阅读说明：本技术 用于飞机气候实验室多风道循环风系统的融霜控制方法 (Defrosting control method for multi-air-duct circulating air system of airplane climate laboratory ) 是由 成竹 强宝平 吴相甫 王瑶 杜文辉 于 2021-11-19 设计创作，主要内容包括：本发明公开了一种用于飞机气候实验室多风道循环风系统的融霜控制方法,包括步骤：一、安装融霜控制装置；二、开启多风道循环风系统并进行2N个换热器进出风侧的风压压差的实时检测；三、待融霜的换热器的选择及融霜。本发明通过采用轮询式的算法能够适当地选择出某一时刻最需要进行融霜的两个换热器进行融霜作业,且两个处于融霜作业状态的换热器不同属于一个室外空气处理总管内,其余待融霜的换热器和未结霜的换热器持续进行正常工作,直至其被判定需要即刻进行融霜作业,从而减少对实验室环境温度的影响,保证实验室内试验的正常进行。(The invention discloses a defrosting control method for a multi-air-channel circulating air system of an airplane climate laboratory, which comprises the following steps of: firstly, installing a defrosting control device; secondly, starting a multi-air-channel circulating air system and detecting the air pressure difference of the air inlet side and the air outlet side of the 2N heat exchangers in real time; and thirdly, selecting a heat exchanger to be defrosted and defrosting. The invention can properly select two heat exchangers which are most needed to be defrosted at a certain moment to be defrosted for defrosting operation by adopting a polling algorithm, the two heat exchangers in the defrosting operation state belong to an outdoor air treatment main pipe, and the rest heat exchangers to be defrosted and the heat exchangers which are not frosted continuously work normally until the heat exchangers are judged to be needed to be defrosted immediately, thereby reducing the influence on the environment temperature of a laboratory and ensuring the normal operation of the laboratory test.)

1. The defrosting control method for the multi-air-channel circulating air system of the aircraft climate laboratory comprises N circulating air units, wherein N is a positive integer and takes 4-7, each circulating air unit comprises an indoor air supply pipe (1), an outdoor air treatment main pipe (11) and an indoor air return pipe (2), each outdoor air treatment main pipe (11) comprises two outdoor air treatment branch pipes (3), and each outdoor air treatment branch pipe (3) is internally provided with a centrifugal fan (4) and a heat exchanger (5), and is characterized by comprising the following steps:

step one, installing a defrosting control device:

the defrosting control device comprises 2N defrosting control units, the number of the defrosting control units is the same as that of the outdoor air treatment branch pipes (3), and the defrosting control units correspond to one another one by one and comprise a pressure difference measuring mechanism for measuring the air pressure difference of the air inlet side and the air outlet side of the heat exchanger (5) in each outdoor air treatment branch pipe (3) and a defrosting mechanism for carrying out internal defrosting on the heat exchanger (5);

step two, starting the multi-air-channel circulating air system and utilizing a pressure difference measuring mechanism to detect the air pressure difference of the air inlet side and the air outlet side of the 2N heat exchangers in real time;

step three, selecting a heat exchanger to be defrosted and defrosting:

301, obtaining the wind pressure difference of the air inlet and outlet sides of the 2N heat exchangers (5) according to the measurement data of the pressure difference measurement mechanism, determining the number of the heat exchangers (5) with the wind pressure difference of the air inlet and outlet sides larger than 700Pa in the current 2N heat exchangers (5), and recording the heat exchangers (5) with the wind pressure difference of the air inlet and outlet sides larger than 700Pa as the heat exchangers (5) to be defrosted;

step 302, when the number of the heat exchangers (5) to be defrosted is 1, performing defrosting operation on the heat exchangers (5) to be defrosted by using defrosting mechanisms corresponding to the heat exchangers;

when the number of the heat exchangers (5) to be defrosted is 2, judging whether the two heat exchangers (5) to be defrosted are positioned in the same outdoor air processing main pipe (11) or not,

when the two heat exchangers (5) to be defrosted are positioned in the same outdoor air treatment main pipe (11), defrosting operation is carried out on one heat exchanger (5) to be defrosted with the largest wind pressure difference at the air inlet side and the air outlet side of the two heat exchangers (5) to be defrosted;

when the two current heat exchangers (5) to be defrosted are positioned in two different outdoor air treatment main pipes (11), defrosting operation is simultaneously carried out on the two current heat exchangers (5) to be defrosted by using defrosting control units corresponding to the two current heat exchangers (5) to be defrosted;

when the number of the heat exchangers (5) to be defrosted is more than 2, selecting two of the heat exchangers (5) to be defrosted which are positioned in different outdoor air processing main pipes (11) and have the largest and the second largest wind pressure difference at the air inlet and outlet sides, and defrosting the heat exchangers simultaneously;

and 303, circulating the steps 301 to 302 until the multi-air-duct circulating air system stops working.

