experimental study on wax-deposition …...bruno (2006) reported results on the south pelto crude...

PB Oil and Gas Facilities • August 2013 August 2013 • Oil and Gas Facilities 61

SummaryCrude oil, having a paraffin nature, has been studied extensively in the small-scale flow loop at Tulsa University Paraffin Deposi-tion Projects (TUPDP). The effects of turbulence/shear and thermal driving force on wax-deposition characteristics were experimen-tally studied using a waxy crude oil from the Gulf of Mexico. The test matrix consisted of a total of 15 experiments, which included 12 short-term tests and three long-term tests. The tests were con-ducted under different operating conditions with a wide range of Reynolds numbers from 3,700 to 20,500. The shear stress ranged from 5.4 to 53.9 Pa.

It was observed that paraffin deposition is highly dependent on the thermal effective driving force, which is the temperature dif-ference between oil bulk and initial inner pipe wall, and also on turbulence effects. The deposit thickness obtained using both the pressure-drop method and a direct measurement was found to de-crease with increasing shear stress and decreasing thermal driving force. The wax content showed a gradual increase with an increase in flow rate. For the short-term tests, the deposit mass with no en-trained oil seemed to increase and then decrease with an increase in initial shear stress and decrease in effective thermal driving force, whereas the total deposit mass was found to decrease with an increase in initial shear stress or decrease in effective thermal driving force.

IntroductionWhen crude oil flows through the subsea and production pipelines, the oil temperature drops because of the colder surroundings. It has been observed through experiments and postulated in literature that when the bulk temperature of the crude oil in pipes is higher than the wall temperature, there exists a dissolved wax concentra-tion gradient between the bulk oil and the pipe wall. The n-paraffin components are considered to be mainly responsible for wax depo-sition (Benallal et al. 2008). When the pipe-wall temperature goes below the wax appearance temperature (WAT) of the oil, the liquid wax diffuses toward the wall. The liquid wax diffused toward the pipe wall crystallizes on the wall surface or at the interface between the bulk and deposit. The wax deposit may eventually block the pipes. Hence, it is imperative to accurately predict wax deposition under different operating conditions. The main problems associated with wax deposition are the increased pressure drop in the pipeline, reduced productivity and the risk of getting a pig stuck during reg-ular maintenance operations.

The current paraffin deposition models can predict wax- deposition characteristics with high confidence under zero or low-shear-rate

conditions while they can grossly overpredict and underpredict par-affin deposition under turbulent flow or high-shear conditions. Un-derstanding of the physics behind paraffin deposition in single phase can help accurately model the behavior aiding in the prediction of paraffin deposition and in deciding the pigging frequency.

Matlach and Newberry (1983) reported that increasing the shear rate increases the hardness of the deposit as well as the median carbon number of the deposit. Weingarten and Euchner (1988) ob-served sloughing at high shear rates in a 6.4-mm (0.25-in.) -di-ameter flow loop. They also reported that the onset of sloughing was not related to the transition from laminar to turbulent flow. Hsu et al. (1994) stated that shear is not a critical factor affecting wax deposition under laminar flow; however, it must not be ne-glected under turbulent flow conditions. Creek and Hobson (1996) reported periodic sloughing in a flow loop 3.2 mm (0.13 in.) in di-ameter. It was also found that shear rate not only affects the depo-sition rate but also the nature of the paraffin deposits. Solaimany Nazar (2001) conducted an experimental and mathematical mod-eling study of wax deposition. He found that an increase in the flow rate leads to an increase in the amount of mass deposited up to a specific flow rate, namely the critical flow rate. Beyond this critical value, a further increase in flow rate causes a decrease of deposit mass. The interpretation was that the deposition mass at high flow rates decreases sharply in turbulent flow because of a sloughing ef-fect. The critical Reynolds number found in his study was 2,700. Hernandez (2002) did not observe any significant reduction in de-posit thickness at different flow rates under isothermal conditions. However, no definitive conclusions were drawn because of the un-certainties of the methods used to estimate deposit thickness and wax content. Jennings and Weispfennig (2005) studied the effects of shear and temperature on wax-deposition characteristics. They observed a reduction in the amount of entrained crude oil and a decrease in total deposition with increasing shear. They found the amount of wax to be relatively constant for a particular range of variation in shear. The study also revealed an expected increase in total deposition when the differential temperature was increased.

After analyzing the previous data from TUPDP, additional tests were conducted with a crude oil (south Pelto crude oil) under single-phase high-shear-flow conditions. The experimental results were used to carry out further data analysis. In addition, long-term turbulent single-phase experiments with low heat flux were also conducted and analyzed.

Fluid Characterization Bruno (2006) reported results on the south Pelto crude oil with an API gravity of 35° and a wax appearance temperature of approxi-mately 124°F measured by fourier transform infrared spectrometry at 5,000 psig. The wax content is approximately 6.7% by weight of C17 to C80 fractions of n-paraffin components. Further DSC analysis on the oil samples collected during various experiments revealed a wax appearance temperature of approximately 118°F for south Pelto oil.

Experimental Study on Wax-Deposition Characteristics of a Waxy Crude Oil Under Single-Phase Turbulent-Flow Conditions

Priyank Dwivedi, Cem Sarica, and Wei Shang, University of Tulsa

Copyright © 2013 Society of Petroleum Engineers

This paper (SPE 163076) was revised for publication from paper OTC 22953, first presented at the Offshore Technology Conference, Houston, Texas, USA, 30 April–5 May 2012. Original manuscript received for review 24 January 2012. Revised manuscript received for review 23 July 2012. Paper peer approved 30 August 2012.

62 Oil and Gas Facilities • August 2013 August 2013 • Oil and Gas Facilities 63

The viscosity of south Pelto crude oil was measured by sev-eral companies (Marathon, Shell, and Conoco). Creek and Hobson (1998) combined the data sets from these companies and developed a correlation for the viscosity of the oil, which is given by

2

ln 14.023469 11.906456

1000 1000 2.533129 ,

o

o oT T

µ = −

× +

..............................................(1)

Where To is the oil temperature (°K) and mo is the viscosity (cp).An Anton Parr high-shear rheometer was used to perform vis-

cosity measurements with respect to temperature for south Pelto crude oil. The results of the test are presented in Table 1. Fig. 1 summarizes the viscosity profile of the south Pelto crude oil. The data from the measurements differ from the results obtained from Bruno (2006).

