George's answer is a bit more complete than mine. For cases where the heat released or absorbed is non-linear, other correction factors apply, and need to be considered. Typically, these types of cases need to be analyzed in different zones to account for the other effects. That is, for...
Since very few heat exchangers are actually in pure counterflow, there is usually some kind of correction factor (less than 1.0) that needs to be applied to the raw LMTD, which is just calculated from the two terminal temperature differences. That is likely what they are referring to on the data...
GeminiII,
I'll take a stab at this one. If you use a typical 1" OD tube with 5/8" high aluminum fins at 10 fins/inch, the surface area is about 5.65 square feet per linear foot. A typical U value would be on the order of 5 to 6 BTU/(hr-sq ft-deg F). Therefore, a good estimating value would...
kjocis,
I wish I knew. I've never seen a project of this type actually go forward. Here are a few ideas to get you going. Let's assume an overall U value of 6 btu/(hr-deg F-Ft^2). This is approximately 34 W/(m^2 deg K) Calculate the heat you are trying to recapture. Calculate a log mean...
kjocis,
These types of heat recovery units have a few problems. First, the operating pressures are near atmospheric on both sides, allowing for very small pressure drops on both sides of an exchanger. Low pressure drops, generally translate to low heat transfer coefficients. The second...
q3s,
If the coolers are operating, a simple way to check for accidental warm air recirculation is to measure the inlet temp to the fans at various places. I'm presuming that these are forced draft (fans on the bottom) coolers.
In this scenario, the worst setup is to have a small space (say...
dtorresa,
Here's one way to do it. Determine the thermal resistance of the 18 ga Admiralty tube, based on its thickness and thermal conductivity. Take that resistance out of the overall heat transfer resistance (1/overall coefficient) from HEI. Then calculate the resistance of the 254 SMO...
Jamesbanda,
Since there have been no replies yet to your query, I thought I would chime in. I'm not an end user, but have been involved in cooler designs for quite some time. As you can tell, these systems are very rare. I think that's for good reason. The problem with any kind of mist...
SJones,
Your right. The original question referred to fans, not fins. However, since he alse referred to fouling, it appears that his intent was to ask about coatings on heat transfer surface. Maybe he will respond to clear things up.
Speco
EnergyMix,
I checked with my manufacturer on your question. We're researching it a bit to try to find a better answer. In the meantime, he's estimating it at approximately 5% (and possibly higher) additional thermal resistance based on a 2 mil coating thickness. Using coated finned tubes is...
jamesbanda,
I'm not an end user, but a designer and rep for an air-cooled exchanger manufacturer. So you can take what I say with a large block of salt. That said, the usual to the problem of fin-side corrosion is extruded, not coated fins. I have seen Heresite coatings used for some bizarre...
Khardy,
Tank heaters of this type often used finned tubes or finned pipe. If you have that option, you could do the same job with muchy fewer linear feet of pipe.
Regards,
Speco
landrover77,
I would suggest calling Cooling Products in Broken Arrow, OK. They have extensive experience with full recirculation systems for the North Slope and other cold-weather applications. Full disclosure: We represent them.
Regards,
Speco
