Testing method and system for heat transfer coefficient K value of rail vehicle body

Abstract

The present invention belongs to the field of rail vehicle testing technology, and relates to a method and system for testing the heat transfer coefficient K value of a rail vehicle body. The testing method comprises the following steps: placing the vehicle in a climate test chamber, adjusting the ambient temperature t out To the range of 5±5K; when the temperature inside and outside the vehicle is consistent, the heating devices and air supply devices evenly distributed inside the vehicle are turned on according to the given power to heat and raise the temperature; the vehicle interior temperature is continuously measured at least every 5 minutes for 20 hours to 24 hours; within 8-10 hours, any measuring point P1 is randomly selected, and the corresponding average vehicle interior temperature is t1; within 16-20 hours, any measuring point P2 is randomly selected, and the corresponding average vehicle interior temperature is t2. The vehicle body heat transfer coefficient and temperature change rate at measuring point P1 and the vehicle body heat transfer coefficient and temperature change rate at measuring point P2 are respectively calculated, and then the average heat capacity of the vehicle body is calculated, and further the actual vehicle body heat transfer coefficient is calculated. The test of the present invention is accurate, highly reliable, short in test time, and highly efficient.

Description

Technical Field

[0001] The present invention belongs to the field of rail vehicle detection technology, and relates to a rail vehicle body thermal insulation performance detection technology, and specifically to a testing method and system for testing the heat transfer coefficient K value of a rail vehicle body during a heating process. Background Art

[0002] The thermal insulation performance of a vehicle body is an important indicator for evaluating vehicle performance and is also an important basis for selecting air conditioning units. In rail vehicles, the thermal insulation performance of the vehicle body is expressed using the vehicle body heat transfer coefficient K value. In accordance with the requirements of GB / T33193 and TB / T1674, the K value is measured in a climate test chamber using the thermal stability test method for in-vehicle heating. This test method requires that the air in the vehicle be heated using an electric heater at a certain ambient temperature. After reaching a thermally stable state, the vehicle body heat transfer coefficient K value is calculated according to the following formula:

[0003]

[0004] Where P is the heating power in the car, unit: W; F is the area of ​​the car body insulation wall, unit: m 2 ; Δt is the average air temperature difference between the inside and outside of the vehicle, unit: ℃.

[0005] The thermal stability test method has strict requirements for establishing a thermally stable state when testing the K value of a vehicle body. GB / T33193 requires that, while the heating power remains stable, the difference between the average air temperature outside the vehicle and the average air temperature inside and outside the vehicle must be less than 0.5K within three hours, and the temperature difference between different temperature measurement points (inside or outside) must be less than 3K. TB / T1674 requires a thermal stabilization period of at least eight hours, within which the average air temperature inside and outside the vehicle must not fluctuate by more than ±0.5K, and the temperature fluctuation must not increase or decrease monotonically. The heating power inside the vehicle must not fluctuate by more than 3%, and the power fluctuation must not increase or decrease monotonically.

[0006] Generally speaking, when using the thermal stability method to test the heat transfer coefficient K value of the vehicle body, it is necessary to wait for the temperature inside and outside the vehicle to rise to a stable state of thermal equilibrium, and adjust the temperature uniformity inside and outside the vehicle to meet the requirements of the standard. The test time usually takes 48-72 hours, which is long and the test efficiency is low. Summary of the Invention

[0007] In response to the above-mentioned problems of long testing time and low testing efficiency in the prior art, the present invention provides a testing method and system for testing the heat transfer coefficient K value of a rail vehicle body during a heating process. This method does not require waiting for the internal and external temperatures of the vehicle to reach a stable state of thermal equilibrium. While ensuring the accuracy and reliability of the test, it reduces the test time and improves the test efficiency.

