11 replies to this topic

[KR]

Dear all,

Thanks for the previous help/suggestions.

I want to calculate insulation and/or heat required for the storage tank. The description is as below. There are 6 tanks in a room and the room temperature is maintained around 15 deg C using gas [Natural Gas] heater. All the tanks are of same dimensions [2.3m long,3.1m wide, 0.006mm thick and 2.55m high] and each tank contains 17000 kg of organic viscous liquid which are entering into the tanks at 45C and temperature has to maintained around 35 deg C when we take the liquid out of the tank [Time is not fixed - liquid may be required after 2 days or 3 days or 1 week] . The MoC of tanks is carbon steel. The only known property of liquid is its specific heat i.e. 2 kJ/kg C.

I want to find the thickness of insulation [glass wool] required and if necessary, additional heat required.

I have calculated the amount of heat a liquid can [afford] lose while dropping down temp from 45 to 35 deg C by simple m*Cp*dT equation. I can calculate heat loss through conduction once inside and outside SURFACE temp of tank is known but how to calculate those two temperature.

Any hint or help would be appreciated. I don't want the answer!

Thanks in advance.
Komal

[Art Montemayor]

Komal:

The answer to all your needs in resolving this application is to obtain a copy of the great article written by Jimmy D. Kumana and Samir P. Kothari, "Predict Storage-Tank Heat Transfer Precisely", in the March 22, 1982 edition of Chemical Engineering Magazine.

I am currently trying to transcribe this great source of engineering know-how into an Excel workbook. I am 30% of the way to finishing it. Sorry I can't offer it to you yet.

You will find the theory, recomendations and even a worked example in this article.

[ankur2061]

Komal,

Hi this is Ankur.

Suggest, you read the two previous posts on the topic of heat loss. Althought the posts relates to heat loss from insulated pipe the same principle applies for tanks also.

http://www.cheresour...?showtopic=6248

http://www.cheresour...mp;hl=heat loss

Another post specifically meant for heat loss in storage tanks is:

http://www.cheresour...x...033&hl=heat

Happy reading.

Regards,
Ankur.

[KR]

Dear Ankur,

Thanks for your help and I have gone through those links but no hint yet as I dont have many information which I need to start with.

Dear Art,

I appreciate your suggestion but I dont think it would be available to me within my time frame.

@ All

Any help?

Thanks

[ankur2061]

Komal,

Can you try to formulate your problem in a excel sheet preferably with a sketch and leave some blank cells which need to be filled up with the required data to arrive at the solution of the problem? I find this the most convenient way to arrive at solutions for engineering calculations and other forum stalwarts like Art also prefer it this way. This gives a very precise method of tackling engineering calculations.

Regards,
Ankur.

[Joyy]

Hi,

You can download copy of the article "Predict Storage-Tank Heat Transfer Precisely" by Jimmy D. Kumana and Samir P. Kothari, March 22, 1982 edition of Chemical Engineering Magazine, as suggested by Art Montemayor, from the below link:

http://ifile.it/90u1ok2

Joyy

P.S. It was uploaded by gusgon in the forum http://www.egpet.net/vb/t2857.html

[KR]

@Joyy,

Nup. its not working dear. Anyways thanks for that.

@Ankur

Please find the attached file where I have described the prob briefly and written remarks where necessary.

Thanks very much for that.

Regards,
Komal

Attached Files

•  Heat_Loss_tank_farm.xls   30.5KB   756 downloads

[KR]

Sorry, I forgot to mention that time is not fixed to take the liquid out of the tanks [daily, weekly etc - its based on the requirement], so I think we need to calculate drop in temp per unit time as well.

[DRS]

Jimmy KKumana's paper, as suggested by Mr Montemayor, is the best and precise one I ever came across. You can use approximate methods given in DQ Kern and JP Holman using Nusselt Number correlation by Churchill.

Chromolax has some discussion on tank heating using approximate overall heat transfer coefficients, which you can use till you get your hands on Jimmy Kumana's paper.

http://www.chromalox...TankHeating.pdf

You can safely assume tank wall temperature as average of fluid (or vapor space) and ambient temperatures. For bottom floor, it is average of ground and liquid temperatures.

[GTYJ81]

Komal,

Another source of information that may be of help to you in solving this problem is the Tranter Platecoil Product Data Manual. There is a section within this manual that gives the procedure for calculating the heat loss from a storage tank and some example problems from which I believe you could glean some useful information. The website is www.tranter.com. You will have to register on the site to access the Product Data Manual that I'm referring to. I could also try to e-mail you a copy of the manual if you supply your address.

[Joyy]

Komal,

The above link is still working fine for me.

Anyways, I am attaching the file here for your ready reference.
Joyy

Attached Files

•  predict_storage_tank_heat_transfer_precisely.pdf   1007.67KB   983 downloads

[bigdisu1]

Working through this example from the downloaded .pdf, I get stuck on p130. I am putting this example into a excel spreadsheet for future use and one part of my calculation does not come out like the example shows it should

The calculation on P130 shows the Grashof # for the liquid phase to be L^3*p^2*g*B*deltaT/u^2 = 97.5L^3*deltaT

Using the data from Table II
p = 4.68 lb/ft^3;
B = 1*10^-6 1/F;
g = 4.17*10^8 lb/ft^2;
u = 40 cP=96.8 lb/ft-hr (convert 1cP is 2.42 lb/ft-hr )

When I make this calculation, my result is .975L^3*deltaT. I am obviously off by a factor of 2 but I cannot see where I am making the mistake and want to know if it is an error on my part or an error in the document.

Any help is appreciated.