A differential scanning calorimeter with high sensitivity

Abstract

The application discloses a differential scanning calorimeter with high sensitivity. The heat flow sensor in the application is provided with a sensor pressing block above and is fixedly connected through a screw; the heat flow sensor is mainly composed of a sample end and a reference end, three bare wire thermocouples are connected in series at the bottom of the sample end and the reference end respectively, and the multi-signal superposition significantly enhances the heat flow detection sensitivity of the instrument; the copper base structure is divided into a heat dissipation end base and a refrigeration end base, an armored heater is fixedly installed on the upper surface of the heat dissipation end base and is used for providing uniform and controllable heating power to the furnace body, and the refrigeration end base is integrated with a refrigeration head and a fin type radiator, and the high-efficiency refrigeration and heat dissipation of the instrument are realized in cooperation; the armored heater adopts a double helix coiled structure design. The application integrates the advantages of high sensitivity, heat dissipation and refrigeration integration and low cost, and effectively reduces the manufacturing difficulty and production cost of the equipment while improving the heat flow detection sensitivity of the differential scanning calorimeter.

Description

Technical Field

[0001] This invention relates to the field of analytical instrument technology, and in particular to a differential scanning calorimeter with high sensitivity. Background Technology

[0002] A differential scanning calorimeter (DSC) is a thermal analysis instrument that measures the difference in heat flow between a sample and a reference material as a function of temperature under programmed temperature control. DSCs can quickly and easily test thermodynamic data such as phase transition temperature, enthalpy, and entropy of samples, and are widely used in materials-related fields such as chemical engineering, minerals, petroleum, and product manufacturing.

[0003] Differential scanning calorimeters (DSCs) are mainly divided into two types: power-compensated and heat-flow-based. Compared to the power-compensated type, the heat-flow-based DSC has the advantage of a more stable baseline. It adopts a single furnace design, using a single heating wire to provide heating power to the entire furnace, thus ensuring that the sample end and the reference end are in the same thermal power environment. Independent thermocouple nodes are configured for the sample end and the reference end to detect and output the heat flow difference signal between them. Therefore, the heat-flow-based DSC measures the heat flow difference between the sample end and the reference end, and this heat flow difference is proportional to the temperature difference between the two ends.

[0004] Traditional heat flux differential scanning calorimeters often face high cost pressures during manufacturing. On one hand, their furnace bodies are often made of silver, a relatively expensive material, significantly increasing raw material costs. On the other hand, the complex design of the heat flux sensor places extremely high demands on machining accuracy and welding processes, further increasing manufacturing difficulty and production costs. Furthermore, in terms of instrument assembly and maintenance, parts replacement costs are high, and core components are difficult to disassemble and replace easily. Regarding temperature detection, traditional differential scanning calorimeters typically use a single thermocouple to measure the sample and reference temperatures separately. This method has limitations in thermal response speed and signal acquisition capabilities, resulting in relatively low sensitivity in heat flux detection, making it difficult to meet the requirements of high-precision thermal analysis. Summary of the Invention

[0005] In view of the above problems, the purpose of this invention is to provide a differential scanning calorimeter with high sensitivity, which aims to improve the heat flux detection sensitivity of the differential scanning calorimeter while reducing the manufacturing difficulty and production cost of the equipment.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention includes:

[0008] Furnace body;

[0009] A multi-point series heat flow sensor is installed inside the furnace body and has a sample end and a reference end. The sample end and the reference end are connected by a thermal resistance bridge. At least three bare wire thermocouples connected in series are respectively provided at the bottom of the sample end and the reference end for outputting the heat flow difference signal between the sample end and the reference end.

[0010] A sensor pressure block is disposed above the heat flow sensor to enable the detachable installation of the heat flow sensor;

[0011] An armored heater is located below the furnace body and is used to provide heating power to the furnace body;

[0012] An integrated heat dissipation and cooling copper base is located below the armored heater. It includes a heat dissipation end base and a cooling end base. The heat dissipation end base has a circular hole in the center for threading the sample end thermocouple lead and the reference end thermocouple lead. The cooling end base has a hollow cylindrical structure in the center for assembling and fixing the cooling head.

[0013] Compared with the prior art, the advantages and positive effects of the present invention are as follows: It innovatively designs a differential scanning calorimeter with a detachable structure and low cost. Its bottom adopts a multi-sensor series structure, which can directly measure the heat flow difference between the sample end and the reference end. Compared with the traditional single thermocouple temperature measurement method, this structure significantly improves the TAWN sensitivity from the conventional 3.0 to more than 8.0, while also effectively reducing the manufacturing difficulty of the heat flow sensor.