[0008] In order to achieve the above object, the present invention provides a method for testing the heat transfer coefficient K value of a railway vehicle body, the specific steps of which are as follows:

[0009] Ambient temperature adjustment steps: Place the vehicle in a climate test chamber and adjust the ambient temperature t out To the range of 5±5K;

[0010] Heating step: When the temperature inside and outside the vehicle is the same, the heating devices and air supply devices evenly distributed inside the vehicle are turned on according to the given power to heat and increase the temperature;

[0011] Temperature measurement steps: Continuously measure the temperature inside the vehicle at least every 5 minutes for 20 hours to 24 hours;

[0012] K value calculation steps: randomly select measuring point P1 within 8-10 hours, the corresponding average temperature inside the car is t1, randomly select measuring point P2 within 16-20 hours, the corresponding average temperature inside the car is t2, and calculate the heat transfer coefficient K of the car body at measuring point P1 respectively. S1 and temperature change rate The heat transfer coefficient K of the vehicle body at measuring point P2 S2 and temperature change rate By formula Calculate K S1 , the temperature change rate of measuring point P1 Take the rate of change of the average temperature inside the car per unit time near the measuring point P1, and use the formula Calculate K S2 , the temperature change rate of measuring point P2 Take the rate of change of the average temperature inside the vehicle per unit time near the measuring point P2, P is the given heating power, F is the surface area of ​​the vehicle body; then calculate the average heat capacity W of the vehicle body by the following formula r :

[0013]

[0014] The average heat capacity of the vehicle body W r Substitute the following formula to calculate the actual vehicle body heat transfer coefficient K value:

[0015]

[0016] Furthermore, in the heating step, before heating, the following steps are also included: closing or sealing the air conditioning fresh air vents and exhaust vents without heat insulation, closing the doors and windows, closing or using a K value of less than 0.5W / m 2 ·K's material blocks the through passage door.

[0017] Preferably, in the heating step, the heating power P is according to the formula P=K·F·Δt, wherein the K value is the design value, F is the surface area of ​​the vehicle body, and Δt is 25K±5K.

[0018] Preferably, during the heating step, the air supply device is placed above or on the side of the heating device to ensure air flow inside the vehicle and uniform temperature rise inside the vehicle.

[0019] Preferably, in the temperature measurement step, the temperature measurement points are arranged according to the requirements of GB / T33193 or TB / T1674.

[0020] Preferably, in the temperature measurement step, when measuring the temperature inside the vehicle, the temperature outside the vehicle and the heating power are maintained unchanged, and entry into the vehicle is not allowed.

[0021] Preferably, in the K value calculation step, the average temperature inside the vehicle is defined according to the requirements of GB / T33193 or TB / T1674.

[0022] In order to achieve the above-mentioned object, the present invention further proposes a test system for the heat transfer coefficient K value of a railway vehicle body, which is used to implement the above-mentioned test method for the heat transfer coefficient K value of a railway vehicle body, comprising:

[0023] Temperature control module, used to adjust the vehicle's ambient temperature t out Adjust to within 5±5K;

[0024] Heating devices are evenly distributed inside the vehicle to heat the vehicle according to a given heating power when the temperature inside and outside the vehicle is the same;

[0025] The air supply device is placed above or on the side of the heating device to ensure air flow inside the vehicle and evenly heat the interior of the vehicle;

[0026] Temperature sensors are placed inside the vehicle in accordance with GB / T33193 or TB / T1674 to measure the interior temperature;

[0027] K value calculation module, used to calculate the heat transfer coefficient K of the vehicle body at the measuring point P1 S1 and temperature change rate The heat transfer coefficient K of the vehicle body at measuring point P2 S2 and temperature change rate Then calculate the average heat capacity W of the vehicle body r , further based on the average heat capacity W of the vehicle body r Calculate the actual vehicle body heat transfer coefficient K value; where the measuring point P1 is taken arbitrarily within 8-10 hours, the corresponding average temperature inside the vehicle is t1, and the measuring point P2 is taken arbitrarily within 16-20 hours, the corresponding average temperature inside the vehicle is t2, through the formula Calculate K S1 , the temperature change rate of measuring point P1 Take the rate of change of the average temperature inside the car per unit time near the measuring point P1, and use the formula Calculate KS2 , the temperature change rate of measuring point P2 Take the rate of change of the average temperature inside the vehicle per unit time near the measuring point P2, where P is the given heating power and F is the surface area of ​​the vehicle body; calculate the average heat capacity W of the vehicle body by the following formula r :

[0028]

[0029] The average heat capacity of the vehicle body W r Substitute the following formula to calculate the actual vehicle body heat transfer coefficient K value:

[0030]

[0031] Compared with the prior art, the advantages and positive effects of the present invention are:

[0032] (1) The method and system for testing the heat transfer coefficient K value of a rail vehicle body of the present invention do not need to wait for the internal and external temperatures of the vehicle to reach a stable stage of thermal equilibrium. The test time is 20-24 hours, which is only half the time of the thermal stabilization method, greatly shortening the test time and improving the test efficiency.

