阅读说明：本技术 燃烧热测定仪的量热系统 (Calorimetric system of combustion heat tester ) 是由 金波 楚士晋 彭汝芳 李晓仪 张青春 黄琪 于 2020-12-31 设计创作，主要内容包括：本发明公开一种燃烧热测定仪的量热系统,该系统包括水柜,柜中充有恒温介质,恒温介质包括但不限于超纯水,在恒温介质环境中,设有一个氧弹量热池和一个参比量热池,在氧弹量热池和参比量热池外围分别套有一个结构和性能完全相同的热电堆,两热电堆反向连接,构成示差量热方式,以抵消寄生热流的影响；所述水柜包括外柜、内柜,所述内柜坐落在外柜中,所述量热池、热电堆均布置在内柜中,内柜的柜壁是夹层结构,夹层内充有空气；所述内柜设有活动连接盖,活动连接盖打开时,内柜和外柜内的恒温介质进行热量交换；活动连接盖关闭时,内柜和外柜通过空气层进行热量交换。(The invention discloses a calorimetric system of a combustion heat tester, which comprises a water tank, wherein a constant temperature medium is filled in the tank, the constant temperature medium comprises but is not limited to ultrapure water, an oxygen bomb heat pool and a reference heat pool are arranged in a constant temperature medium environment, thermopiles with completely identical structures and performances are respectively sleeved on the peripheries of the oxygen bomb heat pool and the reference heat pool, and the two thermopiles are reversely connected to form a differential heat measuring mode so as to offset the influence of parasitic heat flow; the water tank comprises an outer tank and an inner tank, the inner tank is located in the outer tank, the calorimetric cell and the thermopile are both arranged in the inner tank, the tank wall of the inner tank is of an interlayer structure, and air is filled in the interlayer; the inner cabinet is provided with a movable connecting cover, and when the movable connecting cover is opened, the constant temperature media in the inner cabinet and the outer cabinet exchange heat; when the movable connecting cover is closed, the inner cabinet and the outer cabinet exchange heat through an air layer.)

1. The calorimetric system of the combustion heat measuring instrument is characterized by comprising a water tank, wherein the water tank is filled with a constant temperature medium, and the constant temperature medium comprises but is not limited to ultrapure water; in a constant temperature medium environment, an oxygen elasticity heat measuring pool and a reference heat measuring pool are arranged, thermopiles with completely same structure and performance are respectively sleeved on the peripheries of the oxygen elasticity heat measuring pool and the reference heat measuring pool, and the two thermopiles are reversely connected to form a differential heat measuring mode so as to counteract the influence of parasitic heat flow.

2. The calorimetry system of the combustion heat tester of claim 1, wherein the water tank comprises an outer tank and an inner tank, the inner tank is located in the outer tank, the calorimetric cell and the thermopile are both arranged in the inner tank, the tank wall of the inner tank is of a sandwich structure, and air is filled in the sandwich structure; the inner cabinet is provided with a movable connecting cover, and when the movable connecting cover is opened, the constant temperature media in the inner cabinet and the outer cabinet exchange heat; when the movable connecting cover is closed, the inner cabinet and the outer cabinet exchange heat through an air layer.

3. The calorimeter system of claim 2, wherein the inner cabinet is provided with a stirrer to maintain the temperature of the isothermal medium in the inner cabinet at an equilibrium.

4. The calorimeter system of claim 2, wherein the outer cabinet is provided with a temperature control device to maintain the temperature of the thermostatic medium in the outer cabinet at a constant temperature of 20-70 ℃.

5. The calorimeter system of claim 1, wherein the thermopile comprises 20 to 2000 pairs of thermocouples connected in series.

Technical Field

The invention relates to the technical field of heat measurement equipment, in particular to a calorimetric system of a combustion heat determinator.

Background

The combustion heat is the heat generated when 1mol of combustible is sufficiently combusted in oxygen at 25 ℃ under 101kPa to produce a stable compound.

The traditional combustion heat measuring method is based on a water equivalent method, namely, an oxygen bomb is placed in a water bath with a known initial temperature, the water temperature is increased by heat generated by combustion, and the combustion heat is indirectly measured by measuring the increase value of the water temperature. The traditional oxygen bomb calorimeter of the water equivalent method has the defects of harsh environmental condition requirements, poorer test precision, large sample amount of samples and unsuitability for explosive samples and precious samples. And the water equivalent method only focuses on the initial value and the final temperature rise of the water temperature, can not effectively reflect the heat release process, and is difficult to meet the requirement of high-precision rapid characterization at present. The heat conductivity type calorimeter based on the Calvet calorimetric principle utilizes the thermopile to directly measure the heat in the calorimetric channel, and the heat flow detectors, namely thermocouples, are uniformly arranged around the calorimetric channel, so that the change of the heat at any point in the calorimetric channel can be captured, and the calorimeter has the advantages of high sensitivity (0.2 mu W), good stability (long-time baseline drift is not more than +/-0.2 mu W), small sample amount (2-30 mg), simple explosion-proof operation, wide application range, low environmental requirement, good repeatability, high accuracy and the like.

