Porous material aperture testing equipment and application

Abstract

The invention provides porous material aperture testing equipment and application, and belongs to the field of porous material aperture testing equipment. The porous material aperture testing equipment comprises a pipeline system, a fan and a control system, the pipeline system comprises a pipeline, one end of the pipeline is provided with a sample placing structure, the other end of the pipeline is flexibly connected with the fan, the end, provided with the sample placing structure, of the pipeline is provided with a micro differential pressure gauge, and the pipeline is further provided with an orifice plate flowmeter; and the control system is respectively connected with the fan, the micro differential pressure gauge and the orifice plate flowmeter. The pore diameter of the porous material can be rapidly and accurately measured, time and labor are saved, and reproducibility is good.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of porous material pore size testing equipment, and particularly relates to a porous material pore size testing device and application. BACKGROUND

[0002] Pore size is a very important index of porous materials, and the pore size has a decisive effect on the application of porous materials, so the stable and accurate measurement of the pore size of porous materials is of great significance. At present, the measurement methods of pore size and pore size distribution include direct method and indirect method; the direct method is to directly observe the pore size of the local surface of the material by visual observation, or by optical photograph or electron microscope combined with computer image analysis technology; the indirect method is to indirectly calculate the pore size of the material by measuring the physical quantities related to the pore size of the material, and the indirect method mainly includes bubble point pressure method, mercury intrusion method and the like.

[0003] Due to the complexity of the structure of the porous material, the pores have bending, non-directionality and randomness, and it is time-consuming and laborious to measure the PPI (pores per inch) of the porous material by direct observation, and the accuracy is low and the reproducibility is poor. The existing indirect method is only limited to paper research, and there is no real mature device, and the measurement result error is also large, and some even reaches ± 30%. SUMMARY

[0004] The purpose of the present application is to solve the problems existing in the prior art, and to provide a porous material pore size testing device and application, which can quickly and accurately measure the pore size of the porous material, save time and effort, and has good reproducibility.

[0005] The present application is realized by the following technical solutions:

[0006] In a first aspect, the present application provides a porous material pore size testing device, comprising a pipeline system, a fan and a control system.

[0007] The pipeline system comprises a pipeline, one end of the pipeline is provided with a sample placement structure, the other end is soft-connected with the fan, one end of the pipeline provided with the sample placement structure is installed with a differential pressure gauge, and the pipeline is further provided with a hole plate flowmeter.

[0008] The control system is connected with the fan, the differential pressure gauge and the hole plate flowmeter respectively.

[0009] Further improvements of the present application are as follows:

[0010] The pipeline comprises a reduced diameter section and a main pipe section, one end of the reduced diameter section with a large inner diameter is provided with the sample placement structure, and the other end with a small inner diameter is connected with the main pipe section.

[0011] The main pipe section is connected with the fan through a polyurethane hose.

[0012] The further improvement of the present application is:

[0013] The sample placing structure comprises a cross-shaped support frame, and a fixing ring is arranged at the outermost circle of the cross-shaped support frame.

[0014] The further improvement of the present application is:

[0015] A plurality of circular reinforcing ribs are sequentially arranged on the cross-shaped support frame and in the fixing ring.

[0016] The further improvement of the present application is:

[0017] The test device further comprises a flow regulating valve arranged on the pipeline and a temperature / humidity sensor arranged in the pipeline, and the temperature / humidity sensor is further connected with the control system.

[0018] The further improvement of the present application is:

[0019] The control system comprises:

[0020] A control module is connected with the fan, and is used for controlling start and stop of the fan and adjusting rotating speed of the fan.

[0021] A receiving and storing module is connected with the micro differential pressure meter, the orifice flow meter and the temperature / humidity sensor, and is used for receiving and storing measurement values of the orifice flow meter, the micro differential pressure meter and the temperature / humidity sensor.

[0022] A data processing module is used for calculating pressure drop of a sample with a standard thickness of 25.4 mm according to pressure drops measured by the micro pressure difference meter and the orifice flow meter, establishing a quantitative relationship between the pressure drop and PPI of the sample with the standard thickness of 25.4 mm, and drawing a standard curve; and is further used for calculating PPI of a sample to be measured according to the standard curve and pressure drop of the sample to be measured with the standard thickness of 25.4 mm.

[0023] In a second aspect, the present application provides a method for testing pore size of a porous material, comprising:

[0024] A standard curve is drawn by sequentially placing a plurality of porous material samples with the same material and different PPI values in the porous material pore size test device according to any one of claims 1-6, taking air as a medium, measuring pressure drop of the air flowing through the porous material sample, then obtaining pressure drop of the sample with a standard thickness of 25.4 mm, and further establishing a quantitative relationship between the pressure drop and PPI of the sample with the standard thickness of 25.4 mm when the standard orifice differential pressure Δp2 is constant, and drawing a standard curve.