[0033] (2) The test method and system for the heat transfer coefficient K value of the rail vehicle body of the present invention have test conditions and test procedures that are basically consistent with the existing thermal stabilization method, and are suitable for use in a constant temperature warehouse or thermal test room. The measurement point arrangement and the definition of the average temperature inside the vehicle are exactly the same as those of the existing relevant standards GB / T33193 or TB / T1674. Only the calculation method of the heat transfer coefficient is different. The test procedure can use existing mature operating procedures, and the operation is convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is the average temperature change curve inside the vehicle when the K value of the vehicle is tested using the heating method;

[0035] Figure 2 It is the curve of the change of the heat transfer coefficient K value of the vehicle body. DETAILED DESCRIPTION

[0036] The present invention is described in detail below by way of exemplary embodiments, but it should be understood that elements, structures, and features of one embodiment may be beneficially combined in other embodiments without further description.

[0037] Example 1: This example provides a method for testing the heat transfer coefficient K value of a rail vehicle body, which is used to quickly test the heat transfer coefficient K value of a rail vehicle body during a heating process. The specific steps are as follows:

[0038] Ambient temperature adjustment steps: Place the vehicle in a climate test chamber and adjust the ambient temperature t outTo the range of 5±5K.

[0039] Heating steps: When the temperature inside and outside the vehicle is the same, turn on the heating devices and air supply devices evenly distributed inside the vehicle according to the given power to heat and increase the temperature.

[0040] Specifically, before heating, the following steps are also included: closing or sealing the air conditioning fresh air vents and exhaust vents without heat insulation, closing the doors and windows, closing or using a K value of less than 0.5W / m 2 K material blocks the through-passage door. This seals the entrance and exit of the vehicle to ensure uniform heating inside the vehicle, thereby improving the accuracy of subsequent temperature detection inside the vehicle.

[0041] Specifically, the heating power P is calculated according to the formula P=K·F·Δt, where K is the design value, F is the surface area of ​​the vehicle body, and Δt is 25K±5K. It should be noted that the K value can be set according to actual needs and is not limited to a fixed value.

[0042] In this embodiment, the heating device adopts a heating device currently available on the market (such as a heater, etc.).

[0043] Specifically, the air supply device is placed above or on the side of the heating device to ensure air flow inside the vehicle and evenly heat the interior of the vehicle. In this embodiment, the air supply device is a fan but is not limited to a fan, and the fan can be an existing fan on the market.

[0044] Temperature measurement steps: Measure the temperature inside the vehicle continuously at least every 5 minutes for 20 hours to 24 hours.

[0045] Specifically, the temperature measurement points are arranged according to the requirements of GB / T33193 or TB / T1674. Arrangement according to existing standards allows the use of existing mature operating procedures, which is convenient for operation.

[0046] Specifically, when measuring the temperature inside the vehicle, the outside temperature and heating power are maintained constant, and entry into the vehicle is not allowed to ensure the accuracy of the temperature measurement inside the vehicle.

[0047] In one embodiment, the vehicle interior temperature is continuously measured every 5 minutes for 22 hours. It should be noted that the time and frequency of measuring the vehicle interior temperature can be set according to actual needs, as long as it is ensured to be no less than once every 5 minutes and the measurement time is between 20 hours and 24 hours.

