阅读说明：本技术 一种施加不同方向静电场控制饱和蒸气压和沸点的方法 (Method for controlling saturated vapor pressure and boiling point by applying electrostatic fields in different directions ) 是由 韩光泽 胡秋霞 蒙健佳 陈明东 于 2019-08-26 设计创作，主要内容包括：本发明属于工业应用领域,涉及一种施加不同方向静电场控制饱和蒸气压和沸点的方法。当静电场方向与气液相界面法向的夹角小于θ时,温度不变的情况下,能够升高气液平衡系统的饱和蒸气压；在气相压强不变的情况下,能够降低沸点,角度越小,饱和蒸气压和沸点的改变量越大；当静电场方向与气液相界面法向的夹角大于θ时,在温度不变的情况下,能够降低气液平衡系统的饱和蒸气压；在气相压强不变的情况下,能够提升沸点；当静电场方向与气液相界面法向的夹角约为θ时,静电场对气液平衡系统的饱和蒸气压和沸点无影响；当静电场方向一定时,改变电场强度以升高或降低对饱和蒸气压的影响。本发明强化了相变传质过程,提高了传热效率。(The invention belongs to the field of industrial application, and relates to a method for controlling saturated vapor pressure and boiling point by applying electrostatic fields in different directions. When the included angle between the direction of the electrostatic field and the normal direction of the gas-liquid phase interface is smaller than theta, the saturated vapor pressure of the gas-liquid balance system can be increased under the condition of unchanged temperature; under the condition that the pressure intensity of the gas phase is not changed, the boiling point can be reduced, and the smaller the angle is, the larger the change amount of the saturated vapor pressure and the boiling point is; when the included angle between the direction of the electrostatic field and the normal direction of the gas-liquid phase interface is larger than theta, the saturated vapor pressure of a gas-liquid balance system can be reduced under the condition of unchanged temperature; under the condition that the gas phase pressure intensity is not changed, the boiling point can be improved; when the included angle between the direction of the electrostatic field and the normal direction of the gas-liquid phase interface is about theta, the electrostatic field has no influence on the saturated vapor pressure and the boiling point of the gas-liquid balance system; when the direction of the electrostatic field is fixed, the electric field strength is changed to increase or decrease the influence on the saturated vapor pressure. The invention strengthens the phase change mass transfer process and improves the heat transfer efficiency.)

1. A method for controlling saturated vapor pressure and boiling point by applying electrostatic fields in different directions, which is characterized by comprising the following steps:

when the included angle between the direction of the electrostatic field and the normal direction of the gas-liquid phase interface is smaller than theta, the saturated vapor pressure of the gas-liquid balance system can be increased under the condition that the temperature of the gas-liquid balance system is not changed; under the condition that the pressure intensity of the gas phase is not changed, the boiling point can be reduced, and the smaller the angle is, the larger the change amount of the saturated vapor pressure and the boiling point is;

when the included angle between the direction of the electrostatic field and the normal direction of the gas-liquid phase interface is larger than theta, the saturated vapor pressure of the gas-liquid balance system can be reduced under the condition that the temperature of the gas-liquid balance system is not changed; under the condition that the gas phase pressure intensity is not changed, the boiling point can be improved, and the larger the angle is, the larger the change amount of the saturated vapor pressure and the boiling point is;

when the included angle between the direction of the electrostatic field and the normal direction of the gas-liquid phase interface is about theta, the electrostatic field has no influence on the saturated vapor pressure and the boiling point of the gas-liquid balance system;

when the direction of the electrostatic field is fixed, the electric field strength is changed to increase or decrease the influence on the saturated vapor pressure.

2. A method for controlling the saturated vapor pressure and boiling point by applying electrostatic fields in different directions, wherein θ is related to the selected substance.

3. The method for controlling the saturated vapor pressure and the boiling point according to the electrostatic field of claim 1, wherein the included angle θ is calculated by the following formula:

wherein: v. of^G、v^LIs the molar volume, ε, of the gas-and liquid-phase substances, respectively^L、ε^GThe dielectric constants of the liquid and gas phase materials, respectively.

4. The method of claim 1, wherein the electric field strength and the nature of the substance determine the amount of change of the electrostatic field in increasing or decreasing the saturated vapor pressure of the gas-liquid equilibrium system.

