phex, you are very taft today. There are many people who like upper case. What's the matter?
Further, whowhat is right, I suppose he is looking for twisted tapes, or twisted ribbons.
Brown Fintube (I think belonging to Koch, at present) makes twisted tubes.
whowhat, Cal Gavin makes twisted tapes to be inserted in existing heat exchangers, to improve the performance, for laminar flows, etc. They call them "turbulators" and its trade name is "Hitran". It's a British company, follow:
There are a number of inside turbulance enhancers. Turbulator is a registered trademark. One of the other styles looks like a bunch of wire loops. The folded or twisted strip styles are made by a number of people. I believe that HPD still is in the business.
If you are retrofitting make sure that your tubes can tollerate the flow. Also remember you will increase your tubeside pressure drop.
All of these require that you have a clean fluid or they will foul. You also need to think about what will happen when one comes loose, will it damage a valve or pump?
For new construction where size and efficency are critical the BrownFintube Twisted Tube design is fantastic. I have worked with a number of them.
= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.
Oh, my bad, I'm sorry. didn't hear the expression "twisted tapes" before, which is probably due to me not being a native english speaker.
Furthermore, my temper has been a little hot yesterday, so I - once more - have to apologise. But writing in all-caps is something I really don't like. This is probably because I'm quite an internet nerd and as such give much about the netiquette. In online communities, writing in all caps is normally considered to symbolize shouting and it is considered rude to do so. I probably shouldn't feel this way in these fora, cause this is engineering and as such not a community of "nerds", so I presume this is not valid here. But, as I said, I had a "short fuse" yesterday and coudn't restrain myself. I know this is not an excuse for behaviour like this, but at least an explanation.
What you are referring to are what used to be called "turbulators" - at least that's what they used to be called at DuPont. I believe the HTRI also refers to them by that name. I hope you know their purpose and use with regards to heat exchangers. Most young engineers and recent grads have abused them because of ignorance as to what they are intended for. Young engineers seem to think that they are the greatest thing since Teflon and the answer to every heat transfer problem. The answer is: they're not; but they serve a specific purpose under certain conditions:
1. They are intended, primarily, to stimulate turbulence and convective currents which tend to increase the tubeside film coefficient. They do this at the expense of pressure drop and, as a result, are not very efficient.
2. DuPont (& other major companies) used them (& I think they still do) because in the practical sense the company owns multi-million $ worth of heat exchangers that have to be versatile and used in a variety of services during their lifetime. In order to be able to have a "fit" with an application, these turbulators come in handy in being able to modify the tubeside characteristics so that they can be applied in a variety of cases.
3. Sometimes, albeit rarely, the tubeside fluid characteristics (like viscosity) can play havoc with the film coefficient and a designer has to have some tool to adjust the ultimate heat transfer. Turbulators can serve this purpose.
4. There may be other reasons to use them - like stimulating turbulance to reduce film fouling and reduce the fouling coefficient.
They should not be treated like a panacea. They have a specific use under certain specific conditions. I don't know any specific companies that design and sell the turbulators, but I'm sure you can find out by asking heat exchanger manufacturers themselves - they are the prime users of the items.
Don't you think my text and commentaries read a lot better and are conducive to good understanding when typed in the conventional, small case with appropriate capital letters? I personally agree with phex; why torture the English language? It goes through enough grief as it is without having to be expressed in total capital letters. We need to communicate more and better instead of just trying to make impressions.
two other facts to note:
a) if you want to minimize the increase in pressure drop, you have to have a 1/4" clearance ( "relief") between the ribbons and the tube ID ( by use of spaced buttons)
b) the more modern method is to use rifled tubes ,not ribbons, if it is a gas -liquid mixture.
I share Phex's and Art's dislike of ALL CAPS. Could this be an age thing ;-) I worked in a company where the policy was to use ALL CAPS for job descriptions, and I really struggled with them.
It is interesting to note that road signs are never written in CAPS. This is because we learn to recognize the shape of a word as much as (or more than) reading the actual letters. You can recognize "Chicago" from much further than you can read "CHICAGO".
Recently there was an email doing the rounds that showed how (English) readers can make sense of words that are totally wrongly spelled as long as the first and last letters are correct, the length is approximately correct, and the shape of the word is familiar.
Sorry for coming onto this thread late ... I too am looking for a source of twisted tapes to insert into a tube type heat exchanger ... my application is for some research at NASA GRC in Cleveland. I'm not familiar with "HPD" and a google search did not seem to return much.
. Pete