Review Example 5-3. A marketing major hired by your firm thinks that if you put a little turbine in your refrigerators instead of the throttling valve, he can write up good ad copy that your refrigerators are the only ones on the market with these energy recovery turbines. If the inlet and outlet streams for the turbine were both identical (in ALL properties) to the inlet and outlet streams for the valve, what would be the rate at which work is produced?
A. 0 J/s
B. -3.8 kJ/s
C. -1.9 J/s
D. -1.25 J/s
E. Insufficient information to solve
A. Correct. The data given was obtained for a valve, and when these same values of enthalpy are substituted into the turbine energy balance, it returns zero work. Either new outlet stream conditions must be determined OR the turbine must be described (e.g., efficiency) in order for us to get a more realistic answer.
B. Incorrect. You are making a conceptual error in analyzing the system.
C. Incorrect. You are making a conceptual error in analyzing the system.
D. Incorrect. You are making a conceptual error in analyzing the system.
E. Incorrect. There is enough information to solve the problem as it was stated—though you are correct that it isn’t a practical question.
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