Heat Transfer Rate of Steam Bubbling in a Liquid

Thanks. That info is exactly what I needed. I just hope I can figure it out now. The first link is especially good, and it looks like I pretty much nailed identifying the issues that need to be considered. You've been very helpful. I mostly lurk on this group when I have the time, and I'm always impressed by the amount of help that people provide.

Cheers.

Bill Velek

The mystery saviour strikes again!!!!

..................see this thread for an explanation:

http://cr4.globalspec.com/thread/25721/Round-Pipes-vs-Square-Tubes

Hmmmm. I really do appreciate your taking the time to reply, but is that the correct link? I've read every message in that entire thread (as far as I know) ... TWICE ... and I can't see anything in the thread that helps answer my questions. What am I missing? Can you take a quick look at the thread and then tell me what the message number is?

Thanks.

Bill Velek

Oh, there is no answer to your question in that thread.

I was just pumping sunshine up my own arse by saying that I received some more 'Good Answers' - but I like to post as an anonymous Guest and not keep track.

You have a rather unique problem but interesting I must say.

My suggestion would be that you should look to books that teach about Boiling Heat Transfer. Some of the usually addressed considerations in this area - and it is many years ago that I studied this - are the effect of the size of bubbles on their point of collapse as they travel upwards, the effect of the bubble-temperature and liquid-bubble temperatures differentials on the initial bubble size at injection and of course the impact on point of collapse, the rate of heat transfer as a function of bubble motion dynamics - rotation and all, and of course the impact of coalescence and knifing of bubbles.

You do have an interesting problem my friend.

Bill,

A couple of questions....

What is the final solution temperature target?

What is the solution sugar concentration target?

Is this a batch process?

Is the kettle open or closed to the surroundings?

I am assuming you are using saturated steam and not superheated at a low feed rate (i.e. low velocity)...

Some thoughts....

Because the solution you are bubbling steam through is cold initially, the steam injected will more than likely condense instantaneously. This will occur as the local area about the injection point is heated and heat is transferred through solution to colder areas. If this is a batch process you may need an agitator to restrict temperature and concentration gradients.

Any solute (sugar for this case) added to solvent (water) will raise the boiling point of the solution. This is a collagative property called boiling point elevation. And the raise in boiling point is proportional to the concentration of the solute.

So any steam you bubble through will more than likely be captured in solution because the solution will always be at a higher boiling point then the steam used. However as the system becomes diluted, the boiling point will decrease and approach that of pure water (212 °F under atmospheric conditions). You may see steam bubble through and exit solution then.

To tell you the truth, I have been a little perplexed at Bill.

I had thought that he had found the answers to his questions in the first link given to him in the initial reponse of Guest, only to find that he was still seeking answers. I therefore surmised that perhaps Bill was not looking to understand the problem as to actually acquire the knowledge underpinning the problem, but rather he was looking for a formula for a quick answer, so I went silent.

Perhaps after much searching he would settle on understanding the problem, and then he would develop a real and comprehensive solution to the problem by considering your suggestions.

ChemE119, before answering your specific questions, let me first briefly explain the system we hope to build and what we hope to accomplish with it, and perhaps that will also address concerns expressed by 'editorgbanalysts' in post #8 as well as provide you with a better understanding of the problem.

Our business is a 'brewpub'; as such, under Arkansas law we will be authorized to produce up to 500 barrels of beer per year, or essentially a maximum of 10 barrels per week. One typical approach is to purchase expensive commerical brewing equipment for batches of perhaps 5 to 10 barrels at a time, but in order to carry a variety of craft beer such as the five that we plan to carry as standard stock, plus some specials that will change from week to week, large equipment of that size is not feasible due to the size of the equipment (generally too tall for the leased premises), the floor space that several varieties would occupy, and the capital investment it would take. At maximum capacity, we could brew 1.5 barrel batches (9 '5-gallon kegs' each batch), probably 2 batches per day 3 days per week = approximately 9 barrels per week.

