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Water Bath Heater Design


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#1 Matteo Giorgio Marrano

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Posted 04 December 2008 - 10:41 AM

Good morning,
my name is Matteo, i write from italy and i'm a chemical engineer working as project engineer working for a engineering and construction company.

At the moment i'm working on a project for a desalting plant in an extraction site. The project includes the preheat section and the desalting section.

The first step for me is to Develop the project of the 4 indirect fired heater (water bath heater with water and glycol).

The aim is to preheat the crude oil from 34.4°C to 66°C

I would like to have some help in order to calculate all the parameters that i need in order to build up the unit.

In my hand i have:
-the datasheet of the heater (in attached)
-P&ID
-PFD
-characteristic of crude oil

What is the procedure in order do dimension the heater?
If i understand the water bath heater work like this:

1)a fuel gas rate is used in order to heat the water/glycol mixture present in the vessel
2)the heated mixture heat the oil that passes troug a coil
3)the heated crude oil exit the coil heated at the desired temperature

The problem is that i don't have any info about the water/glycol mixture and i don't know from wich part i have to start to calculate all the system.
Can anybody help me?

These are the main input data:

CRUDE OIL
- Duty requested=3600 kW (900 kW for each heater)
- Crude oil flowrate=183.546 (including 24902 kg/h of water)
- inlet pressure=11 barg
- oulet pressure=10 barg
- Inlet temperature=34.4°C
- Outlet temperature=66°C
- Crude oil density=890,5 kg/m3
- Inlet viscosity=14.2 cP
- Outlet viscoisty=5 cP

WATER BATH
- bath type=water/ethilene glicol
- Bath temperature=80°C
- Etylene glicol concentration=unknow

FUEL GAS
- fuel gas flow rate=281 kg/h
- specific gravity at standard condition=0.8
- Pressure=3.5 barg
- Heating value=11300 kcal/kg

The following data are taken from a commercial offer by a company contacted by us:

- Vessel size=4270mm*15000mm (horizontal vessel)
- expansion tank=680mmx3050mm
- process coils= three paths 6'' XH pipe at 12800mm longx72 tubes combined into one 8'' header
- fire tubes=nr. 2 30''
- burners=2 (they didn't wrote other characteristics)
- stack=?

I would like to understand how that company dimensioned the heater, so we can do the project from ourselves...

The problems are these:
-i don't know how the glycol/water sistem work
-i don't know how to develop the coil
-i don't know what is the best practise to calculate the heat transfer (in my experience i worked only in "simple" heat exchangers but this is different due to the fatc that first i heat the water and then the water heat the crude oil.

Does anybody have some tips for my calculation?
thanks
Matteo



#2 djack77494

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Posted 04 December 2008 - 02:29 PM

QUOTE (Matteo Giorgio Marrano @ Dec 4 2008, 07:41 AM) <{POST_SNAPBACK}>
I would like to have some help in order to calculate all the parameters that i need in order to build up the unit.

What is the procedure in order do dimension the heater?
Does anybody have some tips for my calculation?


Matteo,
Given your statements, you are obviously not qualified to develop fabrication drawings for a fired heater. Yet you seem to be asking for help to do just that. What you as an E&C company should do is to supply a reputable heater manufacturer with your requirements and all needed process information for the heater. The bulk of these inputs is typically done in the form of a process datasheet completed by you and then sent off to potential suppliers. You must tell them about your crude oil - its inlet and desired outlet conditions and all pertinent properties. You must also tell them about the available fuel, power, and control system requirements, local conditions, other available utilities, and perhaps space limitations you have. Water bath heaters are well known devices that can heat difficult fluids that would not well tolerate high localized temperatures and/or regions of high heat flux. A knowledgable fabricator of these devices can design and build a reliable heater meeting your requirements; it is most unlikely that you could do the same (else what value would their extensive experience have?). Please talk to the vendor and help steer him/her to a good design. Then you will have well served your client.

#3 Matteo Giorgio Marrano

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Posted 05 December 2008 - 02:30 AM

QUOTE
Matteo,
Given your statements, you are obviously not qualified to develop fabrication drawings for a fired heater. Yet you seem to be asking for help to do just that.