[0025] The sample to be tested is placed in the porous material pore size testing device as described in any one of claims 1-6. Air is used as the medium to measure the pressure drop when air flows through the porous material sample and to obtain the pressure drop at a standard thickness of 25.4 mm for the sample to be tested. Furthermore, the pressure drop at a standard thickness of 25.4 mm for the sample to be tested is obtained when the pressure difference Δp2 of the standard orifice plate is constant.

[0026] When the obtained standard orifice plate pressure difference Δp2 is constant, the pressure drop of the sample under a standard thickness of 25.4 mm is substituted into the plotted standard curve to obtain the PPI value of the sample.

[0027] A further improvement of the present invention is that:

[0028] The process for obtaining the pressure drop at a standard sample thickness of 25.4 mm is as follows:

[0029] First, place the sample face down against the sample placement structure. By setting the fan frequency, obtain the pressure drop reading Δp1 of the differential pressure gauge and the pressure drop reading Δp2 of the pressure transmitter in the orifice flow meter at different frequencies.

[0030] Then, the sample is placed with its reverse side pressed against the sample placement structure. By setting the fan frequency, the pressure drop reading Δp1 of the differential pressure gauge and the pressure drop reading Δp2 of the pressure transmitter in the orifice flow meter are obtained at different frequencies.

[0031] Pressure drop Δp of the sample 样品 Obtained through formula (I):

[0032]

[0033] In equation (I), Δp1 is the reading of the differential pressure gauge, Pa; Δp2 is the reading of the pressure transmitter in the orifice flowmeter, i.e., the standard orifice plate differential pressure, Pa; ζ 进口 ζ is the resistance coefficient at the pipe inlet; 孔板 d1 is the resistance coefficient of the orifice plate; d2 is the inner diameter of the main pipe section in the pipeline, mm; d1 is the inner diameter of the pipe inlet, that is, the inner diameter of the larger inner diameter end of the necked section in the pipeline, mm.

[0034] The pressure drop ΔP of the standard sample thickness of 25.40 mm 25.4 The following can be obtained through formula (II):

[0035]

[0036] A further improvement of the present invention is that:

[0037] When the standard orifice plate pressure difference Δp2 is constant, the pressure drop ΔP corresponding to a standard sample thickness of 25.4 mm is obtained. 25.4 The specific operations include:

[0038] Due to the pressure drop Δp corresponding to the standard thickness of the sample at different frequencies. 25.4 It is proportional to the standard orifice plate pressure difference Δp2, with Δp 25.4 Plotting Δp1 on the ordinate and Δp2 on the abscissa, and obtaining Δp through linear fitting. 25.4 The linear relationship between Δp2 and the standard orifice plate pressure difference Δp2 is used to calculate the pressure drop corresponding to a standard sample thickness of 25.4 mm when the standard orifice plate pressure difference Δp2 is 200 Pa, 400 Pa, 600 Pa, and 800 Pa.

[0039] At least four groups of samples of the same PPI specification should be prepared, and the above operation should be repeated for each group. Calculate the pressure drop corresponding to a standard sample thickness of 25.4 mm when the standard orifice plate pressure difference Δp2 is 200 Pa, 400 Pa, 600 Pa, and 800 Pa. Calculate the average value to obtain the pressure drop value Δp2 corresponding to a standard sample thickness of 25.4 mm when the standard orifice plate pressure difference Δp2 is 200 Pa, 400 Pa, 600 Pa, and 800 Pa. 25.4 .

[0040] A third aspect of the present invention provides the application of the above-described porous material pore size testing equipment in porous side material pore size testing.

[0041] Compared with the prior art, the beneficial effects of the present invention are:

[0042] This invention indirectly measures the PPI by measuring the pressure drop when gas flows through a porous material of a certain thickness. The result has extremely low error compared with the direct method (image analysis method), and the test method is simple and easy to implement. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the structure of a porous material pore size testing device provided by the present invention;

[0044] Figure 2 This is a schematic diagram of the piping system.

[0045] Figure 3 This is a schematic diagram of the sample support structure;

[0046] In the figure, 1. Pipe, 2. Sample placement structure, 201. Cross-shaped support frame, 202. Fixing ring, 203. Reinforcing rib, 3. Fan, 4. Differential pressure gauge, 5. Orifice plate flow meter, 6. Flow regulating valve, 7. Hose, 8. Control system.

[0047] Figure 4 The photographs were taken with a digital camera of the surface of the mesh polyurethane foam sample.

