Numerical analysis and experimental assessment of the cylinder temperature in a reciprocating compressor

Accurate evaluation of the thermal deformation is important to the analysis of reciprocating compressors since the induced deformations are responsible of the thermal stresses on the cylinder. The cylinder body experiences a non-uniform temperature distribution, with the presence of hot and cold spots, creating a bending strain on the structure. A cylinder cooling system is designed to control the uniformity of the temperature field and to reduce the fresh gas heating due to a hot cylinder body, improving the volumetric efficiency. Due to the difficulties associated with obtaining detailed data on the heat transfer processes by experimental means, a more and more important role is played by numerical analysis in reciprocating compressor design. This paper shows the capability of a conjugate heat transfer (CHT) simulation for a double-acting reciprocating compressor cylinder in accurately predicting both the thermal state of the compressor cylinder and the temperature field of the cooling water. The results of the three-dimensional simulations of the water-circuit flow field and the thermal conduction inside the solid metal were compared to temperature measurements collected on a dedicated test bench for both the coolant and the metal structure. Satisfactory agreement was obtained between the experimental data and the numerical computations. In addition, three different modifications for the CHT model were introduced in order to obtain a better match with the experimental results. The suitability of using the CHT simulation as an efficient tool for replicating the actual condition of the reciprocating compressor was analyzed and discussed.