BE SURE TO ANSWER. ATTEMPT ALL QUESTIONS

5-43C Consider an adiabatic turbine operating steadily. Does the work output of the turbine have to be equal to the decrease in the energy of the steam flowing through it? 5-44C Consider an air compressor operating steadily. How would you compare the volume flow rates of the air at the compressor inlet and exit? 5-45C Will the temperature of air rise as it is compressed by an adiabatic compressor? Why? 5-46C Somebody proposes the following system to cool a house in the summer: Compress the regular outdoor air, let it cool back to the outdoor temperature, pass it through a turbine, and discharge the cold air leaving the turbine into the house. From a thermodynamic point of view, is the proposed system sound? 5-47 Refrigerant-134a enters a compressor at 100 kPa and -24C with a flow rate of 1.35 and leaves at 800 kPa and 60C. Determine the mass flow rate of R-134a and the power input to the compressor.

24C with a flow rate of 1.35 and leaves at 800 kPa and 60C. Determine the mass flow rate of R-134a and the power input to the compressor. 5-48 Refrigerant-134a enters a compressor at 180 kPa as a saturated vapor with a flow rate of 0.35 m3/min and leaves at 700 kPa. The power supplied to the refrigerant during compression process is 2.35 kW. What is the temperature of R-134a at the exit of the compressor? Answer: 48.8C 5-49 Steam flows steadily through an adiabatic turbine. The inlet conditions of the steam are 6 MPa, 400C, and 80 m/s, and the exit conditions are 40 kPa, 92 percent quality, and 50 m/s. The mass flow rate of the steam is 20 kg/s. Determine (a ) the change in kinetic energy, (b) the power output, and (c) the turbine inlet area

5-37 Carbon dioxide enters an adiabatic nozzle steadily at I MPa and 500C with a mass flow rate of 6000 kg/h and leaves at 100 kPa and 450 m/s. The inlet area of the nozzle is 40 cm2. Determine (a ) the inlet velocity and (/;) the exit temperature. Answers: (a) 6 0 .8 m/s, (b) 6 8 5 .8 K 5-38 Refrigerant-134a at 700 kPa and 120C enters an adiabatic nozzle steadily with a velocity of 20 m/s and leaves at 400 kPa and 30C. Determine (a ) the exit velocity and (b ) the ratio of the inlet to exit area A ,M2. 5-39 Nitrogen gas at 60 kPa and 7C enters an adiabatic diffuser steadily with a velocity of 275 m/s and leaves at 85 kPa and 27C. Determine (a) the exit velocity of the nitrogen and (b) the ratio of the inlet to exit area

5-39. software, investigate the effect of the inlet velocity on the exit velocity and the ratio of the inlet-to-exit area. Let the inlet velocity vary from 210 to 350 m/s. Plot the final results against the inlet velocity, and discuss the results. 5-41 Refrigerant-134a enters a diffuser steadily as saturated vapor at 800 kPa with a velocity of 120 m/s, and it leaves at 900 kPa and 40C. The refrigerant is gaining heat at a rate of 2 kJ/s as it passes through the diffuser. If the exit area is 80 percent greater than the inlet area, determine (a) the exit velocity and (b) the mass flow rate of the refrigerant.

5-51 Steam enters an adiabatic turbine at 10 MPa and 500C and leaves at 10 kPa with a quality of 90 percent. Neglecting the changes in kinetic and potential energies, determine the mass flow rate required for a power output of 5 MW. Answer: 4 .8 5 2 kg/s 5-52E Steam flows steadily through a turbine at a rate of 45,000 , entering at 1000 psia and 900F and leaving at 5 psia as saturated vapor. If the power generated by the turbine is 4 MW, determine the rate of heat loss from the steam. 5-53 An adiabatic air compressor compresses 10 L/s of air at 120 kPa and 20C to 1000 kPa and 300C. Determine (a) the work required by the compressor, in kJ/kg, and (b) the power required to drive the air compressor, in kW

5-56 Carbon dioxide enters an adiabatic compressor at 100 kPa and 300 K at a rate of 0.5 kg/s and leaves at 600 kPa and 450 K. Neglecting kinetic energy changes, determine (a) the volume flow rate of the carbon dioxide at the compressor inlet and (b) the power input to the compressor. Answers: (a) 0 .2 8 m3/s, (b) 6 8 .8 kW 5-57 An adiabatic gas turbine expands air at 1300 kPa and 500C to 100 kPa and 127C. Air enters the turbine through a 0.2-m2 opening with an average velocity of 40 m/s, and exhausts through a 1-m2 opening. Determine (a) the mass flow rate of air through the turbine and (b) the power produced by the turbine.