Hi, here in italy is difficoult to find these kind of devices, so this is the real problem.
In the other case, the problem is only to find a typical design of that devices, i think is like a heat transfer (from hot gas to water, from water to crude oil)..
I have all the available data to do i heat balance, i think..

QUOTE
What you as an E&C company should do is to supply a reputable heater manufacturer with your requirements and all needed process information for the heater.


yes i undertand but we're not talking about a difficoult design (i think)...As we can design in example heater exchanger i thought that it was not so different to design the heater.
The problems is that i didn't find any info for design in books, web etc. It's strange that no book, no website gives info for the design. (on the other way there are a lot of other tips for the calculation of heat exchangers, columns, pumps, vessels etc..)


QUOTE
Water bath heaters are well known devices that can heat difficult fluids that would not well tolerate high localized temperatures and/or regions of high heat flux.


but just to understand how they works, is there any documentation?Is it a simple heat transfer or not?

Thank you for your help..
Matteo

#4 djack77494

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Posted 05 December 2008 - 09:39 AM

QUOTE (Matteo Giorgio Marrano @ Dec 4 2008, 11:30 PM) <{POST_SNAPBACK}>
Hi, here in italy is difficoult to find these kind of devices, so this is the real problem.

Matteo,
I confess to not being Italian, but the last time I looked Italy was in Western Europe. So you're telling me it's difficult to find these devices? I don't believe it. Maybe if you were working in central Africa, but even then... These devices are available beyond the boundaries of North America. Try google.com.

QUOTE (Matteo Giorgio Marrano @ Dec 4 2008, 11:30 PM) <{POST_SNAPBACK}>
yes i undertand but we're not talking about a difficoult design (i think)...


This statement does not give me what we call "the warm fuzzy feeling". If you don't design boilers or fired heaters for a living, then this design IS difficult. This is not something for the uninitiated. If you think you know all there is to know about designing these things, that it's just a bent pipe sitting in a tub of hot water, than go ahead and calculate a surface area. Get your piper to layout a coil, and a local fab shop to put something together for you. Is anyone expecting you to actually produce something that works? Will you/your company have any liability if the thing is totally useless? Will anyone mind if the cost of an inadequate device actually turns out to be much higher than the cost of something that would work? If you answer "yes", find a heater vendor.

QUOTE (Matteo Giorgio Marrano @ Dec 4 2008, 11:30 PM) <{POST_SNAPBACK}>
It's strange that no book, no website gives info for the design. (on the other way there are a lot of other tips for the calculation of heat exchangers, columns, pumps, vessels etc..)

but just to understand how they works, is there any documentation?Is it a simple heat transfer or not?

Well, yes, it is "simple heat transfer". So is a nuclear reactor, depending on your definition of simple. Since you boldly go where you've never been before, your definition is apparently pretty broad. So, your complaint about tips for designing the equipment - I don't understand. I see lots of information on designing boilers. But I know there are an incredible number of difficult-to-discern details involved in the design of an industrial boiler. I wouldn't dream of trying to compile boiler "how to" articles and think I could then do the detailed mechanical design of a boiler. Step 1 to attaining that type of knowledge is to go work for a boiler manufacturer for a decade or two. I assume that your ultimate objective is to produce a low cost, reliable device that will heat your starting material from its initial to your desired final temperature. I can absolutely tell you that the optimum solution starts with a phone call or email to a reputable supplier. Good luck.

#5 Matteo Giorgio Marrano

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Posted 05 December 2008 - 10:29 AM

QUOTE
Matteo,
I confess to not being Italian, but the last time I looked Italy was in Western Europe. So you're telling me it's difficult to find these devices? I don't believe it. Maybe if you were working in central Africa, but even then... These devices are available beyond the boundaries of North America. Try google.com.


Hi jack, thanks for reply...
Maybe my english wasn't perfect, with that kind of words i meant that for me, italian, is difficoult to see with my eyes these kind of device so that the first thing is to imagine how they works..I worked in a refinery and there were no water bath heaters...

