A teaching aid and measurement method for measuring combustion heat based on pressure

Abstract

The present invention discloses a teaching aid and a measuring method for measuring combustion heat based on pressure. It comprises a circular fixing plate, the upper end surface of the circular fixing plate is provided with a circular fixing groove, a cylindrical sealing cavity is movably provided in the circular fixing groove, the lower end surface of the cylindrical sealing cavity is an open structure, the upper end surface of the cylindrical sealing cavity is a closed structure, a rubber sealing ring is provided on the lower end of the cylindrical sealing cavity, and the rubber sealing ring is located in the circular fixing groove, and a group of fixing blocks are evenly distributed on the outer surface of the cylindrical sealing cavity. The present invention has the advantages of simple teaching aid structure, easy production and simple operation; the heat-conducting medium does not require water, which is water-saving and environmentally friendly, does not require complicated Reynolds temperature correction, and has high measurement accuracy; the amount of medicine used is small, which saves costs and reduces pollution; it is closely linked to the teaching materials, allowing students to creatively apply the knowledge they have learned, which helps to deepen the understanding and consolidation of physical and chemical knowledge and experimental methods, and is convenient for cultivating students' scientific thinking ability and practical ability.

Description

Technical Field

[0001] The invention relates to a teaching aid and a measuring method for measuring combustion heat, in particular to a teaching aid and a measuring method for measuring combustion heat based on pressure. Background Art

[0002] Heat of combustion refers to the heat released when a substance and oxygen undergo a complete combustion reaction. It is generally measured by the amount of unit substance, unit mass or unit volume of fuel released when it is burned. At present, the oxygen bomb method is used both at home and abroad to determine the calorific value of solid and liquid fuels. The principle is to place a certain amount of analytical sample in an oxygen bomb, fill the oxygen bomb with oxygen, and then make the sample completely burn in the oxygen bomb. The oxygen bomb is placed in a container full of water in advance. According to the increase in water temperature after the sample is burned, the calorific value of the sample is calculated. Since the actual situation is not so simple, it is necessary to consider various factors that affect the measurement and make various corrections before obtaining the correct results. Therefore, in order to solve the above technical problems and combine many years of teaching practice, a teaching aid and measurement method based on pressure measurement of combustion heat was invented. Summary of the invention

[0003] The purpose of the present invention is to provide a teaching aid and a measuring method for measuring combustion heat based on pressure. The teaching aid has a simple structure, is easy to make, and is easy to operate; the heat transfer medium does not require water, which is water-saving and environmentally friendly, does not require complicated Reynolds temperature correction, and has high measurement accuracy; the amount of medicine used is small, which saves costs and reduces pollution; it is closely linked to the teaching materials, allowing students to creatively apply the knowledge they have learned, which helps to deepen the understanding and consolidation of physical and chemical knowledge and experimental methods, and is convenient for cultivating students' scientific thinking ability and practical ability.

[0004] The technical solution of the present invention is a teaching aid and a measuring method for measuring combustion heat based on pressure, comprising a circular fixing plate, an upper end surface of the circular fixing plate is provided with an annular fixing groove, a cylindrical sealing cavity is movably provided in the annular fixing groove, the lower end surface of the cylindrical sealing cavity is an open structure, the upper end surface of the cylindrical sealing cavity is a closed structure, a rubber sealing ring is provided on the lower end of the cylindrical sealing cavity, and the rubber sealing ring is located in the annular fixing groove, a group of fixing blocks are evenly distributed on the outer surface of the cylindrical sealing cavity, a group of fixing blocks are respectively vertically provided with fixing bolts, the lower ends of the fixing bolts are respectively connected with fixing nuts, and the fixing nuts are respectively fixed on the circular fixing plate; an oxygen bomb is movably placed on the circular fixing plate in the cylindrical sealing cavity, the oxygen bomb is connected to an ignition wire, the ignition wire is connected to the upper end surface of the cylindrical sealing cavity, and the ignition wire outside the cylindrical sealing cavity is connected to an ignition device; a differential pressure gauge is connected to one side of the cylindrical sealing cavity through a catheter.

