Method and device for measuring Joule-Thomson coefficient of hydrocarbon fuel and cracking product thereof

Abstract

The invention discloses a method for measuring Joule-Thomson coefficients of hydrocarbon fuel and cracking products thereof. The method comprises the following steps: pumping a target substance into an experimental tube, and heating from room temperature to target temperature; monitoring the temperature of the target substance at the inlet and outlet of the experiment tube, the wall surface temperature distribution of the experiment tube, the system pressure at two ends of the experiment tube, and current and voltage applied to two ends of the experiment tube in real time; according to the parameters monitored in real time, a function H (T) of the constant-pressure enthalpy value of the target substance changing along with the temperature is obtained on line based on a calorimetric model; when cooling to room temperature, changing the pressure and continuing the steps to obtain H (T) under different pressures; and based on H (T) under different pressures, establishing a Joule-Thomson coefficient calculation model containing a pressure-temperature-constant pressure enthalpy value function relationship, and calculating the change condition of the Joule-Thomson coefficient of the target substance along with the temperature. The invention further discloses a corresponding measuring device. According to the method and the device, accurate measurement of the Joule-Thomson coefficient is realized.

Description

Technical Field

[0001] The invention relates to the technical fields of thermodynamics, calorimetry, supercritical fluid and throttling expansion of hydrocarbon fuels, and in particular to a method and device for measuring the Joule-Thomson coefficient of hydrocarbon fuels and cracking products thereof. Background Art

[0002] As the international situation becomes increasingly complex and the competition in science and technology becomes increasingly fierce, the research and development of hypersonic aircraft has become one of the key research directions of major aerospace powers. The poor performance of the aircraft thermal management system is one of the key issues restricting the development of hypersonic aircraft. Active regenerative cooling technology that uses high-density hydrocarbon fuel as a combustible coolant to construct a physical and chemical heat exchange system has emerged. Before entering the combustion chamber for combustion, high-density hydrocarbon fuel relies on the heat exchange circulation pipeline to cool down the surface of the high-temperature parts of the fuselage in a forced convection heat exchange manner to protect the scramjet engine. The fuel will undergo thermal cracking reaction under high temperature and high pressure environment. The coke produced by the thermal cracking of the fuel adheres to the surface of the circulation pipeline, which will cause internal blockage of the pipeline and further increase the fuel flow pressure. The internally blocked pipeline will become a throttling channel, and the fuel will have a significant throttling expansion effect after flowing through the throttling channel and spraying into the combustion chamber. The liquid-like and gas-like compressed in the supercritical state will rapidly expand into the low-pressure pipeline, causing a significant pressure drop and temperature difference in the pipeline, which will cause great safety hazards to the safe flight of the aircraft. The Joule-Thomson coefficient reflects the change of temperature with pressure of gas after the throttling expansion process, which is of great significance for studying the throttling expansion effect caused by coke blockage of fuel.

[0003] At present, experimental measurement of relevant physical parameters combined with EOS state equation calculation is the main means to obtain the Joule-Thomson coefficient of fuel.

