Contents - Index


SR_16

 

 

Function SR_16(a, b, k) returns the thermal resistance associated with spreading between a circular contact area located on the surface of an infinitely long square flux tube.  The contact area itself is assumed to be exposed to a uniform temperature.  The spreading resistance is the thermal resistance that is in addition to the 1-D thermal resistance in the flux tube that would exist if the uniform temperature was applied over the entire area of the tube.  

 

Note that if a << b then the result approaches the equivalent result for spreading resistance from a half-space given by SR_1.

 

Note that the total resistance associated with conduction through a circular bar of length L with a contact on one end will be the sum of the normal, 1D resistance and the spreading resistance:

 

R_total = L/(k*4*b^2) + SR_16 (SR_16 only calculates the additional resistance associated with spreading that occurs at the end of the bar)

 

 

The calling protocol is:

 

R = SR_16(a, b, k)

 

Inputs:

a = radius of contact area [m or ft]

b = half width of flux tube [m or ft]

k = thermal conductivity of the material [W/m-K or Btu/hr-ft-R]

 

Outputs:

R = spreading resistance [K/W or R-hr/Btu]

 

Rohsenow, W.M, J. P. Hartnett, and Y. I. Cho, Handbook of Heat Transfer, 3rd Edition, McGraw Hill, (1998).

 

Example: 

$UnitSystem SI Mass J K Pa Radian

$VarInfo R16 units=K/W

a=1 [m]

b=2 [m]

k=1 [W/m-K]

R16=sr_16(a,b,k)

 

{Solution:

R16 = 0.1016 [K/W]}

 

 

Spreading Resistance Index