Comparison of the Characteristics of Low-Temperature Scroll Compressors for Heat Pump Applications
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REFRIGERATING EQUIPMENT AND TECHNOLOGIES COMPARISON OF THE CHARACTERISTICS OF LOW-TEMPERATURE SCROLL COMPRESSORS FOR HEAT PUMP APPLICATIONS E. Kh. Shungarov and S. A. Garanov
UDC 621.574
Ceteris paribus, the efficiency of heat pumps is higher in the systems with moderate temperature levels for heat consumers. The selection of a scroll compressor for a low-temperature heat pump is defined by its operating characteristics which include isentropic efficiency, feed coefficient and compression ratio. To demonstrate the manufacturer’s specifications for low-temperature scroll compressors, the authors investigated the compressors of three manufacturers: Copeland, Danfoss and Invotech. The study of low-temperature compressors was carried out in the range of refrigerant boiling temperatures from 0 to minus 40 °С (in increments of 5 °С). The obtained data were used to plot diagrams of respective dependences for various compressor models. Keywords: air heat pump, scroll compressor, isentropic (adiabatic) efficiency, volume ratio, compression ratio.
The main advantages of scroll compressors are high energy efficiency, high reliability, and good balance [1, 2]. However, the disadvantage of scroll compressors is that a complex system of forces acts on the movable scroll, which is manufactured with high precision. The selection of a scroll compressor for a low temperature heat pump application is determined by the compressor performance characteristics, which include compressor isentropic efficiency, feed coefficient and compression ratio. Isoentropic efficiency is the ratio of isentropic work of compression lis to the specific actual work of compression lact [3]: ηis = lis /lact. The feed coefficient is the ratio of the volume of vapors sucked in by the compressor to the (geometric) volume these vapors flow through [4]: λ = V/Vh, where V is the actual volumetric capacity of the compressor corresponding to the suction conditions, m3/s; Vh is the described compressor volume through which vapors flow, m3/s. It is known that the performance of a compressor depends on the degree of gas compression in the working chambers. The increase in gas pressure during compressor operation is characterized by the pressure increase or Moscow Bauman State Technical University, Russia; e-mail: [email protected], [email protected]. Translated from Khimicheskoe i Neftegazovoe Mashinostroenie, Vol. 56, No. 5, pp. 27–30, May, 2020. 378
0009-2355/20/0506–0378
© 2020
Springer Science+Business Media, LLC
COMPARISON OF THE CHARACTERISTICS OF LOW-TEMPERATURE SCROLL COMPRESSORS FOR HEAT PUMP APPLICATIONS
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Fig. 1. Isentropic efficiency versus compression ratio for Invotech compressors of the YF-E1G-100 series. compression ratio, that is, the ratio of the pressure at the outlet of the compressor P2 to the pressure at the inlet of the compressor P1 is [3]: πc = P2 /P1. Thus, the higher the compression ratio, the lower the compressor capacity. Technical and economic requirements for compressors for air heat pumps are: 1. High isentrop
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