Analysis of a Combined Absorption Cycle for Power and Cooling with R134a-DEGDME Working Fluid Using a Scroll Expander

This paper presents the integration of a scroll expander into a combined power and cooling absorption cycle driven by low-grade heat sources such as solar energy and waste heat. R134a-DEGDME has been selected as the working fluid mixture to replace the commonly used ammonia-water mixture. The scroll device used here is derived from a compressor. The mathematical model adopted for the expander incorporates a simplified semi-empirical model that calculates the mechanical power, exhaust temperature and supply mass flow rate of the expander at accuracy levels of 9 %, 2 K and 3 %, respectively. Some operating parameters such as the generator (90-100C), condenser (18-26C) and evaporator (-4-10C) temperatures have been varied to investigate the behaviour of the combined cycle. For the selected cycle it is suggested that increasing the generator temperature is beneficial to both power generation and cooling production. However, increasing the condenser temperature is detrimental for both power and cooling. The increase of the evaporator temperature is also favorable for both outputs.