Experimental study on the on-line cleaning system influencing the heat transfer performance of shell-tube heat exchanger

Fouling resistance has an obvious effect on the heat transfer performance of shell-tube heat exchangers, among all kinds of cleaning methods, rubber ball on line automatic cleaning system is a new and effective method. In this paper, an experimental device is built and installed a rubber ball online cleaning system based on a gas-fired lithium bromide absorption-refrigerating unit, the influence of cleaning on the heat transfer performance of shell-tube condenser and the coefficient of performance (COP) of direct-fired unit was experimentally studied. The results show that the fouling resistance increases while the COP decreases with the increase of the running time when the rubber ball online cleaning system without works. The ball percentage, running time and start / stop ratio of on-line cleaning system have significant effects on fouling resistance. When the ball percentage is 10%, 20%, and 30%, respectively, the thermal resistance increases by 32.8%, 20.8% and 8.9%, respectively. As the running time increases from 20 s, 40 s to 60 s, respectively, the thermal resistance increases by -20.8%, 17.9% and 10.7%, respectively. When the start/stop ratio is set at 1:1, 1:2 and 1:3, respectively, the thermal resistance increases by 16.1%, 23.0% and 29.0%, respectively. On comprehensive consideration of cleaning effect and energy consumption, it is recommended that the percentage of ball is 20%, the service pump operates for 60 s and stops for 120 s, and the start-stop ratio is 1:2. For the minimum operating cost, an interval cleaning mode is recommended, and the optimal cleaning interval is 28 h, the optimal cleaning time is 8 h.