Thermodynamics: An Engineering Approach
8th Edition
ISBN: 9780073398174
Author: Yunus A. Cengel Dr., Michael A. Boles
Publisher: McGraw-Hill Education
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Textbook Question
Chapter 5.5, Problem 90P
A 110-volt electrical heater is used to warm 0.3 m3/s of air at 100 kPa and 15°C to 100 kPa and 30°C. How much current in amperes must be supplied to this heater?
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Chapter 5 Solutions
Thermodynamics: An Engineering Approach
Ch. 5.5 - Prob. 1PCh. 5.5 - Define mass and volume flow rates. How are they...Ch. 5.5 - Does the amount of mass entering a control volume...Ch. 5.5 - Consider a device with one inlet and one outlet....Ch. 5.5 - The ventilating fan of the bathroom of a building...Ch. 5.5 - 5–6E Air whose density is 0.078 lbm/ft3 enters the...Ch. 5.5 - 5–7 Air enters a 28-cm diameter pipe steadily at...Ch. 5.5 - A steady-flow compressor is used to compress...Ch. 5.5 - A 2-m3 rigid tank initially contains air whose...Ch. 5.5 - 5–10 A cyclone separator like that in Fig. P5–10...
Ch. 5.5 - 5–11 A spherical hot-air balloon is initially...Ch. 5.5 - A desktop computer is to be cooled by a fan whose...Ch. 5.5 - 5–13 A pump increases the water pressure from 100...Ch. 5.5 - Refrigerant-134a enters a 28-cm-diameter pipe...Ch. 5.5 - Prob. 15PCh. 5.5 - Prob. 16PCh. 5.5 - 5–17C What is flow energy? Do fluids at rest...Ch. 5.5 - How do the energies of a flowing fluid and a fluid...Ch. 5.5 - Prob. 19PCh. 5.5 - Prob. 20PCh. 5.5 - Refrigerant-134a enters the compressor of a...Ch. 5.5 - Steam is leaving a pressure cooker whose operating...Ch. 5.5 - A diffuser is an adiabatic device that decreases...Ch. 5.5 - The kinetic energy of a fluid increases as it is...Ch. 5.5 - Prob. 25PCh. 5.5 - Air enters a nozzle steadily at 50 psia, 140F, and...Ch. 5.5 - The stators in a gas turbine are designed to...Ch. 5.5 - The diffuser in a jet engine is designed to...Ch. 5.5 - Air at 600 kPa and 500 K enters an adiabatic...Ch. 5.5 - Prob. 30PCh. 5.5 - Prob. 31PCh. 5.5 - Air at 13 psia and 65F enters an adiabatic...Ch. 5.5 - Carbon dioxide enters an adiabatic nozzle steadily...Ch. 5.5 - Refrigerant-134a at 700 kPa and 120C enters an...Ch. 5.5 - Prob. 35PCh. 5.5 - Refrigerant-134a enters a diffuser steadily as...Ch. 5.5 - Prob. 38PCh. 5.5 - Air at 80 kPa, 27C, and 220 m/s enters a diffuser...Ch. 5.5 - 5–40C Consider an air compressor operating...Ch. 5.5 - Prob. 41PCh. 5.5 - Somebody proposes the following system to cool a...Ch. 5.5 - 5–43E Air flows steadily through an adiabatic...Ch. 5.5 - Prob. 44PCh. 5.5 - Prob. 45PCh. 5.5 - Steam flows steadily through an adiabatic turbine....Ch. 5.5 - Prob. 48PCh. 5.5 - Steam flows steadily through a turbine at a rate...Ch. 5.5 - Prob. 50PCh. 5.5 - Carbon dioxide enters an adiabatic compressor at...Ch. 5.5 - Prob. 52PCh. 5.5 - 5–54 An adiabatic gas turbine expands air at 1300...Ch. 5.5 - Prob. 55PCh. 5.5 - Prob. 56PCh. 5.5 - Air enters the compressor of a gas-turbine plant...Ch. 5.5 - Why are throttling devices commonly used in...Ch. 5.5 - Would you expect the temperature of air to drop as...Ch. 5.5 - Prob. 60PCh. 5.5 - During a throttling process, the temperature of a...Ch. 5.5 - Refrigerant-134a is throttled from the saturated...Ch. 5.5 - A saturated liquidvapor mixture of water, called...Ch. 5.5 - Prob. 64PCh. 5.5 - A well-insulated valve is used to throttle steam...Ch. 5.5 - Refrigerant-134a enters the expansion valve of a...Ch. 5.5 - Prob. 68PCh. 5.5 - Consider a steady-flow heat exchanger involving...Ch. 5.5 - Prob. 70PCh. 5.5 - Prob. 71PCh. 5.5 - Prob. 72PCh. 5.5 - Prob. 73PCh. 5.5 - Prob. 74PCh. 5.5 - Prob. 76PCh. 5.5 - Steam is to be condensed on the shell side of a...Ch. 5.5 - Prob. 78PCh. 5.5 - Air (cp = 1.005 kJ/kgC) is to be preheated by hot...Ch. 5.5 - Prob. 80PCh. 5.5 - Refrigerant-134a at 1 MPa and 90C is to be cooled...Ch. 5.5 - Prob. 82PCh. 5.5 - An air-conditioning system involves the mixing of...Ch. 5.5 - The evaporator of a refrigeration cycle is...Ch. 5.5 - Steam is to be condensed in the condenser of a...Ch. 5.5 - Steam is to be condensed in the condenser of a...Ch. 5.5 - Two mass streams of the same ideal gas are