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Viewing blog entries in category: Tank atomizers - pressure differential design

  • State O' Flux
    RBA, RDA, RTA... oh my! For those folks that are new (and semi-new) to RBAs, what are they and how do they work?

    I could delve into the history of the RBA, but I imagine that most of my "gentle readers" don't really care about history - rather a bit of definition for what is available now. I'll also toss in a few bits of editorial commentary for the reader to ponder.

    I apologize if I don't mention "your" atomizer. In the scope of this short article, I can't cover every atomizer design made, so I'm focusing on what the blue collar "Joe Vapist" is buying now.
    If this annoys you, write your own elitist POS article. :2cool:

    First, lets define what an RBA is. An RBA is any atomizer, designed so that the wick and coil elements are, to a large degree... at your discretion.
    Beginning around the fall of 2014, you can buy RTAs with your choice of ready to go coil/heads, or the option of a DIY RBA head. You can start off with know RBA experience and just use the supplied coil/head assemblies... and at your discretion, learn how to produce your own builds.The Kanger Subtank and Subtank mini are good examples of this relatively new genre of "user optional" atomizers.

    Beats the hell out of trying to rebuild a clearo/glasso that was never intended to be rebuilt... don't it?

    Some will require, due to their design, a specific shape or even specific coil and/or wicking material, but for the most part... it's builders choice, hence the name "rebuildable atomizer".

    They can be a rebuildable dripping atomizer, like the ubiquitous and still hugely popular JPGE Nimbus... or a genesis type atomizer - the Smoktech RSST being a popular entry level example, or a tank type atomizer or "RTA" - as represented by perhaps the most popular RTA ever made - the SvoeMesto Kayfun.
    In the last few paragraphs, I'll include a few RBAs that fall into a, mostly undefined category - the "top-filler-to-wick" atomizer.

    The RDA.
    In basic design, a dripping atomizer or RDA, is the simplest form of atomizer. They do not have a built-in, semi-sealed or sealed juice container or tank. You build your coil(s) and wick(s), drip juice from your bottle onto the wick... and vape away. When the draws start to taste a bit dry and less flavorful, it's time to drip in more juice.

    The upside of RDAs are that they allow practically any coil - shape, quantity and resistance values are limited only by the number of terminal posts and the size of the build deck. The wicking materials used are unlimited as well - from "roll-yer'-own" cotton ball to ceramic rod or rope... it's your call.
    The downside to RDAs is that they don't have a juice container - with even the deepest juice wells holding no more than 30 or so drops of juice. RDAs can leak, and will require that you have a separate juice bottle at your disposal.

    "Drivin' and drippin' can be a dangerous habit to develop - particularly with a manual trans, or motorcycle. :ohmy:

    Still hugely popular, but... as drippers become larger, more refined and complicated, what will they turn into - something else entirely?

    The Genesis RBA
    A genesis atomizer is a device made from necessity - and a "Eureka moment". We look at the dripping atomizers greatest negative, a lack of juice container - and think, "how do I get around carrying a juice bottle and dripping?" - with the answer being... "lets just attach a juice tank to the bottom of an RDA, and run the wick down into it!!!!" And that's how the "genesis" was born.

    OK... maybe it wasn't quite that simple. :p

    Genesis atomizers have some limitations and requirements. Because the liquid tank is not sealed, if you tip it over or upside-down, juice may leak... or even pour out the wick hole or tank vent port.
    Because they essentially feed from the bottom up, you may need to "tip" the atomizer to get juice up to the portion of wick that is wrapped by the coil. Wick materials and design become more important in that capillary action is a critical consideration.

    Stainless steel mesh and rope, as well as ceramic rods are popular wick materials, as they can provide a balance of adequate, but not excessive, capillary action.
    There are new and interesting variations of genesis atomizers introduced every day. Some that are guaranteed not to leak and some with tanks on top.

    "Genny's" have lost a lot of love in the past year or so... mostly due to the next RBA on our list.

    The RTA - "tank" atomizer
    All of the popular tank type atomizers can be defined using another term... they all operate on the principal of "pressure differential". The hyperlink is to an article on how pressure differential or "PD" tanks work.
    For those that don't want to read the entire PD article, in short and sweet terms... positive pressure (in the air venting system) and negative pressure (in the liquid tank) are held separate - yet balance... serving to feed juice, in appropriate quantities, to the wick. The wick itself may aid in this function, acting as a seal between the two pressures.