We've just contacted a supplier (we're in contact with a chinese one), they gave us a quotation but i wanted to understand HOW they arrived to that results. I'm curious to understand, specially when there is a new device to study...

QUOTE
If you don't design boilers or fired heaters for a living, then this design IS difficult.


ok, that's right..

QUOTE
This is not something for the uninitiated. If you think you know all there is to know about designing these things, that it's just a bent pipe sitting in a tub of hot water, than go ahead and calculate a surface area.


As i said, i would like to understand and not just "send datasheet-receiver offer-buy"...Maybe i put the question in the wrong "style", sorry for that..

In my hand i have the results of the design given by the supplier (the quotation), such as:
-dimensions of the vessel (incl. thickness, nozzles, material of construction)
-type of coil, lenght
-n° of burners, fire tube

BUT I would like to understand how did they reach that design of the device...
In add, we're also a construction company so we usually make from our own the vessels, piping, we decide strumentation based on the P&I etc....
In that kind of offer, the supplier wants to give us the complete skid and this is not good because we would lile to receive first the "process" (and pay it, of course), not the complete device..

QUOTE
I see lots of information on designing boilers. But I know there are an incredible number of difficult-to-discern details involved in the design of an industrial boiler.


tha is a good starting point, even if neither in the Perry neither in the coulson vol. 1 are given information about the water abth heater, am i wrong?I thought that its working is different from a "classical reboiler", also due to the fact that there is the intermediate bath (water+glycol) and the heat transfer is: burning gas-water bath-crude oil..

If you can direct me to some "key-points" it would be great..

QUOTE
I assume that your ultimate objective is to produce a low cost, reliable device that will heat your starting material from its initial to your desired final temperature. I can absolutely tell you that the optimum solution starts with a phone call or email to a reputable supplier. Good luck.


my ultimate objective is to understand how a device works, i think that we have continusly to learn new things....

Jack, as i said maybe i put the answer in the wrong manner...I'm sorry for this misunderstanding...

I repeat, my aim are:
1)understand that new kind of device and process
2)increase my knowledge on the water bath heaters (and what is the starting point to know it)
3)try to build up the device (with the process given by the supplier) due to the fact taht we're a construction company and we have the skills to to that...

Thanks for your precious tips.
Matteo



#6 Art Montemayor

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Posted 05 December 2008 - 11:58 AM

Matteo:

I've followed this thread with interest because it is nostalgic and reminds me of similar experiences I had on the same subject. I offer some comments in the spirit of possibly helping you.

I built my first direct-fired, indirect heater back in 1964, while I was a young engineer running a production company in Peru. I used the services of a local maestro welder, Ermano Galli, who had immigrated to Peru while working for Montecatini and building an ammonia plant in Callao. He was from San Giuseppe di Cairo (near the Piedmont) and was a third generation welder, taught by his father. He fell in love with, and married a pair of brown, Peruvian eyes and stayed in Peru. The man was a genius and an artist to boot. I also was a welder, but he showed me more than I could handle with his skill and artisan craftsmanship. He was a pipefitter as well and could form pressure vessels from steel plates. He even built an MEA reboiler (in the shape of a BKU kettle) for me with nothing more than old steel plate, an "H" steel beam, a large mall, an oxy-acetylene heating and cutting torch, and a Lincoln DC welding machine. In my 48 years as an engineer I have never seen a complete steel worker ("Maestro") such as Ermano Galli. The reboiler lasted over 25 years before it was retired. Enough of nostalgic romance; now for some history and details:

Please refer to the attached specification sheet on a similar heater. This one is for heating wellhead natural gas prior to field separation and treating, but it would also apply to heating a crude oil feed. This is the type of heater I designed and built in Peru with Ermano doing all the difficult fabrication work. Since then, I have specified and purchased various size models and types throughout my career. As Doug has so clearly pointed out, it isn't normally practical or recommended to design and fabricate your own indirect heater. There are practical and legal ramifications that compel an engineer today to seek out the experts who do this for a living and specify the heater you need. To do what I did years ago in Peru would take, what we vulgarly call here in Texas, "cojones" (testicoli) and a lot of desperate need and little choice to do otherwise. I did what I did over 40 years ago because:

