Fabric heat reflection performance detection equipment

Abstract

The utility model relates to the textile field, in particular to fabric heat reflection performance detection equipment which is composed of a base and an instrument cover, the base comprises a bottom plate, a test plate, a protection plate, a wooden frame and a heat insulation layer, the bottom plate, the test plate and the protection plate are provided with temperature control devices and can be kept at a constant temperature after being heated, and the protection plate annularly surrounds the test plate; the instrument cover is arranged above the base and forms a closed space with the base; an instrument cover door is arranged on one side of the instrument cover, an instrument cover skylight is arranged above the instrument cover, and an in-cover temperature sensor is arranged inside the instrument cover; an overhead frame is arranged above the test plate, the maximum edge of the inner side of the overhead frame does not exceed the test plate, an overhead frame support of the overhead frame is made of a heat insulation material, and the inner surface and the outer surface of the overhead frame support are wrapped by aluminum-foil paper; an in-frame temperature sensor is arranged on the inner side of the overhead frame close to the upper end. According to the invention, the blank of fabric heat reflection performance detection can be filled.

Description

Technical Field

[0001] This invention relates to the field of textile testing, and more specifically to a device for testing the thermal reflectance properties of fabrics. Background Technology

[0002] In recent years, fabrics with heat-reflective properties have emerged. These fabrics are coated with a layer of highly reflective materials such as aluminum foil to reflect external solar heat radiation. They are used to make insulated tents and umbrellas to prevent rapid heat accumulation during outdoor work, or to make firefighter suits to reduce the harm of heat radiation to firefighters. Applying these fabrics to thermal clothing can reflect most of the infrared radiation emitted by the human body, locking heat inside and reducing heat loss, thus providing good insulation. Related research shows that when the outside temperature drops, the human body loses 54% to 60% of its total heat loss through infrared radiation. Therefore, improving the heat-reflective properties of fabrics can achieve good insulation without increasing fabric thickness or using better insulation materials.

[0003] Currently, the most widely used testing method for measuring the heat transfer performance of thermal insulation and cold-resistant fabrics is GB / T 35762-2017 "Textiles - Test Method for Heat Transfer Performance - Plate Method". The matching fabric insulation tester can measure the insulation performance of ordinary fabrics. The measurement results are generally expressed as Clo value. The higher the Clo value, the better the insulation performance. However, this instrument is not suitable for testing fabrics with heat reflection function. There is currently a lack of relevant methods and instruments for testing the insulation performance of fabrics with heat reflection function.

[0004] A fabric thermal insulation testing machine, model ASTM-100A, with serial number MXJ-05-043, manufactured by Daiei Scientific Instruments Co., Ltd., Japan, is used for testing the thermal insulation performance of fabrics. The instrument mainly consists of a test plate, a protective plate, a base plate, and an electrical control device. The testing principle is as follows: the test plate is located in the center of the instrument, surrounded by isothermal protective and base plates with air, blocking heat transfer. Therefore, the power dissipated by the test plate can only be transferred through the exposed upper surface. The thermal insulation performance of the fabric is evaluated by measuring the thermal insulation power when the test plate is exposed and covered by fabric, i.e., the difference between the power of the empty plate and the power of the sample. The greater the difference in power, the better the thermal insulation effect. The upper surface of the test plate is treated with blackening or painting to achieve a surface reflectivity of approximately 0.95. During the test, the surface temperature is controlled to be stable at 35.0℃. The surface reflectivity and temperature are close to those of human skin to simulate the wearing conditions.

[0005] There are three ways heat energy is transferred: conduction, convection, and radiation. Fabrics with heat-reflective properties can reflect the heat radiation they receive back, reducing heat absorption. When using a fabric insulation testing machine, the test plate is in direct contact with the fabric, resulting in low thermal resistance. The energy transmitted through heat conduction is far greater than the energy radiated by heat, making it unsuitable for testing the insulation performance of heat-reflective fabrics. Summary of the Invention

[0006] Based on the above technical background and the current need for testing the thermal insulation performance of textiles, this invention provides a device and method for testing the thermal reflectivity of fabrics.

[0007] A fabric heat reflectance performance testing device consists of a base and an instrument cover. The base includes a base plate, a test plate, a protective plate, a wooden frame, and a heat insulation layer. The base plate, test plate, and protective plate are equipped with temperature control devices and can all be heated and maintained at a constant temperature to simulate the human body environment, which is set to (35±0.1)℃. The protective plate surrounds the test plate in a ring shape, that is, the test plate is located in the center of the protective plate, and the material can be aluminum or copper metal plate.