[0048] K value calculation steps: randomly select measuring point P1 within 8-10 hours, the corresponding average temperature inside the car is t1, randomly select measuring point P2 within 16-20 hours, the corresponding average temperature inside the car is t2, and calculate the heat transfer coefficient K of the car body at measuring point P1 respectively. S1 and temperature change rate The heat transfer coefficient K of the vehicle body at measuring point P2 S2 and temperature change rate By formula Calculate K S1 , the temperature change rate of measuring point P1 Take the rate of change of the average temperature inside the car per unit time near the measuring point P1, and use the formula Calculate K S2 , the temperature change rate of measuring point P2 Take the rate of change of the average temperature inside the vehicle per unit time near the measuring point P2, P is the given heating power, F is the surface area of ​​the vehicle body; then calculate the average heat capacity W of the vehicle body by the following formula r :

[0049]

[0050] The average heat capacity of the vehicle body W r Substitute the following formula to calculate the actual vehicle body heat transfer coefficient K value:

[0051]

[0052] Specifically, the average temperature inside the vehicle is defined in accordance with the requirements of GB / T33193 or TB / T1674.

[0053] The above-mentioned test method of the embodiment of the present invention does not need to wait for the temperature inside and outside the vehicle to reach the stable stage of thermal equilibrium. The test time is 20-24 hours, which is only half the time of the thermal stabilization method, greatly shortening the test time and improving the test efficiency.

[0054] Embodiment 2: The embodiment of the present invention provides a system for testing the heat transfer coefficient K value of a rail vehicle body, which is used to implement the method for testing the heat transfer coefficient K value of a rail vehicle body described in embodiment 1, comprising:

[0055] Temperature control module, used to adjust the vehicle's ambient temperature t out Adjust to within 5±5K;

[0056] Heating devices are evenly distributed inside the vehicle to heat the vehicle according to a given heating power when the temperature inside and outside the vehicle is the same;

[0057] The air supply device is placed above or on the side of the heating device to ensure air flow inside the vehicle and evenly heat the interior of the vehicle;

[0058] Temperature sensors are placed inside the vehicle in accordance with GB / T33193 or TB / T1674 to measure the interior temperature;

[0059] K value calculation module, used to calculate the heat transfer coefficient K of the vehicle body at the measuring point P1 S1 and temperature change rate The heat transfer coefficient K of the vehicle body at measuring point P2 S2 and temperature change rate Then calculate the average heat capacity W of the vehicle body r , further based on the average heat capacity W of the vehicle body r Calculate the actual vehicle body heat transfer coefficient K value; where the measuring point P1 is taken arbitrarily within 8-10 hours, the corresponding average temperature inside the vehicle is t1, and the measuring point P2 is taken arbitrarily within 16-20 hours, the corresponding average temperature inside the vehicle is t2, through the formula Calculate K S1 , the temperature change rate of measuring point P1 Take the rate of change of the average temperature inside the car per unit time near the measuring point P1, and use the formula Calculate K S2 , the temperature change rate of measuring point P2 Take the rate of change of the average temperature inside the vehicle per unit time near the measuring point P2, where P is the given heating power and F is the surface area of ​​the vehicle body; calculate the average heat capacity W of the vehicle body by the following formula r :

[0060]

[0061] The average heat capacity of the vehicle body W r Substitute the following formula to calculate the actual vehicle body heat transfer coefficient K value:

[0062]

[0063] In this embodiment, when the test system tests the heat transfer coefficient K value of the vehicle body, the temperature adjustment module is connected to the heating device in the test room to control the operation of the heating device and adjust the vehicle's ambient temperature t out (i.e. the temperature inside the test chamber) is adjusted to within the range of 5±5K. The temperature adjustment module uses the existing temperature regulator on the market. Ambient temperature t out Measured by a thermometer installed in the test room.

[0064] In this embodiment, the heating device is a commercially available heating device (such as a heater, etc.), and the air supply device is a fan but is not limited to a fan. The fan can be a commercially available fan.

[0065] The above-mentioned test system of this embodiment does not need to wait for the temperature inside and outside the vehicle to reach the stable stage of thermal equilibrium. The test time is 20-24 hours, which is only half the time of the thermal stabilization method, greatly shortening the test time and improving the test efficiency.

[0066] The methods and systems described in the above embodiments are implemented according to the following test principles:

[0067] (1) Heat capacity

[0068] When using the heating method to test the K value of a vehicle, due to the existence of the heat capacity of the vehicle body, during the heating stage, part of the heat input into the vehicle per unit time is transferred out through the vehicle body insulation wall, and the other part is absorbed by the vehicle body. Assuming that the average heat capacity of the vehicle body is W, the unit is: J / K.

