EBK THERMODYNAMICS: AN ENGINEERING APPR
8th Edition
ISBN: 8220102809444
Author: CENGEL
Publisher: YUZU
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Chapter 6.11, Problem 35P
A refrigerator has a COP of 1.5. That is, the refrigerator removes 1.5 kWh of energy from the refrigerated space for each 1 kWh of electricity it consumes. Is this a violation of the first law of
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A Carnot heat pump is used to maintain the temperature inside a building at 20 ∘C. Significantly, the colder it gets outside, the more heat is lost through the walls and windows of the building. Assume that 45 kW of heat are lost for each degree difference between the outside and the inside temperature. That means that the colder it gets, the harder the heat pump will need to work. However, for safety reasons, the controller circuit for the heat pump limits its electrical power consumption to 195 kW. What's the coldest it can get outside before the heat pump can't maintain the building temperature adequately?
A heat pump with a COP of 3.2 is used to heat a perfectly sealed house (no air leaks). The entire mass within the house (air, furniture, etc.) is equivalent to 1200 kg of air. When running, the heat pump consumes electric power at a rate of 5 kW. The temperature of the house was 7°C when the heat pump was turned on. If heat transfer through the envelope of the house (walls, roof, etc.) is negligible, the length of time the heat pump must run to raise the temperature of the entire contents of the house to 22°C is (a) 13.5 min (b) 43.1 min (c) 138 min (d) 18.8 min (e) 808 min
By supplying energy to a house at a rate of 25,000 kJ/hr, a heat pump maintains the
temperature of the dwelling at 20 C when the outside air is at -10 C. If electricity
costs 8 cents per kW-hr, determine the minimum theoretical operating cost to heat
the house for 24 hours.
$1.97
O $1.37
$1.75
O $1.51
O$1.64
Chapter 6 Solutions
EBK THERMODYNAMICS: AN ENGINEERING APPR
Ch. 6.11 - Describe an imaginary process that violates both...Ch. 6.11 - Describe an imaginary process that satisfies the...Ch. 6.11 - Describe an imaginary process that satisfies the...Ch. 6.11 - An experimentalist claims to have raised the...Ch. 6.11 - Prob. 5PCh. 6.11 - Consider the process of baking potatoes in a...Ch. 6.11 - What are the characteristics of all heat engines?Ch. 6.11 - What is the KelvinPlanck expression of the second...Ch. 6.11 - Is it possible for a heat engine to operate...Ch. 6.11 - Baseboard heaters are basically electric...
Ch. 6.11 - Does a heat engine that has a thermal efficiency...Ch. 6.11 - In the absence of any friction and other...Ch. 6.11 - Are the efficiencies of all the work-producing...Ch. 6.11 - Consider a pan of water being heated (a) by...Ch. 6.11 - Prob. 15PCh. 6.11 - Prob. 16PCh. 6.11 - A heat engine has a heat input of 3 104 Btu/h and...Ch. 6.11 - Prob. 18PCh. 6.11 - A 600-MW steam power plant, which is cooled by a...Ch. 6.11 - Prob. 20PCh. 6.11 - A heat engine with a thermal efficiency of 45...Ch. 6.11 - A steam power plant with a power output of 150 MW...Ch. 6.11 - An automobile engine consumes fuel at a rate of 22...Ch. 6.11 - Prob. 24PCh. 6.11 - Prob. 25PCh. 6.11 - A coal-burning steam power plant produces a net...Ch. 6.11 - An Ocean Thermal Energy Conversion (OTEC) power...Ch. 6.11 - What is the difference between a refrigerator and...Ch. 6.11 - Prob. 29PCh. 6.11 - In a refrigerator, heat is transferred from a...Ch. 6.11 - A heat pump is a device that absorbs energy from...Ch. 6.11 - Define the coefficient of performance of a...Ch. 6.11 - Define the coefficient of performance of a heat...Ch. 6.11 - Prob. 34PCh. 6.11 - A refrigerator has a COP of 1.5. That is, the...Ch. 6.11 - What is the Clausius expression of the second law...Ch. 6.11 - Show that the KelvinPlanck and the Clausius...Ch. 6.11 - Prob. 38PCh. 6.11 - Determine the COP of a heat pump that supplies...Ch. 6.11 - Prob. 40PCh. 6.11 - Prob. 41PCh. 6.11 - 6–42 An air conditioner removes heat