College Physics
1st Edition
ISBN: 9781938168000
Author: Paul Peter Urone, Roger Hinrichs
Publisher: OpenStax College
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Chapter 15, Problem 39PE
What is the best coefficient of performance possible for a hypothetical refrigerator that could make liquid nitrogen at
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An ideal reversible refrigerator keeps its inside compartment at 9.0°C. What is the high temperature, Th, needed to give this refrigerator a coefficient of performance of 3.7?
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A certain brand of freezer is advertised to use 730 kW . hof energy per year. (a) Assuming the freezer operates for 5 hours eachday, how much power does it require while operating? (b) If the freezerkeeps its interior at -5.0 C in a 20.0 C room, what is its theoreticalmaximum performance coefficient? (c) What is the theoretical maximumamount of ice this freezer could make in an hour, starting withwater at 20.0 C?
Chapter 15 Solutions
College Physics
Ch. 15 - Describe the photo of the tea kettle at the...Ch. 15 - The first law of thermodynamics and the...Ch. 15 - Heat transfer Q and work done W are always energy...Ch. 15 - How do heat transfer and internal energy differ?...Ch. 15 - If you run down some stairs and stop, what happens...Ch. 15 - Give an explanation of how food energy (calories)...Ch. 15 - Identify the type of energy transferred to your...Ch. 15 - A great deal of effort time, and money has been...Ch. 15 - One method of converting heat transfer to doing...Ch. 15 - Would the previous question make any sense for an...
Ch. 15 - We ordinarily say that U=0 for an isothermal...Ch. 15 - The temperature of a rapidly expanding gas...Ch. 15 - Which cyclical process represented by the two...Ch. 15 - A real process may be nearly adiabatic if it...Ch. 15 - It is unlikely that a process can be isothermal...Ch. 15 - Imagine you are driving a car up Pike’s Peak in...Ch. 15 - Is a temperature difference necessary to operate a...Ch. 15 - Definitions of efficiency vary depending on how...Ch. 15 - Whyother than the fact that the second law of...Ch. 15 - Think about the drinking bird at the beginning of...Ch. 15 - Can improved engineering and materials be employed...Ch. 15 - Does the second law of thermodynamics alter the...Ch. 15 - Explain why heat pumps do not work as well in very...Ch. 15 - In some Northern European nations, homes are being...Ch. 15 - Why do refrigerators, air conditioners, and heat...Ch. 15 - Grocery store managers contend that there is less...Ch. 15 - Can you cool a kitchen by leaving the refrigerator...Ch. 15 - A woman shuts her summer cottage up in September...Ch. 15 - Consider a system with a certain energy content,...Ch. 15 - Does a gas become more orderly when it liquefies?...Ch. 15 - Explain how water’s entropy can decrease when it...Ch. 15 - Is a uniform-temperature gas more or less orderly...Ch. 15 - Give an example of a spontaneous process in which...Ch. 15 - What is the change in entropy in an adiabatic...Ch. 15 - Does the entropy at a star increase or decrease as...Ch. 15 - Explain why a building made of bricks has smaller...Ch. 15 - Explain why a building made of bricks has smaller...Ch. 15 - What is the change in internal energy of a car if...Ch. 15 - How much heat transfer occurs from a system, if...Ch. 15 - A system does 1.80108J of work while 7.50108J of...Ch. 15 - What is the change in internal energy of a system...Ch. 15 - Suppose a woman