Thermodynamics: An Engineering Approach
9th Edition
ISBN: 9781259822674
Author: Yunus A. Cengel Dr., Michael A. Boles
Publisher: McGraw-Hill Education
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Chapter 5.5, Problem 97P
A computer cooled by a fan contains eight PCBs, each dissipating 10 W power. The height of the PCBs is 12 cm and the length is 18 cm. The cooling air is supplied by a 25-W fan mounted at the inlet. If the temperature rise of air as it flows through the case of the computer is not to exceed 10°C, determine (a) the flow rate of the air that the fan needs to deliver and (b) the fraction of the temperature rise of air that is due to the heat generated by the fan and its motor.
FIGURE P5–97
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A fan-cooled computer contains eight printed circuit boards, each dissipating 10 W of power. The height of the cards is 12 cm and their length is 18 cm. Cooling air is supplied by a 25W fan mounted at the inlet. If the air temperature rise is not to be greater than 10 ° C as it passes through the computer case, determine (a) the air flow rate that the fan must deliver and (b) the fraction of the air temperature rise due to heat generated by the fan and its motor.
A device submitted to the Pa-
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Chapter 5 Solutions
Thermodynamics: An Engineering Approach
Ch. 5.5 - Name four physical quantities that are conserved...Ch. 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 - Air enters a 16-cm-diameter pipe steadily at 200...Ch. 5.5 - A steam pipe is to transport 200 lbm/s of steam at...Ch. 5.5 - A garden hose attached with a nozzle is used to...Ch. 5.5 - A steady-flow compressor is used to compress...Ch. 5.5 - Air enters the 1-m2 inlet of an aircraft engine at...
Ch. 5.5 - A 2-m3 rigid tank initially contains air whose...Ch. 5.5 - Air enters a nozzle steadily at 2.21 kg/m3 and 40...Ch. 5.5 - A spherical hot-air balloon is initially filled...Ch. 5.5 - Water enters the constant 130-mm inside-diameter...Ch. 5.5 - A desktop computer is to be cooled by a fan whose...Ch. 5.5 - A hair dryer is basically a duct of constant...Ch. 5.5 - Refrigerant-134a enters a 28-cm-diameter pipe...Ch. 5.5 - What are the different mechanisms for transferring...Ch. 5.5 - How do the energies of a flowing fluid and a fluid...Ch. 5.5 - An air compressor compresses 6 L of air at 120 kPa...Ch. 5.5 - A house is maintained at 1 atm and 24C, and warm...Ch. 5.5 - Refrigerant-134a enters the compressor of a...Ch. 5.5 - Steam is leaving a pressure cooker whose operating...Ch. 5.5 - How is a steady-flow system characterized?Ch. 5.5 - Can a steady-flow system involve boundary work?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 - 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 enters a nozzle steadily at 50 psia, 140F, and...Ch. 5.5 - Air at 600 kPa and 500 K enters an adiabatic...Ch. 5.5 - Carbon dioxide enters an adiabatic nozzle steadily...Ch. 5.5 - Steam enters a nozzle at 400C and 800 kPa with a...Ch. 5.5 - Air at 80 kPa and 127C enters an adiabatic...Ch. 5.5 - Air at 13 psia and 65F enters an adiabatic...Ch. 5.5 - Refrigerant-134a at 700 kPa and 120C enters an...Ch. 5.5 - Refrigerant-134a enters a diffuser steadily as...Ch. 5.5 - Air at 80 kPa, 27C, and 220 m/s enters a diffuser...Ch. 5.5 - Air enters an adiabatic nozzle steadily