Experimental Facility DescriptionThe experimental facility consists of two oil systems of different capacity, a cooling system, three test sections with different pipe diameters, a data acquisition system, and a control system.

Oil System. Fig. 2 shows a schematic of the oil systems. It has two different oil-circulation systems with common test sections and a common oil heater. The two systems are different in terms of quan-tity of oil that can be stored and the circulation pump types and capacities. The small oil system has a storage tank with a capacity of 3 bbl, which can be operated at atmospheric pressure or with a 10- to 20-psig nitrogen blanket on top. A variable speed two-stage mixer keeps the temperature in the tank uniform and prevents the wax from depositing on the tank walls. Fluids are circulated using a sliding vane pump, which has a maximum capacity of 1,000 B/D.

A new oil system containing a new high-capacity pump and a large oil tank was envisaged to study wax deposition under high Reynolds number and high shear stress. This large oil system con-

sists of a storage tank of 15-bbl capacity and a variable-speed electric-motor-driven progressive cavity pump to provide test flow rates up to 3,500 B/D. The new larger storage tank could serve to run the long-term tests to avoid any concerns of depleting the test fluid during the experiment. These modifications have allowed run-ning wax deposition experiments for 3- to 4-week periods under high turbulence regime (high Reynolds number and shear stress).

The facility uses a 15-KW electric circulation heater to main-tain the set bulk oil temperature. The heater was designed to output a maximum heat flux of 10–12 W/in2 to avoid high skin tempera-tures and cracking of the oil. This heater is common to both the oil systems.

Test Sections. The test sections consist of three schedule-40 carbon steel pipes with nominal diameters of 0.5, 1.0, and 1.5 in. All the three sections are in a pipe-in-pipe configuration, wherein a gly-col/water mixture flows in the annulus. The temperature difference between the bulk oil and glycol/water mixture acts as the driving force for wax deposition in the test section.

Each test section is 8 ft in length and is insulated from the am-bient. A 7-ft-long hydraulic section allows development of the flow and eliminates entrance effects before reaching the jacketed sec-tion. Each test section is equipped with three different ports/open-ings. These openings can be used to collect wax-deposit samples at a specific time during an experiment and at the end of the test. These ports can also be used to measure deposit thickness by a di-rect method that involves boroscope. The test sections share inlet and outlet temperature transducers to monitor the oil temperatures. Each section has a differential pressure transducer to monitor pres-sure drop of the fluid across the section. Fig. 3 shows a schematic of the test sections in the facility.

Glycol System. Two separate glycol-circulation systems are part of the facility. One loop is referred to as the cold glycol system, in which a pump circulates 50% glycol water solution from a storage tank through a shell-and-tube heat exchanger. This fluid enters a 10-ton chiller to cool the glycol, which flows in the test-section an-nulus. The other loop circulates the cooled glycol through the test section. This loop, like the cold-glycol loop, constitutes a pump, a storage tank, and a mass flowmeter.

A control valve can be operated either automatically through data-acquisition systems or manually controls the desired glycol/water temperature by controlling the amount of cold glycol to be mixed in the heat exchanger with the glycol coming back from the section. The glycol flow rate is regulated by a bypass valve, which is controlled using data coming from the mass flowmeter.

Analysis of Data From Past StudiesThe data analyses were performed on the wax-deposition exper-imental results obtained by previous researchers at TUPDP cor-responding to three different crude oils. The objective of this analysis was to investigate the trend of deposit thickness and wax content with shear stress and Reynolds number. In the previous single-phase experimental studies conducted at TUPDP, three dif-ferent crude oils (south Pelto oil, Garden Banks condensate, and Cote Blanche Island crude oil) were tested using three different

Fig. 1—Viscosity Profiles for south Pelto oil.

TABLE 1—VISCOSITY MEASUREMENTS FOR SOUTH PELTO CRUDE OIL

Temp (°K)

Temp (°F)

Creek and Hobson (1998) (cp)

Anton Parr Viscometer Results (cp)

319.26 115 4.86 5.83 313.71 105 6.11 6.9 308.15 95 7.86 8.86 302.59 85 10.39 12 297.04 75 14.15 15.10

0

10

20

30

40

50

60

40 60 80 100 120 140

Dyn

amic

Vis

cosi

ty (c

p)

Temperature (°F)

Creek's CorrelationASTM-BrunoAdjusted-BrunoAnton Parr Viscometer Results


Fig. 2—Oil system schematic.

Fig. 3—Schematic of the test sections.

From Test SectionDP Lines

Vent

P11

PT1

TT1DPT1

LS1

PRV1

V12

V3V11

V5V4

V29

V2V1

V13

V10

V9

V8

V7

V5

Transfer

TransferTransfer/Drain

Transfer/Drain

Transfer/Drain

MM2

MM1, MD1

TESTSECTIONS

A

B

TT6 2 StageMixer

Large Oil Tank15 BBL

PT Large TankTT Large Tank

Hose Connection

ProgressiveCavityPump

SlidingVanePump

PT2

Small Oil Tank3 BBL

VariableSpeed Mixer

OIL SYSTEMRevised: 10/2010

Circ

ulat

ion

Hea

ter

G13

To oil return line (TT6)

TT4

8-ft Test Section—3 in. jacket



Nitrogen

Pig Receiver Pig Launcher

B A

D

C

DPT2

DPT3

DPT4

D5

D4G4

G5G7

G6

D1

G3

D3

D2 PT4

TT2

TT5

TT3

PT3

N43

N34 N33 N32N31

N41N42

N22N21

N23N24

N44 V22

V20V21

V18

V16

V17

V19

V15V14

V27

V29

V26

V24

V23

V25

V28 ½ in. ½ in.

½ in.


test facilities for various ∆T (Toil–Tglycol) (Dwivedi 2010). The test data were sorted on the basis of the reliability of obtained results during an experimental run. The test data selected from the pre-vious studies fall under turbulent flow regime except for the Cote Blanche Island crude oil.

