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Heat loss

  1. Feb 20, 2016 #1
    1. The problem statement, all variables and given/known data
    Hello everyone, I hope that you guys could lend me a hand.
    I need to calculate the heat loss at any point over a long pipe while considering lambda of the pipe. I am trying to use octave to find a reasonable flow-rate to keep the temperature loss to a minimum at a reasonable pressure.

    lambda= 0.02
    inner radius=0.1m
    outer radius=0.2m
    Distance=4000m
    initial inside temperature 100C
    outside temperature=10C

    Assumptions:
    laminar flow.
    no vertical variations.


    2. Relevant equations


    3. The attempt at a solution
    %Heat loss long distance transfer
    %Initial Settings
    PipeRadiusInside=0.1;
    PipeRadiusOutside=0.2;
    TotalPipeDistance=1000;
    Time=1;
    PipeSegmentLength=16;
    OutsideTemperature=10;
    InsulatingCapacity=0.020;
    Temperature=[];
    CurrentTemperature=100;
    i=0;
    %%
    PipeThickness=PipeRadiusOutside-PipeRadiusInside;
    Resistance=((PipeThickness*log(PipeRadiusOutside/PipeRadiusInside))/InsulatingCapacity); U=1/Resistance;
    TemperatureDifference=CurrentTemperature-OutsideTemperature; SegmentVolume=2*pi*PipeSegmentLength; EnergyOfWater=4.2*TemperatureDifference*SegmentVolume*0.9982;
    while i<TotalPipeDistance/Time i=i+PipeSegmentLength; Temperature=[Temperature CurrentTemperature]; HeatLoss=2*pi*PipeRadiusOutside*U*TemperatureDifference*PipeSegmentLength; EnergyOfWater=EnergyOfWater-HeatLoss; CurrentTemperature=((EnergyOfWater-HeatLoss)/(4.2*SegmentVolume*0.9982))+OutsideTemperature; TemperatureDifference=CurrentTemperature-OutsideTemperature;
    end plot(Temperature)


    It gives me results which look like the could be right as it reacts to changes in variables correctly but it is definitely incorrect. Also I do not know how to relate it to flow rate.
    I really need help and would be thankful for an example.

    Thank you for your time.
     
  2. jcsd
  3. Feb 20, 2016 #2

    SteamKing

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    Staff Emeritus
    Science Advisor
    Homework Helper

    Does lambda have any units associated with it?
     
  4. Feb 21, 2016 #3
    Yes. Sorry I forgot to mention that. (w/mK)
     
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