[0048] Figure 5is the relationship between the reading Δp1 of the micro differential pressure gauge when empty and the reading Δp2 of the pressure transmitter in the orifice flow meter;

[0049] Figure 6a is the pressure drop test result of the reticulated polyurethane foam S1-1 in the embodiment of the present application;

[0050] Figure 6b is the pressure drop test result of the reticulated polyurethane foam S1-2 in the embodiment of the present application;

[0051] Figure 6c is the pressure drop test result of the reticulated polyurethane foam S1-3 in the embodiment of the present application;

[0052] Figure 6d is the pressure drop test result of the reticulated polyurethane foam S1-4 in the embodiment of the present application;

[0053] Figure 7a is the PPI standard curve of the reticulated polyurethane foam when Δp2 = 200 Pa in the embodiment of the present application;

[0054] Figure 7b is the PPI standard curve of the reticulated polyurethane foam when Δp2 = 400 Pa in the embodiment of the present application;

[0055] Figure 7c is the PPI standard curve of the reticulated polyurethane foam when Δp2 = 600 Pa in the embodiment of the present application;

[0056] Figure 7d is the PPI standard curve of the reticulated polyurethane foam when Δp2 = 800 Pa in the embodiment of the present application. DETAILED DESCRIPTION

[0057] The present application will be further described in detail below with reference to the accompanying drawings:

[0058] Research shows that it is an effective method to indirectly measure the PPI of a porous material by measuring the pressure drop of the gas flowing through the porous material of a certain thickness. The PPI is the number of cells per inch length on the surface of the sample.

[0059] According to the famous Ergun equation, when the gas flows through the porous material of a certain thickness, the pressure of the gas will decrease due to the hindering effect of the porous material on the gas flow. The pressure drop per unit thickness is:

[0060]

[0061] In the formula, Δp is the pressure drop, Pa; L is the thickness of the porous material in the direction of the gas flow, m; ε is the porosity of the porous material, dimensionless; d is the equivalent diameter of the porous material (related to PPI), m; μ is the viscosity of the gas, Pa·s; and ρ is the density of the gas, kg·m-3 u is the average flow velocity of the gas (calculated based on the entire flow cross section), m·s -1 .

[0062] The first term on the right side of equation (a) reflects the influence of viscous force on pressure drop, which is proportional to the first power of flow velocity; the second term reflects the influence of inertial force on pressure drop, which is proportional to the second power of flow velocity. As can be seen from equation (a), the factors affecting the pressure drop of gas flowing through a porous material include:

[0063] First, the structure of the porous material, including porosity and equivalent diameter. When other conditions remain unchanged, the greater the porosity and the equivalent diameter of the porous material, the smaller the pressure drop of the gas.

[0064] Second, the physical properties of the gas, including viscosity and density. When other conditions remain unchanged, the greater the viscosity and density of the gas, the greater the pressure drop of the gas.

[0065] Third, the flow velocity of the gas. When other conditions remain unchanged, the greater the flow velocity of the gas, the greater the pressure drop of the gas, and the pressure drop is proportional to the square of the flow velocity of the gas.

[0066] Let

[0067]

[0068]

[0069] Then

[0070]

[0071] As can be seen from equation (d), under certain conditions (the density and viscosity of the gas are constant) and when measuring the pressure drop of a gas flowing through a specific porous material (the porosity and equivalent diameter are constant), the pressure drop per unit thickness is a quadratic function of the flow velocity of the gas.

[0072] The porous material pore size testing equipment of the present application uses air as the medium, measures the pressure drop of air flowing through a porous material sample of a certain thickness, establishes a quantitative relationship between pressure drop and PPI, draws a standard curve graph, and calculates the PPI value of the sample to be tested.

[0073] As shown in Figure 1 and Figure 2 , the present application provides a porous material pore size testing equipment, which comprises a pipeline system, a fan and a control system.

[0074] The pipeline system comprises a pipeline 1, one end of the pipeline 1 is provided with a sample placement structure 2, the other end is connected with a fan 31 in a soft connection mode, the pipeline 1 is provided with a differential pressure gauge 4 at the end provided with the sample placement structure 2, the pipeline 1 is further provided with a orifice flowmeter 5 and a flow regulating valve 6, respectively, and the pipeline 1 is provided with a temperature / humidity sensor (not shown in the figure);

[0075] The control system 8 is connected with the fan 3, the differential pressure gauge 4, the orifice flowmeter 5 and the temperature / humidity sensor, respectively.

[0076] The porous material pore size testing device further comprises a support rack, and the pipeline 1 is arranged on the support rack.

[0077] The fan 3 is connected with the pipeline 1 in a soft connection mode, is used for driving air to flow through the sample to be tested, and is used for stably flowing in the pipeline 1 at a certain speed, the rotating speed of the fan 3 is adjusted through a frequency converter, the flow (flow rate) of the air in the pipeline 1 is adjusted by changing the rotating speed of the fan 3 and the opening of the flow regulating valve 6 arranged on the pipeline 1, and the orifice flowmeter 5 is used for measuring, and the pressure drop of the air flowing through the sample to be tested is measured by the differential pressure gauge 4.