2. The method of claim 1 for controlling defrosting of an aircraft climate laboratory multi-duct circulating air system, wherein: the defrosting mechanism comprises a defrosting pipeline (6), one end of the defrosting pipeline (6) is connected with the secondary refrigerant inlet of the heat exchanger (5), and the other end of the defrosting pipeline (6) is connected with the secondary refrigerant outlet of the heat exchanger (5); the defrosting pipeline (6) is filled with secondary refrigerant, and the defrosting pipeline (6) is provided with a cooling water plate type heat exchanger (12) and a steam plate type heat exchanger (13) which are used for heating the secondary refrigerant, a temperature sensor (14) which is used for measuring the temperature of the secondary refrigerant in the defrosting pipeline (6), and a circulating pump (8) which is used for controlling the internal circulation of the secondary refrigerant in the defrosting pipeline (6) and the heat exchanger (5).

3. A method of frost control for an aircraft climate laboratory multi-duct circulating air system as claimed in claim 2, wherein: in the third step, the specific steps of utilizing the defrosting mechanism to perform defrosting operation on the heat exchanger (5) to be defrosted are as follows:

step S1, closing a secondary refrigerant filling pump (7) corresponding to the heat exchanger (5) to be defrosted, and starting a circulating pump (8) to circulate the secondary refrigerant in the defrosting pipeline (6) and the heat exchanger (5);

s2, opening a water inlet electromagnetic valve K3 on the cooling water plate type heat exchanger (12), and heating the secondary refrigerant in the defrosting pipeline (6) by using cooling water;

step S3, judging whether the wind pressure difference of the air inlet side and the air outlet side of the heat exchanger (5) is smaller than 700Pa, if so, closing a water inlet electromagnetic valve K3, closing a circulating pump (8), starting a secondary refrigerant filling pump (7), ending the defrosting operation, and if not, executing step S4;

step S4, judging whether the temperature of the coolant in the defrosting pipeline (6) is more than or equal to 10 ℃, if so, executing step S6, and if not, executing step S5;

step S5, judging whether the current defrosting operation time is more than or equal to 20min, if so, closing a water inlet electromagnetic valve K3, closing a circulating pump (8), starting a secondary refrigerant charging pump (7), ending the defrosting operation, and if not, executing step S3;

s6, closing the water inlet electromagnetic valve K3, opening a steam inlet electromagnetic valve K2 on the steam plate type heat exchanger (13), and heating the secondary refrigerant in the defrosting pipeline (6) by using steam;

step S7, judging whether the wind pressure differential pressure of the air inlet side and the air outlet side of the heat exchanger (5) is smaller than 700Pa, if so, closing an air inlet electromagnetic valve K2, closing a circulating pump (8), starting a secondary refrigerant charging pump (7), ending the defrosting operation, and if not, executing step S8;

step S8, judging whether the temperature of the secondary refrigerant in the current defrosting pipeline (6) is more than or equal to 40 ℃, if so, closing the steam inlet electromagnetic valve K2, closing the circulating pump (8) and starting the secondary refrigerant charging pump (7), ending the defrosting operation, and if not, executing the step S9;

and S9, judging whether the current defrosting operation time is more than or equal to 20min, if so, closing the steam inlet electromagnetic valve K2, closing the circulating pump (8), starting the secondary refrigerant charging pump (7), and ending the defrosting operation, and if not, executing the step S7.

