CN111550907A - Air conditioner debugging system and method for determining length of capillary tube - Google Patents

Air conditioner debugging system and method for determining length of capillary tube Download PDF

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Publication number
CN111550907A
CN111550907A CN202010265485.2A CN202010265485A CN111550907A CN 111550907 A CN111550907 A CN 111550907A CN 202010265485 A CN202010265485 A CN 202010265485A CN 111550907 A CN111550907 A CN 111550907A
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length
energy efficiency
capillary
capillary tube
electronic expansion
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兰加芬
黄松斌
应必业
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Aux Air Conditioning Co Ltd
Ningbo Aux Electric Co Ltd
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Aux Air Conditioning Co Ltd
Ningbo Aux Electric Co Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F11/00—Control or safety arrangements
    • F24F11/30—Control or safety arrangements for purposes related to the operation of the system, e.g. for safety or monitoring
    • F24F11/49—Control or safety arrangements for purposes related to the operation of the system, e.g. for safety or monitoring ensuring correct operation, e.g. by trial operation or configuration checks
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F11/00—Control or safety arrangements
    • F24F11/62—Control or safety arrangements characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
    • F24F11/63—Electronic processing
    • F24F11/64—Electronic processing using pre-stored data
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F11/00—Control or safety arrangements
    • F24F11/70—Control systems characterised by their outputs; Constructional details thereof
    • F24F11/80—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air
    • F24F11/83—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air by controlling the supply of heat-exchange fluids to heat-exchangers
    • F24F11/84—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air by controlling the supply of heat-exchange fluids to heat-exchangers using valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F11/00—Control or safety arrangements
    • F24F11/70—Control systems characterised by their outputs; Constructional details thereof
    • F24F11/80—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air
    • F24F11/86—Control systems characterised by their outputs; Constructional details thereof for controlling the temperature of the supplied air by controlling compressors within refrigeration or heat pump circuits
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F11/00—Control or safety arrangements
    • F24F11/88—Electrical aspects, e.g. circuits
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F13/00—Details common to, or for air-conditioning, air-humidification, ventilation or use of air currents for screening
    • F24F13/30—Arrangement or mounting of heat-exchangers

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  • Combustion & Propulsion (AREA)
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Abstract

The invention discloses an air conditioner debugging system and a method for determining the length of a capillary tube. According to the air conditioner debugging system and the method for determining the length of the capillary tube, the theoretical capillary tube length is calculated according to all parameters of the air conditioner debugging system when the air conditioner debugging system is in the best energy efficiency, the best capillary tube length can be obtained only by testing two groups of capillary tubes after the theoretical capillary tube length is obtained, repeated air pumping and injecting operations on a pipeline system are not needed, the capillary tube length does not need to be frequently and manually replaced, the optimal capillary tube length is determined quickly, effectively and accurately, the process is simple, the time consumption is short, and the manpower, material resources and the time are saved.

Description

Air conditioner debugging system and method for determining length of capillary tube
Technical Field
The invention relates to the technical field of air conditioners, in particular to an air conditioner debugging system and a method for determining the length of a capillary tube.
Background
The capillary tube is used as an important component of the air conditioner and has a good throttling and pressure reducing effect. When the air conditioner is in operation, high-pressure and high-temperature refrigerants output from the high-pressure end of the compressor flow through the capillary tube and are changed into low-pressure and high-temperature gases. The capillary tube is used as a throttling device and has the characteristics of simple structure, low cost, high reliability and the like. And thus is widely used in air conditioning systems. However, in the debugging of the air conditioner in the early stage, it is necessary to repeatedly replace the capillary tube and perform a lot of experiments to determine the optimum length, which consumes a lot of manpower, material resources, and time, but it is not always possible to find the optimum length. And once the capillary tube is welded into the pipeline, the diameter and the length of the capillary tube cannot be changed, so that the debugging of the air conditioner performance is difficult.