5. The method for controlling the saturated vapor pressure and the boiling point according to the electrostatic field of claim 4, wherein the amount of change of the saturated vapor pressure of the gas-liquid equilibrium system applying the electrostatic field with the intensity of the electrostatic field is calculated according to the following formula:

wherein: the quantity with the superscript "L" represents the physical quantity in the liquid phase, the quantity with the superscript "G" represents the physical quantity in the gas phase, p' is the applied staticSaturated vapor pressure at temperature T after electric field, p being saturated vapor pressure at temperature T without electrostatic field, ε₀V is the molar volume of the material, v is the dielectric constant in vacuum^G、v^LIs the molar volume of the gas and liquid phase material, respectively,. epsilon.is the dielectric constant of the material,. epsilon.^L、ε^GThe dielectric constants of the liquid and gas phase materials, respectively, and E the total applied electric field strength.

6. The method for controlling the saturated vapor pressure and the boiling point by the electrostatic field according to claim 5, wherein the unknown parameters in the formula (2) are functions of the boiling point under the condition that the saturated vapor pressure of the gas-liquid balance system is not changed, and the change relation of the boiling point of the gas-liquid balance system applying the electrostatic field effect with the electrostatic field intensity is obtained by solving an implicit function equation in the formula by a numerical method.

7. The method for controlling the saturated vapor pressure and the boiling point according to the electrostatic field of claim 1, wherein when the direction of the electrostatic field is parallel to the phase interface, i.e., θ ═ pi/2, and the system temperature is 25 ℃, the magnitude of the decrease of the saturated vapor pressure is larger and larger as the electric field intensity is increased.

8. The method for controlling the saturated vapor pressure and the boiling point according to the electrostatic field of claim 1, wherein when the direction of the electrostatic field is perpendicular to the phase interface, i.e. θ is 0, and the system temperature is 25 ℃, the magnitude of the increase of the saturated vapor pressure is larger and larger as the electric field strength is increased.

9. The method of claim 1, wherein the liquid phase electrostatic field is obtained by applying an electrostatic field to the gas-liquid equilibrium system, knowing the gas phase electrostatic field and the boundary conditions.

10. The method for controlling the saturated vapor pressure and the boiling point according to the electrostatic field of claim 1, wherein the liquid phase substance of the gas-liquid equilibrium system comprises: water, ethanol or toluene.

Technical Field

The invention belongs to the field of industrial application, and relates to a method for controlling saturated vapor pressure and boiling point by applying electrostatic fields in different directions.

Background

Gas-liquid phase transition refers to the process of converting a liquid phase into a gas phase or converting a gas phase into a liquid phase under specific external temperature and pressure. The phase change is a mass transfer and heat transfer process, for example, the heat released by the liquefaction of hot gas can be utilized to strengthen the heat transfer process in the production process, and the rectification separation operation of a rectification tower in a chemical plant also relates to the gas-liquid phase change process. The current separation technology has the problems of high energy consumption and low energy utilization rate, for example, the distillation process needs to continuously provide energy, wherein only part of the energy can be transferred into the substance to be absorbed, and the rest of the energy is dissipated to cause low transfer efficiency.

Temperature and pressure are two basic macroscopic physical quantities in a gas-liquid balance system, the gas-liquid conversion process can be carried out towards a desired direction by controlling the temperature or the pressure of the system, and the change of the pressure and the temperature in actual production means more equipment investment and energy consumption, and sometimes the benefit is not high due to the imperfect technology. Some production processes also require temperature and pressure control, for example, in a processing technology for extracting effective components from Chinese herbal medicines, on the premise of controlling the boiling of a solution, the vacuum degree and the heating amount of heating equipment are regulated to ensure that the effective components are not degraded due to overhigh temperature, and the production speed is reasonably controlled to reduce energy consumption. Therefore, developing a new technology to control the temperature and pressure of the gas-liquid equilibrium system is of great significance to improve efficiency and strengthen the phase change process.

The electrostatic field can effectively promote the change process of the gas-liquid balance system and promote the gas-liquid balance system to reach a new balance state. Researches show that the electrostatic field can promote the membrane distillation and reverse osmosis treatment processes, improve the mass transfer separation efficiency, promote the boiling of superheated liquid and enhance the heat transfer of a gas-liquid boiling system. The field separation is an approved novel separation technology, but at present, the field separation cannot be put into practical production, and a plurality of restrictive factors exist, so that the research on the influence of an electrostatic field on the pressure and the temperature of a gas-liquid balance system has extremely important guiding significance for correctly analyzing the aspects of distillation, strengthening the mass transfer process, improving the strengthening transfer efficiency and the like.

