Method for measuring aromatherapy release characteristic parameters of cylindrical ceramic

Abstract

The invention belongs to the technical field of in-vehicle environment inspection, a cylindrical coordinate physical model of cylindrical ceramic aromatherapy is constructed based on the Fick's law, and high-efficiency and high-precision measurement of volatile organic compound (VOC) release characteristic parameters is realized. The method comprises the following steps: establishing a mass transfer model of VOC in cylindrical aromatherapy under a cylindrical coordinate system; placing aromatherapy in a ventilation experiment module for free release, and measuring the hourly concentration of VOC in the experiment module; a numerical solution is solved by combining a finite element method, experimental data are combined, and three characteristic parameters, namely initial concentration, a diffusion coefficient and a distribution coefficient, in the release process are obtained through inversion by adopting a particle swarm coupling ant colony algorithm. The device is simple in structure, convenient to operate, low in cost and suitable for laboratory detection and engineering evaluation and optimization of vehicle-mounted aromatherapy products.

Description

Technical Field

[0001] This invention belongs to the field of in-vehicle environment testing technology. Based on Fick's law, a cylindrical coordinate physical model of a cylindrical ceramic aromatherapy diffuser is constructed to achieve efficient and high-precision measurement of volatile organic compound release characteristic parameters. Background Technology

[0002] As a crucial mode of transportation for travel and tourism, people spend approximately 6.5% of their time daily in the relatively small, enclosed space of a car, with drivers spending over 50% of that time. This makes in-car air quality issues caused by volatile organic compounds (VOCs) a global concern. In-car fragrances have gained widespread attention due to their ability to improve in-car air quality, regulate mood, and alleviate fatigue, thereby enhancing the driving experience and passenger comfort. Fragrance products release significant amounts of VOCs, with 3-carene, γ-terpinene, β-myrcene, α-terpineol, eucalyptol, and linalool being common aromatic components. While these components possess potential benefits such as anti-tumor, antibacterial, neuroprotective, and anti-anxiety properties, their continuous release and accumulation may lead to respiratory irritation, oxidative stress, and even potential sensitization or carcinogenic risks. Currently, most studies still use constant release rate or exponential decay models to describe the VOC release process of fragrance products. These simplified models fail to reflect the dynamic changes in release rates in real-world environments, limiting the accurate assessment and control of the health risks of fragrance products. To address this issue, this method establishes a VOC release model for cylindrical aromatherapy diffusers in cylindrical coordinates based on mass transfer, systematically considering multiple control mechanisms including internal diffusion, interfacial distribution, and surface convection. Furthermore, based on this model, a method for characteristic parameter inversion and measurement is proposed, which can simultaneously obtain the initial concentration C0 and diffusion coefficient D through numerical simulation and experimental data fitting. m The study identifies three characterization parameters: the distribution coefficient K, etc. This research not only provides a more physically meaningful physical model for the dynamic prediction of VOC release from in-vehicle air fresheners, but also offers a methodological framework and technical support for the quantitative analysis of mass transfer behavior in solid materials with complex geometries. Summary of the Invention

[0003] The purpose of this invention is to address the problems of overly simplified VOC mass transfer models for cylindrical car air fresheners, which fail to obtain release characteristic parameters and accurately reflect the actual release process. This invention proposes a method for determining VOC characteristic parameters based on a cylindrical coordinate mass transfer model. This method can simultaneously retrieve the initial VOC concentration C0 and diffusion coefficient D in a cylindrical car air freshener in a single experiment. mThe allocation coefficient K significantly improves the completeness and accuracy of release characterization. This invention also establishes a systematic and standardized experimental scheme, employing finite element numerical solution and particle swarm optimization coupled with ant colony optimization to achieve high-precision fitting. The method features a simple device structure, convenient operation, and low cost, making it suitable for laboratory testing and the engineering evaluation and optimization of in-vehicle aromatherapy products.

[0004] To achieve the above objectives, this invention proposes a method for accurately and simultaneously measuring three release characteristic parameters based on the release process and characteristics of cylindrical air fresheners in a vehicle under ventilated conditions, comprising the following steps:

[0005] 1) Establish a mass transfer model of VOCs in a cylindrical aromatherapy diffuser in cylindrical coordinates, considering multiple mass transfer control mechanisms including diffusion within the diffuser, interfacial distribution, and surface convection. No mass transfer occurs at the top and bottom of the in-vehicle aromatherapy diffuser; the overall mass transfer process is a radially symmetrical process about the axis. Based on this, construct a physical model of the VOC release process of the in-vehicle aromatherapy diffuser in the experimental chamber. Its initial values, boundary conditions, governing equations, and mass conservation equations can be described as follows:

[0006] C m (t=0)=C0 t=0 (1)

[0007] C a =0 t=0 (2)

[0008]

[0009] In this model: C a The concentration of gaseous VOCs in the experimental chamber, in μg / m³ 3 t represents the release time, in seconds; C0 represents the initial concentration of VOCs in the aromatherapy material, in μg / m³. 3 ;D m m is the diffusion coefficient of VOCs in aromatherapy materials. 2 / s; K is the distribution coefficient of VOCs in the aromatherapy material, dimensionless; V is the volume of the experimental chamber, m. 3 A represents the release surface area of ​​the aromatherapy material, in m². 2 R is the radial radius of the aromatherapy material, in meters; h m Let m be the convective mass transfer coefficient. 2 / s; Q is the number of air changes in the experimental chamber, h -1 ;

[0010] 2) The partial differential equations of the cylindrical ceramic aromatherapy mass transfer model in cylindrical coordinates are transformed into a large algebraic system by using the finite element method, and the numerical solution of the mass transfer process is obtained by numerical methods.