Disclosure of Invention
The invention aims to provide an air conditioner debugging system and a method for determining the length of a capillary tube, and aims to solve the technical problems of complex process and long time consumption when a target capillary tube is determined in the prior art.
In order to achieve the purpose, the invention adopts the following technical scheme,
the air conditioner debugging system is used for determining the length of a capillary tube and comprises a compressor, a four-way valve, a condenser and an evaporator which are sequentially connected, wherein an electronic expansion valve is arranged between the condenser and the evaporator, a first pressure sensor and a first temperature sensor are installed at an inlet of the electronic expansion valve, and a second pressure sensor and a second temperature sensor are installed at an outlet of the electronic expansion valve.
The air conditioner debugging system of the invention enables the air conditioner debugging system to be in a set state by adjusting the electronic expansion valve, and determines the optimal capillary tube length by acquiring the pressure and the temperature of the inlet and the outlet of the electronic expansion valve and the related parameters of the electronic expansion valve, thereby simplifying the configuration required for determining the optimal capillary tube length and saving material resources.
The invention also provides a method for determining the length of the capillary tube, and the air conditioner debugging system comprises the following steps:
s1, starting an air conditioner debugging system, setting parameters according to experience values, adjusting the frequency of a compressor, and adjusting the capacity to be within a target range;
s2, aiming at the optimal energy efficiency, adjusting the valve steps of the electronic expansion valve to obtain the step number of the electronic expansion valve when the energy efficiency is optimal;
s3, acquiring pressure and temperature at an inlet and an outlet of the electronic expansion valve when the energy efficiency is optimal, and calculating the flow of a refrigerant in the air conditioner debugging system;
s4, determining the theoretical length of the capillary tube according to the pressure and the temperature at the inlet and the outlet of the electronic expansion valve when the energy efficiency is optimal and the flow of a refrigerant in an air conditioner debugging system;
s5, selecting two groups of capillary lengths which are greater than or equal to the theoretical length of the capillary and smaller than the theoretical length of the capillary and are N times respectively, and performing retest tests through a capillary tool; wherein the value of N is selected according to the enterprise logo.
And S6, determining the optimal capillary length.
According to the method for determining the length of the capillary tube, the theoretical capillary tube length is calculated according to all parameters of the air conditioner debugging system when the air conditioner debugging system is in the best energy efficiency, and the optimal capillary tube length can be obtained only by testing two groups of capillary tubes after the theoretical capillary tube length is obtained. The method for determining the length of the capillary tube does not need to repeatedly evacuate the pipeline system and inject gas, does not need to frequently and manually replace the length of the capillary tube, and can quickly, effectively and accurately determine the optimal length of the capillary tube, thereby shortening the time for determining the target capillary tube, having simple process and short time consumption, and saving manpower, material resources and time.
Further, step S1 includes:
s11, starting an air conditioner, and setting initial parameters of the step number of the electronic expansion valve, the rotating speed of an internal machine and an external machine and the frequency of a compressor according to parameters of finished air conditioners of the same type or similar types;
s12, judging whether the capacity reaches the standard or not, including:
if the capability is within the target range, go to step S2;
if the capacity is not in the target range, the compressor frequency is adjusted until the capacity is reached, and the process goes to step S2.
According to the technical scheme of the embodiment, the capacity of the air conditioner debugging system can be adjusted to the target range quickly and effectively.
Further, step S2 includes:
s21, reducing the valve step of the electronic expansion valve by one step length;
s22, judging whether the current energy efficiency is smaller than the energy efficiency of the previous step or not, wherein the judging step comprises the following steps:
s221, if the current energy efficiency is smaller than that of the previous step, increasing the current valve step by 2 step lengths;
s222, judging whether the energy efficiency at the moment is less than the energy efficiency of the previous step,
if so, finishing the optimal adjustment of the valve step;
and if not, continuing to increase the valve step by one step length until the energy efficiency at the moment is less than that of the previous step, and finishing the optimal adjustment of the valve step.
