Convection from a braided hose
Convection from a braided hose
(OP)
Hello all,
I'm attempting to work through a heat transfer problem and I was hoping to get some advice and clarity about how to model it.
I have a corrugated, double-braided SS tube carrying hot (500-800degC) gas at about 30 bar over a length of a few meters. Tube motion is minimal, so it is just sitting in standard conditions. The purpose of the calculation is to estimate temperature drop in the gas and figure out how much insulation we need to minimize it.
So I have a few heat transfer conditions. From the gas to the tube is forced convection, then conduction through the tube, then free convection to surrounding air from the outer tube surface.
The way I was thinking of approaching this was taking a small length of hose, assuming that its surface temp was equal to gas temp, and determining what the rate of heat transfer to surroundings would be, removing that energy from the gas, and then iterating that method for the full length (i.e. the temperature of the gas at the outlet of my first small length of pipe would be the new assumed surface temp of the next small length of pipe).
The thing I'm not sure about is where free vs. forced convection comes in. Does the fact that convection is free on the outside of the tube mean that the total heat transfer is limited to that rate, or does the turbulent, high temp. flow inside the tube mean that the rate of heat transfer to the surroundings is higher?
I'm attempting to work through a heat transfer problem and I was hoping to get some advice and clarity about how to model it.
I have a corrugated, double-braided SS tube carrying hot (500-800degC) gas at about 30 bar over a length of a few meters. Tube motion is minimal, so it is just sitting in standard conditions. The purpose of the calculation is to estimate temperature drop in the gas and figure out how much insulation we need to minimize it.
So I have a few heat transfer conditions. From the gas to the tube is forced convection, then conduction through the tube, then free convection to surrounding air from the outer tube surface.
The way I was thinking of approaching this was taking a small length of hose, assuming that its surface temp was equal to gas temp, and determining what the rate of heat transfer to surroundings would be, removing that energy from the gas, and then iterating that method for the full length (i.e. the temperature of the gas at the outlet of my first small length of pipe would be the new assumed surface temp of the next small length of pipe).
The thing I'm not sure about is where free vs. forced convection comes in. Does the fact that convection is free on the outside of the tube mean that the total heat transfer is limited to that rate, or does the turbulent, high temp. flow inside the tube mean that the rate of heat transfer to the surroundings is higher?





RE: Convection from a braided hose
RE: Convection from a braided hose
RE: Convection from a braided hose
Then I fit an exponential decay to those two points with the variable being the length in cm. Can anyone comment on how close that would be to actual?
RE: Convection from a braided hose
you can simulate this as a pipe in 3E Plus. You can download that for free.
It says for personell protection you need 5.5" of high temperature blanket to get the surface temp down to 140F.
Regards
StoneCold
RE: Convection from a braided hose
RE: Convection from a braided hose
RE: Convection from a braided hose
RE: Convection from a braided hose
The 3E software does what I was trying to do anyway, which is figure out insulation thicknesses, so my own HT equations don't have to be fantastically accurate.