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Hydrodynamics of Apparatuses with Preformed Packing Bodies
Available online at www.sciencedirect.com
ScienceDirect Procedia Technology 12 (2014) 375 – 381
The 7th International Conference Interdisciplinarity in Engineering (INTER-ENG 2013)
Hydrodynamics of apparatuses with preformed packing bodies Zh. Serikulya,*, А. А. Volnenkob, E. Ya. Kenigc a b
M. Auezov South Kazakhstan State University, Shymkent 160000, Kazakhstan M. Auezov South Kazakhstan State University, Shymkent 160000, Kazakhstan c University of Paderborn, Paderborn 33098, Germany
Abstract The article describes the various types of preformed units of packed elements: cylindrical, sheet and ball. It is planned to do analyze of the hydrodynamic environment devices by the alteration of the gas flow rate and determination of the mode operation as well as researching of hydraulic resistance machines irrigated with regular packing depending on the vertical spacing between the elements of a packed and identifying opportunities to achieve regime simultaneous vortex. The equation for calculating the amount of the retained fluid for all the studied packed elements will be obtained as a result of the experimental data processing. © 2013 The Authors. Published by Elsevier B.V. © 2013 The Authors. Published by Elsevier Ltd. Selection and peer-review under responsibility of Department of Industrial Engineering and Management, Faculty of Selection and peer-review under responsibility of the Petru Maior University of Tirgu Mures. Engineering, “Petru Maior” University of Tîrgu Mureș. Keywords: preformed packing; interaction of the vortices; hydraulic resistance; amount of the retained fluid.
1. Introduction Packing columns find application in the modern chemical, petrochemical, oil, gas, and other industries for processes of chemisorptions, absorption, distillation, extraction, gas cooling and liquid and gas separation. Random packing of HY-PAK, CASCADE-RINGS, “Engchem” types and preformed packing of INTALOX, Sulzer, Koch, “Inzhehim”, Norton, “Vakupak”, “Glitch-Grid”, Mellapak, Mellapak Plus, Mellagrid types are widely
* Corresponding author. Tel.: +7-701-102-2422; E-mail address: [email protected]
2212-0173 © 2013 The Authors. Published by Elsevier Ltd. Selection and peer-review under responsibility of the Petru Maior University of Tirgu Mures. doi:10.1016/j.protcy.2013.12.502
376
Zh. Serikuly et al. / Procedia Technology 12 (2014) 375 – 381
used as contact devices in chemical apparatuses [1-6]. Preformed packing has several advantages over random packing: it has a lower hydraulic resistance that allows extension of the range of gas velocities. An entirely different principle of creating a regular gas-liquid layer is put in structures incorporated devices with a regular movable packing, in which the packing elements are strung on string with evenly spaced vertically and evenly spaced between the strings in the radial direction. This packing allows using the patterns of vortices interaction formed at the packing elements along the flow and across it to intensify the ongoing processes. Advantages of such devices are: simplicity of design, high rates of heat and mass transfer, low power consumption, and ability to treating contaminated gas and liquid flows. A characteristic feature of apparatuses with a preformed packing is their versatility. Having all the advantages of devices with movable packing, such as a simple design, a low pressure drop and a high efficiency, the apparatuses with a regular plate, tubular and spherical packing equally well be applied in absorption, distillation, condensation, contact cooling of gas and dust collection. The main application these devices finds in chemical engineering and processing, where large amounts of gas emissions and gas treatment processes require a large number of transfer units. The aim of the work is to study the hydrodynamic characteristics of apparatuses with a regular movable packing of cylindrical, lamellar and ball shapes, for obtaining the dependences for calculating the coefficients of hydraulic resistance, the number of retained fluid. Nomenclature
'Р L
hydraulic resistance, Pa; gas rate, m/s; irrigation densities, m3/m2h; vertical spacing between elements of packing; radial spacing between elements of packing; the size of the square plate packing, m; diameter ball packing, m; diameter of the cylindrical packing, m; dependence of fluid retention, m; packed height, m; gas density, kg/m3; coefficient of resistance taking account for the loss of pressure at the interaction of the vortexes in the vertical and radial directions, the gas friction on the surface of the packing cells and the film liquid; ε0 porosity of some packing; ReL Reynolds number; = L/3600 velocity of the liquid, m/s; ୪ coefficient of kinematic viscosity of the liquid, m2/s; dequ equivalent diameter of the packing, м; Ʌୠ coefficient characterizing the interaction of the vortices in the vertical direction; Ʌ୰ coefficient characterizing the interaction of the vortices in the radial direction; ɉ Strouhal number; ୩ parameter accounting for vortex formation, streamlined form elements and decrease of vortex rate; WG L tv tr b db dc h0 Н ρg ξL
2. Theory It is known [7] that the flow of solid bodies by gas flow (liquid) is accompanied by the formation and propagation of vortices. For spherical bodies, the arisen and broken down torroidal vortices are symmetrical. For prismatic bodies (cylinders, plates), the vortices appear alternately on one side of the body, then on the other, and their disruption occurs asymmetrically. By installing the streamlined bodies as elements packed in mass transfer apparatuses it can be achieved such an arrangement of elements in the vertical direction of the packing that the time when the vortices
Zh. Serikuly et al. / Procedia Technology 12 (2014) 375 – 381