Further, step S2 further includes:
s221', if the current energy efficiency is larger than or equal to the energy efficiency of the previous step, reducing the current valve step by one step length;
s222' next, judging whether the energy efficiency at this time is less than the energy efficiency of the previous step,
if so, finishing the optimal adjustment of the valve step;
if not, the valve step is continuously reduced by one step length until the energy efficiency at the moment is smaller than that of the previous step.
According to the technical scheme of the embodiment, the optimal adjustment of the valve step of the electronic expansion valve can be quickly completed, and the valve step of the electronic expansion valve when the energy efficiency of the air conditioner debugging system is optimal is obtained.
Further, in step S3, the calculation formula of the refrigerant flow rate in the air conditioning debugging system is:
Figure BDA0002441122370000031
wherein M is the flow rate of the refrigerant; cDIs the flow coefficient; a is the flow area of the electronic expansion valve corresponding to the valve step; rho is the density of the refrigerant before throttling; p1Is the pressure at the inlet of the electronic expansion valve; p2The pressure at the outlet of the electronic expansion valve.
According to the technical scheme of the embodiment, the refrigerant flow is calculated by adopting the electronic expansion valve and all parameters in the air conditioner debugging system when the air conditioner debugging system is in the best energy efficiency, and then the theoretical length of the capillary tube is calculated.
Further, in step S4, the capillary theoretical length is the sum of the length of the super-cooling segment and the length of the two-phase segment.
According to the technical scheme of the embodiment, the capillary tube is divided into the supercooling section and the two-phase section according to the structure and the working principle of the capillary tube, the lengths of all the parts are calculated respectively, the theoretical length of the capillary tube is further obtained, and the calculation accuracy can be effectively improved.
Further, the calculation formula of the length of the supercooling section is as follows:
L1＝(P1-Ps)·2D/(fρ1u1 2)
wherein L is1Is the length of the supercooling segment; p1Is the pressure at the inlet of the electronic expansion valve; pSSaturation pressure at inlet temperature; d is the inner diameter of the capillary; rho1Is the density of the refrigerant at the saturation temperature, u1The flow velocity of the refrigerant in the supercooling section.
The embodiment provides a method for calculating the length of the supercooling section of the capillary tube.
Further, the calculation formula of the two-phase segment length is as follows:
L2＝∑ΔL
wherein L is2For the two-phase length, Δ L is the corresponding infinitesimal length after each pressure step is reduced.
Further, the calculation formula of the infinitesimal length Δ L is:
ΔL＝ΔP.2D/(fmm2vm)
wherein Δ P is a pressure step; d is the inner diameter of the capillary; m is refrigerant mass flow, fmIs an average parameter of the friction coefficient of the infinitesimal section along the way, vmIs an average parameter of the specific volume of the micro-element segment.
This example provides a method of calculating the two-phase length of the capillary.
Drawings
FIG. 1 is a schematic structural diagram of an air conditioner debugging system according to the present invention;
FIG. 2 is a flow chart of a method of determining capillary length in accordance with the present invention;
FIG. 3 is a flow chart of the present invention for adjusting capacity to meet the standard;
FIG. 4 is a schematic diagram of the relationship between the energy efficiency and the valve step of an air conditioner debugging system;
fig. 5 is a flow chart of the invention for obtaining optimal energy efficiency.
Description of reference numerals:
100-compressor, 200-four-way valve, 300-condenser, 400-evaporator, 500-electronic expansion valve, 600-first pressure sensor, 700-first temperature sensor, 800-second pressure sensor, 900-second temperature sensor.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
Example one
The present embodiment discloses an air conditioner commissioning system for determining the length of a capillary tube, as shown in fig. 1, the air conditioner commissioning system includes a compressor 100, a four-way valve 200, a condenser 300 and an evaporator 400 connected in sequence, an electronic expansion valve 500 is disposed between the condenser 300 and the evaporator 400, a first pressure sensor 600 and a first temperature sensor 700 are installed at an inlet of the electronic expansion valve 500, and a second pressure sensor 800 and a second temperature sensor 900 are installed at an outlet of the electronic expansion valve 500.
