A NUMERICAL STUDY OF INSTANTANEOUS HEAT TRANSFER DURING COMPRESSION AND EXPANSION IN PISTON-CYLINDER GEOMETRY

Abstract

A numerical analysis of the flow and heat transfer in a gas confined by a moving piston inside a valveless cylinder is presented. Repeated compression and expansion of the gas in the cylinder causes it to heat up. The in-cylinder heat transfer is out of phase with the bulk gas-wall temperature difference and the conventional Newton law is not applicable. Instead of being proportional to bulk gas-wall temperature difference the heat transfer should also depend on the time derivative of the bulk gas temperature. An understanding of the in-cylinder heat transfer is essential in modeling compressors, internal combustion engines, and other reciprocating machines. In the present paper the unsteady compressible axisymmetric flow inside the cylinder is modeled using a moving coordinate system and a finite volume methodology. The existing phase difference between the heat transfer and the gas-wall temperature difference is explored.