[0078] The control system 8 is used for controlling the start and stop of the fan 3 and adjusting the rotating speed of the fan 3, connecting the orifice flowmeter 5, the differential pressure gauge 4 and the temperature / humidity sensor, receiving, storing and processing the measured data, including the air flow (flow rate) in the pipeline system, the pressure drop of the air flowing through the sample to be tested and the temperature / humidity and the like.

[0079] As a preferred embodiment of the present application, the pipeline 1 is made of SUS304 stainless steel, and comprises a necked section and a main pipe section, preferably, the inner diameter of the necked section is linearly reduced from 254 mm to 151 mm from one end to the other end, the end of the necked section with a large inner diameter is provided with the sample placement structure 2, and a cylindrical sample with a diameter of 254 mm (10 in) and a thickness of 25.4 mm (1.0 in) can be placed and fixed, and the end with a small inner diameter is connected with the main pipe section;

[0080] The inner diameter of the main pipe section is 151 mm, the main pipe section is connected with the fan 3 through a polyurethane hose 7, specifically, one end of the polyurethane hose 7 is connected with the main pipe section of the pipeline 1, and the other end is connected with the air outlet of the fan 3, so as to reduce the influence of fan vibration on the test result.

[0081] As a preferred embodiment of the present application, as shown in Figure 3As shown, the sample placement structure 2 comprises a cross-shaped support frame 201, the outermost circle of which is provided with a fixed circular ring 202 fixedly connected to the end of the larger inner diameter end of the reduced diameter section of the pipeline 1, preferably, the inner diameter of the fixed circular ring 202 is larger than the inner diameter of the larger inner diameter end of the reduced diameter section of the pipeline and smaller than the outer diameter of the larger inner diameter end of the reduced diameter section; a plurality of circular reinforcing ribs 203 are sequentially arranged on the cross-shaped support frame 201 and located in the fixed circular ring 202, which can ensure that the sample is flat and not deformed during the test. The circular reinforcing ribs 203 are preferably provided with two.

[0082] The material of the sample placement structure 2 is SUS304 stainless steel, which is processed by laser cutting.

[0083] As a preferred embodiment of the present application, the fan 3 is preferably a CF-2A multi-wing type centrifugal fan, the maximum power of which is 1.1kW, the rated voltage is 380V, the rated rotating speed is 2800rpm, the maximum air volume is 2258Nm 3 / h, the total pressure is 1150-839Pa, the noise is about 78 decibels, and the weight is 23kg.

[0084] The fan 3 is connected with a frequency converter.

[0085] As a preferred embodiment of the present application, the orifice plate flowmeter has the following comprehensive performance parameters: differential pressure range 0-2500Pa, differential pressure accuracy 0.1Pa, flow range 0-1100Nm 3 / h, flow accuracy 0.1Nm 3 / h, flow uncertainty ≤±0.82%, flow velocity range 0-17.1m / s, flow velocity accuracy 0.1m / s, and flow velocity uncertainty ≤±0.82%.

[0086] The orifice plate flowmeter can not only measure the air speed in the pipeline, but also measure the pressure drop flowing through the orifice plate, including the standard orifice plate, the pressure guide pipeline and the pressure transmitter.

[0087] When the orifice plate flowmeter is installed, the standard orifice plate is first installed in the pipeline 1, then the pressure transmitter is connected with the standard orifice plate through the pressure guide pipeline, and the pressure transmitter is arranged outside the pipeline 1.

[0088] As a preferred embodiment of the present application, the differential pressure meter 4 adopts an EJA-120A differential pressure transmitter for measuring the pressure drop when air flows through the to-be-measured sample.

[0089] The EJA-120A differential pressure transmitter is suitable for measuring a small differential pressure and then converting it into a 4-20mA DC current signal output.

[0090] The temperature / humidity sensor in the application adopts a ZS-1T-1H-SHT30-485 temperature / humidity transmitter for measuring the temperature and humidity of air.

[0091] As a preferred embodiment of the application, the control system 8 comprises:

[0092] The control module is connected with the fan 3 and the frequency converter, and is used for controlling the start and stop of the fan 3 and adjusting the rotating speed of the fan 3.

[0093] The receiving and storing module is connected with the differential pressure meter 4, the orifice flowmeter 5 and the temperature / humidity sensor, and is used for receiving and storing the measurement values of the differential pressure meter 4, the orifice flowmeter 5 and the temperature / humidity sensor.

[0094] The data processing module is used for calculating the pressure drop of the sample with a standard thickness of 254 mm according to the pressure drop measured by the differential pressure meter 4 and the orifice flowmeter 5, establishing a quantitative relationship between the pressure drop and PPI, and drawing a standard curve.

[0095] The embodiment of the application further provides a porous material pore diameter testing method, comprising:

[0096] Step 1, drawing a standard curve;

[0097] A plurality of porous material samples of the same material and different PPI values are sequentially placed in the device of the application, air is used as the medium, the pressure drop of air flowing through the porous material sample is measured, the pressure drop of the sample under the standard thickness is calculated, a quantitative relationship between the pressure drop of the sample under the standard thickness and PPI is established, and a standard curve is drawn; wherein the porous material sample is at least selected from three kinds.