[0005] In the aforementioned teaching aid for measuring combustion heat based on pressure, three fixing blocks are evenly distributed on the outer surface of the cylindrical sealing cavity.

[0006] In the aforementioned teaching aid for measuring combustion heat based on pressure, the outer surface of the cylindrical sealed cavity is provided with a heat-insulating layer; the circular fixing plate is made of heat-insulating material, and the teaching aid has good heat-insulating performance.

[0007] The measurement method of the combustion heat teaching aid based on pressure measurement includes the following steps:

[0008] A. Accurately weigh the mass of the ignition wire as m1, take the sample to be tested, press it into a tablet, and then accurately weigh the total mass of the pressed ignition wire and the sample to be tested as m2. The mass of the sample to be tested is m 样 =m2-m1, put the pressed ignition wire and the sample to be tested into the oxygen bomb, and then fill the oxygen bomb with oxygen at 0.5-1MPa for 30 seconds;

[0009] B. Place the oxygen bomb on the circular fixing plate, connect the oxygen bomb to the ignition wire, and then put the lower end of the cylindrical sealing cavity into the annular fixing groove. Then connect the fixing bolts on the fixing block with the fixing nuts on the circular fixing plate, and press the rubber sealing ring at the lower end of the cylindrical sealing cavity tightly into the annular fixing groove to ensure good air tightness.

[0010] C. After recording the initial pressure as P1 through the differential pressure gauge connected to one side of the cylindrical sealed cavity through the conduit, the ignition device is controlled to control the ignition of the oxygen bomb through the ignition wire. When the pressure of the differential pressure gauge rises to the maximum, the pressure is recorded as P2 through the differential pressure gauge, and the change value of the air pressure in the cavity before and after the combustion reaction is obtained, △P=P2-P1;

[0011] D. By rotating the fixing bolt, cancel the connection between the fixing bolt and the fixing nut, open the cylindrical sealed cavity, take out the oxygen bomb and open it, and accurately weigh the mass of the unburned ignition wire as m3, that is, the mass of the ignition alloy wire m 丝 =m1-m3.

[0012] In the aforementioned measurement method based on the pressure measurement combustion heat teaching aid, 0.2-0.3g of the sample to be tested is taken.

[0013] In the aforementioned measurement method based on the pressure measurement combustion heat teaching aid, the m 丝 ×Q 丝 +m 样 ×Q 样 =K×(P2-P1)=K×△P;

[0014] Where: m 丝 : Ignition alloy wire mass, unit: g; Q 丝 : Combustion heat of ignition alloy wire, unit: kJ / g; m sample: mass of the sample to be tested, unit: g; Q 样: Sample combustion heat, unit: kJ / g; K: Instrument heat capacity constant of the teaching aid, unit: kJ / Pa; △P: Change in air pressure in the cavity before and after the combustion reaction, unit: Pa.

[0015] In the aforementioned measurement method of the teaching aid for measuring combustion heat based on pressure, the K: the instrument heat capacity constant of the teaching aid, unit: kJ / Pa; the constant K is calibrated using a sample with known combustion heat.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention calculates the combustion heat of the sample by measuring the micro-pressure difference. Figure 1-3 ) The structure is simple, the production is easy, and the operation is simple; the heat transfer medium does not require water, which is water-saving and environmentally friendly, does not require complicated Reynolds temperature correction, and has high measurement accuracy; the amount of drugs used is small, and the amount of drugs used in the experiment is between 0.2-0.3g, which saves costs and reduces pollution; the measurement is fast and takes less time, the entire measurement process takes an average of 30 minutes, and the longest does not exceed 1 hour; in the processing of experimental data, it closely follows the textbooks, allowing students to creatively apply the knowledge they have learned, which helps to deepen the understanding and consolidation of physical and chemical knowledge and experimental methods, and is conducive to cultivating students' scientific thinking ability and practical ability.