5-58E Air is expanded by an adiabatic gas turbine from 500 psia and 800F to 60 psia and 250F. If the volume flow rate at the exit is 50 ft3/s; the inlet area is 0.6 ft2; and the outlet area is 1.2 ft2; determine the power produced by this turbine. 5-59 Steam enters a steady-flow turbine with a mass flow rate of 20 kg/s at 600C, 5 MPa, and a negligible velocity. The steam expands in the turbine to a saturated vapor at 500 kPa where 10 percent of the steam is removed for some other use. The remainder of the steam continues to expand to the turbine exit where the pressure is 10 kPa and quality is 85 percent. If the turbine is adiabatic, determine the rate of work done by the steam during this process

5-61 Determine the power input for a compressor that compresses helium from 150 kPa and 20C to 400 kPa and 200C. Helium enters this compressor through a 0.1 -m2 pipe at a velocity of 15 m/s. What is the increase in the flow power during this process? Throttling Valves 5-62C Someone claims, based on temperature measurements, that the temperature of a fluid rises during a throttling process in a well-insulated valve with negligible friction. How do you evaluate this claim? Does this process violate any thermodynamic laws? 5-63C Would you expect the temperature of air to drop as it undergoes a steady-flow throttling process? Explain. 5-64C Would you expect the temperature of a liquid to change as it is throttled? Explain. 5-65C During a throttling process, the temperature of a fluid drops from 30 to 20C. Can this process occur adiabatically? 5-66 An adiabatic capillary tube is used in some refrigeration systems to drop the pressure of the refrigerant from the condenser level to the evaporator level. The R-134a enters the capillary tube as a saturated liquid at 50C, and leaves at 20C. Determine the quality of the refrigerant at the inlet of the evaporator.

Refrigerant-134a at 800 kPa and 25C is tied to a temperature of 20C. Determine the pressure and the internal energy of the refrigerant at the final state. Answers: 133 kPa, 8 0 .7 kJ/kg 5-69 A well-insulated valve is used to throttle steam from 8 MPa and 350C to 2 MPa. Determine the final temperature of the steam. Answer: 285C 5-70 Reconsider Prob. 5-69. Using EES (or other) software, investigate the effect of the exit pressure of steam on the exit temperature after throttling. Let the exit pressure vary from 6 to 1 MPa. Plot the exit temperature of steam against the exit pressure, and discuss the results. 5-71E Refrigerant-134a enters the expansion valve of a refrigeration system at 160 psia as a saturated liquid and leaves at 30 psia. Determine the temperature and internal energy changes across the valve

5-72C Consider a steady-flow mixing process. Under what conditions will the energy transported into the control volume by the incoming streams be equal to the energy transported out of it by the outgoing stream? 5-73C Consider a steady-flow heat exchanger involving two different fluid streams. Under what conditions will the amount of heat lost by one fluid be equal to the amount of heat gained by the other? 5-74C When two fluid streams are mixed in a mixing chamber, can the mixture temperature be lower than the temperature of both streams? Explain. 5-75 Hot and cold streams of a fluid are mixed in a rigid mixing chamber. The hot fluid flows into the chamber at a mass flow rate of 5 kg/s with an energy in the amount of 150 kJ/kg. The cold fluid flows into the chamber with a mass flow rate of 15 kg/s and carries energy in the amount of 50 kJ/kg

5-77E Water at 65F and 20 psia is heated in a chamber by mixing it with saturated water vapor at 20 psia. If both streams enter the mixing chamber at the same mass flow rate, determine the temperature and the quality of the exiting stream. Answers: 228F, 0 .4 1 5 5-78 A stream of refrigerant-134a at 1 MPa and 20C is mixed with another stream at 1 MPa and 80C. If the mass flow rate of the cold stream is twice that of the hot one, determine the temperature and the quality of the exit stream. 5-79 r ^ | Reconsider Prob. 5-78. Using EES (or other) r ^ t i software, investigate the effect of the mass flow rate of the cold stream of R-134a on the temperature and the quality of the exit stream. Let the ratio of the mass flow rate of the cold stream to that of the hot stream vary from 1 to 4. Plot the mixture temperature and quality against the cold-tohot mass flow rate ratio, and discuss the results