377
moving with gas flow, come up to formed at the downstream elements coincides with the time of completion of the formation of vortices at the upstream of packed items. As a result there is arisen the simultaneous or common regime of vortex formation [8]. This regime is characterized by high energy consumption and, consequently, by high efficiency. While flowing the fluid along the row of solid bodies placed side by side, there exists the some critical distance between the streamlined bodies, the excess of which leads to the formation of vortices with a frequency that depends on the size of streamlined bodies. Arrangement of packing elements at a distance less than critical value leads to that the vortex shedding frequency is determined not by the size of streamlined bodies, but this frequency depends on the magnitude of the gap formed by the adjacent cross-sectional elements. The smaller the gap is, the greater is the frequency of vortex shedding and formation. Increase in the number of vortices, formed at small values of the gap, promotes that the higher efficiency can be reached by the lower power expenses. 3. Experimental section The experimental data of hydrodynamic and kinetic characteristics of the different types of preformed packing elements with symmetric and asymmetric vortex formation were obtained in a laboratory setting (Fig. 1). When operating the unit air flow charging by fan 1 was supplied to the columned device 7 with a diameter of 1.0 m and a height of 6.0 m. Passing through the work area with packing elements 8 the air flow resulted fluid coming through sprinklers 6 in a turbulent state and then was released into the atmosphere. Liquid droplets caught by the mist eliminator 5 through the tank gauging 4 run into the circulation tank 14. Air flow rate was regulated by choke 2 on the testimony of standard aperture with differential pressure gauge. Scrubbing liquid from the circulation tank 12 through the gate 3 was pumped 10 into the pressure tank 9 from where a low-pressure sprinklers got on irrigation. The flow of water was regulated by the gate 3 on the testimony of aperture complete with differential pressure gauge and the showing device DTS type. Fluid is heated of necessity by the coaxial heater 11. To measure the temperature of the incoming and outgoing air and liquid the installation was equipped with thermometers and psychrometers of Asman with divisions of 0.10 0C. The valve 13 is used to determine the amount of liquid held device. 4. Main results and discussion of the experimental data The gas, flowing through the layer of packing items with velocity of 1.0 to 2.5 m/s, does not violate the picture of fluid flow. The sprayed liquid flows over the strings of the packing in the form of film and in the form of large droplets and streams in the space among the packing units. In this regime that is called membrane-drip regime, the interaction between the gas and the liquid occurs on the surface of the films and on the surface of large droplets and streams. Hydraulic resistance is conditioned on the loss of the gas stream pressure while passing through a layer of irrigated packing items. The curves (Fig 2) the end of film-drip regime are characterized by fractures in the points A1, A2, A3. At the second regime that is called droplet regime, (WG = 2.5-4.0 m/s) the character of fluid flow changes. The growth rate of the gas flow leads to that the kinetic energy of the gas flow is sufficient for disrupting the flow of film on the surface of packing cells and for the formation of waves on the surface of the liquid film. As a consequence, the rate of fluid flow slows down, therefore the film thickness and the amount of the retained fluid increase. Fragmentation of liquid is carried out by the next mechanism: fluid film - streams - drops. Fragmentation of liquid is carried out by the next mechanism: fluid film - streams - drops. The work regime of the apparatus approaches to the most stable at WG|4.0 m/s. The uniformity of flow distribution is improved over the cross section of the apparatus; the turbulence of gas-liquid flow is increased due to the intensification of the formation process and vortex shedding behind the streamlined bodies. In the structure of gas-liquid layer is dominated by small drops. Fractures of the points B1… B3 on the curves 'РL = f(WG) (Fig. 2) indicate the upper limit of the drop regime existence. The increase in the density of irrigation shifts the end of drop mode to lower gas velocities. At the end of the drop regime the kinetic energy of the gas increases so that the liquid in the form of drip stream turns out to be driven out of the work area. The appearance of liquid droplets above the working area of the apparatus indicates the arrival of the next regime - the regime of splashing. This regime occurs when the gas flow rate is more than 4.0 m/s. On curves 'РL=f(WG) (Fig. 2) the regime of entrainment is shown in the areas В1С1, В2С2, В3С3, where the hydraulic resistance abruptly increases. Dynamic height of gas-liquid layer exceeds the height of the working area; there is an accumulation of fluid over the packing.
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a
1000
5
b
6
tb t r tr b
4 3
3
7 8
db
9
tb tr c
tr
dc
13
tb
2 tr
3
14
12 11 10
1
Hydraulic resistance dPL, Pa
b
- L=25 m3/m2h; tv/b=2; tr /b=2 - L=25 m3/m2h; tv/dc=2; tr /dc=2 - L=25 m3/m2h; tv/db=4.7; tr /db=2
500 400 300 200
B1
100 80 60 40 A1 20
?1 ?2 ?3 B2 B3
- sheet packing - tubular packing - ball packing
A2
A3 1
2
3
4
5
6
7 8 9 10
Gas rate WG, m/s Fig. 1. The diagram of the experimental setup
a - ball packing; b – sheet packing; c – tubular packing 1 fan; 2 choke; 3 gate; 4 tank gauging; 5 mist eliminator; 6 sprinkler; 7 columned device; 8 preformed movable packing; 9 pressure tank; 10 pump; 11 coaxial heater; 12, 14 circulation tanks; 13 valve.
