ISSN 00406015, Thermal Engineering, 2014, Vol. 61, No. 13, pp. 919–923. © Pleiades Publishing, Inc., 2014. Original Russian Text © V.E. Nakoryakov, A.N. Tsoy, I.V. Mezentsev, A.V. Meleshkin, 2014, published in Izvestiya RAN. Energetika.
Explosive Boiling of Liquid Nitrogen V. E. Nakoryakov, A. N. Tsoy, I. V. Mezentsev, and A. V. Meleshkin Kutateladze Institute of Thermophysics, Siberian Branch, Russian Academy of Sciences, pr. Akademika Lavrent’eva 1, 630090 Novosibirsk, Russia email:
[email protected] Received December 19, 2013
Abstract—The present paper deals with experimental investigation of processes that occur when injecting a cryogenic fluid into water. The optical recording of the process of injection of a jet of liquid nitrogen into water has revealed the structure and the stages of this process. The results obtained can be used when studying a new method for producing gas hydrates based on the shockwave method. Keywords: liquid nitrogen, cryogenic fluid, explosive boiling, gas hydrates DOI: 10.1134/S0040601514130060
INTRODUCTION A project of creation of a piston cryogenic engine using a cryogenic liquid as a working medium is known [1, 2]. The essence of this concept is that, during the controlled supply of a cryogenic agent into fluid, fast boiling and expansion occurs that would result in a drastic increase in the internal pressure. Experimental investigations on injection of a cryogenic agent into water were carried out [3–5]. In the work [3] it was found that there occurs a thick vapor blanket consist ing of gas that surrounds the cryogenic liquid being injected during change of the phases, which takes place in the medium being introduced. In the work [4], experiments were conducted on injection of liquid nitrogen into a relatively large volume of water at the ambient temperature of 293 K. It was recorded that the pressure and the pressure rise rate increased almost linearly when the injection pressure increased, and reached 2.8 bar and 5.0 bar/s, respectively, at the rate of liquid nitrogen injection of approximately 0.85 m/s. In the work [5], cryogenic fluid was fed into the small volume vessel (140 mL). The volume of cryogenic liq uid being injected was small—approximately 2 mL. For example, on injection of liquid nitrogen into water under the pressure of 7 bar the pressure reaches the amplitude of 14 bar 5 s after the injection. Previously, the authors carried out the experimen tal investigation into dynamics of shock waves when capsules with liquid nitrogen exploded [6, 7]. The object of the investigation was to determine the ampli tudes of pressure jumps being developed, since a cer tain level of pressure is a necessary condition for a pro cess of hydrate formation when the shockwave method is used. The maximum pressure amplitude in these experiments was 35 bar, while the pressure rise rate was 115 bar/s. An advantage of the shockwave
method [8, 9] as compared to known analogues is a considerable (by an orderofmagnitude and higher) intensification of the process of formation of gas hydrates. The experimental investigation into the pro cesses of dissolution and formation of gas hydrates fol lowing the shock wave have been presented in the works [10–12]. In the present work, we experimentally investigated the highrate processes that occurred on injection of a cryogenic liquid into water. The results obtained were part of works required for developing a new method for producing gas hydrates that is based on the shockwave method. Experimental Facility and the Procedure Using the technology of the production of intense shock waves by exploding capsules with liquid nitro gen, experimental investigations have been carried out [6, 7]. In the course of selection of a dose of liquid nitrogen and a volume of a cryogenic capsule, the regime of nitrogen explosion with the TNT equivalent of 0.86 was achieved. This serves as a convenient method for studying the process of shock wave propa gation in a twophase mixture. The next step in the experimental investigations of shock waves on the explosion of capsules with liquid nitrogen was the modernization of the unit used for liq uid nitrogen injection. For this purpose, a special injec tor was developed that made it possible to introduce liquid nitrogen into water with a high rate. The experi mental facility consisted of a vertical vessel (a tube) 764 mm in height with the inner diameter of 53 mm. The external view of the facility is shown in Fig. 1. On the fixed cap of the tube, the system for liquid nitrogen injection is arranged; on the underside, the tube is closed by a solid bottom. In the upper part of the tube,
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Fig. 1. Schematic diagram of the experimental facility (without the optical cell): (1) working section, (2) liquid nitrogen injection system, (3) injector, (4, 5) pressure transducers, (6) pressure release system, (7) thermostating system, (8) analogtodigital converter, (9) computer.
