Why Dimples on Jacketed Fermenters?

[6Tap]

Does anyone know why some jacketed
Fermenters are built with dimples?

Supposed to help with cooling more?

See pic below for an example.

Just curious why?

Any pros/ cons?


Thanks fo your response.

 

[Blazinlow86]

My guess is for strength. It's a guess though

 

[day_trippr]

Could very well be turbulators...Or they may effect positive spacing between the liner and jacket (I don't know how deep the spacing is on such vessels).

[edit] Is the jacketed section just the band around the middle? If so, I expect those dimples establish and maintain the gap...and would also act as turbulators...

Cheers!

 

[SanPancho]

turbulent flow. possibly as stand-offs as well to keep the jacket thickness uniform. but definitely turbulent flow.

 

[6Tap]

Dimples are mainly around the middle of the fermenter.
Thanks.

 

[doug293cz]

Gap maintenance is the primary purpose.

Brew on

 

[Nokt]

Daleks........

 

[SanPancho]

if gap maintenance was the answer why dont insulated mash tuns and kettles have dimples? and what about fermenters with no dimples? see alot more of those than dimple jackets.

 

[Brickman]

It helps with the aerodynamics when they fly through the air.

 

[SanPancho]

or maybe they were damaged.

Hulk smash bad beer.

 

[doug293cz]

if gap maintenance was the answer why dont insulated mash tuns and kettles have dimples? and what about fermenters with no dimples? see alot more of those than dimple jackets.

If the insulation isn't highly compressible, the the insulation will do the gap maintenance. People actually build airplane structural components out of fiberglass/epoxy skinned foam cores.

Do you have examples of jacketed fermenters without dimples? Lots of non-jacketed fermenters have temp control via internal or external coils, or cool/heat spears.

Brew on

 

[SanPancho]

https://discussions.probrewer.com/s...bbl-10bbl-15bbl-20bbl-best-price-from-Cassman

https://discussions.probrewer.com/s...ERMENTERS-3-120-BBLS!-American-Beer-Equipment

https://discussions.probrewer.com/showthread.php?56805-Custom-American-Made-Fermenters

no dimples.

 

[SanPancho]

mash tun and kettle/HLT.

https://discussions.probrewer.com/showthread.php?67902-10-bbl-Direct-Fire-Brewhouse

no dimples.

 

[doug293cz]

mash tun and kettle/HLT.

https://discussions.probrewer.com/showthread.php?67902-10-bbl-Direct-Fire-Brewhouse

no dimples.

Foam (polyurethane) insulation as spacer.

Brew on

 

[SanPancho]

and the fermenters? they must be using some other sort of fibrous insulation like batting?


https://discussions.probrewer.com/s...Fermenters-Unitanks-Brite-Tanks-Serving-Tanks

and what about these? PE insulation and yet still have dimpling on the interior.

 

[doug293cz]

https://discussions.probrewer.com/s...bbl-10bbl-15bbl-20bbl-best-price-from-Cassman

Foam core (insulation) spacer

https://discussions.probrewer.com/s...ERMENTERS-3-120-BBLS!-American-Beer-Equipment

American Beer Equipment's web site isn't responding, but I suspect their clad tanks are foam insulated.

https://discussions.probrewer.com/showthread.php?56805-Custom-American-Made-Fermenters

According to Pioneer's web site the tanks are insulated and clad, so insulation spacer

no dimples.

It's tanks that have coolant flow thru the space between the vessel and jacket that need the dimples.

Brew on

 

[SanPancho]

all of those fermenters linked to are glycol jacketed. no dimples on the exterior shell. one has tiny dimples on interior shell only.

 

[doug293cz]

and the fermenters? they must be using some other sort of fibrous insulation like batting?

More likely polyurethane foam insulation. You would only use fiber bat insulation in areas that get too hot for the foam.

https://discussions.probrewer.com/s...Fermenters-Unitanks-Brite-Tanks-Serving-Tanks

and what about these? PE insulation and yet still have dimpling on the interior.

I see some distorted reflections in those pics, but nothing that looks like intentional dimples. And what would be the purpose of dimpling the inside of a tank?

Brew on

 

[doug293cz]

all of those fermenters linked to are glycol jacketed. no dimples on the exterior shell. one has tiny dimples on interior shell only.

