Energy efficient technologies for ultra-low temperature refrigeration

Abstract

Sustainable transition is ongoing in many refrigeration and heat pump applications following what is established in national and international regulations. However, many of them have not controlled ultra-low temperature refrigeration (at –80 °C) because of the challenges associated with these systems’ operation. This chapter presents the main characteristics of several technologies (vapor compression cycle with element variations, sublimation, or absorption cycle) that can be applied for this range of temperatures, focusing on the constructing elements, advantages and drawbacks. Then, recently developed configurations that can appear in commercial systems in the coming years are explored. These configurations are based on vapor compression cascade cycles, including an intermediate heat exchanger, ejector and three-stage. Apart from the additional elements or stages, working fluids used in these configurations are critical parameters for increasing the resulting energy performance and cooling capacity, ending with more sustainable ultra-low temperature freezers.