Heat Loss in Pipe-Fluid Not Moving
Heat Loss in Pipe-Fluid Not Moving
(OP)
Hey,
I am trying to calculate heat loss of a fluid in a pipe where the initial temperature of the fluid in the pipe is greater than ambient temperature. The pipe is open to the atmosphere. The tubing is not insulated. The fluid is not flowing in the pipe, just sitting there.
I am assuming there is no forced convection in this fluid since the Re number would be 0. So I found two correlations to calculate the Nu number for free convection (turbulent and laminar flow). Could I just use the laminar flow correlation (from Churchill and Chu "Correlating Equations for Laminar and Tubular Free Convection from a Horizontal Cylinder) to calculate this heat loss.
Is there another method for this calculation?
Thanks.
I am trying to calculate heat loss of a fluid in a pipe where the initial temperature of the fluid in the pipe is greater than ambient temperature. The pipe is open to the atmosphere. The tubing is not insulated. The fluid is not flowing in the pipe, just sitting there.
I am assuming there is no forced convection in this fluid since the Re number would be 0. So I found two correlations to calculate the Nu number for free convection (turbulent and laminar flow). Could I just use the laminar flow correlation (from Churchill and Chu "Correlating Equations for Laminar and Tubular Free Convection from a Horizontal Cylinder) to calculate this heat loss.
Is there another method for this calculation?
Thanks.





RE: Heat Loss in Pipe-Fluid Not Moving
"So I found two correlations to calculate the Nu number for free convection (turbulent and laminar flow)." This is confusing to me. Did you mean natural convection when you said free convection? If so, there should be no flow or velocity components to input to those correlations, because natural convection is for no forced flow situations. The only flow that occurs during natural convection is due to temperature and density differences. Use a relavent natural convection correlation.
Good luck,
Latexman
RE: Heat Loss in Pipe-Fluid Not Moving
Anyone have any good correlations for this type of problem?
Thanks again.
RE: Heat Loss in Pipe-Fluid Not Moving
Do you really mean rate of heat transfer? This will not be constant, being a function of delta T.
RE: Heat Loss in Pipe-Fluid Not Moving
You can find your answer in this book
http://web.mit.edu/lienhard/www/
page 416
Good luck
RE: Heat Loss in Pipe-Fluid Not Moving
But wouldn't I use this equation since the flow is neither Laminar or Turbulent:
Q=(Delta T)/[(1/h*A)+(LN(ro/ri)/(2*pi*k*L))]
Now do I use the equations for the Nu number to find h(convective coefficient) or do I just ignore convection for the heat loss estimate? (Can estimate average wind speed). I have already ignored convection through the silicone fluid.
Thanks
RE: Heat Loss in Pipe-Fluid Not Moving
Thanks.
RE: Heat Loss in Pipe-Fluid Not Moving
MintJulep is right. This is an unsteady-state heat transfer situation, since ΔT is bound to drop with time.
RE: Heat Loss in Pipe-Fluid Not Moving
Good luck,
Latexman
RE: Heat Loss in Pipe-Fluid Not Moving
Good luck,
Latexman
RE: Heat Loss in Pipe-Fluid Not Moving
RE: Heat Loss in Pipe-Fluid Not Moving
Thanks, now if there was flow of the silicone in the pipe. I would just use the correlations to find the convective heat transfer coefficient for the inside correct?
Thanks for all the responses.