In case you are unfamilar with the brewing process, it involves these vessels: a mash tun (also serving as a lauter tun in our design), kettle, fermenter, bright tank (for conditioning and forced carbonation), and kegs. A small brewery can manage with just a single mash tun and a single kettle, but each variety of beer must sit in its own fermenter for a week, and then in its own bright tank for a week, and each must be completely emptied for the next batch. Our plan is to use 55 gallon stainless steel drums for all vessels; to carry a total of six varieties of beer at a time, we need six 'pairs' of drums with the fermenting drum stacked above the brightening drum. All very feasible and practical. When emptied, they will be removed and steam cleaned and sanitized. We will have at least 60 of our own 5-gallon kegs.

Now, the reasons why we want to use steam:

1.) Natural gas is unavailable, and propane is expensive and we have no place to locate a large outdoor propane tank, and we don't want to mess around with constant trips to refill smaller propane tanks;

2.) Since we will be using electric heating, the most efficient method is to locate the heating elements inside the liquid, but high heat density can easily scorch beer and cause carmelization;

3.) Because of small batch brewing is more labor and time intensive, we want to shorten the brewing process as much as possible in order to manage two batches per brewing day during an 8 hour shift; using steam _should_ enables us to do that, as explained below, provided that we can use it efficiently -- thus my questions about it;

4.) Steam, as mentioned above, will help us clean and sanitize -- two very important parts of brewing.

To fully understand the problem, this is the brewing process that we will use (in a nutshell):

1.) Hot water is added to milled malt and any other grains in the mash tun; complicated mashing schedules can include temperature steps but most of my beer is done with a single saccharification rest at 152F. A typical grain bill for a 1.5 barrel batch is from 70 to 90 pounds of grain, but could be as high as 150# for something special like a barley wine. Let's use 85 pounds as a standard, which will produce an average beer of about 4.9% alcohol by volume at 80% extraction (which we hope will be our minimum). At a common ratio of 1.25 quarts of water / pound of grain to start and a target temperature of 152F, we will need to add 26.56 gallons of at least 165F water (will no doubt need to be higher once we determine thermal mass of the tun). The mash then sits there for anywhere from 45 minutes to an hour to convert starches to sugars; a recirculating pump through a heat exchanger is used to maintain the temperature. The total volume of grain and water inside the mash tun at that point is 34.73 gallons (inside an insulated 55 gallon drum). During the time that the grain is mashing, our boiler will be heating water needed for sparging (flushing sugars from the grains), and we also intend for it to be building up a reserve of heat for a very rapid jump to boiling when the wort finally reaches the kettle.

2.) Sparging is done with water no hotter than 170F to avoid the extraction of tannins from the grains which would cause astringency; I use 168F for a margin of safety. By recirculating the original mash liquid through a heat exchanger, we should be able to drain 16.9 gallons at 152F before sparge water is added. Then 26.9 gallons of sparge water at 168F is filtered through the grain bed and into the kettle. Ignoring heat losses in the system for simplicity at this point, and allowing for 4.1 gallons worth of condensation from steam (assuming 100% heat exchange and no losses from steam bubbles reaching the surface), we should end with approximately 48 gallons of wort at 212F, which yields 46.5 gallons (1.5 barrels) after allowing 1.5 gallons for absorption by the hops. I know that I haven't allowed for expansion of the liquid either, but this is already way too long. Sorry!

3.) The depth of a full batch inside of the kettle is a bit less than 20", and even with a specific gravity of 1.110 (such as for a barleywine and about the highest we would _ever_ go), head pressure is less than 1psi, which I don't think changes temps enough to be concerned. Since Coors brews in Golden, Colorado, where I believe boiling temp is below 200F, whereas ours is 211.8F, I'll be satisfied if we can get a rapid rise to 200F, although we will not doubt eventually reach 212F. I say this because if proteins coagulate and alpha acids isomerize in Colorado then we will be accomplishing some of the primary purposes of the boil, even at just 200F. Another purpose is the stretching effect that expanding steam bubbles have on some of the molecules in the wort, but we will have that by steam injection whether the wort ever reaches 212F.

