If you are changing from one metal to another, then the change may not be that great. Of you are changing from a metal to graphite or something that is not a good conductor, then you will probably see a difference.
The main driver on heat transfer is the boundry layer on the tubes, not necessarially the tubes themselves. If you have low turbulance or laminar flow in your heat exchanger, then the material of the tubes will probably not be noticable since the boundry layer efffects will be very high. If you have a high reynolds number, then the resistance of the tube material may come into play as the resistance to heat transfer is much reduced in the boundry layer.
My experience is that the smallest resistance in heat transfer is the tube itself, therefore changing material probably will not change performance much and may in fact not be noticible at all.
Depends on the delta T. At high delta T the resistance due to tube material is pretty insignificant, at low delta T the tube resistance may become a small factor. Flow rate, convection, and turbulance are much more important issues.
__________________
Eventually, one needs to realize that it is far less important to be the smartest person in the room than it is to sit next to that person and make friends.
as an example, consider two exchangers provided with tubes respectively made on carbon steel and stainless steel. Thermal conductivity of carbon steel is about three time the stainless steel one. Under same conditions of flowrates, in/out temperatures, kind of involved fluids and thermal duty, U-factor of carbon steel case is higher than stainless steel one, up to two time if fouling factors are very low.
You can check it after an easy theoretical calculation.
Consider a hypothetical tube made of a metal, and replace it with a hypothetical tube of similar dimensions made of, well let's take an example material, expanded polystyrene. The heat transfer rate depends on the thermal conductivity of the material, and will, in this hypothetical situation, be much greater for the metal tube on account of its greater thermal conductivity.
Is this going in the right direction?
__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Presuming the hypothetical expanded polystyrene has similar structural strength, heat exchanger tubes are usually relatively thin, on the order of 0.025 to 0.10" thick. Heat transfer losses from conduction through thin materials are usually low. I will grant metal might have greater heat transfer capability, but the delts T and flow rates (which affect turbulance) have a more significant impact.
If you get a copy of USA Coil's coil sizing program and play around with the configuration options, you can see the minimal impact tube thickness has on heat transfer rate, compared to flow rates and delta T. The reason copper and brass predominates for tube material selection is corrosion resistance and fabrication costs, not necessarily thermal efficiency.
__________________
Eventually, one needs to realize that it is far less important to be the smartest person in the room than it is to sit next to that person and make friends.
__________________
Eventually, one needs to realize that it is far less important to be the smartest person in the room than it is to sit next to that person and make friends.
Heat Transfer Reduction
Re: heat transfer reduction