mixed...Ch. 5.5 - Prob. 89PCh. 5.5 - A 110-volt electrical heater is used to warm 0.3...Ch. 5.5 - The fan on a personal computer draws 0.3 ft3/s of...Ch. 5.5 - Prob. 92PCh. 5.5 - 5–93 A scaled electronic box is to be cooled by...Ch. 5.5 - Prob. 94PCh. 5.5 - Prob. 95PCh. 5.5 - Prob. 96PCh. 5.5 - Prob. 97PCh. 5.5 - A computer cooled by a fan contains eight PCBs,...Ch. 5.5 - Prob. 99PCh. 5.5 - A long roll of 2-m-wide and 0.5-cm-thick 1-Mn...Ch. 5.5 - Prob. 101PCh. 5.5 - Prob. 102PCh. 5.5 - A house has an electric heating system that...Ch. 5.5 - Steam enters a long, horizontal pipe with an inlet...Ch. 5.5 - Refrigerant-134a enters the condenser of a...Ch. 5.5 - Prob. 106PCh. 5.5 - Water is heated in an insulated, constant-diameter...Ch. 5.5 - Prob. 108PCh. 5.5 - Air enters the duct of an air-conditioning system...Ch. 5.5 - A rigid, insulated tank that is initially...Ch. 5.5 - 5–113 A rigid, insulated tank that is initially...Ch. 5.5 - Prob. 114PCh. 5.5 - A 0.2-m3 rigid tank equipped with a pressure...Ch. 5.5 - Prob. 116PCh. 5.5 - Prob. 117PCh. 5.5 - Prob. 118PCh. 5.5 - Prob. 119PCh. 5.5 - An air-conditioning system is to be filled from a...Ch. 5.5 - Oxygen is supplied to a medical facility from ten...Ch. 5.5 - Prob. 122PCh. 5.5 - A 0.3-m3 rigid tank is filled with saturated...Ch. 5.5 - Prob. 124PCh. 5.5 - Prob. 125PCh. 5.5 - Prob. 126PCh. 5.5 - The air-release flap on a hot-air balloon is used...Ch. 5.5 - An insulated 0.15-m3 tank contains helium at 3 MPa...Ch. 5.5 - An insulated 40-ft3 rigid tank contains air at 50...Ch. 5.5 - A vertical pistoncylinder device initially...Ch. 5.5 - A vertical piston-cylinder device initially...Ch. 5.5 - Prob. 135RPCh. 5.5 - Prob. 136RPCh. 5.5 - Air at 4.18 kg/m3 enters a nozzle that has an...Ch. 5.5 - An air compressor compresses 15 L/s of air at 120...Ch. 5.5 - 5–139 Saturated refrigerant-134a vapor at 34°C is...Ch. 5.5 - A steam turbine operates with 1.6 MPa and 350C...Ch. 5.5 - Prob. 141RPCh. 5.5 - Prob. 142RPCh. 5.5 - Prob. 143RPCh. 5.5 - Steam enters a nozzle with a low velocity at 150C...Ch. 5.5 - Prob. 146RPCh. 5.5 - Prob. 147RPCh. 5.5 - Prob. 148RPCh. 5.5 - Prob. 149RPCh. 5.5 - Cold water enters a steam generator at 20C and...Ch. 5.5 - Prob. 151RPCh. 5.5 - An ideal gas expands in an adiabatic turbine from...Ch. 5.5 - Prob. 153RPCh. 5.5 - Prob. 154RPCh. 5.5 - Prob. 155RPCh. 5.5 - Prob. 156RPCh. 5.5 - Prob. 157RPCh. 5.5 - Prob. 158RPCh. 5.5 - Prob. 159RPCh. 5.5 - Prob. 160RPCh. 5.5 - Prob. 161RPCh. 5.5 - Prob. 162RPCh. 5.5 - Prob. 163RPCh. 5.5 - The ventilating fan of the bathroom of a building...Ch. 5.5 - Determine the rate of sensible heat loss from a...Ch. 5.5 - An air-conditioning system requires airflow at the...Ch. 5.5 - The maximum flow rate of standard shower heads is...Ch. 5.5 - An adiabatic air compressor is to be powered by a...Ch. 5.5 - Prob. 171RPCh. 5.5 - Prob. 172RPCh. 5.5 - Prob. 173RPCh. 5.5 - Prob. 174RPCh. 5.5 - Prob. 175RPCh. 5.5 - A tank with an internal volume of 1 m3 contains...Ch. 5.5 - A liquid R-134a bottle has an internal volume of...Ch. 5.5 - Prob. 179RPCh. 5.5 - Prob. 181RPCh. 5.5 - Prob. 182RPCh. 5.5 - Prob. 184RPCh. 5.5 - A pistoncylinder device initially contains 1.2 kg...Ch. 5.5 - In a single-flash geothermal power plant,...Ch. 5.5 - The turbocharger of an internal combustion engine...Ch. 5.5 - A building with an internal volume of 400 m3 is to...Ch. 5.5 - Prob. 189RPCh. 5.5 - Prob. 190RPCh. 5.5 - Prob. 191RPCh. 5.5 - Prob. 192FEPCh. 5.5 - Prob. 193FEPCh. 5.5 - An adiabatic heat exchanger is used to heat cold...Ch. 5.5 - A heat exchanger is used to heat cold water at 15C...Ch. 5.5 - An adiabatic heat exchanger is used to heat cold...Ch. 5.5 - In a shower, cold water at 10C flowing at a rate...Ch. 5.5 - Prob. 198FEPCh. 5.5 - Hot combustion gases (assumed to have the...Ch. 5.5 - Steam expands in a turbine from 4 MPa and 500C to...Ch. 5.5 - Steam is compressed by an adiabatic compressor...Ch. 5.5 - Refrigerant-134a is compressed by a compressor...Ch. 5.5 - Prob. 203FEPCh. 5.5 - Prob. 204FEPCh. 5.5 - Air at 27C and 5 atm is throttled by a valve to 1...Ch. 5.5 - Steam at 1 MPa and 300C is throttled adiabatically...Ch. 5.5 - Air is to be heated steadily by an 8-kW electric...
