Analysis Of Dynamic Heat Transfer Coefficient In a Reciprocating Compressor By Immersed Solid Method in CFD

Accurate mapping of heat transfer inside the Hermetic compressor has been a major challenge for the designing and evaluation of performance. Various methodologies have been adopted for the thermal mapping such as experimental analysis, numerical methods, CFD etc. Mapping is further complex when the motions of multiple components are considered. In this work heat transfer is mapped inside a reciprocating hermetic compressor by considering the rotation of crankshaft and associated motion of connecting rod and piston. The refrigerant gas and oil in the sump are used as the working fluids for this conjugate heat transfer model. The motion is imposed on the moving parts through trigonometric relations using immersed body technique in Ansys CFX. The transient analysis is carried out on a simplified model with few thermally sensitive components to save computation cost. The heat transfer from the omitted components are imposed as boundary conditions in the simplified model. A steady simulation has been done with the simplified model providing ‘zero’ motion as a reference for comparison and as an initial condition for the transient run. Finally, transient run was carried out and results were compared with the steady state. It has been found that heat transfer between the fluids and components increased up to 600% with the imposed motion. The transient heat transfer coefficients were used in a 1D simulation model and compared with experimental results