steadily from...Ch. 6.11 - 6–43 A food department is kept at –12°C by a...Ch. 6.11 - A household refrigerator that has a power input of...Ch. 6.11 - When a man returns to his well-sealed house on a...Ch. 6.11 - Prob. 47PCh. 6.11 - Prob. 48PCh. 6.11 - 6–49 A heat pump is used to maintain a house at a...Ch. 6.11 - Prob. 50PCh. 6.11 - A household refrigerator runs one-fourth of the...Ch. 6.11 - Prob. 52PCh. 6.11 - Consider an office room that is being cooled...Ch. 6.11 - Prob. 54PCh. 6.11 - Refrigerant-134a enters the condenser of a...Ch. 6.11 - An inventor claims to have developed a resistance...Ch. 6.11 - Prob. 57PCh. 6.11 - A cold canned drink is left in a warmer room where...Ch. 6.11 - A block slides down an inclined plane with...Ch. 6.11 - Prob. 60PCh. 6.11 - Show that processes that use work for mixing are...Ch. 6.11 - Why does a nonquasi-equilibrium compression...Ch. 6.11 - Prob. 63PCh. 6.11 - Prob. 64PCh. 6.11 - Prob. 65PCh. 6.11 - Why are engineers interested in reversible...Ch. 6.11 - What are the four processes that make up the...Ch. 6.11 - Prob. 68PCh. 6.11 - Prob. 69PCh. 6.11 - Prob. 70PCh. 6.11 - Somebody claims to have developed a new reversible...Ch. 6.11 - Is there any way to increase the efficiency of a...Ch. 6.11 - Consider two actual power plants operating with...Ch. 6.11 - Prob. 74PCh. 6.11 - Prob. 75PCh. 6.11 - 6–76 A Carnot heat engine receives 650 kJ of heat...Ch. 6.11 - A Carnot heat engine operates between a source at...Ch. 6.11 - A heat engine operates between a source at 477C...Ch. 6.11 - Prob. 80PCh. 6.11 - Prob. 81PCh. 6.11 - In tropical climates, the water near the surface...Ch. 6.11 - 6–83 A well-established way of power generation...Ch. 6.11 - Prob. 84PCh. 6.11 - Prob. 85PCh. 6.11 - How can we increase the COP of a Carnot...Ch. 6.11 - In an effort to conserve energy in a heat-engine...Ch. 6.11 - Prob. 88PCh. 6.11 - Prob. 89PCh. 6.11 - 6–90 During an experiment conducted in a room at...Ch. 6.11 - Prob. 91PCh. 6.11 - An air-conditioning system operating on the...Ch. 6.11 - Prob. 93PCh. 6.11 - Prob. 94PCh. 6.11 - Prob. 95PCh. 6.11 - Prob. 96PCh. 6.11 - 6–97 A heat pump is used to maintain a house at...Ch. 6.11 - Prob. 98PCh. 6.11 - Prob. 99PCh. 6.11 - Prob. 100PCh. 6.11 - A commercial refrigerator with refrigerant-134a as...Ch. 6.11 - Prob. 102PCh. 6.11 - A heat pump is to be used for heating a house in...Ch. 6.11 - A Carnot heat pump is to be used to heat a house...Ch. 6.11 - A Carnot heat engine receives heat from a...Ch. 6.11 - Prob. 106PCh. 6.11 - Prob. 107PCh. 6.11 - Prob. 108PCh. 6.11 - Derive an expression for the COP of a completely...Ch. 6.11 - Prob. 110PCh. 6.11 - Prob. 111PCh. 6.11 - Prob. 112PCh. 6.11 - Prob. 113PCh. 6.11 - Someone proposes that the entire...Ch. 6.11 - Prob. 115PCh. 6.11 - Prob. 116PCh. 6.11 - Prob. 117PCh. 6.11 - It is often stated that the refrigerator door...Ch. 6.11 - Prob. 119RPCh. 6.11 - A Carnot heat pump is used to heat and maintain a...Ch. 6.11 - Prob. 121RPCh. 6.11 - Prob. 122RPCh. 6.11 - A refrigeration system uses a water-cooled...Ch. 6.11 - A heat pump with a COP of 2.8 is used to heat an...Ch. 6.11 - Prob. 125RPCh. 6.11 - Consider a Carnot refrigeration cycle executed in...Ch. 6.11 - Consider two Carnot heat engines operating in...Ch. 6.11 - Prob. 129RPCh. 6.11 - A heat engine operates between two reservoirs at...Ch. 6.11 - Prob. 132RPCh. 6.11 - An old gas turbine has an efficiency of 21 percent...Ch. 6.11 - Prob. 134RPCh. 6.11 - Prob. 135RPCh. 6.11 - Prob. 136RPCh. 6.11 - Prob. 137RPCh. 6.11 - Prob. 138RPCh. 6.11 - Prob. 139RPCh. 6.11 - A refrigeration system is to cool bread loaves...Ch. 6.11 - The drinking water needs of a production facility...Ch. 6.11 - Prob. 143RPCh. 6.11 - Prob. 145RPCh. 6.11 - Prob. 146RPCh. 6.11 - Prob. 147RPCh. 6.11 - Prob. 148RPCh. 6.11 - A heat pump with refrigerant-134a as the working...Ch. 6.11 - Prob. 150RPCh. 6.11 - Prob. 151RPCh. 6.11 - Prob. 153RPCh. 6.11 - Prob. 154RPCh. 6.11 - Prob. 155RPCh. 6.11 - A 2.4-m-high 200-m2 house is maintained at 22C by...Ch. 6.11 - Prob. 157FEPCh. 