Thermodynamic Analysis of a Vapor-Compression Refrigeration Cycle – ME235 Final Project
As part of a team in ME235 (Thermodynamics) at the University of Michigan, I contributed to a detailed analysis of vapor-compression refrigeration and heat pump cycles using four different working fluids: R-134a, R-12, R-22, and NH₃. Each team member was responsible for evaluating the full thermodynamic behavior of one refrigerant. My assigned fluid was R-12.
I conducted a complete thermodynamic analysis of the R-12 cycle, including calculating net work input, heat transfer in the evaporator and condenser, and coefficients of performance (COP) for both refrigeration and heat pump modes. Using provided inlet conditions and isentropic efficiency assumptions, I applied energy and entropy balance equations to determine key state properties and performance metrics. I then performed a sensitivity analysis by varying the maximum cycle temperature to examine its effect on entropy generation and cycle efficiency. Results showed a clear trade-off: as the maximum temperature increased, COP decreased while entropy generation rose—indicating greater irreversibility in the cycle.
As a team, we compared the performance and feasibility of each fluid. While NH₃ exhibited the highest theoretical efficiency, safety concerns made R-22 the most balanced option in terms of performance and practicality. We also identified evaporator pressure as a critical lever for improving system performance without requiring changes to hardware.
The project involved engineering communication, collaborative problem-solving, and technical analysis aligned with real-world refrigeration system design. Our final deliverable included a written technical report and a team presentation, supported by bar charts, p-v and T-s diagrams, and entropy generation comparisons. Through this work, I developed a stronger understanding of thermodynamic cycles, refrigerant behavior, and how to optimize system efficiency using both theoretical and applied methods.