heat exchange between a tube and a box

Nov 2019
The problem is very easy but i cannot figure it out.

I have a tube of L length, Dext and Dint. The tube is in a box of x,y,z dimensions.
The box has a constant temperature of 37°C and it is full of water. The tube is inside the box and in the tube there is a flow of water. The Tin of the tube is 20 °C and the Tout should be 35 °C.

Can I dimension the box and the tube?

Thanks a lot
Jun 2016
Do you have the thermal conductivity of the tube?
(or can you perhaps assume this is high enough to be ignored for this problem).
But then you also have to consider the thermal conductivity of the water.
Start off with a 2D static approximation, how long will it take a 2D slice through the pipe (starting at 20 °C) to reach 35 °C.
Then given the water flow rate through the pipe, the time taken to flow through the pipe should equal the time you found in your 2D approximation.
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