Thermal engineers usually face two kinds of problems: design of new systems, where multiple alternatives for each composing unit of the system can fulfill the design requirements and/or assessment of exiting systems, where they usually work at off-the-design conditions due to deterioration of their efficiencies. The present paper addresses possible solutions to such problems via the Monte-Carlo method (MCM) applied to compressors as major units in airconditioning (A/C) and heat pump (H/P) systems having Carbon Dioxide (R744) as working fluid. Diversity of the effects of system design, process parameters and fluid properties within and across the saturation line hinders an overall-view of hidden capabilities and limitations of the compressors. Thus, it is hard to apply any appropriate optimization methods for their better design, besides the difficulty in assessing their performance along their working lifetime. In an answer to the above two points, the present paper utilizes the powerful MCM to investigate and expose the effects on compressor performance of all controlling parameters, randomly selected from their variation ranges within and across wet/saturation region to the transcritical dry region of R744. For each selected set of parameters, a complete analysis is calculated to determine the performance of the compressor. This process is repeated about 500 times to randomly cover the variation spaces of the parameters. The study reveals that MCM can fairly handle the parametric design and evaluation study of compressor performance. It shows that the initial temperature has a greatly decreasing effect on compressor specific displacement volume per unit work and to a less extent on size of compressor, while its effects on all other parameters are insignificant. Initial pressure has similar expected trends. Final to initial temperature ratio has increasing effects on both final pressure and work of compressor and decreasing effects on both second law efficiency and specific displacement volume per unit work. The application of MCM to the parametric compressor performance presented here could open many ways for further theoretical design optimization and experimental justification of the compressors and hence greatly limits the trade-off methods that are usually adopted in the selection of such units.

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