Mae219 Unit 9 Study Guide
MAE219 Review Prof. Y. Ngabonziza
1.
The water in a tank is pressurized by air, and the pressure is measured by a multifluid manometer as shown in Figure 1. Determine the gage pressure of air in the tank if h1=0.2m, h2=0.3m, and h3=0.46m. Take the densities of mercury, water, and oil are given to be 13,600, 1000, and 850 kg/m3, respectively.
2.
A piston cylinder device initially contains 0.07m3 of nitrogen gas at 130KPa and 120oC. The nitrogen is now expanded polytropically to a state of 100KPa and 100oC. Determine the boundary work done during this process.
3.
A refrigerator operates on the ideal vapor compression refrigeration cycle with R-134a as the working fluid between the pressure limits of …show more content…
120 kPa and 800 kPa. If the rate of heat removal from the refrigerated space is 38 kJ/s, calculate the mass flow rate of the refrigerant.
4.
Consider an ideal gas refrigeration cycle using helium as the working fluid. Helium enters the compressor at 100 kPa and –20°C and is compressed to 220 kPa. Helium is then cooled to 20°C before it enters the turbine. For a mass flow rate of 0.22 kg/s, calculate the net power input required.
5.
Steam expands in a turbine from 6 MPa and 500(C to 0.2 MPa and 150(C at a rate of 1.2 kg/s. Heat is lost from the turbine at a rate of 34 kJ/s during the process. Find the power output of the turbine.
6.
An Otto cycle with air as the working fluid has a compression ratio of 8.2. Under cold air standard conditions, find the thermal efficiency of this cycle. …show more content…
7.
A simple ideal Rankine cycle operates between the pressure limits of 20 kPa and 3 MPa, with a turbine inlet temperature of 500(C. Disregarding the pump work, find the cycle efficiency.
8.
Helium gas in an ideal Otto cycle is compressed from 12(C and 2 L to 0.25 L, and its temperature increases by an additional 800(C during the heat addition process. Calculate the temperature of helium before the expansion process.
9.
Air in an ideal Diesel cycle is compressed from 4 L to 0.25 L, and then it expands during the constant pressure heat addition process to 0.50 L. Under cold air standard conditions, determine the thermal efficiency of this cycle.
9.
A Carnot heat engine receives heat at 800K and rejects the waste heat to the environment at 300K. The entire work output of the heat engine is used to drive a Carnot refrigerator that removes heat from the cooled space at -15oC at a rate of 400KJ/min and rejects it to the same environment at 300K. Determine: (a) the rate of heat supplied to the heat engine (b) the total rate of heat rejection to the environment
10.
A 20 kg of aluminum block initially at 80oC is dropped into an insulated tank that contains 120 liters of water at 25oC. Determine the final equilibrium temperature and the total entropy change for this process.
11.
A heat pump is to be used to heat a building during the winter. The building is to be maintained at 21oC at all times. The building is estimated to be losing heat at a rate of 135,000 kJ/h when the outside temperature drops to -5oC. Determine the minimum power required to drive the heat pump unit for this outside
temperature.
12.
Air enters an evaporative cooler at 1 atm, 36oC, and 20 percent relative humidity at a rate of 4 m3/min, and it leaves with a relative humidity of 90 percent. Determine a) The exit temperature of the air b) The required rate of water supply to the evaporative cooler
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Figure 1
1.
The water in a tank is pressurized by air, and the pressure is measured by a multifluid manometer as shown in Figure 1. Determine the gage pressure of air in the tank if h1=0.2m, h2=0.3m, and h3=0.46m. Take the densities of mercury, water, and oil are given to be 13,600, 1000, and 850 kg/m3, respectively.
2.
A piston cylinder device initially contains 0.07m3 of nitrogen gas at 130KPa and 120oC. The nitrogen is now expanded polytropically to a state of 100KPa and 100oC. Determine the boundary work done during this process.
3.
A refrigerator operates on the ideal vapor compression refrigeration cycle with R-134a as the working fluid between the pressure limits of …show more content…
120 kPa and 800 kPa. If the rate of heat removal from the refrigerated space is 38 kJ/s, calculate the mass flow rate of the refrigerant.
4.
Consider an ideal gas refrigeration cycle using helium as the working fluid. Helium enters the compressor at 100 kPa and –20°C and is compressed to 220 kPa. Helium is then cooled to 20°C before it enters the turbine. For a mass flow rate of 0.22 kg/s, calculate the net power input required.
5.
Steam expands in a turbine from 6 MPa and 500(C to 0.2 MPa and 150(C at a rate of 1.2 kg/s. Heat is lost from the turbine at a rate of 34 kJ/s during the process. Find the power output of the turbine.
6.
An Otto cycle with air as the working fluid has a compression ratio of 8.2. Under cold air standard conditions, find the thermal efficiency of this cycle. …show more content…
7.
A simple ideal Rankine cycle operates between the pressure limits of 20 kPa and 3 MPa, with a turbine inlet temperature of 500(C. Disregarding the pump work, find the cycle efficiency.
8.
Helium gas in an ideal Otto cycle is compressed from 12(C and 2 L to 0.25 L, and its temperature increases by an additional 800(C during the heat addition process. Calculate the temperature of helium before the expansion process.
9.
Air in an ideal Diesel cycle is compressed from 4 L to 0.25 L, and then it expands during the constant pressure heat addition process to 0.50 L. Under cold air standard conditions, determine the thermal efficiency of this cycle.
9.
A Carnot heat engine receives heat at 800K and rejects the waste heat to the environment at 300K. The entire work output of the heat engine is used to drive a Carnot refrigerator that removes heat from the cooled space at -15oC at a rate of 400KJ/min and rejects it to the same environment at 300K. Determine: (a) the rate of heat supplied to the heat engine (b) the total rate of heat rejection to the environment
10.
A 20 kg of aluminum block initially at 80oC is dropped into an insulated tank that contains 120 liters of water at 25oC. Determine the final equilibrium temperature and the total entropy change for this process.
11.
A heat pump is to be used to heat a building during the winter. The building is to be maintained at 21oC at all times. The building is estimated to be losing heat at a rate of 135,000 kJ/h when the outside temperature drops to -5oC. Determine the minimum power required to drive the heat pump unit for this outside
temperature.
12.
Air enters an evaporative cooler at 1 atm, 36oC, and 20 percent relative humidity at a rate of 4 m3/min, and it leaves with a relative humidity of 90 percent. Determine a) The exit temperature of the air b) The required rate of water supply to the evaporative cooler
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Figure 1