I apologize for being so long, but that about sums it up: 212F steam bubbling in liquid which starts at about 18" deep and 162F, with a target temp of 200F as quickly as possible, and at least a 60 minute boil after that with temps eventually reaching close to 212F (90-minute boils are pretty much the norm, but much of that is probably simply to evaporate excess runnings).

Now, here are the answers to your specific questions:

What is the final solution temperature target? A minimum of 200F.

What is the solution sugar concentration target? Normally a gravity of about 1.050 to 1.060, but sometimes as high as 1.110.

Is this a batch process? Sorry, but I don't know what you mean by that; if you mean, is this a fixed quantity rather than a continous flow, yes.

Is the kettle open or closed to the surroundings? It will be insulated on the outside, but the top will normally be open to avoid boil-overs; I suppose that we could add a lid at the VERY early stages of heating, but I'd prefer to not take chances.

I am assuming you are using saturated steam and not superheated at a low feed rate (i.e. low velocity)... Well, let me explain that a bit. I think it would be inefficient to begin bubbling steam in the kettle when the depth in the kettle is still relatively shallow even though the wort will be at its coldest (about 162F), so I would imagine that we would just circulate the wort from the kettle to a heat exchanger and back to the kettle until we get some depth. For that quantity of wort, draining and sparging could take half an hour. During that time, the boiler will build up some pressure and temperature (including the temp of the water inside which, if we are planning to do a second batch that day, be about 50 gallons) ... up to 15 psi MAXIMUM ... so that's what we would start with, but pressure and temp will gradually drop down to the normal operating pressure equal to the head pressure about .8 pounds.

Thanks in advance for any further comments and assistance.

Bill Velek

Bill!

Simply put, my understanding of your project in this section is as follows

Given a Kettel charged with wort which starts at about 18" deep and 162F and of liquid volume 42.4 gallons and [wet-]hops of 1.5 gallons, and with a specific gravity of 1.110 (such as for a barleywine and about the highest we would _ever_ go), and head pressure estimated as less than 1psi. 212F steam bubbling in liquid , with a target temp of 200F as quickly as possible, and at least a 60 minute boil after that with temps eventually reaching close to 212F (90-minute boils are pretty much the norm, but much of that is probably simply to evaporate excess runnings), steam should fully condense inside the wort during the bubbling, and allowing for 4.1 gallons worth of condensation from steam (assuming 100% heat exchange and no losses from steam bubbles reaching the surface), such as which yields 46.5 gallons (1.5 barrels) [allowing for the 1.5 gallons of liquid absorption by the hops].

Now as I see it, here then are the issues:

• The concentration of sugar in the wort is not known but that can be back-calculated from an analysis of the fermentation reaction; however, concentration of sugar is needed to determination the extent of boiling point elevation so that the quantity of steam injection required to cause boiling is determined,
• The number of steam injection ports is needed to determine how fast steam is being injected into the wort, but base analysis can be performed for a single port and then roughly multiplied by the actual number of injection ports,
• A single steam bubble traveling up the wort causes mixing as it carries along its boundary, a wake that is pushed into the rest of the wort when the bubble collapses; so the problem may require a single body problem analysis, see our site:
• Besides because the bubble may increase in size as a result of the falling pressure head as it rises up reaching a maximum size and then begin to reduce in size due to the heat losses, all of which cause interesting heat transfer and mixing phenomena, a single body problem analysis more effectively captures all these.

As I had said you have an interesting problem.

Off-Cuff suggestion:
However, off the cuff I will suggest that you begin with some kind of superheated steam that will not immediately collapse upon injection into the wort, but bring down the steam state in relation to the temperature increases of the wort: By this process, the heating process will always have a steam bubble traveling through the wort, thus heating the wort and also mixing the wort at the same time.

Just my thoughts and off the cuff.