does 500 J of work and 9500 J of...Ch. 15 - (a) How much food energy will a man metabolize in...Ch. 15 - (a) What is the average metabolic rate in watts of...Ch. 15 - (a) How long will the energy in a 1470kJ (350kcal)...Ch. 15 - (a) A woman climbing the Washington Monument...Ch. 15 - A car tire contains 0.0380m3 S of air at a...Ch. 15 - A heliumfilled toy balloon has a gauge pressure of...Ch. 15 - Steam to drive an old—fashioned steam locomotive...Ch. 15 - A hand—driven tire pump has a piston with a 2.50cm...Ch. 15 - Calculate the net work output of a heat engine...Ch. 15 - What is the net work output of a heat engine that...Ch. 15 - Unreasonable Results What is wrong with the claim...Ch. 15 - (a) A cyclical heat engine, operating between...Ch. 15 - Construct Your Own Problem Consider a car's...Ch. 15 - Construct Your Own Problem Consider a car trip...Ch. 15 - A certain heat engine does 10.0 kJ of work and...Ch. 15 - With 2.56106J of heat transfer into this engine, a...Ch. 15 - (a) What is the work output of a cyclical heat...Ch. 15 - (a) What is the eficiency of a cyclical heat...Ch. 15 - The engine of a large Ship does 2.00108J of work...Ch. 15 - (a) How much heat transfer occurs to the...Ch. 15 - Assume that the turbines at a coal—powered power...Ch. 15 - This problem compares the energy output and heat...Ch. 15 - A certain gasoline engine has an efficiency of...Ch. 15 - A gascooled nuclear reactor operates between hot...Ch. 15 - (a) What is the hot reservoir temperature of a...Ch. 15 - Steam locomotives have an efficiency of 17.0% and...Ch. 15 - Practical steam engines utilize 450C steam, which...Ch. 15 - A coalfired electrical power station has an...Ch. 15 - Would you be willing to financially back an...Ch. 15 - Unreasonable Results (a) Suppose you want to...Ch. 15 - Unreasonable Results Calculate the cold reservoir...Ch. 15 - What is the coefficient of performance of an ideal...Ch. 15 - Suppose you have an ideal refrigerator that cools...Ch. 15 - What is the best coefficient of performance...Ch. 15 - In a very mild winter climate, a heat pump has...Ch. 15 - (a) What is the best coefficient of performance...Ch. 15 - (a) What is the best coefficient of performance...Ch. 15 - Suppose you want to operate an ideal refrigerator...Ch. 15 - An ideal heat pump is being considered for use in...Ch. 15 - A 4ton air conditioner removes 5.60107J (48,000...Ch. 15 - Show that the coefficients of performance of...Ch. 15 - (a) On a winter day, a certain house loses...Ch. 15 - On a hot summer day, 4.00106J of heat transfer...Ch. 15 - A hot rock ejected from a volcano's lava fountain...Ch. 15 - When 1.60105J of heat transfer occurs into a meat...Ch. 15 - The Sun radiates energy at the rate of 3.801026W...Ch. 15 - (a) In reaching equilibrium, how much heat...Ch. 15 - What is the decrease in entropy of 25.0 g of water...Ch. 15 - Find the increase in entropy of 1.00 kg of liquid...Ch. 15 - A large electrical power station generates 1000 MW...Ch. 15 - (a) How much heat transfer occurs from 20.0 kg of...Ch. 15 - Using Table 15.4, verify the contention that if...Ch. 15 - What percent of the time will you get something in...Ch. 15 - (a) If tossing 100 coins, how many ways...Ch. 15 - (a) What is the change in entropy if you start...Ch. 15 - (a) What is the change in entropy if you start...Ch. 15 - (a) If you toss 10 coins, what percent of the time...Ch. 15 - (a) Construct a table showing the macro states and...Ch. 15 - In an air conditioner, 12.65 MJ of heat transfer...