The exterior shell is the insulation cover. You can't tell what the cooling jacket looks like in the photos.

Brew on

 

[SanPancho]

the sungood tanks have no dimples on exterior shell. glycol jacketed. PE insulation. and dimples on the interior shell.


if you dont wanna listen to what im saying maybe you might wanna take the word of some folks who've been in the biz for generations.

https://www.paulmueller.com/tank-co.../stamped-dimple-jacket-heat-transfer-surface/

here's another firm we've had stuff from. at the bottom you see the graph showing how dimple jackets have less flow than channel designs which is due to the turbulent flow vs the smooth laminar flow of a channel type.
http://srss.com/stainless-steel-tank-cooling-heating-jackets/

and of course, good old wikipedia as it popped up as i looked for our manufacturer's info on dimple jackets.

• Dimple Jackets. A thin external shell is affixed to the vessel shell with spot welds located in a regular pattern, often about 50 mm on center both horizontally and vertically. These so-called dimples impart turbulence to the heating or cooling media as it flows through the jacket.

 

[doug293cz]

the sungood tanks have no dimples on exterior shell. glycol jacketed. PE insulation. and dimples on the interior shell.


if you dont wanna listen to what im saying maybe you might wanna take the word of some folks who've been in the biz for generations.

https://www.paulmueller.com/tank-co.../stamped-dimple-jacket-heat-transfer-surface/

Ok, you take a sheet of this dimpled SS, wrap it around the vessel you want to heat/cool, the bottom of the dimples contact the vessel wall, you weld around the circumference of the opening at the bottom of each dimple (to the vessel wall), weld around the top and bottom, and you have a cooling/heating jacket. There are no dimples on the inside of the vessel. If you put a shroud around the assembly, and fill the gap with urethane pour foam, you have an insulated, jacketed vessel. no dimples on the inside of the vessel, and no dimples visible from outside. The dimple depth sets the stand-off between the vessel wall and the outside wall of the jacket.

here's another firm we've had stuff from. at the bottom you see the graph showing how dimple jackets have less flow than channel designs which is due to the turbulent flow vs the smooth laminar flow of a channel type.
http://srss.com/stainless-steel-tank-cooling-heating-jackets/

and of course, good old wikipedia as it popped up as i looked for our manufacturer's info on dimple jackets.

• Dimple Jackets. A thin external shell is affixed to the vessel shell with spot welds located in a regular pattern, often about 50 mm on center both horizontally and vertically. These so-called dimples impart turbulence to the heating or cooling media as it flows through the jacket.

Here's the flow chart from the second reference:

As I read this chart, in order to get 25 gpm flow thru the jacket, you need 10 psi of head at the jacket inlet for the channeled jacket, and 23 psi for the dimpled jacket. That means you need a bigger pump to get the same flow with a dimpled jacket vs. the channeled jacket. I don't see that as an advantage for the dimpled jacket. There is no data that the dimpled jacket at lower flow provides better heat transfer than the channeled jacket at higher flow.

Brew on

 

[6Tap]

WOW thanks for the responses!
All this time I thought it all started when a manufactures fermentor fell over and dented so they Just uniformly dented the rest of the fermentor for looks. Turns out that the manufacture of the dimpled fermenter I am interested in Located in China sells their fermenter for the same price as Stout Tanks sells their non dimpled unit for $2 k which is still a lot of $$. Fu.. thanks to
For HEL’s I am going to just charge it so I can add a second one... Cheers

 

[SanPancho]

christ, you just wont stop. they literally stated it has better heat transfer than channel design.

turbulent vs laminar flow. school yourself on the fundamentals. guess which one has higher GPM flow rate?

https://www.advantageengineering.com/fyi/156/advantageFYI156.php

 

[6Tap]

I also have a wall Ac unit to Contol my brew room temp so I don’t really give a f... about some channelized bs design since I always pay the max cost on electricity and water. I was just curious about why some
Have dimples. Question answered. Thanks.

Cheers peeps!!