[0004] Teresa Regueira et al. calculated the Joule-Thomson coefficient of various normal alkanes (n-hexane, n-octane, n-decane, n-dodecane, n-tetradecane and n-hexadecane) at 0.1-10MPa and 323.15K-483.15K (Teresa Regueira, Farhad Varzandeh, Erling Stenby. Heat Capacity and Joule-Thomson Coefficient of Selected n-Alkanes at 0.1 and 10MPa in Broad Temperature Ranges [J]. The Journal of Chemical Thermodynamics, 2017, 111, 250-264.). This method requires the use of a Calvet differential calorimeter to measure the isobaric heat capacity of the target substance in advance, and then the EOS model is used to correlate the constant-pressure specific heat and the Joule-Thomson coefficient. EOS models include Soave-Redlich-Kwong, Peng-Robinson, Perturbed Chain Statistical Associating Fluid Theory and Soave-Benedict-Webb-Rubin, etc. Nabil Al-Bizreh, etc. [2-4]A flow calorimeter that can simulate the throttling expansion process of a fluid was designed. The Joule-Thomson coefficients of acetone, chloroform, benzene, cyclohexane, n-hexane, n-heptane and n-octane in the temperature range of 313.15-393.15K were measured (Nabil Albizreh, Christopher Wormald. The Isothermal Joule-Thomson Coefficients of Benzene and Cyclohexane[J]. The Journal of Chemical Thermodynamics, 1977, 9, 749-764. Nabil Albizreh, Christopher Wormald. The Isothermal Joule-Thomson Coefficient of Acetone and of Chloroform[J]. The Journal of Chemical Thermodynamics, 1979, 11, 1127-1136.). Gao Ming et al. designed a device for measuring the Joule-Thomson coefficient of gas. They used the device to measure the changes in the Joule-Thomson coefficient of binary mixtures (CO2, N2) with different molar compositions in the temperature range of 298.15-423.15K, and combined the Eos model to carry out calculations to verify the accuracy of the experimental data (Gao Ming, Wang Lin, Chen Xiao. Joule-Thomson Effect on a CCS-Relevant (CO2+N2) System[J]. ACS Omega, 2021, 6, 9857-9867.).Hailong She et al. used the microchannel JT cryocooler as a prototype and used simulation technology to study the temperature and Joule-Thomson coefficient distribution of the fluid in the throttling channel, proving that appropriately reducing the friction loss of the throttling channel helps to improve the refrigeration capacity of the fluid (Hai She, Xiao Cui, Jian Weng. Study on the Influence of Distributed Joule-Thomson Effect on the Performance of Microchannel Cryocooler [J]. Applied Thermal Engineering, 2022, 21, 2575-2584.). Cai Zhang et al. used computational fluid dynamics (CFD) models and isentropic models to investigate the feasibility of hydrogen mixed with natural gas in pipeline transportation. With the increase of hydrogen molar content, the temperature in the hydrogen-blended natural gas pipeline increases linearly, and the Joule-Thomson coefficient decreases linearly (Cai Zhang, Zhuo Li, Chang Li. Insight into the Effects of Hydrogen on Inside-Valve Flow and Joule-Thomson Characteristics of Hydrogen-Blended Natural Gas: A Numerical Study [J]. International Journal of Hydrogen Energy, 2024, 49, 1056-1074.).

[0005] In summary, the existing experimental measurement methods and EOS models are only suitable for the measurement and prediction of the Joule-Thomson coefficient of single-component and binary components in the low temperature range. Summary of the invention

[0006] The purpose of the present invention is to provide a method and device for measuring the Joule-Thomson coefficient of hydrocarbon fuels and their cracking products, thereby realizing accurate measurement of the Joule-Thomson coefficient.

[0007] The present invention provides the following technical solutions:

[0008] A method for measuring the Joule-Thomson coefficient of hydrocarbon fuels and cracking products thereof, the method comprising:

[0009] (1) Pump the target substance into the experimental tube and heat it from room temperature to the target temperature;

[0010] (2) Real-time monitoring of the temperature of the target substance at the inlet and outlet of the experimental tube, the temperature distribution of the experimental tube wall, the system pressure at both ends of the experimental tube, and the current and voltage applied to both ends of the experimental tube;

[0011] (3) obtaining online, based on the parameters monitored in real time in step (2), a function of the constant pressure enthalpy of the target substance changing with temperature based on a calorimetric model;

[0012] (4) When the experimental tube cools down to room temperature, the pressure is changed and the above steps (1) to (3) are continued to obtain the function of the constant pressure enthalpy of the target substance changing with temperature at different pressures;

[0013] (5) Based on the function of the constant-pressure enthalpy value of the target substance changing with temperature under different pressures, a Joule-Thomson coefficient calculation model including the functional relationship between pressure, temperature and constant-pressure enthalpy value is established to calculate the change of the Joule-Thomson coefficient of the target substance with temperature.