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- Show that the coefficients of performance of refrigerators and heat pumps are related by COPref=COPhp1. Start with the definitions of the COP s and the conservation of energy relationship between Qh, QC, and W.arrow_forwardA refrigerator has a coefficient of performance of 3.0. (a) If it requires 200 J of work per cycle, how much heat per cycle does it remove the cold reservoir? (b) How much heat per cycle is discarded to the hot reservoir?arrow_forwardIf a refrigerator discards 80 J of heat per cycle and its coefficient of performance is 6.0, what are (a) the quantity off heat it removes per cycle from a cold reservoir and (b) the amount of work per cycle required for its operation?arrow_forward
- 1. (a) What is the best coefficient of performance for a refrigerator that cools an environment at -26° C and has heat transfer to another environment at 49 ° C? COP ref (b) How much work must be done for a heat transfer of 4186 kJ from the cold environment? W = (c) What is the cost of doing this if the work costs 10.0 cents per 3.6 x 106 J (a kilowatt-hour)? Cost in cents = (d) How many kJ of heat transfer, Qh occurs into the warm environment? Qn kj = Think about what type of refrigerator might operate between these temperatures. Hint: Use the appropriate formula for a refrigerator which is different from a heat pump.arrow_forwardA refrigerator has a coefficient of performance of 2. The ice (cice = 2090 J/kg.ºC) tray compartment is at -14°C, and the %3D room temperature is 55°C. The refrigerator can convert 4.49 g of water (cwater = 4186 J/kg.°C) at 55°C to 4.49 g of ice at -14°C each minute. What input power (in W) is required? (Answer in 2 decimal places)arrow_forwardWhat is the coefficient of performance of a refrigerator that operates with Carnot efficiency between temperatures -3.00°C and #27.0°C? E 270K 28 400 ニ Selected Answer:arrow_forward
- A 23 600 BTU/hr. air-conditioning unit has an energy efficiency ratio (EER) of 7.5. The EER is defined as the number of BTU /hr. extracted from the room divided by the power consumption of the unit in watts (1 BTU = 1.055 kJ). What is the actual coefficient of performance of this refrigerator?|arrow_forward(a) What is the best coefficient of performance for a refrigerator that cools an environment at -28 C and has heat transfer to another environment at 49 ° C? COP, = 3.18 ref (b) How much work must be done for a heat transfer of 4186 kJ from the cold environment? W = 1316.4 kJ (c) What is the cost of doing this if the work costs 10.0 cents per 3.6x10° J (a kilowatt-hour)? Cost in cents = 3.66 (d) How many kJ of heat transfer, Q, occurs into the warm environment? Qn = 1314.5arrow_forward(a) What is the best coefficient of performance for a heat pump that has a hot reservoir temperature of 53.3°C and a cold reservoir temperature of -12.2°C? 4.982 (b) How much heat in kilocalories would it pump into the warm environment if 3.60 x 107 ) of work (10.0 kw · h) is put into it? 4.287e4 v kcal (c) Assume the cost of this work input is 10c/kW · h. Also assume that the cost of direct production of heat by burning natural gas is 81.0c per therm (a common unit of energy for natural gas), where a therm equals 1.055 x 10° J. Compare the cost of producing the same amount of heat by each method. cost of heat pump = 0,692 cost of natural gas Check unit conversions and your calculations.arrow_forward
- A refrigerator has a coefficient of performance of 2. The ice (cice = 2090 J/kg.°C) tray compartment is at –12°C, and the room temperature is 48°C. The refrigerator can convert 2.44 g of water (cwater= 4186 J/kg.°C) at 48°C to 2.44 g of ice at -12°C each minute. What input power (in W) is required? (Answer in 2 decimal places) A Moving to another question will save this response. « Close Windowarrow_forwardone of the most efficient engines ever built (actual efficiency 42.0%) operates between 430°C and 1 870°C. (a) What is its maximum theoretical efficiency? (b) How much power does the engine deliver if it absorbs 1.40 105 J of energy each second from the hotreservoir?arrow_forwardA refrigerator has a coefficient of performance of 2. The ice (cice = 2090 J/kg.°C) tray compartment is at-18°C, and the room temperature is 48°C. The refrigerator can convert 4.47 g of water (cwater = 4186 J/kg.°C) at 48°C to 4.47 g of ice at-18°C each minute. What input power (in W) is required? (Answer in 2 decimal places) « K Question 2 of 25> A Moving to another question will save this response. Adaptive 44HZ SÝNC ASUSarrow_forward
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