The purpose of this work is investigation of changes in hydrodynamic parameters (absolute pressure, mass flow rates of solution and secondary steam, secondary steam velocity, solution irrigation density, and pressure loss) along the length of the heat exchange tube of a vertical falling film evaporator. The obtained data of the distribution of hydrodynamic parameters were used in the design of falling film evaporators. © 2021 Author(s)

Gushshamova, V. N.

Khomyakov, A. P.

Khomyakova, T. V.

Mordanov, S. V.

Institutional repository of Ural Federal University named after the first President of Russia B.N.Yeltsin

AIP Conference Proceedings 2388, 020006 (2021); https://doi.org/10.1063/5.0068408 2388, 020006© 2021 Author(s).Investigation of hydrodynamic parametersdistribution in heat exchange tubes of fallingfilm evaporatorCite as: AIP Conference Proceedings 2388, 020006 (2021); https://doi.org/10.1063/5.0068408Published Online: 19 November 2021V. N. Gushshamova, A. P. Khomyakov, S. V. Mordanov, et al.ARTICLES YOU MAY BE INTERESTED INLateral flow test strips for mercury ions detection based on combination of oligonucleotide-modified gold nanoparticles and chelation by glutathioneAIP Conference Proceedings 2388, 020001 (2021); https://doi.org/10.1063/5.0069419New silver nanocomposites based on copolymers of azanorbornenes with N-vinylpyrrolidoneAIP Conference Proceedings 2388, 020005 (2021); https://doi.org/10.1063/5.0068384Influence of the knotweed (Reynoutria japonica Houtt.) extract on the growth of Fusarium sp.AIP Conference Proceedings 2388, 020008 (2021); https://doi.org/10.1063/5.0069186Investigation of Hydrodynamic Parameters Distribution in Heat Exchange Tubes of Falling Film EvaporatorV.N. Gushshamova ), A.P. Khomyakov, S.V. Mordanov, T.V. Khomyakova Ural Federal University, 19, Mira str., 620002, Yekaterinburg, Russia. a)Corresponding author: 89126634949@yandex.ruAbstract.  The purpose of this work is investigation of changes in hydrodynamic parameters (absolute pressure, mass flow rates of solution and secondary steam, secondary steam velocity, solution irrigation density, and pressure loss) along the length of the heat exchange tube of a vertical falling film evaporator. The obtained data of the distribution of hydrodynamic parameters were used in the design of falling film evaporators. INTRODUCTION Falling film evaporators are widely used in various industries. This application is due to the high intensity of heat exchange, high performance with relatively small volumes of the apparatus itself and insignificant production area [1-3]. Experimental studies of the hydrodynamics of the irrigation liquid film in horizontal film evaporators are presented in literature [4, 5]. The purpose of this work is investigation of changes in hydrodynamic parameters (absolute pressure, mass flow rates of solution and secondary steam, secondary steam velocity, solution irrigation density, and pressure loss) along the length of the heat exchange tube of a vertical falling film evaporator. DESCRIPTION OF THE INVESTIGATION Study of hydrodynamics was carried out by means of a mathematical numerical simulation for the falling film evaporator, equipped with heat exchange tube (with diameter 38 2 mm and length L=7 m). Data were obtained from the length of the heat exchange tube with step L=0.1 m. For the numerical simulation, we used the mathematical model based on the momentum conservation equation in terms of the pressure changes due to the steam and liquid film frictional and dynamical pressure changes, local hydraulic resistances, gravitation, and steam and liquid physical properties on the saturation line changing with the absolute pressure decreasing. The physical properties of the solution and steam were described using experimental data approximation equations with the approximation error of no more than 2-3 %. The solution thermal depressions and boiling temperatures were calculated using the ebullioscopic method. Main technological parameters of the device operation: 1. Volume flow rate of the initial solution: 50 l/h, 100 l/h, 150 l/h;2. Effective temperature difference – 15 ° ;3. Temperature of the initial solution – 70 ° ;4. Boiling point of the initial solution – 70 ° ;5. The heat transfer coefficient was assumed to be constant over the entire length of the heat exchange tube, equalto 2000 W/(m2·K). RESULTS OF THE STUDY The absolute pressure changes along the length of the heat exchange tube of the falling film evaporator at volume flow rates of the initial solution 50 l/h, 100 l/h, 150 l/h are shown in figure 1. At volume flow rates of 50 l/h and 100 l/h, the absolute pressure varies along the length of the tube from 31000 Pa to 28589 Pa and from 31000 Pa to 27532 Pa, respectively. When the volume flow rate of the initial solution increases to 150 l/h, the absolute pressure changes from 31000 Pa to 26519 Pa along the length of the heat exchange tube. Modern Synthetic Methodologies for Creating Drugs and Functional Materials (MOSM2020)AIP Conf. Proc. 2388, 020006-1–020006-4; https://doi.org/10.1063/5.0068408Published by AIP Publishing. 