Calculation of pipeline heat loss
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Could everyone help me calculate this? My supervisor asked me to figure out something: for a DN1000 pipe that is 1000 meters long and filled with air at 200°C, it takes how long for this pipe to reach the ambient temperature of -20°C, assuming the pipe is made of carbon steel and has no insulation. I hope someone experienced can provide an equation or some guidance on how to carry out this calculation
You need to know the thermal conductivity of carbon steel
First, calculate the total heat in the air duct, and then determine the heat loss per meter of the air duct, paying attention to the unit conversions. But it seems that in your data, the heat is lost entirely after traveling 1000 meters, as it’s a dynamic process.
For this problem, it is recommended to use a segmented calculation approach: assume segments of 50m each, assume the temperature remains constant, calculate the heat dissipation (Q=KAΔt), and then determine the exit temperature for that segment; repeat this process. Excel can be used for calculations.
By taking a derivative along the length of the pipe and considering the thermal equilibrium over a unit length, it is possible to determine the pipe length; the time can then be calculated based on the flow velocity
I agree with the views expressed on floors 4 and 5 above; given that the pipeline in LZ’s case is relatively long, a segmented heat balance calculation method can be used to solve the problem
The pipe is simply filled with air at 200°C, but it doesn’t flow