  • I had no option; we needed a heater and the company was in deep economic woes. If I didn't succeed, the failure of the company was imminent. We had to do something.
  • Time was of the essence. We needed production immediately, within days. We had little or no hard currency, no time for specifications, quotations, evaluations, and waiting around to import the equipment.
  • I was very familiar with the design since I am Texas-born and reared. The design and concept evolved here in Texas and Oklahoma where "Oil-patch" (remote located) heaters were needed to heat high pressure natural gas and crude oil.
  • My father was a shipyard steel worker who could drive rivets, weld, and hang steel. I was raised in that environment and steel fabrication was familiar to me.
Unless you are facing similar circumstances, like Doug I would not recommend you attempt to design and fabricate your own indirect heater. I know there are qualified and recognized Italian fabrication shops who could do what Ermano Galli and I did years ago – and do it much better and safer.

If you are interested in knowing more about the basic design and concept, then I can offer this experienced information and background:

  • Design the Direct-fired tube bundle with no more than 8,000 Btu/hr/ft2 of heat flux. This is an experienced and empirical value gained through hands-on experience that allows for reasonable and safe operation.
  • Do not expose your heater tube or bundle to direct impingement by the burner flame. This will destroy the bundle in little time.
  • a 50% weight ethylene glycol solution is what is normally employed in the "bath".
  • If you can fire natural gas or a similar gaseous fuel, the combustion can be done with an induced draft if your chimney stack is high enough – usually no higher than 10 to 15 feet.
  • You can use a 180 degree, mitered return on the heater coil made from fire box quality steel.
  • Protect the unit with a flame-out alarm and shutdown instrument package. You should always monitor the existence of a flame in the firebox.
  • Design the firing mechanism such that you automatically purge the firebox after a flame-out and always prior to burner ignition.
The heat transfer theory and equations that you find in Don Q. Kern's famous book, "Process Heat Transfer" is what I used in my designs and, believe it or not, is also what the majority of today's fabricators also use. This design of direct-fired heater is not found in the usual literature and you would find it hard to find design guidelines for it. I have some fabricator literature and sizes, but I would wait for your specific question on specific details before attempting to give you a lecture or tutorial on the design.

I hope this information is of help to you.

Cordiali saluti.

Attached File  Indirect_Fired_Heater.xls   54.5KB   1066 downloads

#7 Matteo Giorgio Marrano

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Posted 05 December 2008 - 03:39 PM

QUOTE
I've followed this thread with interest because it is nostalgic and reminds me of similar experiences I had on the same subject. I offer some comments in the spirit of possibly helping you.


Hi Art, thank for your partecipation...

QUOTE
I built my first direct-fired, indirect heater back in 1964, while I was a young engineer running a production company in Peru. I used the services of a local maestro welder, Ermano Galli, who had immigrated to Peru while working for Montecatini and building an ammonia plant in Callao. He was from San Giuseppe di Cairo


i think it was a great person looking how you describe him..smile.gif

QUOTE
The reboiler lasted over 25 years before it was retired. Enough of nostalgic romance; now for some history and details:


the old skilled engineers are 10000 ft above young engineers (like me), there's nothing to do..

QUOTE
Please refer to the attached specification sheet on a similar heater. This one is for heating wellhead natural gas prior to field separation and treating, but it would also apply to heating a crude oil feed. This is the type of heater I designed and built in Peru with Ermano doing all the difficult fabrication work.


i see..thanks

QUOTE
Since then, I have specified and purchased various size models and types throughout my career. As Doug has so clearly pointed out, it isn't normally practical or recommended to design and fabricate your own indirect heater.


as i told above, i work for a company of engineering and costruction. We contacted a supplier of bath heaters (AMR) and they gave us an offer including complete datasheet, P&I, dimension of the vessels, quoted sketch of the vessel.They gave us the price including the vessel but we don't want the complete system but only the "process".
In fact, according to the P&I given by supplier, we do all detailed engineering like build the vessel (according to specification), buy strumentation, design piping layout etc...