[0069] (2) Heat transfer coefficient of vehicle body

[0070] When using the heating method to test the vehicle's K value, the heat input into the vehicle per unit time is Q s and the outside temperature t out Keep stable, then during the heating stage, only the temperature inside the car t in Assume that the K value of the vehicle body obtained from the temperature rise test is K s ,but:

[0071] Q s =K s ·F·(t in -t out ) (1)

[0072] Among them, K s The K value of the vehicle body measured during the heating stage, unit: W / m 2 ·K;t in is the outside temperature, unit: ℃; t out is the outside temperature of the vehicle, unit: ℃.

[0073] In practice, during the heating stage, due to the heat capacity of the vehicle body, part of the heat input into the vehicle per unit time is transferred out through the vehicle body insulation wall, and the other part is absorbed by the vehicle body, that is:

[0074] Q s =Q0+Q1 (2)

[0075] Wherein, Q0 is the heat transferred from the vehicle body insulation wall per unit time, unit: J / s; Q1 is the storage heat absorbed by the vehicle body per unit time, unit: J / s;

[0076] Q0 is related to the actual K value of the vehicle body and can be written as:

[0077] Q0=K·F·(t in -t out ) (3)

[0078] Where K is the actual K value of the vehicle body, unit: W / m 2 K;

[0079] Q1 is related to the heat capacity of the vehicle body. Assuming that the temperature inside the vehicle changes by dt within the time dτ, Q1 can be written as:

[0080]

[0081] Substituting formulas (1), (3), and (4) into formula (2), we obtain:

[0082]

[0083] In the steady state, dt / dτ=0, at this time, K S =K.

[0084] See also Figure 1 The average temperature change curve inside the vehicle when the vehicle K value is tested using the heating method is shown as follows: Figure 2 The corresponding curve of the change of the vehicle body heat transfer coefficient K value is shown. Take any two points P1 and P2, and the tangent value of the tangent line to the temperature curve at the two points is the temperature change rate at the two points.

[0085] According to formula (5), for point P1:

[0086]

[0087] For point P2:

[0088]

[0089] Among them, K S1 The heat transfer coefficient of the vehicle body obtained by the test at point P1, unit: W / m 2 K; is the temperature change rate at point P1, K S2 The heat transfer coefficient of the vehicle body obtained by the test at point P2, unit: W / m 2 K; is the temperature change rate at point P2;

[0090] In the above formulas (6) and (7), only the actual vehicle body heat transfer coefficient K value and the vehicle body average heat capacity W r Unknown, therefore, the average heat capacity of the vehicle body W can be calculated r for:

[0091]

[0092] The average heat capacity of the vehicle body W r Substituting into formula (6) or (7) to calculate the actual vehicle body heat transfer coefficient K value is:

[0093]

[0094] The above-mentioned method and system of the embodiment of the present invention tests the heat transfer coefficient K value of the vehicle body according to the above-mentioned testing principle. Compared with the existing thermal stability method for testing the heat transfer coefficient K value of the vehicle body, there is no need to wait for the internal and external temperatures of the vehicle to reach a stable stage of thermal equilibrium. The test time is 20-24 hours, which is only half the time of the thermal stability method, which greatly shortens the test time and improves the test efficiency.

[0095] The above embodiments are used to explain the present invention rather than to limit the present invention. Any modifications and changes made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A method for testing the heat transfer coefficient K value of a railway vehicle body, characterized in that: The specific steps are: Ambient temperature adjustment steps: Place the vehicle in a climate test chamber and adjust the ambient temperature t out To the range of 5±5K; Heating step: When the temperature inside and outside the vehicle is the same, the heating devices and air supply devices evenly distributed inside the vehicle are turned on according to the given power to heat and increase the temperature; Temperature measurement steps: Continuously measure the temperature inside the vehicle at least every 5 minutes for 20 hours to 24 hours; K value calculation steps: randomly select measuring point P1 within 8-10 hours, the corresponding average temperature inside the car is t1, randomly select measuring point P2 within 16-20 hours, the corresponding average temperature inside the car is t2, and calculate the heat transfer coefficient K of the car body at measuring point P1 respectively. S1 and temperature change rate The heat transfer coefficient K of the vehicle body at measuring point P2 S2 and temperature change rate By formula Calculate K S1 , the temperature change rate of measuring point P1 Take the rate of change of the average temperature inside the car per unit time near the measuring point P1, and use the formula Calculate K S2 , the temperature change rate of measuring point P2 Take the rate of change of the average temperature inside the vehicle per unit time near the measuring point P2, P is the given heating power, F is the surface area of ​​the vehicle body; then calculate the average heat capacity W of the vehicle body by the following formula r : The average heat capacity of the vehicle body W r Substitute the following formula to calculate the actual vehicle body heat transfer coefficient K value:

2. The method for testing the heat transfer coefficient K value of a railway vehicle body according to claim 1, characterized in that: In the heating step, before heating, the following steps are also included: closing or sealing the air conditioning fresh air vents and exhaust vents but not insulating them, closing the doors and windows, closing or using a K value of less than 0.5W / m 2 ·K's material blocks the through passage door.

3. The method for testing the heat transfer coefficient K value of a railway vehicle body according to claim 1 or 2, characterized in that: In the heating step, the heating power P is calculated according to the formula P=K·F·Δt, where K is the design value, F is the surface area of ​​the vehicle body, and Δt is 25K±5K.

4. The method for testing the heat transfer coefficient K value of a railway vehicle body according to claim 1 or 2, characterized in that: During the heating step, the air supply device is placed above or on the side of the heating device to ensure air flow inside the vehicle and evenly heat the interior of the vehicle.

5. The method for testing the heat transfer coefficient K value of a railway vehicle body according to claim 1, wherein: In the temperature measurement step, the temperature measurement points are arranged in accordance with the requirements of GB / T33193 or TB / T1674.

6. The method for testing the heat transfer coefficient K value of a railway vehicle body according to claim 1 or 5, characterized in that: In the temperature measurement step, when measuring the temperature inside the vehicle, the outside temperature and heating power are maintained unchanged, and entry into the vehicle is not allowed.

7. The method for testing the heat transfer coefficient K value of a railway vehicle body according to claim 1, wherein: In the K value calculation step, the average temperature inside the vehicle is defined in accordance with the requirements of GB / T33193 or TB / T1674.

8. A system for testing the heat transfer coefficient K value of a railway vehicle body, used to implement the method for testing the heat transfer coefficient K value of a railway vehicle body according to any one of claims 1 to 7, characterized in that: include: Temperature control module, used to adjust the vehicle's ambient temperature t out Adjust to within 5±5K; Heating devices are evenly distributed inside the vehicle to heat the vehicle according to a given heating power when the temperature inside and outside the vehicle is the same; The air supply device is placed above or on the side of the heating device to ensure air flow inside the vehicle and evenly heat the interior of the vehicle; Temperature sensor, arranged inside the vehicle in accordance with GB / T33193 or TB / T1674, to measure the interior temperature; K value calculation module, used to calculate the heat transfer coefficient K of the vehicle body at the measuring point P1 S1 and temperature change rate The heat transfer coefficient K of the vehicle body at measuring point P2 S2 and temperature change rate Then calculate the average heat capacity W of the vehicle body r , further based on the average heat capacity W of the vehicle body r Calculate the actual vehicle body heat transfer coefficient K value; where the measuring point P1 is taken arbitrarily within 8-10 hours, the corresponding average temperature inside the vehicle is t1, and the measuring point P2 is taken arbitrarily within 16-20 hours, the corresponding average temperature inside the vehicle is t2, through the formula Calculate K S1 , the temperature change rate of measuring point P1 Take the rate of change of the average temperature inside the car per unit time near the measuring point P1, and use the formula Calculate K S2 , the temperature change rate of measuring point P2 Take the rate of change of the average temperature inside the vehicle per unit time near the measuring point P2, where P is the given heating power and F is the surface area of ​​the vehicle body; calculate the average heat capacity W of the vehicle body by the following formula r : The average heat capacity of the vehicle body W r Substitute the following formula to calculate the actual vehicle body heat transfer coefficient K value:

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