Preferably, the air conditioner debugging system includes a controller, and the controller is connected to the compressor 100, the electronic expansion valve 500, the first pressure sensor 600, the first temperature sensor 700, the second pressure sensor 800, and the second temperature sensor 900, respectively. Further preferably, the air conditioner debugging system comprises a remote controller, the remote controller is in wireless connection with the controller, relevant instructions are input on the remote controller, the remote controller sends the instructions to the controller, and the controller controls the air conditioner to execute the corresponding actions of the instructions.
According to the air conditioner debugging system, the electronic expansion valve 500 is adjusted to enable the air conditioner debugging system to be in a set state, the optimal capillary tube length is determined by obtaining the pressure and the temperature of the inlet and the outlet of the electronic expansion valve 500 and the related parameters of the electronic expansion valve 500, the configuration required for determining the optimal capillary tube length is simplified, and material resources are saved.
Example two
The embodiment discloses a method for determining the length of a capillary tube, which is implemented by the air conditioner debugging system of the first embodiment, and as shown in fig. 2, the method for determining the length of the capillary tube includes:
s1, starting an air conditioner debugging system, setting parameters according to experience values, adjusting the frequency of a compressor, and adjusting the capacity to be within a target range;
s2, aiming at the optimal energy efficiency, adjusting the valve steps of the electronic expansion valve to obtain the step number of the electronic expansion valve when the energy efficiency is optimal;
s3, acquiring the pressure and the temperature at the inlet and the outlet of the electronic expansion valve 500 when the energy efficiency is optimal, and calculating the flow of a refrigerant in the air conditioner debugging system;
s4, determining the theoretical length of the capillary tube according to the pressure and the temperature at the inlet and the outlet of the electronic expansion valve 500 and the flow of a refrigerant in an air conditioner debugging system when the energy efficiency is optimal;
s5, selecting two groups of capillary lengths which are greater than or equal to the theoretical length of the capillary and smaller than the theoretical length of the capillary and are N times respectively, and performing retest tests through a capillary tool; wherein the value of N is selected according to the enterprise logo.
And S6, determining the optimal capillary length.
According to the method for determining the length of the capillary tube, the theoretical capillary tube length is calculated according to all parameters of the air conditioner debugging system when the air conditioner debugging system is in the best energy efficiency, and the optimal capillary tube length can be obtained only by testing two groups of capillary tubes after the theoretical capillary tube length is obtained. The method for determining the length of the capillary tube does not need to repeatedly evacuate the pipeline system and inject gas, does not need to frequently and manually replace the length of the capillary tube, and can quickly, effectively and accurately determine the optimal length of the capillary tube, thereby shortening the time for determining the target capillary tube, having simple process and short time consumption, and saving manpower, material resources and time.
In this embodiment, as shown in fig. 3, step S1 specifically includes:
s11, starting an air conditioner, and setting initial parameters of the step number of the electronic expansion valve, the rotating speed of an internal machine and an external machine and the frequency of a compressor according to parameters of finished air conditioners of the same type or similar types;
s12, judging whether the capacity reaches the standard or not, including:
if the capability is within the target range, go to step S2;
if the capacity is not in the target range, the compressor frequency is adjusted until the capacity is reached, and the process goes to step S2.
The capacity is a general term of the refrigerating capacity and the heating capacity. And if the capacity is within the target range, the capacity is considered to reach the standard. The target range is typically + -5% of the required capacity, and may also be specified by the tester based on air conditioner operating requirements.
In step S12, if the capacity is not within the target range, the compressor frequency is adjusted, specifically: if the capacity is greater than the target range, reducing the compressor frequency; if the capacity is less than the target range, the compressor frequency is increased. Under the condition that the steps of the electronic expansion valve and the rotating speeds of the internal machine and the external machine are fixed, the capacity can be quickly adjusted to be within a target range by adjusting the frequency of the compressor.
