Study On Device Of Combustion Heat Based On Calvet Principle

Based on Calvet’s principle,this project has successfully developed a new device for measuring the heat of combustion of small-volume energetic materials.The device changed the principle of indirect measurement of water temperature by the traditional water equivalent method,and successfully overcame the shortcomings of the traditional water equivalent method,such as large sample consumption,low test accuracy,complicated experimental operation and high environmental requirements.The device used a thermopile to directly measure the heat generated by the combustion of the sample,and has the advantages of less sample consumption,high test accuracy,simple experimental operation,good stability and repeatability.The instrument is equipped with a complete data recording and processing system,which can continuously record data online to facilitate long-period experiments.The research focus of this topic mainly includes the following three parts:（1）Based on the principle of Calvet,the overall structure design and processing of a new combustion heat measuring device is presented.On the basis of the feasibility of the previous theoretical research,the overall structure of the new combustion heat measurement device is designed reasonably.The device is mainly divided into the following five modules:temperature control system,thermopile calorimetric system,electric energy calibration system,measurement control system,micro oxygen bomb installation.In order to conform to the Tian equation and prevent the experimental error caused by the temperature rise of the external interface of the thermopile,110 L water bath is used for the external cylinder of the constant temperature tank.In order to ensure high temperature control accuracy,the inner cylinder is designed as an aluminum cylinder with 2 mm air interlayer,and the effective volume is 10 L.The temperature is kept at 25℃through the mixing device.The calorimetric system of thermopile consists of 960 pairs of thermocouples,which has high test accuracy and sensitivity.In order to ensure the complete combustion of the sample and the slow release of heat at the moment of combustion,and to obtain the gentle heat flow curve,the micro oxygen bomb device with different structures was designed reasonably in this subject,and finally the stainless steel bullet body with 1.5 mm air layer was selected.（2）Research on the reliability of a new combustion heat measuring device based on Calvet principle.In order to ensure the reliability of the instrument,the constant temperature system and the measurement control system of the device were calibrated.The temperature control accuracy of inner cylinder can reach 0.001℃within 5 hours.From the test results,it can be seen that the measured value and the standard value have good consistency,and the standard deviation of the test can reach 0.0001,so as to ensure the accuracy of the power calibration module.In addition,the calorimetric coefficient of the device was measured by electric energy calibration and chemical calibration.There is a similar phenomenon between electric energy calibration and chemical calibration.The calorimetric coefficient S value increases with the increase of heat source.This is because when the heat is large,the large heat generated cannot be quickly absorbed by the soaking block,the temperature of the soaking block increases,and the E₁ measured by the thermopile is less than the actual e value,resulting in the increase of S value.The calorimetric coefficient S value of electric energy calibration is 53.00,and that of chemical calibration is 46.45.According to the experimental results,the calorimetric coefficients obtained by chemical calibration and electric energy calibration are different because of the different heat transfer modes.（3）The application of a new combustion heat measuring device based on Calvet principle.The combustion heat of benzoic acid and succinic acid was measured by a new combustion heat measuring device.The standard molar combustion enthalpy and the standard molar formation enthalpy were calculated.The experimental results show that the calorific value of benzoic acid is–（26462.904±31.212）J g^–1,the standard molar combustion heat is–（3231.687±3.812）k J mol^–1,the standard molar combustion enthalpy is–（1992.277±3.812）k J mol^–1,and the standard molar formation enthalpy is–（1619.783±3.812）k J mol^–1,which is in good agreement with the standard value.The calorific value of succinic acid is–（12654.450±22.535）J g^–1,the standard molar combustion heat is–（1495.159±3.244）k J mol^–1,the standard molar combustion enthalpy is–（2749.327±3.244）k J mol^–1,the standard molar formation enthalpy is–（936.371±3.244）k J mol^–1,which is in good agreement with the standard value and the reference value.