An exergy method for compressor performance analysis

McGovern, Jim; Harte, S.

doi:10.1016/0140-7007(95)98165-h

Cited by 29 publications

(13 citation statements)

References 2 publications

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“…The exergy destroyed in the compressor is caused by the refrigerant vapour warming at the inlet of the cylinder, the imperfection of the stuffing between the piston and the cylinder and the losses in the suction and discharge valves. These losses can rise or diminish when the speed is varied (McGovern and Harte, 1995;Stecco, 1986) The refrigeration power control obtained varying the compressor speed related to the refrigeration systems, has been studied during the last 20 years (Qureshi and Tassou, 1996;Pedersen et al, 1999;Jang and Jeong, 1999;Binneberg et al, 1999;Qureshi and Tassou, 1998). To modulate the compressor speed an inverter can be used.…”

Section: Introductionmentioning

confidence: 97%

Refrigeration plant exergetic analysis varying the compressor capacity

Aprea

Rossi

Greco

et al. 2003

Int. J. Energy Res.

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The paper presents an exergetic analysis of a vapour compressor refrigeration plant when the refrigeration capacity is controlled by varying the compressor speed. The aim is performance evaluation of both the whole plant and its individual components. The analysis of the exergy flow destroyed in each device of the plant varying the compressor speed has been carried out in order to determine the relative irreversibility of the plant components. The vapour compression plant is subjected to a commercially available cold store. The compressor working with R22, R407C and R507 and designed for a revolution speed corresponding to 50 Hz supply current frequency, has been used varying the frequency in the range 30–50 Hz. In this range, the most suitable working fluids proposed as substitutes of R22, as R407C (R32/R125/R134a 23/25/52% in mass), R507 (R125/R143A 50/50% in mass) and R417A (R125/R134a/R600 46.6/50/3.4% in mass), have been tested. The variable-speed compressor is fitted with a pulse-width modulated source inverter (PWM) predominantly used in medium power applications due to its relatively low cost and high efficiency. The\ud basic difference between variable speed refrigeration and conventional refrigeration systems is in the control of the system capacity at part-load conditions. The conventional refrigeration systems are characterized by compressor on/off cycles arising from by the thermostatic control. On the contrary when the inverter is used the capacity of the refrigeration system is matched to the load regulating the compressor motor speed. When the control of the compressor capacity is obtained by varying its speed there is an energy saving with respect to the thermostatic control. The best results of the exergetic analysis have been obtained using R22 followed by the non-azeotropic mixture designed as R407C that confirms, among the fluid candidates R22 substitution a better performance, shown also at the compressor nominal speed

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Section: Introductionmentioning

confidence: 97%

Refrigeration plant exergetic analysis varying the compressor capacity

Aprea

Rossi

Greco

et al. 2003

Int. J. Energy Res.

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“…In particular, in the compressor the shaft power wastage can be attributed to friction, irreversible fluid mixing, irreversible heat transfer and fluid throttling; these defects can be considered as exergy destruction rates. However, a more detailed analysis related to the exergy destroyed in the compressor is reported in Fornasieri (1983) and Govern and Harte (1995). Moreover, on decreasing the compression ratio the irreversibility of the expansion valve also decreases when the compressor speed decreases.…”

Section: Resultsmentioning

confidence: 94%

An experimental analysis of a thermodynamic model of a vapour compression refrigeration plant on varying the compressor speed

Aprea

Renno

2004

Int. J. Energy Res.

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The principal aim of this paper is the study of a thermodynamic model that simulates the working of a vapour compression refrigeration plant. The model allows the evaluation of plant performances when the compressor capacity is regulated varying its velocity by means of an inverter inserted into the compressor electric motor feeder. This type of control allows to match continuously the compressor refrigeration capacity to the load, determining an energy saving in comparison with the classical thermostatic control. In particular, in this paper the outputs of the model are compared with the experimental results. The vapour compression experimental refrigeration plant, whose evaporator is located in a commercially available cold store, presents a semi-hermetic reciprocating compressor able to work with the R22 and some its substitutes, and designed for a revolution speed corresponding to a 50Hz frequency of a compressor electric motor supply current. The comparison of model and experimental results is realized by varying the supply current frequency of the compressor in the range 30–50 Hz using the R407C (R32/R125/R134a 23/25/52% in mass) that represents the most suitable working fluid for the R22 substitution. The model experimental comparison results reported in terms of condensation temperature, compression ratio, condensation power and Coefficient Of Performance are completely acceptable. Moreover, an exergetic analysis is realized to explain the performances of the plant components when the compressor speed is varied

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“…As an example, McGovern and Harte [16,17] included internal thermal resistances in exergy analyses of the operation of refrigeration compressors.…”

Section: Heat Input Rate and Thermal Efficiency Of A Heat Engine At Mmentioning

confidence: 99%

Thermodynamic Analysis of Closed Steady or Cyclic Systems

McGovern¹

2015

Entropy

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Closed, steady or cyclic thermodynamic systems, which have temperature variations over their boundaries, can represent an extremely large range of plants, devices or natural objects, such as combined heating, cooling and power plants, computers and data centres, and planets. Energy transfer rates can occur across the boundary, which are characterized as heat or work. We focus on the finite time thermodynamics aspects, on energy-based performance parameters, on rational efficiency and on the environmental reference temperature. To do this, we examine the net work rate of a closed, steady or cyclic system bounded by thermal resistances linked to isothermal reservoirs in terms of the first and second laws of thermodynamics. Citing relevant references from the literature, we propose a methodology that can improve the thermodynamic analysis of an energy-transforming or an exergy-destroying plant. Through the reflections and analysis presented, we have found an explanation of the second law that clarifies the link between the Clausius integral of heat over temperature and the reference temperature of the Gouy-Stodola theorem. With this insight and approach, the specification of the environmental reference temperature in exergy analysis becomes more solid. We have explained the relationship between the Curzon Ahlborn heat engine and an irreversible Carnot heat engine. We have outlined the nature of subsystem rational efficiencies and have found Rant's anergy to play an important role. We postulate that heat transfer through thermal resistance is the sole basis of irreversibility.

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An exergy method for compressor performance analysis

Cited by 29 publications

References 2 publications

Refrigeration plant exergetic analysis varying the compressor capacity

Refrigeration plant exergetic analysis varying the compressor capacity

An experimental analysis of a thermodynamic model of a vapour compression refrigeration plant on varying the compressor speed

Thermodynamic Analysis of Closed Steady or Cyclic Systems

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