978-0-7354-4142-2/$30.00020006-1 FIGURE 1. Distributions in absolute pressure in the tube space of the falling film evaporator  It is established that an increase in the volume flow rate of the initial solution leads to an increase in hydraulic resistance. Figure 2 shows distributions of the mass flow rates of the solution along the heat exchange tube length. It is found that for all the considered volume flow rates of the initial solution, the amount of solution along the length of the tube decreases and changes almost linearly. Distributions of the mass flow rates of secondary steam along the heat exchange tube length at different flow rates of the initial solution are shown in figure 3. It is established that an increase in the volume flow rate of the initial solution leads to an increase in the mass flow rate of secondary steam. The change is linear for the mass flow rate of secondary steam along the heat exchange tube length.   FIGURE 2. Distributions of the mass flow rate of the solution in the tube space of the film evaporator  The distribution of the volume density of irrigation along the length of the heat exchange tube of the falling film evaporator is shown in figure 4. The volume density of irrigation at the volume flow rate of the initial solution of 50 l/h varies from 0.00013 m3/(s·m) to 0.00001 m3/(s·m). When the volume flow rate of the initial solution is 100 l/h, it changes from 0.00026 m3/(s·m) to 0.00017 m3/(s·m). When the volume flow rate of the initial solution is 150 l/h, it changes from 0.0004 m3/(s·m) to 0.00023 m3/(s·m). The change in the volume density of irrigation with an increase in the volume flow of the initial solution is almost linear.  Figure 5 shows the distribution of the secondary steam velocity along the length of the heat exchange tube. At the following volume flow rates of the initial solution, the velocity of secondary steam at the outlet of the heat exchange tube reaches the values:  for flow rate 50 l/h – 56 m/s;  for flow rate 100 l/h – 62.7 m/s;  for flow rate 150 l/h – 67.2 m/s.  0,00010,00510,01010,01510,02010,02510,03010,03510,04010,04510 1 2 3 4 5 6 7Mass flow rate of the solution, kg/sLength of heat exchange tube, m50 l/h100 l/h150 l/h200002200024000260002800030000320000 1 2 3 4 5 6 7Absolute pressure, PALength of heat exchange tube, m50 l/h100 l/h150 l/h020006-2It was found that an increase in the volume flow rate of the initial solution leads to an increase in velocity of secondary steam.                FIGURE 3. Distributions of the mass flow rate of secondary steam in the tube space of the film evaporator FIGURE 4. Distributions of volume density irrigation along the length of the heat exchange tube  Distributions of pressure losses along the length of the tube for each test mode of the initial solution are shown in figure 6. When the initial solution is consumed at 50 l/h, the pressure loss along the length of the heat exchange tube varies from 134 Pa to 2411 Pa. At the flow rate of the initial solution of 100 l/h, the pressure loss along the length of the heat exchange tube varies from 297 Pa to 3468 Pa. At the flow rate of the initial solution of 150 l/h, the pressure loss along the length of the heat exchange tube varies from 431 Pa to 4481 Pa. The local hydraulic resistance at the inlet to the tube explains the pressure change in the initial section of the heat exchange tube.  Pressure losses along the length of the heat exchange tube occur due to changes in the dynamical pressure, due to the friction of the solution film against the tube wall, and due to the friction of steam against the solution film. The graph shows that an increase in the volume flow of the initial solution leads to an increase in the values of pressure losses along the length of the heat exchange tube.      00,000050,00010,000150,00020,000250,00030,000350,00040,000450 1 2 3 4 5 6 7The volume density of irrigation, m^3/(s*m)Length of heat exchange tube, m50 l/h100 l/h150 l/h00,0020,0040,0060,0080,010,0120 1 2 3 4 5 6 7 8Mass flow rate of  secondary steam, kg/sLength of heat exchange tube, m50 l/h100 l/h150 l/h020006-3FIGURE 5. Distributions of velocities of secondary steam along the length of the heat exchange tube FIGURE 6. Distributions of hydraulic resistance along the length of the heat exchange tube  CONCLUSION In our research, we have studied changes of the hydrodynamic parameters of a two-phase flow along the length of the heat exchange tube of the falling film evaporator. The research was carried out using mathematical numerical modeling. Distributions at the length of the heat exchange tube are obtained: absolute pressure, secondary steam velocity, liquid phase irrigation density, mass flow rates of the solution and secondary steam, and pressure losses. The obtained data of the distribution of hydrodynamic parameters were used in the design of falling film evaporators. REFERENCES 1. F.C. Standiford, Chemical Engineering Progress 70, 157 (1974). 2. J.G. Moore, Chemical Engineering Progress 59, 87-92 (1963). 3. J.R. Sinek, E.H. Young, Chemical Engineering Progress 58, 74-80 (1962). 4. Q. Wang, M. Li, W. Xu, L. Yao, X. Li, D. Su, P. Wang, International Journal of Heat and Mass Transfer 163, (2020). 5. E. Aursanda and T. Ytrehus, International Journal of Multiphase Flow 116, 67-79 (2019).  010203040506070800 1 2 3 4 5 6 7 8Velocity of secondaty steam, m/sLength of heat exchange tube, m50 l/h100 l/h150 l/h05001000150020002500300035004000450050000 1 2 3 4 5 6 7Pressure losses, PaLength of heat exchange tube, m50 l/h100 l/h150 l/h020006-4

Investigation of Hydrodynamic Parameters Distribution in Heat Exchange Tubes of Falling Film Evaporator

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Investigation of Hydrodynamic Parameters Distribution in Heat Exchange Tubes of Falling Film Evaporator

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