Unavoidable Destroyed Exergy in Crude Oil Pipelines due to Wax Precipitation
Abstract
:1. Introduction
2. Definition of Unavoidable Destroyed Exergy
3. Determination of Unavoidable Destroyed Exergy for Waxy Crude Oil
3.1. Crude Oil Critical Transition Temperature
3.2. Determination of the Specific Heat Capacity of Waxy Crude Oil
3.3. Temperature Range of Pipeline Transportation
3.4. Calculation of Unavoidable Destroyed Exergy
3.4.1. Unavoidable Thermal Destroyed Exergy
3.4.2. Unavoidable Pressure Destroyed Exergy
3.5. The Calculation Process of Unavoidable Destroyed Exergy
4. Calculation Example
4.1. Basic Data
4.1.1. Critical Transition Temperature
4.1.2. Pipeline Transmission Temperature Intervals
4.1.3. Theoretical Outstation Temperature
4.2. Calculation Results and Analysis of Unavoidable Destroyed Exergy
4.3. Influence of Design Parameters on Unavoidable Destroyed Exergy Loss
4.3.1. Change with Pipeline Diameter
4.3.2. Change with Insulation Layer Thickness
4.3.3. Change with Buried Depth
4.4. Influence of Operational Parameters on Unavoidable Destroyed Exergy
4.4.1. Throughput
4.4.2. Outstation Temperature
4.4.3. Outstation Pressure
5. Conclusions
Author Contributions
Funding
Conflicts of Interest
Nomenclature
Re | Reynolds number (−) |
dynamic viscosity coefficient (N·s/m2) | |
D | inner diameter of oil pipeline (m) |
crude oil flow velocity (m/s) | |
oil flow viscosity (m2/s) | |
density (kJ/m) | |
T | the crude oil temperature (°C) |
P | pressure (Pa) |
c | crude oil specific heat capacity (kJ/(kg·°C) |
A | consistency coefficient fitting constant parameter (−) |
B | consistency coefficient fitting constant paramete (−) |
a | fitting constant of specific heat capacity curve (−) |
m | fitting constant of specific heat capacity curve (−) |
K | pipeline total heat transfer coefficient (W/(m2 °C) |
S | pipe section area (m2) |
h | friction loss (m) |
Q | pipe volume flow (m3/s) |
L | pipeline length (km) |
G | oil mass flow (kg/s) |
i | hydraulic gradient (−) |
crude oil consistency coefficient (Pa·s) | |
crude oil rheological constant parameter (−) | |
Subscripts | |
x | exergy (kJ) |
U | unavoidable (−) |
A | avoidable (−) |
min | theoretical minimums (−) |
c | Newtonian flow critical point (−) |
MRc | non-Newtonian flow critical point (−) |
sl | wax appearance point (−) |
F | abnormal point (−) |
0 | ambient (−) |
R | initial point (−) |
L | terminal point in different temperature ranges (−) |
Z | end point |
Rl | theoretical terminal point |
Zl | theoretical end point |
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Parameter | ||||
---|---|---|---|---|
Shengli crude oil | 0.4840 | 1.9255 | 0.03465 | 0.01164 |
Daqing crude oil | 0.9085 | 1.7585 | 0.01732 | 0.01567 |
Puyang crude oil | 0.6753 | 1.7258 | 0.0264 | 0.01217 |
Renqiu crude oil | 0.1970 | 1.8880 | 0.0476 | 0.02117 |
Item | Data | Item | Data |
---|---|---|---|
Pipeline length | 45121 m | Pipeline diameter | Φ219 × 5.6 mm |
Buried depth | 1600 mm | Wax Appearance point | 47.7 °C |
Outstation temperature | 65 °C | Anomalous point | 36.2 °C |
Outstation pressure | 4.5 MPa | Condensation point | 25 °C |
Pipeline throughput | 70 m3/h | Density (30 °C) | 860 kg/m3 |
