Experimental study on heat transfer performance of horizontal tube falling film evaporator for vapor compression distiller.

Compared with multi-effect distillers, vapor compression distillers have advantages of lower energy consumption and high degree of automation. However, the energy saving potential of vapor compression distillers are definitely affected by the temperature difference between the inside and outside of tubes in the evaporator. The heat transfer efficiency of horizontal tube falling film evaporators is very large even the temperature difference is small. Unfortunately, there is a lack of accurate correlations to predict the heat transfer efficiency of this kind of evaporators. Hence, a horizontal tube falling film evaporator test apparatus was constructed and effects of various operating parameters including spray flow, evaporation temperature, heat transfer temperature, inlet steam flow and diameter of tubes were changed to obtain the heat transfer performance. The experimental result reveals that the total heat transfer coefficient increases with increasing spray flow and evaporation temperature, decreases with the increase of heat transfer temperature.