A simulation design method for a cryogenic liquid heater

Abstract

The present invention provides a simulation design method for a cryogenic liquid heater, which relates to the field of cryogenic liquid heating. In the simulation design method for a cryogenic liquid heater of the present invention, in the cylindrical coordinate system, a mathematical model is established during the flow heat transfer process of gas and water vapor. Based on the hybrid difference scheme, the partial differential equation group in the mathematical model is discretized, and a solution method for the discretized partial differential equation group is established, so as to obtain the temperature value of the upper edge point of the low-emission pipe orifice and the temperature value of the lower edge point of the discharge pipe orifice. Then, based on the preset upper edge temperature constraint of the pipe orifice and the lower edge temperature constraint of the discharge pipe orifice, the preset values of the position of the discharge pipe and the inner diameter of the heating pipe are adjusted, so as to obtain the theoretical results of the inner diameter of the heating pipe and the position of the discharge pipe. By this method, the R & D time of the cryogenic liquid heater is shortened, the test cost during the R & D process is reduced, and the R & D efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of cryogenic liquid heating, and specifically relates to a simulation design method for a cryogenic liquid heater. Background Art

[0002] An air separation unit generally refers to a device for separating various air components in a chemical plant, separating gases such as nitrogen, cryogenic gas, and argon from the air. During the overhaul or accident search process of the air separation unit, it is necessary to discharge the cryogenic liquids in the air separation unit in advance, such as liquid nitrogen, liquid argon, and liquid air. However, the temperature of the above cryogenic liquids is usually lower than -180°C and needs to be heated into normal temperature gases for high-altitude discharge.

[0003] In the existing heating technologies, there is a device system that uses atmospheric pressure steam to contact and exchange heat with cryogenic liquids, enabling the cryogenic liquids to be gasified and discharged. Reference can be made to the applied invention patent "A Cryogenic Liquid Heating and Discharging Device and Its Use Method" (Publication No.: CN113432035A). This patent discloses the specific content of the device system and its core equipment, but does not explain the size and opening position of the core component - the heating tube during the actual working process.

[0004] In view of the complex material system and heat transfer principle involved in the heating tube, the conventional design method of obtaining empirical formulas based on a large number of experiments not only has high costs, long time, but also has a narrow application range. Therefore, there is an urgent need for a simulation design method for a cryogenic liquid heater to obtain relevant design parameters of the cryogenic liquid heater. Summary of the Invention

[0005] (1) Technical Problems to be Solved

[0006] Aiming at the deficiencies of the existing technology, the present invention provides a simulation design method for a cryogenic liquid heater, which obtains relevant design parameters of the cryogenic liquid heater by reasonably simplifying the cryogenic liquid heater, establishing a mathematical model, and using a reasonable numerical solution method.

[0007] (2) Technical Solutions

[0008] To achieve the above objectives, the present invention is realized through the following technical solutions:

[0009] The present invention provides a simulation design method for a cryogenic liquid heater. The cryogenic liquid heater includes: a heating pipe, a discharge pipe, a main steam pipe, a liquid distributor, and a main liquid collecting pipe; the main liquid collecting pipe is connected to the upper part of the vertically arranged heating pipe and is located above the liquid distributor; the periphery of the liquid distributor is tightly connected to the inner wall of the upper part of the heating pipe; the main steam pipe is connected and extends into the lower part of the heating pipe; one end of the discharge pipe is connected to the other side of the middle part of the heating pipe, and one end communicates with the outside air upward and is located below the liquid distributor;

[0010] Wherein, R represents the radius of the heating pipe; R0 represents the radius of the discharge pipe; H1 represents the height from the tip of the solid cone nozzle of the liquid distributor to the center of the discharge pipe orifice; H2 represents the height from the center of the discharge pipe to the upper edge of the main steam pipe;

[0011] The simulation design method includes:

[0012] S1. Obtain the preset values of R, R0, H1, H2, T, U, V, W, p and initialize the grid;

[0013] Wherein, T represents the temperature inside the heating pipe, U represents the radial velocity of the gas inside the heating pipe, V represents the circumferential velocity of the gas inside the heating pipe, W represents the axial velocity of the gas inside the heating pipe, and p represents the gas pressure inside the heating pipe; the construction process of the initialized grid includes: performing grid division on the heating pipe based on an adaptive grid to obtain the initialized grid;

[0014] S2. Based on the preset values of R, R0, H1, H2, T, U, V, W, p and the pre-constructed numerical calculation iteration equation, obtain the equation solutions corresponding to each grid node in the initialized grid;

[0015] Wherein, the equation solutions include the numerical values of T, U, V, W, p; the construction process of the numerical calculation iteration equation includes: discretizing the partial differential equation group in the mathematical model based on a mixed difference format, and taking the discretized partial differential equation group as the numerical calculation iteration equation; the mathematical model includes: the sedimentation equation group of cryogenic droplets, and the partial differential equation group in the cylindrical coordinate system during the mass transfer - heat transfer - gas flow process of cryogenic droplets and water vapor;

[0016] S3. Continuously divide the initialized grid based on the equation solutions and the adaptive grid to obtain the completed divided grid, which is used as the first grid;

[0017] Wherein, the equation solutions corresponding to the grid nodes in the first grid satisfy the adaptive grid division rule;

[0018] S4. Determine the temperature value T1 of the upper edge point of the low-emission pipe orifice and the temperature value T2 of the lower edge point of the emission pipe orifice based on the coordinates of the first grid, the upper edge point of the emission pipe orifice, and the lower edge point of the emission pipe orifice;

[0019] S5. Judge whether T1 meets the temperature constraint of the upper edge of the emission pipe orifice and whether T2 meets the temperature constraint of the lower edge of the emission pipe orifice. If so, use the initial value of H1 as the target value of H1 and the initial value of H2 as the target value of H2; if not, adjust the initial values of H1 and H2, repeat steps S2 - S4, update T1 and T2 until the updated T1 meets the temperature constraint of the upper edge of the emission pipe orifice and the updated T2 meets the temperature constraint of the lower edge of the emission pipe orifice, and use the adjusted H1 and H2 as the target values of H1 and H2 respectively;

[0020] Among them, the temperature constraint of the upper edge of the emission pipe orifice is -0.05 ≤ T1 + 50 ≤ 0.05, and the temperature constraint of the lower edge of the emission pipe orifice is -0.05 ≤ T2 - 25 ≤ 0.05.