6.11 - Prob. 158FEPCh. 6.11 - A heat pump is absorbing heat from the cold...Ch. 6.11 - A heat engine cycle is executed with steam in the...Ch. 6.11 - A heat engine receives heat from a source at 1000C...Ch. 6.11 - Prob. 162FEPCh. 6.11 - A refrigeration cycle is executed with R-134a...Ch. 6.11 - A heat pump with a COP of 3.2 is used to heat a...Ch. 6.11 - A heat engine cycle is executed with steam in the...Ch. 6.11 - An air-conditioning system operating on the...Ch. 6.11 - Prob. 167FEPCh. 6.11 - Two Carnot heat engines are operating in series...Ch. 6.11 - Consider a Carnot refrigerator and a Carnot heat...Ch. 6.11 - A typical new household refrigerator consumes...Ch. 6.11 - A window air conditioner that consumes 1 kW of...
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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, mechanical-engineering and related others by exploring similar questions and additional content below.Similar questions
- (1) Explain how a heat engine works. (2) Explain the 2nd Law of thermodynamics.arrow_forwardExplain the principle of refrigerator? Show that a reversible heat engine acts as a refrigerator.arrow_forwardOn average, 0.59 kg of CO2 is produced for each kWh of electricity generated from a power plant that burns natural gas. A typical new household refrigerator uses about 700 kWh of electricity per year. Determine the amount of CO2 production that is due to the refrigerators in a city with 300,000 households.arrow_forward
- A heat pump is used to extract heat from the outside atmosphere to heat the inside of a building. On a day when the outside air temperature is Tc°C, the heat pump is operating to a COP of 2.7, maintaining the inside temperature of the building at Th°C. If the building is losing heat at the rate of 62,893 kJ/hour in these conditions, determine how much power (kW) must be supplied to a heat pump.arrow_forwardProve that if you had a heat engine whose efficiency was better than the ideal value (4.5), you could hook it up to an ordinary Carnot refrigerator to make a refrigerator that requires no work input.arrow_forwardIn a given process, a heat engine requires 2500J of energy and exhausts 1200J of heat. What is its efficiency?arrow_forward
- An older refrigerator uses 4.22 kWh per day while an Energy Star refrigerator uses 0.78 kWh per day (both running continuously). What is the difference in power between the two refrigerators? If your electricity costs $0.13 per kWh, how much money does the Energy Star refrigerator save over 5 years?arrow_forwardA heat engine receives a heat-transfer at the rate of 2 MW at a high temperature of 750 °C. The engine releases energy to its surrounding at 300 K and work is produced at a rate of 1200 kW. What are 1. The energy released to the ambient surroundings? 2. The efficiency of the engine?arrow_forwardYou have a refrigerator in your garage. Does it perform differently in the summer than in the winter?Explain.arrow_forward
- A heat pump with a coefficient of performance of 3.5 provides energy at an average rate of 70,000 kJ/h to maintain a building at 20 deg C on a day when the outside temperature is -5 deg C. If electricity costs 8.5 cents per kWh, (a) determine the actual operating cost and the minimum theoretical operating cost, each in $/day. (b) compare the results of part (a) with the cost of electrical-resistance heating.arrow_forwardAn inventor claims to have developed a resistance heater that supplies 1.2 kWh of energy to a room for each kWh of electricity it consumes. Is this a reasonable claim, or has the inventor developed a perpetual-motion machine? Explain.arrow_forwardA Carnot heat pump is used to heat and maintain a residential building at 75°F. An energy analysis of the house reveals that it loses heat at a rate of 2500 Btu/h per °F temperature difference between the indoors and the outdoors. For an outdoor temperature of 35°F, determine the coefficient of performance.arrow_forward
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