Preferably, the adjustment of the frequency of the compressor can be set by a remote controller, and the remote controller can be controlled by software to send instructions to the controller for execution.
In this embodiment, as shown in fig. 5, step S2 specifically includes:
s21, reducing the valve step Steps of the electronic expansion valve 500 by a step length delta Steps;
s22, judging the EER of the current energy efficiencyAt presentWhether or not it is smaller than the previous oneEnergy efficiency EER of stepLast stepThe method comprises the following steps:
s221. if the current energy efficiency EER isAt presentEnergy efficiency EER less than the previous stepLast stepIncreasing the current valve step Steps by 2 step lengths delta Steps;
s222, then judging the energy efficiency EER at the momentAt presentWhether it is less than the previous energy efficiency EERLast step，
If so, finishing the optimal adjustment of the valve Steps;
if not, continuing to increase the valve step Steps by a step length delta Steps until the energy efficiency EER is reachedAt presentEnergy efficiency EER less than previous stepLast stepAnd finishing the optimal adjustment of the valve step.
Step S2 further includes:
s221' if the current energy efficiency EERAt presentEnergy efficiency EER greater than or equal to the previous stepLast stepIf so, reducing the current valve step Steps by a step length delta Steps;
s222' then judging the energy efficiency EER at the momentAt presentWhether it is less than the previous energy efficiency EERLast step，
If so, finishing the optimal adjustment of the valve Steps;
if not, continuously reducing the valve step Steps by one step delta Steps until the energy efficiency EER at the momentAt presentEnergy efficiency EER less than previous stepLast step。
Preferably, in the step 2, the step size Δ Steps is selected to be 4.
FIG. 4 is a schematic diagram of the relationship between the energy efficiency EER and the valve step Steps for an air conditioning commissioning system, wherein the energy efficiency EER and the valve step Steps are parabolic, the valve step Steps is reduced by △ Steps, and if EER is reduced, the valve step Steps is reduced by △ Steps2<EER1Increasing the current valve step Steps by 2 step Steps delta Steps to obtain EER2’If EER is2’<EER2If not, the valve step is increased to △ Steps until EERAt present<EERLast step。
Preferably, in this embodiment, the step number of the electronic expansion valve can be set by a remote controller, or the remote controller can be controlled by software to send a command to the controller for execution. In a preferred embodiment, software can be programmed and debugged according to the logic of step 2, so as to automatically complete the valve step adjustment of the electronic expansion valve, and obtain the step number of the electronic expansion valve 500 when the energy efficiency is optimal.
By adopting the adjusting method in the step 2, the optimal adjustment of the valve steps of the electronic expansion valve can be quickly completed, and the valve step of the electronic expansion valve 500 when the energy efficiency of the air conditioner debugging system is optimal is obtained.
In this embodiment, in step S3, the calculation formula of the refrigerant flow rate in the air conditioning debugging system is:
Figure BDA0002441122370000081
wherein M is the flow rate of the refrigerant; cDIs the flow coefficient; a is the flow area of the electronic expansion valve 500 corresponding to the valve step; rho is the density of the refrigerant before throttling; p1The pressure at the inlet of the electronic expansion valve 500; p2The pressure at the outlet of the electronic expansion valve 500.
In this embodiment, in step S4, the theoretical length of the capillary tube is the sum of the length of the supercooling segment and the length of the two-phase segment.
The calculation formula of the length of the supercooling section is as follows:
L1＝(P1-Ps)·2D/(fρ1u1 2)
wherein L is1Is the length of the supercooling segment; p1The pressure at the inlet of the electronic expansion valve 500; pSSaturation pressure at inlet temperature; d is the inner diameter of the capillary; rho1Is the density of the refrigerant at the saturation temperature, u1The flow velocity of the refrigerant in the supercooling section.
The calculation formula of the two-phase segment length is as follows:
L2＝∑ΔL
wherein L is2For the two-phase length, Δ L is the corresponding infinitesimal length after each pressure step is reduced.
