Thermal fluid Heater sizing question 3

[suocsiv]

We are in the design procces of an AST for fuel oil (380cSt)for vessel bunkering supply.

Because we are not familiar with heat transfered products such as heavy fuels can anyone help how to size the capacity of the heater needed to pump the product from tank to ship??

Tank: 11,46m diam./12m height (20m elevated from dock-sea level)
Discharge Pipeline: 8" Sch Std 250m long
Tracer line: 2" Sch Std
Product preheat time ~1 hour
Product flow rate : 150m3/h-200m3/h

 

[BigInch]

What is the associated temperature for your viscosity value? You also need to find out the lowest possible temperature for the fuel stored in the tank. The lowest possible temperature at which this operation will be conducted, get the specific heat capacity for the oil, get the mass or specific gravity or some indication of the mass or weight of oil in the tank, and the desired discharge temperature before you can take a stab at this. You should also have the viscosity at the low temperature, (not at 60ºF) The design wind velocity might also be helpful if you think it might give significant cooling effects.

Then you must design the heating system for the tank. What have you got hot around there to use for the heating medium, size the pump, the diameter and lengths of heating elements, heat circulation pumping system, find the pressure and flowrate required in the heating pipes.

Obviously we can't do that kind of work in these little boxes provided on this website, so get all that info together and then I suggest you try to find an engineer that can do a tank and pipeline heated delivery system design for you.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[MortenA]

suocsiv:

This site is generally for tips and help - not for "free consultancy service". You will get excellent help here - but you will need a good understanding of the field that you are asking question in.

How will you document the deisgn that you may receive from here?

My advice: If this knowledge does not exists within your company seek "professional help".

Best regards

Morten

 

[suocsiv]

Thank you for your advice!!
Parameters such as BigInch mentioned above help to get a litle bit more into heating details.

I am not looking for free consultancy service.I am just trying to clear some things out, such as the fact that my engineer is suggesting a 2.000.000kcal/h heater calculating the heat needed for a flow rate of 150m3/h ,but what about for example the heat needed to preheat the product in the tank? Isn't it another factor that I will have to add up to heaters'capacity?

Thanks again for your time.

 

[BigInch]

I thought that's what you wanted. It seemed the pipeline was being heated, but somebody forgot about the tank contents. That's why I asked about data values needed for the tank contents. No point heating the pipeline if you can't move the fuel oil out of the tank.

But neither is there point to heating the tank, if the pipeline remains plugged with cold product. Both must be heated to flow temperature.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[quark]

The specific heat of bunker oil is 0.23 kcal/kg ⁰C and flash point is about 60⁰C. Density is 985 kg/m³.

As the pour point is much below this value, you can go upto 40⁰C for the tank contents. We used to maintain 40⁰C in the tank and 60⁰C for transfer piping (for transfer from main sotrage to day storage of boiler).

The tank contents will be 3.142 x 11.46 x 11.46 x 12/4 = 1238 m³.

If you have 1 hr preheating time and considering 20⁰C initial temperature (or consider worst case), the heat input should be 1238 m³x985 kg/m³ x 0.23 kcal/kg ⁰C x 20⁰C/1 hr = 5609378 kcal/hr. (Note: You can reduce this by increasing the heating time.)

For transferring at 150m³/hr, you require
150m³/hr x 985 kg/m³x0.23kcal/kg ⁰C x 20⁰C = 679650 kcal/hr.

Then you have tank heat loss and also heat required to raise tank material. The link below gives you some methods to estimate tank heat losses.

http://www.chromalox.com/technical/pdf/en/heat-req.pdf

It is also worth reading Predict Storage Tank Heat Transfer Precisely by Jimmy Kumana et al appeared in Chemical Engineering March, 1982 issue.

 

[suocsiv]

Thanks a lot everyone!!!

I thing using the formula Q=m*c*dt as quark has mentioned above gives me a clearer view...

You need 40oC in the tank and 60oC for transfer piping for what exactly product?
Ours is RMG 380(ISO 8217) whith a visc of 380cSt/50oC-pour point 30oC or RME 180 180cSt/50oC-pour point 30oC (ISO 8217/2005).Are these products pumpable at 30oC??

