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16 Pages

### Thermo_5th_Chap06_P069

Course: E 234, Spring 2008
School: Stevens
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Word Count: 4317

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Heat 6-18 Carnot Engines 6-69C No. 6-70C The one that has a source temperature of 600C. This is true because the higher the temperature at which heat is supplied to the working fluid of a heat engine, the higher the thermal efficiency. 6-71 The source and sink temperatures of a Carnot heat engine and the rate of heat supply are given. The thermal efficiency and the power output are to be determined. Assumptions...

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Stevens - E - 234
6-34Special Topic: Household Refrigerators 6-104C It is a bad idea to overdesign the refrigeration system of a supermarket so that the entire airconditioning needs of the store can be met by refrigerated air without installing any air-conditioning
Stevens - E - 234
7-1Chapter 7 ENTROPYEntropy and the Increase of Entropy Principle 7-1C Yes. Because we used the relation (QH/TH) = (QL/TL) in the proof, which is the defining relation of absolute temperature. 7-2C No. The Q represents the net heat transfer dur
Stevens - E - 234
7-26Entropy Change of Incompressible Substances 7-52C No, because entropy is not a conserved property.7-53 A hot copper block is dropped into water in an insulated tank. The final equilibrium temperature of the tank and the total entropy change a
Stevens - E - 234
7-51Reversible Steady-Flow Work 7-87C The work associated with steady-flow devices is proportional to the specific volume of the gas. Cooling a gas during compression will reduce its specific volume, and thus the power consumed by the compressor. 7
Stevens - E - 234
7-51Reversible Steady-Flow Work 7-87C The work associated with steady-flow devices is proportional to the specific volume of the gas. Cooling a gas during compression will reduce its specific volume, and thus the power consumed by the compressor. 7
Stevens - E - 234
7-107Special Topic: Reducing the Cost of Compressed Air7-150 The total installed power of compressed air systems in the US is estimated to be about 20 million horsepower. The amount of energy and money that will be saved per year if the energy co
Stevens - E - 234
7-1357-184 The validity of the Clausius inequality is to be demonstrated using a reversible and an irreversible heat engine operating between the same temperature limits. Analysis Consider two heat engines, one reversible and one irreversible, both
Stevens - E - 234
7-1487-198 Refrigerant-134a is vaporized by air in the evaporator of an air-conditioner. For specified flow rates, the exit temperature of air and the rate of entropy generation are to be determined for the cases of an insulated and uninsulated eva
Stevens - E - 234
8-1Chapter 8 EXERGY A MEASURE OF WORK POTENTIALExergy, Irreversibility, Reversible Work, and Second-Law Efficiency 8-1C Reversible work differs from the useful work by irreversibilities. For reversible processes both are identical. Wu = Wrev -I.
Stevens - E - 234
8-33Second-Law Analysis of Control Volumes8-54 Steam is throttled from a specified state to a specified pressure. The wasted work potential during this throttling process is to be determined. Assumptions 1 This is a steady-flow process since ther
Stevens - E - 234
8-608-79 A rigid tank initially contains saturated R-134a vapor. The tank is connected to a supply line, and R134a is allowed to enter the tank. The mass of the R-134a that entered the tank and the exergy destroyed during this process are to be det
Stevens - E - 234
8-79Review Problems8-95 Refrigerant-134a is expanded adiabatically in an expansion valve. The work potential of R-134a at the inlet, the exergy destruction, and the second-law efficiency are to be determined. Assumptions 1 Steady operating condit
Stevens - E - 234
8-968-113 A well-insulated room is heated by a steam radiator, and the warm air is distributed by a fan. The average temperature in the room after 30 min, the entropy changes of steam and air, and the exergy destruction during this process are to b
Stevens - E - 234
8-1118-124 An evacuated bottle is surrounded by atmospheric air. A valve is opened, and air is allowed to fill the bottle. The amount of heat transfer through the wall of the bottle when thermal and mechanical equilibrium is established and the amo
Stevens - E - 234
