Heat Loss of uninsulated capsule

  • #1
Hello,

I am trying to calculate the heat loss of a capsule (mini submarine), size is 6m long and 0.5m radius of the ends and a height of 3m. I found a formula for calculating heat loss but it requires an R-value which I don't have, H = A(Thot-Tcold)/R (I'm guessing this is for insulated bodies)

The tank is uninsulated. I got some numbers using a Thermal Imaging Camera, Min temperature is 25 degC and Max is 114 degC. The emissivity is 0.95. The water inside the tank is heated using steam from about 20 degC to 120 degC. Ambient temperature is 25 degC.

I have been at it for 2 days now and can't get anywhere, maybe I'm looking at this the hard way. Is there a simply formula for heat loss of uninsulated bodies? Will the emissivity be used in this calculation?

Any help is greatly appreciated.

Thanks
 

Answers and Replies

  • #2
Simon Bridge
Science Advisor
Homework Helper
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Your formula assumes that the conduction of heat through the minisub walls is less than 100%.
You can think of an uninsulated body as an insulated body with very poor insulation if you like. Otherwise you are using a direct cooling model where the heat flow where the change in temperature depends on a function of the temperature - depending on how good your convection is.

Your emmissivity shows that you do loose heat by radiation.
The formula you have is for conduction through the walls.
A complete model will include conduction, convection, and radiation.
 
  • #3
Thanks for your reply Simon. The capsule is actually a textile dyeing machine. What value would you use for a poor insulation?

I came across this Formula on a Tyco article:

Tank Heat Loss

1) Calculate Surface Area, Av
2) Calculate Qv (heat loss through insulated tank body)
Need:
* Maintain Temperature (Tm)
* Minimum Ambient Temperature (Ta)
* Insulation Thickness
i) ΔT = (Tm) - (Ta)
ii) Find Heat Loss Rate, qv (this was provided in a table)
iii) Find Insulation Adjustment Factor

Now, Calculate Heat Loss through Tank Body
Qv = (Av) x (qv) x (Insulation Adjustment Factor)

3) Heat Loss through base support and Accessories

4) Finally, calculate overall heat loss, Qt
Qt = (Qv + Qs + Qa)
or Qt = (Qv + Qs + Qa) x 0.9, if indoor



Now, assuming I can use the above formula, I have a few questions:

1 - Is maintain temperature the same as operating temperature, i.e. when machine has reached the maximum temperature required for the process?

2 - What size insulation should I use when determining 'Heat Loss Rate' (2 ii) as in the table provided it starts with 1" and goes up to 4"?

3 - What insulation 'type' should I pick when determining Insulation Adjustment Factor?


This is the website btw:
http://www.tycothermal.com/assets/Americas/English/Document/Product%20Design%20and%20Selection%20Guides/1670/H56887_th_0806.pdf [Broken]

Thanks
 
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