Thanks again. I will study the reference material you provided as soon as I can. However, with considerable embarrassment, I must confess that I made another very stupid mistake in my last post, which I will attribute to sleep deprivation (it was posted at 5:03 a.m.). When I checked the dimensions of a 55-gallon drum on a website, I transposed numbers (diameter and height) and then compounded the problem by making my depth calculations based on it (starting depth: 44/55*22.5=18" and ending depth: 48/55*22.5"=19.64"). I am really sorry to have made such a blunder which really should have been immediately obvious to me, and for wasting your time and effort in that respect. The CORRECT beginning depth is 44/55*34= 27.2" and CORRECT ending depth is 48/55*34= 29.7" for an average depth of 28.5" and an average head pressure of 1.14 pounds at our highest specific gravity of 1.110, but once again I don't think that this pressure appreciably affects the problem.

Until I have a chance to study the reference material, let me also suggest a possible solution that occurred to me when I woke up this morning. We could install a pre-kettle heating column consisting of a vessel that has a 12" inside diameter and is 8' tall; that would have a volume of 10857.34 cubic inches = 47 gallons. It could be capped on the top with a pipe leading down to the bottom of the kettle next to it to transfer any overflow to the kettle. Since we start the heating with just 43.8 gallons at 162F, it will initially fit; to raise the liquid to 200F, including condensation, requires 3 gallons of 212F steam, for a total ending volume of 46.8 gallons which still _barely_ fits (although not counting expansion), but also remember that we could have an overflow directly into the kettle when the volume maxes out as we approach the target temp. The 200F wort would then be transferred to the kettle for a 90 minute 'boil' with steam, during which 1.1 gallons should condense to bring the total volume close to the projected 48 gallons. Such a pre-heating column would have a head pressure of 3.37 psi with 1.110 gravity wort, which I think, again, probably won't create problems.

The tall column would give the bubbles about 3 times the distance to condense and would also help solve the problem of how to disperse the steam more or less evenly over the cross-section because it will be substantially smaller; in addition, with a narrower vessel, we should reach a sufficient depth after only partially finishing the sparge to permit us to begin steam injection sooner. I know that the column would create a much larger surface area for heat loss from the vessel, but we could reduce that a lot with insulation. It will also waste some heat due to its thermal mass, but that could be minimize by using a very thin gauge of metal if we can find something suitable.

Now, I don't know what other factors come into play using such a narrow column; I don't want to cause an effect like a coffee percolator with liquid trying to spout out the top; is there a name for that 'effect' so that I can investigate whether that could be a problem?

Thanks for any feedback, and I apologize again for my stupid error in depth and for changing the factors with this new idea.

Bill Velek

My regrets in responding now!

Your proposal would still cause you the problem that ChemE119 advised - the condensation of the steam bubble upon injection into the column. You still have to determine the extent of boiling point elevation in order to determine the state/quality of steam you need to inject into the column.

Alternatively, as per ChemE119, simply stir the wort while injecting the steam which will not form bubbles but will still provide the thermal energy you want. Is there a reason you do not wish to stir the wort? Perhaps, there is and I do not know.

BTW, how do you propose to boil the wort with steam in the Kettle? Is it your plan to steam jacket the kettle? Or is it to boil the wort for the 90 mins with the 1.1 gallons of steam you expect to condense in the wort? If the latter, then you still face the issue of elevated boiling point that ChemE119 has raised, in which case we are back to stirring.

I hope that this is helpful

EditorGBAnalysts wrote:

> Your proposal would still cause you the problem that ChemE119 advised
> - the condensation of the steam bubble upon injection into the
> column. You still have to determine the extent of boiling point
> elevation in order to determine the state/quality of steam you need
> to inject into the column.

Thanks, and a big 'thank you' to ChemE119, too. I'm learning a LOT and making great progress here. I now realize that, whether I use a pre-kettle heater or not, there will still be two stages to the process, requiring two different types of steam -- the pre-heating stage when I _want_ all of the bubbles to condense and consequently increase the volume of wort, and the boiling stage when I want bubbles to reach the surface without any condensation.