[0018] Experimental proof:

[0019] 1. Basic Idea

[0020] When a substance burns, it releases heat. After a certain amount of gas absorbs the heat, its volume expands, causing the pressure to rise. The heat of combustion of the substance is calculated by measuring the gas pressure.

[0021] 2. Determination Principle

[0022] The heat generated by the combustion reaction in the oxygen bomb is transferred to the air and measuring device in the heat-insulated and sealed cylindrical cavity, causing the temperature in the cylindrical sealed cavity to rise from T1 to T2, as shown in the figure below, with the following formula:

[0023] m 丝 ×Q 丝 +m 样 ×Q 样 =(C 空 +C 计 )×(T2-T1) (1)

[0024] (1) Where:

[0025] m 丝 : Ignition alloy wire mass, unit: g;

[0026] Q 丝 : Combustion heat of ignition alloy wire, unit: kJ / g;

[0027] m 样 : Mass of the sample to be tested, unit: g;

[0028] Q 样 : Sample combustion heat, unit: kJ / g

[0029] C 空 : Heat capacity of air in the cylindrical sealing cavity, unit: kJ / K;

[0030] C 计 : Total heat capacity of the cylinder seal cavity and oxygen bomb and other components, unit: kJ / K;

[0031] For the same measuring device, (C 空 +C 计 ) remains unchanged, and is represented by K1, and equation (1) becomes:

[0032] m 丝 ×Q 丝 +m 样 ×Q 样 =(C 空 +C 计 )×(T2-T1)

[0033] m 丝 ×Q 丝 +m 样 ×Q 样 =K1×(T2-T1)

[0034] Under low pressure, the air in the closed cavity is regarded as an ideal gas, and P1 and P2 are the pressures corresponding to temperatures T1 and T2 respectively:

[0035] From: P2V=nRT2, P1V=nRT1, we get

[0036] T2-T1=V / nR×(P2-P1)

[0037] Under the same teaching aids and conditions, the volume V of the air in the cavity and the amount n of the substance are constant, R is the molar gas constant, V / nR is a constant, expressed by K2, and the following formula is obtained:

[0038] T2-T1=K2×(P2-P1)

[0039] Substitute T2-T1=K2×(P2-P1) into m 丝 ×Q 丝 +m 样 ×Q 样 =K1×(T2-T1), combining the constants K1×K2=K, we get:

[0040] m 丝 ×Q 丝 +m样 ×Q 样 =K1×K2×(P2-P1)=K×(P2-P1)

[0041] And △P=P2-P1;

[0042] That is: m 丝 ×Q 丝 +m 样 ×Q 样 =K×(P2-P1)=K×△P

[0043] As long as the air pressure change △P and K value in the cavity before and after the combustion reaction are measured, the combustion heat of the sample can be calculated. For the same measuring teaching aid and measuring conditions, the instrument heat capacity constant K value of the teaching aid remains unchanged. When measuring, the constant K is first calibrated with a sample with a known combustion heat, and then the sample combustion heat is measured according to the same steps.

[0044] In summary, the teaching aids of the present invention have a simple structure, are easy to make, and are easy to operate; the heat-conducting medium does not require water, which is water-saving and environmentally friendly, does not require complicated Reynolds temperature correction, and has high measurement accuracy; the amount of medicine used is small, which saves costs and reduces pollution; it closely follows the teaching materials, allowing students to creatively apply the knowledge they have learned, which helps to deepen the understanding and consolidation of physical and chemical knowledge and experimental methods, and is conducive to cultivating students' scientific thinking ability and practical ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram of the structure of the present invention;

[0046] Figure 2 is a top view of the present invention;

[0047] Figure 3 It is a structural schematic diagram of the cylindrical sealing cavity and the circular fixing plate of the present invention.