The calculation formula of the infinitesimal length Δ L is:
ΔL＝ΔP·2D/(fmm2vm)
wherein Δ P is a pressure step; d is the inner diameter of the capillary; m is refrigerant mass flow, fmIs an average parameter of the friction coefficient of the infinitesimal section along the way, vmIs an average parameter of the specific volume of the micro-element segment.
According to the structure and the working principle of the capillary tube, the capillary tube is divided into a supercooling section and a two-phase section, the lengths of all the sections are calculated respectively, the theoretical length of the capillary tube is further obtained, and the calculation accuracy can be effectively improved.
In this embodiment, assuming that the flow in the capillary is a one-dimensional heat-insulating homogeneous flow model, and dividing the flow of the refrigerant in the capillary into a plurality of infinitesimals along the length of the capillary, the flow rate of the refrigerant in the capillary is as follows:
m1＝m2(1)
Figure BDA0002441122370000091
Figure BDA0002441122370000092
in the formula: m, h, v, p, f and D respectively represent the mass flow rate of the refrigerant, the enthalpy value, the specific volume, the pressure, the on-way friction coefficient and the inner diameter of the capillary. Subscripts 1, 2, m respectively represent the inlet parameter, outlet parameter, average parameter of the infinitesimal; Δ L is the length of the infinitesimal segment.
The flow of the refrigerant inside the capillary tube can be regarded as being composed of a supercooling section and a two-phase section. Saturation pressure P at inlet temperatureSThe outlet pressure of the supercooling section and the inlet pressure of the two-phase section are used, the flow of the supercooling section can be regarded as isothermal, isenthalpic, constant-speed and equal-specific-volume flow, and the length of the supercooling area of the capillary can be calculated through a formula (3):
L1＝(P1-Ps)·2D/(fm2v)
as for the refrigerant in the supercooling section,
m＝ρu
v＝L/ρ
the substitution gives the length of the supercooling segment:
L1＝(P1-Ps)·2D/(fρ1u1 2)
wherein L is1Is the length of the supercooling segment; p1The pressure at the inlet of the electronic expansion valve 500; pSSaturation pressure at inlet temperature; d is the inner diameter of the capillary; rho1Is the density of the refrigerant at the saturation temperature, u1The flow velocity of the refrigerant in the supercooling section.
After the refrigerant enters the two-phase section, the density of the refrigerant gas-liquid mixture is changed due to the low vapor density of the refrigerant, so that the speed of the refrigerant is obviously changed, and the pressure and the temperature of the refrigerant are changed accordingly.
When calculating the length of the two-phase section, the saturation pressure P at the inlet temperature is calculatedSReducing a pressure step length delta P, calculating physical property parameters of the refrigerant with reduced pressure, obtaining the length of a infinitesimal according to formulas (1) to (3), taking the reduced pressure as an initial value of the next cycle, reducing the pressure until the reduced pressure is equal to the pressure at the outlet of the electronic expansion valve 500, and accumulating the infinitesimal lengths to obtain the length of two-phase sections.
Preferably, the pressure step may be taken as (pressure at the outlet of the electronic expansion valve 500-saturation pressure at the inlet temperature)/20000.
In this embodiment, the calculation process of a length of a infinitesimal segment is as follows:
after a pressure step length Δ P is reduced, the length of the infinitesimal section is obtained according to the formula (3):
ΔL＝ΔP·2D/(fmm2vm)
wherein Δ P is a pressure step; d is the inner diameter of the capillary; m is refrigerant mass flow, fmIs an average parameter of the friction coefficient of the infinitesimal section along the way, vmIs an average parameter of the specific volume of the micro-element segment.