Deposit Thickness Vs. Shear Stress. Fig. 4 plots the summary of deposit thickness (pressure-drop method) vs. shear stress for south Pelto oil from the previous experimental data at TUPDP. The differences between bulk oil and the glycol/water solution tem-peratures, ∆Ts, considered in the analysis were 30, 45, and 15ºF. For analysis and comparison, all the experiments considered are 24 hours in duration. Overall, there were three different methods used to measure the deposit thickness in previous experiments con-ducted by previous researchers at TUPDP [i.e., the pressure-drop method, the spool piece LD-LD method, and the online LD-LD method (Hernandez 2002)]. The trend of deposit thickness vs. the initial wall shear stress for ΔT=30°F was observed to be continu-ously decreasing, although, given the uncertainty of the thickness calculation from the pressure-drop measurement, no specific trend was observed at a lower ΔT=15°F. For ΔT=45°F experimental data points, deposit thickness was found to be decreasing at high shear stress values while increasing at low shear stresses. This somewhat agrees with Solaimany Nazar’s (2001) observations.

Fig. 5 is a graph for the shear stress and deposit thickness as measured by the spool-piece LD-LD method. At ΔT=15°F, the spool-piece measurement does not show a significant change in de-

posit thickness with shear-stress data, which is in agreement with the pressure-drop data analysis. At ΔT=45°F, the measured values are widely scattered, although there is a hint of thickness decrease when increasing shear stress. The measurement error can be attrib-uted to the uncertainty of the measurement technique, and hence data are not very reliable. Fig. 6 shows the trend of deposit thick-ness with shear stress when the online LD-LD method is used. There is a clear decreasing trend with an increase in shear stress. The online LD-LD method is supposedly more accurate than the spool-piece LD-LD method.

In summary, the deposit thickness for south Pelto oil shows a decreasing trend with an increase in shear stress for ∆T=30ºF and 45ºF when thickness was calculated from pressure-drop measure-ments, whereas no trend was observed for deposit thickness at 15ºF for any thickness measuring method, although the three test facili-ties have different configurations. The deposit thickness from the online LD-LD method was also found to decrease with an increase in wall shear stress. The increase of wax content when increasing initial shear stress showed an aging effect.

Fig. 7 shows the graph of shear stress and deposit thick-ness (pressure-drop method) for the Garden Banks condensate at ΔT=30°F and ΔT=15°F, respectively. This condensate was pro-vided to TUPDP by Shell Oil Company. It has an API gravity of 42.1°, a WAT of 96°F, and wax content of 3.3%. Unlike the south Pelto oil case, the duration of all the experiments considered was 24 hours. The effective ∆T considered for data analysis was 30ºF and 15ºF. It showed a clear reduction in wax deposition with an increase

Dep

osi

t Th

ickn

ess

(mm

)

Shear Stress (Pa)

∆T=15°F ∆T=30°F ∆T=45°F

0 10 20 30 40 50 60 70 80 90 100

2

1.8

1.6

1.4

1.2

1

0.8

0.6

0.4

0.2

0

Dep

osi

t Th

ickn

ess

(mm

)

Shear Stress (Pa)

∆T=15°F ∆T=45°F

0 10 20 30 40 50 60 70 80 90 100

2

1.8

1.6

1.4

1.2

1

0.8

0.6

0.4

0.2

0

Fig. 6—Deposit thickness (online LD-LD method) vs. shear stress for south Pelto oil.

Fig. 4—Summary: Deposit thickness (pressure-drop method) vs. shear stress for south Pelto oil.

Fig. 7—Deposit thickness (pressure-drop method) vs. shear stress for Garden Banks condensate.

Fig. 5—Summary: Deposit thickness (spool piece LD-LD meth-od) vs. shear stress for south Pelto oil.

Dep

osi

t Th

ickn

ess

(mm

)

Shear Stress (Pa)

(Online LD-LD), ∆T=45°F

0 5 10 20 25 3015 35 40

2

1.8

1.6

1.4

1.2

1

0.8

0.6

0.4

0.2

02 4 8 10 126 14 16

Dep

osi

t Th

ickn

ess

(mm

)

Shear Stress (Pa)

∆T=15°F ∆T=30°F

0

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0


in shear stress for ΔT=30°F, while no significant change was ob-served for ΔT=15°F, which is similar to the result observed for the south Pelto oil. Fig. 8 shows the graph of shear stress and deposit thickness using the spool-piece LD-LD method at ΔT=30°F and ΔT=15°F, respectively.

The Cote Blanche Island crude oil obtained from Chevron-Texaco has a considerably lower API gravity when compared with the south Pelto oil and the Garden Banks condensate. This oil has

an API gravity of 24° and a WAT of 105°F. The wax content is 6.3%. All tests for this oil were performed under laminar flow con-ditions. Fig. 9 shows a graph for the shear stress and deposit thick-ness before and after MEK wash using the spool piece.

Deposit Thickness Vs. Reynolds Number. Figs. 10 and 11 show the graph of deposit thickness from pressure-drop calculation vs. the Reynolds number for ΔT=30°F and ΔT=15°F, respectively.

Fig. 8—Deposit thickness (spool piece LD-LD) vs. shear stress for Garden Banks Condensate.

Fig. 9—Deposit thickness (spool piece LD-LD) vs. shear stress for CBI oil.

2 4 8 10 126 14 16

Dep

osi

t Th

ickn

ess

(mm

)

Shear Stress (Pa)

Spool Piece-1 (∆T=30°F) Spool Piece-2 (∆T=30°F)Spool Piece-2 (∆T=15°F)

0

1.4

1.2

1

0.8

0.6

0.4

0.2

0

Spool Piece Before MEK Spool Piece After MEK

1 2 4 5 63 7 8

Dep

osi

t Th

ickn

ess

(mm

)

Shear Stress (Pa)0

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

Fig. 10—Deposit thickness (pressure-drop method) vs. Reyn-olds number for south Pelto oil (ΔT=30°F).

Fig. 12—Deposit thickness (pressure-drop method) vs. Reyn-olds number for south Pelto oil (T=45°F).

Fig. 11—Deposit thickness (pressure-drop method) vs. Reyn-olds number for south Pelto oil (ΔT=15°F).

Fig. 13—Deposit thickness (spool piece LD-LD) vs. Reynolds number for south Pelto oil.