[0021] Optionally, the sedimentation equations in S2 include:

[0022]

[0023]

[0024]

[0025] The boundary conditions are: z = 0, V d = V d 0, d p = d p 0, ρ p = ρ p 0;

[0026] Among them, V d represents the sedimentation velocity of low-temperature droplets; z represents the axial coordinate of the spatial point, with the downward direction being positive; W represents the gas axial velocity; ρ p represents the density of low-temperature droplets; ρ represents the gas density; d p represents the droplet diameter; g represents the acceleration due to gravity; C D represents the drag coefficient; p represents the gas pressure; k s represents the heat transfer coefficient; T represents the temperature; n represents the number of low-temperature droplets; represents the boiling point of the low-temperature liquid; represents the heat of vaporization of the low-temperature droplets; represents the heat of vaporization of water; represents the heat of fusion of water; represents the density of solid water; represents the density of the liquid low-temperature liquid;

[0027] Optionally, the partial differential equations in cylindrical coordinates in S2 include: continuity equation, volume expansion rate equation, momentum equation, and energy equation;

[0028] The continuity equation:

[0029] The volume expansion rate equation:

[0030] The momentum equation:

[0031]

[0032] The energy equation:

[0033] The boundary conditions are:

[0034] z = 0, U = 0, V = 0, W = 0, T = T0, and δ = 0;

[0035] z = H, H = H1 + H2, U = 0, V = 0, W = W w , T = T w ;

[0036] r = R, except 3π / 2 < θ < 2π), U = 0, V = 0, W = 0,

[0037] where r represents the cylindrical radial coordinate of a spatial point in the cylindrical coordinate system; θ represents the circular cross-section angular coordinate of a spatial point in the cylindrical coordinate system; U represents the gas radial velocity; V represents the gas circumferential velocity; n represents the number of cryogenic droplets; C p represents the isobaric heat capacity of the gas; λ represents the thermal conductivity of the gas; δ represents the gas volume expansion rate; p represents the gas pressure; μ represents the gas viscosity.

[0038] Optionally, the judgment criterion for the hybrid difference format in S2 is:

[0039] For the momentum equation

[0040] For the energy equation

[0041] where it is judged whether it satisfies If \(s = r,\theta,z\), then rewrite the momentum equation and energy equation in the corresponding coordinate direction into the upwind format;

[0042] If not, then rewrite the momentum equation and energy equation in the corresponding coordinate direction into the central difference format.

[0043] Optionally, in S3, based on the equation solution and the adaptive grid, continuously refine the initialized grid to obtain a refined grid, which is used as the first grid, including:

[0044] S301. Based on the equation solution and the adaptive grid, refine the initialized grid to obtain a refined grid;

[0045] S302. Determine whether the equation solution corresponding to the grid nodes in the refined grid satisfies the adaptive grid refinement rule; if so, use the refined grid as the first grid; if not, go to S303;

[0046] S303. Determine the existing grid nodes around the newly added grid nodes in the refined grid, average the equation solutions of the existing grid nodes, and use the averaged equation solution as the equation solution of the newly added grid node;

[0047] S304. Replace the preset values of \(T\), \(U\), \(V\), \(W\), \(p\) with the equation solution of the newly added grid node, and go to S2.

[0048] Optionally, in S5, determine whether T1 satisfies the temperature constraint at the upper edge of the discharge pipe orifice and whether T2 satisfies the temperature constraint at the lower edge of the discharge pipe orifice; if so, use the initial value of H1 as the target value of H1 and the initial value of H2 as the target value of H2; if not, adjust the initial values of H1 and H2, repeat steps S2 - S4 to update T1 and T2 until the updated T1 satisfies the temperature constraint at the upper edge of the discharge pipe orifice and the updated T2 satisfies the temperature constraint at the lower edge of the discharge pipe orifice, and use the adjusted H1 and H2 as the target values of H1 and H2 respectively, including:

[0049] S501. Determine whether T1 satisfies the temperature constraint at the upper edge of the discharge pipe orifice; if it satisfies, use the parameter value of H1 as the target value of H1 and go to S502; if T1 does not satisfy the temperature constraint at the upper edge of the discharge pipe orifice, continuously adjust T1 based on the first preset method until the adjusted T1 satisfies the temperature constraint at the upper edge of the discharge pipe orifice;

[0050] Wherein, the first preset method is: when \(T1 + 50>0.05\), decrease the value of H1; when \(T1 + 50 < - 0.05\), increase the value of H1; then, replace the initial value of H1 with the adjusted value of H1 and go to S2;

[0051] S502. Determine whether T2 meets the temperature constraint at the lower edge of the discharge pipe orifice. If so, use the initial value of H2 as the target value of H2; if not, continuously update T2 based on the second preset method until the updated T2 meets the temperature constraint at the lower edge of the discharge pipe orifice.

[0052] Wherein, the second preset method is: when T2 - 25 > 0.05, increase the value of H2; when T2 - 25 < -0.05, decrease the value of H2. Then, replace the initial value of H2 with the adjusted value of H2, and replace the initial value of H1 with the target value of H1, and go to S2.

[0053] Optionally, the simulation design method further includes:

[0054] S6. Adjust the preset value of R, and repeat steps S2 - S5 to reduce the value of H; where H = H1 + H2.