[0014] The technical concept of the present invention is as follows: the present invention establishes a functional relationship between the temperature and enthalpy value of a fuel and its cracking product under isobaric conditions based on a calorimetric model; the pressure of an experimental system is changed by a pressure regulating valve to establish a functional relationship between the pressure and enthalpy value of the fuel and its cracking product under isothermal conditions; the present invention uses a Joule-Thomson calculation model to establish a fuel temperature-fuel pressure functional relationship under isothermal conditions based on the functional relationship between the pressure, temperature and enthalpy value of the fuel and its cracking product, thereby obtaining the change of the Joule-Thomson of the fuel and its cracking product with temperature.

[0015] In order to avoid the environmental requirements of adiabatic expansion and complex parameter calculations in the EOS state equation required in previous Joule-Thomson coefficient measurement methods, the present invention proposes a new method for calculating the Joule-Thomson coefficient based on distributed flow calorimetry and fuel enthalpy. The measured physical parameters are the fuel enthalpy and the Joule-Thomson coefficient. The accurate measurement of the Joule-Thomson coefficient is the basis for studying the laws of fuel flow heat transfer and examining the safety of fuel transportation. Therefore, the present invention is of great significance to the basic research on hydrocarbon fuels.

[0016] The measurement method provided by the present invention is distributed flow calorimetry.

[0017] The target substance may be a single component or multiple components, including but not limited to small molecule gases and liquids.

[0018] In step (1), the target substance is selected from small molecule gases and / or liquids.

[0019] The small molecule gas may be one of hydrogen, gaseous alkanes, gaseous alkenes, gaseous alkynes, or a combination of at least two thereof; the liquid may be one of alkanes, olefins, cycloalkanes, cycloolefins, or aromatic hydrocarbons, or a combination of at least two thereof.

[0020] Further, in step (1), the target substance is pumped into the experimental tube at a flow rate of 0.1-10 g / s or 1-1000 ml / s, the target temperature is 298-1173 K, and the heating rate is 5-25 K / min.

[0021] Furthermore, in step (3), the calorimetric model is used to calculate the energy required for heating the hydrocarbon fuel, including an experimental tube microelement input energy model, an experimental tube microelement to environment heat transfer model, a copper electrode to environment heat transfer model, and an experimental tube microelement to fuel heat transfer model;

[0022] The experimental tube microelement is to divide the experimental tube with a length of x meters into n experimental tube segments with a length of Δx during calculation;

[0023] The experimental tube microelement input energy model is obtained by pre-calibrating the function of the experimental tube resistance changing with temperature, and allocating the voltage across the experimental tube microelement in combination with the experimental tube wall temperature distribution; calculating the experimental tube microelement input energy according to the experimental tube microelement voltage value and current value, recorded as P x,total ;

[0024] The heat transfer model of the experimental tube microelement to the environment is obtained by pre-calibrating the function of the heat convection and heat radiation energy of the experimental tube microelement wall with the temperature of the experimental tube wall, denoted as P x,loss ;

[0025] The heat transfer model from the copper electrode to the environment is obtained by carrying out a standard fluid flow heat transfer experiment, calibrating the function of the copper electrode heat loss as the fuel temperature changes, and evenly dividing it into each calculation microelement, denoted as P x,electrode ;

[0026] The heat transfer model from the experimental tube microelement to the fuel is obtained by the following method: Establish the heat conservation equation between each model, that is, P x,total -P x,electrode =P x,loss +P x,fluid , P x,fluid is the energy transferred from the experimental tube microelement to the fuel;

[0027] The function of the constant pressure enthalpy value of the target substance changing with temperature is H(T)=P fluid / m=∑P x,fluid / m, where m is the mass of the target substance.

[0028] Among them, in the heat transfer model from copper electrode to environment, the standard fluids are water, toluene, p-xylene, cyclohexane, etc.

