Experimental investigation of heat and mass transfer characteristics in direct contact exchanger

An innovative design of a direct contact exchanger was developed using internal volume of short vertical tubes as an active zone of heat and mass transfer. There was conducted experimental investigation of heat and mass transfer between hot water and atmospheric air in flooding flow at air inlet velocity of 4-11 m/s, inlet air temperature of 11-18 degrees C, inlet air relative humidity of 63-88% and inlet water temperature of 16-55 degrees C. The empirical relations for calculating convective heat transfer and mass transfer in the range of air Reynolds numbers from 9.10(3) to 30.10(3) were obtained. It was shown that air velocity has a decisive influence on heat and mass transfer. The geometrical dimensions of the flooding tube were determined, which provided the most efficient operating regime (with the tube height from 0.1 to 0.25 m, and diameter - from 25 to 45 mm). An efficient application of an innovative direct contact exchanger both for cooling towers and for cooling the gas flow (exchangers for waste heat recovery from flue gases) was outlined. (C) 2020 Elsevier Ltd. All rights reserved.