4. A method of frost control for an aircraft climate laboratory multi-duct circulating air system as claimed in claim 3, wherein: the defrosting device is characterized in that the defrosting pipeline (6) is also provided with an electromagnetic valve D1, an electromagnetic valve D2, an electromagnetic valve D3, an electromagnetic valve K1 and a one-way valve Y1, the electromagnetic valve D2 is arranged on a secondary refrigerant outlet of the heat exchanger (5), the electromagnetic valve D3 is arranged on a secondary refrigerant inlet of the heat exchanger (5), the electromagnetic valve K1 and the one-way valve Y1 are both arranged at a liquid outlet end of the circulating pump (8), and the cooling water plate type heat exchanger (12) and the steam plate type heat exchanger (13) are both arranged between a liquid inlet end of the circulating pump (8) and the electromagnetic valve D1.

5. The method of claim 1 for controlling defrosting of an aircraft climate laboratory multi-duct circulating air system, wherein: the heat exchanger (5) is a medium-temperature heat exchanger or a low-temperature heat exchanger.

6. The method of claim 1 for controlling defrosting of an aircraft climate laboratory multi-duct circulating air system, wherein: the differential pressure measuring mechanism comprises a first wind pressure sensor (9) arranged on the air inlet side of the heat exchanger (5), a second wind pressure sensor (10) arranged on the air outlet side of the heat exchanger (5) and a microcontroller used for calculating the wind pressure differential pressure of the air inlet side and the air outlet side of the heat exchanger (5), and the first wind pressure sensor (9) and the second wind pressure sensor (10) are both connected with the microcontroller.

Technical Field

The invention belongs to the technical field of refrigeration of airplane climate laboratories, and particularly relates to a defrosting control method for a multi-air-channel circulating air system of an airplane climate laboratory.

Background

The climate environment test can be mainly divided into two categories, namely a natural climate environment test and a simulated climate environment test in a laboratory. The climate environment laboratory determines the adaptability of the test piece to the use environment by simulating the use environment of the test piece in the laboratory, including a basic environment and an extreme environment. The climate environment laboratory can simulate various natural environments such as low temperature, high temperature, rainfall, hail, solar irradiation and the like. The basic environment simulation system of the climate environment laboratory can provide proper temperature, humidity and pressure for the climate test, wherein the multi-air-channel circulating air system realizes temperature control of the laboratory through circulating heat exchange of air of the laboratory. And a heat exchanger for exchanging heat with air is arranged in each air channel. When special tests such as snowfall, wind blowing snow and the like are carried out, the heat exchanger is in a low-temperature working condition with a refrigerating interval of-50 ℃ to-25 ℃ or a medium-temperature working condition with a refrigerating interval of-25 ℃ to 0 ℃, frost is generated on the surface of the heat exchanger, so that the wind resistance is increased, the experimental effect is influenced, and the frost formation on the surface of the heat exchanger needs to be eliminated by the defrosting device. Because of the particularity of a climate environment laboratory, the lowest temperature can reach the redundancy of-50 ℃, and the volume of the laboratory reaches 130000m³The volume of the air duct is large, the surface area of the heat exchanger is wide, and the general defrosting device is difficult to meet the defrosting requirement of a climate environment laboratory. In addition, how to perform the defrosting operation of the heat exchanger under the requirement of influencing the indoor environmental conditions as little as possible in the test process is a problem which needs to be solved at present.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a defrosting control method for a multi-air-channel circulating air system of an airplane climate laboratory, aiming at the defects in the prior art, two different heat exchangers belonging to an outdoor air treatment main pipe are selected to be in a defrosting operation state by adopting a polling algorithm, and the other heat exchangers to be defrosted and the heat exchangers which are not frosted continuously work normally, so that the influence on the environmental temperature of the laboratory is reduced, the normal operation of the laboratory test is ensured, and the method is convenient to popularize and use.

In order to solve the technical problems, the invention adopts the technical scheme that: the defrosting control method for the multi-air-channel circulating air system of the aircraft climate laboratory is characterized by comprising the following steps of:

step one, installing a defrosting control device:

the defrosting control device comprises 2N defrosting control units, the number of the defrosting control units is the same as that of the outdoor air treatment branch pipes, and the defrosting control units correspond to the outdoor air treatment branch pipes one by one, and each defrosting control unit comprises a pressure difference measuring mechanism for measuring the air pressure difference of the air inlet side and the air outlet side of the heat exchanger in the outdoor air treatment branch pipes and a defrosting mechanism for defrosting the heat exchanger internally;

step two, starting the multi-air-channel circulating air system and utilizing a pressure difference measuring mechanism to detect the air pressure difference of the air inlet side and the air outlet side of the 2N heat exchangers in real time;

step three, selecting a heat exchanger to be defrosted and defrosting:

