An experimental study and numerical investigation on fluidized defouling of non-clean water heat exchanger wall

The solid-liquid fluidized defouling technology was applied to prevent and remove fouling of non-clean water heat exchanger. The simulation results show that with the increase of flow rate the maximum erosion rate firstly decreases and then increases, and the maximum erosion rate increases quickly with the increase of sand total flow rate. The shear stress on the pipe wall is high enough to remove fouling. Meanwhile a set of defouling system using sand as defouling particles was established in this paper. The experimental results show that the sand with the diameter of 2 mm could be fluidized if the non-clean water flow rate reaches 0.87 m/s. The recycling efficiency of the sand was almost 95%. The fluidized defouling technology could effectively remove dirt and rust on non-clean water heat exchanger wall. In addition, the heat transfer coefficient increased by 25.6% after the defouling system continued to run for 24 h when the sand particle volume fraction was 6% compared with fouled heat exchanger. In order to reduce erosion and assure the defouling efficiency, the optimum parameters were set as follows: the volume fraction of sand was 4% and the flow rate was 0.87 m/s.