I have the following problem and hope you can help me. I have the setup as shown in the drawing. A pipe that is flowed through, and in the middle of it another pipe, but at the end of this branch is a sensor. Initially the fluid would flow, with a temperature of 25°C. If my thought is correct, the pipe with the sensor (if there is a drain valve) would fill with the liquid and then rest, because there would be no more flow, since it has nowhere to flow.
Now the liquid is slowly heated (heating to about 350°C) and continues to flow the same way. How would the temperature in the branch change? This would have to be still relatively cold at the sensor, since no exchange of the liquid takes place, since no flow is present in the branch, or do I have there a mistake in my thought?
How would you calculate the heat exchange between the flowing and standing medium? Because there is heat exchange only there, which would then have to be "up" through the entire
water column. Can we calculate this in a simplified way as forced convection on a plane wall and assume the fluid portion in the branch as a plane wall?
I hope the problem is apparent, because I would need to calculate the length of the branch so that a certain temperature at the sensor is not exceeded.
Thanks a lot!
So I did a simple Static analysis with a 2meter capillary and the Results are that the temperature is 350 Celsius at the begnning of the capillary And gets cooler in the direction of the senso. After Line 1,5 Meters it cooled down to 25 Celsius. so in coclusion it did not heated all the way thRoug. Capillary is 2 mm in diameter and i put it Under the main pipe
I will post an update as soon as the simulation is finished!
Thanks, as you mentioned i will be using ANSYS for now and simulate the pipe. Thanks for your help!
Hello, welcome to the forum.
I have a little bit different thought process. In my opinion the water column will not stay as it is. The water in the branch would keep on changing. That is new molecules of water will be replaced by old ones consistently even though from outside we see same quantity of water inside the branch.
Reason: First of all, to raise the water in the column there must be a high pressure water which would work against the gravity and stays inside the branch. This high pressure flow creates turbulence(whirls at the bottom of the branch. This results in mixing of molecules.
So, Before the temperature of incoming water is at 25 C entire water will be at 25 C. But when water with 350 C temperature is passed the temperature in the branch will also start raising and after some time entire water temperature in the branch will reach 350 C because of the mixing.
You can confirm this by doing simulation in CFD software like ANSYS, Start CCM+, COMSOL, etc
If you do steady state simulations you will only see the final results but if you do transient simulation you can find the change in temperature with respect to time.