Liquid-state dipolarcaloric refrigeration cycle with nitrate-based salts

Abstract

Environmental burden of vapor compression refrigeration has driven interest in alternatives. Caloric refrigeration cycles offer a path forward but most rely on solid-state materials with limited temperature lift, low performance, and poor fluidity, which hinder scalability. We introduce a liquid-phase dipolarcaloric refrigeration cycle utilizing endothermic dissolution of nitrate-based salts regenerated via electrodialysis. This cycle achieves large adiabatic temperature changes and high coefficients of performance. We identify effective salt-water pairs and validate the cycle experimentally, supported by thermodynamic modeling. Among these, ammonium nitrate is suited for refrigeration, while potassium nitrate is appropriate for air conditioning. The system uses abundant, low-cost materials, and its fluidic nature ensures efficient heat transfer and scalability. This work establishes dipolarcaloric cooling as a viable alternative for environmentally responsible refrigeration.