Personally i would like to learn how to design that kind of heater, also to understand more of this argument.

In detail what i'm trying to do is to understand HOW the supplier obtained the given data like:
-overall dimensions of the vessel
-shape and characteristic of coil
-how is made the water bath (why we put 50/50% glicol?why we don't use only water?)

i would like to "go rewind" and understand all the calculations that they made

As i said in the first post the designed water bath heater have a duty of 3600 kW.
I have the complete datasheet filled and the overal design and drawings given by supplier..

I can calculate the fuel gas necessary to give that kind of duty to the water and then to the crude oil (with overdesign of the case) but:
-i don't know how "works" the system water/glycol instead of a simple "hot water"
-i would like to understand how to design a coil (ok, the first step is to determine the surface area needed to exchange the 3600 Kw from the hot bath to the crude oil, right?)
- and so on...




#8 Matteo Giorgio Marrano

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Posted 05 December 2008 - 03:39 PM

QUOTE
Unless you are facing similar circumstances, like Doug I would not recommend you attempt to design and fabricate your own indirect heater. I know there are qualified and recognized Italian fabrication shops who could do what Ermano Galli and I did years ago – and do it much better and safer.


read above....

QUOTE
If you are interested in knowing more about the basic design and cocept, then I can offer this experienced information and background:


yes it would be great, i'm very courious, i think that we have to learn every day of our life and work..
I have only to resume a bit of theory, if possibile with your help..

QUOTE
-Design the Direct-fired tube bundle with no more than 8,000 Btu/hr/ft2 of heat flux. This is an experienced and empirical value gained through hands-on experience that allows for reasonable and safe operation
-Do not expose your heater tube or bundle to direct impingement by the burner flame. This will destroy the bundle in little time.
-a 50% weight ethylene glycol solution is what is normally employed in the "bath".
-If you can fire natural gas or a similar gaseous fuel, the combustion can be done with an induced draft if your chimney stack is high enough – usually no higher than 10 to 15 feet.
-You can use a 180 degree, mitered return on the heater coil made from fire box quality steel.
-Protect the unit with a flame-out alarm and shutdown instrument package. You should always monitor the existence of a flame in the firebox.
-Design the firing mechanism such that you automatically purge the firebox after a flame-out and always prior to burner ignition.


very good tips..
monday i will post a drawing that i made looking at the p&i and offer of the supplier..
QUOTE
The heat transfer theory and equations that you find in Don Q. Kern's famous book, "Process Heat Transfer" is what I used in my designs and, believe it or not, is also what the majority of today's fabricators also use.


i have to re-find it...During my study i studied on coulson vol.1 e coulson vol.6, even if know i have only coulson 1 and Perry because i moved from tuscany (now i live in milano)

QUOTE
This design of direct-fired heater is not found in the usual literature and you would find it hard to find design guidelines for it. I have some fabricator literature and sizes, but I would wait for your specific question on specific details before attempting to give you a lecture or tutorial on the design.


thank you so much...if you want we can discuss via mail if you want...
I don't know if my answers are clearly written....

QUOTE
Cordiali saluti.


grazie mille, i hope i will learn many things from your tips..
Matteo




#9 Matteo Giorgio Marrano

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Posted 12 December 2008 - 10:22 AM

Good afternoon,
i've tried to design the water bath heater with some tips that i found on books, internet, and Art's documents. I also found a sizing of a water bath heater in excel made by someone in my company but im' still trying to "decrypt" it and going backword in order to comprehend the steps..

I've calculated the following parameters:
1)required area needed for the heat exchange (210 square meters)
2)i've assumed the following:
-lenght of the tubes: 12 m,
-diameter of tubes: 4''
-pitch : 1.25*external diameter
3)I've calculated that i need 46 tubes.

the following step is to decide the arrangement of the coil bundle. Considering the fact that the coil will stay in a half of the vessel (due to the space occupied by the firetubes), what would be the best configuration of this bundle?.

I think that if i split the 46 tubes in 3-4 coil the heat exchange is better than if i use 1 coil of 46 tubes....Is it right?Obviously i need the space to do it..