301, obtaining the wind pressure difference of the air inlet and outlet sides of the 2N heat exchangers according to the measurement data of the pressure difference measurement mechanism, determining the number of the heat exchangers with the wind pressure difference larger than 700Pa of the air inlet and outlet sides in the current 2N heat exchangers, and marking the heat exchangers with the wind pressure difference larger than 700Pa of the air inlet and outlet sides as the heat exchangers to be defrosted;

step 302, when the number of the heat exchangers to be defrosted is 1, performing defrosting operation on the heat exchangers to be defrosted by using defrosting mechanisms corresponding to the heat exchangers to be defrosted;

when the number of the heat exchangers to be defrosted is 2, judging whether the two heat exchangers to be defrosted are positioned in the same outdoor air processing main pipe or not,

when the two heat exchangers to be defrosted are positioned in the same outdoor air treatment main pipe, defrosting operation is carried out on one heat exchanger to be defrosted with the largest air pressure difference at the air inlet side and the air outlet side in the two heat exchangers to be defrosted;

when the two heat exchangers to be defrosted are positioned in two different outdoor air treatment main pipes, defrosting operation is simultaneously carried out on the two heat exchangers to be defrosted by using defrosting control units corresponding to the two heat exchangers to be defrosted;

when the number of the heat exchangers to be defrosted is more than 2, selecting two of the heat exchangers to be defrosted which are positioned on different outdoor air processing main pipes and have the largest and the second largest air pressure difference at the air inlet and outlet sides, and simultaneously defrosting the heat exchangers;

and 303, circulating the steps 301 to 302 until the multi-air-duct circulating air system stops working.

The defrosting control method for the multi-air-duct circulating air system of the aircraft climate laboratory is characterized by comprising the following steps of: the defrosting mechanism comprises a defrosting pipeline, one end of the defrosting pipeline is connected with the heat exchanger secondary refrigerant inlet, and the other end of the defrosting pipeline is connected with the heat exchanger secondary refrigerant outlet; the defrosting pipeline is filled with secondary refrigerant, and the defrosting pipeline is provided with a cooling water plate type heat exchanger and a steam plate type heat exchanger for heating the secondary refrigerant, a temperature sensor for measuring the temperature of the secondary refrigerant in the defrosting pipeline, and a circulating pump for controlling the circulation of the secondary refrigerant in the defrosting pipeline and the heat exchanger.

The defrosting control method for the multi-air-duct circulating air system of the aircraft climate laboratory is characterized by comprising the following steps of: in the third step, the specific steps of utilizing the defrosting mechanism to perform defrosting operation on the heat exchanger to be defrosted are as follows:

step S1, closing a secondary refrigerant filling pump corresponding to the heat exchanger to be defrosted, and starting a circulating pump to circulate the secondary refrigerant in the defrosting pipeline and the heat exchanger;

s2, opening a water inlet electromagnetic valve K3 on the cooling water plate type heat exchanger, and heating the secondary refrigerant in the defrosting pipeline by using cooling water;

step S3, judging whether the wind pressure difference of the air inlet side and the air outlet side of the current heat exchanger is smaller than 700Pa, if so, closing a water inlet electromagnetic valve K3, closing a circulating pump, starting a secondary refrigerant filling pump, ending the defrosting operation, and if not, executing step S4;

step S4, judging whether the temperature of the coolant in the current defrosting pipeline is more than or equal to 10 ℃, if so, executing step S6, and if not, executing step S5;

step S5, judging whether the current defrosting operation time is more than or equal to 20min, if so, closing a water inlet electromagnetic valve K3, closing a circulating pump, starting a secondary refrigerant charging pump, ending the defrosting operation, and if not, executing step S3;

s6, closing a water inlet electromagnetic valve K3, opening a steam inlet electromagnetic valve K2 on the steam plate type heat exchanger, and heating the secondary refrigerant in the defrosting pipeline by using steam;

step S7, judging whether the wind pressure difference of the air inlet and the air outlet of the current heat exchanger is smaller than 700Pa, if so, closing an air inlet electromagnetic valve K2, closing a circulating pump and starting a secondary refrigerant filling pump to finish the defrosting operation, and if not, executing step S8;

step S8, judging whether the temperature of the secondary refrigerant in the current defrosting pipeline is more than or equal to 40 ℃, if so, closing an air inlet electromagnetic valve K2, closing a circulating pump and starting a secondary refrigerant charging pump to finish defrosting operation, and if not, executing step S9;

and step S9, judging whether the current defrosting operation time is more than or equal to 20min, if so, closing an air inlet electromagnetic valve K2, closing a circulating pump, starting a secondary refrigerant filling pump, ending the defrosting operation, and if not, executing step S7.

