Thermodynamics: An Engineering Approach
8th Edition
ISBN: 9780073398174
Author: Yunus A. Cengel Dr., Michael A. Boles
Publisher: McGraw-Hill Education
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Chapter 4.5, Problem 38P
A 40-L electrical radiator containing heating oil is placed in a 50-m3 room. Both the room and the oil in the radiator are initially at 10°C. The radiator with a rating of 2.4 kW is now turned on. At the same time, heat is lost from the room at an average rate of 0.35 kJ/s. After some time, the average temperature is measured to be 20°C for the air in the room, and 50°C for the oil in the radiator. Taking the density and the specific heat of the oil to be 950 kg/m3 and 2.2 kJ/kg·°C, respectively, determine how long the heater is kept on. Assume the room is well sealed so that there are no air leaks.
FIGURE P4–39
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A piston-cylinder device as shown in Figure 1-7, initially contains 0.75 kg of refrigerant-
134a at 120 kPa and 20°C. Heat is now transferred to the refrigerant from a source at
150°C, and the piston, which is resting on a set of stops, starts moving when the pressure
inside reaches 140 kPa. Heat transfer continues until the temperature reaches 90°C.
Assuming the surroundings to be at 25°C and 100 kPa, determine:
(a) the work done,
(b) the heat transfer,
(c) the exergy destroyed,
(d) the second law efficiency of this process.
Environment
100 kPa
25°C
R-134a
R-134a
0.75 kg
0.75 kg
Нeat
120 kPa
140 kPa
20°C
90°C
Initial State
Heat Source
Final State
150°C
Figure 1-7 A piston-cylinder device
A 50-L electrical radiator containing heating oil is placed in a 50-m³ room. Both the room and the oil in the
radiator are initially at 5°C. The radiator with a rating of 3 kW is now turned on. At the same time, heat
is lost from the room at an average rate of 0.3 kJ/s. After some time, the average temperature is measured
to be 20°C for the air in the room, and 60°C for the oil in the radiator. Taking the density and the specific
heat of the oil to be 950 kg/m³ and 2.2kJ/(kg °C), respectively, determine how long the heater is kept on.
Assume the room is well-sealed so that there are no air leaks.
A piston-cylinder device contains 0.1 m3 of refrigerant 134a at 0.24 MPa and 40ºC. Initially the piston is fixed with a pin. Heat is transferred now to the refrigerant from a source at 100ºC until the pressure rises to 0.28 MPa. Then, heat is given to an environment with a temperature of 25ºC at a constant pressure (the pin is pulled and in this case, the mass of the piston and the masses on it and the pressure created by the atmospheric pressure are equal to the pressure inside the cylinder) the temperature is brought to a temperature of 50ºC.
a) Determine the heat and work interaction for each process
b) Sketch the P-v and T-s diagrams of the processes with respect to the saturation lines
c) Determine the entropy change of the refrigerant 134a during these two processes
d) Determine the entropy generation during these processes. Are these processes appropriate to 2. law of thermodynamics, explain
Chapter 4 Solutions
Thermodynamics: An Engineering Approach
Ch. 4.5 - An ideal gas at a given state expands to a fixed...Ch. 4.5 - Nitrogen at an initial state of 300 K, 150 kPa,...Ch. 4.5 - 4–3 The volume of 1 kg of helium in a...Ch. 4.5 - 4–4E Calculate the total work, in Btu, for process...Ch. 4.5 - 4–5 A piston–cylinder device initially contains...Ch. 4.5 - A pistoncylinder device with a set of stops...Ch. 4.5 - 4–7 A piston–cylinder device initially contains...Ch. 4.5 - 4–8 A mass of 5 kg of saturated water vapor at 300...Ch. 4.5 - 1 m3 of saturated liquid water at 200C is expanded...Ch. 4.5 - A gas is compressed from an initial volume of 0.42...