[0055] (III) Beneficial effects

[0056] The present invention provides a simulation design method for a cryogenic liquid heater. Compared with the prior art, it has the following beneficial effects:

[0057] In the technical solution provided by the present invention, S1. Obtain the preset values of R, R0, H1, H2, T, U, V, W, p and initialize the grid; S2. Based on the preset values of R, R0, H1, H2, T, U, V, W, p and the pre-constructed numerical calculation iteration equation, obtain the equation solutions corresponding to each grid node in the initialized grid; S3. Based on the equation solutions and the adaptive grid, continuously divide the initialized grid to obtain the divided grid, which is used as the first grid; S4. Based on the first grid and the coordinates of the upper edge point and the lower edge point of the discharge pipe orifice, determine the temperature value T1 of the upper edge point of the low discharge pipe orifice and the temperature value T2 of the lower edge point of the discharge pipe orifice; S5. Determine whether T1 meets the temperature constraint at the upper edge of the discharge pipe orifice and whether T2 meets the temperature constraint at the lower edge of the discharge pipe orifice. If so, use the initial value of H1 as the target value of H1 and the initial value of H2 as the target value of H2; if not, adjust the initial values of H1 and H2, repeat steps S2 - S4, update T1 and T2 until the updated T1 meets the temperature constraint at the upper edge of the discharge pipe orifice and the updated T2 meets the temperature constraint at the lower edge of the discharge pipe orifice, and use the adjusted H1 and H2 as the target values of H1 and H2 respectively.

[0058] In the heating pipe, the heat exchange process between the low-temperature liquid and the water vapor is a coupled process of low-temperature liquid droplet settlement and vaporization, heat transfer between the gas and the water vapor, and gas flow. Based on the above technical solution, in the cylindrical coordinate system, a mathematical model is established for the flow and heat exchange process between the gas and the water vapor. The partial differential equation group in the mathematical model is discretized based on the hybrid difference scheme, and a solution method for the discretized partial differential equation group is established, so as to obtain the temperature value of the upper edge point of the discharge pipe orifice and the temperature value of the lower edge point of the discharge pipe orifice. Then, based on the preset upper edge temperature constraint of the pipe orifice and the lower edge temperature constraint of the discharge pipe orifice, the preset values of the discharge pipe position and the inner diameter of the heating pipe are adjusted, so as to obtain the theoretical results of the inner diameter of the heating pipe and the discharge pipe position. By this method, the R & D time of the low-temperature liquid heater is shortened, the test cost in the R & D process is reduced, and the R & D efficiency is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0060] Figure 1 The external view of a low-temperature liquid heater provided by an embodiment of the present invention;

[0061] Figure 2 The flowchart of a simulation design method for a low-temperature liquid heater provided by an embodiment of the present invention;

[0062] Figure 3 The flowchart of a simulation design method for a low-temperature liquid heater in the specific implementation process provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0063] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0064] In an embodiment of the present invention, by providing a simulation design method for a cryogenic liquid heater, a mathematical model is established in a cylindrical coordinate system during the flow and heat exchange process of gas and water vapor. Based on a hybrid difference scheme, the partial differential equation group in the mathematical model is discretized, and a solution method for the discretized partial differential equation group is established, so as to obtain the temperature value of the upper edge point of the low-emission pipe orifice and the temperature value of the lower edge point of the emission pipe orifice in the cryogenic liquid heater. Then, based on the preset temperature constraints of the upper edge of the pipe orifice and the temperature constraints of the lower edge of the emission pipe orifice, the preset values of the position of the emission pipe and the inner diameter of the heating pipe are adjusted, so as to obtain the theoretical results of the inner diameter of the heating pipe and the position of the emission pipe. By this method, the R & D time of the cryogenic liquid heater is shortened, the test cost during the R & D process is reduced, and the R & D efficiency is improved.

[0065] The overall idea of the technical solution in the embodiment of the present invention to achieve the above beneficial effects is as follows:

[0066] In the heating pipe of the cryogenic liquid heater, the heat exchange process between the cryogenic liquid and water vapor involves flow-heat transfer processes such as the settlement of the cryogenic liquid, the heat exchange between the cryogenic liquid and the cryogenic gas, the flow of the cryogenic gas, and the settlement of liquid water.

[0067] In view of the complex substance system and heat transfer principle involved in the heating pipe, the conventional design method of obtaining empirical formulas based on a large number of experiments not only has high costs and long time, but also has a narrow application range. Starting from the basic formulas of fluid mechanics, through reasonable assumptions and simplifications, the design results can be quickly obtained, so as to achieve the purpose of reducing R & D costs, improving R & D efficiency and level.

[0068] In order to better understand the above technical solution, the above technical solution will be described in detail below in combination with the specification drawings and specific implementation manners.

[0069] See Figure 1 , Figure 1 is an external view of a cryogenic liquid heater provided by an embodiment of the present invention. As Figure 1 shown, the cryogenic liquid heater includes: a heating pipe, an emission pipe, a steam main pipe, a liquid distributor, and a liquid collecting main pipe; the liquid collecting main pipe is connected to the upper part of the vertically arranged heating pipe, above the liquid distributor, and the periphery of the liquid distributor is closely connected to the inner wall of the upper part of the heating pipe; the steam main pipe is connected and extends into the lower part of the heating pipe; one end of the emission pipe is connected to the other side of the middle part of the heating pipe, and one end communicates with the outside air upward and is below the liquid distributor.

[0070] Wherein, R represents the radius of the heating pipe; R0 is the radius of the emission pipe; H1 is the height from the tip of the solid cone nozzle of the liquid distributor to the center of the emission pipe orifice; H2 is the height from the center of the emission pipe to the upper edge of the steam main pipe, and H = H1 + H2.

[0071] During the operation of a cryogenic liquid heater, the cryogenic liquid settles in the heating tube. Along with the heat transfer and mass transfer processes, the cryogenic liquid vaporizes. However, the water vapor in the cryogenic gas and water vapor after the cryogenic liquid vaporizes undergoes sublimation on the surface of the cryogenic liquid, resulting in changes in the droplet shape, volume, and density of the cryogenic liquid, thereby affecting the settling process. In particular, affected by the sublimation of water vapor, the volume and density of the cryogenic droplets will undergo slight changes, making the lateral influence of the cryogenic droplets by gas flow smaller. Therefore, it can be simplified to settling along the direction of gravity.

