TWI401402B - Refrigerant liquid level control method for flooded evaporator - Google Patents

Description

Full liquid evaporator refrigerant liquid level control method

The invention relates to a liquid level control method for a full liquid evaporator, which provides a method for measuring an actual ice water inlet and outlet water temperature difference, a refrigerant discharge temperature value, a refrigerant evaporation pressure value and a refrigerant condensation pressure value, thereby obtaining an actual It is desirable to discharge the temperature error value and an actual and desired arithmetic mean temperature difference error value, and then adjust the opening degree of the electronic expansion valve according to the error value to control the refrigerant liquid level of the evaporator, thereby effectively utilizing the heat exchange area of the evaporator. And can increase the evaporation temperature.

In recent years, the technology of refrigerating air-conditioning has become close to maturity. However, the basic concept of refrigeration or air conditioning is to use heat exchange between refrigerant and liquid to increase or decrease the temperature of the liquid, or to reduce or increase the temperature of the refrigerant, thereby achieving air conditioning or freezing. the goal of.

The more common device in the heat exchange process is a flooded refrigerant system having a compressor, a condenser, an electronic expansion valve and a flooded evaporator, and a compressor. The utility model has an inlet end and an outlet end, wherein the outlet end is connected with a condenser by a pipeline, the condenser is connected with an electronic expansion valve by a pipeline, and the electronic expansion valve is connected with a pipeline full of liquid evaporator, full liquid The evaporator is connected to the compressor by a pipeline, and a liquid level sensor is provided in the flooded evaporator.

The liquid level of the refrigerant in the flooded evaporator is in an optimum state, which just covers the uppermost row of copper tubes in the flooded evaporator to exchange heat between the refrigerant and the liquid flowing in the copper tube. Can be water, oil or brine, etc. In order to effectively control the liquid level of the refrigerant, the prior art adopts three common methods of using a liquid level sensor, detecting the pressure of the condenser and the progressive temperature.

The first type of liquid level sensor adopts a liquid level sensor with an electronic expansion valve as a method for controlling the liquid level of the refrigerant. Under the full load standard condition, the compressor is 100% running, and the liquid level is sensed. The detector system can control the refrigerant liquid level with great precision, but in the actual state, the compressor may only have partial load. Due to the liquid level and actual liquid level set by the liquid level sensor, there is a great difference between the two. In addition, the evaporation of the refrigerant will increase the overall variable, so that the refrigerant is not at the optimal liquid level, so the evaporator can not effectively perform its optimal function, and the evaporation temperature of the refrigerant and the efficiency of the compressor cannot be improved. Moreover, the liquid level sensor of the existing liquid level sensor has poor resolution and high cost.

The second method uses the method of detecting the pressure of the condenser, which converts the detected pressure into temperature, and adds a temperature difference to serve as a refrigerant discharge temperature, thereby controlling the refrigerant liquid level, but the refrigerant liquid level is high or low. The change directly affects the evaporation temperature of the refrigerant, and the relative change in the discharge temperature is very small. The amount of change plus the error value of the temperature detection makes it difficult to accurately control the refrigerant liquid level. In addition, external factors can also cause misjudgment, such as The hot gas of the condenser enters the evaporator, causing the illusion that the evaporation temperature and the discharge temperature are too high, which makes the control more difficult. Furthermore, the pressure of the detection condenser cannot be applied to the partial load or the lower condensing pressure. The optimum level of demand.

The third type adopts the progressive temperature control method, which uses the temperature difference between the ice water outlet temperature and the refrigerant evaporation temperature to achieve the purpose of the refrigerant liquid level control, but still cannot be applied to the partial load condition, the refrigerant is the most Good liquid level and demand under optimal evaporation temperature conditions.

In summary, the existing three common single target set value refrigerant liquid level control methods have higher cost, poor liquid level resolution accuracy, and can not effectively control partial load conditions for better refrigerant liquid level, so existing refrigerants There is still room for improvement in the liquid level control method.

In view of the above disadvantages, the object of the present invention is to provide a liquid level control method for a full liquid evaporator, which utilizes the set ice water inlet and outlet water temperature difference, the measured actual ice water inlet and outlet water temperature difference, and the refrigerant. The discharge temperature value, the refrigerant evaporation pressure value and the refrigerant condensation pressure value are adjusted to adjust the opening degree of the electronic expansion valve, thereby controlling the refrigerant liquid level in the evaporator, thereby effectively utilizing the heat exchange area of the evaporator and increasing the evaporation temperature. In order to enable the evaporator to operate at the optimum refrigerant evaporation temperature, the operation efficiency of the ice water machine under partial load conditions is improved, and the cost is low and the liquid level control precision is high.

