Numerical Analysis of Needle Valve for Cryogenic Applications

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Special Issue on International Journal on Theoretical and Applied Research in Mechanical Engineering (IJTARME) V-5 No.1 ISSN (Print): 2319-3182, For National Conference on Advances in Design and Thermal Engineering (NCADTE-2016)

G.H. Raisoni College of Engineering & Management, Chass, Ahmedanagar, Maharashtra 17th to 18th February 2016 25

Numerical Analysis of Needle Valve for Cryogenic Applications

1A. Y. Balande, ²D. S. Watvisave, ³Tansen Chaudhari

1,2Department of Mechanical Engineering, Sinhgad College of Engineering, Pune, India

3Fluid Controls Private Limited, Pune, India

Email: ¹[email protected], ²[email protected], ³[email protected]

Abstract- Flow control valves used for cryogenic application are critical components of the system.

Performance of valve is tested before it is used in the system to ensure safe and desired operation. Leakage rate in valves used at cryogenic temperature is more as mating parts are subjected to the contraction. In this study analysis of Needle valve is carried out to ensure its performance at very low temperature. To obtain the relation between flow, geometry and pressure drop, analysis using CFD code is carried out and results are evaluated. Thermal analysis of valve is done to understand the effect of cryogenic temperature for which thermal stress and thermal deformation is calculated.

Keywords- Analysis, Cryogenics, Computational Fluid Dynamics (CFD), Needle Valve.

I. INTRODUCTION

Cryogenic valves are used for very low temperature applications such as in transfer and storage of cryogenic fluid (Ex. Liquefied Natural Gas, Liquefied Nitrogen at temperature below -150⁰C). At such low temperature properties of component and material changes and this change is required to be considered while designing the valves. If normal temperature valve is used at cryogenic temperature different problems may arise such as the contraction of parts which will be responsible for the disturbed geometry of valve causing more leakage, thermal stresses induced in the valves due to which valve strength may be affected, cryogenic liquid trapped in between the moving parts of the valves which will affect the desired working of valve, heat transfer from surrounding to the valve causing increase in pressure, inside the valve.

To overcome this kind of difficulties cryogenic valves are used having different design and material of construction. Design of valve for cryogenic applications required special considerations as compared to valve used at normal temperature. As flow of fluid in valve will have different pressure at different position, that pressure will be operating conditions so it necessary to calculate pressure at different points and at the same time temperature effect is to be considered.

II. RELATED WORK

Multidisciplinary design optimization (MDO) is necessary for valves as it is grouped into critical component of the system so that different parameter can be analyzed to ensure its design. Dai Ye et al. [1]

performed multi physics field analysis of nuclear power

valve based on MDO model. Multi physics analysis that includes static structural analysis, thermal mechanical coupling analysis, flow field analysis and seismic analysis is done on nuclear power valve. Using MDO model different working characteristic is predicated under loading condition before it is being used in the system. Above FEA analysis was verified valve strength and sealing test.

Oza et al. [2] carried out the CFD simulation to understand the performance of globe valve for oxygen flowing at high pressure through it. In this paper axisymmetric numerical model is used for the prediction of flow characteristics for globe style flow control valve.

The turbulent kinetic energy increases as the plug retracted beyond the plane of seat. The k-ѡ model gave higher values of velocity and turbulent kinetic energy than the k-ε model since the latter captures lesser recirculation and is more suitable for boundary level flow.

Moore et al. [3] carried cryocooler test for development and testing of passive check valve, in this experiment one additional step was taken with the conventional assembly and installation of valve, to improve the sealing. As PTFE goes through a phase transition at about 170 K, but it also gets soften as the temperature is increased above room temperature (-295 K). To improve sealing performance of seat, the valve is immersed in a bath of 50 °C water and the valve is sealed with a preload pressure difference of 10 psi. The results of tests on a pulse tube cryocooler setup prove a scaling argument which can be used to predict the sealing flow rate of a valve using results from tests at liquid nitrogen temperatures. A more effective method for preforming the reed valve is also discussed, resulting in orders of magnitude improvement over other methods. This improved iteration can be scaled to different temperatures, providing a versatile passive check valve for various cryogenic applications.

CFD analysis on dynamic flow characteristics of the pilot control globe valve was presented by Jin-yuan Qian et al. [4] to show that PCGV is having consistent design such as simple structure and lower driving energy. Pressure difference is used to control the valve core flow and it is found that the opening time is short.

Study shows that appropriate spring stiffness is to be selected in design process to make sure that valve core can work in optimal design condition.

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Tyler Brosten et al. [5] presented numerical flow model and experimental results of cryogenic micro valve for distributed cooling application. Experimental data for the flow of various gases through prototype micro valve design is obtained at room temperature and at liquid nitrogen temperature with pressure difference of 100 kPA across the inlet and outlet.

Structural seismic analysis based on the seismic service condition for butterfly valves in nuclear power plant performed by the Sang UK Han et al. [6]. The analytical and experimental analysis where performed and both the methods compared and found 3% error. Static analysis found maximum stress of 135MPa at contact area between topside of stem and body. In case of dynamic analysis maximum stress was 183 MPa.

