Fouling thermal conductivity 1

[MortenA]

Google "fouling thermal conductivity" and you get lots of hits but i think i stared myself blank because all these references (and my old text books) allways refer to the overall value (BTU/FT² h F or a similar SI unit system value) - NOT the conductivity of the substance e.g. FT h F/BTU and they never refer to the thickness of the layer so i cant back calculate. Most actually refer to the same table from Kern,. I used tp have a copy but lost it in my last job swap.

Could anybody help me here? I need a typical value for a HC (multiphase crude) residue and NOT the typical resistance contribution (or the thickness of the layer used by e.g. Kern.

Best regrads

Morten

 

[LCeballos]

Normally, these values are tabuled, in fact you can find them in "Heat Transfer" written for A.F Mills. I have taken some values for fouling resistance for reference:

Fluid: Fouling resistance (Rf) [W/m2 K]^-1
Fuel oil 0.005
Oil for Electrical transformers 0.001
Vegetable oil 0.003
Light diesel 0.002
Heavy diesel 0.003
Asphalt 0.005
Gasoline 0.001
Kerosone 0.001
Caustic solutions 0.002
Coolant liquids 0.001
Hydraulic fluid 0.001
Casted salts 0.0005
Escape gas from engines 0.01
Vapor (without oil) 0.0005
Vapor (with oil) 0.001
Coolant vapors (with oil) 0.002
Compressed air 0.002
Acid gas 0.001
Solvent vapors 0.001
Sea water 0.0005-0.001
Salted water 0.001-0.003
Treated cooling tower water 0.001-0.002
Non treated cooling tower water 0.002-0.005
River water 0.001-0.004
Condensated water from close cycle 0.0005
Treated water for boilers feed 0.0005-0.001

Regards,

Luis C.

 

[MortenA]

Thanks, but as i said - its easy to find the overall thermal resistance - what im looking for is the thermal conductivity (W/mC in SI) (or the thickness of the layer that these numbers were derived from).

But thanks for the effort anyway.

Best regards

Morten

 

[25362]

Fouling factors as listed by Luis Ceballos are given in m[sup]2[/sup]K/W as the inverse of heat transfer coefficients,
There is no use for fouling thermal conductivities since this would involve knowing fouling thicknesses. BTW, units of thermal conductivity are the inverse to those quoted.

 

[25362]

Morten A, I must say I haven't seen your last posting. I meant "the inverse" of those units in your opening message.

 

[25362]

BTW, plenty of threads dealt with fouling factors. I found thread391-251669 highly educating.

 

[25362]

Fouling factors are determined experimentally by measuring the values of the overall heat transfer coefficients under "clean" and "dirty" conditions:

FF = 1/U[sub]dirty[/sub] – 1/U[sub]clean[/sub]​

 

[MortenA]

@25362: I NEVER asked for fouling factors - what i need are thermal conductivity of varoius substances found on e.g. heat exchangers (or the thickness of the layer behind those numbers refer to above IF they exist. Why? I didnt say that explicitly i know didt think it would matter but since it does: I need it because the HX design software called EDR (by Aspentech) wants the thermal conductivity and the thickness of the layer. OK so i could just say: My layer is 2 mm thick, and back calculate the equvalent conductivity. But if i wanted to try another FF r another layer thickness - then i would need to do it again!

Why would i want to do such a thing (OK maybe im going overboard here but i havnt had my first cup of coddee yet so... ): I have a HX with a reduced performance. I also experience a much higher dP on the tube side than expected - so i wanted to do a little simulation work to see if there was much to gain by opening the HX and clean it on the tube side or if some cleaning agent on the shell side would be sufficient.

Best regards

Morten

 

[Latexman]

Can you add some description to "HC (multiphase crude) residue" for us non-Petroleum types? Kern gives TC of HC liquids with API and temperature. Do you have that data?

Good luck,
Latexman

 

[Latexman]

Kern gives TC of HC liquids with API and temperature. Do you have that data?

Good luck,
Latexman

 

[Latexman]

click. Click. CLICK Damn it!

Good luck,
Latexman

 

[willard3]

Marks handbook for Mech Eng gives thermal conductivities of liquids and gasses, but I'm not going to type it in, it's too big.

 

[MortenA]

@willard3 thanks for the refercne. I will see if i get get hold of one.

@latexman: Hmmmm i have clicked and clicked untill my fingers bled and all i come by are those FF. Wrt "HC (multiphase crude) residue" the HX is an inlet heater that heats product from a marginal field subsea tie-back to a processing platform. The crude cools in transit and we now have some problems with wax granulate that ends up in the water phase and makes produced water cleaning difficult. By heating the oil/water/gas we can make the wax liquid and then it dissolves in the oil phase. Ironically its the addition of wax dispersants that causes the problem - but that nescessary in order to awoid wax deposition.

You write "TC" is that the heat capacity or? im not familiar with the abbreviation sorry. Also, i dont have a copy of Kern currently. I might consider getting one again.

 

[Latexman]

Thermal Conductivity

Good luck,
Latexman

 

[25362]

Morten A, from your posting of september 24, it seems to me you assume that thermal resistances, expressed as fouling factors, are the result of measuring conductivities and thicknesses of fouling deposits, as could possibly be done with calcium hardness deposits inside heat exchanger tubes.

To my grasping fouling resistances were, otherwise, obtained from experimental measurements on the overall HTC's [U's] under varying thermo-physical conditions. It seems also logical since deposits are far from being of uniform thickness and sometimes show to be of a porous character.

Curiously enough, in a few cases, the roughness and restrictions to flow of the fouling layer leads to negative resistances meaning an improvement of HT due to fouling deposits. It is assumed that an increase in thermal performance would occur for small-diameter tubes in which the film coefficient is low and the deposit thermal conductivity is relatively high.

FWIW, the thermal conductivity of solid paraffin waxes is about 0.25 W/(m.K). Good luck.

 

[MortenA]

25362,

Thanks i guess that assuming its a parafin is a little difficult since the hot side is 130-119ºC but i will see how it fits in.Wrt tio getting from FF to a thermal conductivity: I agree that the experimental values are good because they are average - and that great variatiuons may be present. Its just the stupid software needs that inout. I think i will settle for back calculating as appropriate.

Best regards
Morten

 

[Christine74]

Table 4 of HTRI Report F-4 "Design Fouling Resistances - Recommended Good Practice" contains thermal conductivities of several individual fouling components.

 

[MortenA]

@Christine74,

Thanks, they appear to be properitaire reports, and if you are not a costumer you dont have access.

Best regards

Morten

 

[vpl]

Morten
Hopefully this will be of some help. It is from Kreith, Principles of Heat Transfer, 3rd Edition (which is falling apart, but I hate to get rid of for just this reason.)

Patricia Lougheed

******

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.

 

[MortenA]

@Patricia,

Thanks really appreciate it

Best regards

Morten