A house heated by a heat pump requires QH= 25 kW of heat flow when acting between -5°C outside and 20 °C inside. A. Assuming the heat pump is ideal, how much work (in kW) is required to maintain this heat flow. B. Heat pumps are usually rated by their coefficient of performance 7= Q#/W. Find 7 for the ideal case. C. In practice 7× 4. For this 7, find the work actually required.

A house heated by a heat pump requires QH= 25 kW of heat flow when acting between -5°C outside and 20 °C inside. A. Assuming the heat pump is ideal, how much work (in kW) is required to maintain this heat flow. B. Heat pumps are usually rated by their coefficient of performance 7= Q#/W. Find 7 for the ideal case. C. In practice 7× 4. For this 7, find the work actually required.

Principles of Physics: A Calculus-Based Text

5th Edition

ISBN:9781133104261

Author:Raymond A. Serway, John W. Jewett

Publisher:Raymond A. Serway, John W. Jewett

Chapter18: Heat Engines, Entropy, And The Second Law Of Thermodynamics

Section: Chapter Questions

Problem 13P

See similar textbooks

Similar questions

1. Suppose 3,500[J] of work is done on a system, and 4,000[J] of heat flows into the system during this process. What is the change in thermal energy of the system? Express your answer in Joules. 2. The temperature of the air is 25oC. What is this temperature expressed on the Fahrenheit scale? 3. The temperature of a cup of hot coffee is 175oF. What is this temperature on the Kelvin scale? 4. A heat engine operates between energy reservoirs of 75°C and 450°C. What is the maximum efficiency of this heat engine? Express your answer as a decimal, between 0 and 1. 5. A heat engine is operated between two energy reservoirs at different temperatures, where 10,200[J] of thermal energy flows out of the hot reservoir. If the engine has an efficiency of 0.15, what is the work performed by the engine? Express your answer in Joules.
5. (a) How much heat transfer occurs to the environment by an electrical power station that uses1.25 × 10^14 J of heat transfer into the engine with an efficiency of 42.0%? (b) What is the ratioof heat transfer to the environment to work output? (c) How much work is done?
(a) How much food energy will a man metabolize in the process of doing 35.0 kJ of work with an efficiency of 5.00%? (b) How much heal transfer occurs to the environment to keep his temperature constant? Explicitly show how you follow the steps in the Problem—Solving Strategy for thermodynamics found in Problem-Solving Strategies for Thermodynamics.
(a) What is the best coefficient of performance for a refrigerator that cools an environment at 30.0C and has heat transfer to another environment at 45.0C ? (b) How much work in joules must be done for a heat transfer of 4186 kJ from the cold environment? (c) What is the cost of doing this if the work costs 10.0 cents per 3.60106J (a kilowatthour)? (d) How many kJ of heat transfer occurs into the warm environment? (e) Discuss what type of refrigerator might operate between these temperatures.
(5 blanks) What is the maximum possible efficiency (in Percent) of a steam engine working between a hot reservoir at 100 degree celcius and a cold reservoir at 273.15 K? Sol. The equation for maximum possible efficiency is
2. An engine takes in 9000 J and does 1700 J of work each cycle while operating at the temperatures of 650°C and 370°C. a. What is the engine’s actual efficiency? b. What is its maximum theoretical efficiency?
(II) How much less per year would it cost a family to operatea heat pump that has a coefficient of performance of 2.9 thanan electric heater that costs $2000 to heat their home for ayear? If the conversion to the heat pump costs $15,000, howlong would it take the family to break even on heating costs?How much would the family save in 20 years?
10. Five people, all about equal masses, are in a perfectly sealed room in which the air conditioner is operating. The air conditioner removes heat at the rate of 500 kcal/h, maintaining a constant temperature. a) What is the average heat output per hour of each person in the room? b) What is the power rating in watts for an electric light bulb that puts out energy at the same rate as one of the individuals?
3. (a) What is the efficiency of a cyclical heat engine in which 75.0 kJ of heat transferoccurs to the environment for every 95.0 kJ of heat transfer into the engine? (b) How much work does it produce for 100 kJ of heat transfer into the engine?
6. An engine does 10J of work and exhausts 15J of waste heat. (a) what is the efficiency? (b) If the coldreservoir is at 20°C, what is the minimum temperature of the hot reservoir?
i) Define the specific heat capacity with equation? How much thermal energy is required to change a 40 g ice cube from a solid at -10 degrees C to steam at 110 degrees C? ii) A hydraulic jack is used to lift objects such as automobiles. If the input force is 250 N over a distance of 2 m, what will be the output force over a distance of 0.5 m?
Problem 13: Suppose you want to operate an ideal refrigerator that has a cold temperature of -11.5°C, and you would like it to have a coefficient of performance of 6.5. What is the temperature, in degrees Celsius, of the hot reservoir for such a refrigerator? Th = |