The defrosting control method for the multi-air-duct circulating air system of the aircraft climate laboratory is characterized by comprising the following steps of: the defrosting pipeline is also provided with an electromagnetic valve D1, an electromagnetic valve D2, an electromagnetic valve D3, an electromagnetic valve K1 and a one-way valve Y1, the electromagnetic valve D2 is arranged on a secondary refrigerant outlet of the heat exchanger, the electromagnetic valve D3 is arranged on a secondary refrigerant inlet of the heat exchanger, the electromagnetic valve K1 and the one-way valve Y1 are both arranged at a liquid outlet end of the circulating pump, and the cooling water plate type heat exchanger and the steam plate type heat exchanger are both arranged between a liquid inlet end of the circulating pump and the electromagnetic valve D1.

The defrosting control method for the multi-air-duct circulating air system of the aircraft climate laboratory is characterized by comprising the following steps of: the heat exchanger is a medium-temperature heat exchanger or a low-temperature heat exchanger.

The defrosting control method for the multi-air-duct circulating air system of the aircraft climate laboratory is characterized by comprising the following steps of: the pressure difference measuring mechanism comprises a first wind pressure sensor arranged on the air inlet side of the heat exchanger, a second wind pressure sensor arranged on the air outlet side of the heat exchanger and a microcontroller used for calculating the wind pressure difference of the air inlet side and the air outlet side of the heat exchanger, and the first wind pressure sensor and the second wind pressure sensor are both connected with the microcontroller.

Compared with the prior art, the invention has the following advantages: the polling algorithm adopted by the invention can properly select two heat exchangers which are most required to be defrosted at a certain moment to be defrosted for defrosting operation, and the other heat exchangers to be defrosted and the heat exchangers which are not frosted only continuously work normally until the heat exchangers are judged to be required to be defrosted immediately, so that the influence on the environment temperature of a laboratory is reduced, and the normal operation of a laboratory test is ensured; in addition, the polling algorithm ensures that two heat exchangers in the defrosting operation state are different from each other and belong to one outdoor air treatment main pipe, so that the refrigerated air flow is always sent out from indoor air supply pipes in the N circulating air units, and the influence on the test result is reduced.

The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.

Drawings

Fig. 1 is a schematic structural view of a multi-duct circulating air system according to the present invention.

FIG. 2 is a schematic diagram showing the positional relationship among the outdoor air processing branch pipe, the centrifugal fan, the heat exchanger and the differential pressure measuring mechanism according to the present invention.

FIG. 3 is a schematic view showing the installation relationship between the defrosting mechanism and the heat exchanger according to the present invention.

FIG. 4 is a flow chart of the method of the present invention.

FIG. 5 is a flow chart of the defrosting operation of the present invention.

Description of reference numerals:

1-indoor blast pipe; 2-indoor return air duct; 3, outdoor air treatment branch pipe;

4-centrifugal fan; 5, a heat exchanger; 6, defrosting the pipeline;

7-coolant charge pump; 8-a circulating pump; 9-a first wind pressure sensor;

10-a second wind pressure sensor; 11-an outdoor air treatment main pipe, 12-a cooling water plate type heat exchanger;

13-steam plate heat exchanger; 14-temperature sensor.