Fig. 2. Dependence of hydraulic resistance on the gas rate of vehicles with a preformed moveable packing
Results of investigations of the hydraulic resistance 'РL of irrigated apparatuses with pipe, sheet and ball preformed packing depending on the vertical spacing between the packing elements tv/b indicate that for the studied types of packing, as well as for other geometric shapes of packing units [9,10], the simultaneous vortex formation can be achieved (Fig 3 (a)). Periodic regime is typical for units with a regular ball attachment, as well as halfperiodic and periodic are typical for regular tubes and plates. This means that in the studied range of irrigation densities (L from 25 to 100 m3/m2h) the fluid does not significantly affect the size of the vortexes. The rate of failure is determined by the gas phase. More fully effect of mechanism formation and interaction of the vortexes in the radial direction can be seen from the curves οܲ ൌ ݂ሺݐ ሻ(Fig 3 (b)). In the tested range tr from 1.5 to 4b a sharp decrease of hydraulic resistance of apparatuses with tubular, sheet and ball routine is observed at tr from 1.5 to 2b. Later, at tr from 2 to 4b the decline of οܲ is negligible. As for most devices with a preformed packing, the value tr=2b is critical. This is connected with different mechanisms of vortex formation. [8] The study results of fluid retention h0 depending on the design parameters tv and tr are shown in Fig. 4 (a) and (b). As you can see on the figures, the behavior of curves h0 while changing tv and tr is similar to the curves οܲ ൌ ݂ሺݐ௩ ǡ ݐ ሻ (Figs. 3 (a) and (b)). The increasing power of interacting vortexes in the simultaneous vortex regimes leads to increasing the fluid retention and mixing intensity, while the common-mode violation leads to a loss of power vortex, reducing their number and consequently, to a smaller amount of fluid retention. The amount of fluid retention h0 depending on a radial spacing tr (Fig. 4 (b) ) are decreased similarly to the hydraulic resistance (Fig 3 (b)) that is corresponding to the change in the porosity of the packing.
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Zh. Serikuly et al. / Procedia Technology 12 (2014) 375 – 381
a)
b) Fig. 3. (a) Dependence of hydraulic resistance on vertical spacing; (b) Dependence of hydraulic resistance on radial spacing
a)
b) Fig. 4. (a) Dependence amount of fluid retention on vertical spacing; (b) Dependence amount of fluid retention on radial spacing.
5. Calculations The loss of flow pressure spent on the formation and movement of the vortexes in the packing zone system, and the appropriate change of the gas flow direction, the gas friction on the surface of packing cells and the film liquid can be calculated by the following equation: 'PL
[L
2 H U gWG 2 tv 2H 0
(1)
Calculated relationship for the definition of coefficients Ɍ is obtained by processing of the experimental data
'РL:
for the apparatus with a tubular packing [L
0.24TbTr Re0.1 L
(2)
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Zh. Serikuly et al. / Procedia Technology 12 (2014) 375 – 381
with sheet packing
[L
0.27TbTr Re0.2 L
(3)
with ball packing
[L
0.677TbTr Re0.1 L
(4)
Reynolds number: Re L
U L dequ vl
(5)
ߠ - coefficient characterizing the interaction rate of the vortexes in the vertical direction: Tb
ª S § 4t S O · º 1¸ » 0.85 0.15sin « ¨ v ¹¼ ¬ 2 © mk
(6)
in equation (6) the Strouhal number for tubular elements ܵߣ ൌ Ͳǡͳͷ ; ݉ -parameter accounting for vortex formation, streamlined form elements and decrease of vortex rate:
mk ߠ
0.329 1 exp tv
(7)
- the coefficient, characterizing the interaction rate of the vortexes in the radial direction: Tr
tr O tr d
(8)
Impulsive elements located in the same row perpendicular to the flowing stream contribute the formation of vortices with scales O.There are two cases for discrete bodies arranged in a row perpendicular to the flowing stream. They are: by tr> 2d O=d; when tr<2d O=tr-d. For devices with plate and ball packing methods of calculation ξL are noted in [11]. For the irrigated devices the error of calculated data by equation (1) compared with the experiments (figures 3.4) were as follows: for the device with a tubular packingr 14%; with sheet r 15%; with ball r 14%. Obtained photographs of visual observation of the flow structure show that the liquid in the packing zone is distributed in the form of films on the packing cells, jets and droplets suspended among the space of packing units. Using the known relationship between the hydraulic resistance and the magnitude of the liquid column held by the gas flow, we obtain the formula for calculating the amount of the retained fluid h 0 as follows: H U gWG tv 2 Ul gH 02 2
h0
B [L
(9)
where experienced coefficient B = 0.65 - for the unit with a tubular packing, B = 0.52 - for the unit with sheet packing, B = 0.545 - for the unit with ball packing. Pointing error of the calculated data on the equation (9) with experimental data (Figures 4 (a) and (b)) was for the device: the tubular packing r10% with sheet packing r12% with ball packing r11%.