In any case thank you.
I have some more reading to do..,coming back later on!

 

[25362]

To quark, what is the source of the bunker fuel heat capacity ? I have the feeling it would be about twice the quoted value.

 

[BigInch]

should be somewhere around 0.50 Btu/lb-F x 0.252 kcal/Btu x 2.2 Lbs/Kg = 0.28 kcal/Kg, although having SG would help zero it in.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[25362]

BigInch,

Btu/(lb[×]^oF) = Kcal/(kg[×]^oC)​

You apparently forgot to convert deg F to deg C.

 

[BigInch]

Bien hecho! Yes I did forget. I guess that's why I left out the ºC. Ugh! Forced me to get Katmar's unit converter running. How about that, 0.5 Btu/Lb-F appx = 0.5 kcal/kg-C. I always converted to kJ/Kg-K, hence before I never noticed this appximation.

I'm with you then. The heat calculated above needs to be at least doubled.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[25362]

Yo pienso que no es una aproximaci[ó]n sino una identidad.

 

[BigInch]

Tiene reason. Es cierto que no es por nada.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[quark]

hmmm... let us remember some forum etiquette (ofcourse, this is applicable to me as well:-().

1. The language spoken should be common.
2. When challenging a previously given data, it is the challenger that has to show references.
3. When in doubt google it.
4. All the above are not applicable if I am kidding

You are absolutely right that the specific heat is about 0.5kcal/kg ⁰C. Surprisingly, I did have the correct value but I missed it.

Thanks a lot for the correction.

Suocsiv,

The fluid I was speaking about is called as furnace oil here (or bunker C or No. 6 oil, else where, with 380cst @50C)

If the pour point is 30⁰C you can just pour at that temperature. Further, it is better to reduce viscosity before pumping for longer life of the pump. So, you require higher temperatures to pump it. I never checked what the viscosity was at 60⁰C. I faced problems below 60⁰C though the ambient temperatures here are generally high.

After doubling the value in my calculation, note that this is the calculation for initial start up. Once the temperature is reached, you have to just maintain it. The link I provided is an excellent tool to calculate the heat loss from tank and piping as well.

Good luck,

 

[suocsiv]

Quark I can't find "Predict Storage Tank Heat Transfer Precisely by Jimmy Kumana et al appeared in Chemical Engineering March, 1982 issue", is there a link to download or buy this article?

Thanks again for your helping knowlege!

 

[25362]

Quark, referring to your points:

a. I indeed childishly misbehaved for having used Spanish in my message to BigInch. It happens that I sometimes yearn to go back to mother-tongue when I see the correspondent speaks the language.
My last post translates into: I believe it's not an approximation but an identity.

b. Most liquid hydrocarbon fuels have specific heats of 0.45-0.50 kcal/(kg.^oC) or thereabouts at transferring temperatures.

One formula for Cp, in kJ/(kg.^oC), would be:

Cp = (1.7 + 0.0034 t)[÷] d^0.5​

where t = temperature in ^oC and d = density of oil at 20^oC in kg/L.

Their thermal conductivities are about 0.125 W/(m^oC).

c. No comment.

d. Even if/when joking you're still right in your complaint.

Suocsiv,

Some notes:

[•] A knowledge of the viscosity-temperature relationship is needed for the determination of the heating required for tranfer purposes, as well as the temperature range for satisfactory burning at the injector nozzle or burner.

[•] As long as the fuel is liquid and flowing (in some cases asphalt is considered an effective pour point depressant) you may not need to heat the whole tank contents to pumping temperature if you install properly-designed suction heater + pump system.

[•] A minimum of 80^oC is sometimes specified to take account of possible non-Newtonian behaviour of some heavy residual fuels.

Visit, among others,:

http://www.rmarmstrong.com/products5.htm

http://www.kochheattransfer.com/cp/UserFiles/articles/tank_bro.pdf

http://www.fueloilpump.com/08-heavyoil.html

 

[quark]

Thanks for the equation. I knew you have something up your sleeve. Get the star.