During the first stage, assuming that latent heat is independent of state/quality of steam, and because I want full condensation, I suppose that I need only the poorest quality of steam and pressure sufficient to inject the necessary volume of steam for that head pressure -- whatever is necessary to achieve a good dispersal of bubbles and raise wort temp to 200F as rapidly as possible by having as much of the steam as possible condense and thereby release its latent heat into the wort. I don't care if the release occurs very close to the point where it is injected, or if it needs to rise 90% of the way to the surface; either way, the surrounding wort is heated, and the bubbles should cause enough movement of the wort to avoid stratification. I don't really see this process as much different than heating the bottom of the kettle externally: the bottom gets hot enough to vaporize water, bubbles form and eventually break free from the bottom, and as soon as they do they begin to condense within the cooler wort that they are rising through; the process continues with bubbles being able to rise closer and closer to the surface as the wort gets hotter and makes it harder for the bubbles to release their latent heat. Eventually bubbles begin to break the surface more and more, increasing the vigor of the boil. So, if I can inject steam at or against the bottom of the kettle in a manner which causes a similar number, size, and relatively uniform distribution of bubbles that an exterior heating of the kettle causes, then the effect should be the same. The advantage that I am looking for is the ability to inject steam at a rate which greatly surpasses what can be generated on the kettle bottom by direct heating, the latter being limited by necessity to avoid scorching and carmelization, and probably by the practical limits of conductivity on the kettle bottom.

> Alternatively, as per ChemE119, simply stir the wort while injecting
> the steam which will not form bubbles but will still provide the
> thermal energy you want. Is there a reason you do not wish to stir
> the wort? Perhaps, there is and I do not know.

I _could_ stir the wort, if necessary, and I have considered whether a stationary or a spinning disk made of screen would help to more evenly disperse the bubbles. There is no doubt that if the bubbles are small enough and spread out across the cross-section of the vessel to minimize coalescence, that this method will work. But I don't know how fast the steam can be injected to balance speed of heating with efficiency. In other words, consider this: assume that a 100-BTU burner will boil my wort without carmelization, but a 200-BTU burner is too hot; if instead of applying the 200-BTUs directly to the bottom of the kettle and scorching, suppose I use it to make steam which is injected at the bottom of the kettle, and I therefore have no risk of carmelization but I can still heat my wort twice as fast as with the 100-BTU burner ... _IF_ much of the steam is not being wasted by forming large bubbles which reach the surface and waste steam.

> BTW, how do you propose to boil the wort with steam in the Kettle?

Just by bubbling steam through it. For my purposes, it really doesn't make any difference that the wort itself is 'technically' not boiling, but instead just has steam bubbles rising through it. The wort doesn't know if the steam bubbles were formed on the bottom of the pot by an external heat source or if they were injected; the steam bubbles are just that -- steam -- and then contain no sugars, oils, resins, or anything else. The conditions that I need during the boil are temperature and lots of expanding bubbles. Upon reaching about 200F, I really don't care one way or the other about the temperature rising any further, although I think it is inevitable that it will do so with steam bubbles rising through it for 90 minutes; note my earlier comment about commercial beer successfully brewed in Golden Colorado where boiling temp is below 200F. As for the bubbles, they are needed to help create surface tension of the so called "albumin fraction" of the protein. These particles then will concentrate on the steam bubbles and because of the high concentration, they will aggregate into larger and larger masses. More scientifically, the micellae, denatured in the boiling process, are held in suspension only by their electric charges. When in turn, the force of affinity between the micellae exceeds the force of electrostatic repulsion, as a result of high concentration on the surface of the bubbles, the albumin will aggregate and precipitate. This process cannot be achieved without a rolling boil, i.e., _LOTS_ of tiny bubbles forming a 'hump' of sorts on the surface as they emerge.

> Is it your plan to steam jacket the kettle? ...

No steam jackets; just insulation wrapped around all of the vessels.

> ... Or is it to boil the wort for the 90 mins with the 1.1 gallons of
> steam you expect to condense in the wort?