Assembly 1 1 3 2 4
the safety valve is installed. The thickness of the tube wall is 8 mm, while that of the flanged cap and the bot tom is 20 cm. Pressure waves are recorded by two piezoelectric transducers located at the distances of 4 and 27 mm from the lower point of the injector. The transducers are installed flash with the inner wall of the tube. Signals from the transducers come through the analogtodigital converter to the computer; they are sampled with the frequency of 4 kHz. The injector serves to supply a jet of liquid nitrogen in water with a high rate. The volume of liquid nitro gen being injected was 28 mL. The schematic diagram of the injector is shown in Fig. 2. Here, unit 1 provides filling of the injector with liquid nitrogen. This proce dure is carried out as follows: the whole system is immersed into the Dewar vessel, and liquid nitrogen fills the entire volume, up to membrane 6, through annular slot 2. After that, the annular slot is hermeti cally closed by cone 3. A capillary 1 is provided through which liquid nitrogen contained in the cap sule is pressed out by helium at the pressure of up to 150 bar after the membrane is broken. Unit 2 com prises a nozzle for injecting fluid, which is closed by the membrane. After the procedure of filling is over, the injector outlet is closed with membrane 6 and washer 7. Then both the former and the latter are clamped together by means of grip nut 8. After that, the injector was attached hermetically above the vessel filled with water, while the liquid nitrogen injection system 2 was immersed below the water surface level at a depth of up to 10 cm, and helium was supplied through the capillary of injector 1 connected via the pipe to a gas cylinder in which pressure of up to 150 bar was created. When the pressure reached some critical value, the membrane was ruptured, and a dose of liq uid nitrogen was injected into water; the volume of the dose was equal to the volume of injector chamber 4. By means of selection of number of membranes and the inner diameter of the washer, it was possible to vary the pressure in the injector volume at which the mem brane was ruptured and liquid nitrogen was injected into water. Membranes were made of copper foil 0.1 mm thick.
Assembly 2
Experiments with Injection of a Jet of Liquid Nitrogen into Water
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Fig. 2. Schematic diagram of the injector: (1) capillary for helium supply, (2) annular slot, (3) coneshaped connec tor, (4) injector chamber, (5) tube connecting the injector chamber to the liquid nitrogen injection system, (6) mem brane, (7) washer, (8) grip nut.
In the course of experimental investigations, the pressure amplitude at boiling of liquid nitrogen in water was measured; the maximum amplitude was 53 bar when the washer with the inner diameter of 2.7 mm was used. In this case, the pressure rise rate was 567 bar/s (see Fig. 3.) Besides, there were carried out experiments at various degrees of filling of the volume of the working section with water (from 84 to 98%), and the amplitude of pressure jumps being developed was in the range between 8 and 53 bar. It can be seen from Fig. 4 that at such variation the pressure rise rate turns out to be proportional to the extent to which the THERMAL ENGINEERING
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working section is filled with water. This observation correlates qualitatively with experiments described in work [5], except that the levels of pressure and the val ues of derivatives are higher in experiments that have been carried out by the authors of the present paper, and this is due, respectively, not to the geometry of experiment but to physics of the process of formation of a gasliquid cavity inside the volume. An increase in volume and height of the chamber would make it pos sible to observe the processes that are more prolonged and occur at greater distances. In our experiments, the temperature of water in the working section varied; the measurements were carried out at the temperatures of 20 and 60°C, and, as this took place, the pressure rise rate varied too. The maximum amplitude of the pres sure jump at the temperature of 60°C was 17.4 bar. These experiments have been conducted at the largest inner diameter of the washer (4.5 mm), and they were comparative in nature (Fig. 5). Experiments on Visualization of the Physical Processes on Injection of Liquid Nitrogen into Water To carry out these experiments, we made a trans parent cell with the wall thickness of 20 mm, in the shape of a parallelepiped with external dimensions 150 × 150 mm and the height of 280 mm. This optical cell made it possible to work during longer periods and at larger distances from the point of the onset of the development of the process. The cell was filled with water by 90%. The injector nozzle was located at a dis tance of 50 mm from the water level. The process was recorded by means of a Phantom 7 video camera; highspeed video shooting was made with the fre quency of 10000 pictures/s. The stages of the process of video shooting are shown in the form of successive pictures in Fig. 6. Several stages have been revealed. In the first six pictures, the development of a bubble of gaseous nitrogen is shown; nitrogen was generated in the process of heating of the metal part of the inlet sys tem. The development of a bubble seen here is a clas sical vortex ring [13–15], which is being formed at the pulse gas injection into a gaseous or liquid medium. In the next pictures, it is shown how the expansion of the entire gas cavity occurs with time, with the simulta neous discharge of a jet of liquid nitrogen in the center of the gaseous core; this moves quickly in the area of lowered pressure and strikes the water surface in the lower part of the gaseous core. Then the process devel ops due to evaporation of liquid nitrogen caused by heat transfer from the ambient medium through the twophase mixture and gas space to liquid nitrogen. At the same time, freezingout of part of water occurs, with the formation of the ice phase; as this takes place, an expanding twophase gas plume is being formed. Figure 7 illustrates the dependence of the growth of a gas bubble at the level of the injector nozzle. These data are used at present for constructing the theory of THERMAL ENGINEERING
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Fig. 3. Pressure wave profile in the course of liquid nitro gen injection.
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Fig. 4. Pressure wave profile in the course of liquid nitro gen injection with various filling of the working section with water at the temperature of 20°C, (1) water occupies 98% of the working section volume, (2) water occupies 96% of the working section volume.
