Conference Year

2014

Keywords

improve, cooling capacity, heat transfer, Ashby, material

Abstract

Many ways is possible to improve the compressor efficiency, like to reduce the mechanical losses through valve or bearing which represents from 20% to 30% of total electric consumption power on the compressor. Another ways is to decrease the pressure drop through the compression circuit of the compressor, which can reduce the temperature variation through the compressor…etc. In our case of study, we will be interested in the heat transfer and pressure drop through the suction circuit. In this paper, we present the challenge done on the heat transfer reduction through the suction line of the CAJ4519Z compressor, in reducing from 10°C to 20°C the flow temperature through the suction line and, thus improve the cooling capacity in increasing density of the flow. Indeed, according to the mechanical conception of the compressor, the suction line, the fresh part of the flow, is in contact with the discharge line, the hot part of the flow, at the cylinder head part. Thus, thermal conduction phenomena at this level heat up the fresh flow of the suction line therefore decrease the density of the flow which impacts on the global cooling capacity of the compressor. In this case of study, the cylinder head is on cast iron material, and separates the suction line (fresh flow at 64°C) with the discharge line (hot flow at 115°C) by a thickness wall of 0.8cm. Consequently, the fresh flow of suction line reheats by the conductivity and loses between 10°C and 20°C according to the operating condition. To reduce the conductivity phenomenon on the cylinder head, a judicious choice of material is done according to the Ashby methodology based on the conductivity coefficient, and a new concept of cylinder head is done. Before, testing the new concept of the cylinder head, CFD (Computational Fluid Dynamics) simulation allows understanding the improvement through the standard and new cylinder head concept, and allows defining the position of the sensor. The laboratory test result confirms the simulation results. Thus, thanks to the thermal characteristic of the material and re design the cylinder head part, we can reduce the temperature and improve by 2% ( average value) the cooling capacity of the compressor.

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