asking a simplified question from the one yesterday. hopefully, if somebody can answer this, then i will be closer to answering the harder one, and this one does apply to my system.
lets assume
in my heat exchanger i will have 50 PSI of steam which equates to a approx internal boiler temp of 281 F.
the specific heat of the heat transfer fluid is .71 Btu/lb F at this temperature.
assuming a 1/8" stainless steel pipe thickness that is 24'' long with a .5" diameter which has a thermal conductivty of 18W/m-K will be transporting the heat transfer fluid,
what is the heat transferred?
You are American aren't you? I'm not going to answer the question (sorry bout that), but what is with those units?! How can you possibly get anywhere with the problem using scrambled egg units like that?
i am indeed american. and yes the units are scambled. from trying to learn this stuff i am typically working in meters, kelvin, and watts. and my final answer is BTUs.
i rather not like meters either, i should probably look at working in good ole BTUs, ft, and F.
i rather not like meters either, i should probably look at working in good ole BTUs, ft, and F.
Being a filthy leftie European, I would strongly recommend using SI units. They are defined a lot better and work together far better than imperial units, where I imagine you'd end up confusing yourself a lot.
If you haven't got much intuition for SI units, then just think of 1m as 1 yard and 1 kg as 2 lb and you won't be far wide of the mark.
Of course, the only system of units that is ever used in HEP is natural units. c = h bar = 1 (sometimes = i = pi if you aren't careful
)
If you haven't got much intuition for SI units, then just think of 1m as 1 yard and 1 kg as 2 lb and you won't be far wide of the mark.
Of course, the only system of units that is ever used in HEP is natural units. c = h bar = 1 (sometimes = i = pi if you aren't careful
)
Hi all!
Units: each time one writes hbar for h/2pi, I read hectobar... The unit I used for material strength (together with daN and mm2) before I began computing resonance frequencies, which messed all up. Since then, SI, again SI, and only SI for me; even if they are often too big or too small or have g=9.81 too different from 1, they are the only consistent ones.
Simplified problem: only half-way simplified...
On the boiling side, it's simple. You have at the surface of the metal the temperature of the liquid-vapour equilibrium, quite precisely, because boiling liquids absorb huge power densities with almost no temperature loss. For instance, I could absorb the full power density of a blow torch, something like 100kW on one cm2, on a copper foil tub filled with water. Which also tells that this flame radiates its heat instead of conducing it; consistent with calculations.
But on the heat transfer fluid side, your problem remains as complicated as in the other post. You really need to go through the complicated process of Reynolds number and co. Bad luck.
This could be a beginning:
http://en.wikipedia.org/wiki/Convective_heat_transfer
http://en.wikipedia.org/wiki/Heat_exchanger
textbooks are cited.
Units: each time one writes hbar for h/2pi, I read hectobar... The unit I used for material strength (together with daN and mm2) before I began computing resonance frequencies, which messed all up. Since then, SI, again SI, and only SI for me; even if they are often too big or too small or have g=9.81 too different from 1, they are the only consistent ones.
Simplified problem: only half-way simplified...
On the boiling side, it's simple. You have at the surface of the metal the temperature of the liquid-vapour equilibrium, quite precisely, because boiling liquids absorb huge power densities with almost no temperature loss. For instance, I could absorb the full power density of a blow torch, something like 100kW on one cm2, on a copper foil tub filled with water. Which also tells that this flame radiates its heat instead of conducing it; consistent with calculations.
But on the heat transfer fluid side, your problem remains as complicated as in the other post. You really need to go through the complicated process of Reynolds number and co. Bad luck.
This could be a beginning:
http://en.wikipedia.org/wiki/Convective_heat_transfer
http://en.wikipedia.org/wiki/Heat_exchanger
textbooks are cited.