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This work presents a methodology for the numerical simulation of reed valves of a small-size reciprocating compressor (approximately 200 mm in length, 60 mm in diameter), oil free and operating at high frequency. A fluidstructure interaction methodology is employed, where the fluid domain is modeled by the tridimensional transient Navier-Stokes equations, while the solid domain is governed by a beam model considering geometrical contacts between valves and stoppers (valve plate, piston, etc.) Results are shown for mass flow, pump power consumption and valve losses for evaporating temperatures ranging from -15 degrees Celsius to +40 degrees Celsius, and condensing temperatures from +45 degrees Celsius to +85 degrees Celsius. Finally, numerical results were compared to experimental data.

In this paper, an algebraic formulation which expresses the dimensionless rate of entropy generation as a function of the heat exchanger geometry (number of transfer units), the thermal-hydraulic characteristics (friction factor and Colburn j-factor), and the operating conditions (heat transfer duty, core velocity, coil surface temperature, and fluid properties) is derived. It is shown that for heat exchanger with constant wall temperature (i.e., condensers and evaporators), there does exist a particular number of transfer units which minimizes the dimensionless rate of entropy generation. An algebraic expression for the optimum heat exchanger effectiveness, based on the working conditions, heat exchanger geometry and fluid properties, is also presented. The theoretical analysis led to the conclusion that a high effectiveness heat exchanger does not necessarily provide the best thermal-hydraulic design.