Development of cooling systems on the basis of absorption water-ammonia refrigerating machines of low refrigeration capacity

Abstract

An analysis of the cycles of an absorption water-ammonia refrigerating machine (AWARM) is carried out in a wide range of operating parameters (temperature of the heating medium: 45...145 °C, outdoor temperature: 10...43 °C, temperature of the cooling object: minus 25...5 °C). It is shown that under the considered operating conditions, the AWARM positive effect on the energy efficiency of the AWARM is low outdoor air temperatures and high temperatures of the heating heat source. A promising cooling system based on low refrigerating capacity AWARM is developed using solar thermal energy and the technology of using natural seasonal and daily temperature potential of atmospheric air, including using night radiation cooling (NRC). The key elements of the cooling system are: storage tank; cooling system based on AWARM with combined sources of heat load; heat removal system in the mode of convection and radiation at night. It is shown that AWARM in combination with a cold storage tank allows to provide a wide range of refrigeration processing by selecting a working substance with a phase transition (melting-solidification). Working substances with a temperature level are recommended: minus 25 °C (for products of animal origin); 0 °C (primary refrigerated processing of milk); 5 °C (for fruits and vegetables). It is advisable to ensure the guaranteed heat removal from the cold storage tank of the cooling system in the passive «thermal diode» mode with the help of two-phase thermosyphons. When working with solar collectors with water, as a coolant for the AWARM generator, the AWARM scheme with a booster compressor in front of the condenser is proposed. It is shown that the greatest effect of the NRC technology in heat removal systems can be achieved in the high-mountainous regions of the planet with minimal atmospheric humidity, for example, in Kazakhstan.