[0029] Furthermore, in step (5), the Joule-Thomson coefficient calculation model includes a function H(T) of the constant-pressure enthalpy value of the target substance under isobaric conditions as a function of temperature; a function H(p) of the enthalpy value of the target substance under isothermal conditions as a function of pressure; a function T(p) of the temperature of the target substance under isothermal conditions as a function of pressure; and a first-order derivative function μ of the temperature of the target substance under isothermal conditions as a function of pressure. J-T =(αT / αp) H .

[0030] Furthermore, the measuring method includes recovering the pyrolysis gas and pyrolysis liquid of the target substance.

[0031] The present invention also provides a measuring device for the Joule-Thomson coefficient of the above method, the measuring device comprising:

[0032] A fuel constant pressure transport module, comprising a large-flow double-plunger high-pressure constant-flow pump and a liquid gear flowmeter, wherein the large-flow double-plunger high-pressure constant-flow pump is used to pump the target substance into the calorimetric module, and the liquid gear flowmeter is used to detect the stable state of the flow;

[0033] The calorimetric module includes a DC regulated power supply and an experimental tube. The DC regulated power supply is used to apply stable energy to the experimental tube. The experimental tube is used as a fluid flow heat exchange platform. The pumped target substance is heated from room temperature to the target temperature in the experimental tube.

[0034] The temperature-pressure acquisition module includes a thermocouple, an infrared thermal imager, a pressure sensor, and a pressure regulating valve, which is used to monitor the temperature of the target substance at the inlet and outlet of the experimental tube, the temperature distribution of the wall of the experimental tube, the system pressure at both ends of the experimental tube, and adjust the pressure in real time;

[0035] The fuel recovery module includes a gas-liquid separation device, an exhaust gas treatment device, and a waste liquid storage tank, which are used to separate and recover the cracked gas and cracked liquid of the target substance;

[0036] The data storage and processing module includes a temperature-pressure multi-channel data collector, a current and voltage data collector, a memory, and a central processing unit. The temperature-pressure multi-channel data collector and the current and voltage collector transmit the parameters monitored in real time by the temperature-pressure acquisition module to the memory and the central processing unit for executing steps (3) and (5).

[0037] The beneficial effects of the present invention are:

[0038] (1) This method establishes a Joule-Thomson calculation model that includes the functional relationship between pressure, temperature and enthalpy. With the help of experimental measurement methods, distributed calculations are carried out on the Joule-Thomson coefficients of hydrocarbon fuels with hundreds of components and their cracking products. The experimental measurable temperature range is increased from low temperature to high temperature (298K-1173K). It provides data support for studying the flow heat transfer mechanism and chemical thermodynamic mechanism of hydrocarbon fuels, and provides testing and evaluation methods for the development of new hydrocarbon fuels.

[0039] (2) This method avoids the difficult-to-achieve and quantify conditions required in traditional experimental measurement methods, such as adiabatic and throttling expansion, and avoids the situation where the numerical calculation model only satisfies the measurement and prediction of the Joule-Thomson coefficient of single and binary components in the low temperature range. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A flow chart of a method for measuring the Joule-Thomson coefficient of hydrocarbon fuels and their cracking products;

[0041] Figure 2 is a schematic diagram of the structure of the measuring device;

[0042] Figure 3 is the energy of heat transfer from each experimental tube microelement of toluene (3MPa) to the fuel;

[0043] Figure 4 The variation trend of toluene heat sink with pressure and temperature;

[0044] Figure 5 This is the change of temperature with pressure under the condition of isenthalpy of toluene;

[0045] Figure 6 is the Joule-Thomson coefficient of toluene (3MPa). DETAILED DESCRIPTION

[0046] The following examples can enable professionals to more fully understand the present invention, but do not limit the present invention in any way.

[0047] The present invention provides a method for measuring the Joule-Thomson coefficient of hydrocarbon fuel and its cracking product. Figure 1 The structural diagram of the measuring device is shown in Figure 2 As shown, (1) is a fuel constant pressure transport module, (2) is a calorimetric module, (3) is a temperature-pressure acquisition module, (4) is a fuel recovery module, and (5) is a data storage and processing module.