[0098] Step 2, placing the sample to be measured in the device of the application, using air as the medium, measuring the pressure drop of air flowing through the porous material sample, and calculating the pressure drop of the sample to be measured under the standard thickness;

[0099] Step 3, substituting the pressure drop of the sample to be measured under the standard thickness calculated in step 2 into the standard curve drawn in step 1 to obtain the PPI value of the sample to be measured.

[0100] Embodiment:

[0101] I. Sample preparation

[0102] Three kinds of reticulated polyurethane foams with different PPI specifications (numbered S1, S2 and S3 respectively) are selected, the foams are cut into cylindrical standard samples by an electric heating wire cutting machine, the thickness is about 25.4 mm, the diameter is 250-252 mm, four standard samples of each specification of reticulated polyurethane foam are prepared, and the accurate thickness is measured.

[0103] II. Direct measurement of sample PPI

[0104] Submerge the standard sample into a milky liquid (e.g. milk) to a certain depth, make sure the upper surface of the sample is slightly higher than the liquid surface, take a picture of the upper surface of the sample with a digital camera (Fig. 1), then measure the aperture of the sample with open-source image analysis software ImageJ (1.54f), finally take the average value of the sample PPI, the results are shown in Table 1. Figure 4

[0105] Table 1. PPI measurement results of reticulated polyurethane foam

[0106]

[0107] III. Measurement of sample PPI with the device of the present application

[0108] 1. Empty load test (test with the device of the present application without sample)

[0109] As shown in Fig. 2, the differential pressure gauge 4 measures the pressure difference between the atmosphere and the back side of the sample in the pipe 1, including the pressure drop at the pipe inlet and the pressure drop of the sample. Figure 1 According to Darcy's formula, the reading of the differential pressure gauge 4 Δp1 (Pa) is:

[0110]

[0111] In the formula, ζ 进口 and ζ 样品 are the resistance coefficients of the pipe inlet and the sample, respectively; ρ is the density of air, kg·m -3 ; u1 is the average flow rate of air at the pipe inlet (based on the entire flow cross section), m·s -1 .

[0112] Similarly, the reading of the pressure transmitter in the orifice flowmeter Δp2 (Pa) is the pressure drop of the standard orifice:

[0113]

[0114] In the formula, ζ 孔板 is the resistance coefficient of the orifice; u2 is the average flow rate of air in the main pipe (based on the entire flow cross section), m·s -1 .

[0115] According to the continuity equation of fluid flow, u1 and u2 satisfy the following relationship:

[0116]

[0117]

[0118] ​​In the formula, d1 = 254 mm and d2 = 151 mm are the inner diameters of the pipe inlet and the main pipe, respectively.

[0119] From equations (1), (2), and (3), we can derive the following expression:

[0120]

[0121] As can be seen from equation (4), for a specific sample (ζ) 样品 (where ζ is a constant), Δp1 and Δp2 are proportional to different wind speeds; when no sample is placed in the pipe (ζ... 样品 =0), when no sample is placed, Δp1 = Δp 进口 Δp1 and Δp2 are also directly proportional to different wind speeds, as expressed by:

[0122]

[0123] Plot a graph with the reading Δp1 of the differential pressure gauge 4 as the ordinate and the reading Δp2 of the pressure transmitter as the abscissa. The result is as follows: Figure 5 As shown.

[0124] from Figure 5 It can be seen that under no-load conditions (ζ) 样品 =0), Δp1 and Δp2 are linearly related (R = 0). 2 >0.99), with a slope of 0.023, indicating good reproducibility.

[0125] 2. Sample PPI Measurement

[0126] (1) Plotting the standard curve

[0127] After the no-load test, the standard sample with the measured thickness was placed on the sample placement structure 2, and the pressure drop of the mesh polyurethane foam standard sample with different PPI specifications was measured respectively.

[0128] Specifically, during the measurement, the standard sample is first placed with its front side pressed against the sample placement structure 2. By setting the fan frequency, the pressure drop reading Δp1 of the differential pressure gauge 4 and the pressure drop reading Δp2 of the pressure transmitter in the orifice flowmeter are obtained at different frequencies. Preferably, at least three sets of pressure drop readings Δp1 of the differential pressure gauge 4 and pressure drop readings Δp2 of the pressure transmitter in the orifice flowmeter are obtained at different frequencies. In this embodiment of the invention, four sets are obtained.