[0072] For the settling process of cryogenic liquid, that is, the description of the relationship between the falling speed of cryogenic droplets and time, the following settling equation can be established:

[0073]

[0074]

[0075]

[0076] Its boundary condition is: z = 0, V d = 0 1 - 4

[0077] Among them, V d represents the velocity component of the droplet along the z - direction (vertical direction), ρ p represents the density of the cryogenic droplet, ρ represents the gas density, g represents the acceleration due to gravity, C D represents the drag coefficient, W represents the velocity component of the gas along the z - direction (vertical direction), Re is the component in the z - direction (vertical direction), t represents time, and Re represents the droplet Reynolds number.

[0078] Based on the above content, Equation 1 - 1 can be transformed into

[0079]

[0080] It can be seen that the above Equation 1 - 5 and boundary condition 1 - 4 will constitute a complete droplet settling equation.

[0081] Under steady - state conditions, the heat transfer paths that occur include:

[0082] ① Heat transfer between the cryogenic liquid and the cryogenic gas causes the moisture in the cryogenic gas to condense or sublime on the surface of the cryogenic liquid droplets and settle together with the cryogenic liquid droplets. Because the density of the cryogenic liquid is different from that of ice, ice adheres to the upper or lower part of the cryogenic liquid droplets.

[0083] Among them, the heat transfer amount and the heat of solidification during the condensation or sublimation of moisture are small, so this part of the heat transfer process can be ignored.

[0084] ② When the water vapor content in the gas in the heating tube is relatively high, if the height of the gas outlet of the heating tube is relatively low, there will be a strong heat exchange between the low-temperature liquid droplets and water vapor. If the outlet height is relatively high, only the heat exchange between water ice and water vapor will occur, and even a situation of partial wasted height will appear. Therefore, in order to minimize the height of the gas outlet of the heating tube as much as possible, it is necessary for the low-temperature liquid droplets to settle and penetrate to directly contact the water vapor.

[0085] ③ The heat transfer process occurs on the surface of the low-temperature liquid droplets, that is, intense heat exchange and gasification occur in the 100 °C environment of water vapor, resulting in the formation of a layer of moist low-temperature gas layer near the low-temperature liquid droplets as a diffusion resistance layer (i.e., boundary layer). Outside the boundary layer, the temperature of the low-temperature gas is the same as the ambient temperature. Therefore, before the low-temperature liquid is completely evaporated, there will be no gas-phase bulk heat exchange behavior between the low-temperature gas and water vapor.

[0086] For the flow mixing process between the low-temperature gas and water vapor, in the turbulent airflow, extremely small water mist droplets are formed and become part of the airflow as they move with the airflow. Thus, it can be assumed that water forms ice and settles together with the low-temperature liquid, and the collision probability is small, so that the number of droplets (or particles) in the heating tube remains unchanged, and the droplet volume is the sum of the volumes of the remaining low-temperature liquid and ice.

[0087] ④ From the analysis of this heat transfer process, the rationality of neglecting the influence of the radial movement of droplets on droplet settlement before is proved.

[0088] ⑤ In this technical solution, the main heat transfer occurring inside the heating tube is phase change heat transfer, which is much greater than the heat released by the change in gas temperature. During the descent of the low-temperature droplets, there is a relatively high relative velocity with respect to the gas and a relatively high heat transfer temperature difference. Therefore, the influence of the heat transfer - mass transfer boundary layer can be ignored. Since it is phase change heat transfer, the heat exchange amount between the low-temperature gas and the water mist is relatively small and is ignored.

[0089] Based on the above treatment, by reasonably simplifying the low-temperature droplet settlement process, it is convenient to establish a new mathematical model in the process of flow heat exchange between the gas and water vapor.

[0090] Furthermore, based on the above heat transfer process analysis, the variation equation of the diameter of the low-temperature droplets with time can be obtained, that is, the droplet diameter equation:

[0091]

[0092] or

[0093]

[0094] Its boundary equation is: z = 0, d p = d p0 .

[0095] where k s represents the heat transfer coefficient, and T represents the temperature; represents the boiling point of the cryogenic liquid; represents the heat of vaporization of the cryogenic liquid droplet; represents the heat of vaporization of water; represents the heat of fusion of water; represents the density of solid water; represents the density of the liquid cryogenic liquid.

[0096] And in the steady-state process, the droplet density is the average density of the cryogenic liquid and water ice, and the equation for the change of the droplet density with height is:

[0097]

[0098] Boundary condition: z = 0,

[0099] where the ks in Equation 3-1 is calculated by the heat transfer J factor.

[0100] Bed void fraction:

[0101] Heat transfer factor:

[0102] where,

[0103] ε B represents the bed void fraction; J H represents the heat transfer J factor.

[0104] Since the gas outflow position is at the middle height of the heating tube, the gas flows out separately at the upper end and the lower end of the discharge tube. It should be noted that according to the energy-saving design requirements, there is no water vapor flowing out in the heating tube. Therefore, assuming that the water vapor is quickly condensed and consumed, at the same pressure, the mass flow rate in the heating tube only has different directions, so the initial mass flow rate of the cryogenic liquid is halved and used as the initial gas mass flow rate for calculating ε B and k s when

[0105] Generally,

[0106] where G in represents the gas mass flow rate flowing into the heating tube; G out represents the gas mass flow rate flowing out of the heating tube

[0107] According to the Reynolds transport formula, the continuity equation is obtained:

[0108]

[0109] Among them, θ represents the circular cross-section angular coordinate of the spatial point in the cylindrical coordinate system; U represents the radial gas velocity; V represents the circumferential gas velocity; n represents the number of cryogenic droplets.

[0110] In the cylindrical coordinate system, Equation 5-1 represents the relationship between the radial gas velocity U, the tangential velocity V, and the axial velocity W.

[0111] Meanwhile, the gas volume expansion rate δ caused by the vaporization of cryogenic liquid and the sublimation of water vapor is:

[0112]

[0113] When the density ρ changes little, under atmospheric pressure conditions, the fluid flow equation is simplified to the N-S equation as:

[0114]

[0115] Its boundary conditions are:

[0116] z = 0, U = 0, V = 0, W = 0;

[0117] z = H, H = H1 + H2, U = 0, V = 0, W = W w .