9-1Chapter 9 GAS POWER CYCLESActual and Ideal Cycles, Carnot cycle, Air-Standard Assumptions 9-1C The Carnot cycle is not suitable as an ideal cycle for all power producing devices because it cannot be approximated using the hardware of actual pow
Stevens - E - 234
9-40Stirling and Ericsson Cycles 9-60C The efficiencies of the Carnot and the Stirling cycles would be the same, the efficiency of the Otto cycle would be less. 9-61C The efficiencies of the Carnot and the Ericsson cycles would be the same, the eff
Stevens - E - 234
9-70Brayton Cycle with Intercooling, Reheating, and Regeneration 9-101C As the number of compression and expansion stages are increased and regeneration is employed, the ideal Brayton cycle will approach the Ericsson cycle. 9-102C (a) decrease, (b)
Stevens - E - 234
9-97Review Problems9-132 A turbocharged four-stroke V-16 diesel engine produces 3500 hp at 1200 rpm. The amount of power produced per cylinder per mechanical and per thermodynamic cycle is to be determined. Analysis Noting that there are 16 cylin
Stevens - E - 234
9-1319-159 EES The effect of variable specific heats on the thermal efficiency of the ideal Otto cycle using air as the working fluid is to be investigated. The percentage of error involved in using constant specific heat values at room temperature
Stevens - E - 234
10-1Chapter 10 VAPOR AND COMBINED POWER CYCLESCarnot Vapor Cycle 10-1C Because excessive moisture in steam causes erosion on the turbine blades. The highest moisture content allowed is about 10%. 10-2C The Carnot cycle is not a realistic model for
Stevens - E - 234
10-3010-46 A steam power plant operates on an ideal regenerative Rankine cycle with two open feedwater heaters. The net power output of the power plant and the thermal efficiency of the cycle are to be determined. Assumptions 1 Steady operating con
Stevens - E - 234
10-5210-67 A cogeneration plant is to generate power and process heat. Part of the steam extracted from the turbine at a relatively high pressure is used for process heating. The net power produced and the utilization factor of the plant are to be
Stevens - E - 234
10-77Special Topic: Binary Vapor Cycles 10-82C Binary power cycle is a cycle which is actually a combination of two cycles; one in the high temperature region, and the other in the low temperature region. Its purpose is to increase thermal efficien
Stevens - E - 234
10-9310-99 A combined gas-steam power plant is considered. The topping cycle is an ideal gas-turbine cycle and the bottoming cycle is an ideal reheat Rankine cycle. The mass flow rate of air in the gas-turbine cycle, the rate of total heat input, a
Stevens - E - 234
11-1Chapter 11 REFRIGERATION CYCLESThe Reversed Carnot Cycle 11-1C Because the compression process involves the compression of a liquid-vapor mixture which requires a compressor that will handle two phases, and the expansion process involves the e
Stevens - E - 234
11-36Gas Refrigeration Cycles 11-49C The ideal gas refrigeration cycle is identical to the Brayton cycle, except it operates in the reversed direction. 11-50C The reversed Stirling cycle is identical to the Stirling cycle, except it operates in the
Stevens - E - 234
12-1Chapter 12 THERMODYNAMIC PROPERTY RELATIONSPartial Derivatives and Associated Relations 12-1Czdzx dx(z)y (z)xy dy dz = (z ) x + (z ) yy x dx x +dx dyy + dyyx12-2C For functions that depend on one variable, they are identical
Stevens - E - 234
12-2912-58E The enthalpy of nitrogen at 400 R and 2000 psia is to be determined using data from the ideal-gas nitrogen table and the generalized enthalpy departure chart. Analysis (a) From the ideal gas table of nitrogen (Table A-18E) we readh = 2
Stevens - E - 234
13-1Chapter 13 GAS MIXTURESComposition of Gas Mixtures 13-1C It is the average or the equivalent gas constant of the gas mixture. No. 13-2C No. We can do this only when each gas has the same mole fraction. 13-3C It is the average or the equivalent
Stevens - E - 234
13-3513-64 Heat is transferred to a gas mixture contained in a piston cylinder device discussed in previous problem. The total entropy change and the exergy destruction are to be determined for two cases. Analysis The entropy generated during this
Stevens - E - 234
14-1Chapter 14 GAS-VAPOR MIXTURES AND AIR CONDITIONINGDry and Atmospheric Air, Specific and Relative Humidity 14-1C Yes; by cooling the air at constant pressure. 14-2C Yes. 14-3C Specific humidity will decrease but relative humidity will increase.