Disclosure of Invention

In order to solve the problems of the field separation technology and effectively control the temperature and the vapor pressure when a gas-liquid balance system is balanced, the invention provides a method for controlling the saturated vapor pressure and the boiling point by applying electrostatic fields in different directions, thereby achieving the purposes of controlling the increase or decrease of the saturated vapor pressure and the boiling point and the change amount thereof, changing the balance state of the system, strengthening the phase-change mass transfer process and improving the heat transfer efficiency.

The invention is realized by adopting the following technical scheme:

a method for controlling saturated vapor pressure and boiling point by applying electrostatic fields in different directions, comprising the following steps:

when the included angle between the direction of the electrostatic field and the normal direction of the gas-liquid phase interface is smaller than theta, the saturated vapor pressure of the gas-liquid balance system can be increased under the condition that the temperature of the gas-liquid balance system is not changed; under the condition that the pressure intensity of the gas phase is not changed, the boiling point can be reduced, and the smaller the angle is, the larger the change amount of the saturated vapor pressure and the boiling point is;

when the included angle between the direction of the electrostatic field and the normal direction of the gas-liquid phase interface is larger than theta, the saturated vapor pressure of the gas-liquid balance system can be reduced under the condition that the temperature of the gas-liquid balance system is not changed; under the condition that the gas phase pressure intensity is not changed, the boiling point can be improved, and the larger the angle is, the larger the change amount of the saturated vapor pressure and the boiling point is;

when the included angle between the direction of the electrostatic field and the normal direction of the gas-liquid phase interface is about theta, the electrostatic field has no influence on the saturated vapor pressure and the boiling point of the gas-liquid balance system;

when the direction of the electrostatic field is fixed, the electric field strength is changed to increase or decrease the influence on the saturated vapor pressure.

Further, θ is related to the selected substance.

Preferably, the included angle θ is calculated by the following formula:

wherein: v. of^G、v^LIs the molar volume, ε, of the gas-and liquid-phase substances, respectively^L、ε^GThe dielectric constants of the liquid and gas phase materials, respectively.

Further, the electric field intensity and the nature of the substance determine the magnitude of the change of the electrostatic field to the increase or decrease of the saturated vapor pressure of the gas-liquid equilibrium system.

Preferably, under the condition of constant temperature, the magnitude of the change of the saturated vapor pressure of the gas-liquid equilibrium system applying the electrostatic field action with the intensity of the electrostatic field is calculated by the following formula:

wherein: the amount with the superscript "L" represents the physical quantity in the liquid phase, the amount with the superscript "G" represents the physical quantity in the gas phase, p' is the saturated vapor pressure at temperature T after the application of an electrostatic field, p is the saturated vapor pressure at temperature T without the action of an electrostatic field,. epsilon₀V is the molar volume of the material, v is the dielectric constant in vacuum^G、v^LIs the molar volume of the gas and liquid phase material, respectively,. epsilon.is the dielectric constant of the material,. epsilon.^L、ε^GThe dielectric constants of the liquid and gas phase materials, respectively, and E the total applied electric field strength.

Preferably, under the condition that the saturated vapor pressure of the gas-liquid balance system is not changed, the unknown parameters in the calculation formula of the variation of the saturated vapor pressure along with the electrostatic field intensity are functions of the boiling point, and the change relation of the boiling point of the gas-liquid balance system applying the electrostatic field effect along with the electrostatic field intensity is obtained by solving an implicit function equation in the formula by a numerical method.

Preferably, when the electrostatic field direction is parallel to the phase interface, i.e. θ ═ pi/2, and the system temperature is 25 ℃, the magnitude of the decrease of the saturated vapor pressure is larger and larger as the electric field strength is increased.

Preferably, when the electrostatic field direction is perpendicular to the phase interface, i.e. θ is 0, and the system temperature is 25 ℃, the magnitude of the increase of the saturated vapor pressure is larger and larger as the electric field strength is increased.

Further, an electrostatic field is applied to the gas-liquid balance system, a gas-phase electrostatic field is known, and a liquid-phase electrostatic field is obtained through a boundary condition.

Further, the liquid phase material of the gas-liquid equilibrium system may be any dielectric, including: water, ethanol or toluene.

