Use of coolants at phase transition for foodstuffs refrigeration.

Abstract

One of the ways to intensify the processes of foodstuffs refrigeration and to reduce the electric power consumption at operation of indirect cold supply systems is use of the coolers at phase transition. That includes the coolers on the base of water solutions of nonorganic salts, alcohols, sugars or salts of organic acids. During their cooling the crystals of water ice are accumulated in the solutions. The technological immersion method of products refrigeration using ice slurry is used in different countries including Russia. The investigations on the application of ice slurry from the water solution of sodium chlorides (salt concentration is more than 3 %) during the fish refrigeration processes with definition of heat exchange intensity, refrigeration velocity and shelf life of refrigerated fish were carried out. The technological equipment that gives the possibility to perform the immersion refrigeration process under industrial conditions was created in Russia. Rather perspective is the application of coolers at phase transition in the closed loop of air conditioning. In this case the accumulation of cold takes place at low loads thanks to the increase of ice crystals concentration in the circulating solution with their following activation when the cold consumption increases. The cold accumulation may be implemented at the expense of the accumulation of the solution with ice crystals in special systems. The paper cites the technoeconomic comparison of refrigerating systems operating on single-phase coolers and coolers at phase transition. In both systems for calculations is assumed the use of state-of-the-art screw compressors, plate-type evaporators or ice slurry generators (with cold accumulation). The comparison is based on the experimental results, obtained on investigation of the hydraulic resistance of coils and coefficients of heat transfer of heat exchange apparatuses operating on ice slurry.