Obtaining average parameter v of micro-element segment specific volumemThe method comprises the following steps:
reducing a pressure step length delta P to obtain a pressure P', calculating a bubble point enthalpy value and a dew point enthalpy value corresponding to the dryness of the moment respectively being 1 and 0, assuming that the outlet enthalpy value is equal to the inlet enthalpy value, and calculating the dryness of the outlet of the infinitesimal section at the moment according to a calculation formula of the dryness;
according to the dryness of the outlet of the micro-element section, the specific volume v of the outlet of the micro-element section is obtained2V is obtained by averaging the specific volumes of the inlet and outlet of the infinitesimal sectionm。
Obtaining the average parameter f of the friction coefficient of the infinitesimal section along the waymThe method comprises the following steps:
the in-process friction coefficient can be obtained by calculation according to the diameter of the capillary, the roughness of the inner wall and the Reynolds number. Preferably, the in-path friction coefficient can be estimated by using an empirical formula, such as a Colebrook formula, a Moidi formula and a Ciffelin formula. The Reynolds number can be obtained by calculating according to the inner diameter of the capillary tube, the mass flow of the refrigerant and the dynamic viscosity of the refrigerant, wherein the inner diameter of the capillary tube and the mass flow of the refrigerant are known, and the dynamic viscosity of the refrigerant can be obtained by two known conditions of pressure, temperature or dryness of an inlet and an outlet of the micro-element section. F is obtained by averaging the in-process friction coefficient of the inlet and the outlet of the infinitesimal sectionm。
In this embodiment, the steps S5-S6 specifically include: and respectively selecting two groups of capillary lengths which are greater than or equal to the value and less than the value and are N times according to the calculated theoretical length of the capillary, and carrying out retest tests through a capillary tool so as to determine the optimal capillary length. The value of N is determined by the experimenter, and if the capillary length is specified as a multiple of 50 in the trade mark, then N is taken as 50. For example, if the calculated theoretical length of the capillary is 122.33mm and the length of the capillary is required to be a multiple of 50 according to the trade mark, the lengths of the capillary are 100mm and 150mm, respectively. And (3) taking down the electronic expansion valve 500 in the air conditioner debugging system, and welding the capillary tube tool for testing. Typically, a capillary tooling can access up to 3 capillaries of different lengths at a time. And determining the capillary length corresponding to the optimal energy efficiency through experiments, namely the optimal capillary length. Thereby, the determination of the capillary length is completed.
According to the method for determining the length of the capillary tube, the theoretical length of the matched capillary tube is obtained by solving the discrete equation, and the theoretical length of the capillary tube can be determined quickly, effectively and accurately by retesting, repeated evacuation and gas injection operations on a pipeline system of an air conditioner debugging system are not needed, and the capillary tubes with different lengths are not needed to be frequently and manually replaced, so that the time for determining the length of the capillary tube is shortened, the process is simple, the consumed time is short, and the manpower, the material resources and the time are saved.
Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (10)

1. An air conditioner debugging system for determining the length of a capillary tube, which comprises a compressor (100), a four-way valve (200), a condenser (300) and an evaporator (400) which are connected in sequence,
be provided with electronic expansion valve (500) between condenser (300) and evaporimeter (400), first pressure sensor (600) and first temperature sensor (700) are installed to the import department of electronic expansion valve (500), second pressure sensor (800) and second temperature sensor (900) are installed to the exit of electronic expansion valve (500).
2. A method of determining capillary length using the air conditioning commissioning system of claim 1, said method comprising:
s1, starting an air conditioner debugging system, setting parameters according to experience values, adjusting the frequency of a compressor, and adjusting the capacity to be within a target range;
s2, aiming at the optimal energy efficiency, adjusting the valve steps of the electronic expansion valve to obtain the step number of the electronic expansion valve when the energy efficiency is optimal;
s3, acquiring the pressure and the temperature at the inlet and the outlet of the electronic expansion valve (500) when the energy efficiency is optimal, and calculating the flow of a refrigerant in the air conditioner debugging system;
s4, determining the theoretical length of the capillary tube according to the pressure and the temperature at the inlet and the outlet of the electronic expansion valve (500) when the energy efficiency is optimal and the flow of a refrigerant in an air conditioner debugging system;
s5, selecting two groups of capillary lengths which are greater than or equal to the theoretical length of the capillary and smaller than the theoretical length of the capillary and are N times respectively, and performing retest tests through a capillary tool; wherein the value of N is selected according to the enterprise logo regulation;
and S6, determining the optimal capillary length.