Detailed Description

As shown in fig. 1 to 5, the defrosting control method for the multi-duct circulating air system of the aircraft climate laboratory of the present invention includes N circulating air units, where N is a positive integer and N is 4 to 7, each circulating air unit includes an indoor air supply pipe 1, an outdoor air processing main pipe and an indoor air return pipe 2, each outdoor air processing main pipe 11 includes two outdoor air processing branch pipes 3, and each outdoor air processing branch pipe 3 is provided with a centrifugal fan 4 and a heat exchanger 5, and the method includes the following steps:

step one, installing a defrosting control device:

the defrosting control device comprises 2N defrosting control units, the number of the defrosting control units is the same as that of the outdoor air treatment branch pipes 3, and the defrosting control units correspond to one another one by one and comprise a pressure difference measuring mechanism for measuring the air pressure difference of the air inlet side and the air outlet side of the heat exchanger 5 in the outdoor air treatment branch pipes 3 and a defrosting mechanism for defrosting the heat exchanger 5 internally;

step two, starting the multi-air-channel circulating air system and utilizing a pressure difference measuring mechanism to detect the air pressure difference of the air inlet side and the air outlet side of the 2N heat exchangers in real time;

step three, selecting a heat exchanger to be defrosted and defrosting:

301, obtaining the wind pressure difference of the air inlet and outlet sides of the 2N heat exchangers 5 according to the measurement data of the pressure difference measurement mechanism, determining the number of the heat exchangers 5 with the wind pressure difference of the air inlet and outlet sides larger than 700Pa in the current 2N heat exchangers 5, and recording the heat exchangers 5 with the wind pressure difference of the air inlet and outlet sides larger than 700Pa as the heat exchangers 5 to be defrosted;

step 302, when the number of the heat exchangers 5 to be defrosted is 1, performing defrosting operation on the heat exchangers 5 to be defrosted by using defrosting mechanisms corresponding to the heat exchangers;

when the number of the heat exchangers 5 to be defrosted is 2, judging whether the two heat exchangers 5 to be defrosted are positioned in the same outdoor air processing main pipe 11 or not,

when the two heat exchangers 5 to be defrosted are positioned in the same outdoor air treatment main pipe 11, defrosting operation is carried out on one heat exchanger 5 to be defrosted with the largest air pressure difference at the air inlet side and the air outlet side of the two heat exchangers 5 to be defrosted;

when the two heat exchangers 5 to be defrosted are positioned in two different outdoor air treatment main pipes 11, defrosting operation is simultaneously carried out on the two heat exchangers 5 to be defrosted by using defrosting control units corresponding to the two heat exchangers 5 to be defrosted;

when the number of the heat exchangers 5 to be defrosted is more than 2, selecting two of the heat exchangers 5 to be defrosted, which are positioned on different outdoor air processing main pipes 11 and have the largest and the second largest air pressure difference on the air inlet and outlet sides, and defrosting the heat exchangers simultaneously;

and 303, circulating the steps 301 to 302 until the multi-air-duct circulating air system stops working.

At most two heat exchangers 5 are in the defrosting operation state at the same time.

It should be noted that the polling algorithm adopted in the third step can appropriately select two heat exchangers 5 that need to be defrosted most at a certain time to perform the defrosting operation, and the remaining heat exchangers 5 to be defrosted and the heat exchangers 5 that do not frost only continuously perform the normal operation until the defrosting operation is determined to be needed immediately, so as to reduce the influence on the environmental temperature of the laboratory and ensure the normal operation of the laboratory test.

It should be noted that, through the polling algorithm in step three, the two heat exchangers in the defrosting operation state are different from each other in one outdoor air handling main pipe 11, so that it is ensured that the cooled air flows always flow out of the indoor air supply pipes 1 in the N circulating air units, and the influence on the test result is reduced.

In this example, N is 5.

In this embodiment, "when the number of the heat exchangers 5 to be defrosted is greater than 2, two of the heat exchangers 5 to be defrosted, which are located in different outdoor air handling manifolds 11 and have the largest and the second largest wind pressure difference on the air inlet and outlet sides, are selected, and the specific steps of performing defrosting operation on the selected heat exchangers simultaneously" are as follows: firstly, selecting a heat exchanger 5 with the largest air pressure difference at the air inlet and outlet sides from each outdoor air processing main pipe 11, selecting N heat exchangers 5 in total, sequencing the air pressure differences at the air inlet and outlet sides of the N heat exchangers 5 from large to small, and simultaneously carrying out defrosting operation on the heat exchanger 5 with the largest air pressure difference at the air inlet and outlet sides and the heat exchanger 5 with the second largest air pressure difference at the air inlet and outlet sides; the steps can ensure that the two heat exchangers 5 which simultaneously carry out defrosting operation are not arranged in the same outdoor air treatment main pipe 11; and because there are at least three heat exchangers 5 to be defrosted, the two selected heat exchangers 5 are determined as the heat exchangers 5 to be defrosted, the steps are clear, and the operation is convenient.

