Thermodynamics
The final report should be divided into several sections containing:
• Problem statement
• Introduction (define design specifications, realistic constraints, and design variables) define:
o design specifications,
o realistic constraints,
o design variables
o method of approach
• Alternative design considerations
• Results and discussion
• Economic analysis
• Conclusion
• List of references.
Remember to number equations, tables, and figures in your report (use the textbook as a guide). Include captions for each table or figure and paginate the report. Include detailed calculations in the appendix.
Design Problem Statement
A vapor-compression refrigeration system operating continuously is being considered to provide a minimum of 80 tons of refrigeration for an industrial refrigerator maintaining a space at 2oC.
The surroundings to which the system rejects energy by heat transfer reach a maximum temperature of 40oC. For effective heat transfer, the system requires a temperature difference of at least 20oC between the condensing refrigerant and surroundings and between the vaporizing refrigerant and refrigerated space.
The project manager wishes to install a system that minimizes the annual cost for electricity (monthly electricity cost is fixed at 6.5 cents for the first 250 kW.h and 7.2 cents for any usage above 250 kW.h).
Your team is asked to design the most efficient vapor compression refrigeration cycle as compared to most basic standard vapor compression refrigeration cycle.
The design alternative may include adding flash intercooling, employing power-recovery turbine(s) in lieu of expansion valve (s).
For each alternative, consider three refrigerants: ammonia, Refrigerant 22, and Refrigerant 134a.
In your design analysis, make realistic assumptions for isentropic efficiencies of turbines, compressors, pumps, or heat exchanger effectiveness. Based on electricity cost, recommend the best choice between alternative designs and a suitable refrigerant.
Other than electricity cost, what additional factors should the team consider in making a final selection (e.g. the cost of additional components into the cycle)? Prepare a written report including results, conclusions, and recommendations.