[0048] The markings in the attached drawings are: 1-circular fixing plate, 2-fixing nut, 3-fixing block, 4-fixing bolt, 5-cylindrical sealing cavity, 6-ignition wire, 7-conduit, 8-differential pressure gauge, 9-ignition device, 10-circular fixing groove, 11-rubber sealing ring, 12-oxygen bomb, 13-insulation layer. DETAILED DESCRIPTION

[0049] The following is combined with Figure 1-3 The present invention is further described with reference to the accompanying drawings and embodiments, but they are not intended to limit the present invention.

[0050] Example 1. A teaching aid for measuring combustion heat based on pressure (the instrument heat capacity constant K value of the teaching aid calibrated with benzoic acid), for measuring the combustion heat of naphthalene, comprises the following steps:

[0051] A. Accurately weigh the mass of the ignition wire as m1, take 0.2-0.3g of the sample to be tested, press it into a tablet, and then accurately weigh the total mass of the pressed ignition wire and the sample to be tested as m2. The mass of the sample to be tested is m 样 =m2-m1, put the pressed ignition wire and the sample to be tested into the oxygen bomb 12, and then fill the oxygen bomb 12 with oxygen at 0.5-1MPa for 30 seconds. The specification of the oxygen bomb 12 is 300mL;

[0052] B. Place the oxygen bomb 12 on the circular fixing plate 1, connect the oxygen bomb 12 to the ignition wire 6, then put the lower end of the cylindrical sealing cavity 5 into the annular fixing groove 10, then respectively connect the fixing bolts 4 on the fixing block 3 with the fixing nuts 2 on the circular fixing plate 1, and press the rubber sealing ring 11 at the lower end of the cylindrical sealing cavity 5 tightly into the annular fixing groove 10, so that the airtightness is good, and the outer surface of the cylindrical sealing cavity 5 is provided with a heat-insulating layer 13, and the circular fixing plate 1 is made of heat-insulating material, so the teaching aid has good heat-insulating performance;

[0053] C. After the initial pressure is recorded as P1 by the differential pressure gauge 8 connected to one side of the cylindrical sealed cavity 5 through the conduit 7, the model of the differential pressure gauge 8 is DMP-2P, and then the ignition device 9 is controlled to control the ignition of the oxygen bomb 12 through the ignition wire 6. When the pressure of the differential pressure gauge 8 rises to the maximum, the pressure recorded by the differential pressure gauge is P2, and the change value of the air pressure in the cavity before and after the combustion reaction is obtained, △P=P2-P1;

[0054] D. By rotating the fixing bolt 4, the connection between the fixing bolt 4 and the fixing nut 2 is canceled, the cylindrical sealing cavity 5 is opened, the oxygen bomb 12 is taken out and opened, and the mass of the unburned ignition wire is accurately weighed as m3, that is, the mass of the ignition alloy wire m 丝 =m1-m3.

[0055] Technical data:

[0056] The literature value of the constant volume combustion heat of the known ignition wire is: Q 丝 =6.694 kJ / g

[0057] Literature value of constant volume combustion heat of benzoic acid: Q 苯甲酸 =26.460kJ / g

[0058] Indoor temperature: 19℃

[0059] According to: 丝 ×Q 丝 +m 样 ×Q 样 =K×(P2-P1)=K×△P;

[0060] Where: m 丝 : Ignition alloy wire mass, unit: g; Q 丝 : Ignition alloy wire combustion heat, unit: kJ / g; m样 : Mass of the sample to be tested, unit: g; Q 样 : Sample combustion heat, unit: kJ / g; K: Instrument heat capacity constant of the teaching aid, unit: kJ / Pa; △P: Change in air pressure in the cavity before and after the combustion reaction, unit: Pa.

[0061] The measurement and calculation results are detailed in Table 1:

[0062] Table 1 Measurement and calculation results of Example 1

[0063]

[0064]

[0065] Note: The calculated Q sample is the constant volume combustion heat (Q v,m ), according to Q p,m -Q v,m =[∑V B(g) ]RT calculates the constant pressure heat of combustion (Q p,m ):where ∑V B(g) is the algebraic sum of the stoichiometric quantities of the gaseous substances participating in the reaction; R is the gas constant; T is the absolute temperature of the reaction; Q p,m , Q v,m The dimension is J / mol.