Experimental cryogenic leak testing of tube fitting/

valves was performed by Jia et al. [7] for that high pressure and variable temperature cryogenic leak testing system was designed to conduct the experiment. In this experiment high pressure helium gas was used instead of cryogenic liquid considering the safety. The was carried out on KC126 fettings used for space shuttle results shows that fettings started to leak at 205 K and has a leak mass flux of 1.28*10^-3 kg min^-1 at 77 K.

III. NEEDLE VALVE

Needle valves are used in variety of industries to regulate the flow of fluid very precisely. Generally it is used to control the flow passing through gauges to avoid damage due to high pressure fluid flow. Needle valves are used in application where flow of fluid must gradually decrease or the application where very less flow rate is required. Needle valves have a slender, tapered point at the end of the valve stem that is lowered through the seat to restrict or block flow. Fluid flowing through the valve turns 90 degrees and passes through an orifice that is the seat for a rod with a cone shaped tip. Different parts of needle valve are body, bonnet, bonnet nut, stem, packing, handle. Stainless Steel or Cast Iron is generally used for design of body, bonnet, handle and other parts of valve. PTFE or Grafoil is used for the packing. Figure 1 shows the needle valve.

Fig 1: Needle Valve

IV. CFD ANALYSIS OF NEEDLE VALVE

Fluid flow analysis is performed using CFD code ANSYS FLUENT. Figure 2 show the model and Meshed fluid Domain. Modeling of valve is done in SOLIDWORKS and imported in ANSYS ICEM meshing software to extract the flow domain and perform meshing on that. Meshing at the boundary at which fluid and valve is in contact, is made fine compared to inside volume to capture the boundary effect. Total number of elements are 484296 and nodes are 84702. Tetrahedral type of meshing is used. Inlet boundary condition is inlet pressure of 264 kg/cm² and temperature is -150 ⁰C. Fluid flowing through the valve is Liquid Nitrogen having density 806.08 Kg/m³.

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Fig. 2: (a) Model of Needle Valve, (b) Meshed Fluid Domain

Flow analysis is performed to obtain the velocity and pressure distribution along the valve. Figure 3 shows velocity distribution along the valve at open condition.

At different position planes are created to represent the velocity profile in the valve. It can be seen that velocity at the center of each flow domain is higher compared to velocity of flow near the wall, representing boundary layer formation due to no sleep condition.

Fig. 3: Velocity profile at different location in valve Figure 4 shows the pressure distribution inside flow domain of Needle Valve, maximum pressure is at inlet with decreasing pressure towards outlet representing pressure drop in the valve. This pressure profile represent the variable distributed load in the valve which is used to calculate leakage through valve.

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Fig 4: Pressure distributions in valve

V. THERMAL ANALYSIS ON NEEDLE VALVE

Static thermal analysis on valve is performed to understand the effect of cryogenic temperature.

Boundary condition is -150 ⁰C. Thermal stress, deformation and stain is calculated. Figure 4 represents the thermal analysis of valve which shows the maximum thermal stress induced is 67.439 MPa. Maximum stress obtained is large therefore it is required to consider in design of valve. Maximum deformation obtained is 0.2734 mm.

Fig 5: Thermal stress induced in valve

VI. CONCLUSION

Analysis on Needle valve for cryogenic application is performed to understand the different parameters that are required for the design of valve. At cryogenic temperature valve is subjected thermal deformation of 0.2734 mm which is to be considered while design of valve. Thermal deformation calculated is used to calculate leakage rate. Above analysis is required to be validated with the experimental analysis of valve for that cryogenic leak testing is to be performed.

REFERENCES

[1] Dei Y., Tian C., Multi physics field analysis of nuclear power valve based on the MOD model, International Journal Control And Automation, 2014, (7), pp. 363-372.

[2] Oza A., Ghosh S., Chowdhary K., CFD modeling of Globe valve for Oxygen Application, Australasian fluid mechanics, 2007, (16), pp.

1356-1362.

[3] S0011-2275-(14)00108-8, Madison, 2014, Development and Testing of a Passive Check Valve for Cryogenic Applications, 2014 (12).

[4] Jin-yuan Qian, Lin Wei, Zhi-jiang Jin, Jian-kai Wang, Han Zhang, An-le Lu. CFD analysis on the dynamic flow characteristics of the pilot- control globe valve, Energy conservation and management, Elsevier, 2014, (87), pp. 220-226.

[5] Tyler R. Brosten et al. A numerical flow model and experimental results of a cryogenic micro- valve for distributed cooling applications, Cryogenics, Elsevier, 2007, (47), pp. 501-509.

[6] Sang U., Ahn D., Lee M., Structural Safety Analysis Based On Seismic Service Conditions for Butterfly Valves in a Nuclear Power Plant.

2014, (9), pp. 01-09.

[7] FL33431, Jia L., Florida Atlantica University, Boca Raton, , USA., Cryogenic leak testing of tube fitting/valves by Department Of Mechanical Engineering, 1992.

[8] 3048362, New York, Aug. 7, 1962, Cryogenic valve, 1962.

[9] Veenstra T., Development of a Stainless Steel Check Valve for Cryogenic Applications.

Cryogenics, 2007, (47), pp. 121-126.

[10] FL33431, United States, June 3,1986, Low pressure cryogenic liquid delivery system.

[11] FL9854, United states, June 2008, Bidirectional valve for cryogenic system.

[12] 3048362, Egypt, August, 1961, Cryogenic valves, Mar 1962.

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