Vapor compression refrigeration systems require high grade energy (electrical or mechanical) for operation. In two-pressure absorption cycles, most of the input energy can be supplied as heat. Such devices can be configured to harness locally available inexpensive thermal sources – such as waste heat or solar energy. However, these two-pressure absorption cycles still require electrical infrastructure to drive the solution pump and fans. Single pressure absorption cycles, such as the diffusion absorption refrigeration (DAR) (Figure 1), cycle operate on similar principles to conventional absorption cycles, but require no mechanical input. Working fluid circulation is achieved passively with a bubble pump and free convection in a gas loop. Such systems are well suited to applications in remote locations, where electrical resources are limited, or where low-maintenance operation is beneficial.
In this investigation, a fully passive air-cooled diffusion absorption refrigeration system was demonstrated (Figure 2). Alternate working fluids (NH3-NaSCN-He), a liquid heated bubble-pump generator, and an enhanced absorber design were employed, enabling refrigeration with source temperatures as low as 110°C. This system is well suited to off-grid applications, such as medicine and vaccine refrigeration in developing countries. The experimental system was developed in collaboration with the Sustainable Thermal Systems Laboratory at Georgia Tech. Representative cooling coefficients of performance (COPs) are presented in Figure 3.
- Rattner, A.S., Garimella, S., 2015. Coupling-fluid heated bubble pump generators for low-temperature fully thermally activated single pressure absorption systems. Science and Technology for the Built Environment (In Press). DOI: 10.1080/10789669.2015.1004978.
- Rattner, A.S., Garimella, S., 2012. Design and analysis of the absorption component in waste-heat- driven diffusion absorption refrigeration systems. ASME Heat Transfer Conference, San Juan, PR. DOI: 1115/HT2012-58608.
- Rattner, A.S., Garimella, S., March 2012. Simulación a nivel de componente y sistema acoplados en un sistema de refrigeración por absorción difusión para aplicaciones residenciales. Frio Calor Aire Acondicionado: 3–12. Link.
- Rattner, A.S., and Garimella, S., 2011. Coupled component- and system-level simulation of a diffusion absorption refrigeration system for residential applications. International Sorption Heat Pump Conference, Padua, Italy.