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crossbow (Mechanical) (OP)
5 Sep 07 20:45
I am currently checking the steam requirement for an existing suction heater, however I am having trouble finding the thermal properties of the oil ie specific heat capacity, heat transfer coefficient and maximum heat flux at the various temperatures.  Does any one know where I can get this information.
Helpful Member!(2)  BigInch (Petroleum)
6 Sep 07 5:47
What oil?  Those properties can usually be related to the specific density or specific gravity.  Do you have the SG or API gravity?

crossbow (Mechanical) (OP)
6 Sep 07 15:12
The oil is a 180 cSt No.6 Bunker oil, reference ISO 8217.  The data sheet has some very broard temperatures and corresponding viscosities which is not of great help to me.  The operating temperture range is 20 to 50 degrees celcius. I was hoping to locate data similar to that which I have for a BP Transcal N thermal oil which shows a good set of graphs relating specific heat, thermal conductivity, vapour pressure, viscosity and heat transfer coefficients to temperature.
BigInch (Petroleum)
6 Sep 07 15:45
copy of data I have for No. 6 Fuel Oil

Appearance: Black
Physical State: Viscous liquid
Odor: Heavy petroleum; asphalt-like
pH: Not applicable
Vapor Pressure (mm Hg): Negligible @ 100°F
Vapor Density (air=1): >1
Boiling Point/Range: >350°F / >177°C
Freezing/Melting Point: No Data
Solubility in Water: Negligible
Specific Gravity: 0.991
Evaporation Rate (nBuAc=1): <1
Viscosity: 205 SUS @ 122°F (50°C)
Bulk Density: 8.25 lbs/gal
Flash Point: 150°F / 66°C minimum (PMCC)
LEL: 0.5 / UEL: 7.0 Flammable/Explosive Limits (%):

Specific Heat (based on 0.991 SG) should be 0.79 Btu/h/ft2/(Fº in)
Caragoe Equation gives Adiabatic Bulk modulus of 323000 psi

0707 (Petroleum)
7 Sep 07 13:11
No.6 Fuel oil will depend on crude oil origin, so it will be very difficult to have a typical composition. A no.6 fuel oil from a sweet crude will be very different from a sour crude origin.

“No. 6 fuel oil, sometimes called residual, Bunker C, vacuum bottoms, or reduced crude is produced by many methods, but basically, it is the residue left after most of the light volatile products have been distilled from the crude. It is a very heavy oil, with a viscosity ranging from 900 to 9000 Saybolt Universal Secondary (SUS) at 100°F. Thus it can be used only in installations with heated storage tanks and with a recirculating piping return back to the tank in order to circulate hot oil at the burner front for correct atomisation. No. 6 oil essentially is a refinery by-product.

Due to the demand of low sulphur content and low fuel bound nitrogen fuel oil to meet the stringent limits dictated by the environmental protection agency regulations, light distillates with characteristics as having low sulphur content and low fuel bound nitrogen are blended with high sulphur and high fuel bound nitrogen residue to produce an improved fuel. However, blending light distillate oils with heavy #6 influence other properties of oil. For example, API gravity, heating value per gallon of oil; viscosity, and the ash content as well as the emissions.”

crossbow (Mechanical) (OP)
9 Sep 07 3:14
Thanks BigInch could you just confirm that this is for  Specific Heat (based on 0.991 SG) should be 0.79 Btu/h/ft2/(Fº in)or should this read heat transfer coefficient, just checking my unit conversion to either W/m2.K or kJ/kg.K.
Helpful Member!  25362 (Chemical)
9 Sep 07 7:00

The units given by BigInch apparently correspond to thermal conductivity, not HTC.
To convert to W/(m.K) multiply Btu/[] by 0.1442.  

BigInch (Petroleum)
9 Sep 07 15:09
Thank you 25362 (again)

25362 is right, I gave you the heat conductivity. Appologies.

Specific Heat is = 0.46 Btu/lbm-F

crossbow (Mechanical) (OP)
9 Sep 07 15:50
Thank you all for your help.
25362 (Chemical)
10 Sep 07 0:11

Please note that the Pr number = Cp.μ/κ changes a lot with temperature. An engine oil, for example, would change its Pr from, say, 10,000 at 20oC to about 100 at 150oC mainly due to the viscosity factor μ.
crossbow (Mechanical) (OP)
10 Sep 07 1:18
Thanks 25362 I had seen that for the BP Transcal N, but obviously this detailed data is not available for 180 cSt HFO.  From BigInch's data I get the viscosity at 50C of 205 SUS does any one have data that would give me the viscosity fron say 10 to 100 degree C. Would I assume that the Prandtl number for HFO is not readily available and is calculated depending on the producer and the fact that it varies significantly from source to source as pointed out by 0707.
BigInch (Petroleum)
10 Sep 07 3:29
The viscosity is best predicted with two actual values at different temperatures and heavy fuels can vary considerably, but lacking that you might be forced to use the typicals from the cSt/temperature line for various hydrocarbons.  

See also, the theory of calculation of various properties,

25362 (Chemical)
10 Sep 07 3:32

For a ballpark estimate, a fuel having 180 cSt at 50oC would have ~300 cSt at 40oC and ~20 cSt at 100oC.

If you have a visc./temp. chart, and assuming you are far away from the fuel's pour point, an extrapolation to 20oC would give about 1500 cSt.
25362 (Chemical)
10 Sep 07 4:21

Evidently, BigInch's message and mine were almost simultaneous.
crossbow (Mechanical) (OP)
10 Sep 07 4:27
Like they say great minds think alike.

Thank you for your help.
jmw (Industrial)
10 Sep 07 7:01
For viscosity data, go to and download the ASTM spreadsheet. This has several different fuel oils preloaded and shows the viscosities at various temperatures based on the ASTM D341 calculation for viscosity above 2xst. It also has the Injection temperature or EVT calculation... just enter the viscosity you want and it will return the temperature that corresponds.


Sharper80 (Mechanical)
8 Oct 07 5:38
In your post on 6th Sep you mention the Caragoe equation for calculating bulk modulus. I googled it but it only returned this website.

Can you give me some more info on this?


BigInch (Petroleum)
8 Oct 07 6:50
Here's the equation I use for estimating HC bulk modulii, (Excel format)

Bulk_Modulus_PSI = 100000*EXP(1.9947-0.00013427*TF-0.79392/SG^2-0.002326*TF/SG^2)

TF = Temperature ºF = Temperature of SG measurement (usually 60ºF)

SG = Specific Gravity

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