In order to achieve the above object, the technical means of the present invention is to provide a liquid level control method for a full liquid evaporator, the steps of which include the following:

A. Set basic conditions: set multiple temperature difference values and multiple correction values.

B. Measuring temperature and pressure: measuring an ice water inlet water temperature value, an ice water outlet water temperature value, a refrigerant evaporation pressure value, a refrigerant condensation pressure value, and a refrigerant discharge temperature value.

C. Calculating the error value: according to the data obtained in the steps A and B, the error value is obtained.

D. Controlling the opening degree of the electronic expansion valve: according to the error value obtained in the step C, to control the opening degree of the electronic expansion valve.

In the step A as described above, the temperature difference and the correction value are an arithmetic mean temperature difference of the evaporator, a rated ice water inlet and outlet water temperature difference, an arithmetic mean temperature difference correction value, an arithmetic mean temperature difference neutral band and a spit out The temperature correction value, the arithmetic mean temperature difference correction value is between -0.5 and 0.5, and the discharge temperature correction value is between 0 and 5. And the rated arithmetic mean temperature difference, the rated ice water inlet and outlet water temperature difference, the arithmetic mean temperature difference correction value and the discharge temperature correction value are set in one controller; and the electronic expansion valve is set at the initial opening degree of a compressor starting operation The setting value can be 50~100%.

Step B, as described above, is to measure the ice water inlet water temperature value, the ice water outlet water temperature value and the refrigerant discharge temperature value by using a plurality of temperature sensors, and separately measure the evaporator or the plurality of pressure sensors respectively. The refrigerant evaporation pressure value of the suction pipe of the compressor and the refrigerant condensation pressure value of the discharge pipe of the condenser or the compressor. The temperature sensor and the pressure sensor transmit the measured ice water into the water temperature value, the ice water outlet water temperature value, the refrigerant discharge temperature value, the refrigerant evaporation pressure value, and the refrigerant condensation pressure value to the controller.

Step C as described above, further having:

C1. Calculating a desired arithmetic mean temperature difference between the compressor and the desired discharge temperature value of the compressor: obtaining a desired discharge temperature value of the compressor according to the refrigerant evaporation pressure value, the refrigerant condensation pressure value, and the discharge temperature correction value; The temperature difference between the water inlet water temperature value and the ice water outlet water temperature value, the arithmetic mean temperature difference correction value, and the rated arithmetic mean temperature difference value, and the desired arithmetic mean temperature difference value of the evaporator is obtained.

C2. Calculating the evaporation temperature value of the refrigerant: according to the evaporation pressure value of the refrigerant, a refrigerant evaporation temperature value is obtained.

C3, calculate the actual arithmetic mean temperature difference: according to the temperature of the ice water into the water The value, the ice water outlet temperature value and the refrigerant evaporation temperature value, and an actual arithmetic mean temperature difference is obtained.

C4. Calculating the error value of the refrigerant discharge temperature and the arithmetic mean temperature difference: according to the refrigerant discharge temperature value and the desired refrigerant discharge temperature value, an actual and desired discharge temperature error value is obtained; and the actual arithmetic mean temperature difference and the desired arithmetic mean temperature difference are obtained. The value gives an actual and expected arithmetic mean temperature difference error value.

In step C1, the refrigerant evaporation pressure value is abbreviated as RSEP, the refrigerant condensation pressure value is abbreviated as RSCP, the discharge temperature correction value is simply referred to as C _SHDT , and the desired discharge temperature value is simply referred to as SHDT _exp , and the calculation formula of the desired discharge temperature value is It is: SHDT _exp = {a + b × (RSCP) + c × (RSCP) ² + d × (RSEP) + C _SHDT }, and a, b, c, d are constants.

In step C1, the ice water inlet water temperature value is simply referred to as CWRT, the ice water water outlet temperature value is simply referred to as CWLT, the rated ice water inlet and outlet water temperature difference is simply referred to as ΔT, and the arithmetic mean temperature difference correction value is abbreviated as C _Δtm , rated The arithmetic mean temperature difference is abbreviated as Δt _m , and the arithmetic mean temperature difference is abbreviated as Δt _m(exp) . The calculation formula of the expected arithmetic mean temperature difference is: Δt _m(exp) =(CWRT-CWLT)/△ T × Δt _m + C _Δtm .

In step C2, the refrigerant evaporation temperature value is abbreviated as RSET, and the refrigerant evaporation temperature value is calculated as: RSET=a1+b1×(RSEP)+c1×(RSEP) ^0.5 , wherein a1, b1, and c1 are constants.

In step C3, the actual arithmetic mean temperature difference is abbreviated as Δt _m(real) , and the actual arithmetic mean temperature difference is calculated as: Δt _m(real) = [(CWRT+CWLT)/2]-RSET.