[0066] Example 2. A teaching aid for measuring combustion heat based on pressure (the instrument heat capacity constant K value of the teaching aid calibrated with benzoic acid), for measuring the combustion heat of naphthalene, comprises the following steps:

[0067] A. Accurately weigh the mass of the ignition wire as m1, take 0.2-0.3g of the sample to be tested, press it into a tablet, and then accurately weigh the total mass of the pressed ignition wire and the sample to be tested as m2. The mass of the sample to be tested is m 样 =m2-m1, put the pressed ignition wire and the sample to be tested into the oxygen bomb 12, and then fill the oxygen bomb 12 with oxygen at 0.5-1MPa for 30 seconds. The specification of the oxygen bomb 12 is 300mL;

[0068] B. Place the oxygen bomb 12 on the circular fixing plate 1, connect the oxygen bomb 12 to the ignition wire 6, then put the lower end of the cylindrical sealing cavity 5 into the annular fixing groove 10, then respectively connect the fixing bolts 4 on the fixing block 3 with the fixing nuts 2 on the circular fixing plate 1, and press the rubber sealing ring 11 at the lower end of the cylindrical sealing cavity 5 tightly into the annular fixing groove 10, so that the airtightness is good, and the outer surface of the cylindrical sealing cavity 5 is provided with a heat-insulating layer 13, and the circular fixing plate 1 is made of heat-insulating material, so the teaching aid has good heat-insulating performance;

[0069] C. After the initial pressure is recorded as P1 by the differential pressure gauge 8 connected to one side of the cylindrical sealed cavity 5 through the conduit 7, the model of the differential pressure gauge 8 is DMP-2P, and then the ignition device 9 is controlled to control the ignition of the oxygen bomb 12 through the ignition wire 6. When the pressure of the differential pressure gauge 8 rises to the maximum, the pressure recorded by the differential pressure gauge is P2, and the change value of the air pressure in the cavity before and after the combustion reaction is obtained, △P=P2-P1;

[0070] D. By rotating the fixing bolt 4, the connection between the fixing bolt 4 and the fixing nut 2 is canceled, the cylindrical sealing cavity 5 is opened, the oxygen bomb 12 is taken out and opened, and the mass of the unburned ignition wire is accurately weighed as m3, that is, the mass of the ignition alloy wire m 丝 =m1-m3.

[0071] Technical data:

[0072] The literature value of the constant volume combustion heat of the known ignition wire is: Q 丝 =6.694 kJ / g

[0073] Literature value of constant volume combustion heat of benzoic acid: Q 苯甲酸 =26.460kJ / g

[0074] Indoor temperature: 20℃

[0075] According to: 丝 ×Q 丝 +m 样 ×Q 样 =K×(P2-P1)=K×△P;

[0076] Where: m 丝 : Ignition alloy wire mass, unit: g; Q 丝 : Ignition alloy wire combustion heat, unit: kJ / g; m 样 : Mass of the sample to be tested, unit: g; Q 样 : Sample combustion heat, unit: kJ / g; K: Instrument heat capacity constant of the teaching aid, unit: kJ / Pa; △P: Change in air pressure in the cavity before and after the combustion reaction, unit: Pa.

[0077] The measurement and calculation results are detailed in Table 2:

[0078] Table 2 Measurement and calculation results of Example 2

[0079]

[0080] Note: The calculated Q sample is the constant volume combustion heat (Q v,m ), according to Q p,m -Q v,m =[∑V B(g) ]RT calculates the constant pressure heat of combustion (Q p,m ):where ∑VB(g) is the algebraic sum of the stoichiometric quantities of the gaseous substances participating in the reaction; R is the gas constant; T is the absolute temperature of the reaction; Q p,m , Q v,m The dimension is J / mol.