[0118] r = R, except for 3π / 2 < θ < 2π), U = 0, V = 0, W = 0.

[0119] Under atmospheric pressure operation, the gas density in the heating tube is small and the gravity work is small. Therefore, the gravity work is ignored, and the energy equation in the cylindrical coordinate system obtained is:

[0120]

[0121] Its boundary conditions are: z = 0, T = T0; r = R, except for z = H, H = H1 + H2, T = T w .

[0122] To prevent water vapor from invading upward and blocking the orifices of the liquid distributor, therefore, the upper edge temperature of the gas discharge pipe should not be lower than -50°C; to make full use of water vapor, that is, to prevent water vapor from flowing out of the outlet of the gas discharge pipe, therefore, the lower edge temperature of the gas discharge pipe should not be higher than 100°C.

[0123] For the physical property equations required in the calculation process, they can be estimated according to the physical property estimation formulas of relevant substances.

[0124] See Figure 2 , Figure 2Schematic diagram of the process of a simulation design method for a cryogenic liquid heater provided by an embodiment of the present invention. As Figure 2 shown, a simulation design method for a cryogenic liquid heater includes:

[0125] S1. Obtain the preset values of R, R0, H1, H2, T, U, V, W, p and initialize the grid.

[0126] Among them, T represents the temperature inside the heating tube, U represents the radial velocity of the gas inside the heating tube, V represents the circumferential velocity of the gas inside the heating tube, W represents the axial velocity of the gas inside the heating tube, and p represents the gas pressure inside the heating tube; the construction process of the initialized grid includes: performing grid division on the heating tube based on an adaptive grid to obtain the initialized grid.

[0127] S2. Based on the preset values of R, R0, H1, H2, T, U, V, W, p and the pre-constructed numerical calculation iteration equation, obtain the equation solutions corresponding to each grid node in the initialized grid.

[0128] Among them, the equation solutions include the numerical values of T, U, V, W, p; the construction process of the numerical calculation iteration equation includes: discretizing the partial differential equation system in the mathematical model based on a mixed difference format, and taking the discretized partial differential equation system as the numerical calculation iteration equation; the mathematical model includes: the sedimentation equation system of cryogenic droplets, and the partial differential equation system in the cylindrical coordinate system during the mass transfer - heat transfer - gas flow process of cryogenic droplets and water vapor.

[0129] For step S2, the sedimentation equation system includes:

[0130]

[0131]

[0132]

[0133] The boundary conditions are: z = 0, V d = V d 0, d p = d p 0, ρ p = ρ p 0.

[0134] Among them, V d represents the sedimentation velocity of cryogenic droplets; z represents the axial coordinate of the spatial point, and the downward direction is positive; W represents the axial velocity of the gas; ρ p represents the density of cryogenic droplets; ρ represents the gas density; d p represents the droplet diameter; g represents the acceleration due to gravity; C D represents the drag coefficient; p represents the gas pressure; ks represents the heat transfer coefficient; T represents the temperature; n represents the number of low-temperature droplets; represents the boiling point of the cryogenic liquid; represents the heat of vaporization of the low-temperature droplet; represents the heat of vaporization of water; represents the heat of fusion of water; represents the density of solid water; represents the density of the liquid cryogenic liquid.

[0135] In the process of constructing this sedimentation equation set, the horizontal movement of low-temperature droplets and the collision, splitting, and merging between different low-temperature droplets are ignored. Only the sedimentation of low-temperature droplets in the gravitational direction is considered, and the number of low-temperature droplets in the heating tube is constant during the sedimentation process.

[0136] The partial differential equation set in the cylindrical coordinate system includes: the continuity equation, the volume expansion rate equation, the momentum equation, and the energy equation

[0137] Continuity equation:

[0138]

[0139] Volume expansion rate equation:

[0140] Momentum equation:

[0141]

[0142] Energy equation:

[0143] The boundary conditions are:

[0144] z = 0, U = 0, V = 0, W = 0, T = T0, and δ = 0;

[0145] z = H, H = H1 + H2, U = 0, V = 0, W = W w , T = T w ;

[0146] r = R, except for 3π / 2 < θ < 2π), U = 0, V = 0, W = 0,

[0147] where r represents the cylindrical radial coordinate of a spatial point in the cylindrical coordinate system; θ represents the circular cross-section angular coordinate of a spatial point in the cylindrical coordinate system; U represents the gas radial velocity; V represents the gas circumferential velocity; n represents the number of droplets; Cp represents the gas isobaric heat capacity; λ represents the gas thermal conductivity; δ represents the gas volume expansion rate; p represents the gas pressure; μ represents the gas viscosity.

[0148] In addition, a hybrid difference scheme is adopted for the difference schemes of the momentum equation and the energy equation, including: the upwind scheme or the central difference scheme.

[0149] For the momentum equation

[0150] For the energy equation

[0151] Among them, it is judged whether it satisfies (s = r, θ, z). If so, the difference equations of the momentum equation and the energy equation in the corresponding coordinate direction are rewritten into the upwind scheme.

[0152] If not, the difference equations of the momentum equation and the energy equation in the corresponding coordinate direction are rewritten into the central difference scheme.

[0153] S3. Based on the equation solution and the adaptive grid, continuously refine the initial grid to obtain the refined grid as the first grid.

[0154] Among them, the equation solutions corresponding to the grid nodes in the first grid satisfy the adaptive grid refinement rules.

[0155] Specifically, step S3 includes:

[0156] S301. Based on the equation solution and the adaptive grid, refine the initial grid to obtain the refined grid.

[0157] S302. Judge whether the equation solutions corresponding to the grid nodes in the refined grid satisfy the adaptive grid refinement rules; if so, take the refined grid as the first grid; if not, go to S303.

[0158] S303. Determine the existing grid nodes around the newly added grid nodes in the refined grid, average the equation solutions of the existing grid nodes, and use the averaged equation solutions as the equation solutions of the newly added grid nodes.