[0129] Then the standard sample is placed on the sample placement structure 2 with the reverse side close to the sample placement structure 2. By setting the frequency of the fan, the pressure drop readings Δp1 of the differential pressure gauge 4 and the pressure drop readings Δp2 of the pressure transmitter in the orifice flowmeter under different frequencies are obtained. Preferably, at least three groups of pressure drop readings Δp1 of the differential pressure gauge 4 and the pressure drop readings Δp2 of the pressure transmitter in the orifice flowmeter under different frequencies are obtained. In the embodiment of the present application, four groups of pressure drop readings Δp1 of the differential pressure gauge 4 and the pressure drop readings Δp2 of the pressure transmitter in the orifice flowmeter under different frequencies are obtained.

[0130] Taking the standard sample S1 as an example, Table 2 is the pressure drop measurement results of the reticulated polyurethane foam standard sample S1. In Table 2, S1-1, S1-2, S1-3 and S1-4 are respectively the test results of four parallel standard samples of the same PPI specification.

[0131] It should be noted that along the sample axis direction, one of the end faces of the sample is the front face, and the other end face opposite to the front face is the reverse face.

[0132] As shown in formula (1), the differential pressure gauge 4 measures the pressure difference between the atmospheric pressure and the pressure on the back side of the sample in the pipeline 1, which includes the pressure drop at the pipeline inlet and the real pressure drop of the sample:

[0133]

[0134] Let

[0135]

[0136]

[0137] Then

[0138] Δp1= Δp 进口 + Δp 样品 (9)

[0139] Or

[0140] ΔP 样品 = Δp1- Δp 进口 (10)

[0141] Substituting formula (5) into formula (10) can obtain

[0142]

[0143] Formula (11) can be used to correct the influence of the pressure drop at the pipeline inlet on the measurement results. The results are shown in the second last column of Table 2, and the pressure drop Δp 样品 only generated by the sample itself is obtained.

[0144] The pressure drop of the sample is proportional to the thickness of the sample. Therefore, the pressure drop ΔP 25.4 of the standard thickness (25.40 mm) of the sample is calculated using formula (12):

[0145]

[0146] The pressure drop of the standard thickness sample is shown in the last column of Table 2.

[0147] The measurement and calculation methods for standard samples S2, S3, and S4 are the same as those for standard sample S1, and will not be repeated here.

[0148] Table 2. Pressure drop measurement results of reticulated polyurethane foam S1

[0149]

[0150] Similarly, the pressure drop of a standard thickness sample can also be expressed using Darcy's formula:

[0151]

[0152] Combining equations (2) and (3), we can solve for:

[0153]

[0154] As can be seen from equation (14), for a specific sample (ζ) 样品 (where Δp is a constant, representing a sample with a standard thickness of 25.4 mm). At different frequencies, the pressure drop Δp of the standard thickness sample... 25.4 It is proportional to the pressure difference Δp2 of the standard orifice plate. Taking the sample S1-1 as an example, Δp 25.4 Plotting Δp2 on the ordinate and Δp2 on the abscissa, the result is as follows: Figure 6a Linear fitting yields Δp 25.4 The linear relationship with Δp2; the fitting results for standard samples S1-2, S1-3, and S1-4 are as follows. Figure 6b , 6c And 6d.

[0155] from Figures 6a to 6d It can be seen that Δp at different frequencies 25.4 Linearly dependent on Δp2 (R 2 >0.99). Therefore, it can be used separately. Figures 6a to 6d The linear relationship was used to calculate the pressure drop values ​​of standard samples S1-2, S1-3, and S1-4 when the standard orifice plate pressure difference Δp2 was 200 Pa. Then, the average value was calculated, which is the pressure drop Δp of the standard thickness sample when the standard orifice plate pressure difference Δp2 was 200 Pa. 25.4 The results are shown in Table 3.

[0156] Table 3 shows the pressure drop at standard thickness (25.40 mm) corresponding to the standard orifice plate pressure difference.

[0157]

[0158] When the standard orifice plate pressure difference Δp2 is 200 Pa, the pressure drop Δp is based on the standard sample thickness in Table 3. 25.4 Plotting the standard curve of polyurethane foam standard samples with the x-axis as the horizontal axis and the PPI (measured directly) of the standard sample as the y-axis, we obtain the standard curve when the pressure difference Δp2 of the standard orifice plate is 200 Pa. Figure 7a As shown, Figures 7b to 7d The standard curves are shown for samples when the pressure difference Δp2 of the standard orifice plate is 400 Pa, 600 Pa, and 800 Pa, respectively.

[0159] (2) PPI of the sample to be tested

[0160] Four cylindrical test samples (numbered A1-1, A1-2, A1-3 and A1-4) of mesh polyurethane foam were cut using a hot wire cutter. The samples had a thickness of approximately 25.4 mm and a diameter of approximately 250–252 mm. The accurate thickness of each sample was then measured.

[0161] Taking A1-1 as an example, the sample to be tested, A1-1, is first placed with its front side pressed against the sample placement structure 2. By setting the fan frequency, the pressure drop reading Δp1 of the differential pressure gauge 4 and the pressure drop reading Δp2 of the pressure transmitter in the orifice flowmeter are obtained at different frequencies. Preferably, at least three sets of pressure drop readings Δp1 of the differential pressure gauge 4 and pressure drop readings Δp2 of the pressure transmitter in the orifice flowmeter are obtained at different frequencies. In this embodiment of the invention, four sets are obtained.