Zh. Serikuly et al. / Procedia Technology 12 (2014) 375 – 381
6. Conclusions The analysis of devices with different types of random and preformed packing elements has been carried out. The prospects of the usage of the apparatuses with a preformed movable packing are shown. The experimental studies have been based on analysis of hydrodynamic condition of apparatuses with a preformed movable packing cylindrical, lamellar and ball shape by the gas flow rate change, which indicates the presence of three regimes: film-drip, drip and entrainment. The most preferred regime is droplets regime of interaction phases as it shows the quality characteristics of the dispersed and continuous phases, the uniformity of their distribution and the degree of turbulence Results of the study of hydraulic resistance, the number of retained fluid of apparatuses with a regular movable packing cylindrical, sheet and ball shape, depending on the operational and design parameters have been used for deriving of the calculated dependences for the coefficients of hydraulic resistance determination, the number of retained fluid. References [1] Dmitrieva GB, Berengarten MG, Klyushenkova MI, Pushnov AS. Jeffektivnye konstrukcii strukturirovannyh nasadok dlja processov teplomassoobmena. (Effective design of structured packing for the processes of heat and mass transfer) J Himicheskoe i neftehimicheskoe mashinostroenie 2005; 8:15-17. [2] Kljujko VV, Holpanov LP. Issledovanie i raschet gidrodinamicheskih harakteristik reguljarnyh kontaktnyh ustrojstv massoobmennyh kolonn. (Research and calculation of the hydrodynamic characteristics of regular contact devices of mass transfer columns) J Himicheskoe i neftehimicheskoe mashinostroenie 2004; 5:10-12. [3] Farahov MI, Laptev AG, Mineev NG. Nasadochnye kontaktnye ustrojstva dlja massoobmennyh kolonn. (Packed contact devices for massexchange columns) J Himicheskaja tehnika 2009; 2: 4-5. [4] Senol Aynur, Dramur Umur. Performance test and desing considerations of a column packed with a new ceramic packing. J Chim. Actatruc 1995; 23: 145-155 [5] Laptev AG, Kudrjashov VN, Farahov MI. Vysokojeffektivnye nasadochnye jelementy dlja apparatov razdelenija. (high-performance vehicles packed items for sharing) Sb. trudov Jubilejnoj nauchno-prak. konf. posvjashhennoj 40-letiju OAO «Kazan'orgsintez», Kazan 2003; 272-304 [6] Farahov TM, Basharov MM, Shigapov IM. Gidravlicheskie harakteristiki novyh vysokojeffektivnyh nereguljarnyh teplomassoobmennyh nasadok. (Hydraulic characteristics of the new high-performance nozzles irregular heat and mass transfer) J Neftegazovoe delo 2011; 2:192207 [7] Balabekov OS, Petin VF. Zakonomernost vzaimodejstvija vihrej, voznikajushhih pri otryvnom obtekanii potokom gaza ili zhidkosti diskretno raspolozhennyh vdol nego tel. Svidetelstvo o nauchnom otkrytii №144. (The pattern of interaction between vortices arising from the separated flow stream of fluid, discretely along his body. Certificate of scientific discovery №144) Mezhdunarodnaja associacija avtorov nauchnyh otkrytij, Moscow 2000; 3. [8] Balabekov OS, Volnenko AA, Praliev S, Korganbaev BN, Balabekova MO, Viktorov SV. Zakonomernost' formirovanija parallel'no dvizhushhihsja vihrevyh struj pri techenii potoka gaza ili zhidkosti cherez sistemu poperek k nemu raspolozhennyh diskretnyh istochnikov. Svidetel'stvo o nauchnom otkrytii №269. (The pattern of formation of the vortex moving parallel streams in the flow stream of gas or liquid through the system across to him located discrete sources. Certificate of scientific discovery №269) Mezhdunarodnaja associacija avtorov nauchnyh otkrytij, Moscow 2004; 32-35. [9] Volnenko AA. Metodologija razrabotki i metodika rascheta apparatov s reguljarnoj podvizhnoj nasadkoj. (Development methodology and calculation method of mobile devices with a regular nozzle) J Vestnik NAN RK 1999; 3: 56-62. [10] Balabekov OS, Volnenko AA, Korganbaev BN. Zakonomernosti obtekanija sistemy reguljarno razmeshhennyh jelementov s razlichnym prostranstvennym raspolozheniem. (Patterns of flow systems are regularly posted items with different spatial arrangement) Tr.Mezhd. nauch. konf. «Jenergo- i resursosberegajushhie tehnologii i oborudovanie, jekologicheski bezopasnye proizvodstva». Ivanovo 2004; 1: 340-354. [11] Volnenko AA, Serikuly Zh, Balabekov OS, Husanov ZhE, Bazhirov TS. O edinom podhode k raschetu gidravlicheskogo soprotivlenija i kolichestva uderzhivaemoj zhidkosti v apparatah s reguljarnoj nasadkoj. (On a unified approach to the calculation of the hydraulic resistance and the amount of liquid held in the apparatus with a regular nozzle) J Himicheskij zhurnal Kazahstana 2012; 48-59.