[0159] S304. Replace the preset values of T, U, V, W, and p with the equation solutions of the newly added grid nodes, and go to S2.

[0160] Based on the above processing, through the adaptive grid and the equation solutions of the numerical calculation iterative equation, continuously divide the initial grid, and judge whether the division is completed based on the adaptive grid refinement rules. Furthermore, in the initial grid after the division is completed, the temperature values of the upper edge point and the lower edge point of the discharge pipe orifice can be obtained based on the coordinates of the upper edge point and the lower edge point of the discharge pipe orifice.

[0161] S4. Based on the coordinates of the upper edge point and the lower edge point of the discharge pipe orifice on the first grid, determine the temperature value T1 of the upper edge point of the low discharge pipe orifice and the temperature value T2 of the lower edge point of the discharge pipe orifice.

[0162] For step S4, based on the coordinates of the upper edge point and the lower edge point of the discharge pipe orifice, determine the solution of the equation for the corresponding grid node in the first grid, and then based on this solution of the equation, obtain the temperature value T1 of the upper edge point of the low discharge pipe orifice and the temperature value T2 of the lower edge point of the discharge pipe orifice in the low-temperature liquid heater.

[0163] S5. Judge whether T1 satisfies the upper edge temperature constraint of the discharge pipe orifice and whether T2 satisfies the lower edge temperature constraint of the discharge pipe orifice. If so, take the initial value of H1 as the target value of H1 and the initial value of H2 as the target value of H2; if not, adjust the initial values of H1 and H2, repeat steps S2 - S4, update T1 and T2 until the updated T1 satisfies the upper edge temperature constraint of the discharge pipe orifice and the updated T2 satisfies the lower edge temperature constraint of the discharge pipe orifice, and take the adjusted H1 and H2 as the target values of H1 and H2 respectively.

[0164] Among them, the upper edge temperature constraint of the discharge pipe orifice is -0.05 ≤ T1 + 50 ≤ 0.05, and the lower edge temperature constraint of the discharge pipe orifice is -0.05 ≤ T2 - 25 ≤ 0.05.

[0165] Specifically, step S5 includes:

[0166] S501. Judge whether T1 satisfies the upper edge temperature constraint of the discharge pipe orifice. If it satisfies, take the parameter value of H1 as the target value of H1 and go to S502; if T1 does not satisfy the upper edge temperature constraint of the discharge pipe orifice, continuously adjust T1 based on the first preset method until the adjusted T1 satisfies the upper edge temperature constraint of the discharge pipe orifice.

[0167] Among them, the first preset method is: when T1 + 50 > 0.05, reduce the value of H1; when T1 + 50 < -0.05, increase the value of H1; then, replace the initial value of H1 with the adjusted value of H1 and go to S2.

[0168] S502. Judge whether T2 satisfies the lower edge temperature constraint of the discharge pipe orifice. If it does, take the initial value of H2 as the target value of H2; if not, continuously update T2 based on the second preset method until the updated T2 satisfies the lower edge temperature constraint of the discharge pipe orifice.

[0169] Among them, the second preset method is: when T2 - 25 > 0.05, increase the value of H2; when T2 - 25 < -0.05, reduce the value of H2, then, replace the initial value of H2 with the adjusted value of H2 and the target value of H1 with the initial value of H1, and go to S2.

[0170] The simulation design method further includes:

[0171] S6. Adjust the preset value of R, and repeat steps S2 - S5 to reduce the value of H. Wherein, H = H1 + H2.

[0172] The method for reducing the value of H in step S6 includes:

[0173] S601. Increase the preset value of R, and execute steps S2 - S5.

[0174] S602. Determine whether the value of H decreases. If so, go to S603; if not, go to S604.

[0175] S603. Increase the initial value of R again, and execute steps S2 - S5. And repeat the increase of the initial value of R and the execution of steps S2 - S5 until the value of H increases for the first time, then go to S605.

[0176] S604. Decrease the initial value of R, and execute steps S2 - S5; and repeat the decrease of the initial value of R and the execution of steps S2 - S5; until the value of H increases for the first time, then go to S605.

[0177] S605. Calculate the average value of the R value corresponding to the first increase in the value of H and the R value corresponding to the last decrease in the value of H, and use this average value as the final value of R.

[0178] S606. Substitute the final value of R back into the numerical calculation iteration equation, and execute steps S2 - S5 to obtain the corresponding values of H1 and H2 as the final values of H1 and H2.

[0179] In the specific implementation process, the steps are as follows:

[0180] First, establish a differential equation system and divide the grid in a computer program; establishing a differential equation system is to perform discretization processing. Due to the existence of convection, a differential equation system with a mixed difference format (including boundary conditions) is used.

[0181] Dividing the grid means that after establishing the differential equation system, the cylinder corresponding to the heating pipe with side openings and two - end feeding is divided into grids. Among them, in order to improve the calculation accuracy, an adaptive grid is used, and the grid is cut and encrypted according to the solution of the numerical calculation iteration equation.

[0182] After the differential of the differential equation system and the meshing of the solution space, refer to Figure 3 , Figure 3 which is a schematic flow chart in the specific implementation process of a simulation design method for a cryogenic liquid heater provided by an embodiment of the present invention, and is programmed according to the device simulation design program block diagram.

[0183] Step 1: After inputting the preset values of R, R0, H1, H2 and the initial grid in the program interface, input the initial values [T U V W p] (i.e., the preset values of T, U, V, W, p) to obtain the equation solutions [T U V W p](0)(0)(0) of each grid node. According to [T U V W p](0)(0)(0), judge how to divide the grid according to the adaptive grid division rule to obtain grid E(1).

[0184] Among them, for the newly obtained grid nodes, obtain the average according to the data of the surrounding nodes to obtain the new equation solution [T U V W p](0)(0)(0). Solve [T U V W p](0)(0)(0) in the same way, then judge how to divide the grid according to the adaptive grid division rule, and solve again according to the newly obtained initial solution [T U V W p](0)(0)(0). In this way, repeat the cycle until the obtained equation solution [T U V W p](s)(0)(0) satisfies the adaptive grid division rule without further processing of the grid.