[0014] In addition, its unique fixed design facilitates the quick disassembly and replacement of the heat flow sensor; the designed integrated heat dissipation and cooling copper base is clearly divided into heat dissipation end and cooling end in structure, realizing the efficient integration of heat dissipation and cooling functions in the same device. While maintaining good heat conduction performance, it greatly reduces the structural complexity compared with traditional cooling structure, and has higher economic efficiency and practical value.

[0015] The double-helix coil armored heater provides uniform and controllable heating power to the furnace body. By optimizing the structural layout, the effective contact area between the heater and the furnace body is significantly increased in a limited space, which effectively improves the utilization efficiency of heating power and the thermal response speed of the instrument. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the differential scanning calorimeter according to an embodiment of the present invention.

[0017] Figure 2 for Figure 1 A schematic diagram of a multi-point series heat flux sensor.

[0018] Figure 3 for Figure 1A schematic diagram of the integrated heat dissipation and cooling copper base.

[0019] Figure 4 for Figure 1 A schematic diagram of a double-helix coil armored heater.

[0020] Figure 5 for Figure 1 A schematic diagram of the heat flow sensor pressure block.

[0021] Figure 6 This is a schematic diagram of a sensitivity test.

[0022] Figure 7 The graph shows the results of three sensitivity tests. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be noted that the specific embodiments are only a detailed description of the present invention and should not be regarded as a limitation of the present invention.

[0024] like Figure 1 As shown, the differential scanning calorimeter provided in this embodiment mainly includes a furnace body 3, a multi-point series heat flow sensor 4, a sensor pressure block 5, a heat dissipation and cooling integrated copper base 1, and an armored heater 2. The furnace body 3 is equipped with the multi-point series heat flow sensor 4. A sensor pressure block 5 is located above the heat flow sensor 4 and is fixedly connected by screws, thus enabling convenient disassembly and replacement of the heat flow sensor. A double-helix coil armored heater 2 is located below the furnace body 3, and the two are fixed together by screws to achieve close thermal contact, thereby maximizing heating efficiency. The armored heater 2 is located below the heat dissipation and cooling integrated copper base 1.

[0025] like Figure 2 As shown, the multi-point series heat flow sensor 4 in this embodiment mainly consists of a sample end 7 and a reference end 6, which are connected by a thermal resistance bridge 13. The thermal resistance bridge provides good thermal resistance for both ends, which helps to form a stable thermal gradient during heat flow measurement, thereby effectively improving the resolution of the instrument's heat flow detection. Four cuboid thin-plate structures 14 are provided on the upper surfaces of both the sample end and the reference end to fully fix the sample crucible 15 and the reference crucible 16, achieving positioning. To ensure extremely high sensitivity in heat flow detection, three identical bare-wire thermocouples are laser-welded at 1 mm to the left, 1 mm to the center, and 1 mm to the right of the bottom center 17 of the sample end. (The positive electrode material of each bare-wire thermocouple is a nickel-chromium alloy consistent with the main body of the heat flow sensor, and the negative electrode is constantan alloy; the three identical bare-wire thermocouples form an E-type thermocouple.) Figure 2The thermocouple leads 8 at the sample end are obtained by connecting them in series as shown, so that the total output thermoelectric potential is the sum of the potentials of the three bare wire thermocouples. The reference end adopts a highly symmetrical structure design with the sample end. The three bare wire thermocouples at the bottom of the reference end are also laser-welded to the left, center and right of the bottom center 18 of the reference end 1 mm away. The thermocouple leads at the sample end and the thermocouple leads at the reference end are connected to the differential operational amplifier circuit 10 to directly measure the heat flow difference between the sample end and the reference end, so as to improve the instrument's heat flow detection sensitivity and reduce the influence of common mode noise.

[0026] Preferably, the main body material of the heat flow sensor is a nickel-chromium alloy, which has the characteristics of high temperature resistance and low coefficient of thermal expansion. This material is the same as the positive electrode material of the E-type thermocouple, so it will not cause contamination to the thermocouple during welding. The high temperature resistance and low coefficient of thermal expansion can effectively suppress the deformation of the sensor itself caused by temperature rise. The bottom circle diameter of the heat flow sensor is 17.5 mm and the thickness is 0.2 mm, while the bottom circle diameter of the sample end is 6 mm. The thermal resistance connecting bridge is only 0.1 mm thick, which helps to form a stable thermal gradient during the measurement process, thereby effectively improving the resolution of heat flow detection. The diameter of the bare wire thermocouple used is 0.3 mm, which ensures a fast thermal response speed during heat flow measurement.

[0027] Preferably, the differential operational amplifier circuit directly measures the temperature difference between the sample end and the reference end through the thermocouple leads at the sample end and the thermocouple leads at the reference end, and converts it into a heat flow signal; at the same time, the temperature at the bottom of the finned heat sink is collected in real time by a high-precision thermistor to monitor the temperature change at the heat sink in real time.

