A method for improving temperature control accuracy of thermal insulation box

Abstract

The present invention relates to a method for improving the temperature control accuracy of an incubator, comprising the following steps: defining the following five parameter items and storing them in a controller; parameter item A is the reference temperature corresponding to the average change rate of the temperature inside the box, which is set by the user independently; parameter item B is the maximum temperature difference between the temperature inside the box and the ambient temperature T S when the refrigeration mechanism continuously operates; parameter item T is the time constant of the incubator, which is set by the user independently; parameter item D is the weight ratio, with a range of 0 to 1, which is set by the user independently; parameter item E is the protection temperature difference, which is set by the user independently; setting the above five parameter items, the controller receives the temperature inside the box actually detected by the temperature sensor, and calculates the corrected temperature inside the box according to the set parameter items; the present invention reduces the deviation between the temperature detected by the temperature sensor and the actual temperature inside the box during the dynamic balance process, thereby improving the temperature control accuracy of the incubator.

Description

Technical Field

[0001] The invention belongs to the technical field of improving temperature control accuracy, and in particular relates to a method for improving the temperature control accuracy of an insulation box. Background Art

[0002] Currently, the thermostat control of the insulated box is usually carried out by placing a temperature sensor inside the insulated box to control the temperature inside the box. Taking a refrigerated box that controls the temperature periodically by temperature difference as an example, when the temperature of the temperature sensor is higher than the set high temperature, the controller controls the regulating mechanism to start and cool down; when the temperature sensed by the temperature sensor is lower than the set low temperature, the controller controls the regulating mechanism to stop, at which time the temperature inside the box rises, and when it rises to the high temperature set by the controller, the regulating mechanism starts again, and the temperature is controlled in this reciprocating manner.

[0003] In actual engineering, the temperature sensed by the temperature sensor is affected by many factors, and it often cannot represent the actual temperature change in the box. In general, the sensor itself is also a heat capacity unit that can store a certain amount of heat. The time constant of the sensor is also affected by different packaging methods. The time constant reflects the speed of the temperature change of the sensor itself affected by the surrounding temperature. Therefore, the reaction rate of the temperature sensor is basically affected by two aspects. One is the physical properties of the sensor itself, that is, the time constant. The time constant varies with the sensor material and packaging. The second is the influence of the surrounding environment of the sensor on the temperature sensor. In actual engineering, the sensor is affected by the layout position of the sensor, the temperature of the surrounding environment of the sensor, the wind speed, etc., which will make the temperature change rate of the sensor inconsistent with the actual temperature change rate in the box.

[0004] For an insulated box, the rate of change of its actual box temperature is affected by different ambient temperatures. At the same time, different set temperatures will also affect the rate of change of the box temperature. Here, the impact of the box temperature change rate when the box temperature remains unchanged but the ambient temperature is different is used as the analysis object. The insulated box is actually a multi-capacity object, but it can be simplified to a single-capacity object for analysis without affecting the effect of the present invention on improving the temperature control accuracy. For the simplified single-capacity object, its cooling process can be regarded as a step interference of a certain refrigeration power after equilibrium at a certain ambient temperature. The dynamic equation of its cooling process will be a first-order differential equation, which is: (Formula 1), the left side of the formula is the temperature change rate. By solving Formula 1, we can get the curve function of the temperature change following the time change. Among them, W is the refrigeration power, C is the capacity coefficient of the insulation box, K is the composite heat transfer coefficient of the insulation box, and A is the heat transfer area of ​​the insulation box. The above three parameters are the inherent characteristics of the insulation box. ΔT is the temperature difference. It can be found that the temperature change rate is only related to the size of the temperature difference. For example, for a refrigerator that is constant at 2-8°C, different ambient temperatures will lead to different ΔT. The higher the ambient temperature, the larger the ΔT, the smaller the cooling rate, and the faster the warming rate; the lower the ambient temperature, the smaller the ΔT, the larger the cooling rate, and the slower the warming rate.

[0005] By solving equation 1, we can get the curve function of the box temperature change over time, which is: (Formula 2), T is the time constant, which is the inherent physical property of the insulation box. (Formula 3), C is the capacity coefficient of the storage box, is the thermal resistance coefficient of the insulation box. It is found through formula 2 that if the cooling power does not change with the ambient temperature, the cooling curve of the insulation box will have the same trend under different ambient temperatures, and the maximum value of ΔT is (Equation 4), and the time constant T is the temperature change of 63.2%*ΔT max The time corresponding to the time.

[0006] When the rate of change of the temperature sensor is greater than the actual rate of change of the temperature in the box, for the cooling process, the regulating mechanism will shut down early, resulting in a higher box temperature; for the warming process, the regulating mechanism will start up early, resulting in a lower box temperature. When the rate of change of the temperature sensor is less than the actual rate of change of the temperature in the box, for the cooling process, the temperature regulating mechanism will delay shutting down, resulting in a lower box temperature; for the warming process, the temperature regulating mechanism will delay starting up, resulting in a higher box temperature. It can be seen that no matter whether the rate of change of the temperature sensor is large or small relative to the actual box temperature, it will cause the temperature sensor to deviate from the actual box temperature, resulting in reduced controllability of the box temperature.