1000 2000 4000 5000 60003000 7000 8000

Dep

osi

t Th

ickn

ess

(mm

)

Reynolds Number

∆T=30°F

0

2

1.8

1.6

1.4

12

1

0.8

0.6

0.4

0.2

02500 5000 10000 12500 150007500 175000

Dep

osi

t Th

ickn

ess

(mm

)

∆T=15°F

Reynolds Number

2

1.8

1.6

1.4

12

1

0.8

0.6

0.4

0.2

0

2500 5000 10000 12500 150007500 17500 20000 22500 25000 27500 300000

Dep

osi

t Th

ickn

ess

(mm

)

Reynolds Number

2

1.8

1.6

1.4

12

1

0.8

0.6

0.4

0.2

0

∆T=45°F

2500 5000 10000 12500 150007500 17500 200000

Dep

osi

t Th

ickn

ess

(mm

)

Reynolds Number

2

1.8

1.6

1.4

12

1

0.8

0.6

0.4

0.2

0

∆T=15°F ∆T=45°F


There is no clear trend observed in both figures, which implies that the Reynolds number may not be a parameter affecting wax depo-sition. Fig. 12 shows the graph of deposit thickness vs. Reynolds number at ΔT=45°F. The deposit thickness first increases and then decreases with the Reynolds number. Fig. 13 shows the trend in deposit thickness from the spool-piece LD-LD measurement with the Reynolds number. There is a slight decreasing trend for the de-posit thickness with the Reynolds number. Fig. 14 shows the graph of the online LD-LD thickness vs. the Reynolds number. It shows a clear decreasing trend in the deposit thickness when increasing the Reynolds number.

Data Analysis of Experimental ResultsThe data analysis of the single-phase wax-deposition data from the previous researchers provided an impetus for further study to estab-lish a test matrix to investigate the shear effects for a wide range of shear stress and Reynolds numbers. The south Pelto crude oil was used to investigate the effects of shear and the driving force—the temperature difference between the oil and glycol/water mixture—on wax deposition under single-phase flow conditions. In this study, a total of 15 experiments were conducted, which included 12 short-term tests and three long-term tests. Tables 2 and 3 sum-marize the test matrix for short- and long-term experiments for the south Pelto oil, respectively.

Shear Stress and Reynolds-Number Variation. The turbulent flow regime is characterized by high turbulence in a pipe, and two of the key parameters are shear stress and Reynolds number. As the deposit thickness builds up on the inner wall of a pipe, the ef-fective cross-sectional area available to flow reduces from the ini-tial cross-sectional area. When the flow conditions are set in an experiment, the flow system encounters certain wall shear stress depending upon the flow rate and viscosity of the oil. Because this study is intended to investigate wax deposition under single-phase turbulent-flow conditions, it is imperative to consider the variation in wall shear stress as the wax builds up in the pipe and to observe if this makes an impact during wax-deposition phenomena.

It was observed from the calculations that the variation of shear stress and Reynolds number is large for the low-oil flow-rate exper-iments, whereas the variation or percentage change in shear stress and Reynolds number decreases for high-flow-rate cases. Also, it is evident from the data that when an experiment is described to be run at a certain shear stress or Reynolds number, it could be re-ferred to as the initial shear stress or the initial Reynolds number.

Fig. 14—Deposit thickness (online LD-LD) vs. Reynolds number for south Pelto oil (T=45°F).

Dep

osi

t Th

ickn

ess

(mm

)

Reynolds Number

2

1.8

1.6

1.4

12

1

0.8

0.6

0.4

0.2

0

∆T=45°F

2500 5000 10000 12500 150007500 17500 20000 22500 25000 27500 300000

TABLE 2—TEST MATRIX FOR SOUTH PELTO OIL: SHORT-TERM EXPERIMENTS

Test Code

Oil Flow Rate (B/D)

Pipe Diameter

(in.)

Toil (°F)

Tglycol (°F)

∆T (Toil–Tglycol)

(°F)

Velocity (m/sec)

Shear Stress, τw

(Pa)

NRe

Wax-SP-10-15 340 1.049 105 75 30 1.14 5.5 3688 Wax-SP-10-17 426 1.049 105 75 30 1.43 8.2 4629 Wax-SP-10-18 500 1.049 105 75 30 1.68 10.9 5448 Wax-SP-10-10 680 1.049 105 75 30 2.24 18.1 7285 Wax-SP-10-09 740 1.049 105 75 30 2.47 21.5 8026 Wax-SP-10-11 885 1.049 105 75 30 2.93 29 9524 Wax-SP-10-03 1267 1.049 105 75 30 4.18 53.9 13575 Wax-SP-10-21 1296 1.049 105 75 30 4.28 56 13873 Wax-SP-10-05 1244 1.61 105 75 30 1.74 10.4 8647 Wax-SP-10-08 1675 1.61 105 75 30 2.36 17.8 11767 Wax-SP-10-13 1890 1.61 105 75 30 2.66 21.9 13233 Wax-SP-10-06 2950 1.61 105 75 30 4.12 47.2 20529

TABLE 3—TEST MATRIX FOR SOUTH PELTO OIL: LONG-TERM EXPERIMENTS

Test Code

Duration (days)

Oil Flow Rate (B/D)

Pipe Diameter

(in.)

Toil (°F)

∆T (Toil–Tglycol)

(°F)

Velocity (m/sec)

Shear Stress,

τw (Pa)

NRe

Wax-SP-10-L1 15 850 1.61 105 10 1.19 5.4 5940 Wax-SP-10-L2 5 350 1.049 105 10 1.15 5.68 3755 Wax-SP-10-L3 15 767 1.049 105 10 2.52 22.3 8215


Table 4 shows the shear-stress and Reynolds-number variation during the tests.

Deposit Thickness and Growth. Fig. 15 compares the deposition growth (from the pressure-drop method) with time in the order of increasing initial shear stress for the experiments run in 1.0-in. ID pipe. It was observed that with an increase in initial shear stress, the overall deposition rate declines to give forth less deposit thick-ness at the end of the test. A close look at the deposition growth for the experiments reveals that even though Tests 9, 10, and 11 had higher initial shear stress than Tests 15, 17, and 18, the initial deposition rates (up to 6 hours) were found to be higher for these three tests.

Fig. 16 plots the deposition growth with time for the experi-ments run in 1.5-in. ID pipe. It was observed that the deposi-tion rate decreases with increase in flow rates, with high initial shear stress.

Fig. 17 shows the deposit growth with time for the long-term (5 and 15 days) experiments conducted in 1.0-in. ID pipe. The tem-perature difference maintained between oil and the glycol/water

TABLE 4—SHEAR STRESS AND REYNOLDS-NUMBER VARIATION

Test Code

Oil Flow Rate (B/D)

Pipe Diameter (in.)

