The paper presents a mathematical model of combined processes of reverse expansion and suction in the wet steam region, implemented in an ammonia low-speed long-stroke reciprocating compressor stage. The mathematical model is based on the equations of the first law of thermodynamics for a body of variable mass, the equation of state of a real gas, the Clapeyron–Clausius and Newton–Richman equations; various options for implementing the methodology for calculating the heat exchange process in the working chamber of the stage are also considered. A computational and parametric analysis of the effect of the piston speed on the performance losses of the compressor stage and on the degree of dryness of ammonia at the end of the suction process is performed, taking into account the existing uncertainty factors both in terms of the choice of methods for calculating heat exchange processes and in terms of the choice of initial and initial conditions.

The paper presents a theoretical assessment of the effect of the piston speed on the energy efficiency of a steam compression refrigeration cycle based on compression in the area of wet steam, implemented in a low-speed refrigeration compressor stage. The refrigerant R134a was chosen as the working fluid. The numerical calculation of the working process of a refrigeration compressor operating in the field of wet steam was carried out on the basis of a mathematical model and implemented using the Runge– Kutta method of the 4th order in the MathCad package. The calculation of heat transfer was carried out according to the generalized formula for film boiling — condensation inside the pipes. Based on the calculation, the analysis of the effect of the piston speed on the characteristics of the compressor workflow, in particular, on the appearance of its indicator diagram, was carried out.

The paper presents the analysis of influence of the method of calculating the heat transfer coefficient on mathematical modeling of the process of reverse expansion of ammonia in the working chamber of the reciprocating compressor stage (in the area of wet steam). Alternative variants of film and drip schematization of the heat exchange process are considered. The mathematical model is based on the equations of the first law of thermodynamics for a body of variable mass, the equation of state of a real gas, the Clapeyron–Clausius and Newton–Richman equations. Based on the results of the computational and parametric analysis, the applicability of known methods for calculating the heat transfer coefficient to the object under consideration is evaluated.

The paper presents an analysis of the influence on the mathematical modeling of the process of reverse expansion of ammonia in the area of wet steam, implemented in the working chamber of the reciprocating compressor stage, of such uncertainty factors as the method for calculating the heat transfer coefficient, the surface temperature of the wall of the working chamber and the degree of dryness at the beginning of the process of reverse expansion. The mathematical model is based on the equations of the first law of thermodynamics for a body of variable mass, the equation of state of a real gas, the Clausius– Clausius and Newton–Richmann equations. The results of the calculation showed that the instantaneous values of the pressure and temperature of ammonia, as well as its degree of dryness during reverse expansion in the wet steam region, significantly depend on the chosen method for calculating the heat transfer coefficient. The process under consideration is also significantly influenced by the temperature of the walls of the compressor working chamber, in which the compression process is implemented, and the degree of dryness of ammonia at the beginning of the expansion process.