[0007] A common problem encountered in the actual control process is that when the temperature of the refrigerated box meets the temperature measurement standard by adjusting the temperature sensor calibration value and temperature difference under high ambient temperature conditions, the temperature inside the refrigerated box will deviate from the temperature range inside the box at high ambient temperature after the ambient temperature is lowered, and even exceed the standard requirements. This phenomenon is particularly obvious for refrigerated boxes with small capacity coefficients. The essence is the change in ambient temperature, which not only increases the rate of change of the box temperature, but also affects the influence of the regulating mechanism on the surrounding environment of the temperature sensor, resulting in the temperature sensor changing at a rate lower than the actual rate of change of the box temperature. When the temperature drops, the regulating mechanism delays shutdown, resulting in a low box temperature. Summary of the invention

[0008] In order to solve the above problems, the present invention proposes a method for improving the temperature control accuracy of an insulated box, which has a reasonable design, overcomes the shortcomings of the prior art, and has good effects.

[0009] In order to achieve the above object, the present invention adopts the following technical solution:

[0010] A method for improving the temperature control accuracy of an insulated box, wherein a temperature sensor and a controller are arranged in the insulated box, the temperature sensor is used to detect the temperature in the box, and the controller is used to control the start or stop of a refrigeration mechanism;

[0011] The following steps are involved:

[0012] S1. Define the following five parameter items and store them in the controller;

[0013] Parameter A: defined as the reference temperature corresponding to the average rate of change of the temperature inside the box, which is set by the user;

[0014] Parameter B: defined as the temperature inside the box and the ambient temperature T when the refrigeration mechanism continues to work S The maximum temperature difference;

[0015] Parameter T: defined as the time constant of the incubator;

[0016] Parameter D: defined as a weight ratio, ranging from 0 to 1, set by the user. When D is set to 0, it means that the temperature inside the box is the temperature actually detected by the temperature sensor, without correction. When D is set to 1, it means that the temperature inside the box detected by the temperature sensor is completely corrected by the algorithm, ignoring its own changes.

[0017] Parameter E: defined as the protection temperature difference, which is set by the user. If there is an abnormal situation such as refrigeration mechanism failure or the door of the incubator is opened, the corrected temperature inside the box T X There will be distortion, so the protection temperature difference E is defined.

[0018] S2. Input the values ​​of the above five parameters. The controller receives the actual temperature inside the box detected by the temperature sensor and calculates the corrected temperature inside the box according to the values ​​of the input parameters.

[0019] S3. When the difference between the corrected temperature inside the box and the actual temperature inside the box detected by the temperature sensor is greater than E, the controller controls whether the refrigeration mechanism is activated according to the actual temperature inside the box detected by the temperature sensor. When the difference between the corrected temperature inside the box and the actual temperature inside the box detected by the temperature sensor is less than E, the controller controls whether the refrigeration mechanism is activated according to the corrected temperature inside the box.

[0020] Furthermore, although the cooling power W, the capacity coefficient C of the insulation box, the composite heat transfer coefficient K of the insulation box, and the heat transfer area S of the insulation box in formula (3) and formula (4) are the inherent physical properties of the insulation box, it is difficult to obtain accurate values ​​in practical engineering applications. By obtaining the actual cooling curve and temperature recovery curve of the insulation box under different ambient temperatures, the maximum difference ΔT between the temperature inside the box and the ambient temperature is obtained. max , and then find the average value, which is parameter B, where ΔT is the difference between the temperature inside the box and the ambient temperature. max The average value under different ambient temperatures can eliminate the influence of ambient temperature on cooling power to a certain extent.

[0021] Furthermore, by obtaining the temperature difference ΔT at different ambient temperatures, the maximum temperature difference ΔT max The time corresponding to 63.2% of the time is then averaged, which is the parameter T.

[0022] Furthermore, in S2, the corrected temperature inside the box T X =T X =(1-D)T0+D(T 0-t -V·t), where T0 is the current temperature inside the box detected by the temperature sensor, T 0-t is the temperature inside the box detected by the temperature sensor at the last moment, t is the acquisition period of the controller for the temperature sensor, and V is the actual rate of change of the temperature inside the box.