[0081] Example 3. A teaching aid for measuring combustion heat based on pressure (the instrument heat capacity constant K value of the teaching aid calibrated with benzoic acid) for measuring the combustion heat of sucrose comprises the following steps:

[0082] A. Accurately weigh the mass of the ignition wire as m1, take 0.2-0.3g of the sample to be tested, press it into a tablet, and then accurately weigh the total mass of the pressed ignition wire and the sample to be tested as m2. The mass of the sample to be tested is m 样 =m2-m1, put the pressed ignition wire and the sample to be tested into the oxygen bomb 12, and then fill the oxygen bomb 12 with oxygen at 0.5-1MPa for 30 seconds. The specification of the oxygen bomb 12 is 300mL;

[0083] B. Place the oxygen bomb 12 on the circular fixing plate 1, connect the oxygen bomb 12 to the ignition wire 6, then put the lower end of the cylindrical sealing cavity 5 into the annular fixing groove 10, then respectively connect the fixing bolts 4 on the fixing block 3 with the fixing nuts 2 on the circular fixing plate 1, and press the rubber sealing ring 11 at the lower end of the cylindrical sealing cavity 5 tightly into the annular fixing groove 10, so that the airtightness is good, and the outer surface of the cylindrical sealing cavity 5 is provided with a heat-insulating layer 13, and the circular fixing plate 1 is made of heat-insulating material, so the teaching aid has good heat-insulating performance;

[0084] C. After the initial pressure is recorded as P1 by the differential pressure gauge 8 connected to one side of the cylindrical sealed cavity 5 through the conduit 7, the model of the differential pressure gauge 8 is DMP-2P, and then the ignition device 9 is controlled to control the ignition of the oxygen bomb 12 through the ignition wire 6. When the pressure of the differential pressure gauge 8 rises to the maximum, the pressure recorded by the differential pressure gauge is P2, and the change value of the air pressure in the cavity before and after the combustion reaction is obtained, △P=P2-P1;

[0085] D. By rotating the fixing bolt 4, the connection between the fixing bolt 4 and the fixing nut 2 is canceled, the cylindrical sealing cavity 5 is opened, the oxygen bomb 12 is taken out and opened, and the mass of the unburned ignition wire is accurately weighed as m3, that is, the mass of the ignition alloy wire m 丝 =m1-m3.

[0086] Technical data:

[0087] The literature value of the constant volume combustion heat of the known ignition wire is: Q 丝 =6.694 kJ / g

[0088] Literature value of constant volume combustion heat of benzoic acid: Q 苯甲酸 =26.460kJ / g

[0089] Indoor temperature: 20℃

[0090] According to: 丝 ×Q 丝 +m 样 ×Q 样 =K×(P2-P1)=K×△P;

[0091] Where: m 丝 : Ignition alloy wire mass, unit: g; Q 丝 : Ignition alloy wire combustion heat, unit: kJ / g; m 样 : Mass of the sample to be tested, unit: g; Q 样 : Sample combustion heat, unit: kJ / g; K: Instrument heat capacity constant of the teaching aid, unit: kJ / Pa; △P: Change in air pressure in the cavity before and after the combustion reaction, unit: Pa.

[0092] The measurement and calculation results are detailed in Table 3:

[0093] Table 3 Measurement and calculation results of Example 3

[0094]

[0095] Note: The calculated Q sample is the constant volume combustion heat (Q v,m ), according to Q p,m -Q v,m =[∑V B(g) ]RT calculates the constant pressure heat of combustion (Q p,m ):where ∑V B(g) is the algebraic sum of the stoichiometric quantities of the gaseous substances participating in the reaction; R is the gas constant; T is the absolute temperature of the reaction; Q p,m , Q v,m The dimension is J / mol.