Compared with the prior art, the invention has the following beneficial effects:

(1) the static field can change the balance state of the system, so that the balance pressure and temperature of the gas-liquid balance system are changed, the increase or decrease of the vapor pressure and the boiling point is related to the action direction of the static field, and the change quantity is related to the property of the substance and the electric field intensity. Given a specific substance, it can be calculated that when the direction of the electrostatic field is at a certain angle to the normal of the phase interface, no influence is exerted on the dielectric system. If the direction of the electrostatic field is smaller than the included angle, the saturated vapor pressure of the gas-liquid two-phase balance system can be increased under the condition that the temperature of the system is not changed, the boiling point can be reduced under the condition that the gas phase pressure is not changed, and the smaller the angle is, the larger the change amount of the saturated vapor pressure and the boiling point is; if the electrostatic field direction is greater than this contained angle, under the unchangeable condition of system temperature, can reduce the saturated vapor pressure of gas-liquid two-phase equilibrium system, under the unchangeable condition of gaseous phase pressure, can promote the boiling point, the angle is bigger, and the change of saturated vapor pressure and boiling point is bigger. When the direction of the electrostatic field is constant, increasing the electric field strength can increase the influence on the vapor pressure. The invention controls the increase or decrease of saturated vapor pressure and boiling point and the change amount thereof by applying different electrostatic field action directions and electric field intensities, strengthens the phase change mass transfer process and improves the heat transfer efficiency.

(2) The invention relates to a method for controlling the change of saturated vapor pressure and boiling point of a substance in a gas-liquid balance system through an electrostatic field, which can make the influence of the electrostatic field zero in a certain direction, can be applied to the separation processes such as purification, concentration, distillation and separation, and can also be applied to various production processes needing to regulate and control the vapor pressure or boiling point of the substance.

Drawings

FIG. 1 is a schematic diagram of an electrostatic field of any direction acting on a gas-liquid balance system according to an embodiment of the present invention;

FIG. 2 is a schematic diagram showing the change of the influence of the action direction of the electrostatic field on the vapor pressure and the boiling point in one embodiment of the present invention;

FIG. 3 is a schematic diagram of the effect of the electric field strength on the vapor pressure of an electrostatic field oriented parallel to the phase boundary in one embodiment of the present invention;

fig. 4 is a schematic diagram of the influence of the electric field strength on the vapor pressure of the electrostatic field directed perpendicular to the phase boundary in one embodiment of the present invention.

Detailed Description

For a better understanding of the present invention, reference is made to the following description taken in conjunction with the accompanying drawings and examples, which are set forth, however, not to limit the scope of the invention as claimed.

A method for controlling saturated vapor pressure and boiling point by applying electrostatic fields in different directions, comprising the following steps:

and S1, when the included angle between the direction of the electrostatic field and the normal direction of the gas-liquid phase interface is smaller than theta, the theta is related to the selected substance. Under the condition that the temperature of the gas-liquid balance system is not changed, the saturated vapor pressure of the gas-liquid balance system can be increased; under the condition that the pressure intensity of the gas phase is not changed, the boiling point can be reduced, and the smaller the angle is, the larger the change amount of the saturated vapor pressure and the boiling point is;

and S2, when the included angle between the direction of the electrostatic field and the normal direction of the gas-liquid phase interface is larger than theta, the theta is related to the selected substance. Under the condition that the temperature of the gas-liquid balance system is not changed, the saturated vapor pressure of the gas-liquid balance system can be reduced; under the condition that the gas phase pressure intensity is not changed, the boiling point can be improved, and the larger the angle is, the larger the change amount of the saturated vapor pressure and the boiling point is;

s3, when the included angle between the direction of the electrostatic field and the normal direction of the gas-liquid phase interface is about theta, the theta is related to the selected substance, and the electrostatic field has no influence on the saturated vapor pressure and the boiling point of the gas-liquid balance system;

s4, when the electrostatic field is in a certain direction, the electric field strength is changed to increase or decrease the influence on the vapor pressure.

Steps S1, S2, and S3 can be understood with reference to fig. 1, in this embodiment, the system under study is a thermodynamic gas-liquid equilibrium system, and the system has two phases, wherein one phase is a gas (gas) phase and the other phase is a liquid (liquid) phase, the volume V of the system is constant, there is no exchange of material and energy with the outside, and the total amount of material in the system is constant. And applying an electrostatic field to the system, wherein the liquid-phase electrostatic field can be obtained through boundary conditions by knowing a gas-phase electrostatic field. The boundary condition can be expressed asWhereinThe electric displacement components of the liquid phase and the gas phase perpendicular to the phase interface are respectively,the electric field strength components of the liquid and gas phases parallel to the phase interface, respectively. The pressure difference exists in a gas-liquid two-phase interface, and the pressure difference equation is as follows:

wherein the amount with the superscript "L" represents the physical quantity in the liquid phase. Δ p is the pressure difference, ε, between the gas and liquid phases after application of an electric field₀Is a vacuum dielectric constant of ∈^LIs the dielectric constant of the liquid phase material, E_t、E_nThe electric field strength components parallel to the phase interface and perpendicular to the phase interface, respectively.