In step C4, the actual and desired discharge temperature error values are simply referred to as Err _△SHDT , and the actual and desired discharge temperature error values are calculated as: Err _△SHDT =SHDT-SHDT _exp ; actual and expected arithmetic mean temperature difference error values are simply referred to as Err _Δtm , the actual and expected arithmetic mean temperature difference error value is calculated as: Err _Δtm = Δt _{m (exp)} - Δt _{m (real)} .

Step D as described above, further having:

D1, determining whether the actual and desired discharge temperature error value is less than or equal to or greater than a set value: the set value is zero, if the actual and desired discharge temperature error value is less than or equal to the set value, turning on a liquid compression protection flag, reducing the The opening degree of the electronic expansion valve; if the actual and desired discharge temperature error value is greater than the set value, the liquid compression protection flag is turned off, and the next step is entered.

D2: determining whether the actual and expected arithmetic mean temperature difference error value is greater than or equal to the arithmetic mean temperature difference neutral band: if less than or equal to the arithmetic mean temperature difference neutral band, the electronic expansion valve maintains the existing opening degree, and returns to step B If it is greater than the arithmetic mean temperature difference neutral band, adjust the opening of the electronic expansion valve and return to step B.

As described above, there is further a step of whether or not the compressor is operated between the step B and the step C1, and if the compressor is not operating, the process ends; if the compressor is operated, the step C1 is performed.

As described above, between step C4 and step D1, there is further provided a step of whether the compressor is operated for greater than or equal to a specific time, the specific time is 3 to 5 minutes, and if the compressor is operated less than or equal to a specific time, the electronic expansion valve is If the opening degree is 50 to 100%, the process returns to step B; if the compressor operation is greater than the specific time, step D1 is performed.

In step D1 as described above, the electronic expansion valve is attached to a fixed output force week. The period is gradually reduced by 5%, and the maximum opening limit of the electronic expansion valve is equal to the current opening of the electronic expansion valve.

When the liquid compression protection flag is turned off, the maximum opening degree of the electronic expansion valve is released, and the process proceeds to step D2.

In the step D2 as described above, when the neutral band is greater than the arithmetic mean temperature difference, the controller calculates the desired opening degree and the number of action steps of the electronic expansion valve to adjust the opening degree of the electronic expansion valve.

When the number of action steps is positive, the opening degree of the electronic expansion valve is increased, and the process returns to the step B; when the number of action steps is negative, the opening degree of the electronic expansion valve is reduced, and the process returns to the step B.

The steps A and B described above further have a method for correcting the temperature difference between the rated ice water and the water, and the steps include:

First, set the rated full load of ice water into the water temperature difference: set a nominal ice water into the water temperature difference, the rated ice water into the water temperature difference is equal to the step ice in the rated ice water inlet and outlet water temperature difference.

Second, whether the compressor is running: If the compressor is not running, it will end; if the compressor is running, proceed to the next step.

3. Whether the compressor reaches the full load condition: if the compressor does not reach the full load condition, it will not be corrected, then go to step 2; if the compressor runs to the full load condition, proceed to the next step.

4. Calculate the difference between the temperature of the ice water and the water flowing out of the compressor under full load conditions: the controller determines the temperature difference between the ice water and the outlet water when the compressor is under full load condition according to the ice water inlet water temperature value and the ice water outlet water temperature value;

5. Automatically determine whether to re-adjust the rated temperature difference between the rated ice water and the inlet and outlet water: according to the difference between the rated ice water inlet and outlet water temperature difference and the ice water inlet and outlet water temperature difference, An error value is obtained. If the absolute value of the error value is less than or equal to a set value, then no action is performed, then to step 2, the set value is 5%; if the absolute value is greater than the set value, the next step is performed;

6. Determine whether the number of consecutive occurrences is equal to or less than a fixed number of times: the fixed number of times is five to ten times. If the absolute number is greater than the fixed number of times, the difference between the temperature of the ice water and the water is replaced by the rated ice water. Enter the water temperature difference and return to step 2; if the absolute value is greater than the set value, the number of occurrences is less than the fixed number of times, then no correction, and to step 2.

The shorthand temperature difference between ice water and water is △T _real , the calculation formula of ice water inlet and outlet water temperature difference is: △T _real =CWRT-CWLT; the nominal ice water inlet and outlet water temperature difference is abbreviated as △T _setpoint , the calculation formula of error value It is: ABS (△T _real - ΔT _setpoint ) / ΔT _setpoint ≧ 5%.

