Figuring heat exchanger's surface temp

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SUMMARY

The discussion centers on calculating the surface temperature of a heat exchanger using the equation P = εσAT^4, where P represents the power output, ε is the emissivity, σ is the Stefan-Boltzmann constant, A is the surface area, and T is the temperature. The user attempted to rearrange the equation to T = (P/σA)^0.25 but encountered negative temperature results, indicating a misunderstanding of the heating power P. The conclusion emphasizes that the heating power must account for the heat exchange between the heater and the room, suggesting that the reported power may not reflect the actual total heating power of the radiator.

PREREQUISITES
  • Understanding of thermodynamics principles, particularly heat transfer.
  • Familiarity with the Stefan-Boltzmann law and its application in thermal radiation.
  • Knowledge of emissivity and its significance in heat exchange calculations.
  • Basic algebra skills for manipulating equations.
NEXT STEPS
  • Study the Stefan-Boltzmann constant and its role in thermal radiation calculations.
  • Explore heat exchanger design principles and their impact on efficiency.
  • Learn about the concept of thermal equilibrium in heat transfer systems.
  • Investigate methods for accurately measuring heating power in radiators.
USEFUL FOR

Students in thermodynamics, engineers involved in HVAC design, and anyone working with heat exchangers or thermal systems will benefit from this discussion.

TuomasO
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Homework Statement


Calculate surface temp of heat exchanger when it's heating the room with the known power of P. Room temperature T is also known, as is the heater surface area A. ε ≈ 1.

Homework Equations


P = εσAT^4 is what I've been trying to use.

The Attempt at a Solution


I've been trying to solve this with T = (P/σA)^0.25, but that's giving me negative surface temps which clearly can't be correct. I'm guessing the reported heating power P can't be the actual total heating power of the radiator, but I haven't been able to figure out how to go at it.
 
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Your equation is not correct. If the heater radiating heat to the room, then the room is also heat to the heater.
 

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