[0048] The method for measuring the Joule-Thomson coefficient of hydrocarbon fuel and its cracking product by using the measuring device provided by the present invention comprises:

[0049] (1) The fuel constant pressure transport module pumps the target substance into the experimental tube in the calorimetric module through a large-flow double-plunger high-pressure constant-current pump and raises the temperature from room temperature to the target temperature; during the pumping process, a liquid gear flowmeter is used to detect the flow stability; the DC regulated power supply in the calorimetric module applies stable energy to the experimental tube.

[0050] (2) A temperature-pressure acquisition module including a thermocouple, an infrared thermal imager, a pressure sensor, and a pressure regulating valve monitors in real time the temperature of the target substance at the inlet and outlet of the experimental tube, the temperature distribution of the wall of the experimental tube, the system pressure at both ends of the experimental tube, and the current and voltage applied to both ends of the experimental tube.

[0051] (3) The data storage and processing module obtains the function of the constant pressure enthalpy value of the target substance changing with temperature online based on the calorimetric model according to the parameters monitored in real time in step (2).

[0052] (4) When the temperature of the measuring device is lowered to room temperature, the pressure is changed and the above steps (1) to (3) are continued to obtain a function of the constant-pressure enthalpy value of the target substance changing with temperature at different pressures.

[0053] (5) Based on the function of the constant-pressure enthalpy value of the target substance changing with temperature under different pressures, a Joule-Thomson coefficient calculation model including the functional relationship between pressure, temperature and constant-pressure enthalpy value is established to calculate the change of the Joule-Thomson coefficient of the target substance with temperature.

[0054] Example 1

[0055] In this embodiment, the calorimetric model used includes:

[0056] The experimental tube microelement input energy P x,total :Pre-calibrate the function of the test tube resistivity changing with temperature, ρ=0.34+4.31528×10 -5 ×T w ; T w is the pipe wall temperature; the voltage across the experimental pipe microelement is allocated based on the experimental pipe wall temperature distribution, P x,total =U x I.

[0057] Heat transfer model from experimental tube to environment x,loss : When the temperature of the experimental tube without fluid is raised, the energy conservation equation is established, and the empirical formula obtained by fitting the experimental data is:

[0058] P x,loss =-0.16+8.24×10 -4 ×T w -1.45×10 -6 ×T w 2 +1.29×10 -9 ×Tw 3 -9.46×10 -14 ×T w 4

[0059] Heat transfer model from copper electrode to environment P x,electrode : Conduct flow heat transfer experiments on standard fluids such as water, toluene, p-xylene, and cyclohexane, calibrate the change of copper electrode heat loss with fuel temperature, and divide it equally into each calculation microelement. The empirical formula fitted by the experimental data is:

[0060] P x,electrode =-0.019+7.82×10 -5 ×T w -9.81×10 -8 ×T w 2 +1.89×10 -10 ×T w 3 -8.99×10 -14 ×T w 4

[0061] The energy P transferred from the experimental tube microelement to the fuel x,fluid : Establish the heat conservation equation between each model, that is, P x,total -P x,electrode =P x,loss +P x,fluid ;

[0062] like Figure 3 Shown is the energy transferred from each experimental tube element to the fuel.

[0063] In this embodiment, taking toluene as an example, toluene is pumped to the calorimetric module through the constant pressure transport module under the working conditions of 1g / s and 0.1MPa. The calorimetric module gradually heats the toluene from 298K to 1073K, and the heating step is 10K / min to maintain a stable flow heat exchange state of toluene. The temperature-pressure acquisition module monitors the inlet and outlet temperature and pressure of the calorimeter tube, and the temperature changes of the calorimeter tube wall in real time. When the toluene temperature reaches 1073K, the calorimetric experiment is stopped and the toluene heating calorimetric experiment under different pressures is continued after the calorimeter tube temperature drops to room temperature, and the pressure step is controlled to be 0.2MPa. The data processing system obtains the changing trend of the toluene heat sink with pressure and temperature based on the calorimetric model, such as Figure 4 When the pressure is 3MPa, the empirical formula fitted by the experimental data is:

[0064] When 373K<T<570K, H1=297.48+0.59c×T-2.45×10 -4 ×T 2(R=0.99)

[0065] When 570K≤T<1073K, H2=257.77+0.42×T-1.65×10 -5 ×T 2 (R=0.99).

