在线清洗对管壳式换热器传热性能的影响

Effect of on-line cleaning on the heat transfer performance of shell and tube heat exchanger

为提高除垢效率和管壳式换热器的传热性能,以一台燃气溴化锂吸收式制冷机组为研究对象,通过加装胶球在线清洗系统,研究了胶球在线清洗对吸收器和换热器传热性能的影响。结果表明,在无胶球线清洗工况下换热器污垢热阻随运行时间的增加而逐渐增大,直燃机组的性能系数(COP)随时间的增加而逐渐下降;在线清洗系统运行参数对投球率、发球泵运行时间及启停比对管壳式换热器污垢热阻有显著影响。当投球率为10%、20%和30%时,污垢热阻分别增加了32.8%、20.8%和5.7%;当运行时间分别为20 s、40 s和60 s时,污垢热阻分别增加了-20.8%、17.9%和10.7%;当启停比为1∶1、1∶2和1∶3时,污垢热阻分别增加了16.1%、23.0%和29.0%。综合考虑运行费用和胶球的使用寿命等因素,当在线清洗系统的投球率为20%、运行60 s间隔120 s和启停比为1∶2时,运行工况最佳。

In order to improve descaling efficiency and heat transfer performance of shell and tube heat exchanger,a gas-fired lithium bromide absorption chiller is selected as the research object.By installing rubber ball online cleaning system,the influence of rubber ball online cleaning on the heat transfer performance of absorber and heat exchanger was experimentally studied.The results show that the fouling resistance of heat exchanger increases with the increase of operation time while the performance coefficient(COP)of direct-fired unit decreases with time under the condition of no rubber ball online cleaning system.The ball rate,service time and start/stop ratio of on-line cleaning system have significant effects on fouling resistance of shell and tube heat exchanger.When the input rate is 10%,20%,and 30%,the thermal resistance of the scale increases by 32.8%,20.8%and 8.9%,respectively.When the running time is 20 s,40 s and 60 s respectively,the thermal resistance of the scale increases correspondingly by-20.8%,17.9%and 10.7%.When the start-stop ratios are 1∶1,1∶2 and 1∶3 respectively,the thermal resistance of scale increases correspondingly by 16.1%,23.0%and 29.0%.With the running cost and the service life of the rubber ball taken into account,the best working condition is when the input rate is 20%,the running time is 60 s with an interval of 120 s,and the start-stop ratio is 1∶2.