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- 2 lbm of refrigerant-134a occupy a 3 ft^3 system at 50 psia. In what state is the refrigerant present?arrow_forwardAn air conditioner with refrigerant-134a as the refrigerant is used to keep a large space at 20°C by rejecting the waste heat to the outside air at 37 °C. The room is gaining heat through the walls and the windows at a rate of 125 kJ/min while the heat generated by the computer, TV, and lights amounts to 0.7 kW. Unknown amount of heat is also generated by the people in the room. The condenser and evaporator pressures are 1200 and 500 kPa, respectively. The refrigerant is saturated liguid at the condenser exit and saturated vapor at the compressor inlet. If the refrigerant enters the compressor at a rate of 65 L/min and the isentropic efficiency of the compressor is 70%, determine (a) the temperature of the refrigerant at the compressor exit, (b) the rate of heat generated by the people in the room, (c) the COP of the air conditioner, and (d) the minimum volume flow rate of the refrigerant at the compressor inlet for the same compressor inlet and exit conditions.arrow_forwardA steam power plant has a high pressure of 2.5 MPa after release from the pump and it maintains 40°C in the condenser. The quality of the stream exiting the turbine is 80%. Solve for the work produced by the turbine and the pump, the heat transfer in the boiler, and heat removed by the condenser. (Answer in kJ/kg)arrow_forward
- What is the status of Refrigerant-134a at 10°C and 1 MPa?arrow_forwardIt is common knowledge that the temperature rises as it is compressed. An inventor thought about using this high temperature air to heat buildings. He used a compressor driven by an electric motor. The inventor claims that the compressed hot air system is 25% more efficient than a resistance heating system that provides an equivalent amount of heating. Is this claim valid, or is this just another perpetual motion machine?arrow_forwardThe steam entering the turbine in a coal-burning power plant is heated to 500 celsius. The steam is cooled and condensed to water at 80 celsius. Use the formula in the footnotes of 7-2 in your book to find the ideal efficiency of the power plant. Remember that you must convert Celsius temperatures to Kelvin before using the formula. Show all your work below.arrow_forward
- A tank containing 200 kg of water was used as a constant temperature heat bath. How long would it take to heat the bath from 20°C to 25°C with a 250-W immersion heater? Neglect the heat capacity of the tank frane and any heat loss to the air. 3.2 hrs 3.7 hrs 4.6 hrs 4.9 hrs 5.8 hrsarrow_forwardDetermine the second law efficiency of the heat engine operating between 750 oC and 25 oC. The heat engine has efficiency of 40% .arrow_forwardA refrigeration system uses a water-cooled condenser for rejecting the waste heat. The system absorbs heat from a space at 25°F at a rate of 21,000 Btu/h. Water enters the condenser at 65°F at a rate of 1.45 lbm/s. The COP of the system is estimated to be 1.9. Determine the temperature of the water at the exit of the condenser in °F.arrow_forward
- Consider mixing some of the ice water with the hot water and vice versa so that the two reservoirs are closer to the same temperature. What do you think will happen to the mechanical/thermodynamic efficiency and ideal Carnot efficiency of the heat engine?arrow_forwardDetermine the rate of heat released (in kW) by the steam with 88.0% quality thatenters the evaporator at 1800 kg/h at 132C and exits as a subcooled liquid at 100C.Assume that the condensate outlet pressure is the same as the steam inlet pressure.The specific heat of liquid water is 4.187 kJ/kg-Carrow_forwardA steam plant. the pressure levels are 10 kPa and 6000 kPa, and the steam leaves the turbine as saturated vapor. The pump efficiency is 0.70 and the turbine 0.75. determine the thermal efficiency of the plantarrow_forward
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