[0066] The isenthalpic curves of hydrocarbon fuels and their cracking products are as follows: Figure 5 Taking toluene as an example, the variation trend of toluene heat sink with pressure and temperature was obtained through Example 1. Figure 5 The temperature changes with pressure under the condition of isenthalpy of toluene. When the enthalpy value is 1MJ / kg, the empirical formula fitted by the experimental data is: T = 638.46 + 7.28 × p - 0.0052 × p 2 (R=0.95).

[0067] The Joule-Thomson coefficient of hydrocarbon fuels and their cracking products varies with temperature. Figure 6 As shown. Taking toluene as an example, based on the above-mentioned toluene isenthalpic conditions, the temperature changes with pressure, and the change of (αT / αP) under isenthalpic conditions is calculated, which is the Joule-Thomson coefficient. When p = 3MPa, 570K≤T<1073K, the empirical formula fitted by the experimental data is:

[0068] μ J-T =1155.86-5.53·T+0.0099·T 2 -7.97 10 -6 ·T 3 +2.38·10 -9 ·T 4 (R=0.98)

[0069] The relative error between the experimental measurement value of the Joule-Thomson coefficient and the NIST theoretical value is less than 6%, and the relative measurement uncertainty is ±2%.

Claims

1. A method for measuring the Joule-Thomson coefficient of hydrocarbon fuels and their cracking products, characterized in that: The method comprises: (1) Pump the target substance into the experimental tube and heat it from room temperature to the target temperature; (2) Real-time monitoring of the temperature of the target substance at the inlet and outlet of the experimental tube, the temperature distribution of the experimental tube wall, the system pressure at both ends of the experimental tube, and the current and voltage applied to both ends of the experimental tube; (3) obtaining online, based on the parameters monitored in real time in step (2), a function of the constant pressure enthalpy of the target substance changing with temperature based on a calorimetric model; (4) When the experimental tube cools down to room temperature, the pressure is changed and the above steps (1) to (3) are continued to obtain the function of the constant pressure enthalpy of the target substance changing with temperature at different pressures; (5) Based on the function of the constant-pressure enthalpy value of the target substance changing with temperature under different pressures, a Joule-Thomson coefficient calculation model including the functional relationship between pressure, temperature and constant-pressure enthalpy value is established to calculate the change of the Joule-Thomson coefficient of the target substance with temperature.

2. The method for measuring the Joule-Thomson coefficient of hydrocarbon fuels and their cracking products according to claim 1, characterized in that: In step (1), the target substance is selected from small molecule gases and / or liquids.

3. The method for measuring the Joule-Thomson coefficient of hydrocarbon fuels and their cracking products according to claim 2, characterized in that: The small molecule gas is selected from one or a combination of at least two of hydrogen, gaseous alkanes, gaseous alkenes, and gaseous alkynes, and the liquid is selected from one or a combination of at least two of alkanes, alkenes, cycloalkanes, cycloalkenes, and aromatic hydrocarbons.

4. The method for measuring the Joule-Thomson coefficient of hydrocarbon fuels and their cracking products according to claim 1, characterized in that: In step (1), the target substance is pumped into the experimental tube at a flow rate of 0.1-10 g / s or 1-1000 ml / s, the target temperature is 298-1173 K, and the heating rate is 5-25 K / min.