Another question about the direction of the oil flow: Do i have to let the cold oil passes first in the hot region near the fired tubes or the opposite?
Substantially, with this arrangement the cold oil enters at approximately half of the vessel and exits approx. at the top of the vessel..I'm posting a drawing to explain what i mean..


p.s. Art your pdf were great, specially for the theory. Unfortunately the calculation is done only using their charts, that are valid only for low duty water bath heaters (2 million of BTU while mine is more than 10 millions)..

thanks
matteo

Attached Files



#10 Art Montemayor

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Posted 12 December 2008 - 07:56 PM

Matteo:

Refer to the attached Excel Workbook. I can fit in about 100 tubes (of the same diameter as yours) within the water bath heater.

Look at the way I would lay them out. My tubes are shown in RED.
Attached File  Matteos_Water_Bath_Heater_Tube_Layout.xls   798KB   744 downloads


#11 Matteo Giorgio Marrano

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Posted 13 December 2008 - 05:06 AM


Hi Art,

i see that in the way you drawned the sketch there are more tubes..

My 47 tubes derived from a calculation, not from the available space....
For that reason i tried to arrange the tubes in a coil divided in 3 paths as shown in figure and i was wondering if there are some tips for the coil arrangements (like: the cold oil enters at the middle end exit near to the top of the vessel or the opposite).


ciao
Matteo

#12 gg1

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Posted 17 December 2008 - 03:53 PM

www.terisales.com

We have alot of experience with indirect fired water bath heaters

#13 djack77494

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Posted 17 December 2008 - 05:44 PM

QUOTE (gg1 @ Dec 17 2008, 12:53 PM) <{POST_SNAPBACK}>
www.terisales.com

We have alot of experience (That's what is needed) with indirect fired water bath heaters

Matteo,
You've gotten some interesting and useful guidelines from Art as well as practical advise. My suggestion to you at this point is to go out and buy your heater from a reputable and experienced water bath heater manufacturer. Study the drawings and documentation that come with the heater, and, if possible, participate or remain active in the startup and operation of the heater. Talk to the manufacturer's representative and to your instrument and controls people. Find out about what parameters govern the design - perhaps things like allowable heat flux and the heat release per volume of firebox. Things like that. If you follow these steps you will not become an expert in water bath heaters, but you WILL achieve a lot of knowledge about how they are designed and operated. Much more so than if you strive to layout a coil in a tub of warm water. We have an expression that you can learn things the easy way or the hard way. In your case, I'm not even sure that you would learn that much if you chose the hard way. Choose the easy way, please.

#14 Matteo Giorgio Marrano

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Posted 18 December 2008 - 02:16 AM


yes jack that is what im'm doing....We're in contact with AMR Canada, they're good manufactorers of water bath heater and desalters. What i'm doing is studying the drawings they sent us and trying to understand why they used in example 70 tubes instead 40 or if the heat exchange is enough for the process.
Surely i will not become an expert of water bath heater, i know, i will only "comprehend" what the company is selling to us..

I also tried to made a calculation file (in mathcad) that gave me help to understand how to size the water bath (a first sizizing, of course, not a detailed).

thanks

#15 gg1

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Posted 18 December 2008 - 11:28 AM

To help your understanding:

There are many factors that go into the sizing.

The amount of heat transfer (duty) typically determines the general overall size.

The coil bundle is based on the fluid flow rate and erosion velocities as well as surface area requirements. The number of tubes(and length) is based on the surface area required. The wall thickness and number of flow paths is based on fluid flow.

The firetube is limited, as these guys have mentioned, by the design heat flux, which is duty over area.

Once you have these sized, you try to squeeze them into the smallest shell possible.
Note: The shell itself is not considered a pressure vessel so no code requirements exist, however the coil bundle is and these codes must be considered.

Further, you have to decide on a burner management system. There are many options available such as automatic pilot relighters, plc remote control capabilities and so on.

If you run in to any specific questions along your way, we would be glad to help.


