The effect of outer surface roughness for evaporator tube in the desalination plant

Abstract

The purpose of this study is to investigate the evaporator tube performance with different outer surface roughness and under different feeder water load. A test rig with horizontal aluminum evaporator tube had been designed and fabricated to collect the steam from boiler and converted it into condensate. The study was carried out on two aluminum evaporator tubes with different outer surface roughness and under five different feeder water loads. The performance of each evaporator tube was based on the collected amount of condensate. A theoretical relationship was modified from previous study which derived based on the film wise condensation Nusselt’s equation, heat transfer equation and falling film equation. Theoretical calculation was conducted with Maple software and the outcomes were compared with the experimental results. Results showed that the mass flow rate of the condensate increases as the feeder water load increases for both the tube. The evaporator tube with higher outer surface roughness showed better performance compared with the one with lower outer surface roughness. Also, the modified theoretical relationship showed higher accuracy compared to the previous study. Based on the results, the evaporator tube outer surface roughness plays an important role in the evaporator tube performance.