at 300...Ch. 5.5 - Consider an adiabatic turbine operating steadily....Ch. 5.5 - Prob. 42PCh. 5.5 - Somebody proposes the following system to cool a...Ch. 5.5 - Air is expanded from 1000 kPa and 600C at the...Ch. 5.5 - Prob. 45PCh. 5.5 - Refrigerant-134a enters a compressor at 100 kPa...Ch. 5.5 - Refrigerant-134a enters a compressor at 180 kPa as...Ch. 5.5 - Steam flows steadily through an adiabatic turbine....Ch. 5.5 - Steam flows steadily through a turbine at a rate...Ch. 5.5 - Steam enters an adiabatic turbine at 8 MPa and...Ch. 5.5 - An adiabatic air compressor compresses 10 L/s of...Ch. 5.5 - Carbon dioxide enters an adiabatic compressor at...Ch. 5.5 - Steam flows steadily into a turbine with a mass...Ch. 5.5 - Air is compressed by an adiabatic compressor from...Ch. 5.5 - Air enters the compressor of a gas-turbine plant...Ch. 5.5 - A portion of the steam passing through a steam...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 - During a throttling process, the temperature of a...Ch. 5.5 - Someone claims, based on temperature measurements,...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 - Prob. 69PCh. 5.5 - Consider a steady-flow heat exchanger involving...Ch. 5.5 - Prob. 71PCh. 5.5 - Refrigerant-134a at 700 kPa, 70C, and 8 kg/min is...Ch. 5.5 - Hot and cold streams of a fluid are mixed in a...Ch. 5.5 - A hot-water stream at 80C enters a mixing chamber...Ch. 5.5 - Water at 80F and 20 psia is heated in a chamber by...Ch. 5.5 - An adiabatic open feedwater heater in an electric...Ch. 5.5 - Cold water (cp = 4.18 kJ/kgC) leading to a shower...Ch. 5.5 - Steam is to be condensed on the shell side of a...Ch. 5.5 - Air (cp = 1.005 kJ/kgC) is to be preheated by hot...Ch. 5.5 - An open feedwater heater heats the feedwater by...Ch. 5.5 - Refrigerant-134a at 1 MPa and 90C is to be cooled...Ch. 5.5 - The evaporator of a refrigeration cycle is...Ch. 5.5 - An air-conditioning system involves the mixing of...Ch. 5.5 - A well-insulated shell-and-tube heat exchanger 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 streams of water are mixed in an insulated...Ch. 5.5 - Two mass streams of the same ideal gas are mixed...Ch. 5.5 - Water is heated in an insulated, constant-diameter...Ch. 5.5 - A 110-volt electrical heater is used to warm 0.3...Ch. 5.5 - The ducts of an air heating system pass through an...Ch. 5.5 - The fan on a personal computer draws 0.3 ft3/s of...Ch. 5.5 - Saturated liquid water is heated in a steady-flow...Ch. 5.5 - Water enters the tubes of a cold plate at 70F with...Ch. 5.5 - Prob. 96PCh. 5.5 - A computer cooled by a fan contains eight PCBs,...Ch. 5.5 - A desktop computer is to be cooled by a fan. The...Ch. 5.5 - Prob. 99PCh. 5.5 - A 4-m 5-m 6-m room is to be heated by an...Ch. 5.5 - A house has an electric heating system that...Ch. 5.5 - A long roll of 2-m-wide and 0.5-cm-thick 1-Mn...Ch. 5.5 - Prob. 103PCh. 5.5 - Prob. 104PCh. 5.5 - Argon steadily flows into a constant-pressure...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 - A hair dryer is basically a duct in which a few...Ch. 5.5 - A hair dryer is basically a duct in which a few...Ch. 5.5 - Air enters the duct of an air-conditioning system...Ch. 5.5 - An insulated rigid tank is initially evacuated. A...Ch. 5.5 - A rigid, insulated tank that is initially...Ch. 5.5 - Prob. 115PCh. 5.5 - A 2-m3 rigid tank initially contains air at 100...Ch. 5.5 - A 0.2-m3 rigid tank equipped with a pressure...Ch. 5.5 - Prob. 118PCh. 5.5 - An insulated 40-ft3 rigid tank contains air at 50...Ch. 5.5 - A 4-L pressure cooker has an operating pressure of...Ch. 