[0008] Temperature sensors and temperature controllers are installed on the outer surfaces of the base plate, test plate, and protection plate near the plate to ensure that the temperature of each plate is constant with an accuracy of ±0.3℃. An overhead frame is installed on the test plate. The maximum edge of the inner side of the overhead frame does not extend beyond the test plate. The support material of the overhead frame is heat-insulating material, such as heat-insulating foam. The inner and outer surfaces are covered with aluminum foil. The bottom of the overhead frame is firmly glued to the test plate and completely sealed to the test plate. A temperature sensor is installed inside the frame near the upper end.

[0009] The test board is square in shape with an area of ​​not less than 0.04㎡, for example, a square with a side length of at least 200mm. The shape of the suspended frame corresponds to that of the test board.

[0010] Furthermore, the height of the overhead frame is set at 25-35mm, and the thickness at 15-25mm.

[0011] Preferably, the height of the overhead frame is 30mm and the thickness is 20mm.

[0012] The instrument cover is positioned above the base, forming a sealed space with the base; one side of the instrument cover has an instrument cover door, the top of the instrument cover has an instrument cover skylight, and the inside of the cover has an internal temperature sensor.

[0013] 2. Test environment: Textile constant temperature and humidity laboratory, temperature set at 20℃, relative humidity set at 65%, temperature fluctuation within ±0.3℃ and relative humidity fluctuation within ±3% during the test.

[0014] 3. Test methods:

[0015] 3.1 Empty board test: Set the temperature of the test board, protection board, and base plate to 35℃. Preheat the instrument for a certain period of time, and wait for the temperature of the test board, protection board, and base plate to reach the set value. When the temperature difference is stable within 0.3℃ and the ambient temperature and humidity are stable, start the test.

[0016] 3.2 Sample preparation: According to GB / T 35762-2017 "Test Method for Heat Transfer Properties of Textiles - Flat Plate Method", the sample is pre-cut into a square with a side length of not less than 30cm to ensure that the test sample can completely cover the frame and is placed in the constant temperature and humidity room for full equilibration for 24h.

[0017] 3.3 The test sample is attached to the upper surface of the four-sided support of the frame with double-sided tape to ensure flatness and prevent air intrusion and disturbance; the instrument is set to test for 15 minutes after temperature equilibrium is reached, and the temperature of the test plate, protective plate and base plate is set to 35.0℃.

[0018] 3.4 According to the test method of GB / T 35762, after the empty plate test is completed, lay the test sample flat on the test plate and observe the temperature equilibrium before starting the sample test. After completion, repeat the sample test once without performing other operations, and take the arithmetic mean of the two data as the result; perform the test on the reverse side of the test sample in the same way.

[0019] 3.5 Numerical Calculation:

[0020] Within the relatively enclosed air layer of the overhead frame, heat conduction occurs due to the temperature difference between the upper and lower layers of air. As the thickness of the air layer increases, airflow and thermal convection can occur. Existing research indicates that when the air layer thickness is less than 16 mm, heat transfer occurs through conduction and radiation. As the air layer thickness continues to increase, the heat conduction value decreases, and thermal convection begins to occur and its value tends to increase.

[0021] In the sample test using an overhead frame, the air layer thickness was 30 mm. Under temperature equilibrium, the sum of the heat radiation, heat conduction, and heat convection power emitted by the heat preservation instrument test plate to the fabric was equal to the heat preservation power required to maintain the constant temperature of the test plate. Therefore, the heat radiation power can be indirectly obtained by subtracting the heat conduction power and heat convection power from the heat preservation power of the test plate. The heat radiation power is an indirectly calculated value. The calculation methods for heat conduction power and heat convection power are shown in equations (1) to (4), respectively.

[0022]

[0023] In the formula, Φ1 is the heat transfer power, A is the surface area, Δt is the temperature difference between the upper and lower air layers, δ is the thickness of the air layer, and λ is the thermal conductivity of the air.

