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Numerical and experimental investigation of the cylinder inlet temperatures for different designs of the suction line of a hermetic reciprocating compressor.

Number: 1261

Author(s) : GRÄF J., TUHOVCAK J., BRANCHER R. D.

Summary

Due to the fact, that the performance of a hermetic reciprocating compressor is significantly affected by the temperature of the refrigerant entering the compression chamber, it is of utmost importance to determine the cylinder inlet temperature when it comes to the improvement and the development of a compressor. Especially the physical phenomenon of suction gas heating which occurs due to the heat transfer between the heat sources inside the compressor and the inflowing refrigerant with low temperature has to be examined to infer the cylinder inlet temperature and thus the performance of the entire compressor. The main motivation for this investigation is based on the fact that the currently used suction line design of a compressor model allows small liquid droplets included in the largely gaseous refrigerant to be sucked in, which leads to irregularities in the compression process and in various cases to the destruction of the compressor. The trigger for this circumstance is the defrosting mechanism in the evaporator, which melts the frost that has formed in the cooling element. The evaporator is usually equipped with a channel through which the liquid is supposed to drain. However, some of this liquid sometimes ends up directly in the suction line because it mixes with the refrigerant before it enters the compressor. From a  thermodynamic point of view, the deliberations to remedy this problem place new requirements on the design of the suction line. The superordinate objective of this paper is to draw a meaningful comparison of different suction line configurations, while taking the cooling capacity, the power consumption and the coefficient of performance of this compressor into consideration. To examine the effects of the various design changes on the suction gas heating process, three-dimensional flow simulations are suitable for computing the different cylinder inlet temperatures. With the  intention to reach maximum accuracy of the numerically obtained solutions, a mesh refinement study is performed on the one hand, and experimentally determined temperature values inside
the compressor are defined as non-adiabatic wall boundary conditions on the other hand. In addition to the visualization of the suction gas heating process, the greatest benefit of these simulations is the calculation of the cylinder inlet temperatures, which can be used for the numerical determination of the compressor parameters in relation to its performance. Aiming to validate the results calculated with modern computer technology, experimental measurements of the operating compressor are generated with a calorimeter and compared with one another. As a result, it is finally possible to agree on a compressor design that not only prevents the liquid droplets from being sucked in, but also shows the lowest loss of compressor performance with the smallest increase of the cylinder inlet temperature.

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  • Original title: Numerical and experimental investigation of the cylinder inlet temperatures for different designs of the suction line of a hermetic reciprocating compressor.
  • Record ID : 30030294
  • Languages: English
  • Subject: Technology
  • Source: 2022 Purdue Conferences. 26th International Compressor Engineering Conference at Purdue.
  • Publication date: 2022/07/15

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