In this embodiment, as shown in fig. 3, the defrosting mechanism includes a defrosting pipeline 6, one end of the defrosting pipeline 6 is connected to the coolant inlet of the heat exchanger 5, and the other end of the defrosting pipeline 6 is connected to the coolant outlet of the heat exchanger 5; the defrosting pipeline 6 is filled with secondary refrigerant, and the defrosting pipeline 6 is provided with a cooling water plate type heat exchanger 12 and a steam plate type heat exchanger 13 for heating the secondary refrigerant, a temperature sensor 14 for measuring the temperature of the secondary refrigerant in the defrosting pipeline 6, and a circulating pump 8 for controlling the circulation of the secondary refrigerant in the defrosting pipeline 6 and the heat exchanger 5.

It should be noted that the coolant in the defrost line 6 is of the same type as the coolant in the heat exchanger 5.

It should be noted that, the secondary refrigerant in the defrosting pipeline 6 is heated by the two types of heat exchangers, namely the cooling water plate type heat exchanger 12 and the steam plate type heat exchanger 13, and the heated secondary refrigerant is sent to the heat exchanger 5 to be defrosted through the circulating pump 8, so that two levels of defrosting procedures are formed, the cooling water plate type heat exchanger 12 is used for preliminarily heating the secondary refrigerant through cooling water, the demand of steam in the defrosting early stage can be reduced, idle cooling water resources can be utilized, the defrosting efficiency is improved, the defrosting energy consumption is reduced, and the defrosting device is economical and practical.

In this embodiment, the temperature sensor 14 is disposed beside the electromagnetic valve D3 and is used to detect the temperature of the coolant entering the heat exchanger 13, so as to embody the heating effects of the cooling water plate heat exchanger 12 and the steam plate heat exchanger 13.

In this embodiment, as shown in fig. 5, in the third step, the specific steps of performing the defrosting operation on the heat exchanger 5 to be defrosted by using the defrosting mechanism are as follows:

step S1, closing the secondary refrigerant filling pump 7 corresponding to the heat exchanger 5 to be defrosted, and starting the circulating pump 8 to circulate the secondary refrigerant in the defrosting pipeline 6 and the heat exchanger 5;

step S2, opening a water inlet electromagnetic valve K3 on the cooling water plate type heat exchanger 12, and heating the secondary refrigerant in the defrosting pipeline 6 by using cooling water;

step S3, judging whether the wind pressure difference of the air inlet side and the air outlet side of the heat exchanger 5 is smaller than 700Pa, if so, closing a water inlet electromagnetic valve K3, closing a circulating pump 8, starting a secondary refrigerant charging pump 7, ending the defrosting operation, and if not, executing step S4;

step S4, judging whether the temperature of the coolant in the defrosting pipeline 6 is more than or equal to 10 ℃, if so, executing step S6, and if not, executing step S5;

step S5, judging whether the current defrosting operation time is more than or equal to 20min, if so, closing a water inlet electromagnetic valve K3, closing a circulating pump 8, starting a secondary refrigerant charging pump 7, and ending the defrosting operation, and if not, executing step S3;

s6, closing the water inlet electromagnetic valve K3, opening a steam inlet electromagnetic valve K2 on the steam plate type heat exchanger 13, and heating the secondary refrigerant in the defrosting pipeline 6 by using steam;

step S7, judging whether the wind pressure difference of the air inlet and the air outlet of the heat exchanger 5 is smaller than 700Pa, if so, closing an air inlet electromagnetic valve K2, closing a circulating pump 8 and starting a secondary refrigerant charging pump 7 to finish the defrosting operation, and if not, executing step S8;

step S8, judging whether the temperature of the secondary refrigerant in the defrosting pipeline 6 is more than or equal to 40 ℃, if so, closing the steam inlet electromagnetic valve K2, closing the circulating pump 8 and starting the secondary refrigerant charging pump 7, ending the defrosting operation, and if not, executing the step S9;

and step S9, judging whether the current defrosting operation time is more than or equal to 20min, if so, closing the steam inlet electromagnetic valve K2, closing the circulating pump 8, starting the secondary refrigerant charging pump 7, and ending the defrosting operation, and if not, executing step S7.