[0024] The airflow within the interlayer is related to the temperature difference between the upper and lower air layers and the thickness of the interlayer, and depends on Gr. δnumber. Gr δ The larger the value, the more intense the interlayer convection; only when Gr... δ At temperatures ≤2430°C, flow is difficult to spread, and heat transfer within the interlayer is purely conductive. Assuming the temperature of the air gap varies uniformly in the vertical direction, and the thickness of the air gap δ = 0.03m (the height of the overhead frame in this embodiment is 30mm), the lower layer temperature t... h = (273+35) K, upper layer temperature tc = (273+27) K, average temperature of upper and lower layers 31℃, referring to the table in "Heat Transfer, 5th Edition" (Tao Wenquan), we know v = 22.9 × 10 -6 m 2 / s, λ=0.0268 W / (mK), Pr=0.701, g at 9.8m / s 2 Calculate Gr δ The value of the thermal convection power Φ2 is obtained by combining the value of the Nu coefficient.

[0025] Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the overall invention.

[0027] Figure 2 This is a schematic diagram of the base of the present invention.

[0028] Figure 3 This is a top view of the base of the present invention.

[0029] In the diagram: 1. Base, 2. Elevated frame, 3. Instrument cover, 4. Fabric to be tested, 11. Base plate, 12. Test plate, 13. Protective plate, 14. Wooden frame, 15. Insulation layer, 21. Elevated frame support, 22. Aluminum foil, 23. Temperature sensor inside the frame, 31. Instrument cover door, 32. Instrument cover skylight, 33. Temperature sensor inside the cover. Detailed Implementation

[0030] The invention will be further explained below with reference to the accompanying drawings.

[0031] like Figure 1 , 2 As shown, the heat reflection detection device consists of a base 1 and an instrument cover 3. The base includes a base plate 11, a test plate 12, a protective plate 13, a wooden frame 14, and a heat insulation layer 15. A suspended frame 2 is set on the test plate 12. The suspended frame 2 is a square frame formed by a suspended frame support 21. The suspended frame support 21 has a thickness of 20mm and a height of 30mm. The suspended frame support 21 is made of heat insulation material, such as heat insulation foam. The inner and outer surfaces of the suspended frame support 21 are covered with aluminum foil 22 and are flat. The bottom of the suspended frame 2 is sealed to the test plate 12. The sealing material can be aluminum foil. A temperature sensor 23 is set on the side wall of the suspended frame 2 near the upper end.

[0032] Temperature sensors and temperature controllers are installed on the outer surfaces of the base plate, test plate, and protection plate near the plate to ensure that the temperature of each plate is constant with an accuracy of ±0.3℃.

[0033] The instrument cover 3 is positioned above the base 1 and forms a sealed space with the base 1; one side of the instrument cover 1 is provided with an instrument cover door 31, the top is provided with an instrument cover skylight 32, and the inside is provided with an internal temperature sensor 33.

[0034] This invention selects test samples #1 to #12 for testing and comparison. The test samples are as follows:

[0035] #1 Spring Yarn Lining

[0036] #2 Double-sided Plain Knit Fabric

[0037] #3 Coated Woven Fabric (Black and White)

[0038] #4 100% Polyester Hot Stamping Fabric (Black Outer, Silver Inner)

[0039] 5# Heat-reflective silver-coated cloth (silver mesh)

[0040] 6# Coated Woven Fabric (Black and White)

[0041] 7# Green and white down fabric (no heat-reflective coating)

[0042] #8 Orange + Orange Down Fabric (with Heat-Reflective Coating)

[0043] #9 Green Fabric (No Heat-Reflective Coating)

[0044] 10# Orange fabric (with heat-reflective coating)

[0045] #11 Double-layer green fabric (without heat-reflective coating)

[0046] #12 Double-layer orange fabric (with two layers of heat-reflective coating)

[0047] The samples were divided into three groups according to their thermal insulation performance:

[0048] Group 1: 1#-6# are fabrics with average thermal insulation properties.

[0049] Group 2: 7#-8# fabrics with good thermal insulation properties (down products)

[0050] Group 3: 9#-12# heat-reflective coated fabrics.

[0051] 1. Sample preparation: According to GB / T 35762-2017 "Test Method for Heat Transfer Properties of Textiles - Flat Plate Method", test samples #1 to #12 are pre-cut into squares with a side length of not less than 30cm to ensure that the test samples can completely cover the frame. They are then placed in the constant temperature and humidity room for full equilibration for 24 hours.

[0052] 2. Test environment: Textile constant temperature and humidity laboratory, temperature set at 20℃, relative humidity set at 65%, observed by a multi-channel portable temperature and humidity monitoring recorder. During the test, the temperature fluctuation in the test area was within ±0.3℃, and the relative humidity fluctuation was within ±3%.