 

[SanPancho]

i lost you at the end there. are you going with stout or ordering from china?

remember if you order direct from china there's shipping and then customs fees on top. shipping might not be too bad, if you're on the coast. we're west coast, and they literally drop it at our port here for about 200-400 per tank depending on size. if you need to get it onto a truck east of the rockies you're gonna see that price go way up.

and customs fees are a *****. the customs duties/taxes themselves arent that bad on brew equipment, what gets you is the fees. they're typically flat fees, 50 here, 200 there, etc. it adds up, fast.

once you tally up all those extras, the stout tank looks alot more reasonable.

 

[6Tap]

i lost you at the end there. are you going with stout or ordering from china?

remember if you order direct from china there's shipping and then customs fees on top. shipping might not be too bad, if you're on the coast. we're west coast, and they literally drop it at our port here for about 200-400 per tank depending on size. if you need to get it onto a truck east of the rockies you're gonna see that price go way up.

and customs fees are a *****. the customs duties/taxes themselves arent that bad on brew equipment, what gets you is the fees. they're typically flat fees, 50 here, 200 there, etc. it adds up, fast.

once you tally up all those extras, the stout tank looks alot more reasonable.

SanPancho,

West coast is the best coast!
10-4 on the Stout Tanks direction.
That’s where I am heading.
Any ideas how I can keep this purchase a secret from my wife?
Cheers [emoji482]

 

[SanPancho]

bitcoin?

 

[day_trippr]

Send her on a vacation...

 

[doug293cz]

christ, you just wont stop. they literally stated it has better heat transfer than channel design.

turbulent vs laminar flow. school yourself on the fundamentals. guess which one has higher GPM flow rate?

https://www.advantageengineering.com/fyi/156/advantageFYI156.php

Yes turbulent flow has a better heat transfer coefficient than laminar flow. But the transfer coefficient is only one term in a complex formula that includes flow rate, surface area, temperature delta, thermal conductivity of the walls, heat capacity of the coolant, etc. Very often the transfer coefficient is not the most important factor, and none of your references provided any quantitative data, other than flow rate vs. pressure. A higher flow rate maintains a higher delta T, and that improves thermal transfer. The chart showed the channel jacket has higher flow for the same pressure (pump size). There is no data on actual heat transfer using a dimpled jacket vs. channel jacket in the references that I saw. If I missed something, please point out exactly where it is. A screen shot or short quote would be great.

The other thing is that whether you have turbulent or laminar flow depends on the Reynolds number. A dimpled jacket will reach the Reynolds number threshold for turbulent flow at lower flow rates then a non-dimpled jacket, of the same area, gap space, and surface smoothness. Can't make a general statement on Reynolds number of dimpled jacket vs. channeled jacket, since the flow cross sections will usually be very different.

"they literally stated it has better heat transfer than channel design" I didn't see anything that I would interpret as saying this. Can you provide a direct quote of what you think said this, along with the link where it can be found.

The OP has gotten the information they were looking for, so the thread has achieved its original purpose. This extended debate on thermal design may be getting tedious for other readers. I suggest we move it to a PM conversation, unless we have readers speak up wanting to see the discussion thru.

Brew on

 

[Beholder]

I work in turbomachinery and develop heat transfer technology, so a sectional dimension is the only element missing to understand where this design sits in HT space. The principle is correct that turbulent trips enhance heat transfer, but one can also design in an unintelligent manner and achieve higher HTCs but higher pressure drop, thereby slowing flow and achieving lower overall heat flux.

In this application, the dimples look sized for establishing cylindrical concentricity rather than helping to maintain turbulent flow at lower flow rates.

 

[doug293cz]

I work in turbomachinery and develop heat transfer technology, so a sectional dimension is the only element missing to understand where this design sits in HT space. The principle is correct that turbulent trips enhance heat transfer, but one can also design in an unintelligent manner and achieve higher HTCs but higher pressure drop, thereby slowing flow and achieving lower overall heat flux.

In this application, the dimples look sized for establishing cylindrical concentricity rather than helping to maintain turbulent flow at lower flow rates.