Ch. 4.5 - A mass of 1.5 kg of air at 120 kPa and 24C is...Ch. 4.5 - During some actual expansion and compression...Ch. 4.5 - 4–14 A frictionless piston–cylinder device...Ch. 4.5 - Prob. 15PCh. 4.5 - During an expansion process, the pressure of a gas...Ch. 4.5 - A pistoncylinder device initially contains 0.4 kg...Ch. 4.5 - 4–19E Hydrogen is contained in a piston–cylinder...Ch. 4.5 - A pistoncylinder device contains 0.15 kg of air...Ch. 4.5 - 1 kg of water that is initially at 90C with a...Ch. 4.5 - Prob. 22PCh. 4.5 - An ideal gas undergoes two processes in a...Ch. 4.5 - A pistoncylinder device contains 50 kg of water at...Ch. 4.5 - Prob. 26PCh. 4.5 - 4–27E A closed system undergoes a process in which...Ch. 4.5 - A rigid container equipped with a stirring device...Ch. 4.5 - A 0.5-m3rigid tank contains refrigerant-134a...Ch. 4.5 - A 20-ft3 rigid tank initially contains saturated...Ch. 4.5 - Prob. 31PCh. 4.5 - Prob. 32PCh. 4.5 - Prob. 33PCh. 4.5 - An insulated pistoncylinder device contains 5 L of...Ch. 4.5 -
4–35 A piston–cylinder device initially...Ch. 4.5 - Prob. 37PCh. 4.5 - A 40-L electrical radiator containing heating oil...Ch. 4.5 - Steam at 75 kPa and 8 percent quality is contained...Ch. 4.5 - Prob. 40PCh. 4.5 - An insulated tank is divided into two parts by a...Ch. 4.5 - Is the relation u = mcv,avgT restricted to...Ch. 4.5 - Is the relation h = mcp,avgT restricted to...Ch. 4.5 - Is the energy required to heat air from 295 to 305...Ch. 4.5 - A fixed mass of an ideal gas is heated from 50 to...Ch. 4.5 - A fixed mass of an ideal gas is heated from 50 to...Ch. 4.5 - A fixed mass of an ideal gas is heated from 50 to...Ch. 4.5 - Prob. 49PCh. 4.5 - What is the change in the enthalpy, in kJ/kg, of...Ch. 4.5 - Prob. 51PCh. 4.5 - Prob. 52PCh. 4.5 - Prob. 53PCh. 4.5 - Determine the internal energy change u of...Ch. 4.5 - Prob. 55PCh. 4.5 - Prob. 56PCh. 4.5 - Is it possible to compress an ideal gas...Ch. 4.5 - A 3-m3 rigid tank contains hydrogen at 250 kPa and...Ch. 4.5 - A 10-ft3 tank contains oxygen initially at 14.7...Ch. 4.5 - 4–60E A rigid tank contains 10 Ibm of air at 30...Ch. 4.5 - 4–61E Nitrogen gas to 20 psia and 100°F initially...Ch. 4.5 - An insulated rigid tank is divided into two equal...Ch. 4.5 - 4–63 A 4-m × 5-m × 6-m room is to be heated by a...Ch. 4.5 - 4-64 A student living in a 3-m × 4-m × 4-m...Ch. 4.5 - A 4-m 5-m 7-m room is heated by the radiator of...Ch. 4.5 - 4–66 Argon is compressed in a polytropic process...Ch. 4.5 - An insulated pistoncylinder device contains 100 L...Ch. 4.5 - 4–68 A spring-loaded piston-cylinder device...Ch. 4.5 - An ideal gas contained in a pistoncylinder device...Ch. 4.5 - Air is contained in a variable-load pistoncylinder...Ch. 4.5 - Prob. 71PCh. 4.5 - Prob. 72PCh. 4.5 - Prob. 74PCh. 4.5 - Prob. 75PCh. 4.5 - Prob. 76PCh. 4.5 - 4–77 Air is contained in a piston-cylinder device...Ch. 4.5 - A pistoncylinder device contains 4 kg of argon at...Ch. 4.5 - The state of liquid water is changed