How to calculate outside surface temperature of a metal box with hot air flowing through it
How to calculate outside surface temperature of a metal box with hot air flowing through it
(OP)
First off, I want to apologize for the elementary nature of this question. It has only been about 13 years since I did any heat transfer/thermo type calculations.
I have a boxed in area with a know inlet and outlet. I have a flow rate (in CFM) and temperature of the heated air entering this box, as well as, the ambient temperature of the surroundings. The box is made of steel. I need to determine the surface temperature of the outside of the box.
Any guidance is greatly appreciated.
NB
I have a boxed in area with a know inlet and outlet. I have a flow rate (in CFM) and temperature of the heated air entering this box, as well as, the ambient temperature of the surroundings. The box is made of steel. I need to determine the surface temperature of the outside of the box.
Any guidance is greatly appreciated.
NB





RE: How to calculate outside surface temperature of a metal box with hot air flowing through it
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RE: How to calculate outside surface temperature of a metal box with hot air flowing through it
RE: How to calculate outside surface temperature of a metal box with hot air flowing through it
RE: How to calculate outside surface temperature of a metal box with hot air flowing through it
You can spend a lot of effort and dollars trying to get all the approximations "just right", and not need that much accuracy in the real world. Or go measure a similar facility with an IR thermometer, about 60.00 at the hardware store. 1/2 hour of design time. 8<)
RE: How to calculate outside surface temperature of a metal box with hot air flowing through it
Thanks again for all the replies!!
RE: How to calculate outside surface temperature of a metal box with hot air flowing through it
SAE AIR 1168-4 Ice, Rain, Fog, and Frost Protection has the information on how to keep surfaces ice free. If your air is really 510C, I doubt that anything will stick, except for waxy substanaces and styrofoam-like materials, since they'll actually melt onto the box.
What is the purpose of all this?
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RE: How to calculate outside surface temperature of a metal box with hot air flowing through it
Tunalover
RE: How to calculate outside surface temperature of a metal box with hot air flowing through it
RE: How to calculate outside surface temperature of a metal box with hot air flowing through it
RE: How to calculate outside surface temperature of a metal box with hot air flowing through it
Tunalover
RE: How to calculate outside surface temperature of a metal box with hot air flowing through it
Heat loss across the thin box wall is almost neglibile compared to all of the rest.
What you are describing is a simple very hot box with an interior gas temperature of 510 C ENTERING at one side at 510 C and leaving at something quite a bit lower at the other side. The low gas flow rate (because it is only an exhaust) and relatively low speed in the large box increase heat loss from gas to the four box walls and floor and supports and outside air under, around and over the box walls.
The four box walls will lose heat by convection to the air differently on the bottom, sides and top because of natural convection flow rates differ in the three locations. No outside fan, right?
The four walls will have radiation losses different on the bottom, sides, and top because of the different wall temperatures. Further, on each side => with different radiation losses up the sides of the two walls are to the 4th power, the sides will not have a uniform radiation loss vertically. The side walls will probably have a single emissivity, but it will be different than the top and the bottom walls because of different dirt and paint layers over time.
Conduction gains will occur from upstream back from the engine (unless it is isolated by a flex hose connection or long pipe from the manifold), but will have conduction losses at each box support and the outlet assembly.
Your heat "gain" to the wood particles in some container above the box will have to be evaluated in the same manner as the heat heat losses from the box.
You somehow were thinking in the original question that the heat was simply transmitted from gas to wood through a simple box wall, and that heat loss was the entire part of your problem. You don't even know the wall temperatures of the top of the box yet.
What assumptions have you made for heat transfer from bottom-of-wood container up to the irregular wood particles?