Ambient temperature | −4.4 °C | Density (50 °C) | 830 kg/m3 |
Soil thermal conductivity | 1.4 W/(m·°C) | Viscosity (30 °C) | 70 mPa·s |
Pipe thermal conductivity | 45.24 W/(m·°C) | Viscosity (50 °C) | 9.41 mPa·s |
Pipeline Transmission Temperature Region | Newton Turbulent Non-Wax Precipitation | Newton Turbulent Wax Precipitation | Non-Newton Turbulence | Whole Process of Crude Oil Pipeline Transportation |
---|---|---|---|---|
The unavoidable pressure destroyed exergy (kJ/s) | 7.749 | 15.828 | 0.042 | 23.621 |
The unavoidable thermal destroyed exergy (kJ/s) | 373.379 | 315.716 | 30.217 | 719.313 |
The unavoidable destroyed exergy (kJ/s) | 381.128 | 331.544 | 30.259 | 742.934 |
The ratio between unavoidable pressure destroyed exergy and pressure destroyed exergy (%) | 9.409 | 22.202 | 0.328 | 14.178 |
The ratio between unavoidable thermal destroyed exergy and thermal destroyed exergy (%) | 58.429 | 61.883 | 34.786 | 58.193 |
Pipeline Diameters | 168 mm | 219 mm | 273 mm | 323 mm | |
---|---|---|---|---|---|
Interval length of pipe transmission (km) | Newton no-wax precipitation | 37.450 | 28.877 | 24.816 | 21.685 |
Newton wax precipitation | 7.671 | 16.244 | 20.305 | 21.631 | |
non-Newton turbulence | / | / | / | 1.805 | |
End point temperature (°C) | Newton no-wax precipitation | 43.83 | 47.81 | 47.64 | 47.86 |
Newton wax precipitation | 40.47 | 40.26 | 37.39 | 36.61 | |
non-Newton turbulence | / | / | / | 35.85 | |
Theoretical outstation temperature (°C) | 41.32 | 43.44 | 43.64 | 42.57 |
Throughput | 50 m3/h | 60 m3/h | 70 m3/h | 80 m3/h | 90 m3/h | 100 m3/h | |
---|---|---|---|---|---|---|---|
Pipeline interval length (km) | Newton no-wax precipitation | 14.438 | 17.597 | 20.304 | 23.914 | 27.975 | 29.779 |
Newton wax precipitation | 14.438 | 16.243 | 18.951 | 21.207 | 17.146 | 15.342 | |
Non-Newton turbulence wax precipitation | 8.573 | 11.281 | 5.866 | / | / | / | |
Non-Newton laminar wax precipitation | 7.671 | / | / | / | / | / | |
Total heat transfer coefficient (W/m2 °C) | Newton no-wax precipitation | 0.469 | 0.472 | 0.470 | 0.476 | 0.471 | 0.471 |
Newton wax precipitation | 0.447 | 0.460 | 0.468 | 0.467 | 0.469 | 0.470 | |
Non-Newton turbulence wax precipitation | 0.416 | 0.42652 | 0.461 | / | / | / | |
Non-Newton laminar wax precipitation | 0.356 | / | / | / | / | / |
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Cheng, Q.; Yang, J.; Zheng, A.; Yang, L.; Gan, Y.; Liu, Y. Unavoidable Destroyed Exergy in Crude Oil Pipelines due to Wax Precipitation. Entropy 2019, 21, 58. https://doi.org/10.3390/e21010058
Cheng Q, Yang J, Zheng A, Yang L, Gan Y, Liu Y. Unavoidable Destroyed Exergy in Crude Oil Pipelines due to Wax Precipitation. Entropy. 2019; 21(1):58. https://doi.org/10.3390/e21010058
Chicago/Turabian StyleCheng, Qinglin, JinWei Yang, Anbo Zheng, Lu Yang, Yifan Gan, and Yang Liu. 2019. "Unavoidable Destroyed Exergy in Crude Oil Pipelines due to Wax Precipitation" Entropy 21, no. 1: 58. https://doi.org/10.3390/e21010058
APA StyleCheng, Q., Yang, J., Zheng, A., Yang, L., Gan, Y., & Liu, Y. (2019). Unavoidable Destroyed Exergy in Crude Oil Pipelines due to Wax Precipitation. Entropy, 21(1), 58. https://doi.org/10.3390/e21010058