zappedagain
Electrical
This thread is branched from
Nice thread! I'm looking for the static heat rise of a hand held enclosure, so let me see if I have this correct:
Tia = inside air temp
Tis = inside surface temperature
Tos = outside surface temperature
Tamb = ambient temperature
and
There is a heat transfer rate Q1 defined by the heaters
There is a heat transfer rate Q2 defined by the pair T1a---Tis
There is a heat transfer rate Q3 defined by the pair Tis----Tos
There is a heat transfer rate Q4 defined by the pair Tos---Tamb
The 3 equations:
Q1=Q2
Q2=Q3
Q3=Q4
Q1 - power dissipated in the enclosure
Q2 - temperature rise in the box (this has a positive relationship to the thermal resistivity of the object dissipating the power, correct?). Q2=mc delta T (heat = mass *specific heat constant of air * change in temperature), correct?
Q3 - If I ignore radiation, this is defined by the thermal conductivity of the enclosure, correct?
Q4 - How would I calculate this for a given volume, such as a 2"x2"x2" box? Is there some estimate I can use for a ballpark number?
Set Q1=Q2=Q3=Q4 and the result is a ballpark temperature for Tia, Tis, and Tos, correct?
As I'm ignoring radiation (it should lower the temperature as long as I don't have an external heat source, so this is worst case). Are there other parameters that I might want to include?
Thanks,
John D
Nice thread! I'm looking for the static heat rise of a hand held enclosure, so let me see if I have this correct:
Tia = inside air temp
Tis = inside surface temperature
Tos = outside surface temperature
Tamb = ambient temperature
and
There is a heat transfer rate Q1 defined by the heaters
There is a heat transfer rate Q2 defined by the pair T1a---Tis
There is a heat transfer rate Q3 defined by the pair Tis----Tos
There is a heat transfer rate Q4 defined by the pair Tos---Tamb
The 3 equations:
Q1=Q2
Q2=Q3
Q3=Q4
Q1 - power dissipated in the enclosure
Q2 - temperature rise in the box (this has a positive relationship to the thermal resistivity of the object dissipating the power, correct?). Q2=mc delta T (heat = mass *specific heat constant of air * change in temperature), correct?
Q3 - If I ignore radiation, this is defined by the thermal conductivity of the enclosure, correct?
Q4 - How would I calculate this for a given volume, such as a 2"x2"x2" box? Is there some estimate I can use for a ballpark number?
Set Q1=Q2=Q3=Q4 and the result is a ballpark temperature for Tia, Tis, and Tos, correct?
As I'm ignoring radiation (it should lower the temperature as long as I don't have an external heat source, so this is worst case). Are there other parameters that I might want to include?
Thanks,
John D