In combination with the above method, the main method is to adjust the opening degree of the electronic expansion valve according to the actual and desired discharge temperature error value and the actual and desired arithmetic mean temperature difference error value, thereby controlling the refrigerant flow rate, and effectively utilizing the heat exchange of the evaporator. The area can increase the evaporation temperature so that the evaporator refrigerant can be at the optimal liquid level, and the evaporator is operated at the optimum refrigerant evaporation temperature. Therefore, the invention has the advantages of low cost and accurate liquid level resolution. The advantage of controlling the refrigerant at the optimum liquid level under partial load conditions.

The embodiments of the present invention are described below by way of specific embodiments, and those skilled in the art can readily understand other advantages and functions of the present invention from the disclosure of the present disclosure.

Please refer to Figures 1, 2A and 2B, the present invention is a full liquid type The evaporator refrigerant level control method includes the following steps:

A. Setting basic condition 20: setting an evaporator 11 in a controller 10, and calculating a nominal arithmetic mean temperature difference (hereinafter referred to as Δt _m ) at a rated full load operating condition and a rated ice water inlet and outlet water temperature difference (below) Abbreviation, ΔT), in addition to the controller 10, an arithmetic mean temperature difference correction value (hereinafter referred to as C _Δtm ), an arithmetic mean temperature difference neutral band (hereinafter referred to as dead band) and a discharge temperature correction value (hereinafter referred to as _Acronym, C SHDT), wherein C _{△ tm} between -0.5 ~ _0.5, C SHDT between 0 and 5; the nominal temperature difference line out into ice-water and ice-water flow rate is changed to follow the water into the ice-water rated For the setting method of the temperature difference change, please refer to the following. Further, the setting value set by the electronic expansion valve 14 at the initial opening degree of the startup operation of the compressor 12 may be 50 to 100%.

B. Measure the temperature and pressure 21: Measure the ice water inlet water temperature value (hereinafter referred to as CWRT) of the evaporator 11 using a temperature sensor 110, and measure the ice water of the evaporator 11 by using a temperature sensor 111. The outlet water temperature value (hereinafter referred to as CWLT); using a pressure sensor 112 to measure the refrigerant evaporation pressure value of the evaporator 11 or the suction pipe 121 of the compressor (hereinafter referred to as RSEP); using a temperature sensor 120 The refrigerant discharge temperature value (hereinafter abbreviated as SHDT) of the compressor 12 is measured; the refrigerant condensing pressure value (hereinafter referred to as RSCP) of the condenser 13 or the discharge pipe 122 of the compressor is measured using a pressure sensor 130; CWRT, The CWLT, RSEP, SHDT, and RSCP are transmitted to the controller 10.

C. Whether the compressor 12 is in operation 22: If the compressor 12 is not operating, the electronic expansion valve 14 has an opening degree of 0% 220 and ends 221; if the compressor 12 is operated, the process continues to the next step.

D. Calculating the desired refrigerant discharge temperature value of the compressor 12 and the desired arithmetic mean temperature difference 23 of the evaporator 11: The controller 10 obtains the desired refrigerant discharge temperature value of the compressor 12 based on RSEP, RSCP and _CSHDT (hereinafter referred to as , SHDT _exp ), the calculation formula is: SHDT _exp = {a + b × (RSCP) + c × (RSCP) ² + d × (RSEP) + C _SHDT }, where a, b, c, d are constant. The controller 10 based CWRT, CWLT, △ T, C △ tm and △ t _m, to derive the evaporator 11 of the arithmetic mean temperature difference desired value _{(hereinafter, △ t m (exp))} , is calculated as: △ t _{m (exp) = (CWRT-CWLT} ) / △ T × △ t m + C △ tm. .

E. Calculating the evaporation temperature value of the refrigerant 24: The controller 10 obtains a refrigerant evaporation temperature value (hereinafter referred to as RSET) according to RSEP, and the calculation formula is: RSET=a1+b1×(RSEP)+c1×(RSEP) ^0.5 , where a1, b1, and c1 are constant.

F. Calculate the actual arithmetic mean temperature difference value 25: The controller 10 obtains an actual arithmetic mean temperature difference value (hereinafter referred to as Δt _m(real) ) according to CWRT, CWLT and RSET, and the calculation formula is: Δt _{m (real)} = [(CWRT+CWLT)/2]-RSET.

G. Calculating the error value of the refrigerant discharge temperature value and the arithmetic mean temperature difference value 26: The controller 10 obtains an actual and desired discharge temperature error value (hereinafter referred to as Err _△SHDT ) according to SHDT and SHDT _exp , and the calculation formula is: _{Err △ SHDT = SHDT-SHDT exp} ; controller 10 based △ t _{m (exp)} and △ t _{m (real),} to derive an arithmetic mean temperature difference between the actual and the desired error value (hereinafter, Err _{△ tm),} calculated It is: Err _Δtm = Δt _m(exp) - Δt _m(real) .

