Heat Loss Through Enclosure Walls Equations and Calculations

Heat Transfer Engineering

Reference: Incropera Fundamentals of Heat and Mass Transfer, Frank P. Incropera and David P. DeWitt

Known Design Data: Size (thickness) of insulated encluosure walls and inside and external surface temperatures

Find: Thickness of walls (insulation material) required to maintain heat load.

Assumptions:

  • Perfectly insulated bottom
  • Steady -state conditions
  • Constant material properties
  • One-dimensional conduction through 5 walls of area (A)

Note: The wall intersection or corners will cause local departures from one-dimensional conduction and a larger heat loss.

Data within boxes variables and can be modified.

  Wall Thickness
  L = m  
 
  Inner temperature
  T1 = °C  
 
  Outer Temperature 
  T2 = °C  
 
  Thermal Conductivity of walls
  k = W/mK  
 
  Width    
  W = m  
 
  Change in Temperature
  T= °C
 
  Heat Flux
  q" = w/m2
 
  Total Area
  Atotal = m2  
         
  Heat Transfer Rate
  q = W  
 
  Thickness of walls (Using Fourier's law)  
  L = m  
   

 

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