[0023] Furthermore, when the incubator is in the process of cooling down,

[0024] When the incubator is in the process of warming up,

[0025] Beneficial technical effects brought by the present invention:

[0026] The actual rate of change of the temperature inside the box is obtained to correct the rate of change of the temperature detected by the temperature sensor, so that the corrected rate of change of the temperature inside the box is consistent with the rate of change of the actual temperature inside the box, or the temperature change amount in the same time is the same, and the rate of change is used to correct the rate of change of the temperature detected by the temperature sensor with a certain weight, thereby reducing the deviation between the temperature detected by the temperature sensor and the actual temperature in the box during the dynamic balance process, thereby improving the temperature control accuracy of the insulation box. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flow chart of the control method in one embodiment of the present invention; DETAILED DESCRIPTION

[0028] In order to facilitate those skilled in the art to understand and implement the present invention, the specific implementation of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments:

[0029] For an incubator with an insulation temperature of 2 to 8°C: set the controller parameter A to 5°C, that is, the temperature change rate when the temperature in the box is 5°C represents the average change rate in the range of 2 to 8°C;

[0030] Set parameter D to 1, that is, the temperature of the temperature sensor is completely corrected by the calculated temperature inside the box, without considering the influence of its own changes;

[0031] Set parameter E to 2°C. When the difference between the corrected temperature TX and the actual temperature T0 detected by the temperature sensor is greater than 2°C, the controller controls the refrigeration mechanism based on the actual temperature detected by the temperature sensor. X When the difference between the actual temperature T0 detected by the temperature sensor and the box temperature is less than 2 degrees Celsius, the corrected box temperature is used to control the refrigeration mechanism;

[0032] For parameter item B: the incubator is kept constant at different ambient temperatures, and the controller controls the refrigeration mechanism to cool down without stopping. After the temperature is pulled to the limit, the maximum temperature difference ΔT at different ambient temperatures is obtained. max , and then take the average value, which is parameter B. Because different ambient temperatures will inevitably lead to different cooling power W, calculate ΔT at different ambient temperatures. max The average value can eliminate the influence of ambient temperature on cooling power to a certain extent;

[0033] For parameter T, the temperature difference ΔT under different ambient temperatures is calculated to reach the maximum temperature difference ΔT. max The time corresponding to 63.2% of the time, and then find the average value, which is the parameter T;

[0034] like Figure 1 As shown, after the above five parameters are set in the controller, the controller determines whether the incubator is in the cooling or warming process, and calculates the rate of change V of the temperature inside the box:

[0035] When the incubator is in the process of cooling down, If the actual temperature inside the box detected by the temperature sensor at the last moment is T 0-t , then the corrected temperature inside the box at the current moment is T X for: The controller will use T X To control whether the refrigeration mechanism is shut down;

[0036] When the incubator is in the process of warming up, If the actual temperature inside the box detected by the temperature sensor at the last moment is T 0-t , then the corrected temperature inside the box at the current moment is T X for: The controller will use T X To control whether the refrigeration mechanism is turned on;

[0037] When T X -T 0-t When it is greater than 2℃, the corrected temperature inside the box is considered distorted. The controller will control the refrigeration mechanism based on the actual temperature inside the box detected by the temperature sensor until T X -T 0-t Less than 2℃.

[0038] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for improving the temperature control accuracy of an incubator, characterized in that: The insulated box is provided with a temperature sensor and a controller, the temperature sensor is used to detect the temperature inside the box, and the controller is used to control the action of the refrigeration mechanism; The following steps are involved: S1. Define the following five parameter items and store them in the controller; Parameter A: defined as the reference temperature corresponding to the average rate of change of the temperature inside the box, which is set by the user; Parameter B: defined as the temperature inside the box and the ambient temperature T when the refrigeration mechanism continues to work S The maximum temperature difference; Parameter C: defined as the time constant of the incubator; Parameter D: defined as weight ratio, ranging from 0 to 1, set by the user; Parameter E: defined as the protection temperature difference, set by the user; S2. Input the values ​​of the above five parameters. The controller receives the actual temperature inside the box detected by the temperature sensor and calculates the corrected temperature inside the box according to the values ​​of the input parameters. S3, when the difference between the corrected temperature inside the box and the actual temperature inside the box detected by the temperature sensor is greater than E, the controller controls whether the refrigeration mechanism is activated according to the actual temperature inside the box detected by the temperature sensor; when the difference between the corrected temperature inside the box and the actual temperature inside the box detected by the temperature sensor is less than E, the controller controls whether the refrigeration mechanism is activated according to the corrected temperature inside the box; The calculation process of the parameter item B is as follows: Find the maximum difference ΔT between the temperature inside the box and the ambient temperature at different ambient temperatures max The average value is parameter item B, where ΔT is the difference between the temperature inside the box and the ambient temperature; The calculation process of the parameter item C is as follows: find the value of ΔT at different ambient temperatures. max The average value of the time corresponding to 63.2% of the time is parameter C; In S2, the corrected temperature in the box T X =T X =(1-D)T0+D(T 0-t -V·t), where T0 is the current temperature inside the box detected by the temperature sensor, T 0-t is the temperature inside the box detected by the temperature sensor at the last moment, t is the acquisition period of the controller for the temperature sensor, and V is the actual rate of change of the temperature inside the box; When the incubator is in the process of cooling down, When the incubator is in the process of warming up,

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