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Fig. 5. Pressure wave profile in the course of liquid nitro gen injection with filling of 96% of the working section vol ume with water at the temperature (1) 60°C and (2) 20°C.
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Fig. 6. Highspeed series photographs of the process of liq uid nitrogen injection in the closed vessel (10000 pic tures/s).
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Fig. 7. Variations in the radius of a bubble in the point of liquid nitrogen injection.
the process with due regard for the liquid–gas–solid body phase transitions in water and liquid nitrogen. Practical Implementation of the Obtained Results One of the key methods for the practical imple mentation of the process of fast boiling of liquid nitro gen might be the production of gas hydrates. The Mit sui Engineering & Shipbuilding Co. firm (Japan) already produced artificial gas hydrates in an effort to replace the transportation of natural and liquefied gas via pipelines and in the liquid form. Investigations car ried out by Norwegian scientists [16] showed that, when gas hydrates are transported at a distance of more than 1000 km, this method is economically more advantageous. The Mitsui Engineering & Shipbuild ing Co. firm transports 5 t of gas hydrates daily from
one of the terminals located in Japan, which is 20% of the total amount of fuel transported in the form of liq uefied natural gas. According to forecasts, the share of gas transported in the form of gas hydrates might reach no less than 20% of the total amount of gas being transported. The method that is being developed by the authors of the present paper can be implemented for produc ing gelatinous gas hydrate sludge using the scheme that is close to that used by Mitsui but with its considerable improvement. Besides, the physical processes of gas hydrate formation are essential for understanding the process of accidental blockage of pipelines when gas is transported. CONCLUSIONS In the present work, the following results have been obtained. (1) Highspeed video shooting of the hydrody namic processes occurring at the injection of a jet of cryogenic liquid into water has been made; as this took place, the structure and the stages of this process were established. It can be seen from the pictures that the intense turbulent mixing was formed on the outer edge of a vapor cylindrical bubble, and this fact must be taken into account when developing the mathematical model of the process. (2) The technology of the supply of liquid nitro gen using an original injector has been developed. RF patent no. 2507438 for the principle of its opera tion and construction has been obtained. (3) The experimental results show that pressure jumps required for the formation of gas hydrates were achieved. The maximum pressure obtained was 53 bar. In this case, the pressure rise rate was 567 bar/s. The results obtained will be used for the study of a new method of gas hydrate production based on the shock wave method. This study was supported by the government of the Russian Federation (grant no. 14.B25.31 for leading scientist Y. Kawazoe and the Kutateladze Institute of Thermophysics, Siberian Branch, Russian Academy of Sciences) and by the Russian Foundation for Basic Research (grant no. 140831620). REFERENCES 1. H. Clarke, R. Crookes, D. S. Wen, P. Dearman, and M. Aryes, “Development of a liquid nitrogenfuelled cryogenic engine,” TAE 7th Intern. Colloquium Fuels, 2009, pp. 649–656. 2. C. A. Ordonez, M. C. Plummer, and R.F. Reidy, “Cryogenic heat engines for powering zero emission vehicles,” ASME IMEC: 2001, PID_25620. 3. J. Dahlsveen, R. Kristoffersen, and L. Saetran, “Jet mixing of cryogen and water,” 2nd Intern. Symposium Turbulence and Shear Flow Phenomena, 2001, Vol. 2, pp. 329–334. THERMAL ENGINEERING
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EXPLOSIVE BOILING OF LIQUID NITROGEN 4. D. S. Wen, H. S. Chen, Y. L. Ding, and P. Dearman, “Liquid nitrogen injection into water: pressure build_up and heat transfer,” Cryogenics, 46, 740–748 (2006). 5. H. Clarke, A. MartinezHerasme, R. Crookes, and D. S. Wen, “Experimental study of jet structure and pressurization upon liquid nitrogen injection into water,” Int. J. Multiphase Flow, 36, No. 4, 940–949 (2010). 6. A. V. Meleshkin and I. V. Mezentsev, “The shockwave processes of action on a gasliquid mixture when pro ducing gas hydrates,” in Proc. AllRussia Youth Scien tific Conference “EREL2011,” Yakutsk, 2011, Vol. 1, pp. 115–116. 7. I. V. Mezentsev and A. V. Meleshkin, “The shockwave action on a gasliquid mixture when producing gas hydrates,” in Proc. AllRussia Youth Scientific Confer ence “The Current problems in Mathematics and Mechanics,” Tomsk, 2011, pp. 333–336. 8. V. E. Nakoryakov and V. E. Dontsov, “The shockwave method for producing gas hydrates,” RF Patent No. 2405740. Bull. Izobr., No. 34 (2008) 9. V. E. Nakoryakov, V. E. Dontsov, and A. A. Chernov, “Formation of gas hydrates in a gasfluid mixture fol lowing a shock wave,” Dokl. Ross. Akad. Nauk 411 (2), 190–193 (2006). 10. V. E. Dontsov and E. V. Dontsov , “Processes of disso lution and hydrate formation behind a shock wave in
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Translated by M. Virovlyanskii
