problems 10-Nitrogen, modeled as an ideal gas

Problem 4.024 SI

Nitrogen, modeled as an ideal gas, flows at a rate of 3 kg/s through a well-insulated horizontal nozzle operating at steady state. The nitrogen enters the nozzle with a velocity of 20 m/s at 400 K, 400 kPa and exits the nozzle at 100 kPa.


To achieve an exit velocity of 500 m/s, determine:

(a) the exit temperature, in K.

(b) the exit area, in m2.

 

Problem 4.026

Air enters a diffuser operating at steady state at 750°R, 15 lbf/in.2, with a velocity of 600 ft/s, and exits with a velocity of 60 ft/s. The ratio of the exit area to the inlet area is 10. 

Assuming the ideal gas model for the air and ignoring heat transfer, determine the temperature, in °R, and pressure, in lbf/in.2, at the exit.

 

Problem 4.028 SI

Steam enters a well-insulated turbine operating at steady state at 4 MPa with a specific enthalpy of 3015.4 kJ/kg and a velocity of 10 m/s. The steam expands to the turbine exit where the pressure is 0.07 MPa, specific enthalpy is 2300 kJ/kg, and the velocity is 90 m/s. The mass flow rate is 4 kg/s.

Neglecting potential energy effects, determine the power developed by the turbine, in kW.

W?cv=  kW

 

Problem 4.040 SI

Refrigerant 134a enters an air conditioner compressor at 4 bar, 20°C, and is compressed at steady state to 12 bar, 80°C. The volumetric flow rate of the refrigerant entering is 6.5 m3/min. The work input to the compressor is 97.5 kJ per kg of refrigerant flowing. 


Neglecting kinetic and potential energy effects, determine the magnitude of the heat transfer rate from the compressor, in kW.
 

Q?cv=  kW

 

Problem 4.049

A pump is used to circulate hot water in a home heating system. Water enters the well-insulated pump operating at steady state at a rate of 0.42 gal/min. The inlet pressure and temperature are 14.7 lbf/in.2, and 180°F, respectively; at the exit the pressure is 90 lbf/in.2 The pump requires 1/15 hp of power input. Water can be modeled as an incompressible substance with constant density of 60.58 lb/ft3 and constant specific heat of 1 Btu/lb · °R. 


Neglecting kinetic and potential energy effects, determine the temperature change, in °R, as the water flows through the pump.

ΔT=  °R

the tolerance is +/-2%

 

Problem 4.053 SI

Steam at a pressure of 0.08 bar and a quality of 99.0% enters a shell-and-tube heat exchanger where it condenses on the outside of tubes through which cooling water flows, exiting as saturated liquid at 0.08 bar. The mass flow rate of the condensing steam is 3.4 x 105 kg/h. Cooling water enters the tubes at 15°C and exits at 35°C with negligible change in pressure. 


Neglecting stray heat transfer and ignoring kinetic and potential energy effects, determine the mass flow rate of the cooling water, in kg/h, for steady-state operation.

m?water=  kg/h

 

Problem 4.060 SI

Three return steam lines in a chemical processing plant enter a collection tank operating at steady state at 1 bar. Steam enters inlet 1 with flow rate of 1.4 kg/s and quality of 0.9. Steam enters inlet 2 with flow rate of 2 kg/s at 200°C. Steam enters inlet 3 with flow rate of 1.2 kg/s at 95°C. Steam exits the tank at 1 bar. The rate of heat transfer from the collection tank is 40 kW. 


Neglecting kinetic and potential energy effects, determine for the steam exiting the tank:

(a) the mass flow rate, in kg/s.

(b) the temperature, in °C.

 

Problem 4.079 SI

A rigid tank whose volume is 4 m3, initially containing air at 1 bar, 295 K, is connected by a valve to a large vessel holding air at 6 bar, 295 K. The valve is opened only as long as required to fill the tank with air to a pressure of 6 bar and a temperature of 320 K. 


Assuming the ideal gas model for the air, determine the heat transfer between the tank contents and the surroundings, in kJ.

Qcv=  kJ

 

Problem 4.014 SI

The figure below provides steady-state data for water vapor flowing through a piping configuration where V1 = 5 m/s and T1 = 520°C. At each exit, the volumetric flow rate, pressure, and temperature are equal.

 

Determine the mass flow rate at the inlet and exits, each in kg/s.

 

m?1=	kg/s
m?2=	kg/s
m?3=	kg/s

 

4.007 SI Ammonia enters the expansion valve of a refrigeration system at a pressure of 10 bar and a temperature of 22oC and exits at 5.0 bar. The refrigerant undergoes a throttling process.   Determine the temperature, in oC, and the quality of the refrigerant at the exit of the expansion valve.