[0185] Step 2: Check the equation solution [T U V W p](s)(0)(0) to verify whether the lowest point of the side outlet (i.e., the lower edge point of the discharge pipe of the present invention) satisfies -0.05 < the temperature of the lower edge point of the discharge pipe - 25 < 0.05. If it does not satisfy, adjust the initial value of H2 to obtain H2(t + 1), and repeat the content of step three until the lowest point of the side outlet satisfies -0.05 < the temperature of the lower edge point of the discharge pipe - 25 < 0.05.

[0186] Step 3: Check the solution [T U V W p](s)(t)(0) to verify whether the highest point of the side outlet (i.e., the upper edge point of the discharge pipe of the present invention) satisfies -0.05 < the temperature of the upper edge point of the discharge pipe + 50 < 0.05. If it does not satisfy, adjust the initial value of H1 to obtain H1(S + 1), and then repeat the content of step three until the highest point of the side outlet satisfies -0.05 < the temperature of the lower edge point of the discharge pipe + 50 < 0.05.

[0187] Step 4: Output the result [T U V W p](s)(t)(v), which is the required numerical solution.

[0188] It should be noted that the value of R0 is determined according to the volume flow rate of the cryogenic liquid after complete gasification input based on the method specified in "HGT20570.06 - 95 Pipe Diameter Selection".

[0189] Among them, by changing the value of R, the effective height H of the heating pipe can be made smaller. Therefore, after determining the initial value of R according to the method specified in "HGT20570.06 - 95 Pipe Diameter Selection", perform simulation calculations according to steps 1 to 4. Then, increase or decrease the initial value of R and perform simulation calculations according to steps 1 to 4 to obtain H, H1, and H2 corresponding to R.

[0190] Among them, when comparing H before and after the adjustment of R, if H decreases, accept this R and further adjust R in this change direction until H increases.

[0191] At this time, the average value of the two numerical values before and after R when H increases can be selected as the new R. Then, recalculate H until the change range of H meets the preset error range, and then take the numerical values of R and H at this time as the final iterative result.

[0192] Among them, each time the value of R is adjusted and the result of the simulation design is obtained, it is necessary to verify whether water vapor permeates through the heating pipe and whether there are points on the upper cross-section of the effective height of the heating pipe where the temperature is higher than -50°C. The above verification conditions are the requirements for the normal operation of the heating pipe.

[0193] The finally determined value of R makes the height of the heating pipe the lowest, effectively improving the reliability of the heating pipe layout. In addition, the numerical results of the above simulation design are also the basis for arranging the position of the temperature sensor used to determine the control of the water vapor valve switch and adjustment mentioned in "A Low-Temperature Liquid Heating and Discharge Device and Its Usage Method" (Publication No.: CN113432035A).

[0194] To sum up, compared with the prior art, the following beneficial effects are achieved:

[0195] Based on the above processing, in the cylindrical coordinate system, a mathematical model is established during the flow and heat transfer process of gas and water vapor. Based on the mixed difference format, the partial differential equation group in the mathematical model is discretized, and a solution method for the discretized partial differential equation group is established, so as to obtain the temperature value of the upper edge point of the low-emission pipe orifice and the temperature value of the lower edge point of the discharge pipe orifice. Then, based on the preset upper edge temperature constraint of the pipe orifice and the lower edge temperature constraint of the discharge pipe orifice, the preset values of the position of the discharge pipe and the inner diameter of the heating pipe are adjusted, so as to obtain the theoretical results of the inner diameter of the heating pipe and the position of the discharge pipe. Through this method, the R & D time of this low-temperature liquid heater is shortened, the test cost during the R & D process is reduced, and the R & D efficiency is improved.

[0196] It should be noted that, in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the said element.

[0197] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A simulation design method for a cryogenic liquid heater, characterized in that, The low-temperature liquid heater includes: a heating pipe, a discharge pipe, a main steam pipe, a liquid distributor, and a main liquid collecting pipe; the main liquid collecting pipe is connected to the upper part of the vertically arranged heating pipe and is located above the liquid distributor; the periphery of the liquid distributor is tightly connected to the inner wall of the upper part of the heating pipe; the main steam pipe is connected and extends into the lower part of the heating pipe; one end of the discharge pipe is connected to the other side of the middle part of the heating pipe, and the other end is connected to the outside air upward and is located below the liquid distributor; wherein, R represents the radius of the heating pipe; R0 represents the radius of the discharge pipe; H1 represents the height from the tip of the solid cone nozzle of the liquid distributor to the center of the discharge pipe orifice; H2 represents the height from the center of the discharge pipe to the upper edge of the main steam pipe; The simulation design method includes: S1. Obtain the preset values of R, R0, H1, H2, T, U, V, W, p and initialize the grid; wherein, T represents the temperature inside the heating pipe, U represents the radial gas velocity inside the heating pipe, V represents the circumferential gas velocity inside the heating pipe, W represents the axial gas velocity inside the heating pipe, and p represents the gas pressure inside the heating pipe; the process of constructing the initialized grid includes: performing grid division on the heating pipe based on an adaptive grid to obtain the initialized grid; S2. Based on the preset values of R, R0, H1, H2, T, U, V, W, p and the pre-constructed numerical calculation iteration equation, obtain the equation solutions corresponding to each grid node in the initialized grid; wherein, the equation solutions include the numerical values of T, U, V, W, p; the process of constructing the numerical calculation iteration equation includes: discretizing the partial differential equation group in the mathematical model based on a hybrid difference scheme, and taking the discretized partial differential equation group as the numerical calculation iteration equation; the mathematical model includes: the sedimentation equation group of low-temperature droplets, and the partial differential equation group in the cylindrical coordinate system during the mass transfer - heat transfer - gas flow process of low-temperature droplets and water vapor; S3. Based on the equation solutions and the adaptive grid, continuously divide the initialized grid to obtain the divided grid, which is used as the first grid; wherein, the equation solutions corresponding to the grid nodes in the first grid satisfy the adaptive grid division rule; S4. Based on the first grid and the coordinates of the upper edge point and the lower edge point of the discharge pipe orifice, determine the temperature value T1 of the upper edge point of the low discharge pipe orifice and the temperature value T2 of the lower edge point of the discharge pipe orifice; S5. Judge whether T1 satisfies the temperature constraint of the upper edge of the discharge pipe orifice and whether T2 satisfies the temperature constraint of the lower edge of the discharge pipe orifice. If so, take the initial value of H1 as the target value of H1 and the initial value of H2 as the target value of H2; if not, adjust the initial values of H1 and H2, repeat steps S2 - S4, update T1 and T2 until the updated T1 satisfies the temperature constraint of the upper edge of the discharge pipe orifice and the updated T2 satisfies the temperature constraint of the lower edge of the discharge pipe orifice, and take the adjusted H1 and H2 as the target values of H1 and H2 respectively; Among them, the temperature constraint on the upper edge of the discharge pipe orifice is -0.05 ≤ T1 + 50 ≤ 0.05, and the temperature constraint on the lower edge of the discharge pipe orifice is -0.05 ≤ T2 - 25 ≤ 0.