Claims

1. A teaching aid for measuring combustion heat based on pressure, characterized in that: The invention comprises a circular fixing plate (1), the upper end surface of the circular fixing plate (1) is provided with a circular fixing groove (10), a cylindrical sealing cavity (5) is movably provided in the circular fixing groove (10), the lower end surface of the cylindrical sealing cavity (5) is an open structure, the upper end surface of the cylindrical sealing cavity (5) is a closed structure, a rubber sealing ring (11) is provided on the lower end of the cylindrical sealing cavity (5), and the rubber sealing ring (11) is located in the circular fixing groove (10), and a group of fixing blocks (3) are evenly distributed on the outer surface of the cylindrical sealing cavity (5), and the group of fixing blocks (3) are respectively A fixing bolt (4) is vertically provided, and the lower end of the fixing bolt (4) is respectively connected to a fixing nut (2), and the fixing nut (2) is respectively fixed to the circular fixing plate (1); an oxygen bomb (12) is movably placed on the circular fixing plate (1) in the cylindrical sealed cavity (5), and the oxygen bomb (12) is connected to an ignition wire (6), and the ignition wire (6) is connected to the upper end surface of the cylindrical sealed cavity (5), and the ignition wire (6) outside the cylindrical sealed cavity (5) is connected to an ignition device (9); a differential pressure gauge (8) is connected to one side of the cylindrical sealed cavity (5) via a guide tube (7); Three fixing blocks (3) are evenly distributed on the outer surface of the cylindrical sealing cavity (5); The outer surface of the cylindrical sealing cavity (5) is provided with a heat-insulating layer (13); the circular fixing plate (1) is made of a heat-insulating material; The measurement method of the combustion heat teaching aid based on pressure measurement includes the following steps: A. Accurately weigh the mass of the ignition wire as m1, take the sample to be tested, press it into a tablet, and then accurately weigh the total mass of the pressed ignition wire and the sample to be tested as m2. The mass of the sample to be tested is m 样 =m2-m1, put the pressed ignition wire and the sample to be tested into the oxygen bomb (12), and then fill the oxygen bomb (12) with oxygen; B. Place the oxygen bomb (12) on the circular fixing plate (1), connect the oxygen bomb (12) to the ignition wire (6), then place the lower end of the cylindrical sealing cavity (5) into the annular fixing groove (10), then respectively connect the fixing bolts (4) on the fixing block (3) with the fixing nuts (2) on the circular fixing plate (1), and press the rubber sealing ring (11) at the lower end of the cylindrical sealing cavity (5) into the annular fixing groove (10); C. After the initial pressure is recorded as P1 by the differential pressure gauge (8) connected to one side of the cylindrical sealed cavity (5) via the conduit (7), the ignition device (9) is controlled to ignite the oxygen bomb (12) via the ignition wire (6). When the pressure of the differential pressure gauge (8) rises to the maximum, the pressure is recorded as P2 by the differential pressure gauge (8), and the change value of the air pressure in the cavity before and after the combustion reaction is obtained, △P=P2-P1; D. By rotating the fixing bolt (4), the connection between the fixing bolt (4) and the fixing nut (2) is canceled, the cylindrical sealing cavity (5) is opened, the oxygen bomb (12) is taken out and opened, and the mass of the unburned ignition wire is accurately weighed as m3, i.e., the mass of the ignition alloy wire m 丝 =m1-m3; m 丝 ×Q 丝 +m 样 ×Q 样 =K×(P2-P1)=K×△P; Where: m 丝 : Ignition alloy wire mass, unit: g; Q 丝 : Combustion heat of ignition alloy wire, unit: kJ / g; msample: mass of the sample to be tested, unit: g; Q 样 : Sample combustion heat, unit: kJ / g; K: instrument heat capacity constant of the teaching aid, unit: kJ / Pa; △P: change in air pressure in the cavity before and after the combustion reaction, unit: Pa.

2. The measuring method of the combustion heat teaching aid based on pressure measurement according to claim 1, characterized in that: The sample to be tested is 0.2-0.3 g.

3. The measuring method of the combustion heat teaching aid based on pressure measurement according to claim 1, characterized in that: The K is the instrument heat capacity constant of the teaching aid. Unit: kJ / Pa. The constant K is calibrated using a sample with known heat of combustion.

Images