Ideal Adsorption Isotherm Behavior for Cooling Applications.

Area of Science:

• Thermodynamics
• Materials Science
• Chemical Engineering

Background:

• Heat-driven refrigeration offers high energy efficiency, particularly with waste or solar heat.
• Adsorption refrigeration relies on adsorbent-refrigerant pairs for cooling cycles.
• Optimizing efficiency is key for sustainable and cost-effective cooling solutions.

Purpose of the Study:

• To present a novel expression for ideal adsorption step location based on operating conditions.
• To develop a methodology for evaluating intrinsic efficiency of stepwise adsorption materials.
• To enable facile efficiency comparisons for diverse adsorbent-refrigerant pairs.

Main Methods:

• Developed a thermodynamic model for ideal adsorption step location.
• Applied the model to hypothetical stepwise materials for intrinsic efficiency evaluation.
• Extended the analysis to compare different adsorbent-refrigerant pairs using isotherm and adsorption heat data.

Main Results:

• A stepwise adsorbent can achieve up to 85% of Carnot efficiency under ideal conditions.
• Zeolite 13X-water and UiO-66-water pairs show maximum Coefficients of Performance (COP) of 0.52 and 0.88, respectively.
• A two-stage cascading triple-effect adsorption cycle using these materials can achieve a combined COP of 1.50.

Conclusions:

• The developed analysis provides a powerful tool for assessing and comparing adsorption refrigeration efficiencies.
• UiO-66-water demonstrates superior performance at lower regeneration temperatures compared to Zeolite 13X-water.
• Cascading adsorption cycles offer significant potential for enhanced cooling performance using optimized material pairs.