[0162] Then, the sample A1-1 to be tested is placed with its reverse side pressed against the sample placement structure 2. By setting the fan frequency, the pressure drop reading Δp1 of the differential pressure gauge 4 and the pressure drop reading Δp2 of the pressure transmitter in the orifice flowmeter are obtained at different frequencies. Preferably, at least 3 sets of pressure drop readings Δp1 of the differential pressure gauge 4 and pressure drop readings Δp2 of the pressure transmitter in the orifice flowmeter at different frequencies are obtained. In this embodiment of the invention, 4 sets are obtained.

[0163] The pressure drop ΔP corresponding to the standard thickness (25.4 mm) of the sample A1-1 under different frequencies was calculated using formulas (11) and (12), respectively. 25.4 Thus, for the same sample to be tested, a total of 8 sets of data were obtained from the front and back tests.

[0164] Using the same method, the pressure drop ΔP corresponding to the standard thickness (25.4 mm) of the test samples A1-2, A1-3, and A1-4 at different frequencies was measured and calculated. 25.4 .

[0165] Due to the pressure drop Δp corresponding to the standard thickness of the sample at different frequencies. 25.4 It is proportional to the pressure difference Δp2 of the standard orifice plate. Taking the sample A1-1 as an example, Δp25.4 For the ordinate, Δp2 is the abscissa, and a linear fitting is performed to obtain the linear relationship of Δp 25.4 With Δp2, and the linear relationship is used to calculate the pressure drop value corresponding to the standard orifice plate pressure difference Δp2 of 200 Pa; the same method is used to calculate the pressure drop values of the sample A1-2, A1-3 and A1-4 corresponding to the standard orifice plate pressure difference Δp2 of 200 Pa, and then an average value is obtained, which is the pressure drop Δp of the standard thickness corresponding to the standard orifice plate pressure difference Δp2 of 200 Pa of the sample to be measured. 25.4 .

[0166] The pressure drop Δp 25.4 is brought into the standard curve corresponding to the standard orifice plate pressure difference Δp2 of 200 Pa to obtain the PPI of the sample to be measured.

[0167] Similarly, the pressure drop Δp 25.4 of the standard thickness corresponding to the standard orifice plate pressure difference Δp2 of 400 Pa, 600 Pa and 800 Pa of the sample to be measured can also be obtained, which is substituted into the corresponding standard curve to obtain the PPI of the sample to be measured.

[0168] Through calculation, the PPI of the sample to be measured measured and calculated by the equipment of the present application is 6.38±0.10, and the PPI obtained by the direct method is 6.38, so it can be seen that the present application can accurately measure the PPI of the reticular polyurethane foam sample, and the error with the result measured by the direct method is extremely low, and the test method is simple and easy to operate.

[0169] In the description of the present application, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected", "connected" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected, it can be mechanically connected, or it can be electrically connected, it can be directly connected, or it can be indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0170] In the description of the present application, unless otherwise stated, the terms "upper", "lower", "left", "right", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore it cannot be understood as a limitation on the present application.

[0171] The above technical solution is only one embodiment of the present application, and for those skilled in the art, on the basis of the disclosed principles, various types of improvements or modifications can be easily made, and the technical solution described in the above specific embodiments is not limited. Therefore, the above description is only preferred, and is not limited in meaning.

Claims

1. A porous material pore size testing device, characterized in that, This includes piping systems, fans, and control systems; The pipeline system includes a pipe, one end of which is provided with a sample placement structure, and the other end is flexibly connected to the fan. A differential pressure gauge is installed at the end of the pipe with the sample placement structure, and orifice plate flow meters are also installed on the pipe. The control system is connected to the fan, the differential pressure gauge and the orifice flow meter respectively.

2. The porous material pore size testing device according to claim 1, characterized in that, The pipeline includes a reduced diameter section and a main pipe section. The sample placement structure is provided at the larger inner diameter end of the reduced diameter section, and the smaller inner diameter end is connected to the main pipe section. The main pipe is connected to the fan via a polyurethane hose.

3. The porous material pore size testing device according to claim 2, characterized in that, The sample placement structure includes a cross-shaped support frame, and the outermost ring of the cross-shaped support frame is provided with a fixing ring, which is fixedly connected to the end of the pipe with the larger inner diameter of the reduced diameter section.

4. The porous material pore size testing device according to claim 3, characterized in that, Multiple circular reinforcing ribs are sequentially arranged on the cross-shaped support frame and inside the fixed ring.

5. The porous material pore size testing device according to claim 1, characterized in that, The testing equipment also includes a flow regulating valve installed on the pipeline and a temperature / humidity sensor installed inside the pipeline, the temperature / humidity sensor being connected to the control system.

