COP Evaluation for a Membrane Liquid Desiccant Air Conditioning System Using Four Different Heating Equipment

Abstract

Liquid desiccant air conditioning (LDAC) is a promising technology in terms of energy efficiency, comfort and indoor air quality. The major components of a LDAC system are the dehumidifier and regenerator. The most commonly used design of dehumidifiers/regenerators is the packed-bed, which might result in the entrainment of desiccant droplets in air streams. A promising solution for the entrainment of desiccant droplets in air streams is to use a liquid-to-air membrane energy exchanger (LAMEE) as the dehumidifier/regenerator. A membrane LDAC system, which uses two LAMEEs as the dehumidifier and regenerator, is investigated in this paper. The operation of a LDAC system requires the continuous supply of heating and cooling energy to the desiccant solution. In this study, the COPs of four membrane LDAC systems are evaluated when four different heating equipment are used to provide the solution heating loads as follows: a gas boiler, a solar thermal system, a heating heat pump, and the condenser of a solution cooling heat pump. The COPs of the four systems studied are evaluated under wide ranges of six design/operating parameters as follows: ambient air temperature (Tamb) and humidity ratio (Wamb), number of heat transfer units (NTU), solution-to-air heat capacity ratio (Cr*), and solution inlet temperatures to dehumidifier (Tsol,deh,in) and regenerator (Tsol,reg,in). TRNSYS and CYCLE_D programs are used in this paper to simulate the performances of different systems studied. Results show that the membrane LDAC system which uses a single heat pump to provide the solution heating and