Low-source-temperature diffusion absorption refrigeration. Part I: Modeling and cycle analysis

• A low-source-temperature fully thermally activated refrigeration system is proposed.
• Detailed component- and system-level design models are formulated.
• Enhanced bubble-pump generator and absorber configurations are investigated.
• System performance is evaluated over a range of realistic operating conditions.
• Refrigeration grade cooling can be delivered with low source temperatures (<130 °C).

The diffusion absorption refrigeration (DAR) cycle offers a potentially fully thermally activated cooling technology. However, most implementations operate with high source temperatures, forced liquid cooling, or elevated evaporator temperatures (≳5°C≳5°C). Additionally, few component design resources are available in the literature. In Part I of this investigation, a fully passive DAR design is proposed. Reduced temperature operation is enabled with alternate working fluids (NH3-NaSCN-He), a distributed heated bubble-pump generator (BPG), and an enhanced absorber. Detailed models are formulated for the BPG, condenser, evaporator, absorber, and gas circulation loop. These are integrated to yield an overall system model. System behavior is evaluated over a range of operating conditions. With the necessary and reasonably expected component performances, refrigeration COPs of 0.11–0.26 can be achieved at design conditions (Tamb = 24 °C) with low source temperatures (110–130 °C) and passive air cooling. In the accompanying paper (Part II), this refrigeration system is experimentally demonstrated, and the proposed models are evaluated.