[0028] like Figure 3 As shown, the integrated heat dissipation and cooling copper base 1 in this embodiment includes a heat dissipation end base 19 on the right and a cooling end base 22 on the left. The heat dissipation end base has two circular holes 20 at its center, used for threading the sample end thermocouple lead 8 and the reference end thermocouple lead 9, respectively. The cooling end base is connected to the heat dissipation end base via a copper thermal bridge 21, thus achieving structural connection and limited heat conduction. A hollow cylindrical structure 23 is provided on the cooling end base for assembling and fixing the cooling head. A finned heat sink 11 is installed at the center of the hollow cylindrical structure 23, significantly increasing the effective heat dissipation area of ​​the heat dissipation end and greatly improving the instrument's heat exchange capacity under heat dissipation and cooling conditions. A high-precision thermistor 12 can collect the temperature at the bottom of the heat sink 11 in real time. The copper thermal bridge can effectively control the axial heat flow from the heat dissipation end base to the cooling end base, avoiding excessive heat transfer to the cooling end during heat dissipation, thereby ensuring heat dissipation efficiency and reducing the power consumption required for system cooling.

[0029] Preferably, the base body is made of copper and silver-plated, which has both excellent thermal conductivity and temperature uniformity; the width of the copper thermal bridge is limited to 16 mm and the thickness is 6 mm, which can effectively reduce power consumption under cooling conditions while ensuring heat dissipation efficiency; the diameter of the circular hole in the center of the heat dissipation end base is 2 mm, and the diameter of the hollow cylinder in the middle of the cooling end base is 86 mm.

[0030] like Figure 4 As shown, the fine-diameter armored heater 2 in this embodiment adopts a double-helix winding structure design, which significantly increases the effective contact area between the heater 2 and the furnace body 3, achieving higher power density within a limited space, thereby significantly improving the utilization efficiency of heating power and the thermal response speed of the instrument; at the same time, the armored structure has excellent insulation performance, which can effectively prevent short circuit risks. Preferably, the diameter of the armored heater is 1.0 mm.

[0031] like Figure 5 As shown, in this embodiment, the sensor pressure block 5 is positioned above the heat flow sensor and is fixedly connected by screws, thereby enabling quick disassembly and replacement of the heat flow sensor. Preferably, the bottom diameter of the sensor pressure block is 17 mm.

[0032] Sensitivity tests were conducted on the differential scanning calorimeter designed in this application:

[0033] The sensitivity performance of the differential scanning calorimeter in this embodiment was analyzed using a comparative testing method proposed by the Thermische Analyse Werkgroep Nederland (TAWN). TAWN defines sensitivity as the instrument's ability to measure weak thermal effects (such as glass transition or melting), and considers the ratio of the signal generated by the weak thermal effect to the baseline noise as the determining factor for sensitivity.

[0034] The test used 4,4'-azoxyanisole with a purity higher than 98% as the sample, which was obtained from Shanghai Aladdin Biochemical Technology Co., Ltd. This sample exhibited two endothermic transition characteristic peaks, spaced approximately 17 °C apart. The first peak was a solid-liquid transition at approximately 117 °C, characterized by a relatively large peak; the second peak was a liquid-isotropic liquid transition at around 134 °C, characterized by a relatively small peak.

[0035] like Figure 6The diagram illustrates the sensitivity test. On the low-temperature side of the characteristic peak, data points within a 2°C range are selected to draw a straight line representing the average baseline. This line is then extrapolated to the characteristic peak region. Within the same temperature range (2°C), two additional lines are drawn parallel to the average baseline to encompass all recorded data points. The vertical distance d (peak-to-peak noise level) between these two lines and the peak height c are measured. Sensitivity S = c / d; the larger the value, the higher the instrument's sensitivity.

[0036] Using a Mettler-Toledo analytical balance with an accuracy of 0.1 mg, 0.2–0.3 mg of 4,4'-azoanisole sample was weighed. The sample was then placed in a solid aluminum crucible and transferred to the sample end of a differential scanning calorimeter, while an empty crucible was placed at the reference end as a control.

[0037] The temperature program consisted of two steps: first, it was set to isothermal mode for 10 minutes, then switched to scanning mode with a heating rate of 1 °C / min and a temperature range of 130 °C–140 °C. This test was repeated three times. The results of the three tests are as follows: Figure 7 And as shown in the table below.

[0038]

[0039] Depend on Figure 7 As can be seen from the data in the table, the TAWN sensitivity of the differential scanning calorimeter prototype was greater than 8.0 in all three tests, and the data consistency was good, which met the design requirements.

