Investigation of the Efficiency of Autocascade and Cascade Heat Pumps in Cold Climate
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REFRIGERATING EQUIPMENT AND TECHNOLOGIES INVESTIGATION OF THE EFFICIENCY OF AUTOCASCADE AND CASCADE HEAT PUMPS IN COLD CLIMATE O. A. Zuev, S. A. Garanov, E. V. Ivanova, and A. S. Karpukhin
UDC 621.577
The efficiency of an autocascade heat pump at low ambient temperatures in comparison with a cascade heat pump is investigated. The operation principle of an autocascade heat pump is based on the zeotropic property of mixed refrigerants, the components of which have different boiling points. A mixture of R32/R134a/R365mfc refrigerants was selected as a working fluid for the autocascade heat pump. R410a and R134a were selected as refrigerants for the cascade cycle. The simulation of heat pump cycles was carried out and graphs of the dependence of the coefficient of performance on the ambient temperature were plotted. It is shown that at ambient temperatures below – 20°С the autocascade heat pump is more efficient than a cascade heat pump. At ambient temperatures below – 35°C, the coefficient of performance of the autocascade heat pump is more than 7% higher than the coefficient of performance of the cascade heat pump. Keywords: autocascade heat pump; zeotropic mixed refrigerant; coefficient of performance; cold climate.
In order to improve heat pumps due to the need to increase the energy efficiency of modern heating systems and abandon systems based on fuel combustion, it is promising to use a single-flow cascade cycle or autocascade cycle, first proposed in [1] and described in [2]. In [3], along with a brief history of the development of the autocascade cycle, components for mixed refrigerants (MR) are proposed. Besides, there are a number of published articles on the results of the following studies: operation of an autocascade cycle on R744/R134a and R744/R290 refrigerants [4]; characteristics of an autocascade heat pump on R23/R134a refrigerants with various MR component compositions [5]; operation of an autocascade cycle with two vapor-liquid separators for R23/R134a, R23/R227ea, R23/R236fa, R170/R290, R170/R600a, R170/R600 refrigerants [6]; thermodynamic analysis of an autocascade heat pump for application in cold climates and a proposal to use R143a/R600 MR for these purposes [7]; autocascade heat pump with a solar battery on R32/R290 mixed refrigerant for small water heaters [8]; simulation and tests on an installation with a fractional heat exchanger using R744/R290 refrigerants [9]; during exergy and energy analysis of an autocascade cycle with an ejector, the following was found: the main alternative to an autocascade cycle is a cascade cycle [10]; the properties of the cascade cycle and determination of the optimal temperature between the lower and upper stages of the cascade installation [11]; heat pump with cascade and single-stage cycles [12]. In this study, the efficiency of an autocascade heat pump and a cascade heat pump (in comparison) for their operation in a cold climate is investigated. Bauman Moscow State Technical University, Russia; e-mail: [email protected]. Translated from Khimichesko
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