# Heat transfer rate to heating time

1. Aug 6, 2008

### gemt

i have set up an equation to get the heat transfer rate Q for a combined system where heat is transfered from a cylindrical outer wall set at 500 C. the wall heats a gas, which in turn heats a solid block of cylindrical metal positioned in the centre of the heated walls with a starting temperature of 20 C.

the equation i have is

Q=[1]\frac{}{}[/(A0/(h*Alm1))+((r*A0)/(k*A2))+(A0/(h*Alm3))+((r*A0)/(k*A4))+(A0/(h*Alm5))]*A0*$$\Delta$$T

and it give a result of 11.3213 Watts or the situation above.

but too me this seems small?? am i right in thinking this?

also can anyone tell me how i can relate this heat transfer to time. ie. know how long it would take to heat the central metal part.

2. Aug 10, 2008

### quark1005

could you fix the latex?

3. Aug 11, 2008

### gemt

i could not get the equation editor to work properly (probaly the user to be fair) but i am included a hand written version as an attachment. i have managed to modifie it a bit which is giving me more sensible answers. But to get a value for time (in seconds#) i am using the below equation to get a value for q in joulse and then dividing q by Q.

q=cm$$\Delta$$T

c = specific heat of the gas
m = mass of gas
delta T = the change in temperature

Thanks

#### Attached Files:

• ###### equation1.bmp
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4. Oct 17, 2008

### riscy

Hi, can you send me eveything about this equation including details the of model, description of the variable and sketch, I will look into this.....