5-80E Steam is to be condensed on the shell side of a heat exchanger at 85 F. Cooling water enters the tubes at 60F at a rate of 138 and leaves at 73F. Assuming the heat exchanger to be well-insulated, determine the rate of heat transfer in the heat exchanger and the rate of condensation of the steam. 5-81 Steam enters the condenser of a steam power plant at 20 kPa and a quality of 95 percent with a mass flow rate of 20,000 kg/h. It is to be cooled by water from a nearby river by circulating the water through the tubes within the condenser. To prevent thermal pollution, the river water is not allowed to experience a temperature rise above 10C. If the steam is to leave the condenser as saturated liquid at 20 kPa, determine the mass flow rate of the cooling water required

A heat exchanger is to cool ethylene glycol (cp = 2.56 kJ/kg C) flowing at a rate of 3.2 kg/s from 80C to 40C by water (cp = 4.18 kJ/kg C) that enters at 20C and leaves at 70C. Determine (a) the rate of heat transfer and (b) the mass flow rate of water. 5-83 r g j Reconsider Prob. 5-82. Using EES (or other) K i s software, investigate the effect of the inlet temperature of cooling water on the mass flow rate of water. Let the inlet temperature vary from 10 to 40C, and assume the exit temperature to remain constant. Plot the mass flow rate of water against the inlet temperature, and discuss the results. 5_84 A thin-walled double-pipe counter-flow heat exchanger is used to cool oil (cp = 2.20 kJ/kg-C) from 150 to 40C at a rate of 2 kg/s by water (cp = 4.18 kJ/kg-C) that enters at 22C at a rate of 1.5 kg/s. Determine the rate of heat transfer in the heat exchanger and the exit temperature of water.

Cold water (cp = 4.18 kJ/kg-C) leading to a shower enters a thin-walled double-pipe counter-flow heat exchanger at 15C at a rate of 0.60 kg/s and is heated to 45C by hot water (cp = 4.19 kJ/kg-C) that enters at 100C at a rate of 3 kg/s. Determine the rate of heat transfer in the heat exchanger and the exit temperature of the hot water. 5-86 Air (cp = 1.005 kJ/kg C) is to be preheated by hot exhaust gases in a cross-flow heat exchanger before it enters the furnace. Air enters the heat exchanger at 95 kPa and 20C at a rate of 0.6 m3/s. The combustion gases (cp = 1.10 kJ/kg C) enter at I60C at a rate of 0.95 kg/s and leave at 95C. Determine the rate of heat transfer to the air and its outlet temperature.

5-90 Hot exhaust gases of an internal combustion engine are to be used to produce saturated water vapor at 2 MPa pressure. The exhaust gases enter the heat exchanger at 400C at a rate of 32 kg/min while water enters at 15C. The heat exchanger is not well insulated, and it is estimated that 10 percent of heat given up by the exhaust gases is lost to the surroundings. If the mass flow rate of the exhaust gases is 15 times that of the water, determine (a) the temperature of the exhaust gases at the heat exchanger exit and (b) the rate of heat transfer to the water. Use the constant specific heat properties of air for the exhaust gases.

5-87E An open feedwater heater heats the feedwater by mixing it with hot steam. Consider an electrical power plant with an open feedwater heater that mixes 0.1 lbm/s of steam at 10 psia and 200F with 2.0 lbm/s of feedwater at 10 psia and 100F to produce 10 psia and 120F feedwater at the outlet. The diameter of the outlet pipe is 0.5 ft. Determine the mass flow rate and feedwater velocity at the outlet. Would the outlet flow rate and velocity be significantly different if the temperature at the outlet were 180F? 5-88E . ]. In a steam heating system, air is heated by over some tubes through which steam flows steadily. Steam enters the heat exchanger at 30 psia and 400F at a rate of 15 lbm/min and leaves at 25 psia and 212F. Air enters at 14.7 psia and 80F and leaves at 130F. Determine the volume flow rate of air at the inlet. 5-89 An air-conditioning system

