Chapter 12, Problem 88P

2nd Law of Thermodynamics A 1.5-ft3 rigid tank contains saturated refrigerant-134 at 170 psia. Initially, 20 percent of the volume isoccupied by liquid and the rest by vapor. A valve at the top of the tank is now opened, and vapor is allowedto escape slowly from the tank. Heat is transferred to the refrigerant such that the pressure inside the tankremains constant. The valve is closed when the last drop of liquid in the tank is vaporized. Determine thetotal heat transfer for this process.

Draw the shear and bending-moment diagrams for the beam and loading shown, and determine the maximum normal stress due to bending. 4.8 kips/ft 32 kips B C D E I Hinge 8 ft. 2 ft 5 ft 5 ft W12 x 40

2nd Law of Thermodynamics  A rigid, insulated tank that is initially evacuated is connected through a valve to the supply line that carrieshelium at 300 kPa and 140◦C. Now the valve is opened, and helium is allowed to flow into the tank until thepressure reaches 300 kPa, at which point the valve is closed. Determine the flow work of the helium in thesupply line and the final temperature of the helium in the tank.

Draw the shear and bending-moment diagrams for the beam and loading shown, and determine the maximum normal stress due to bending. 5 kips 10 kips B I W14 x 22 -5 ft -8 ft 5 ft-

2nd Law of Thermodynamics Liquid water at 200 kPa and 25◦C is heated in a chamber by mixing it with superheated steam at 200 kPaand 250◦C. cold water enters the chamber at a rate of 2 kg/s. If the mixture leaves the mixing chamber at50◦C, determine the mass flow rate of the superheated steam required.

The 2nd Law of Thermodynamics Refrigerant-134a enters the compressor of a refrigeration system as saturated vapor at 0.16 MPa, and leavesas superheated vapor at 0.9 MPa and 70◦C at a rate of 0.08 kg/s. Determine the rates of energy transfers bymass into and out of the compressor. Assume the kinetic and potential energies are negligible.

2nd Law of Thermodynamics  Water enters the tubes of a cold plate at 65◦C with an average velocity of 50 ft/min and leaves at 110◦F. Thediameter of the tubes is 0.2 in. Assuming 20 percent of the heat generated is dissipated from the componentsto the surroundings by convection and radiation, and the remaining 80 percent is removed by the coolingwater, determine the amount of heat generated by the electronic devices mounted on the cold plate.

The 2nd Law of Thermodynamics  Refrigerant-134a enters a diffuser steadily as saturated vapor 500 kPa with a velocity of 170 m/s, and it leavesat 600 kPa and 50◦C. the refrigerant is gaining heat at a rate of 2.5 kJ/s as it passes through the diffuser. Ifthe exit area is 75 percent greater than the inlet area, determine (a) the exit velocity  (b) the mass flow rate of the refrigerant.

2nd Law of Thermodynamics  Refrigerant-134a is throttled from the saturated liquid state at 850 kPa to a pressure of 200 kPa. Determinethe temperature drop during this process and the final specific volume of the refrigerant.