    Added 7-1-14: (Sorry... I'm about 2 months behind in adding this)
    If you've not heard of it, don't feel too bad... because the Highwinds Ruzgar, and it's recently introduced clone (first one... anticipate better quality ones) have been a bit under the radar. Think of it as a top fill, glass tanked evolution of the KFL. It doesn't have AFC, but the genuine one I tried had air flow on par with a stock Kebo R91%.

    The previously mentioned Kayfun is one of the 'true' pressure differential atomizers, in that the design does not use the wick as a seal, but rather only the "boundary layer", established by juice channel orifice size, to keep the pressure, and juice, separate.
    Other popular PD tank atomizers, like the Stattqualm sQuape and Taifun GT use orifice size restriction as well, but in concert with the wick, which, not unlike a glassomizer coil/head assembly, serves to define that restriction.

    "Filler" type RBAs.
    OK... I'll be honest here, I'm not sure what to call them. Gravity tanks, top-filler-to-wick tanks, capillary tanks - are any accurate enough to stick?

    This category is populated with atomizers like the VapourArt GP Spheroid, early version GP Heron and Gus Aiolos... which can be considered closer to genesis atomizers than RTAs, because they do not use pressure differential or a true liquid tank, but rather a filler material, usually "cerawool", to both hold juice, and feed the wick.

    Interestingly enough, the latest version GP Heron, with the addition of a spacer/separator, or as VapourArt calls it - "a topper that works as a reducer and cotton feeder at the same time" - this after-the-fact part, aside from the stated design intent, creates the potential for a seal between liquid storage and vaporization chamber.
    This seal, depending on the build, may be sufficient to create and hold a negative pressure, effectively turning the atomizer into a semi-PD type tank... but one where the pressure variance is not used to feed juice. There is a Heron clone available now from FT.

    5-5-2014 Addendum.
    There's a relatively new atty on the market made by GUS in Greece, called the Estia.
    It is a PD atty, and is designed around 3 coils with 6 wick tips "in the juice"... with the highest air flow of any RTA to date. It's currently the very best RTA I've ever used... and as close to a good RDA as one can buy.
    Not much else I need to say, because qorax has done a very well photographed, slightly gushy and subjective, but never the less informative review here.
    If you get a chance, take a look at the Inverno Erlkönigin review too. I don't know qorax, but I know he does two things very well... buys the latest cool attys, and produces some very well photographed reviews.

    The Fogger V4 came out a month or so ago. This is a dual coil atty... and I mention it in the same breath as the Estia, because it's, well... quite a flavorful vape for such a low cost atty.
    It doesn't have the air flow, features or quality of fit and finish of a genuine RTA, but it's 1/5th the price... and easily one of the best performing clones you can get. Only the single coil, genuine Taifun GT is on par.
    Due to it's low price, there are many threads in the RBA forums on this atty... so find one, and read.

    I return and update as things change... stay tuned.

    As always, take it for what it is, do with it what you will. Cheers!
    FilthyPazuzu likes this.
  • State O' Flux
    "Tank" type atomizers... For new vapists - how they work, and why it's a good idea to know this.

    Thought I'd throw something up to help relatively new (and some not so new) vapists understand how "tank" type, or RTA atomizers work.
    Bear in mind, in this instance, the word tank can be used to describe most any clearo, glasso or carto tank... as well as RTAs.

    The common denominator is that all of the above tank devices are functionally dependent on what's called, a "pressure differential". A techno term meaning that both high, or positive (in this context, atmospheric) and low or negative (vacuum or, in this context, less than atmospheric) air pressure are in play.

    There is high pressure in the air tube (or "chimney") that rises to the drip tip and down to the coil... and out the bottom to the 510/eGo connection, or adjustable air control orifice. In the tank with the juice - under normal operating conditions... we find low pressure, or vacuum.
    Still with me? Good. [​IMG]

    I can't go further without talking briefly about wicks. Wicks have a few jobs - one of course, to wick juice to the coil so it can be vaporized, and two, the lesser known... is to function as a pressure seal. Not a perfect seal mind you... but one with a slow leak, that works both ways.
    Not all PD atomizers use a wick in the latter description, but instead may use a series of orifices, where the dimension controls the transfer of both pressure, and with that, juice. The Kayfun design is the best example of this design.