3. The method of determining the length of a capillary tube according to claim 2, wherein step S1 includes:
s11, starting an air conditioner, and setting initial parameters of the step number of the electronic expansion valve, the rotating speed of an internal machine and an external machine and the frequency of a compressor according to parameters of finished air conditioners of the same type or similar types;
s12, judging whether the capacity reaches the standard or not, including:
if the capability is within the target range, go to step S2;
if the capacity is not in the target range, the compressor frequency is adjusted until the capacity is reached, and the process goes to step S2.
4. The method of determining the length of a capillary tube according to claim 2, wherein step S2 includes:
s21, reducing the valve step of the electronic expansion valve (500) by one step length;
s22, judging whether the current energy efficiency is smaller than the energy efficiency of the previous step or not, wherein the judging step comprises the following steps:
s221, if the current energy efficiency is smaller than that of the previous step, increasing the current valve step by 2 step lengths;
s222, judging whether the energy efficiency at the moment is less than the energy efficiency of the previous step,
if so, finishing the optimal adjustment of the valve step;
and if not, continuing to increase the valve step by one step length until the energy efficiency at the moment is less than that of the previous step, and finishing the optimal adjustment of the valve step.
5. The method of determining the length of a capillary tube according to claim 4, wherein step S2 further comprises:
s221', if the current energy efficiency is larger than or equal to the energy efficiency of the previous step, reducing the current valve step by one step length;
s222' next, judging whether the energy efficiency at this time is less than the energy efficiency of the previous step,
if so, finishing the optimal adjustment of the valve step;
if not, the valve step is continuously reduced by one step length until the energy efficiency at the moment is smaller than that of the previous step.
6. The method according to claim 2, wherein in step S3, the refrigerant flow rate in the air conditioning commissioning system is calculated as:
Figure FDA0002441122360000021
wherein M is the flow rate of the refrigerant; cDIs the flow coefficient; a is the flow area of the electronic expansion valve (500) corresponding to the valve step; rho is the density of the refrigerant before throttling; p1Is the pressure at the inlet of the electronic expansion valve (500); p2Is the pressure at the outlet of the electronic expansion valve (500).
7. The method for determining the length of a capillary tube according to claim 2, wherein in step S4, the theoretical length of the capillary tube is the sum of the length of the super-cooled segment and the length of the two-phase segment.
8. The method of determining capillary length of claim 7 wherein said subcooling section length is calculated by the formula:
L1＝(P1-Ps)·2D/(fρ1u1 2)
wherein L is1Is the length of the supercooling segment; p1Is the pressure at the inlet of the electronic expansion valve (500); pSSaturation pressure at inlet temperature; d is the inner diameter of the capillary; rho1Is the density of the refrigerant at the saturation temperature, u1The flow velocity of the refrigerant in the supercooling section.
9. The method of determining the length of a capillary tube according to claim 7 or 8 wherein the two-phase length is calculated by the formula:
L2＝∑ΔL
wherein L is2For the two-phase length, Δ L is the corresponding infinitesimal length after each pressure step is reduced.
10. The method of determining the length of a capillary tube according to claim 9 wherein the infinitesimal length al is calculated by the formula:
ΔL＝ΔP·2D/(fmm2vm)
wherein Δ P is a pressure step; d is the inner diameter of the capillary; m is refrigerant mass flow, fmIs an average parameter of the friction coefficient of the infinitesimal section along the way, vmIs an average parameter of the specific volume of the micro-element segment.
CN202010265485.2A 2020-04-07 2020-04-07 Air conditioner debugging system and method for determining length of capillary tube Pending CN111550907A (en)

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