Shear Stress (pa)

Shear Stress Variation (%)

Reynolds Number

Reynolds Number Variation (%)

Wax-SP-10-15 340 1.049 5.5 22.6 3688 5.00 Wax-SP-10-17 426 1.049 8.2 21 4629 5.31 Wax-SP-10-18 500 1.049 10.9 22.2 5448 5.23 WAX-SP-10-10 680 1.049 18.1 16.5 7285 3.47 WAX-SP-10-09 740 1.049 21.5 11.9 8026 2.73 WAX-SP-10-11 885 1.049 29 10.9 9524 2.70 Wax-SP-09-03 1267 1.049 53.9 5.5 13575 1.30 Wax-SP-09-21 1296 1.049 56.0 4.4 13873 0.90

Wax-SP-09-05 1244 1.61 10.4 22.2 8647 5.70 Wax-SP-10-08 1675 1.61 17.8 11.7 11767 2.70 Wax-SP-10-13 1890 1.61 21.9 6.2 13233 1.50 Wax-SP-09-06 2950 1.61 47.2 4.2 20529 1.04

Wax-SP-10-L1 850 1.61 5.4 12.2 5940 2.9 Wax-SP-10-L2 350 1.049 5.7 5.2 3755 1.20 Wax-SP-10-L3 767 1.049 22.3 5.0 8215 1.07

Dep

osi

t Th

ickn

ess

(mm

)

Time (hours)

Test 15—Shear Stress (5.5 Pa)Test 10—Shear Stress (10.1 Pa)Test 3—Shear Stress (53.9 Pa)Test 17—Shear Stress (8.2 Pa)

Test 9—Shear Stress (21.5 Pa)Test 21—Shear Stress (56 Pa)Test 18—Shear Stress (10.9 Pa)Test 11—Shear Stress (29 Pa)

0 10 20 30 40 50 60

1

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

Test 5—Shear Stress (10.4 Pa)Test 13—Shear Stress (21.9 Pa)Test 8—Shear Stress (17.9 Pa)Test 6—Shear Stress (47.2 Pa)

Dep

osi

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ess

(mm

)

Time (hours)

0 10 20 30 40 50 60

1.2

1

0.8

0.6

0.4

0.2

0

Test L2—Shear Stress (5.68 Pa)Test L3—Shear Stress (22.3 Pa)

Dep

osi

t Th

ickn

ess

(mm

)

Time (days)0 2 4 86 10 12 14 16

0.5

0.45

0.4

0.35

0.3

0.25

0.2

0.15

0.1

0.05

0

Fig. 15—Deposition growth with time: 1.0-in. ID tests. Fig. 16—Deposition growth with time: 1.5-in. ID tests.

Fig. 17—Deposition growth with time: Long-term experi-ments—1.0-in. ID pipe.


mixture was 10°F. In the figure, a continuous growth in the wax deposit without reaching any plateau was observed. It also depicts a smaller deposition rate for the experiment conducted at higher initial shear stress.

Figs. 18 and 19 display the deposit thickness from four different methods: the pressure-drop method; physical measurement using a boroscope system; and two different simulation approaches, film mass transfer and equilibrium models at 24 and 48 hours, respec-tively. It was observed that the film mass transfer model highly overpredicted the deposit thickness, whereas the equilibrium model underpredicted the deposit thickness until a certain shear stress, and then overpredicted in high-turbulence flow conditions. Similar trends in deposit thickness were observed for the experiments in the 1.5-in. ID test section.

To investigate the effects of pipe diameter, dimensionless de-posit thickness δ/r was plotted against shear stress and Reynolds number in Figs. 20 and 21. It was observed that the dimension-

less deposit thickness decreases with an increase in shear stress and Reynolds number.

Wax Content. Differential scanning calorimeter (DSC) and gas chromatography (GC) were used for the wax-content measurement (Dwivedi 2010). Fig. 22 shows the trend of wax content at 24 hours using DSC and GC with shear stress. It was observed that there is an increase in the wax content, which results in harder deposits with increasing shear stress. Both the wax-content measurement methods yielded a decrease in wax content after a certain shear stress. Also, the wax content measured using DSC was found to be higher than that measured using GC. Fig. 23 shows the trend of wax content at 48 hours using DSC and GC with shear stress.

Effect of Interface Temperature and Shear Stress. The tempera-ture difference between the bulk oil and the glycol/water solution is the driving force for the wax deposition in the pipe. Although

Dep

osi

t Th

ickn

ess

(mm

)

Shear Stress (Pa)

Thickness (Pressure Drop)—24 hrsThickness (Equilibrium Model)Thickness (Boroscope)—24 hrsThickness (Film Mass Model)

0 10 20 30 40 50 60

1.6

1.2

0.8

0.4

0.0

Dep

osi

t Th

ickn

ess

(mm

)

Shear Stress (Pa)

Thickness (Pressure Drop)—48 hrsThickness (Equilibrium Model)Thickness (Boroscope)—48 hrsThickness (Film Mass Model)

0 10 20 30 40 50 60

2.5

2.0

1.5

1.0

0.5

0.0

Dim

ensi

on

less

Dep

osi

t Th

ickn

ess

(δ/r

)

Shear Stress (Pa)

Dimensionless Thickness (Pressure Drop)—24 hrsDimensionless Thickness (Pressure Drop)—48 hrs

0 10 20 30 40 50 60

0.03

0.025

0.02

0.015

0.01

0.005

0

Dim

ensi

on

less

Dep

osi

t Th

ickn

ess

(δ/r

)

Reynolds Number

Dimensionless Thickness (Pressure Drop)—24 hrsDimensionless Thickness (Pressure Drop)—48 hrs

0 5000 10000 15000 20000 25000

0.03

0.025

0.02

0.015

0.01

0.005

0

Fig. 18—Deposit thickness (24 hrs.) vs. shear stress: 1.0-in. ID pipe experiments.

Fig. 20—Dimensionless deposit thickness vs. shear stress (all short-term tests).

Fig. 19—Deposit thickness (48 hrs.) vs. shear stress: 1.0-in. ID pipe experiments.

Fig. 21—Dimensionless deposit thickness vs. NRe (all short-term tests).


the temperature difference set between the oil and glycol was 30°F for the short-term experiments and 10°F for the long-term experi-ments, it was found that the effective acting driving force for the wax buildup was not the same. The initial wall temperature and oil bulk temperature were the precursors to wax deposition in the test section. Because there is no provision in the pipe to monitor the wall temperature in the existing facility, a study was carried out to estimate the trend in various temperature profiles within the test section as the wax began to deposit on the wall surface. Fig. 24 shows the oil bulk temperature (105°F), the glycol/water mixture temperature (75°F), and the inner wall temperature of the pipe and the oil/wax interface temperature for the experiment Wax-SP-10-15 as the wax builds up in the pipe.

