Ideal mass transfer cycle and thermal performance optimization for liquid desiccant air conditioning system

Abstract

Mass transfer processes, cycles and associated conversion devices find wide application in air-conditioning. However, several optimization problems concerning mass-related devices and systems persist due to the absence of corresponding optimization principles and methods. For instance, akin to the Carnot cycle representing the ideal heat-work conversion cycle, what constitutes the ideal mass transfer cycle? Moreover, how can this ideal mass cycle be utilized to optimize practical systems? In this paper, a new approach based on inverse problem and variation method is utilized to address these problems. Firstly, as analogy to Carnot heat cycle, a four-process reversible ideal mass cycle is deduced to achieve maximal overall conversion efficiency. Secondly, the cycle perfectness index (ε) is defined, to depict the performance disparity of a certain practical irreversible mass cycle from the ideal one. Thirdly, three typical liquid desiccant air-conditioning processes are compared with considerations of solution/air states and system coefficient of performance (COP). This study aims to offer fresh insights into mass transfer processes and systems, providing guidance and references for optimizing practical system designs involving mass cycling, including liquid desiccant air conditioning systems for indoor dehumidification in buildings.

Keywords

• Mass transfer
• Thermodynamic cycle
• Liquid desiccant
• Thermal performace
• Air conditioning