[0053] 3. Empty plate test: Set the temperature of the test plate, protection plate, and base plate to 35℃. Preheat the instrument for a certain period of time, and wait for the temperature of the test plate, protection plate, and base plate to reach the set value. When the temperature difference is stable within 0.3℃ and the ambient temperature and humidity are stable, start the test.

[0054] 4. Measurement of fabric heat reflectivity.

[0055] To make the test results more referential and meaningful, this invention also measures the test samples in accordance with GB / T35762-2017 "Test Methods for Heat Transfer Properties of Textiles - Plate Method".

[0056] 4.1 According to the test method of GB / T 35762, after the empty plate test is completed, lay the front side of test sample #1 flat on the test plate, observe the temperature balance and start the sample test. After completion, repeat the sample test once without performing other operations, and take the arithmetic mean of the two data as the result; do the same for the back side of sample #1.

[0057] The same method was used to test other samples.

[0058] Heat reflection insulation performance test:

[0059] After completing the above tests, lay the test sample flat and attach all four edges to the upper surface of the frame with masking tape; read the reading of the temperature sensor 23 on the frame, test twice in the same way and take the average value; after completion, test the reverse side of the fabric in the same way.

[0060] The same method was used to test other samples.

[0061] The test results are as follows:

[0062] Table 1. Test samples of the first group of samples.

[0063]

[0064] As shown in Table 1 above, according to GB / T 35762-2017 "Test Method for Heat Transfer Properties of Textiles - Plate Method": For samples without heat reflective coating, the placement direction of the test surfaces 1# to 3# has little effect. Measurements taken with the skin-contact side facing the hot plate (normal wearing side of the garment, front) range from 0.08 to 0.11, while measurements taken with the reverse side range from 0.09 to 0.12. For samples with heat reflective properties, the front measurement values ​​of the test surfaces 4# to 6# are 0.07 to 0.22, which are not significantly different from the samples without heat reflective function and cannot reflect the heat-concentrating performance. However, when measured with the reverse side, the corresponding Clo values ​​increase significantly; for example, for 4#, it increases from 0.07 to 0.41.

[0065] The main reason for the discrepancy is that during the front-side test, the test board is in direct contact with the heat-reflective coating, and heat is mainly conducted, with heat reflection playing a minimal role. During the reverse-side test, a fabric layer separates the test board from the heat-reflective coating, reducing heat conduction while allowing the heat reflection function to take effect. It's important to note that during front-side measurements, the entire surface of the heat-reflective coating cannot be guaranteed to be perfectly flat and adhered to the test board, weakening heat conduction and causing abnormal fluctuations in the Clo value. For example, the front-side measurement value of #5 is 0.22, which is 2-3 times different from the values ​​of #4 (0.07) and #6 (0.10). The reverse-side measurements, however, show values ​​between 0.35 and 0.50, which are relatively close.

[0066] The heat reflectance measurement method of this invention shows that, regardless of whether a sample has a heat reflective coating, the difference in Clo values ​​measured on the front and back of the same sample test surface is small. However, the Clo value of samples with heat reflective function is significantly higher than that of samples without heat reflective function. Taking the front as an example, the Clo values ​​of the non-heat reflective group (1#-3#) are between 0.70 and 0.74, while those of the heat reflective group (4#-6#) are between 0.99 and 1.44. There is a significant difference between the two groups, with an average Clo value increase of 74%. The modified device can demonstrate the heat reflection and heat concentration performance. From the perspective of the power required for the test plate to maintain a temperature equilibrium state, as the heat reflectance function of the sample increases, the insulation power consumed by the test plate decreases. When this technology is applied to real life, with a heat reflective coating, there is no need to specifically increase the thickness and material of the insulation material to achieve the same good insulation effect.

[0067] Table 2. Test samples in the second group.

[0068]

[0069] For the second group of test samples, namely samples with good thermal insulation performance, measured by the GB / T35762-2017 plate method, the Clo value of down fabric with heat-reflective coating #8 was 6.3% higher than that of down fabric without heat-reflective coating #7. The thermal reflectometer of this invention still reflects the heat-reflective function; the Clo value of #8 was 30.4% higher than that of #7. Compared with typical samples, the improvement in thermal insulation effect is relatively small, and the thermal radiation power decreased from 0.84W to 0.48W, a reduction of 0.36W in absolute terms.

[0070] Table 3 Test samples of the third group

[0071]

[0072] Compared to fabric without a heat-reflective coating, fabric #10 with a single-layer heat-reflective coating has a Clo value that is 64.1% higher and a heat radiation power that is 61.3% lower.