from 50 psia...Ch. 4.5 - During a picnic on a hot summer day, all the cold...Ch. 4.5 - Consider a 1000-W iron whose base plate is made of...Ch. 4.5 - Stainless steel ball bearings ( = 8085 kg/m3 and...Ch. 4.5 - In a production facility, 1.6-in-thick 2-ft 2-ft...Ch. 4.5 - Prob. 84PCh. 4.5 - An electronic device dissipating 25 W has a mass...Ch. 4.5 - Prob. 87PCh. 4.5 - 4–88 In a manufacturing facility, 5-cm-diameter...Ch. 4.5 - Prob. 89PCh. 4.5 - Is the metabolizable energy content of a food the...Ch. 4.5 - Is the number of prospective occupants an...Ch. 4.5 - Prob. 92PCh. 4.5 - Prob. 93PCh. 4.5 - Consider two identical 80-kg men who are eating...Ch. 4.5 - A 68-kg woman is planning to bicycle for an hour....Ch. 4.5 - A 90-kg man gives in to temptation and eats an...Ch. 4.5 - A 60-kg man used to have an apple every day after...Ch. 4.5 - Consider a man who has 20 kg of body fat when he...Ch. 4.5 - Consider two identical 50-kg women, Candy and...Ch. 4.5 - Prob. 100PCh. 4.5 - Prob. 101PCh. 4.5 - Prob. 102PCh. 4.5 - Prob. 103PCh. 4.5 - Prob. 104PCh. 4.5 - Prob. 105PCh. 4.5 - Prob. 106PCh. 4.5 - Prob. 107RPCh. 4.5 - Consider a pistoncylinder device that contains 0.5...Ch. 4.5 - Air in the amount of 2 lbm is contained in a...Ch. 4.5 - Air is expanded in a polytropic process with n =...Ch. 4.5 - Nitrogen at 100 kPa and 25C in a rigid vessel is...Ch. 4.5 - Prob. 112RPCh. 4.5 - Prob. 113RPCh. 4.5 - Prob. 114RPCh. 4.5 - 4–115 A mass of 12 kg of saturated...Ch. 4.5 - Prob. 116RPCh. 4.5 - Prob. 117RPCh. 4.5 - Prob. 118RPCh. 4.5 - Prob. 119RPCh. 4.5 - Prob. 120RPCh. 4.5 - Prob. 121RPCh. 4.5 - Prob. 122RPCh. 4.5 - Prob. 123RPCh. 4.5 - Prob. 124RPCh. 4.5 - Prob. 125RPCh. 4.5 - Prob. 126RPCh. 4.5 - Prob. 127RPCh. 4.5 - Prob. 128RPCh. 4.5 - A well-insulated 3-m 4m 6-m room initially at 7C...Ch. 4.5 - Prob. 131RPCh. 4.5 - Prob. 133RPCh. 4.5 - Prob. 134RPCh. 4.5 - An insulated pistoncylinder device initially...Ch. 4.5 - Prob. 137RPCh. 4.5 - Prob. 138RPCh. 4.5 - A pistoncylinder device initially contains 0.35 kg...Ch. 4.5 - Prob. 140RPCh. 4.5 - 4–141 One kilogram of carbon dioxide is compressed...Ch. 4.5 - Prob. 142RPCh. 4.5 - Prob. 143RPCh. 4.5 - Prob. 144FEPCh. 4.5 - A 3-m3 rigid tank contains nitrogen gas at 500 kPa...Ch. 4.5 - Prob. 146FEPCh. 4.5 - A well-sealed room contains 60 kg of air at 200...Ch. 4.5 - Prob. 148FEPCh. 4.5 - A room contains 75 kg of air at 100 kPa and 15C....Ch. 4.5 - A pistoncylinder device contains 5 kg of air at...Ch. 4.5 - Prob. 151FEPCh. 4.5 - Prob. 152FEPCh. 4.5 - A 2-kW electric resistance heater submerged in 5...Ch. 4.5 - 1.5 kg of liquid water initially at 12C is to be...Ch. 4.5 - An ordinary egg with a mass of 0.1 kg and a...Ch. 4.5 - 4–156 An apple with an average mass of 0.18 kg and...Ch. 4.5 - A 6-pack of canned drinks is to be cooled from 18C...Ch. 4.5 - An ideal gas has a gas constant R = 0.3 kJ/kgK and...Ch. 4.5 - Prob. 159FEPCh. 4.5 - Prob. 161FEP
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