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 - A 0.05-m3 rigid tank initially contains...Ch. 5.5 - A 0.12-m3 rigid tank contains saturated...Ch. 5.5 - A 0.3-m3 rigid tank is filled with saturated...Ch. 5.5 - The air-release flap on a hot-air balloon is used...Ch. 5.5 - Prob. 127PCh. 5.5 - An insulated 0.15-m3 tank contains helium at 3 MPa...Ch. 5.5 - A vertical pistoncylinder device initially...Ch. 5.5 - A vertical piston-cylinder device initially...Ch. 5.5 - A pistoncylinder device initially contains 0.6 kg...Ch. 5.5 - The weighted piston of the device shown in Fig....Ch. 5.5 - Prob. 136RPCh. 5.5 - Prob. 137RPCh. 5.5 - Prob. 138RPCh. 5.5 - Air at 4.18 kg/m3 enters a nozzle that has an...Ch. 5.5 - Prob. 140RPCh. 5.5 - An air compressor compresses 15 L/s of air at 120...Ch. 5.5 - A steam turbine operates with 1.6 MPa and 350C...Ch. 5.5 - Refrigerant-134a enters an adiabatic compressor at...Ch. 5.5 - Prob. 144RPCh. 5.5 - Prob. 145RPCh. 5.5 - Prob. 146RPCh. 5.5 - Prob. 147RPCh. 5.5 - Steam enters a nozzle with a low velocity at 150C...Ch. 5.5 - Prob. 149RPCh. 5.5 - Prob. 150RPCh. 5.5 - Prob. 151RPCh. 5.5 - Prob. 152RPCh. 5.5 - Prob. 153RPCh. 5.5 - Cold water enters a steam generator at 20C and...Ch. 5.5 - An ideal gas expands in an adiabatic turbine from...Ch. 5.5 - Determine the power input for a compressor that...Ch. 5.5 - Prob. 157RPCh. 5.5 - Prob. 158RPCh. 5.5 - Prob. 159RPCh. 5.5 - Prob. 160RPCh. 5.5 - In a dairy plant, milk at 4C is pasteurized...Ch. 5.5 - Prob. 162RPCh. 5.5 - Prob. 163RPCh. 5.5 - Prob. 164RPCh. 5.5 - Prob. 165RPCh. 5.5 - Prob. 166RPCh. 5.5 - The average atmospheric pressure in Spokane,...Ch. 5.5 - The ventilating fan of the bathroom of a building...Ch. 5.5 - Prob. 169RPCh. 5.5 - Determine the rate of sensible heat loss from a...Ch. 5.5 - Prob. 171RPCh. 5.5 - An air-conditioning system requires airflow at the...Ch. 5.5 - A building with an internal volume of 400 m3 is to...Ch. 5.5 - The maximum flow rate of standard shower heads is...Ch. 5.5 - Prob. 176RPCh. 5.5 - Prob. 177RPCh. 5.5 - Steam enters a turbine steadily at 7 MPa and 600C...Ch. 5.5 - Reconsider Prob. 5178. Using appropriate software,...Ch. 5.5 - Prob. 180RPCh. 5.5 - A liquid R-134a bottle has an internal volume of...Ch. 5.5 - A pistoncylinder device initially contains 2 kg of...Ch. 5.5 - A pistoncylinder device initially contains 1.2 kg...Ch. 5.5 - A pressure cooker is a pot that cooks food much...Ch. 5.5 - A tank with an internal volume of 1 m3 contains...Ch. 5.5 - In a single-flash geothermal power plant,...Ch. 5.5 - An adiabatic air compressor is to be powered by a...Ch. 5.5 - The turbocharger of an internal combustion engine...Ch. 5.5 - Prob. 189RPCh. 5.5 - Consider an evacuated rigid bottle of volume V...Ch. 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. 195FEPCh. 5.5 - Prob. 196FEPCh. 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 - Refrigerant-134a at 1.4 MPa and 70C is throttled...Ch. 5.5 - Prob. 202FEPCh. 5.5 - Prob. 203FEPCh. 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...Ch. 5.5 - Saturated water vapor at 40C is to be condensed as...
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