逆流式蒸发冷凝型烟气全热换热器的数值模拟研究

Numerical simulation of countercurrent evaporative flue gas total heat exchanger

为解决空气-烟气全热换热过程中,以喷淋水作为中间流体,因3股流体热容不匹配,导致系统换热效率受限的问题,提出了适用于烟气余热回收的逆流式蒸发冷凝型全热换热器,用流量极低的水膜代替中间流体,解除其对换热效率的限制。通过建立换热器的二维模型,对其热湿传递过程进行数值模拟计算,研究了气体流动方式、烟气入口流速、喷淋水质量流量、换热板长宽比及通道间距对全热换热器性能的影响。结果表明:当气体流动方式为烟气上进下出、空气下进上出,烟气入口流速为2.5~3.5 m/s,换热板长宽比在3—5,通道间距为5~7 mm时,全热换热器换热性能较好;在满足空气保持饱和状态条件下,喷淋水质量流量越小,全热换热器性能越好。

To address the problem that the heat transfer efficiency of the system is limited due to the mismatch of the heat capacity of the three fluids in the air-flue gas total heat transfer process,a counter-flow evaporative condensing total heat exchanger suitable for flue gas waste heat recovery is proposed.A water film with a very low flow rate is used instead of the intermediate fluid to remove its limitation on the heat transfer efficiency.A two-dimensional model of the heat exchanger is established and its heat and moisture transfer process is numerically simulated.The effects of Gas flow patterns,flue gas inlet flow rate,spray water mass flow rate,heat exchanger plate aspect ratio and channel spacing on the performance of the total heat exchanger are investigated.The results show that when the flow of gas is from above into below and air from below into above the flue gas,inlet flow rate is 2.5~3.5 m/s,the heat exchanger plate aspect ratio is 3~5 and the channel spacing is 5~7 mm,the heat transfer performance of the full heat exchanger is better.Under the condition that the air remains saturated,the smaller the spray water mass flow rate is,the better the performance of the full heat exchanger is.