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The power plant in Problem 9.16 has too low a quality. What should the superheat for the reheat be so that the turbine quality stays above 92%?
Consider an ideal Rankine cycle using water with a high-pressure side of the cycle at a supercritical pressure. What is the steam quality at the turbine exit?
Find the temperature out of the boiler/super heater so that the turbine exit temperature is 60oC, and find the overall cycle efficiency.
For a turbine power output of 8 MW, find the work and heat transfer in all components and the cycle efficiency.
A Rankine cycle with R-410a has the boiler at 3 MPa superheating to 180oC, and the condenser operates. Find all four energy transfers and the cycle efficiency.
Find the plant efficiency and the efficiency of a Carnot cycle with the same temperatures.
A heat pump uses carbon dioxide, and it must condense at a minimum of 22oC and receives energy. What restrictions does that place on the operating pressures?
A refrigerator in my 20oC kitchen uses R-134a, and I want to make ice cubes at -5oC. What is the minimum high P and the maximum low P it can use?
What is the difference between an open and a closed FWH? In a cogenerating power plant, what is cogenerated?
Find from the literature the amount of energy that must be stored in a car to start the engine. Discuss the feasibility and cost.
The exit pressure is 10 psia and the actual exit temperature is 1780 R. What is the actual exit velocity and the second-law efficiency?
Use constant heat capacities and find the exit temperature and the second-law efficiency for the heat exchanger, assuming ambient at 68 F.
A heat exchanger increases the exergy of 3 kg/s water by 1650 kJ/kg using 10 kg/s air coming. What are the irreversibility and the second-law efficiency?
A piston/cylinder has forces on the piston, so it maintains constant pressure. Find the work out of the heat engine using the exergy balance equation.
Air in a piston/cylinder arrangement is at 110 kPa, 25oC. Find the total work (including that of the external device) and the heat transfer from the ambient.
The intercooler in the previous problem uses cold liquid water to cool nitrogen. Find the flow rate of the water and the exergy destruction in this intercooler.
Find the exergy at the initial and final states and the destruction of exergy in the process.
A turbine receives steam at 3000 kPa, 500oC and has two exit flows, one at 1000 kPa 350oC with 20% of the flow. Find the isentropic and second-law efficiencies.
Find the second-law efficiency for the compressed air system in Problem 8.65. Consider the total system from the inlet to the final point of use.
A compressor in a refrigerator receives R-410a at 20 psia, -40 F and it brings it up to 100 psia, using actual specific work. Find the specific reversible work.
Find the heat transfer out of the R-134a, the extra work input to the refrigerator due to this process and total irreversibility including that of refrigerator.
A heat exchanger increases the exergy of 6 lbm/s water by 800 Btu/lbm using 20 lbm/s air. What are the irreversibility and the second law efficiency?
The air inlet to compressor is at 14.7 lbf/in.2, 60 F and compressor isentropic efficiency is 80%. Find total compressor work and change in exergy of the air.
For the air system in the previous problem, find increase in air exergy from inlet to the point of use. How much exergy was lost in flow after compressor exit?
A constant-pressure piston/cylinder has 1 kg of saturated liquid water at 100 kPa. Find the required amount of air and the work out of the heat engine.