# Heat Engine and Mass Flow Rate

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• Published : June 2, 2012

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MAE219ReviewProf. 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 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. 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...