Temperature gradient along a pipe with no fluid transmission.

[SAK9]

We are installing a biowaste tank which uses steam to kill the waste. The vessel is heated to about 135 C.for approximately an hour and then emptied.The waste pipe into the tank is of poly propelene(PP) of 150mm dia.Two metere away from the tank the PP pipe stops and thereafetr the material is stainless steel of 150 mmdia.PP pipe can withstand upto 60C only.what is the equation to calculate the the temperature at the joining point of PP and stainless steel pipe? The pipes are not insulated.The room temperature is about 25C.When the tank is heated there is no flow into the tank ie heat transmission will be along the pipe wall only.

 

[CRG]

I have seen no single equation to solve the multidimensional heat transfer problem you have stated. I would estimate the temp by making conservative assumptions to simplify the solution method.

Pick a reasonable average pipe temperature for heat transfer from the pipe to the ambient. This average temperature will be changed later through an iterative solution method. Use single dimensional heat transfer methods for calculation.

Look at the single dimensional heat flow down the pipe using cross-sectional area of the pipe. Again you must choose a reasonable temperature for the unknown end of the pipe. This too will be changed later through iterations.

Look at the convective heat flow of the media inside the pipe.

Once you have established the means and methods for calculating the three heat transfer cases, you should be able to iterate the assumed temperatures for each solution by using an energy balance for the heat flows. If you are proficient with heat transfer calculations, this will tell you how big of concern you should have. If the numbers are close to your material limits, a more rigorous solution method would need to be employed (FEA or make a physical model).

 

[hacksaw]

that situation is commonly encountered in manufacturing

the issue is typically reduced to a design problem of isolating the two piping systems either with piping design and materials selection, isolation valving, etc.

condensation from the heated contents of your sterilizaton vessel is likely to exceed (greatly) the pipe wall conduction. you have to design accordingly.