In a previous experimental study (Bruno 2006) at TUPDP, ther-mocouples were used to monitor wall temperature. Because of the paraffin-deposition characteristics, a layer of wax will coat on the tips of thermocouples and form an insulation layer as long as the fluid temperature drops its WAT. Because the thermocouples cannot give the representative wall surface temperature, it was cal-culated for different flow conditions. The following correlations have been used in calculating wall surface temperature with speci-fied parameters (e.g., k of the wax) in the heat-transfer analysis. The Nusselt number to determine inside heat-transfer coefficient for the pipe (Gnielinsky 1990) can be calculated using

0.66

0.5 0.66/ 2 (Re 1000) Pr (1 ( / ) )

N ,u1 12.7 ( / 2) (Pr 1)

i ldff

× − × × +=

+ × × − .......................(2)

where

2[1.58 ln(Re) 3.28] .f −= × − ...................................................(3)

The Reynolds number Re and Prandtl number Pr are based on inner pipe conditions. Also, the Nusselt number in annular ducts for tur-bulent flow (Gnielinski 2009) to find outside heat-transfer coeffi-cient is found by

0.66

0.66/ 8 Re Pr [1 ( / ) ]N ,u

12.7 (Pr 1) / 8fa dh L fa K

kl fa× × × + × ×=

+ × − × ......................(4)

where

900 0.631.07Re 1 10 Pr

kl = + −+ ×

....................................................(5)

* 21.8 log(Re 1.5)fa −= × − .......................................................(6)

2 2*

2

Re (1 ) ln (1 )Re

(1 ) ln

a a a

a a

× + × + − =− ×

......................................(7)

0.170.75fa a−= × .....................................................................(8)

2i ipd d δ= − ...........................................................................(9)

dh do di= − ..........................................................................(10)

oi

da d= ...............................................................................(11)

Interface temperature is then given by

bulk glycolinterface bulk

( ).o o

i i

d U T TT T

d h× × −

= −×

..........................(12)

Note that the thermal conductivity of wax is 0.15 W/m-K.Fig. 24 shows that the initial wall temperature and oil/wax inter-

face temperature start off at the same value, but as the wax deposits

Fig. 22—Wax content comparison at 24 hrs. vs. shear stress.

Fig. 24—Typical temperature behavior (Wax-SP-10-15).

Fig. 23—Wax content comparison at 48 hrs. vs. shear stress.

Wax

Co

nte

nt

(%)

Shear Stress (Pa)

Wax Content (DSC) at 24 hrsWax Content (GC) at 24 hrs

0 10 20 30 40 50 60

100

90

80

70

60

50

40

30

20

10

0

Wax

Co

nte

nt

(%)

Shear Stress (Pa)

Wax Content (DSC) at 48 hrsWax Content (GC) at 48 hrs

0 10 20 30 40 50 60

100

90

80

70

60

50

40

30

20

10

0

Tem

per

atu

re (

°F)

Time (hours)

Tbulk

Tbulk

Twall (inner)

Twall(inner)

Tinterface

Tinterface

Tglycol

Tglycol

0 5

120

110

100

90

80

70

60

50

40

30

20

X

10 2015 25 30 35 40 45 50 55 60


on the wall, insulation effects come into play, and hence the oil/wax interface temperature increases with time. It was observed that interface temperature increased rapidly in the beginning and then seemed to reach a plateau, which indicates the insulation effects ex-erted by the wax to the deposition phenomena. The inner wall tem-perature and interface temperature were calculated on the basis of heat-transfer balance equations.

The interface temperature and initial wall temperature was cal-culated at different times for all the experiments. Fig. 25 plots the effective temperature differences at the beginning of the test with shear stress for each of the tests. It shows a decline in the effective temperature difference with an increase in shear stress. This means that even though the temperature difference between the oil and glycol/water mixture was set at 30°F, the actual driving force was different from 30°F. From the figure, it was observed that the max-imum temperature difference available for wax buildup was around 20°F. The effective ∆Ts were different for the short-term tests. A similar observation can be made from Fig. 26, which shows a de-cline in effective temperature difference at different times with the

Reynolds number, a potential candidate as a correlating parameter in wax deposition.

Deposit Mass and Deposit Mass Density. The wax deposit on the inner wall includes both the wax species that physically precipitate and deposit and the crude oil that is entrained into the wax deposit. This section describes the effect of the effective ∆T and shear at the wall on the wax mass (excluding the entrained oil) and deposit mass density (excluding the entrained oil) only. The deposit mass density is defined as the wax mass per unit area of cross section of the pipe segment. The deposit mass (excluding entrained oil) can be calculated using Eq. 13 (Dwivedi 2010):

( )22 2 1000 ,0014w

i i wF

m d d LδΠ = − − × ....................(13)

where m is the wax mass (no entrained oil) deposited on the pipe wall (g), is the length of the test section (m), rw is the density of the

Fig. 25—Effective temperature difference (short-term experi-ments).

Fig. 27—Deposit mass (no entrained oil) at 24 and 48 hrs. vs. shear stress: 1.0-in. ID tests.

Fig. 26—Effective ΔT vs. Reynolds number.

Fig. 28—Deposit mass (no entrained oil) at 24 and 48 hrs. vs. shear stress: 1.5-in. ID tests.

Tem

per

atu

re (

°F)

Shear Stress (Pa)

Effective Temperature Difference—Initial TimeEffective Temperature Difference—24 hrsEffective Temperature Difference—48 hrs

0 10 20 30 40 50 60

25

20

15

10

5

0

Tem

per

atu

re (

°F)

Reynolds Number

Effective Temperature Difference—InitialEffective Temperature Difference—24 hrsEffective Temperature Difference—48 hrs

0 5000 10000 15000 20000 25000

25

20

15

10

5

0

Dep

osi

t M

ass

(No

en

trai

ned

oil)

(g

m)

Shear Stress (Pa)

Deposit Mass (No entrained oil)—24 hrsDeposit Mass (No entrained oil)—48 hrs

0 10 20 30 40 50 60

60

50

40

30

20

10

0

Dep

osi

t M

ass

(No

en

trai

ned

oil)

(g

m)

Shear Stress (Pa)

Deposit Mass (No entrained oil)—24 hrsDeposit Mass (No entrained oil)—48 hrs

0 10 20 30 40 50 60

120

100

80

60

40

20

0


wax at the oil set temperature (kg/m3) and is assumed to be equal to the density of the oil which is 842 kg/m3, Fw is the wax content obtained from DSC analysis, di is the initial pipe diameter (m), and δ is the deposit thickness (m) at a specified time.