381
ScienceDirect Procedia Technology 12 (2014) 375 – 381
The 7th International Conference Interdisciplinarity in Engineering (INTER-ENG 2013)
Hydrodynamics of apparatuses with preformed packing bodies Zh. Serikulya,*, А. А. Volnenkob, E. Ya. Kenigc a b
M. Auezov South Kazakhstan State University, Shymkent 160000, Kazakhstan M. Auezov South Kazakhstan State University, Shymkent 160000, Kazakhstan c University of Paderborn, Paderborn 33098, Germany
Abstract The article describes the various types of preformed units of packed elements: cylindrical, sheet and ball. It is planned to do analyze of the hydrodynamic environment devices by the alteration of the gas flow rate and determination of the mode operation as well as researching of hydraulic resistance machines irrigated with regular packing depending on the vertical spacing between the elements of a packed and identifying opportunities to achieve regime simultaneous vortex. The equation for calculating the amount of the retained fluid for all the studied packed elements will be obtained as a result of the experimental data processing. © 2013 The Authors. Published by Elsevier B.V. © 2013 The Authors. Published by Elsevier Ltd. Selection and peer-review under responsibility of Department of Industrial Engineering and Management, Faculty of Selection and peer-review under responsibility of the Petru Maior University of Tirgu Mures. Engineering, “Petru Maior” University of Tîrgu Mureș. Keywords: preformed packing; interaction of the vortices; hydraulic resistance; amount of the retained fluid.
1. Introduction Packing columns find application in the modern chemical, petrochemical, oil, gas, and other industries for processes of chemisorptions, absorption, distillation, extraction, gas cooling and liquid and gas separation. Random packing of HY-PAK, CASCADE-RINGS, “Engchem” types and preformed packing of INTALOX, Sulzer, Koch, “Inzhehim”, Norton, “Vakupak”, “Glitch-Grid”, Mellapak, Mellapak Plus, Mellagrid types are widely
* Corresponding author. Tel.: +7-701-102-2422; E-mail address: [email protected]
2212-0173 © 2013 The Authors. Published by Elsevier Ltd. Selection and peer-review under responsibility of the Petru Maior University of Tirgu Mures. doi:10.1016/j.protcy.2013.12.502
376
Zh. Serikuly et al. / Procedia Technology 12 (2014) 375 – 381
used as contact devices in chemical apparatuses [1-6]. Preformed packing has several advantages over random packing: it has a lower hydraulic resistance that allows extension of the range of gas velocities. An entirely different principle of creating a regular gas-liquid layer is put in structures incorporated devices with a regular movable packing, in which the packing elements are strung on string with evenly spaced vertically and evenly spaced between the strings in the radial direction. This packing allows using the patterns of vortices interaction formed at the packing elements along the flow and across it to intensify the ongoing processes. Advantages of such devices are: simplicity of design, high rates of heat and mass transfer, low power consumption, and ability to treating contaminated gas and liquid flows. A characteristic feature of apparatuses with a preformed packing is their versatility. Having all the advantages of devices with movable packing, such as a simple design, a low pressure drop and a high efficiency, the apparatuses with a regular plate, tubular and spherical packing equally well be applied in absorption, distillation, condensation, contact cooling of gas and dust collection. The main application these devices finds in chemical engineering and processing, where large amounts of gas emissions and gas treatment processes require a large number of transfer units. The aim of the work is to study the hydrodynamic characteristics of apparatuses with a regular movable packing of cylindrical, lamellar and ball shapes, for obtaining the dependences for calculating the coefficients of hydraulic resistance, the number of retained fluid. Nomenclature
'Р L
hydraulic resistance, Pa; gas rate, m/s; irrigation densities, m3/m2h; vertical spacing between elements of packing; radial spacing between elements of packing; the size of the square plate packing, m; diameter ball packing, m; diameter of the cylindrical packing, m; dependence of fluid retention, m; packed height, m; gas density, kg/m3; coefficient of resistance taking account for the loss of pressure at the interaction of the vortexes in the vertical and radial directions, the gas friction on the surface of the packing cells and the film liquid; ε0 porosity of some packing; ReL Reynolds number; = L/3600 velocity of the liquid, m/s; ୪ coefficient of kinematic viscosity of the liquid, m2/s; dequ equivalent diameter of the packing, м; Ʌୠ coefficient characterizing the interaction of the vortices in the vertical direction; Ʌ୰ coefficient characterizing the interaction of the vortices in the radial direction; ɉ Strouhal number; ୩ parameter accounting for vortex formation, streamlined form elements and decrease of vortex rate; WG L tv tr b db dc h0 Н ρg ξL
2. Theory It is known [7] that the flow of solid bodies by gas flow (liquid) is accompanied by the formation and propagation of vortices. For spherical bodies, the arisen and broken down torroidal vortices are symmetrical. For prismatic bodies (cylinders, plates), the vortices appear alternately on one side of the body, then on the other, and their disruption occurs asymmetrically. By installing the streamlined bodies as elements packed in mass transfer apparatuses it can be achieved such an arrangement of elements in the vertical direction of the packing that the time when the vortices
Zh. Serikuly et al. / Procedia Technology 12 (2014) 375 – 381
377
