DEFINING THE HEAT TRANSFER PROBLEM 1

[rammtc123]

HI ALL
I HAVE A TIRE CURING PRESS WITH UPPER AND LOWER HOUSING AND THE MOULD. (MOULD 90% IN UPPER HALF AND 10% IN LOWER HALF.THE MOULD IS HEATED AXIALLY BY TWO STEAM PLATENS AND ALSO RADIALLY BY JACKETS.THE MOULD IS SURROUNDED BY 2mm THICK ALUMINIUM SHEET AND THEN BY 40.5mm THICK GLASS WOOL. THE THICKNESS OF UPPER HOUSING IS 25mm.THE SURFACE TEMPERATURE OF MOULD IS AROUND 200 DEG AND AMBIENT AIR TEMP IS 30 DEG. THE MAX SURFACE TEMP ALLOWED AT UPPER HOUSING WAS 40 DEG.

I CONSIDERED THIS AS A STEADY STATE PROBLEM WITH NO INTERNAL HEAT GENERATION AS A COMPOSITE HOLLOW CYLINDER PROBLEM.

I FOUND THAT THE SURFACE TEMP WAS WELL BELOW 40 DEG (37-38 DEG)

BUT IN REALITY THE SURFACE TEMPERATURE IS 65 DEG.

HAVE I DEFINED THE PROBLEM WRONGLY ?, OR ARE MY INPUTS WRONG ?

WHAT ELSE SHOULD I CONSIDER

PLEASE DON'T TAKE ME WRONG AS I'M FRESH GRADUATE WORKING ONLY FOR A MONTH WITH NO ONE TO GUIDE ME.

I WILL EVENTUALLY LEARN . HELP ME TO GIVE A PUSH.

 

[BigInch]

What inputs? You've only described the system, kind of poorly and stated one resulting temperature.

Nobody's going to help you try to do anything that does not have a well described problem and a clear question or two.

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[IRstuff]

> Please refrain from all caps. You should already know that it's tantamount to screaming.
> What's the intent of the exercise? Do you need exact matches, or are qualitative behaviors good enough?
> What was the pedigree of your inputs? Measured? Guessed? Datasheet?

Odd geometries are not amenable to simple calculations. Heat transfer problems are rife with "correlations" which is a polite term for fudge factors that allow you to "correlate" your calculated answer to the measured answer.

TTFN
faq731-376

 

[MintJulep]

You have a heated thing.

So the assumption of no internal heat generation jumps out immediately as being wrong.

 

[rammtc123]

@ Big inch
Thanks for the reply.This is my first post in first forum.You stated that i poorly described the problem.Can you please help me in stating the problem?.What should i provide (drawings,assumptions) etc.I'm new so please guide me.

Thanks in advance

 

[IRstuff]

Pictures, descriptions, numbers. It's not that different than school.

TTFN
faq731-376

 

[rammtc123]

I have attached a pdf.I think that will define the problem more clearly.

These are the inputs that i could get from my superiors.

Please help me

Thanks in advance

 

[MintJulep]

So what is the ambient temperature? 30 or 65? You have now stated both.

It is impossible to lower the ambient temperature by placing a hot thing in the space, yet that is what your PDF is asking for.

Once again, your assumption of no internal heat generation is incorrect.

It's a heat transfer problem, so you are going to need some values that include heat. Temperature is not heat.

 

[willard3]

You should also turn off your caps lock button. My first instinct is not to read posts in caps.

You should also read forum policies:

>>>>>>These fora should not be used to bypass your own in-depth research on the issues that affect you, nor is it intended to >>>>>>>be a substitute for appropriate professional assistance within your field or geographical region.

You need to hire an Engineer who can at least understand the problem and formulate a question.

 

[IRstuff]

This was presumably a learning exercise for you. I think it's time you went to your boss and some him where you've gotten to. You've not provided any details about your calculations, so how do you expect anyone to figure out what your problem is? However, that said, there would be few people here that would be willing to devote the time required to bring you up to speed.

TTFN
faq731-376