The 1.1 gallons is only a small portion of the total steam needed during a vigorous 90 minute boil (probably about 6 gallons, explained below); the 1.1 gallons is just the portion expected to eventually condense when the rest of the wort is raised in temp to 212F. At that point, except for small losses through the sides of the kettle, we should have equilibrium with no further condensation and _all_ of the steam reaching the surface. For purposes of brewing, a good boil-off rate is considered to be 10% of your volume per hour which is a high rate for my purposes because it is usually needed to adequately reduce the volume of excess wort caused by enough sparging to raise the percentage of sugar that is extracted (I won't have that problem). I realize that the percentage changes as the volume changes, but you get the idea. The absolute minimum rate is 5%/hour to achieve good breakdown of proteins as described in my long paragraph, above. I generally use 7% or 8%/hour to make excellent beer but it is hard to closely regulate the rate due to imprecise control of gas, and variations due to different gravity beers, humidity, barometric pressure, temperature and wind (I brew outdoors but wind and temp won't be factors in a brewpub). So to end with 48 gallons, I would normally begin with about 54 gallons and boil off 6 gallons over the course of 90 minutes and so I will need to inject that amount of steam over the 90 minutes of 'boiling' to achieve the same degree of bubbling effect.

> If the latter, then you still face the issue of elevated boiling
> point that ChemE119 has raised, in which case we are back to
> stirring.

Then it appears that during the second 'boiling' stage, as soon as we reach the desired volume of 48 gallons, we will need to begin using super-heated steam so that none of it will condense. I assume that this could be done by adding a heating element in the steam line right before it enters the kettle, so long as the element has enough power for the job; I don't think there could be any problems caused by the steam becoming _too_ hot, although that just causes inefficiency. One problem I will face is in determining when and if super-heated steam is flowing at the correct rate of 4 gallons/hour; any higher than that just wastes energy, and significantly lower than that will affect the quality of the boil. But I presume that the flow rate can be calculated based on the applied pressure and size of pipe, and resistance based on the length of pipe and whatever mechanism we use for injection (an injector, or airstone, or pipe with tiny holes, or just spray it under the false bottom). Kettles have a screen or false bottom of some sort to strain out the hops which are added during the boil, and it might be effective to inject the steam between that and the actual bottom of the kettle to try to help disperse the steam. I don't know if there are any gauges that measure the flow of steam, which I'd prefer, but we can rely on calculations and/or use some data by taking water level measurements inside the boiler before and after the boil stage.

Finally, I'm convinced that it is completely feasible to inject 4 gallons/hour of steam into a 55 gallon barrel of wort because that is no more steam than is normally used for a vigorous boil. But an issue that concerns me is how quickly we will be able to inject about 3 gallons of 212F steam into the pre-kettle heating column. Obviously, I want to do it as fast as it can be done without wasting too much steam or causing the wort to shoot out the top. For example, to do it in 15 minutes is three times the rate that would be applied during the boil, and is no doubt faster than I could achieve with direct heat without scorching -- but doing it in 10 minutes would be great, and any less is FANTASTIC!!

Now, in order to create such a large quantity of steam that quickly, we are relying on building up and storing heat energy in our boiler prior to and during our 45 minutes to an hour required to mash our grains, so that, at a minimum, we will have a boiler with approximately 50 gallons of water and a few gallons of steam at 15psi = 248F. Drawing steam, which gradually drops it to a temperature of let's say 222F, should release/flash 50 gallons x 26F / 540F = 2.4 gallons of steam, plus we will have some additional steam created by the boiler during that time. At a minimum, we'll have a 10,000 watt boiler, so allowing about 400 watts for system losses (everything will be insulated) will give us about 9,600 watts which can convert 6 gallons of water to steam in 90 minutes -- exactly what we need during our boil. Since we need another .6 gallons for our pre-kettle heater, the 9,600 watts can generate that in 9 minutes, which is therefore about the limit for how quickly we could reach 200F in the pre-kettle heater -- although I don't really expect to be able to do that well.

As pressure/temperature of the steam declines, it won't matter as much because the wort temperature will be closer to its target of 200F and the lower temp/pressure of the steam will help it more fully condense. In other words, when the wort is only 162F, we are injecting a large volume of 248F steam at 15psi, but when the wort is approaching 200F, we will be injecting a small volume of 222F steam at a pressure which is probably just barely above head pressure, which is 3.37psi with 1.110 gravity wort.