moving with gas flow, come up to formed at the downstream elements coincides with the time of completion of the formation of vortices at the upstream of packed items. As a result there is arisen the simultaneous or common regime of vortex formation [8]. This regime is characterized by high energy consumption and, consequently, by high efficiency. While flowing the fluid along the row of solid bodies placed side by side, there exists the some critical distance between the streamlined bodies, the excess of which leads to the formation of vortices with a frequency that depends on the size of streamlined bodies. Arrangement of packing elements at a distance less than critical value leads to that the vortex shedding frequency is determined not by the size of streamlined bodies, but this frequency depends on the magnitude of the gap formed by the adjacent cross-sectional elements. The smaller the gap is, the greater is the frequency of vortex shedding and formation. Increase in the number of vortices, formed at small values of the gap, promotes that the higher efficiency can be reached by the lower power expenses. 3. Experimental section The experimental data of hydrodynamic and kinetic characteristics of the different types of preformed packing elements with symmetric and asymmetric vortex formation were obtained in a laboratory setting (Fig. 1). When operating the unit air flow charging by fan 1 was supplied to the columned device 7 with a diameter of 1.0 m and a height of 6.0 m. Passing through the work area with packing elements 8 the air flow resulted fluid coming through sprinklers 6 in a turbulent state and then was released into the atmosphere. Liquid droplets caught by the mist eliminator 5 through the tank gauging 4 run into the circulation tank 14. Air flow rate was regulated by choke 2 on the testimony of standard aperture with differential pressure gauge. Scrubbing liquid from the circulation tank 12 through the gate 3 was pumped 10 into the pressure tank 9 from where a low-pressure sprinklers got on irrigation. The flow of water was regulated by the gate 3 on the testimony of aperture complete with differential pressure gauge and the showing device DTS type. Fluid is heated of necessity by the coaxial heater 11. To measure the temperature of the incoming and outgoing air and liquid the installation was equipped with thermometers and psychrometers of Asman with divisions of 0.10 0C. The valve 13 is used to determine the amount of liquid held device. 4. Main results and discussion of the experimental data The gas, flowing through the layer of packing items with velocity of 1.0 to 2.5 m/s, does not violate the picture of fluid flow. The sprayed liquid flows over the strings of the packing in the form of film and in the form of large droplets and streams in the space among the packing units. In this regime that is called membrane-drip regime, the interaction between the gas and the liquid occurs on the surface of the films and on the surface of large droplets and streams. Hydraulic resistance is conditioned on the loss of the gas stream pressure while passing through a layer of irrigated packing items. The curves (Fig 2) the end of film-drip regime are characterized by fractures in the points A1, A2, A3. At the second regime that is called droplet regime, (WG = 2.5-4.0 m/s) the character of fluid flow changes. The growth rate of the gas flow leads to that the kinetic energy of the gas flow is sufficient for disrupting the flow of film on the surface of packing cells and for the formation of waves on the surface of the liquid film. As a consequence, the rate of fluid flow slows down, therefore the film thickness and the amount of the retained fluid increase. Fragmentation of liquid is carried out by the next mechanism: fluid film - streams - drops. Fragmentation of liquid is carried out by the next mechanism: fluid film - streams - drops. The work regime of the apparatus approaches to the most stable at WG|4.0 m/s. The uniformity of flow distribution is improved over the cross section of the apparatus; the turbulence of gas-liquid flow is increased due to the intensification of the formation process and vortex shedding behind the streamlined bodies. In the structure of gas-liquid layer is dominated by small drops. Fractures of the points B1… B3 on the curves 'РL = f(WG) (Fig. 2) indicate the upper limit of the drop regime existence. The increase in the density of irrigation shifts the end of drop mode to lower gas velocities. At the end of the drop regime the kinetic energy of the gas increases so that the liquid in the form of drip stream turns out to be driven out of the work area. The appearance of liquid droplets above the working area of the apparatus indicates the arrival of the next regime - the regime of splashing. This regime occurs when the gas flow rate is more than 4.0 m/s. On curves 'РL=f(WG) (Fig. 2) the regime of entrainment is shown in the areas В1С1, В2С2, В3С3, where the hydraulic resistance abruptly increases. Dynamic height of gas-liquid layer exceeds the height of the working area; there is an accumulation of fluid over the packing.
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Zh. Serikuly et al. / Procedia Technology 12 (2014) 375 – 381
a
1000
5
b
6
tb t r tr b
4 3
3
7 8
db
9
tb tr c
tr
dc
13
tb
2 tr
3
14
12 11 10
1
Hydraulic resistance dPL, Pa
b
- L=25 m3/m2h; tv/b=2; tr /b=2 - L=25 m3/m2h; tv/dc=2; tr /dc=2 - L=25 m3/m2h; tv/db=4.7; tr /db=2
500 400 300 200
B1
100 80 60 40 A1 20
?1 ?2 ?3 B2 B3
- sheet packing - tubular packing - ball packing
A2
A3 1
2
3
4
5
6
7 8 9 10
Gas rate WG, m/s Fig. 1. The diagram of the experimental setup
a - ball packing; b – sheet packing; c – tubular packing 1 fan; 2 choke; 3 gate; 4 tank gauging; 5 mist eliminator; 6 sprinkler; 7 columned device; 8 preformed movable packing; 9 pressure tank; 10 pump; 11 coaxial heater; 12, 14 circulation tanks; 13 valve.
