Calculating temperature rise
Calculating temperature rise
(OP)
Any assistance will be greatly appreciated!
How do I calculate the following?
If I apply a thermal load of 70 watts to 110 cubic inches of aluminum alloy, what is the approx temperature rise above ambient in degrees C.
How do I calculate the following?
If I apply a thermal load of 70 watts to 110 cubic inches of aluminum alloy, what is the approx temperature rise above ambient in degrees C.






RE: Calculating temperature rise
time?
Is this for a class?
TTFN
RE: Calculating temperature rise
I am dissipating 70 watts continuously within this enclosure.
What would be the temperature of the outer skin of this enclosure above the ambient air temperature of the surrounding environment?
The approx volume of the enclosure material (aluminum) is 110 cubic inches.
This is a real world problem that I’m looking for assistance on, not a class problem.
Any help would be appreciated.
RE: Calculating temperature rise
What is the ambient air temperature and air flow? Are there hotspots? What's it resting on? Will heat be removed through the bottom? Which dimensions correspond to W*H*D?
TTFN
RE: Calculating temperature rise
No hot spots, uniform heat distribution.
Not resting on any surface, I would like to discount the small mounting interface from the equation.
Heat removed by natural convection.
17W*22D*6H.
RE: Calculating temperature rise
RE: Calculating temperature rise
I did the calculation based on a simple heat balance and a coef. of heat transfer of 1. Numbers vary slightly if you tweak h or emmissivity slightly. Also, the assumption is that the heat load is uniformly distributed on the interior surfaces.
RE: Calculating temperature rise
A.side:2*6*in*(17in+26in)=0.3019*m^2 h.cside:2.5W/m^2/ºC
ignore bottom
input:70W deltaT=40.6978ºC
This would put the surface temperature at 67ºC, which is hot enough to be a serious skin burn hazard.
Radiative power is only about 14mW at this temperature.
TTFN
RE: Calculating temperature rise
ko (www.ecooling.biz)
RE: Calculating temperature rise
The temp is only 39ºC if the box is perfectly emissive. A 70% emissive box raise the temperature to 59ºC
TTFN
RE: Calculating temperature rise
39ºC with 47 W radiated
TTFN
RE: Calculating temperature rise
RE: Calculating temperature rise
I stand corrected! These are my corrected values:
1) e=.05, Delta T=36.8 deg C, Qrad=4.8, Qconv=65.2
2) e=.95, Delta T=18.6 deg C, Qrad=42.2, Qconv=27.8