Thanks once again to everyone; you have all been a TREMENDOUS help.

Bill Velek

Shucks! I've been at so many things for too long that I'm not thinking straight. I used Fahrenheit degrees when calculating how much steam would flash from the boiler, etc.; now I've got to relook at everything. I'm absolutely exhausted now, so it will have to wait until tomorrow. Sorry.

Bill Velek

Bill!

Apparently, you have addressed virtually all the issues that need be attended to. As I see it you have three stages of heating of the wort, and you have defined solutions for each of them.

In Stage 1, you are required to perform preheating of the wort from 162F to 200F, and you have proffered to get that done by heating with saturated steam, with the option of stirring if necessary. You have also stated the alternative of using a kettle but I suspect, you will apply heat to the kettle below the limit temperature that cause carmelization. So these essentially take care of this stage of the heating.

In Stage 2, you have proffered to use a Kettle (?) that will be insulated and will bubble steam through the wort but this time with the object of creating the "Albumin Fraction" effect until the temperature reaches 212F. However, I suppose that you would have to keep doing this until the wort also reaches a volume of 54 gallons.

In Stage 3, using the same kettle as in Stage 2, you will change the steam quality to super-heated, and thereby force evaporation of the some of the water in the wort at a rate of, say, 5%/hr and so on, until the wort volume reduces to about 48 gallons. These also very much complete the brewing process of Stage 3.

At this point from the looks of things you are done.

However, you raised some concerns about the specifics of the implementation of the "Albumin Fraction" effect, such as the steam temperature, the steam bubbles size that should be efficacious, the nature of the distribution of the steam-bubbles with the stipulation of coalescence avoidance, etc. This aspect of the analysis, I should think, you would do by trial and error; and the reason being that this aspect is not squarely within the realm of Chemical Engineering but somewhat also partly rather in Chemical Physics. So you will need a Chemical Engineer who also has some understanding of Chemical Physics. The truth of the matter is that a pure Chemical Physicist may not have been involved with problems with boundaries such as the walls of the kettle presents as a chemical enegineer may have been, and will not be effective in solving the heat exchange characteristics through a steam-bubble wall that is redefined by the particulates that you are interested in aggregating with the "Albumin Fraction" effect. On the other hand, the pure Chemical Engineer also not very versed on the concepts of Chemical Physics as to effectively solve the combined effect of surface tension, particulates surface concentration effect, and the energy potential distribution analysis involved in the affinity versus electrostatic repulsion dynamic that governs the aggregation process. You see, at a minimum, this requires knowledge of Statistical Physics, and chemical engineers hardly every study Statistical Physics. So the alternative to doing it by trial and error, is to contract a Consultant to do it for you.

The temperature and concentration effects are quite significant when aggregating nano-particles as I suspect it will be with the agregation dynamic of "Albumin Fraction" effect; and more so given your mention of the term, micellae (?).

The final consideration is the quality of the super-heated steam for Stage 3; The steam must be such that as the bubbles travel through the wort, the steam thermal energy should sufficiently heat the surrounding water to cause the evaporation into the bubbles. Needless to say, that this will cause the bubbles to grow bigger as they travel upwards and as such travel faster. On the other hand the transfer of latent heat of vaporization to the water of the wort will also reduce the temperature of the steam bubbles and therefore cause the bubbles to shrink in size; hence, there probably exists a state/quality of super-heated steam that provides a balance between these forces of bouyancy, but then that you may also have to determine, again by trial and error or by contracting an engineer to do that for you.

Of course, for each of the above considerations, it is less expensive to accomplish it by computational methods than by experimentation.

Either way, I do believe that you have virtually completed your tasks which is to gain understanding of the issues at play, and now moved on to deciding on the path to follow.

I hope that this is helpful

Your 2 questions (this one and the second about heat transfer) deserve a detailed answer. Could you please send via personal mail you e-mail address so that I can give you some informations in an extended form?

It is difficult to write a thorough explanation on this window and I prefer to use word which cannot be pasted here (at least when I tried it did not work properly).