[0011] 3) At the beginning of the aroma diffusion experiment, first clean the inner wall of the experimental chamber with alcohol, and then open the high-pressure gas cylinder to blow away the residual pollutants in the chamber with clean air;

[0012] 4) Set the gas temperature and humidity in the experimental chamber to the required values, with a temperature control accuracy of ±0.5℃ and a humidity control accuracy of ±5%.

[0013] 5) Keep the clean air flow rate constant, place the car air freshener in the test chamber to allow it to release freely, and turn on the fan to mix the VOCs in the chamber evenly.

[0014] 6) During the aroma release process, a VOC sampling device is connected to the outlet of the experimental chamber to collect gaseous VOCs and obtain the hourly concentration C of VOCs in the experimental chamber. a .

[0015] 7) The established numerical mass transfer model was combined with the measured VOC concentration data in the ventilation chamber to perform inversion calculations to determine the model's characteristic parameters. A particle swarm optimization-ant colony optimization algorithm was used to improve the stability and accuracy of the parameter solution. Finally, three release characteristic parameters were obtained: the initial concentration C0, the diffusion coefficient D, and the VOC concentration C0. m And the allocation coefficient K.

[0016] Features and effects of the present invention:

[0017] To address the simplification issues in existing cylindrical in-vehicle aromatherapy mass transfer models and the technical limitations in accurately characterizing the release process by obtaining release parameters experimentally, this invention establishes a cylindrical coordinate physical model for aromatherapy based on Fick's law. The partial differential equations are transformed into a large-scale linear algebraic system using the finite element method, and numerical solutions are obtained through numerical methods. Furthermore, by combining nonlinear fitting with a particle swarm optimization algorithm, hourly monitoring data of pollutant concentrations within the ventilation chamber are processed, thereby accurately and synchronously determining three release characteristic parameters of the pollutant release process in in-vehicle aromatherapy: initial concentration, diffusion coefficient, and distribution coefficient. This method features simple experimental equipment and operation, low cost, and high solution accuracy, making it suitable for laboratory testing and engineering applications. Attached Figure Description

[0018] Figure 1 Diagram of the testing system for the release of pollutants from a cylindrical vehicle-mounted air freshener inside the experimental chamber.

[0019] Figure 2 The nonlinear fitting result of formaldehyde concentration Detailed Implementation

[0020] The method proposed in this invention for accurately and simultaneously determining the three major release characteristics of volatile organic compounds (VOCs) in cylindrical ceramic aromatherapy diffusers is described in detail below with reference to the accompanying drawings and examples:

[0021] The testing system for the VOC release process of the cylindrical ceramic aromatherapy diffuser of the present invention is as follows: Figure 1As shown, the VOC mass transfer characteristic parameter testing system in aromatherapy materials consists of four parts: an air intake system, a temperature and humidity control system, a sampling system, and an experimental chamber. The air intake system comprises a high-pressure gas cylinder 1 with a pressure reducing valve, a valve 2, and a mass flow controller 3; the temperature and humidity control system comprises a sealed chamber 4 filled with purified water, a three-way valve 5, an empty sealed chamber 6, a temperature and humidity monitor 7, and a constant temperature water bath 9, used to regulate and control the temperature and humidity of the air inside the experimental chamber 10; the sampling system comprises an INNOVA-1214i acoustic-optical multi-component gas analyzer 8 and a computer 11, used to monitor the formaldehyde concentration in the experimental chamber hourly. The release characteristic parameter determination method in this example includes the following steps:

[0022] 1) Establish a physical model of the VOC release process of the vehicle-mounted air freshener in the experimental chamber. Its initial values, boundary conditions, governing equations, and mass conservation equations can be described as follows:

[0023] C m (t=0)=C0 t=0 (1)

[0024] C a =0 t=0 (2)

[0025]

[0026]

[0027] In this model: C a The concentration of gaseous VOCs in the experimental chamber, in μg / m³ 3 t represents the release time, in seconds; C0 represents the initial concentration of VOCs in the aromatherapy material, in μg / m³. 3 ;D m m is the diffusion coefficient of VOCs in aromatherapy materials. 2 / s; K is the distribution coefficient of VOCs in the aromatherapy material, dimensionless; V is the volume of the experimental chamber, m. 3 A represents the release surface area of ​​the aromatherapy material, in m². 2 R is the radial radius of the aromatherapy material, in meters; h m Let m be the convective mass transfer coefficient. 2 / s; Q is the number of air changes in the experimental chamber, h -1 ;

[0028] 2) The partial differential equations of the cylindrical ceramic aromatherapy mass transfer model in cylindrical coordinates are transformed into a large algebraic system by using the finite element method, and the numerical solution of the mass transfer process is obtained by numerical methods.