In the equilibrium of gas phase and liquid phase, equivalent chemical potential is equal to mu 'under the action of electrostatic field'^G(T,p′)＝μ′^L(T, p' + Δ p), the equivalent chemical potential under the action of electrostatic field is expressed asThe amount with the prime designation indicates the physical quantity under the influence of the electrostatic field. Mu represents the chemical potential of the substance, and the parameter behind the bracket represents the corresponding chemical potential in the state, for example, mu (T, p ') represents the chemical potential without the action of an electric field at a temperature Texternal pressure of p'.Is a physical quantity describing the change of dielectric constant with the density of a substance itself when the temperature is constant. From the above theoretical basis, the expression of the gas phase pressure at constant temperature can be derived:

wherein the amount with the superscript "L" represents the physical quantity in the liquid phase and the amount with the superscript "G" represents the physical quantity in the gas phase. p' is the saturated vapor pressure at temperature T after the application of the electrostatic field, p is the saturated vapor pressure at temperature T without the action of the electrostatic field, ε₀V is the molar volume of the material, v is the dielectric constant in vacuum^G、v^LIs the molar volume of the gas and liquid phase material, respectively,. epsilon.is the dielectric constant of the material,. epsilon.^L、ε^GDielectric constants of liquid and gas phase materials, respectively, E is the total applied electric field strength, E_tIs the component of the electric field parallel to the phase boundary, E_nIs the electric field component perpendicular to the phase interface.

If there is an electrostatic field in any direction in the gas phase, the component of the electrostatic field parallel to the phase interface is E_tThe electrostatic field component perpendicular to the phase interface in the gas phase is Esin θThe electrostatic field component perpendicular to the phase interface in the liquid phase satisfiesThe angle range of theta is [0, pi/2 ]]Substituting the above equation can obtain a saturated vapor pressure expression related to the angle and the magnitude of the field strength:

solving using the above equation yields:

under the condition of constant temperature, the saturated vapor pressure of a gas-liquid balance system applying the action of an electrostatic field is in a relation of changing with the intensity of the electrostatic field.

② unknown parameters p, v in formula (3) under the condition of constant system vapor pressure^G、v^L、ε^L、ε^GAre all functions of boiling point T. Specifically, the saturated vapor pressure p in the absence of an electrostatic field is derived from the Antoine formulaThe constant A, B, C can be inquired by a related physical property manual; molar volume of gasWherein R is an ideal gas constant, R is 8.314m³·Pa·mol^-1·K^-1(ii) a Molar volume of liquidWherein M is the relative molecular mass of the substance, and the density rho of the liquid is represented by the formulaGiven, the constant A, B, T_cN can be inquired by a related physical property manual; dielectric constant ε of liquid^L＝a+bT+cT²+dT³Specific numerical values of the constants a, b and c are inquired by a related physical property manual; gas dielectric constant ε^G＝1+(N_A/v^Gε₀)(α+μ²/3kT), wherein ε₀Is a vacuum dielectric constant of ∈₀＝8.8542×10^-12F/m，N_AIs an Avogastron constant, N_A＝6.022×10²³mol^-1K is Boltzmann constant, k is 1.381 × 10^-23J/K, alpha and mu are respectively the polarizability of the substance and the dielectric constant, and the specific numerical values of the polarizability and the dielectric constant can be inquired by a related physical property manual.

The implicit function equation of the formula (3) is solved by a numerical method, so that the change relation of the boiling point of the gas-liquid balance system applying the electrostatic field effect along with the electrostatic field intensity can be obtained.

In this embodiment, the liquid phase material of the gas-liquid equilibrium system may be any dielectric, such as water, ethanol, or toluene, and the following examples are further described below.

The physical property parameters in the formula (3) are shown in Table 1 when the system temperature is 25 ℃. The relationship between the angle θ and the change in vapor pressure and boiling point is shown in FIG. 2. To make the influence of the electrostatic field on the vapor pressure and boiling point of the system 0, it is sufficient to:

the included angle theta can be calculated by the formula (4).

TABLE 1 physical Properties of the respective substances