[0040] In summary, this application proposes a high-sensitivity differential scanning calorimeter. Its core innovations include: designing a differential scanning calorimeter with detachable key components; employing multiple E-type thermocouples connected in series for the heat flow sensor, resulting in a simple and low-cost main structure and high heat flow detection sensitivity; designing an integrated heat dissipation and cooling copper base, solving the problem of precisely designing the geometric parameters and material heat transfer characteristics of the copper thermal bridge to match the opposite heating process between the heat dissipation and cooling ends, thus optimizing the heat flow path. Compared to traditional single heat dissipation or cooling bases, this design not only achieves efficient integration of heat dissipation and cooling within the same device but also significantly reduces manufacturing costs while ensuring excellent thermal conductivity; and employing a double-helix coil sheathed heater to provide uniform and controllable heating power to the furnace body, significantly increasing the effective contact area between the heater and the furnace body within a limited space, thereby effectively improving the utilization efficiency of heating power and the instrument's thermal response speed. This application improves the heat flow detection sensitivity of the differential scanning calorimeter while effectively reducing the manufacturing difficulty and production cost, providing a practical technical path and important reference for developing high-sensitivity, low-cost differential scanning calorimeters.

[0041] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-sensitivity differential scanning calorimeter, characterized in that, include: Furnace body (3); A multi-point series heat flow sensor (4) is installed inside the furnace body (3) and has a sample end (7) and a reference end (6). The sample end (7) and the reference end (6) are connected by a thermal resistance bridge (13). Three bare wire thermocouples connected in series are respectively provided at the bottom of the sample end (7) and the reference end (6) for outputting the heat flow difference signal between the sample end and the reference end. A sensor pressure block (5) is disposed above the heat flow sensor (4) to enable the heat flow sensor (4) to be detachably installed; An armored heater (2) is disposed below the furnace body (3) and is used to provide heating power to the furnace body (3); A heat dissipation and cooling integrated copper base (1) is set below the armored heater (2), including a heat dissipation end base (19) and a cooling end base (22). The heat dissipation end base (19) has a circular hole (20) in the center for threading the sample end thermocouple lead (8) and the reference end thermocouple lead (9). The cooling end base (22) has a hollow cylindrical structure (23) in the center for assembling and fixing the cooling head. The bottom of the sample end (7) and the reference end (6) are each connected in series with three bare wire thermocouples laser-welded at three equidistant points. These three points are the center point and the points 1 mm apart on both sides of the center point, in order to improve the sensitivity of the instrument's heat flow detection. The main body material of the multi-point series heat flow sensor (4) is the same nickel-chromium alloy as the positive electrode material of the thermocouple, so that the laser welding will not cause contamination to the thermocouple and effectively suppress sensor deformation caused by temperature rise. The bottom circle diameter of the heat flow sensor is 17.5 mm and the thickness is 0.2 mm; the bottom circle diameter of the sample end is 6 mm; the thickness of the thermal resistance connecting bridge is 0.1 mm, which helps to form a stable thermal gradient during the measurement process, thereby effectively improving the resolution of heat flow detection. The bare wire thermocouples used have a diameter of 0.3 mm, which ensures a fast thermal response.

2. The differential scanning calorimeter according to claim 1, characterized in that: It also includes a differential operational amplifier circuit (10), which is connected to the sample end thermocouple lead (8) and the reference end thermocouple lead (9) respectively to reduce the influence of common-mode noise.

3. The differential scanning calorimeter according to claim 1, characterized in that: The heat flow sensor (4) and the sensor block (5) are fastened together by only four M2 screws, thereby enabling convenient disassembly and replacement of the heat flow sensor.

4. The differential scanning calorimeter according to claim 3, characterized in that: The sample end (7) and the reference end (6) each have four cuboid thin sheet structures (14) on their upper surfaces, which are used to perform planar positioning of the sample crucible (15) and the reference crucible (16).

5. The differential scanning calorimeter according to claim 3, characterized in that: The armored heater (2) adopts a double spiral winding structure design to increase the effective contact area between the armored heater (2) and the furnace body (3) and achieve higher power density in a limited space.

6. The differential scanning calorimeter according to claim 1, characterized in that: The hollow cylindrical structure (23) has a finned heat sink (11) at its center to enhance heat dissipation.

7. The differential scanning calorimeter according to claim 6, characterized in that: It also includes a high-precision thermistor (12), which is disposed at the bottom of the finned heat sink (11) for real-time monitoring of the heat dissipation end temperature.

8. The differential scanning calorimeter according to claim 1, characterized in that: The heat dissipation end base (19) and the cooling end base (22) are connected by a copper thermal bridge (21).

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