Eq. 13 is strictly used for the analysis of the data acquired in this study. But it can be adapted to real-life cases to estimate the deposit mass if deposit thickness and deposit wax content are known along the pipe if needed. The overall contribution of this paper is toward a qualitative behavior analysis of how wax depo-sition occurs under various shear stresses (flow rates). Currently, there is not enough experimental data to develop and propose a re-liable correlation, which would be a great use to our industry. With this paper, we want to share some of what we have learned with the community.

The uncertainty is too high to develop a reliable correlation using the limited amount of data available at this moment, though several attempts have been made to unify the data to consider the shear effects and nondimensionalized heat-transfer parameters (for example, a Nusselt number and Lewis number under turbulent flow conditions). However, this is a continuing effort at TUPDP. Our

current experimental study should provide us more data that can be used to develop a better correlation in the near future.

From Fig. 27, it is easy to see that the deposit mass at 24 hours without considering the entrained oil first increases to a certain value and then decreases with an increase in wall shear stress. For the deposit mass at 48 hours, the trend is somewhat decreasing, with an increase in shear stress. These results were found to be similar to the observations found by Solaimany Nazar (2001). He stated that an increase in the flow rate leads to an increase in the amount of mass deposited up to a specific flow rate, namely the critical flow rate. Beyond this critical value, a further increase in flow rate causes a decrease of deposit mass because of the sloughing effect in high-turbulence regions. However, he did not perform any analysis on the effective ∆T for wax deposition for their tests. He only as-sumed that the inner wall temperature of the pipe was the same as that of the glycol/water mixture. Hence, the decrease in the deposit mass after a certain increase can not be completely attributed to shear effects. Because the effective ∆T, the thermodynamic driving force for wax buildup, also reduces with an increase in shear stress, the decrease in the deposit mass can be attributed to the combina-

Tota

l Dep

osi

t M

ass

(gm

)

Shear Stress (Pa)

Total Deposit Mass—24 hrsTotal Deposit Mass—48 hrs

0 10 20 30 40 50 60

160

140

120

100

80

60

40

20

0

Tota

l Dep

osi

t M

ass

(gm

)

Shear Stress (Pa)

Total Deposit Mass—24 hrsTotal Deposit Mass—48 hrs

0 10 20 30 40 50 60

300

250

200

150

100

50

0

Fig. 29—Total deposit mass at 24 and 48 hrs. vs. shear stress: 1.0-in. ID tests (pressure drop).

Fig. 31—Deposit mass/area (no entrained oil) vs. shear stress.

Fig. 30—Total deposit mass at 24 and 48 hrs. vs. shear stress: 1.5-in. ID tests (pressure drop).

Fig. 32—Total deposit mass/area of pipe vs. shear stress.

Dep

osi

t M

ass/

Init

ial P

ipe

Are

a(N

o e

ntr

ain

ed o

il) (

gm

/cm

2 )

Shear Stress (Pa)

Deposit Mass/area (No entrained oil)—24 hrsDeposit Mass/area (No entrained oil)—48 hrs

0 10 20 30 40 50 60

9

8

7

6

5

4

3

2

1

0

Tota

l Dep

osi

t M

ass/

Init

ial P

ipe

Are

a (g

m/c

m2 )

Shear Stress (Pa)

Total Deposit Mass/area—24 hrsTotal Deposit Mass/area—48 hrs

0 10 20 30 40 50 60

25

20

15

10

5

0


tion of both the effects. Fig. 28 shows the same behavoir for experi-ments performed in 1.5-in ID pipe.

In Figs. 29 and 30, the trend of total deposit mass was found to be decreasing, with an increase in shear stress or decrease in the initial effective ∆T. Hence, the difference in the trend of de-posit mass with and without entrained oil can be attributed to wax content.

The diameter effects were also considered using different test sections in this study. Fig. 31 shows the trend of deposit mass (ex-cluding entrained oil) per unit initial area of the test section, which can also be termed as deposit density (gm/cm2) with respect to an increase in shear stress. Fig. 32 displays the values for total deposit mass per unit initial area of test section. For the 24-hour case, the deposit mass (no entrained oil) per unit initial area of the pipe in-creased to a certain value and then decreased, whereas the deposit mass (no entrained oil) per unit initial area of the pipe has a de-creasing trend at 48 hours.

ConclusionsIn general, a continuous smooth increase in deposit thickness with time was observed in all the experiments, which resulted in an in-crease in pressure drop across the test section. No signs of sloughing were observed around the port sections in the small-scale facility. Because there was no provision to visually inspect the whole test section, it cannot be determined if there was no sloughing for high-flow-rate tests.

Shear stress at the wall and the Reynolds number change as the wax builds up in the pipe because it reduces the area of cross sec-tion. Wall shear stress should be referred to as initial shear stress. It was found that the percentage change in shear stress was higher for the experiments with low initial shear stress than for those with high initial shear stress.

Although the ∆T maintained during any experiment was 30°F to start with, it was transpired from heat-balance calculations that the effective temperature difference, which is the driving force for wax deposition, was different than 30°F for almost every test. It was seen from the calculations that the interface temperature in-creases as the wax builds up in pipe, creating an insulation effect. The initial effective ∆T available for wax deposition is actually the difference between the oil bulk and the initial inner pipe wall tem-perature. It is imperative to know the effective ∆T to compare dif-ferent experiments.

• The effective ∆T was not the same in all the experiments. It decreased with an increase in initial wall shear stress, which demonstrates that the initial inner pipe wall temperature rises when the pipe is subjected to high flow rates. There is a com-bined effect of decreasing effective ∆T and increasing initial wall shear stress on wax-deposition characteristics.

• Both shear stress and Reynolds number were found to be cor-relating parameters for decrease in deposit thickness. Dimen-sionless deposit thickness δ/r decreases with increase in wall shear stress/Reynolds number and effective ∆T. This observa-tion is in line with the analysis of data from past studies.