It should be noted that, during the defrosting operation, the centrifugal fan 4 in the defrosting pipeline stops working, but because the indoor air supply pipe 1 and the indoor air return pipe 2 exist, the air flow still exists in the outdoor air processing branch pipe 3, so the pressure difference measuring mechanism can still measure the air pressure difference at the air inlet side and the air outlet side of the heat exchanger 5, and is convenient for judging when the defrosting operation is finished.

It should be noted that the cooling water circulating in the cooling water plate heat exchanger 12 is 20 ℃ in the normal temperature environment outside the laboratory, so that the cooling water can be used to heat the zero secondary refrigerant to 10 ℃ first, and then the high-temperature steam is used to continue heating the secondary refrigerant.

It should be noted that the judgment sign for ending the defrosting operation includes whether the air pressure differential pressure at the air inlet side and the air outlet side of the heat exchanger 5 is less than 700Pa, whether the defrosting operation time is greater than or equal to 20min, or whether the temperature of the coolant in the defrosting pipeline 6 reaches the target temperature, and the three judgment signs take effect at the same time, so as to prevent the differential pressure measuring mechanism from failing, avoid resource waste to generate more energy consumption, and ensure the normal operation of the defrosting operation.

It should be noted that steps S1 to S9 are a complete flow of the defrosting operation, but in the selection of the heat exchanger 5 to be defrosted in the actual step three, the defrosting operation of one heat exchanger 5 may be interrupted at any time, and the defrosting operation is performed by switching to another heat exchanger 5 having a larger wind pressure difference on the air inlet side and the air outlet side, and the logic of replacing the heat exchanger 5 refers to step three.

In this embodiment, the defrosting pipeline 6 is further provided with an electromagnetic valve D1, an electromagnetic valve D2, an electromagnetic valve D3, an electromagnetic valve K1 and a check valve Y1, the electromagnetic valve D2 is arranged at the coolant outlet of the heat exchanger 5, the electromagnetic valve D3 is arranged at the coolant inlet of the heat exchanger 5, the electromagnetic valve K1 and the check valve Y1 are both arranged at the coolant outlet end of the circulating pump 8, and the cooling water plate heat exchanger 12 and the steam plate heat exchanger 13 are both arranged between the coolant inlet end of the circulating pump 8 and the electromagnetic valve D1.

It should be noted that, when the defrosting operation is started, the electromagnetic valve D1, the electromagnetic valve D2, the electromagnetic valve D3 and the electric valve K1 are all kept in an open state, and the check valve Y1 is used for preventing the coolant heated by the cooling water plate heat exchanger 12 and the steam plate heat exchanger 13 from flowing back, so that the coolant heating effect is ensured, and the defrosting efficiency is improved.

In this embodiment, the heat exchanger 5 is a medium temperature heat exchanger or a low temperature heat exchanger.

It should be noted that the medium temperature heat exchanger is used under the medium temperature working condition with the refrigeration interval of-25 ℃ to 0 ℃, and the low temperature heat exchanger is used under the low temperature working condition with the refrigeration interval of-50 ℃ to-25 ℃.

In this embodiment, the differential pressure measuring mechanism includes a first wind pressure sensor 9 disposed on the air inlet side of the heat exchanger 5, a second wind pressure sensor 10 disposed on the air outlet side of the heat exchanger 5, and a microcontroller for calculating the wind pressure differential between the air inlet side and the air outlet side of the heat exchanger 5, and the first wind pressure sensor 9 and the second wind pressure sensor 10 are both connected to the microcontroller.

It should be noted that, the first wind pressure sensor 9 and the second wind pressure sensor 10 are both used for measuring the wind pressure in the outdoor air processing branch pipe 3, if the wind channel on the heat exchanger 5 is frosted, the sectional area of the wind channel will be reduced, and the wind pressure differential pressure on the air inlet side and the air outlet side of the heat exchanger 5 will be increased, so as to determine whether the current heat exchanger 5 needs to be defrosted.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and all simple modifications, changes and equivalent structural changes made to the above embodiment according to the technical spirit of the present invention still fall within the protection scope of the technical solution of the present invention.