What is the minimum power required to operate the heat pump?

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SUMMARY

The minimum power required to operate a heat pump for heating a house with a temperature difference of 40 degrees Celsius (from 27 degrees inside to -13 degrees outside) and a heat loss of 7 kW is calculated using the formula e = Th/(Th-Tc), resulting in an efficiency factor of 7.5. Consequently, the minimum power needed is 933 W, derived from the equation W = 7000/7.5. The discussion emphasizes the importance of maintaining proper units throughout calculations to avoid confusion.

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  • Understanding of thermodynamics, specifically the principles of heat transfer.
  • Familiarity with heat pump operation and efficiency calculations.
  • Knowledge of temperature scales and conversions.
  • Basic algebra for manipulating equations and solving for variables.
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Engineers, HVAC professionals, and students studying thermodynamics or energy efficiency in heating systems will benefit from this discussion.

swain1
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Homework Statement


It is proposed to heat a house using a heat pump operating between the house (27 degees) and the outside (-13 degrees). The heat loss from the house is 7kW. What is the minimum power required to operate the heat pump?

Homework Equations


The Attempt at a Solution


e=Th/(Th-Tc) =7.5
W=7000/7.5 =933 W

Just checking if this is correct or have I made a mistake. Thanks
 
Last edited:
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Since you start out with a dimensionless number, a ratio of temperatures, and equate that to some number of Watts, something is surely wrong. Maybe you just need to rewrite things to make it clear
 
I have moved the equation now. If you look at the question you will see that 7000 has units of watts. Is it wrong anyway?
 
swain1 said:
I have moved the equation now. If you look at the question you will see that 7000 has units of watts. Is it wrong anyway?

That looks better. It would be better still if you had units of W on the 7000.
 

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