the volume flow rate of air at the inlet. 5-89 An air-conditioning system involves the mixing of cold air and warm outdoor air before the mixture is routed to the conditioned room in steady operation. Cold air enters the mixing chamber at 7C and 105 kPa at a rate of 0.75 m3/s while warm air enters at 34C and 105 kPa. The air leaves the room at 24C. The ratio of the mass flow rates of the hot to cold air streams is 2.2. Using variable specific heats, determine (a) the mixture temperature at the inlet of the room and (b) the rate of heat gain of the room

5 -9 2 The condenser of a refrigeration cycle is basically a heat exchanger in which a refrigerant is condensed by rejecting heat to a cooling fluid. Refrigerant-134a enters a condenser at 1200 kPa and 85C with a flow rate of 0.042 kg/s and leaves at the same pressure subcooled by 6.3C. The condensation is done by cooling water which experiences a temperature rise of 12C in the condenser. Determine (a) the rate of heat transferred to the water in the condenser, in kJ/min and (b) the mass flow rate of water, in kg/min. Answers: (a) 5 2 5 kJ/m in, (b) 10.5 kg/min 5-93 The evaporator of a refrigeration cycle is basically a heat exchanger in which a refrigerant is evaporated by absorbing heat from a fluid. Refrigerant-22 enters an evaporator at 200 kPa with a quality of 22 percent and a flow rate of 2.25 L/h. R-22 leaves the evaporator at the same pressure superheated by 5C. The refrigerant is evaporated by absorbing heat from air whose flow rate is 0.5 kg/s. Determine (a) the rate of heat absorbed from the air and (b) the temperature change of air. The properties of R-22 at the inlet and exit of the condenser are h\ = 220.2 kJ/kg, v/, = 0.0253 , and h2 = 398.0 kJ/kg.

5-98 A 110-volt electrical heater is used to warm 0.3 m3/s of air at 100 kPa and 15C to 100 kPa and 30C. How much current in amperes must be supplied to this heater? 5-99E The fan on a personal computer draws 0.5 ft3/s of air at 14.7 psia and 70F through the box containing the CPU and other components. Air leaves at 14.7 psia and 80F. Calculate the electrical power, in kW, dissipated by the PC components

5-93 The evaporator of a refrigeration cycle is basically a heat exchanger in which a refrigerant is evaporated by absorbing heat from a fluid. Refrigerant-22 enters an evaporator at 200 kPa with a quality of 22 percent and a flow rate of 2.25 L/h. R-22 leaves the evaporator at the same pressure superheated by 5C. The refrigerant is evaporated by absorbing heat from air whose flow rate is 0.5 kg/s. Determine (a) the rate of heat absorbed from the air and (b) the temperature change of air. The properties of R-22 at the inlet and exit of the condenser are h\ = 220.2 kJ/kg, v/, = 0.0253 mTkg, and h2 = 398.0 kJ/kg. 5-94 Two mass streams of the same ideal gas are mixed in a steady-flow chamber while receiving energy by heat transfer from the surroundings. The mixing process takes place at constant pressure with no work and negligible changes in kinetic and potential energies. Assume the gas has constant specific heats. (a) Determine the expression for the final temperature of the mixture in terms of the rate of heat transfer to the mixing chamber and the inlet and exit mass flow rates. (b) Obtain an expression for the volume flow rate at the exit of the mixing chamber in terms of the volume flow rates of the two inlet streams and the rate of heat transfer to the mixing chamber. (c) For the special case of adiabatic mixing, show that the exit volume flow rate is the sum of the two inlet volume flow rates.

September 3,000,000 800,000 October 2,500,000 1,100,000 November 2,500,000 1,500,000 December 1,500,000 1,800,000 The indemnity period according to the policy was 4 months. Sh.200,000 was spent on putting the fire out and additional expenses as a consequence of the fire were Sh160,280 but a saving of Sh.30,000 was affected. Towards the end of 1997, a machine was installed which has resulted in a net saving equal to 2% of sales. Required: Prepare a detailed schedule to ascertain the claim for loss of profit (20 marks) (CPA adapted)