Second-law analysis of vapor compression heat pumps with solution circuit

Journal Article · Fri Jul 01 04:00:00 EDT 1994 · Journal of Engineering for Gas Turbines and Power; (United States)

DOI:https://doi.org/10.1115/1.2906842· OSTI ID:6910604

Amrane, K ^[1]; Radermacher, R ^[2]

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1. ICF Inc., Washington, DC (United States). Global Change Div.
2. Univ. of Maryland, College Park, MD (United States). Mechanical Engineering Dept.

A second-law analysis is conducted on both the single-stage vapor compression heat pump with solution circuit (VCHSC) and its modified version, the cycle with a preheater and additional desorber. The results are compared to a conventional heat pump cycle operating with pure ammonia. The location and magnitude of the irreversibilities of the individual components constituting the cycles are determined. The entropic average temperature is used in computing the irreversibilities. The total work input to the heat pumps is then conveniently decomposed into two parts: the minimum work input or the work of a reversible cycle operating between the desorber and absorber entropic average temperatures, plus an additional input of work caused by the irreversibilities of the different processes of the cycles. The analysis reveals that the compressor is the most inefficient component of the heat pumps with losses accounting for about one fourth of the work input. The irreversibilities in the desorber and absorber are found to be minimum when there is a good match in both the solution and heat transfer fluid temperature glides. By adding a preheater and an additional desorber, the irreversibilities in the single-stage VCHSC are considerably reduced. However, it is shown that it is the preheater and not the additional desorber that has by far the most significant impact on the heat pump's efficiency improvements. Compared to a conventional ammonia vapor compression cycle, the modified VCHSC, which has twice as many sources of irreversibility, shows nevertheless a maximum improvement of 56.1% in second-law efficiency.

• OSTI ID: 6910604
• Journal Information: Journal of Engineering for Gas Turbines and Power; (United States), Journal Name: Journal of Engineering for Gas Turbines and Power; (United States) Vol. 116:3; ISSN JETPEZ; ISSN 0742-4795
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
320303* -- Energy Conservation
Consumption
& Utilization-- Industrial & Agricultural Processes-- Equipment & Processes
EFFICIENCY
ENERGY EFFICIENCY
HEAT PUMPS
IRREVERSIBLE PROCESSES
TEMPERATURE DEPENDENCE
VAPOR COMPRESSION REFRIGERATION CYCLE