[0029] 3) At the beginning of the aroma diffusion experiment, first clean the inner wall of the experimental chamber with alcohol, and then open the high-pressure gas cylinder to blow away the residual pollutants in the chamber with clean air at a flow rate of 500ml / min for about 4-5 hours;

[0030] 4) Set the gas temperature inside the experimental chamber to 25℃, with a temperature control accuracy of ±0.5℃ and a humidity control accuracy of ±5%.

[0031] 5) Keep the clean air flow rate constant, place the car air freshener in a 30L test chamber to allow it to release freely, and turn on the fan to mix the VOCs in the chamber evenly while conducting the test.

[0032] 6) During the free release of the aromatherapy, an INNOVA-1412i gas monitor (measuring range 0.04-400ppm) was connected to the outlet of the experimental chamber to collect formaldehyde gas at 2-minute intervals, obtaining the hourly concentration C of formaldehyde in the experimental chamber. a .

[0033] 7) The established numerical mass transfer model was combined with the measured VOC concentration data in the ventilation chamber to perform inversion calculations to determine the model's characteristic parameters. A particle swarm optimization-ant colony optimization algorithm was used to improve the stability and accuracy of the parameter solution. Finally, the values ​​of the three release characteristic parameters were obtained, with the initial concentration C0 being 4.08 × 10⁻⁶. 8 μg / m 3 diffusion coefficient D m 1.31×10 -12 m 2 / s, with a distribution coefficient K of 141000.

[0034] The principle of this invention: When the cylindrical ceramic aromatherapy diffuser is freely released in the experimental chamber, the hourly concentration of formaldehyde in the experimental chamber is obtained by sampling at different times through sampling equipment. The concentration data measured in the experiment is processed and combined with a numerical mass transfer model to carry out inversion calculation to determine the model characteristic parameters. A particle swarm optimization algorithm-ant colony optimization algorithm is used to improve the stability and accuracy of parameter solution. Thus, the initial concentration, diffusion coefficient and distribution coefficient of VOC of car aromatherapy can be accurately obtained at the same time.

Claims

1. A method for determining the aroma release characteristic parameters of cylindrical ceramic diffusers, comprising the following steps: 1) Establish a mass transfer model of VOC in a cylindrical aroma diffuser in a cylindrical coordinate system. The system considers multiple mass transfer control mechanisms such as diffusion inside the aroma diffuser, interface distribution and surface convection. There is no mass transfer at the top and bottom of the car aroma diffuser. The overall mass transfer process is a radial mass transfer process that is symmetrical about the axis. Based on this, a physical model of the VOC release process of the vehicle-mounted air freshener inside the experimental chamber is constructed. Its initial values, boundary conditions, governing equations, and mass conservation equations can be described as follows: C m (t=0)=C0 t=0 (1) C a =0 t=0 (2) In this model: C a The concentration of gaseous VOCs in the experimental chamber, in μg / m³ 3 t represents the release time, in seconds; C0 represents the initial concentration of VOCs in the aromatherapy material, in μg / m³. 3 ; D m Let m be the diffusion coefficient of VOCs in aromatherapy materials. 2 / s; K is the distribution coefficient of VOCs in the aromatherapy material, which is dimensionless; V is the volume of the experimental chamber, in meters. 3 A represents the release surface area of ​​the aromatherapy material, in m². 2 R is the radial radius of the aromatherapy material, in meters; h m Let m be the convective mass transfer coefficient. 2 / s; Q is the number of air changes in the experimental chamber, h -1 ; 2) The partial differential equations of the cylindrical ceramic aromatherapy mass transfer model in cylindrical coordinates are transformed into a large algebraic system by using the finite element method, and the numerical solution of the mass transfer process is obtained by numerical methods. 3) At the beginning of the aroma diffusion experiment, first clean the inner wall of the experimental chamber with alcohol, and then open the high-pressure gas cylinder to blow away the residual pollutants in the chamber with clean air at a flow rate of 500ml / min for about 4-5 hours; 4) Set the gas temperature inside the experimental chamber to 25℃, with a temperature control accuracy of ±0.5℃ and a humidity control accuracy of ±5%. 5) Keep the clean air flow rate constant, place the car air freshener in a 30L test chamber to allow it to release freely, and turn on the fan to mix the VOCs in the chamber evenly while conducting the test. 6) During the aroma release process, a VOC sampling device is connected to the outlet of the experimental chamber to collect gaseous VOCs and obtain the hourly concentration C of VOCs in the experimental chamber. a . 7) The established numerical mass transfer model was combined with the measured VOC concentration data in the ventilation chamber to perform inversion calculations to determine the model's characteristic parameters. A particle swarm optimization-ant colony optimization algorithm was used to improve the stability and accuracy of the parameter solution. Finally, three release characteristic parameters were obtained: the initial concentration C0, the diffusion coefficient D, and the VOC concentration C0. m And the allocation coefficient K.

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