6. The porous material pore size testing device according to any one of claims 1-5, characterized in that, The control system includes: A control module, connected to the fan, is used to control the start and stop of the fan and adjust the fan speed; A receiving and storage module is connected to the differential pressure gauge, orifice plate flow meter, and temperature / humidity sensor to receive and store the measured values ​​from the orifice plate flow meter, differential pressure gauge, and temperature / humidity sensor. The data processing module is used to calculate the pressure drop of a standard 25.4mm thick sample based on the pressure drop measured by the differential pressure gauge and the orifice plate flow meter, establish a quantitative relationship between pressure drop and PPI, and plot a standard curve; it is also used to calculate the PPI value of the sample based on the standard curve and the pressure drop of the standard 25.4mm thick sample.

7. A method for testing the pore size of porous materials, characterized in that, include: To create a standard curve: Multiple porous material samples of the same material but with different PPI values ​​are placed in the porous material pore size testing device as described in any one of claims 1-6. Using air as the medium, the pressure drop when air flows through the porous material sample is measured. Then, the pressure drop at a standard thickness of 25.4 mm is obtained. Further, a quantitative relationship between the pressure drop at a standard thickness of 25.4 mm and the PPI is established when the pressure difference Δp2 of the standard orifice plate is constant. A standard curve is then plotted. The sample to be tested is placed in the porous material pore size testing device as described in any one of claims 1-6. Air is used as the medium to measure the pressure drop when air flows through the porous material sample and to obtain the pressure drop at a standard thickness of 25.4 mm for the sample to be tested. Furthermore, the pressure drop at a standard thickness of 25.4 mm for the sample to be tested is obtained when the pressure difference Δp2 of the standard orifice plate is constant. When the obtained standard orifice plate pressure difference Δp2 is constant, the pressure drop of the sample under a standard thickness of 25.4 mm is substituted into the plotted standard curve to obtain the PPI value of the sample.

8. The method for testing the pore size of porous materials according to claim 7, characterized in that, The process for obtaining the pressure drop at a standard sample thickness of 25.4 mm is as follows: First, place the sample face down against the sample placement structure. By setting the fan frequency, obtain the pressure drop reading Δp1 of the differential pressure gauge and the pressure drop reading Δp2 of the pressure transmitter in the orifice flow meter at different frequencies. Then, the sample is placed with its reverse side pressed against the sample placement structure. By setting the fan frequency, the pressure drop reading Δp1 of the differential pressure gauge and the pressure drop reading Δp2 of the pressure transmitter in the orifice flow meter are obtained at different frequencies. Pressure drop Δp of the sample 样品 Obtained through formula (I): In equation (I), Δp1 is the reading of the differential pressure gauge, Pa; Δp2 is the reading of the pressure transmitter in the orifice flowmeter, i.e., the standard orifice plate differential pressure, Pa; ζ 进口 ζ is the resistance coefficient at the pipe inlet; 孔板 d1 is the resistance coefficient of the orifice plate; d2 is the inner diameter of the main pipe section in the pipeline, mm; d1 is the inner diameter of the pipe inlet, that is, the inner diameter of the larger inner diameter end of the necked section in the pipeline, mm. Pressure drop ΔP of a standard sample thickness of 25.40 mm 25.4 The following can be obtained through formula (II):

9. The method for testing the pore size of porous materials according to claim 7 or 8, characterized in that, When the standard orifice plate pressure difference Δp2 is constant, the pressure drop ΔP corresponding to a standard sample thickness of 25.4 mm is obtained. 25.4 The specific operations include: Due to the pressure drop Δp corresponding to the standard thickness of the sample at different frequencies. 25.4 It is proportional to the standard orifice plate pressure difference Δp2, with Δp 25.4 Plotting Δp1 on the ordinate and Δp2 on the abscissa, and obtaining Δp through linear fitting. 25.4 The linear relationship between Δp2 and the standard orifice plate pressure difference Δp2 is used to calculate the pressure drop corresponding to a standard sample thickness of 25.4 mm when the standard orifice plate pressure difference Δp2 is 200 Pa, 400 Pa, 600 Pa, and 800 Pa. At least four groups of samples of the same PPI specification should be prepared, and the above operation should be repeated for each group. Calculate the pressure drop corresponding to a standard sample thickness of 25.4 mm when the standard orifice plate pressure difference Δp2 is 200 Pa, 400 Pa, 600 Pa, and 800 Pa. Calculate the average value to obtain the pressure drop Δp2 corresponding to a standard sample thickness of 25.4 mm when the standard orifice plate pressure difference Δp2 is 200 Pa, 400 Pa, 600 Pa, and 800 Pa. 25.4 .

10. The application of the porous material pore size testing device as described in any one of claims 1-6 in the pore size testing of porous side materials.

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