Calculating temp at a time as a mirror looses heat follow'n manufactur

[JJCAB]

Urgent Help Required!

I need to calculate the rate of heat emission from 30 newly formed mirrors 300 mm x 50 mm each. Basically they leave an oven and are at a temperature of 70 Degrees. It then enters a space at 19 degrees. I have a batch of 30 every two minute with a max of ten batches in the room at any one time. So in order to work out my heat load i need to know the temperature of each batch every two minutes until they've reached room temp.

Any ideas?

 

[athomas236]

JJCAB

You need to provide further information such as are the mirrors horizontal or vertical and what is the gap between them

I assume by rate of heat emission you mean heat transfer coefficient.

 

[IRstuff]

Please do not double post.

From your description, they lose 51ºC in temperature. So calculate the net heat lost from the specific heat and temperature delta.

TTFN

 

[JJCAB]

Thanks for the suggestions, in the end i used Newtons law of cooling to predict the temperature of each batch of mirrors up to the point where they had reached room temperature. I had the the factory provide me with a temperature after a given time for a similar manufacturing process. I then calculated the radiation and convection heat transfer coeffients as best i could and used these to calculate the heat emitted at each two minute interval. This gave me the max load in the room at any one time.

 

[8060]

I just want to find out something; can you please describe how you calculated the radiation- and convective heat transfer coefficients? I would really like to know.

 

[chicopee]

This is definitely a late reply but I could not resist putting in my two cents. Altho. you used Newtons cooling law, what you have not indicated is how you treated the temperature gradient inside the mirrors. It appears that your approach was to assume a uniform temp. distribution. To find out if this approach was correct is to determine if the Boit Modulus was < or > 0.1. The significant length within the Boit Modulus is also vital and this is found by calculating the volume of each mirror and dividing this volume by the surface area of he mirror. Hand calculation can be somewhat easily done by hand for uniform temp distribution. For temp gradient you need to do it graphically, or develop a spreadsheet for the so called relaxation method or by using Fortran or Basics for a numerical evaluation.