H, whether the compressor 12 is running greater than or less than a specific time 27: if the compressor 12 is running less than or equal to a specific time, the electronic expansion valve If the opening degree of 14 is 50~100% 270, the process returns to step B271 above, and the whole step is repeated, the specific time is 3~5 minutes; if the compressor 12 is operated longer than the specific time, the next step is performed. step.

I, _{Err △} SHDT determined is less than or equal to a predetermined value greater than 28: controller 10 determines for _{Err △} SHDT, if _{Err △} SHDT greater than or less than or equal to a set value, the set value may be zero, is less than if _{Err △} SHDT When it is equal to zero, the liquid compression protection flag 280 is turned on, and the electronic expansion valve 14 is successively reduced by 5% of the opening degree 281 in a fixed output force period to perform a liquid compression protection process until the SHDT is greater than SHDT _exp , that is, electronic expansion The maximum opening limit of the valve 14 is equal to the current opening degree 282 of the electronic expansion valve 14 and returns to step B 283; if Err _{△SHDT is} greater than zero, the liquid compression protection flag 284 is closed, and the maximum opening limit of the electronic expansion valve is limited. Release 285 and proceed to the next step.

J. Determine whether the absolute value of Err _Δtm is less than or equal to dead band 29: if it is less than or equal to the dead band, the electronic expansion valve 14 maintains the existing opening degree 290 and returns to step B 283; if it is greater than the dead band The controller 10 calculates the desired opening degree and the number of operating steps 291 of the electronic expansion valve 14 to adjust the opening degree of the electronic expansion valve 14, and increases the opening degree of the electronic expansion valve 14 if the number of operating steps is positive. 292, and return to step B 283; if the number of action steps is negative, the opening degree 293 of the electronic expansion valve 14 is decreased, and the process returns to step B 283 described above.

The purpose of returning to step B is to repeat the entire step to avoid the situation in which the protection process of liquid compression occurs repeatedly.

After the temperature is set, the actual pressure is measured, and the actual temperature is measured, the controller 10 determines whether to adjust the opening degree of the electronic expansion valve 14 according to the foregoing data and the correction value. Effectively improve the operating efficiency of the chiller under partial load conditions and the optimal refrigerant level. However, the change of ice water flow will change the temperature difference between the ice water and the water, which will cause the initial set △T to have a large error value, and will cause the opening of the electronic expansion valve 14 to be improperly adjusted, so △T must be The actual ice water temperature difference is automatically corrected. The correction method is applied to the above steps A and B. The steps of the correction method are as follows:

1. Set the ice water inlet and outlet water temperature difference 30 of the rated full load operation condition: as in step A above, set a nominal ice water inlet and outlet water temperature difference (hereinafter referred to as △T _setpoint ), and the △T _setpoint system described in this step Equal to the above ΔT.

2. Whether the compressor 12 is running 31: If the compressor 12 is not running, the process ends 310; if the compressor 12 is running, the next step is performed.

3. Whether the compressor reaches the full load condition 32: If the compressor 12 does not reach the full load condition, that is, 100%, then the fault is not corrected 320, and step 2 is 351; if the compressor 12 is operated to the full load condition, the next step is performed. One step.

4. Calculate the difference between the temperature of the ice water and the water flowing out of the compressor 12 under full load conditions: the controller 10 obtains the temperature difference between the ice water and the water when the compressor 12 is operated under full load conditions according to CWRT and CWLT (hereinafter referred to as , ΔT _real ), the calculation formula is: ΔT _real = CWRT-CWLT.

5. Automatically determine whether to re-adjust the rated ice water inlet and outlet water temperature difference setting value 34: the controller 10 obtains an error value according to ΔT _setpoint and ΔT _real , and if the absolute value of the error value is less than or equal to a set value, The set value may be 5%, then the error is not corrected 320, and to step two 351, the calculation formula is: ABS (ΔT _real - ΔT _setpoint ) / ΔT _setpoint ≧ 5%; if the absolute value is greater than the set value, Then proceed to the next step.

6. Determine whether the number of consecutive occurrences is equal to or less than a fixed number of times 35: the fixed number of times may be five to ten times. If the absolute value of step 5 is greater than the set value, but the number of occurrences is less than the fixed number of times, 320 is not corrected. And step 2 351; if the number of occurrences is equal to the fixed number of times, ΔT _setpoint is equal to ΔT _real 350, that is, ΔT _{real is} replaced by ΔT set in step one, and then returns to step two 351 to repeat the entire step .

