Advances in hybrid compression technology for ultra-low temperature refrigeration achievement

The Hybrid Compression (HC) technology, a synergy between an Absorption Technology Section (ATS) and a Mechanical Vapor Compression Technology Section (MVCTS), was successfully proposed recently for refrigeration and heating, Staicovici (2015a, b, c). In this work, HC advances in the ultra-low temperature refrigeration (ULTR), with emphasis in freeze drying applications, are disclosed. Two types thereof are in research. Both have the same ATS, but different MVCTS's: a) 2 to 4 stage with discharge gas superheating recovery (TVVRC, (Staicovici, 2014)) (HC1), and b) improved HC1 model (HC2). HC1 and HC2 are compared to a standard, 2 to 4 stage and interstage cooling, MVC unit. The MVC, HC1 and HC2 model considers NH3-H2O and NH3, seven evaporator temperatures, T-E = -75, -70, ..., -45 degrees C, three sink source temperatures, Tss = 27, 36, and 45 degrees C, and four HC technology most relevant parameters: i) MVCTS maximum discharge gas temperature, T-cpo ; ii) refrigeration coefficient of performance (COP); iii) MVC vs. HC comparative compressed refrigerant volume, R-v, and iv) exergy efficiency, E-eta . Results show outstanding comparative HC vs. MVC and absolute values of i)-iv) parameters, for same Tss and T-E: A) HC1 and HC2 are compatible with today compressor operation, because T-cpo are smaller by 50 to 170 degrees C than those of MVC; B) HC COP's are much higher than those of MVC, especially in the T-E= -75 to -60 degrees C domain, e.g. by 43 to 65 %; C) HC reduces R-v by 2.5 to 8 times as compared to MVC, promoting compressor physical size reduction; D) HC (eta E) has very high values, E0-62 <= eta (<= 0.78) ; E) The HC2 COP, R-v and E-eta values are better than those of HC1.