05.

2. The method according to claim 1, characterized in that, The sedimentation equations in S2 include: The boundary conditions are: z = 0, V d = V d 0, d p = d p 0, ρ p = ρ p 0; Among them, V d represents the sedimentation velocity of the cryogenic droplets; z represents the axial coordinate of the spatial point, with the downward direction being positive; W represents the gas axial velocity; ρ p represents the density of the cryogenic droplets; ρ represents the gas density; d p represents the droplet diameter; g represents the acceleration due to gravity; C D represents the drag coefficient; p represents the gas pressure; k s represents the heat transfer coefficient; T represents the temperature; n represents the number of cryogenic droplets; represents the boiling point of the cryogenic liquid; represents the heat of vaporization of the cryogenic droplets; represents the heat of vaporization of water; represents the heat of fusion of water; represents the density of solid water; represents the density of the liquid cryogenic liquid.

3. The method according to claim 1, wherein The partial differential equations in cylindrical coordinates in S2 include: continuity equation, volume expansion rate equation, momentum equation, and energy equation; The continuity equation: The volume expansion rate equation: The momentum equation: The energy equation: The boundary conditions are: z = 0, U = 0, V = 0, W = 0, T = T0, and δ = 0; z = H, H = H1 + H2, U = 0, V = 0, W = W w , T = T w ; r = R, except for U = 0, V = 0, W = 0, Among them, r represents the cylindrical radial coordinate of a spatial point in the cylindrical coordinate system; θ represents the circular cross-section angular coordinate of a spatial point in the cylindrical coordinate system; U represents the gas radial velocity; V represents the gas circumferential velocity; n represents the number of low-temperature droplets; C p represents the isobaric heat capacity of the gas; λ represents the thermal conductivity of the gas; 6 represents the gas volume expansion rate; p represents the gas pressure; μ represents the gas viscosity.

4. The method according to claim 1, characterized in that, The judgment criterion for the hybrid difference scheme in S2 is: For the momentum equation For the energy equation Among them, judge whether it satisfies s = r, θ, z. If so, rewrite the momentum equation and energy equation in the corresponding coordinate direction into the upwind format; If not, rewrite the momentum equation and energy equation in the corresponding coordinate direction into the central difference scheme.

5. The method according to claim 1, wherein In S3, based on the equation solution and the adaptive grid, continuously refine the initialized grid to obtain the refined grid, which is used as the first grid, including: S301. Based on the equation solution and the adaptive grid, refine the initialized grid to obtain the refined grid; S302. Judge whether the equation solutions corresponding to the grid nodes in the refined grid satisfy the adaptive grid refinement rule; if so, use the refined grid as the first grid; if not, go to S303; S303. Determine the existing grid nodes around the newly added grid nodes in the refined grid, average the equation solutions of the existing grid nodes, and use the averaged equation solution as the equation solution of the newly added grid node; S304. Replace the preset values of T, U, V, W, and p with the equation solutions of the newly added grid nodes, and go to S2.

6. The method according to claim 1, wherein In S5, judge whether T1 satisfies the temperature constraint on the upper edge of the discharge pipe orifice and whether T2 satisfies the temperature constraint on the lower edge of the discharge pipe orifice. If so, use the initial value of H1 as the target value of H1 and the initial value of H2 as the target value of H2; if not, adjust the initial values of H1 and H2, repeat steps S2 - S4, update T1 and T2 until the updated T1 satisfies the temperature constraint on the upper edge of the discharge pipe orifice and the updated T2 satisfies the temperature constraint on the lower edge of the discharge pipe orifice, and use the adjusted H1 and H2 as the target values of H1 and H2 respectively, including: S501. Judge whether T1 satisfies the temperature constraint on the upper edge of the discharge pipe orifice. If it satisfies, use the parameter value of H1 as the target value of H1 and go to S502; if T1 does not satisfy the temperature constraint on the upper edge of the discharge pipe orifice, continuously adjust T1 based on the first preset method until the adjusted T1 satisfies the temperature constraint on the upper edge of the discharge pipe orifice; Among them, the first preset method is: when T1 + 50 > 0.05, reduce the value of H1; when T1 + 50 < -0.05, increase the value of H1; then, replace the initial value of H1 with the adjusted value of H1 and go to S2; S502. Judge whether T2 satisfies the temperature constraint on the lower edge of the discharge pipe orifice. If so, use the initial value of H2 as the target value of H2; if not, continuously update T2 based on the second preset method until the updated T2 satisfies the temperature constraint on the lower edge of the discharge pipe orifice; Among them, the second preset method is as follows: when T2 - 25 > 0.05, increase the value of H2; when T2 - 25 < -0.05, decrease the value of H2. Then, replace the initial value of H2 with the adjusted value of H2 and the target value of H1 with the initial value of H1, and go to S2.

7. The analog design method according to any one of claims 1 to 6, characterized in that The simulation design method further includes: S6. Adjust the preset value of R, and repeat steps S2 - S5 to reduce the value of H; where H = H1 + H2.

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