The motor that drives a reversible refrigerator produced 142 W

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SUMMARY

The discussion centers on calculating the maximum amount of ice that can be produced by a reversible refrigerator motor with a power output of 142 W, operating between heat reservoirs at 20°C and -6.1°C. The efficiency of the refrigerator was calculated as 0.089 using the formula e=1-Tc/Th. The problem requires determining the maximum heat flow from the cold reservoir over a period of 2.2 hours and relating it to the heat required to freeze water initially at 6.0°C.

PREREQUISITES
  • Understanding of thermodynamics, specifically the concepts of heat flow and efficiency.
  • Familiarity with the Kelvin temperature scale and temperature conversions.
  • Knowledge of the heat of fusion for water and the phase change from liquid to solid.
  • Ability to apply the equation ΔS= Q/T in thermodynamic calculations.
NEXT STEPS
  • Calculate the total heat flow from the cold reservoir over 2.2 hours using Q = P * t.
  • Research the heat of fusion for water to determine the amount of energy required to freeze water.
  • Learn about the Carnot cycle and its implications for the efficiency of refrigeration systems.
  • Explore practical applications of reversible refrigerators in real-world scenarios.
USEFUL FOR

This discussion is beneficial for students studying thermodynamics, engineers working with refrigeration systems, and anyone interested in the principles of heat transfer and energy efficiency in cooling technologies.

warrior2014
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Homework Statement



The motor that drives a reversible refrigerator produced 142 W of useful power. The hot and cold temperatures of the heat reservoirs are 20°C and -6.1°C. What is the maximum amount of ice that can produce in 2.2 hours from water that is initially at 6.0°C?

Homework Equations



ΔS= Q/T


The Attempt at a Solution



I converted the temperatures into K, so 20°C= 293 K and -6.1°C= 266.9 K.
I found the efficiency using e=1- Tc/Th= 1- (266.9/293)= 0.089

after this, I am unsure how to solve the problem. Please help! thank-you :)
 
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warrior2014 said:

Homework Statement



The motor that drives a reversible refrigerator produced 142 W of useful power. The hot and cold temperatures of the heat reservoirs are 20°C and -6.1°C. What is the maximum amount of ice that can produce in 2.2 hours from water that is initially at 6.0°C?

Homework Equations



ΔS= Q/T


The Attempt at a Solution



I converted the temperatures into K, so 20°C= 293 K and -6.1°C= 266.9 K.
I found the efficiency using e=1- Tc/Th= 1- (266.9/293)= 0.089

after this, I am unsure how to solve the problem. Please help! thank-you :)
You don't have to worry about entropy at this stage. You have to determine the maximum amount of heat flow from the cold reservoir in 2.2 hours and relate that to the amount of heat flow that must be removed from the water to make a unit (eg a gram or kg) of ice to determine the units of ice made.

AM
 

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