Fig. 2. Dependence of hydraulic resistance on the gas rate of vehicles with a preformed moveable packing
Results of investigations of the hydraulic resistance 'РL of irrigated apparatuses with pipe, sheet and ball preformed packing depending on the vertical spacing between the packing elements tv/b indicate that for the studied types of packing, as well as for other geometric shapes of packing units [9,10], the simultaneous vortex formation can be achieved (Fig 3 (a)). Periodic regime is typical for units with a regular ball attachment, as well as halfperiodic and periodic are typical for regular tubes and plates. This means that in the studied range of irrigation densities (L from 25 to 100 m3/m2h) the fluid does not significantly affect the size of the vortexes. The rate of failure is determined by the gas phase. More fully effect of mechanism formation and interaction of the vortexes in the radial direction can be seen from the curves οܲ ൌ ݂ሺݐ ሻ(Fig 3 (b)). In the tested range tr from 1.5 to 4b a sharp decrease of hydraulic resistance of apparatuses with tubular, sheet and ball routine is observed at tr from 1.5 to 2b. Later, at tr from 2 to 4b the decline of οܲ is negligible. As for most devices with a preformed packing, the value tr=2b is critical. This is connected with different mechanisms of vortex formation. [8] The study results of fluid retention h0 depending on the design parameters tv and tr are shown in Fig. 4 (a) and (b). As you can see on the figures, the behavior of curves h0 while changing tv and tr is similar to the curves οܲ ൌ ݂ሺݐ௩ ǡ ݐ ሻ (Figs. 3 (a) and (b)). The increasing power of interacting vortexes in the simultaneous vortex regimes leads to increasing the fluid retention and mixing intensity, while the common-mode violation leads to a loss of power vortex, reducing their number and consequently, to a smaller amount of fluid retention. The amount of fluid retention h0 depending on a radial spacing tr (Fig. 4 (b) ) are decreased similarly to the hydraulic resistance (Fig 3 (b)) that is corresponding to the change in the porosity of the packing.
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a)
b) Fig. 3. (a) Dependence of hydraulic resistance on vertical spacing; (b) Dependence of hydraulic resistance on radial spacing
a)
b) Fig. 4. (a) Dependence amount of fluid retention on vertical spacing; (b) Dependence amount of fluid retention on radial spacing.
5. Calculations The loss of flow pressure spent on the formation and movement of the vortexes in the packing zone system, and the appropriate change of the gas flow direction, the gas friction on the surface of packing cells and the film liquid can be calculated by the following equation: 'PL
[L
2 H U gWG 2 tv 2H 0
(1)
Calculated relationship for the definition of coefficients Ɍ is obtained by processing of the experimental data
'РL:
for the apparatus with a tubular packing [L
0.24TbTr Re0.1 L
(2)
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with sheet packing
[L
0.27TbTr Re0.2 L
(3)
with ball packing
[L
0.677TbTr Re0.1 L
(4)
Reynolds number: Re L
U L dequ vl
(5)
ߠ - coefficient characterizing the interaction rate of the vortexes in the vertical direction: Tb
ª S § 4t S O · º 1¸ » 0.85 0.15sin « ¨ v ¹¼ ¬ 2 © mk
(6)
in equation (6) the Strouhal number for tubular elements ܵߣ ൌ Ͳǡͳͷ ; ݉ -parameter accounting for vortex formation, streamlined form elements and decrease of vortex rate:
mk ߠ
0.329 1 exp tv
(7)
- the coefficient, characterizing the interaction rate of the vortexes in the radial direction: Tr
tr O tr d
(8)
Impulsive elements located in the same row perpendicular to the flowing stream contribute the formation of vortices with scales O.There are two cases for discrete bodies arranged in a row perpendicular to the flowing stream. They are: by tr> 2d O=d; when tr<2d O=tr-d. For devices with plate and ball packing methods of calculation ξL are noted in [11]. For the irrigated devices the error of calculated data by equation (1) compared with the experiments (figures 3.4) were as follows: for the device with a tubular packingr 14%; with sheet r 15%; with ball r 14%. Obtained photographs of visual observation of the flow structure show that the liquid in the packing zone is distributed in the form of films on the packing cells, jets and droplets suspended among the space of packing units. Using the known relationship between the hydraulic resistance and the magnitude of the liquid column held by the gas flow, we obtain the formula for calculating the amount of the retained fluid h 0 as follows: H U gWG tv 2 Ul gH 02 2
h0
B [L
(9)
where experienced coefficient B = 0.65 - for the unit with a tubular packing, B = 0.52 - for the unit with sheet packing, B = 0.545 - for the unit with ball packing. Pointing error of the calculated data on the equation (9) with experimental data (Figures 4 (a) and (b)) was for the device: the tubular packing r10% with sheet packing r12% with ball packing r11%.