The heat conduction type micro calorimeter based on the Calvet calorimetric principle uses the thermopile to directly measure the heat change, and has the advantages of small required sample amount and capability of continuously and online recording a heat flow curve. According to the Tian equation, the thermoelectric potential generated by the thermopile is: e ═ epsilon_ABΔT＝ε_AB(T_i-T₀) In the formula of_ABThe thermoelectric power, T, is dependent on the thermocouple material and temperature_iIs the temperature of the interface in the thermopile, T₀Is the thermopile external interface temperature. The Tian equation can improve accuracy for slow exothermic reactions by peltier compensation of the measurement cell, with accuracies of more than 1%. The Tian equation is not applicable to reaction processes involving rapid heat exchange (e.g., heat of combustion). Since the time constant of this process is very small, this can only be achieved with a large thermal conductivity and a small effective heat capacity.

Moreover, since the thermal conductivity type calorimeter adopts the thermocouples to directly measure, when the number of the thermocouples is large and the hot junction is large enough, slight changes of the ambient temperature can be detected in the thermopile, so that parasitic current is generated, the fluctuation of a base line is increased, and the measurement error is increased.

Disclosure of Invention

In view of the above, the main objective of the present invention is to provide a differential calorimetry based calorimetric system, so as to solve the above mentioned technical problems.

In order to achieve the purpose, the invention provides the following technical scheme:

a calorimetric system of a combustion heat tester comprises a water tank, wherein the water tank is filled with a constant temperature medium, and the constant temperature medium comprises but is not limited to ultrapure water; in a constant temperature medium environment, an oxygen elasticity heat measuring pool and a reference heat measuring pool are arranged, thermopiles with completely same structure and performance are respectively sleeved on the peripheries of the oxygen elasticity heat measuring pool and the reference heat measuring pool, and the two thermopiles are reversely connected to form a differential heat measuring mode so as to counteract the influence of parasitic heat flow.

The water tank comprises an outer tank and an inner tank, the inner tank is located in the outer tank, the calorimetric cell and the thermopile are both arranged in the inner tank, the tank wall of the inner tank is of an interlayer structure, and air is filled in the interlayer; the inner cabinet is provided with a movable connecting cover, and when the movable connecting cover is opened, the constant temperature media in the inner cabinet and the outer cabinet exchange heat; when the movable connecting cover is closed, the inner cabinet and the outer cabinet exchange heat through an air layer.

The inner cabinet is provided with a stirrer, so that the temperature of the constant-temperature medium in the inner cabinet is kept balanced.

The outer cabinet is provided with a temperature adjusting device PID controller, so that the temperature of the constant-temperature medium in the outer cabinet is kept constant (the temperature of the constant-temperature medium in the outer cabinet is kept constant at any set temperature between 20 ℃ and 70 ℃).

The thermopile is formed by connecting 20-2000 pairs of thermocouples in series.

The invention has the following positive effects:

the thermopile is formed by connecting 200-2000 pairs of thermocouples in series, and can detect the change of heat at each position in a heat measuring channel; by means of measuring cells and ginsengCompared with a reverse connection mode of the cell, the influence of parasitic current caused by environmental fluctuation is greatly reduced, and the long-time baseline fluctuation is not more than +/-1 muV; water is used as a constant temperature medium, a water bath is used for replacing a traditional metal bath, and the specific heat capacity of the water is large, so that if the volume of a homothermal block is 10dm³Calculated, the heat generated by 10mg of the standard substance benzoic acid is about 265J, which can raise the temperature of the aluminum block by 0.083 ℃ and raise the temperature of the water by 0.0063 ℃, therefore, for the combustion reaction with rapid and large heat, the water bath selected by the constant temperature block is more suitable than the metal bath; the PID controller is used for controlling the water temperature of the outer cabinet, the inner cabinet and the outer cabinet are connected through a movable connecting cover, when the instrument is started, the movable connecting cover is opened, the inner cabinet and the outer cabinet are connected, the water temperature of the inner cabinet and the water temperature of the outer cabinet are quickly consistent through heat convection, and then the movable connecting cover is closed, so that the temperature of the inner cabinet tends to be stable; the influence of the environment on the thermopiles is reduced through the outer cabinet, the temperature of the outer interfaces of the two thermopiles is ensured to be consistent through the inner cabinet, and the base line fluctuation caused by the temperature fluctuation of the outer interfaces of the thermopiles is reduced through the reverse connection of the two thermopiles.