In summary, the invention is based on _{△ T, △ t m, C} △ tm, dead band, C SHDT, CWRT, CWLT, RSEP, SHDT, RSCP, SHDT exp, △ t m (exp), RSET, △ t m ( _{real), Err △ SHDT, Err} △ tm, decide whether to adjust electronic expansion valve opening degree of 14, to enhance the operating efficiency of the ice machine, and may vary with the actual state of △ T, the correction is performed, so that the electronic The opening degree of the expansion valve 14 can be adjusted according to the actual state, thereby controlling the flow rate of the refrigerant, so that the refrigerant of the evaporator 11 can be located at the optimum liquid level, and the heat exchange area of the evaporator 11 can be effectively utilized, and the evaporation temperature can be raised. The evaporator 11 is operated at an optimum refrigerant evaporation temperature.

However, the specific embodiments described above are merely used to exemplify the features and functions of the present invention, and are not intended to limit the scope of the present invention, and may be applied without departing from the spirit and scope of the present invention. Equivalent changes and modifications made to the disclosure of the present invention are still covered by the scope of the following claims.

10‧‧‧ Controller

11‧‧‧Evaporator

110‧‧‧temperature sensor

111‧‧‧Temperature Sensor

112‧‧‧pressure sensor

12‧‧‧Compressor

120‧‧‧temperature sensor

121‧‧‧Compressor suction pipe

122‧‧‧Compressor discharge tube

13‧‧‧Condenser

130‧‧‧pressure sensor

14‧‧‧Electronic expansion valve

20~293‧‧‧Steps

30~351‧‧‧ steps

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic view of an ice water machine to which the liquid level evaporator control method of the full liquid evaporator is applied.

2A and 2B are schematic diagrams showing the flow of a liquid level control method for a flooded evaporator of the present invention.

FIG. 3 is a schematic flow chart of the difference between the ice water and the water outlet temperature of the modified full rated load according to the present invention.

10‧‧‧ Controller

11‧‧‧Evaporator

110‧‧‧temperature sensor

111‧‧‧Temperature Sensor

112‧‧‧pressure sensor

12‧‧‧Compressor

120‧‧‧temperature sensor

121‧‧‧Compressor suction pipe

122‧‧‧Compressor discharge tube

13‧‧‧Condenser

130‧‧‧pressure sensor

14‧‧‧Electronic expansion valve

Claims (22)

