I don't know how I got "mysterious energy" in a Carnot heat pump

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Homework Help Overview

The discussion revolves around the operation of a Carnot heat pump, specifically addressing the relationship between work input and heat output to the hot reservoir. Participants explore the implications of the efficiency coefficient and the nature of energy transfer within the system.

Discussion Character

  • Conceptual clarification, Assumption checking, Exploratory

Approaches and Questions Raised

  • Participants examine the equations governing the Carnot heat pump and question how the heat delivered to the hot reservoir can exceed the work input. Some express confusion about the role of the efficiency coefficient and the contributions from the cold reservoir.

Discussion Status

The discussion is active, with participants seeking clarification on the principles of the Carnot cycle and the implications of the equations presented. There is an exploration of different interpretations regarding the energy dynamics involved in the heat pump's operation.

Contextual Notes

Participants reference specific equations from the Carnot refrigeration cycle and discuss the assumptions underlying the efficiency of the heat pump. There is an acknowledgment of the need to consider both the work done and the heat extracted from the cold reservoir.

Philip Robotic
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Homework Statement
Calculate the heat Q_H that a Carnot heat pump can deliver to the reservoir with a temperature T_H. Temperature of lower reservoir (T_L) and work (W, W>0) are given
Relevant Equations
Equations come from Carnot refrigeration cycle
1. |W|=|Q_H|-|Q_L|
2. K=|Q_L|/|W|
So first I transformed the equation no 2 like this:
$$|Q_L|=K\cdot|W|$$
And then I transformed the first equation to find ##|Q_Z|##
$$|Q_L|=|Q_H|-|W|$$
Plugging the result into the first equation
$$|Q_H|=K\cdot |W|+|W|$$
$$|Q_H|=|W|\cdot (K+1)$$
We know that the efficiency coefficient K is greater than 0, so how is it possible that the energy "pumped" into the hot reservoir (##Q_H##) is greater than the work that was put into the system?
 
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Philip Robotic said:
Homework Statement: Calculate the heat Q_H that a Carnot heat pump can deliver to the reservoir with a temperature T_H. Temperature of lower reservoir (T_L) and work (W, W>0) are given
Homework Equations: Equations come from Carnot refrigeration cycle
1. |W|=|Q_H|-|Q_L|
2. K=|Q_L|/|W|

So first I transformed the equation no 2 like this:
$$|Q_L|=K\cdot|W|$$
And then I transformed the first equation to find ##|Q_Z|##
$$|Q_L|=|Q_H|-|W|$$
Plugging the result into the first equation
$$|Q_H|=K\cdot |W|+|W|$$
$$|Q_H|=|W|\cdot (K+1)$$
We know that the efficiency coefficient K is greater than 0, so how is it possible that the energy "pumped" into the hot reservoir (##Q_H##) is greater than the work that was put into the system?
The heat to the hot reservoir is the work that was put into the system plus the heat that is pumped from the cold reservoir.
 
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So I will be able to heat up a certain substance more by using a Carnot Heat Pump than by theoretically converting all the available energy to heat? Do I understand it correctly?
 
Philip Robotic said:
So I will be able to heat up a certain substance more by using a Carnot Heat Pump than by theoretically converting all the available energy to heat? Do I understand it correctly?
There is also energy available from the cold reservoir, and you’re using some of that too.
 
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Did you use the information that it is a Carnot cycle?
 

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