Modeling of Irreversible Two-Stage Combined Thermal Brownian Refrigerators and Their Optimal Performance

Abstract

Abstract This paper establishes a model of an irreversible two-stage combined thermal Brownian refrigerator with an intermediate heat reservoir by combining finite time thermodynamics with non-equilibrium thermodynamics. The model is composed of two irreversible thermal Brownian refrigerators working in series. The combined thermal Brownian refrigerator works among three constant temperature heat reservoirs. There exist finite rate heat transfer processes among heat reservoirs and refrigerators. Considering heat leakage, heat transfer losses, and heat flows via kinetic energy change of particles, expressions of cooling load and the coefficient of performance (COP) are derived. The effects of design parameters on system performance are studied. The optimal performance of the irreversible combined thermal Brownian refrigerator is studied. The cooling load and COP are higher when the temperature of the intermediate heat reservoir is close to that of the bottom heat reservoir. Compared with the single-stage thermal Brownian refrigerator, which works between the heat source and sink with the same temperatures, the cooling load of the combined thermal Brownian refrigerator is greater, whereas the COP is smaller.