A method for controlling a liquid level of a full-liquid evaporator refrigerant comprises the steps of: A. setting a basic condition: setting a plurality of temperature difference values and a plurality of correction values, the temperature difference value and the correction value being a rated arithmetic of the evaporator Average temperature difference, a nominal ice water inlet and outlet water temperature difference, an arithmetic mean temperature difference correction value, an arithmetic mean temperature difference neutral band and a discharge temperature correction value, and an initial opening of an electronic expansion valve at a compressor start-up operation The set value can be set to 50~100%; B, measuring temperature and pressure: measuring the ice water inlet water temperature value, an ice water outlet water temperature value, a refrigerant evaporation pressure value, a refrigerant condensation pressure value and a refrigerant The temperature value of the squirting water, the ice water inlet water temperature value and the ice water effluent temperature value are an ice water inlet water temperature value and an ice water outlet water temperature value, and the refrigerant discharge temperature value is a refrigerant refrigerant discharge temperature value of the compressor. The refrigerant evaporation pressure value is a refrigerant evaporation pressure value of an evaporator or a compressor suction pipe, and the refrigerant condensation pressure value is a refrigerant condensation pressure value of a condenser or a compressor discharge pipe; Calculating the error value: according to the data obtained in the steps A and B, the error value is obtained; in the step C, the method further has: C1, calculating the expected discharge temperature value of the compressor and the expected arithmetic mean temperature difference of the evaporator: The refrigerant evaporation pressure value, the refrigerant condensation pressure value and the discharge temperature correction value, to obtain a desired discharge temperature value of the compressor, and the ice water inlet water temperature value, the ice water water outlet temperature value, the rated ice water according to the ice water inlet water temperature value The difference between the inlet and outlet water temperature, the arithmetic mean temperature difference correction value and the rated arithmetic mean temperature difference The desired arithmetic mean temperature difference of the evaporator; C2, calculating the refrigerant evaporation temperature value: according to the refrigerant evaporation pressure value, a refrigerant evaporation temperature value is obtained; C3, calculating the actual arithmetic mean temperature difference value: according to the ice water inlet water temperature a value, the ice water outlet temperature value and the refrigerant evaporation temperature value, and an actual arithmetic mean temperature difference value; C4, calculating an error value of the refrigerant discharge temperature and the arithmetic mean temperature difference value: according to the refrigerant discharge temperature value and the desired refrigerant Sampling the temperature value to obtain an actual and desired discharge temperature error value, and obtaining an actual and desired arithmetic mean temperature difference value according to the actual arithmetic mean temperature difference value and the expected arithmetic mean temperature difference value; D, controlling the electronic expansion The opening degree of the valve: according to the error value obtained in the step C, to control the opening degree of the electronic expansion valve; in the step D, the method further has: D1, determining whether the actual and desired discharge temperature error value is less than or equal to or greater than a set value: if the actual and desired discharge temperature error value is less than or equal to the set value, the liquid compression protection flag is turned on to reduce the power The opening degree of the expansion valve; if the actual and desired discharge temperature error value is greater than the set value, the liquid compression protection flag is turned off, and proceeds to the next step; D2, determining whether the actual and desired arithmetic mean temperature difference error value is greater than Or less than or equal to the arithmetic mean temperature difference neutral band: if less than or equal to the arithmetic mean temperature difference neutral band, the electronic expansion valve maintains the existing opening degree, and returns to the step B; if greater than the arithmetic mean temperature difference neutral band , adjusting the opening of the electronic expansion valve and returning Go to step B. The method for controlling the liquid level of a full liquid evaporator according to claim 1, wherein in the step C1, the refrigerant evaporation pressure value is simply referred to as RSEP, and the refrigerant condensation pressure value is simply referred to as RSCP, and the discharge is performed. The temperature correction value is abbreviated as C _SHDT , and the expected discharge temperature value is simply referred to as SHDT _exp . The calculation formula of the desired discharge temperature value is: SHDT _exp = {a + b × (RSCP) + c × (RSCP) ² + d ×(RSEP)+C _SHDT }, and a, b, c, and d are constants. The method for controlling the liquid level of the full liquid evaporator according to the second aspect of the patent application, wherein in the step C1, the ice water inlet water temperature value is simply referred to as CWRT, and the ice water outlet water temperature value is simply referred to as CWLT. The arithmetic mean temperature difference correction value is abbreviated as C _Δtm , and the nominal arithmetic mean temperature difference is simply referred to as Δt _m , and the desired arithmetic mean temperature difference is simply referred to as Δt _m(exp) , and the desired arithmetic mean temperature difference value is The formula _{is: △ t m (exp) =} (CWRT-CWLT) / △ T × △ t m + C △ tm. The method for controlling the liquid level of a full liquid evaporator according to claim 3, wherein in the step C2, the evaporation temperature value of the refrigerant is abbreviated as RSET, and the calculation formula of the evaporation temperature value of the refrigerant is: RSET = a1 + b1 × (RSEP) + c1 × (RSEP) ^0.5 , where a1, b1, and c1 are constants. The method for controlling the liquid level of a full liquid evaporator according to claim 4, wherein in the step C3, the actual arithmetic mean temperature difference is abbreviated as Δt _m(real) , the actual arithmetic mean temperature difference. The calculation formula is: Δt _m(real) = [(CWRT+CWLT)/2]-RSET. The method for controlling the liquid level of a full liquid evaporator according to claim 5, wherein in the step C4, the actual and desired discharge temperature error values are simply referred to as Err _ΔSHDT , the actual and desired discharge temperature errors. calculated values _{as: Err △ SHDT = SHDT-SHDT} exp; the actual and the desired arithmetic average temperature difference between an error value referred to as Err _{△ tm,} calculated average error value of the temperature difference between the actual and the desired arithmetic as: Err _{△ tm} = _△ t _m(exp) - Δt _m(real) . The method for controlling the liquid level of a full liquid evaporator according to claim 6, wherein the arithmetic mean temperature correction value is between -0.5 and 0.5, and the discharge temperature