Influence of heat transfer model on temperature and pressure distribution and steady state performance of CO2 dry gas seal under near critical condition

doi:10.11949/0438-1157.20210407

Abstract

Abstract:

The proper selection of heat transfer model between fluid film and sealing ring plays an important role in the accurate calculation of temperature and pressure distribution and steady state performance of dry gas seal. At close critical point of CO₂, a comparative study on the heat transfer model, including isothermal model, adiabatic model and conjugate heat transfer model, on temperature-pressure distribution, opening force and leakage rate of supercritical CO₂ dry gas seal was conducted. The applicability of the isothermal model and the adiabatic model under different rotating speed and film thickness was discussed. Moreover, the difference between supercritical CO₂ and air dry gas seal on temperature-pressure distribution and steady-state performance were studied. The results show that compared with conjugate heat transfer model, the isothermal model assumption is suitable for the low-speed flow with small film thickness, while the opening force is lower and the leakage rate is higher. However, the adiabatic model assumption is suitable for the high-speed flow with large film thickness. The temperature distribution of supercritical CO₂ dry gas seal under the small film thickness is similar to that of the air dry gas seal, and the pressure distribution of them two at large film thickness is just the same. However, compared to the air dry gas seal, the temperature of supercritical CO₂ dry gas seal at large film thickness is much lower, while the pressure of which at small film thickness is larger.

Key words: supercritical carbon dioxide, dry gas seal, heat transfer model, conjugate heat transfer model, temperature and pressure distribution

摘要：

干气密封流体膜与密封环间传热模型的合理选取对于准确求解密封温压分布和稳态性能至关重要。在CO₂近临界工况下，对比研究了密封环等温模型、绝热模型和共轭热传递模型对超临界CO₂干气密封端面温度、压力分布和开启力、泄漏率等稳态性能的影响，探讨了不同膜厚和转速条件下密封环等温模型和绝热模型的适用性，并基于共轭热传递模型研究了超临界CO₂和空气介质干气密封的温压分布和稳态性能差异。结果表明：以共轭热传递模型计算结果为基准，密封环等温模型假设适用于小膜厚低速流动工况，不过开启力偏低而泄漏率偏高，绝热模型假设适用于大膜厚高速流动工况；相较于空气介质干气密封，超临界CO₂干气密封在小膜厚下的温度分布和大膜厚下的压力分布基本接近，不过小膜厚下的温度更低，而在大膜厚下的压力更高。

关键词: 超临界CO₂, 干气密封, 传热模型, 共轭热传递模型, 温压分布

CLC Number:

TH 117.2

Peng JIANG, Jinbo JIANG, Xudong PENG, Xiangkai MENG, Yi MA. Influence of heat transfer model on temperature and pressure distribution and steady state performance of CO₂ dry gas seal under near critical condition[J]. CIESC Journal, 2021, 72(8): 4239-4254.

江鹏, 江锦波, 彭旭东, 孟祥铠, 马艺. 传热模型对近临界工况CO₂干气密封温压分布和稳态性能影响[J]. 化工学报, 2021, 72(8): 4239-4254.

Figures/Tables 22

Fig.1 Schematic diagram of a typical spiral groove dry gas seal

Fig.2 Grid meshing on calculation domain of dry gas seal

Fig.3 Thermal boundary conditions of dry gas seal under different heat transfer models

Fig.4 Flow chart of flow field parameter calculation of dry gas seal gap

Table 1 Dry gas seal operating conditions and structural parameters of type groove

工况及参数	数值
槽根半径r_g/mm	69
槽数	12
槽深h_g/μm	5
螺旋角β/(°)	15
周向槽宽比α	0.5
进口压力p_in/MPa	8
进口温度T/K	360
动环转速n/(kr/min)	10
膜厚h₀/μm	6

Table2 Dry gas seal ring structure and material parameters

参数	数值
外径r_o/mm	77.78
内径r_i/mm	58.42
静环外周与密封腔内壁间隙δ_s/mm	20
动环外周与密封腔内壁间隙δ_r/mm	20
热导率k/(W/(m·K))	57
密度ρ/(kg/m³)	3150
比定压热容c_p/ (J/(kg·K))	710

Table 3 The heat transfer coefficient of the circumferential face of the rotor and stator ring at different rotational speeds

转速n/ (r/min)	对流传热系数/(W/(m²·K))
	动环		静环
	空气	CO₂	空气	CO₂
2000	—	3683	—	2876
6000	—	6014	—	2876
10000	5078	8188	1556	2876

Fig.5 Verification of grid independence of dry gas seal fluid domain

Fig.6 Comparison of radial pressure and temperature distribution of dry gas seal between calculated results and literature values

Fig.7 Schematic diagram of the characteristic section position of dry gas seal fluid domain

Fig.8 Temperature and pressure distribution of dry gas seals lubricated with two kinds of gas under different film thickness

Fig.9 Temperature distribution on radial section of dry gas seal ring and fluid film with different sealing gas

Fig.10 Radial temperature and pressure distribution of dry gas seal lubricated with two kinds of gas under different film thickness

Fig.11 Radial distribution of Mach number in dry gas seals lubricated with two kinds of gas under different film thickness

Fig.12 Axial and radial distribution of film temperature of sCO2 dry gas seal under different heat transfer models

Fig.13 Radial distribution of temperature and pressure differential at different circumferential sections of sCO2 dry gas seal

Fig.14 Radial temperature and pressure distribution of sCO2 dry gas seal under different heat transfer models and rotating speed

Fig.15 Radial temperature and pressure distribution of sCO2 dry gas seal under different heat transfer models and film thickness

Fig.16 Radial distribution of heat flux in dry gas seal of sCO2 under conjugated model

Fig.17 Influence of rotating speed and film thickness on opening force and leakage rate of dry gas seal lubricated with two kinds of gas

Fig.18 The opening force of sCO2 dry gas seal with rotating speed and film thickness under different heat transfer models

Fig.19 The leakage rate of sCO2 dry gas seal with film thickness and rotating speed under different heat transfer models

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Influence of heat transfer model on temperature and pressure distribution and steady state performance of CO₂ dry gas seal under near critical condition

传热模型对近临界工况CO₂干气密封温压分布和稳态性能影响

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