paper is to investigate how different electrodes (needle type and linear types) affect pressure drop of the boiling R141b coolant when it flows in the microchannel. The pressure in the system was kept at 140 kPa, the working inlet temperature was 32.5, the mass flow rate ranged from 277.35 ℃ to 531.75 kg/(m²·s), the heat flux density ranged from 7.50 to 21.49 kW/m², the voltage ranged from 0 to 850 V, and the microchannel was rectangular with a cross section of 2 mm×2 mm. The results showed that the electric field under both electrodes increased the frictional pressure drop in the microchannel, compared with that without electric field. The frictional pressure drop of the two-phase along per unit length increased with both voltage and heat flux. The average two-phase frictional pressure drop along per unit length under the needle and the linear electrode was increased 0.7% to 15.4% and 1.3% to 18.7%, respectively, that without electric field. When the voltage changed from 0 to 250 V, the effect of the needle electrode on the pressure drop was greater than that of the linear electrode, while when the voltage was higher than 400 V, the effect of the linear electrode on the pressure drop was more significant. We simulated the electric field distribution in a microchannel 6 mm long using COMSOL for both electrodes. The results showed that under the same voltage, the maximum of the electric field intensity in the needle electrode was higher than that in the linear electrode, but the effective range of the electric field in the linear electrode was higher than that in the needle electrode. The results presented in this paper provide an alternative to improve performance of microchannel heat exchanger and reduce its energy consumption. [ABSTRACT FROM AUTHOR]