correction value is between 0 and 5. The method for controlling the liquid level of a full liquid evaporator according to claim 1, wherein in the step B, the temperature value of the ice water is measured by a plurality of temperature sensors, and the ice water is measured. The outlet water temperature value and the refrigerant discharge temperature value, and the plurality of pressure sensors respectively measure the refrigerant evaporation pressure value and the refrigerant condensation pressure value, and the temperature sensor and the pressure sensor system measure the same The ice water inlet water temperature value, the ice water outlet water temperature value, the refrigerant discharge temperature value, the refrigerant evaporation pressure value, and the refrigerant condensation pressure value are transmitted to a controller. The method for controlling a liquid level of a flooded evaporator refrigerant according to claim 8, wherein the pressure sensor measures a refrigerant condensation pressure value of the condenser or the discharge pipe of the compressor, and the pressure The sensor measures the refrigerant evaporation pressure value of the evaporator or the suction pipe of the compressor. The method for controlling the liquid level of a full liquid evaporator according to claim 1, wherein the step B and the step C1 further have a step of whether the compressor is running, and if the compressor is not running, End; if the compressor is running, proceed to step C1. The method for controlling the liquid level of a full liquid evaporator according to claim 1, wherein the step C4 and the step D1 further have a step of whether the compressor is operated for greater than or equal to a specific time. If the compressor operation is less than or equal to the specific time, the opening degree of the electronic expansion valve is 50 to 100%, then return to the step B; if the compressor operation is greater than the specific time, the step D1 is performed. The method for controlling the liquid level of a flooded evaporator as described in claim 11, wherein the specific time is 3 to 5 minutes. The control method of the liquid level of the full liquid evaporator in the first embodiment of the invention, wherein in the step D1, the electronic expansion valve is successively reduced by 5% opening in a fixed output force period, and the The maximum opening limit of the electronic expansion valve is equal to the current opening of the electronic expansion valve. The method for controlling the liquid level of a flooded evaporator as described in claim 13 wherein the set value is zero in the step D1. The method for controlling the liquid level of a full liquid evaporator according to claim 13 , wherein in the step D1, when the liquid compression protection flag is turned off, the maximum opening degree of the electronic expansion valve is released, and enters This step D2. The method for controlling a liquid level of a full liquid evaporator according to claim 1, wherein in the step D2, the controller calculates the electronic expansion valve when the neutral band is greater than the arithmetic mean temperature difference. The opening degree and the number of action steps are desired to adjust the opening degree of the electronic expansion valve. The method for controlling the liquid level of the flooded evaporator refrigerant according to claim 16, wherein when the number of the operation steps is positive, the opening degree of the electronic expansion valve is increased, and the step B is returned. The method for controlling the liquid level of a flooded evaporator refrigerant according to claim 16, wherein when the number of the operation steps is a negative value, the opening degree of the electronic expansion valve is decreased, and the process returns to the step B. The method for controlling a liquid level of a full liquid evaporator according to claim 1, wherein the rated arithmetic mean temperature difference, the rated ice water inlet and outlet water temperature difference, and the arithmetic mean temperature difference correction value are set in the control. In the device. The method for controlling the liquid level of a full-liquid evaporator according to claim 1, wherein the step A and the step B further have a method for correcting a temperature difference between the rated ice water and the water, the correction The method for rating the temperature difference between the ice water and the outlet water has the following steps: 1. setting the temperature difference between the ice water and the outlet water of the rated full load operation condition: setting a temperature difference between the rated ice water and the outlet water, and the temperature difference between the rated ice water inlet and outlet water is equal to the step A. The temperature difference between the rated ice water and the inlet water; 2. Whether the compressor is running: if the compressor is not running, it ends; if the compressor is running, the next step is performed; 3. Whether the compressor reaches the full load condition: If the compressor does not reach the full load condition, if it is not corrected, go to step 2; if the compressor runs to full load condition, proceed to the next step; 4. Calculate the ice water in and out of the compressor under full load conditions. Temperature difference: According to the ice water inlet water temperature value and the ice water outlet water temperature value, the controller obtains the ice water inlet and outlet water temperature difference when the compressor is under full load condition; 5. automatically determines whether to re-adjust The set value of the whole rated ice water inlet and outlet water temperature difference: according to the difference between the rated ice water inlet and outlet water temperature difference and the ice water inlet and outlet water temperature difference, an error value is obtained, if the absolute value of the error value is less than or equal to When a set value is set, it does not operate, and to step 2; if the absolute value is greater than the set value, the next step is performed; 6. Determine whether the number of consecutive occurrences is equal to or less than a fixed number of times: if the absolute value is greater than If the number of occurrences of the set value is equal to the fixed number of times, the ice water inlet and outlet water temperature difference replaces the rated ice water inlet and outlet water temperature difference, and returns to the second step; if the absolute value is greater than the set value, the occurrence frequency is less than the fixed The number of times, then not corrected, and to the second step. The method for controlling the liquid level of a flooded evaporator refrigerant according to claim 20, wherein the set value is 5%, and the fixed number of times is five to ten times. The method for controlling the liquid level of a full liquid evaporator according to claim 21, wherein the ice water inlet water temperature value is simply referred to as CWRT, and the ice water outlet water temperature value is simply referred to as CWLT, and the ice water enters and exits water. The abbreviation of the temperature difference is ΔT _real , and the calculation formula of the ice water inlet and outlet water temperature difference is: ΔT _real = CWRT-CWLT; the nominal ice water inlet and outlet water temperature difference is abbreviated as ΔT _setpoint , and the error value is calculated as : ABS (△T _real - ΔT _setpoint ) / ΔT _setpoint ≧ 5%.