#16 Art Montemayor

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Posted 18 December 2008 - 12:50 PM

Matteo:

What I've tried to show you is that you can fit in more tubes than the ones you showed. And they don't have to be oriented in the vertical position. The number of tubes employed (or actually the total heat transfer area applied) are dependent on a variety of other things besides the answer obtained by using the heat transfer equations found in Kern and other books. Listen to this carefully because what I state is backed by 48 years as an engineer: In order to determine the total heat transfer area to be used, you must know a variety of other factors - such as:

1) the certainty of the design data that you are given or that you obtain for design;
2) the position and the responsibility you hold as designer. If you are designing the heater for someone else (a client) and that person demands a guarantee of performance, you must apply a contingency factor to the area (a multiplier) in order to ensure that ALL factors (known & unknown) are taken into account. That is why there may be an excess of heat transfer area.
3) Another source for excess heat transfer area is that the client may demand extra capacity (in the future). Or, there may be fouling (presently or expected in the future) that has to be compensated.

Note the excellent brochure that gg1 has led us to through his company. I don't know what capacity gg1 has in his company or the extent of his experience, but the mere fact that his company is Oklahoma-based already classifies him in my mind as a potential EXPERT. Remember what I stated earlier: these type of units were invented and developed in what is Texas and Oklahoma oil fields about 100 years ago. I would listen very carefully and note down everything that gg1 offers as advice on these units. Note the developed features of the unit featured in the brochure. It has an expansion tank. This is an extra. Some units don't have this feature. It serves to ensure that the unit is nearly 100% filled with heat transfer solution and also serves as an expansion tank where the level can be monitored and controlled. There are a lot of other features - some subtle, others complex - that may not be appreciated by the unlearned or unexperienced.

gg1:

Thank you very much for your valuable and experienced advice on this subject - expecially for the access to the website and the brochure. I sinerely hope that you continue to visit our Forums and share some profitable experience with our members - expecially in the art of knowing how to Specify and describe a direct-fired heater to a designer/fabricator.


#17 gg1

gg1

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Posted 18 December 2008 - 01:41 PM

Art

Thanks for your welcome note and I appreciate your vast knowledge and willingness to share with everyone. I can assure you that I am no expert, as I am a beginning engineer also. However, I have been fortunate enough to learn from many experts like yourself, that have the knowledge only obtained through experience. The company I work for specializes in these heaters and I get to study them inside and out on a daily basis. There are guys here that have a ton of experience and have had their hands in on thousands of these heaters over the years. I will definitely continue to visit this forum, I am glad I found it. In the near future I will definitely require the experience from this board in designing new equipment...and I will gladly help with your heater questions in exchange for access to your knowledge of processing equipment. By the way, we are currently redesigning the website, I would love to hear any suggestions!

In response to your comments regarding design, you are 100% correct. There are so many things to consider, if you were to start from scratch, undoubtedly you would run into trouble.

Again, if you run into or have any specific questions, I will be glad to help any way I can.

#18 Matteo Giorgio Marrano

Matteo Giorgio Marrano

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Posted 20 March 2009 - 07:41 AM

Goodmorning guys, after some weeks i return to this topic:))

A simple question for you:
Why in wather bath heater we use the coil instead a “classical” tube bundle like in Heat exchangers?Does it depends on the fact that the flow in the tubes is turbulent and the flow outside the tubes (the water bath) is depending on “natural convection”?Or there are some other reason?

Another question: how we can do to extimate the heat exchange coefficients h(tubes), h(shell) in order to calculate the overall U?

In my calculation I used the following, derived from kern and my university books:

- inside tube hi – crude oil
hi: (k/d)*0.027*Re^0.8*Pr^0.33
Is this correct?The value that I found are different from the one calculated with Hysys (I founded hysys results in a sheet buy I’m not able to re-calculate them with hysys)

Where:
Re: (density*velocity in tubes*inner diameter)/viscosity
Pr: (specific heat*viscosity)/K
K: conductivity

- he(shell) – water bath
Do I have to use the empirical formula in wich is present the Grashoff Number? Can you give me the formula pls)


I would like also to share my step-by-step of sizing of a water bath heater (overall sizing); I don’t know if it is right or wrong, maybe there are some points that I forgot or in wich I made some error

Regards
Matteo




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