The real metric is total energy cost required to cool the vessel. This has to include the cost of cooling the glycol, and the cost of running the pump. The overall rate of cooling is easily measured. You just need to know the coolant inlet, temperature, the coolant outlet temperature, the coolant heat capacity, and the coolant flow rate. The heat removal rate is then:

Cooling Rate = Heat Capacity * Flow Rate * (Inlet Temp - Outlet Temp)
​

Heat capacity is in units of energy / (mass * temp delta), Flow rate is in units of mass / time, thus cooling rate is in units of energy / time or power. If using Imperial units then heat capacity is BTU / lb / degree F, flow rate is lb / hour and cooling rate is BTU / hour. So, you can get the same cooling rate at higher flow and lower delta T, or lower flow rate and higher delta T. To get the total power required for cooling you convert the pump power required from horsepower to BTU/hr, or the cooling rate from BTU/hr to horsepower. Then you add the cooling power, the coolant chiller power, and the pump power to get the total power required.

Until you know the total power required for one type of jacket & vessel vs. another type, you can't say which one is better than the other. Comparisons based on heat transfer coefficient between the fluid and vessel, or flow rate thru the jacket are meaningless.

Brew on

 

[Beholder]

The real metric is total energy cost required to cool the vessel. This has to include the cost of cooling the glycol, and the cost of running the pump. The overall rate of cooling is easily measured. You just need to know the coolant inlet, temperature, the coolant outlet temperature, the coolant heat capacity, and the coolant flow rate. The heat removal rate is then:

Cooling Rate = Heat Capacity * Flow Rate * (Inlet Temp - Outlet Temp)
​

Heat capacity is in units of energy / (mass * temp delta), Flow rate is in units of mass / time, thus cooling rate is in units of energy / time or power. If using Imperial units then heat capacity is BTU / lb / degree F, flow rate is lb / hour and cooling rate is BTU / hour. So, you can get the same cooling rate at higher flow and lower delta T, or lower flow rate and higher delta T. To get the total power required for cooling you convert the pump power required from horsepower to BTU/hr, or the cooling rate from BTU/hr to horsepower. Then you add the cooling power, the coolant chiller power, and the pump power to get the total power required.

Until you know the total power required for one type of jacket & vessel vs. another type, you can't say which one is better than the other. Comparisons based on heat transfer coefficient between the fluid and vessel, or flow rate thru the jacket are meaningless.

Brew on

You have the principles right, though based on your assessment, one would do this assessment empirically, since I presume you do not have detailed knowledge of all the system component characteristics on which to develop a model for assessment. (Since naturally you would need the correlations within each system in order to accurately model it...)

Instead, comparisons based on heat transfer can be used to assess pump cycling time, which is a reasonable assumption given that your pump does not vary in power demand over flow resistance. Thus, lower power consumption is achieved via shorter duty cycle of the pump.

In addition turbulent transition will shift somewhat based on fluid temperature, but not significantly ~10 C, as the typical range of optimized glycol fluid temp.

In any case, no need to go to first engineering principles to solicit agreement - not sure your background and experience, so happy to simply agree to disagree if my arguments aren’t compelling.

 

[doug293cz]

You have the principles right, though based on your assessment, one would do this assessment empirically, since I presume you do not have detailed knowledge of all the system component characteristics on which to develop a model for assessment. (Since naturally you would need the correlations within each system in order to accurately model it...)

Instead, comparisons based on heat transfer can be used to assess pump cycling time, which is a reasonable assumption given that your pump does not vary in power demand over flow resistance. Thus, lower power consumption is achieved via shorter duty cycle of the pump.

In addition turbulent transition will shift somewhat based on fluid temperature, but not significantly ~10 C, as the typical range of optimized glycol fluid temp.

In any case, no need to go to first engineering principles to solicit agreement - not sure your background and experience, so happy to simply agree to disagree if my arguments aren’t compelling.

Not trying to describe how to model the system, just describe a pretty simple way to measure the actual performance at a "black box level." This avoids having to actually know thermal transfer coefficients, Reynolds number in the jacket, flow distribution in the jacket, and other complex things like that.

Yes, shorter duty cycle means less average power for a particular pump.

Brew on

 

[SanPancho]

The reason for the design is cost efficiency. These are single wall tanks with jackets, but no insulation.

A quick recap of a nano unit from china-
2bbl domed brite
Single wall- 1300
Add dimple- 1400
Jacketd, insulated, shelled- 2200

Thats a +50% premium for insulation and external shell. And quite a bit more shipping weight.