Drawings

FIG. 1 is a schematic view of a calorimeter system for measuring combustion heat.

Fig. 2 is a schematic diagram of a thermopile device structure.

Fig. 3 is a top view of fig. 2.

Reference numerals: 1-water bath external cabinet; 2-water bath inner cabinet; 3-inner cabinet cover plate (movable connection cover); 4-oxygen bomb thermal pool; 5-oxygen bomb battery thermopile; 6-inner cabinet stirrer; 7-reference calorimetric pool; 8-reference thermopiles; 9-constant temperature medium; 101-thermopile fixing framework; 102-a calorimetric channel; 103-inner insulating layer; 104-thermopile monolithic; 105-an outer insulating layer; 106-fastening screws.

Detailed Description

Referring to fig. 1, the calorimetric system of the combustion heat measuring instrument comprises a water bath device, a calorimetric cell and a thermopile, which are described in the following.

The water bath device comprises an outer cabinet 1 and an inner cabinet 2, wherein the inner cabinet 2 is located in the outer cabinet 1, and a constant temperature medium 9 is contained in the inner cabinet; the cabinet wall of the inner cabinet 2 is of an interlayer structure, and air is filled in the interlayer; the inner cabinet is provided with a movable connecting cover 3, and when the movable connecting cover 3 is opened, the constant temperature media in the inner cabinet 1 and the outer cabinet 2 exchange heat; when the movable connecting cover 3 is closed, the inner cabinet 2 and the outer cabinet 1 exchange heat through the air layer of the inner cabinet 2. The inner cabinet 2 is provided with a stirrer 6, so that the temperature of a constant temperature medium 9 in the inner cabinet is kept balanced. The outer cabinet 1 is provided with a temperature adjusting device PID controller, so that the temperature of the constant temperature medium in the outer cabinet is kept at a temperature set value.

The thermal battery and the thermopile are both arranged in the inner cabinet, an oxygen elasticity thermal battery 4 and a reference thermal battery 7 are arranged in a constant temperature medium environment, the thermopile 5 is sleeved on the periphery of the oxygen elasticity thermal battery 4, the thermopile 8 is sleeved on the periphery of the reference thermal battery 7, the thermopile 8 and the thermopile 5 have the same structure and consistent performance, but the two are reversely connected to form a differential thermal mode so as to offset the influence of parasitic heat flow.

See fig. 2, 3. The thermopile 5 or 8 is composed of a fixed framework 101, a heat measuring channel 102, an inner insulating layer 103, a thermopile single sheet 104, an outer insulating layer 105 and a fastening screw 106.

The manufacturing method of the thermopile comprises the following steps:

the method comprises the steps that 10-40 thermoelectric single chips are vertically and uniformly arranged around a heat measurement channel, a heat junction is tightly contacted with the heat measurement channel, a thin mica plate is adopted for insulation, and a fixing framework 101 and fastening screws 106 are used for forming a cylindrical whole.

The thermopile monolith 104 is composed of a mica sheet and a thermocouple. Each thermopile single chip 104 consists of 20-50 pairs of thermocouples, a mica sheet is used as a framework, the thermocouples are uniformly and tightly distributed on the mica frame, and in order to increase the contact area between the thermocouples and the wall of the heat measuring container, the hot junction of the thermocouples is designed to be large enough.

In order to prevent heat loss, insulation layers, i.e. an inner insulation layer 103 and an outer insulation layer 105, are provided at both the inner and outer interfaces of the thermopile.

All structural designs are obtained through rigorous calculation, the effective heat capacity of the thermopile is greatly increased through the design, and the sensitivity of the instrument is improved.

When the instrument works, an oxygen bomb is placed in the oxygen bomb heat pool 4, oxygen with certain pressure is filled in the oxygen bomb, and a sample to be tested, an ignition wire and other auxiliary combustion substances are placed in the oxygen bomb. The stirrer 6 and the movable connecting cover 3 are opened, the inner cabinet 2 and the outer cabinet 1 can exchange constant temperature media at the moment, the temperature is controlled at a temperature set value (the temperature is constant between 20 ℃ and 70 ℃) through the water cabinet PID temperature controller, the movable connecting cover 3 is closed when the temperature is constant, and the water temperature in the inner cabinet 2 is kept constant.

The influence of the environment on the water tank is absorbed by the outer tank, and the influence of the environment temperature fluctuation on the temperature of the inner tank is reduced and can be ignored due to the large thermal resistance of the air layer of the inner tank. Because the movable connecting cover 3 is closed, and under the action of the stirrer 6, the temperature of each part of the inner cabinet is kept consistent, because the two thermopiles are connected in series in an inverted way, the thermoelectrical potential fluctuation generated by the temperature fluctuation of the inner cabinet to the thermopiles is greatly reduced, and the long-time baseline fluctuation is not more than +/-1 muV.