[0073] Compared to the two-layer fabric without heat-reflective coating, the clo value of fabric #12 with two layers of heat-reflective coating is increased by 125.3%, and the heat radiation power is reduced by 37.6%.

[0074] The test results above show that the placement direction of the test surface of the silver-coated heat reflective product has a significant impact on the test sample's direct contact with the test plate. When the silver-coated surface is placed facing the hot plate (normal wear, front view), the value is small, and the difference compared with the value of conventional products is very small, which cannot reflect the heat reflection performance. However, the test data on the reverse side are significantly different. The main reason is that when the test plate is in direct contact with the silver-coated surface during front measurement, heat transfer mainly relies on heat conduction, and heat reflection cannot play an effective role.

[0075] The fabric heat reflection testing instrument and method provided by this invention isolates the test sample and the test plate with a relatively sealed air layer with poor thermal conductivity. The placement direction of the test surface of the silver-coated heat reflection product has little impact, and the value is significantly improved compared with conventional products (average about 74%). This method can reflect the heat reflection performance. The phenomenon that the data difference is small when the test surface of this type of product is different is mainly because the silver-coated surface is not in direct contact with the test plate during measurement (in actual use, this type of product usually does not come into direct contact with the skin). Its heat reflection and heat concentration performance will play a reflective role regardless of the placement direction. However, the reflective performance is better when the silver-coated surface is placed facing the hot plate, so the Clo value will also be larger.

[0076] Adding a heat-reflective coating can improve the insulation effect, meaning that the same insulation effect can be achieved without better insulation materials.

[0077] Samples with good heat insulation, such as down feathers (the second group of test samples), have a relatively high temperature due to the accumulation of heat inside, and a small temperature difference with the test plate. Therefore, their thermal radiation value is not high, at 0.84W. After heating the reflective coating, it decreased by 0.36W. Compared with conventional samples, the improvement effect is limited.

[0078] Increasing the number of heat-reflective coating layers can effectively improve the heat insulation effect. Compared with fabrics without heat-reflective function, the heat radiation power of a single layer is reduced to 61.3%, and the heat radiation power of a double layer is reduced to 37.6%.

[0079] Using heat reflection power to characterize the heat insulation effect of heat-reflective functional fabrics is more intuitive. The lower the heat reflection power, the better the heat reflection effect of the coating and the lower the power consumption required for heat insulation.

[0080] This invention utilizes the fundamental principles of heat transfer, based on GB / T 35762-2017 "Test Methods for Heat Transfer Properties of Textiles - Plate Method," to test the heat reflectivity of fabrics. By analyzing representative test results of various fabrics, an evaluation index for the heat reflectivity and insulation effect of fabrics is established. This fills a gap in the testing of fabric heat reflectivity performance. The establishment of this testing and analysis method helps people gain a deeper understanding of heat reflective insulation fabrics, which is beneficial for functional textile fabric manufacturers to better develop their new products, thereby promoting the high-quality development of the modern textile and apparel industry.

Claims

1. A fabric heat reflection performance detection device, comprising a base and an instrument cover, the base comprising a bottom plate, a test plate, a protection plate, a wooden frame and a heat insulation layer, the bottom plate, the test plate and the protection plate being provided with temperature control devices and being capable of being heated and maintained at a constant temperature, the protection plate being annularly arranged around the test plate; the instrument cover being arranged above the base and forming a closed space with the base; one side of the instrument cover being provided with an instrument cover door, an upper side of the instrument cover being provided with an instrument cover skylight, and an inside of the instrument cover being provided with an inside cover temperature sensor; an overhead frame being arranged above the test plate, a maximum edge of an inside of the overhead frame not exceeding the test plate, an overhead frame support of the overhead frame being made of a heat insulation material, inner and outer surfaces of the overhead frame support being covered by aluminum foil paper, and a frame inside temperature sensor being arranged on the inside of the overhead frame close to an upper end. The test plate is made of an aluminum or copper metal plate. A height of the overhead frame is 30 mm, and a width of the overhead frame support is 20 mm. characterized in that A material of the overhead frame support is heat insulation foam.

2. The fabric heat reflective performance detection device according to claim 1, wherein: ​ 3. The fabric heat reflective performance detection device according to claim 1, wherein: ​ 4. The fabric heat reflective performance detection apparatus according to claim 1, wherein: ​

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