Stevens - E - 234
14-2014-69E Air enters a heating section at a specified pressure, temperature, velocity, and relative humidity. The exit temperature of air, the exit relative humidity, and the exit velocity are to be determined. Assumptions 1 This is a steady-flow
Stevens - E - 234
14-45Adiabatic Mixing of Airstreams 14-100C This will occur when the straight line connecting the states of the two streams on the psychrometric chart crosses the saturation line. 14-101C Yes.14-102 Two airstreams are mixed steadily. The specific
Stevens - E - 234
14-58Review Problems14-115 Air is compressed by a compressor and then cooled to the ambient temperature at high pressure. It is to be determined if there will be any condensation in the compressed air lines. Assumptions The air and the water vapo
Stevens - E - 234
15-1Chapter 15 CHEMICAL REACTIONSFuels and Combustion 15-1C Gasoline is C8H18, diesel fuel is C12H26, and natural gas is CH4. 15-2C Nitrogen, in general, does not react with other chemical species during a combustion process but its presence affec
Stevens - E - 234
15-24First Law Analysis of Reacting Systems 15-46C In this case U + Wb = H, and the conservation of energy relation reduces to the form of the steady-flow energy relation. 15-47C The heat transfer will be the same for all cases. The excess oxygen a
Stevens - E - 234
15-43Adiabatic Flame Temperature 15-68C For the case of stoichiometric amount of pure oxygen since we have the same amount of chemical energy released but a smaller amount of mass to absorb it. 15-69C Under the conditions of complete combustion wit
Stevens - E - 234
15-64Review Problems15-88 A sample of a certain fluid is burned in a bomb calorimeter. The heating value of the fuel is to be determined. Properties The specific heat of water is 4.18 kJ/kg.C (Table A-3). Analysis We take the water as the system,
Stevens - E - 234
15-8315-102 A mixture of 40% by volume methane, CH4, and 60% by volume propane, C3H8, is burned completely with theoretical air. The amount of water formed during combustion process that will be condensed is to be determined. 40% CH4 Assumptions 1
Stevens - E - 234
16-1Chapter 16 CHEMICAL AND PHASE EQUILIBRIUMThe Kp and Equilibrium Composition of Ideal Gases 16-1C Because when a reacting system involves heat transfer, the increase-in-entropy principle relation requires a knowledge of heat transfer between th
Stevens - E - 234
16-1716-29E A mixture of CO, O2, and N2 is heated to a high temperature at a constant pressure. The equilibrium composition is to be determined. Assumptions 1 The equilibrium composition consists of CO2, CO, O2, and N2. 2 The constituents of the mi
Stevens - E - 234
16-4316-52 The KP value of the combustion process H2 + 1/2O2 H2O is to be determined at a specified temperature using hR data and KP value . Assumptions Both the reactants and products are ideal gases. Analysis The hR and KP data are related to ea
Stevens - E - 234
16-6016-83 A mixture of H2 and O2 in a tank is ignited. The equilibrium composition of the product gases and the amount of heat transfer from the combustion chamber are to be determined. Assumptions 1 The equilibrium composition consists of H2O, H2
Stevens - E - 234
17-1Chapter 17 COMPRESSIBLE FLOWStagnation Properties 17-1C The temperature of the air will rise as it approaches the nozzle because of the stagnation process. 17-2C Stagnation enthalpy combines the ordinary enthalpy and the kinetic energy of a fl
Stevens - E - 234
17-45Duct Flow with Heat Transfer and Negligible Friction (Rayleigh Flow) 17-96C The characteristic aspect of Rayleigh flow is its involvement of heat transfer. The main assumptions associated with Rayleigh flow are: the flow is steady, one-dimensi
Stevens - E - 234
17-64Review Problems 17-118 A leak develops in an automobile tire as a result of an accident. The initial mass flow rate of air through the leak is to be determined. Assumptions 1 Air is an ideal gas with constant specific heats. 2 Flow of air thro
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