• Deposition growth with time in the experiments decreased with increase in initial shear stress or decrease in effective ∆T. For 1.0-in. ID experiments, it was found that the initial depo-sition rate was higher for the first few hours for the tests with higher initial shear stress than for those with lower initial wall shear stress for a longer duration, which did not seem to affect the overall deposition rate.

• The wax content increased almost linearly with an increase in initial shear stress measured from GC and DSC depicting aging effects. The deposits were soft for the tests with lower oil velocities.

• The total deposit mass clearly had a decreasing trend when in-creasing the shear stress and decreasing the effective ∆T, which indicates that the wax content plays a major role in the de-posit mass (no entrained oil). The deposit density at 24 hours,

which combines the effect of difference in pipe diameter, was observed to follow the trend of deposit mass (Solaimany Nazar 2001). For the short-term tests, the deposit mass (no entrained oil) increased in the beginning and then decreased with an increase in the initial shear stress or effective ∆T. The decrease in the deposit mass can be attributed to both the in-crease in turbulence and the decrease in effective ∆T for high flow rates.

The published paraffin-deposition data in literature are still not sufficient enough to develop reliable predictive tools that cap-ture all the paraffin-deposition characteristics in part because of long testing times required. Further experimental studies to en-hance the understanding of the physics of wax-deposition phe-nomena are needed. These experimental studies should focus on better understanding of the deposition physics at a microscopic level while continuing with the macroscale experiments. This will require development of experimental measurement techniques at crystallization length scales under various flowing conditions. The experimental results can collectively lead to the development of paraffin-deposition models that can better predict deposition in the field.

AcknowledgmentsThe authors would like to thank the members of TUPDP for funding this study. TUPDP staff involved in the experimental work are also acknowledged for their dedication.

ReferencesBenallal, A., Maurel, P., Agassant, J.F. et al. 2008. Wax Deposition in

Pipelines: Flow-Loop Experiments and Investigations on a Novel Approach. Presented at the SPE Annual Technical Conference and Exhibition, Denver, 21–24 September. SPE-115293-MS. http://dx.doi.org/10.2118/115293-MS.

Bruno, A. 2006. Paraffin Deposition of Crude Oil and Water Dispersions under Flowing Conditions. MS thesis, The University of Tulsa, Tulsa, Oklahoma.

Creek, J.L. and Hobson, G.G. 1996. ADEX 2 Wax Deposition Study, ANOA Pipeline Evaluation. Report TM96000354, Chevron Petroleum Com-pany, La Habra, California (May 1996).

Dwivedi, P. 2010. An Investigation of Single-Phase Wax Deposition Char-acteristics of South Pelto Oil Under Turbulent Flow. MS thesis, The University of Tulsa, Tulsa, Oklahoma.

Hernandez, O. 2002. Investigation of Single-Phase Paraffin Deposition Characteristics. MS thesis, The University of Tulsa, Tulsa, Okla-homa.

Hsu, J.J.C., Santamaria, M.M., and Brubaker, J.P. 1994. Wax Deposition of Waxy Live Crudes Under Turbulent Flow Conditions. Presented at the SPE Annual Technical Conference and Exhibition, New Orleans, 25–28 September. SPE-28480-MS. http://dx.doi.org/10.2118/28480-MS.

Jennings, D.W. and Weispfennig, K. 2005. Effects of Shear and Temper-ature on Wax Deposition: Coldfinger Investigation With a Gulf of Mexico Crude Oil. Energy Fuels 19 (4): 1376–1386. http://dx.doi.org/10.1021/ef049784i.

Matlach, W.J. and Newberry, M.E. 1983. Paraffin Deposition and Rheo-logical Evaluation of High Wax Content Altamont Crude Oils. Pre-sented at the SPE Rocky Mountain Regional Meeting, Salt Lake City, Utah, 22–25 May. SPE-11851-MS. http://dx.doi.org/10.2118/11851-MS.

Solaimany Nazar, A.R., Dabir, B., Vaziri, H. et al. 2001. Experimental and Mathematical Modeling of Wax Deposition and Propagation in Pipes Transporting Crude Oil. Presented at the SPE Production and Oper-ations Symposium, Oklahoma City, Oklahoma, 24–27 March. SPE-67328-MS. http://dx.doi.org/10.2118/67328-MS.

Weingarten, J.S. and Euchner, J.A. 1988. Methods for Predicting Wax Precipitation and Deposition. SPE Prod Eng 3 (1): 121–126. SPE-15654-PA. http://dx.doi.org/10.2118/15654-PA.


Priyank Dwivedi is a commercialization engineer at Schlumberger In-formation Solutions. He began his career as a mechanical engineer at Larsen & Toubro, India, working on design of offshore platforms and FPSOs. He holds an MS degree in petroleum engineering from the Uni-versity of Tulsa (TU), where he worked with the Paraffin Deposition project research consortium.

Cem Sarica is currently a professor of petroleum engineering, and is the Director of three industry-supported consortia at TU: Fluid Flow, Par-affin Deposition, and Horizontal Well Artificial Lift Projects. He was as an associate professor of petroleum and natural gas engineering at Penn-sylvania State University and an assistant professor of petroleum and natural gas engineering at Istanbul Technical University (ITU) before joining TU. He has over 100 publications, mostly in SPE journals and proceedings, and his research interests are production engineering, multiphase flow in pipes, flow assurance, and horizontal wells. He cur-rently serves as a member of the SPE Projects, Facilities and Construc-

tion Advisory Committee and as a member of SPE Production and Operations Award Committee. He has previously served as a member of SPE Production Operations and Books Committees, and was a member of the SPE Journal Editorial Board between 1999 and 2007. He is the recipient of 2010 SPE International Production and Operations Award, and was recognized as a Distinguished Member of SPE in 2012. He holds BS and MS degrees in petroleum engineering from ITU and a PhD degree in petroleum engineering from TU.

Wei Shang is currently a faculty member at Cape Breton University (CBU), Canada. His main research interests are in the field of thermo-fluids, multiphase flow, and energy recovery systems. Before coming to CBU, he was with TU for several years. Before he joined TU, he worked with Robert W. Besant on many JIPs at the University of Sas-katchewan, Canada. They developed several new test methods together for the HVAC industry. He is author of 30 refereed journal publications. Shang holds BS, MS, and PhD, degrees all in mechanical engineering.

experimental study on wax-deposition …...bruno (2006) reported results on the south pelto crude...

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