Question about thermodynamics (heat loss)

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SUMMARY

The discussion centers on calculating the power requirement for an air conditioner in a poorly insulated house using thermodynamics principles. The house has walls with a thickness of 0.25m, a total surface area of 210m², and a thermal conductivity of 1.3 W/m·K. The user calculated the heat transfer rate using the formula dQ/dt = ak(dT/dx) and arrived at a value of 16380 W for the air conditioner’s power requirement. The problem is identified as a classic 'Carnot refrigerator' scenario, emphasizing the need to first determine the heat leakage through the walls.

PREREQUISITES
  • Understanding of thermodynamics principles, specifically heat transfer.
  • Familiarity with the Carnot cycle and refrigerator concepts.
  • Knowledge of thermal conductivity and its implications in building insulation.
  • Ability to apply the heat transfer equation dQ/dt = ak(dT/dx).
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  • Learn about thermal insulation materials and their thermal conductivity ratings.
  • Explore advanced heat transfer calculations in building physics.
  • Investigate methods to improve insulation and reduce heat loss in buildings.
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Students studying thermodynamics, engineers involved in HVAC design, and homeowners seeking to understand energy efficiency in residential buildings.

vande060
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Homework Statement


Suppose that you own a poorly insulated small house, with outside walls l = 0.25m thick, total outer wall plus roof
surface area 210m^2 (about 1992 ft^2) and your walls have a thermal conductivity of 1.3 W/m·K (limestone). Calculate
how much power your air conditioner will require to keep your house at 293K when the outside temperature is 308K.

Homework Equations



maybe dQ/dt = ak(dT/dx)

The Attempt at a Solution



i think

(1.3)(210)(15/.25) = 16380 W

but what do you think? have i made errors?
 
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This is a classic 'Carnot refridgerator' problem...

EDIT: Maybe this will help.

http://www.ohio.edu/people/piccard/phys202/carnot/carnot.html

Find an expression for the heat leakage first(through the walls).
 
Last edited:

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