5. The method for measuring the Joule-Thomson coefficient of hydrocarbon fuels and their cracking products according to claim 1, characterized in that: In step (3), the calorimetric model is used to calculate the energy required for heating the hydrocarbon fuel, including the experimental tube micro-element input energy model, the experimental tube micro-element to environment heat transfer model, the copper electrode to environment heat transfer model, and the experimental tube micro-element to fuel heat transfer model; The experimental tube microelement is to divide the experimental tube with a length of x meters into n experimental tube segments with a length of Δx during calculation; The experimental tube microelement input energy model is obtained by pre-calibrating the function of the experimental tube resistance changing with temperature, and allocating the voltage across the experimental tube microelement in combination with the experimental tube wall temperature distribution; calculating the experimental tube microelement input energy according to the experimental tube microelement voltage value and current value, recorded as P x,total ; The heat transfer model of the experimental tube microelement to the environment is obtained by pre-calibrating the function of the heat convection and heat radiation energy of the experimental tube microelement wall with the temperature of the experimental tube wall, denoted as P x,loss ; The heat transfer model from the copper electrode to the environment is obtained by carrying out a standard fluid flow heat transfer experiment, calibrating the function of the copper electrode heat loss as the fuel temperature changes, and evenly dividing it into each calculation microelement, denoted as P x,electrode ; The heat transfer model from the experimental tube microelement to the fuel is obtained by the following method: Establish the heat conservation equation between each model, that is, P x,total -P x,electrode =P x,loss +P x,fluid , P x,fluid is the energy transferred from the experimental tube microelement to the fuel; The function of the constant pressure enthalpy value of the target substance changing with temperature is H(T)=P fluid / m=∑P x,fluid / m, where m is the mass of the target substance.

6. The method for measuring the Joule-Thomson coefficient of hydrocarbon fuels and their cracking products according to claim 1, characterized in that: In step (5), the Joule-Thomson coefficient calculation model includes the function H(T) of the constant pressure enthalpy value of the target substance under isobaric conditions as a function of temperature; the function H(p) of the enthalpy value of the target substance under isothermal conditions as a function of pressure; the function T(p) of the temperature of the target substance under isothermal conditions as a function of pressure; the first-order derivative function μ of the temperature of the target substance under isothermal conditions as a function of pressure; J-T =(αT / αp) H .

7. The method for measuring the Joule-Thomson coefficient of hydrocarbon fuels and their cracking products according to claim 1, characterized in that: The measuring method comprises recovering the cracking gas and cracking liquid of the target substance.

8. A device for measuring the Joule-Thomson coefficient using the method according to any one of claims 1 to 7, characterized in that: The measuring device comprises: A fuel constant pressure transport module, comprising a large-flow double-plunger high-pressure constant-flow pump and a liquid gear flowmeter, wherein the large-flow double-plunger high-pressure constant-flow pump is used to pump the target substance into the calorimetric module, and the liquid gear flowmeter is used to detect the stable state of the flow; The calorimetric module includes a DC regulated power supply and an experimental tube. The DC regulated power supply is used to apply stable energy to the experimental tube. The experimental tube is used as a fluid flow heat exchange platform. The pumped target substance is heated from room temperature to the target temperature in the experimental tube. The temperature-pressure acquisition module includes a thermocouple, an infrared thermal imager, a pressure sensor, and a pressure regulating valve, which is used to monitor the temperature of the target substance at the inlet and outlet of the experimental tube, the temperature distribution of the wall of the experimental tube, the system pressure at both ends of the experimental tube, and adjust the pressure in real time; The fuel recovery module includes a gas-liquid separation device, an exhaust gas treatment device, and a waste liquid storage tank, which are used to separate and recover the cracked gas and cracked liquid of the target substance; The data storage and processing module includes a temperature-pressure multi-channel data collector, a current-voltage data collector, a memory, and a central processing unit. The temperature-pressure multi-channel data collector and the current-voltage data collector transmit the parameters monitored in real time by the temperature-pressure acquisition module to the memory and the central processing unit for executing steps (3) and (5).

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