Experimental Investigation of a New Enthalpy Exchanger with Low Absorbent Carryover Designed for Liquid Desiccant Dehumidification System

Abstract

In this paper, the absorbent carryover effect in a designed counter-flow enthalpy exchanger is investigated. In a built prototype of the liquid desiccant dehumidifier, air and the absorbent solution are in contact and flow through a packed multi-channel polymer tower in a counter-flow pattern. To avoid the absorbent carryover, the tower is equipped with an eliminator. Experimental measurements show that applying wick of hydrophilic type material to the channels' surfaces of the eliminator and the enthalpy exchanger, while increasing the rate of dehumidification, reduces the solution carryover effect, however, it does not eliminate it. To eliminate the effect, pumping the solution into the tower is interrupted periodically. It was found that by adjusting the pump switching frequency, the carryover effect can be eliminated. The best result is achieved when the period of switching on state is about a quarter of the off state one and the total period is about 25 seconds. Since the solution pump is turned off frequently, the cost of electrical power is reduced significantly. Also, the measurements show that while the dehumidification ability of the tower is improved in a steady state operation its regeneration performance is not.

Keywords

• carryover
• liquid desiccant
• counter flow
• polymer exchanger
• packed tower