Zh. Serikuly et al. / Procedia Technology 12 (2014) 375 – 381
6. Conclusions The analysis of devices with different types of random and preformed packing elements has been carried out. The prospects of the usage of the apparatuses with a preformed movable packing are shown. The experimental studies have been based on analysis of hydrodynamic condition of apparatuses with a preformed movable packing cylindrical, lamellar and ball shape by the gas flow rate change, which indicates the presence of three regimes: film-drip, drip and entrainment. The most preferred regime is droplets regime of interaction phases as it shows the quality characteristics of the dispersed and continuous phases, the uniformity of their distribution and the degree of turbulence Results of the study of hydraulic resistance, the number of retained fluid of apparatuses with a regular movable packing cylindrical, sheet and ball shape, depending on the operational and design parameters have been used for deriving of the calculated dependences for the coefficients of hydraulic resistance determination, the number of retained fluid. References [1] Dmitrieva GB, Berengarten MG, Klyushenkova MI, Pushnov AS. Jeffektivnye konstrukcii strukturirovannyh nasadok dlja processov teplomassoobmena. (Effective design of structured packing for the processes of heat and mass transfer) J Himicheskoe i neftehimicheskoe mashinostroenie 2005; 8:15-17. [2] Kljujko VV, Holpanov LP. Issledovanie i raschet gidrodinamicheskih harakteristik reguljarnyh kontaktnyh ustrojstv massoobmennyh kolonn. (Research and calculation of the hydrodynamic characteristics of regular contact devices of mass transfer columns) J Himicheskoe i neftehimicheskoe mashinostroenie 2004; 5:10-12. [3] Farahov MI, Laptev AG, Mineev NG. Nasadochnye kontaktnye ustrojstva dlja massoobmennyh kolonn. (Packed contact devices for massexchange columns) J Himicheskaja tehnika 2009; 2: 4-5. [4] Senol Aynur, Dramur Umur. Performance test and desing considerations of a column packed with a new ceramic packing. J Chim. Actatruc 1995; 23: 145-155 [5] Laptev AG, Kudrjashov VN, Farahov MI. Vysokojeffektivnye nasadochnye jelementy dlja apparatov razdelenija. (high-performance vehicles packed items for sharing) Sb. trudov Jubilejnoj nauchno-prak. konf. posvjashhennoj 40-letiju OAO «Kazan'orgsintez», Kazan 2003; 272-304 [6] Farahov TM, Basharov MM, Shigapov IM. Gidravlicheskie harakteristiki novyh vysokojeffektivnyh nereguljarnyh teplomassoobmennyh nasadok. (Hydraulic characteristics of the new high-performance nozzles irregular heat and mass transfer) J Neftegazovoe delo 2011; 2:192207 [7] Balabekov OS, Petin VF. Zakonomernost vzaimodejstvija vihrej, voznikajushhih pri otryvnom obtekanii potokom gaza ili zhidkosti diskretno raspolozhennyh vdol nego tel. Svidetelstvo o nauchnom otkrytii №144. (The pattern of interaction between vortices arising from the separated flow stream of fluid, discretely along his body. Certificate of scientific discovery №144) Mezhdunarodnaja associacija avtorov nauchnyh otkrytij, Moscow 2000; 3. [8] Balabekov OS, Volnenko AA, Praliev S, Korganbaev BN, Balabekova MO, Viktorov SV. Zakonomernost' formirovanija parallel'no dvizhushhihsja vihrevyh struj pri techenii potoka gaza ili zhidkosti cherez sistemu poperek k nemu raspolozhennyh diskretnyh istochnikov. Svidetel'stvo o nauchnom otkrytii №269. (The pattern of formation of the vortex moving parallel streams in the flow stream of gas or liquid through the system across to him located discrete sources. Certificate of scientific discovery №269) Mezhdunarodnaja associacija avtorov nauchnyh otkrytij, Moscow 2004; 32-35. [9] Volnenko AA. Metodologija razrabotki i metodika rascheta apparatov s reguljarnoj podvizhnoj nasadkoj. (Development methodology and calculation method of mobile devices with a regular nozzle) J Vestnik NAN RK 1999; 3: 56-62. [10] Balabekov OS, Volnenko AA, Korganbaev BN. Zakonomernosti obtekanija sistemy reguljarno razmeshhennyh jelementov s razlichnym prostranstvennym raspolozheniem. (Patterns of flow systems are regularly posted items with different spatial arrangement) Tr.Mezhd. nauch. konf. «Jenergo- i resursosberegajushhie tehnologii i oborudovanie, jekologicheski bezopasnye proizvodstva». Ivanovo 2004; 1: 340-354. [11] Volnenko AA, Serikuly Zh, Balabekov OS, Husanov ZhE, Bazhirov TS. O edinom podhode k raschetu gidravlicheskogo soprotivlenija i kolichestva uderzhivaemoj zhidkosti v apparatah s reguljarnoj nasadkoj. (On a unified approach to the calculation of the hydraulic resistance and the amount of liquid held in the apparatus with a regular nozzle) J Himicheskij zhurnal Kazahstana 2012; 48-59.
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