    More with wicks in a bit... promise.

    So, how does negative pressure get in the tank when all around us is atmospheric or negative pressure? Well, that would be dependent on you... drawing on the drip tip. The temporary vacuum you create pulls juice, and that positive pressure you started with in the tank, into the coil head area... and a modest vacuum in the tank is produced.
    Draw again... vacuum is enforced and perhaps even enhanced. Not a tremendous amount of vacuum... because most of our "lung generated vacuum" is directed out the venting system - and remember, our wick/pressure seal - still has that slow leak.
    All else being equal, as our fluid column lowers, the negative pressure you've established above that fluid level will continue to be enforced and enhanced as well.

    If we close (or even restrict) the atmospheric venting system and take a draw, what happens? That's right... most to ALL our vacuum is directed to the liquid tank... and depending on our seal (or control orifice) design, we may end up drawing juice right past that and into our coil/atomizing chamber.
    This may be advantageous... in that with some atomizers, increasing the vacuum - immediately after filling or refilling and closing the system up - is key to both preventing leakage and to a lesser degree, priming the wick.

    Does the vacuum last forever? With a wick seal - unlikely. If you walk away from a wick seal type atty that you were using... the vacuum may be slowly supplanted by positive pressure. How much or how long is a variable of the atty and the wick/seal.
    This may be why your atty can be a bit gurgly (or you may find the 510/eGo positive "well" a bit wet) when you pick it up again... until you reestablish a vacuum with a few draws.

    Once again - The pressure differential, in concert with wick seals and/or control orifices is why tanks don't leak like sieves - and why, when you refill a tank and introduce positive pressure back into it, they may gurgle a bit until a vacuum is reestablished.

    And now... more on that all important wick/seal. If you're using a clearo/glasso of the Kanger BCC variety, it's (very) common to play with wicks. Removing flavor wicks, changing wick thickness and materials - and generally tweaking the pressure differential "seal"... without much thought to the fact that it functions as a seal .
    Take out too much and the atty gurgles and even leaks. Add too much, or to "tight" a compression - and you get dry hits - and if a cotton wick, burnt gym sock flavored hits.
    When you start to fine tune wick systems, with ball cotton perhaps being the most currently popular DIY wick material... take a moment to consider - "Is this (dimensionally) enough, or too much wick for the channels it fits into?" Is this wick too heavily or too lightly wrapped - is the density such that, capillary action is sufficient to feed the coil, but not drown it?"

    I mentioned earlier that some advanced RTAs (may) use the same physics as a $5 clearo. The Squape, Taifun GT, Ithaka, Fogger V's, Aqua and even the latest greatest GUS Estia, along with their clones and variations, all fall into this category to one degree or another... with their wicks exposed to the juice tank. This isn't a bad thing, if done correctly, it works well and consistently.

    A Kayfun, as well as it's variations and clones, use the pressure differential concept, but without the wick functioning as a seal. Instead we use the method of "controlled orifice" juice passageways - and a neat balancing act known as a "boundary layer" - which is established by those specific orifice sizes, keeping the juice from flooding the atomizer chamber.
    In this application, juice is fed in liquid form, all the way into the atomizing chamber, before it encounters the wick.

    With some lower priced KF clones, where the design is copied but not understood, and the orifice passageways are not considered "important"... you may find a condition of perpetual flooding or dry hits, from those orifices being too large or small.
    The wick can act as a sponge... where with lower priced clones, they may have overdone it a bit on the orifice dimensions - and so those atomizers may need more wick than the original to stay in balance.

    I suspect that the designers of the Kayfun (and Russian) spent more time fine tuning this aspect than any other.

    Even genesis tanks have a pressure differential, but due to the design of the (typically metal or ceramic) wick not really functioning as a transfer port seal... it's frequently very temporary, unless the re-builder is very clever, in both their wick design and how that wick fits into the port it passes through.

    Before this gets so long that no one wants to read it... I'll stop. :p

    I used to teach this stuff - but in a different application. However, the same, sometimes complicated and really quite impressive "Bernoulli Principle" fluid dynamics apply, so... there you go, differential pressure is alive and well in your atomizer.

    That's it... take it for what it is, do with it what you will. ;)
    Anisette, Enso, TrashCat and 5 others like this.
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