Control method and system for expansion valve of heat pump unit
Technical Field
The invention relates to the technical field of heat pumps, in particular to a control method and a control system for an expansion valve of a heat pump unit.
Background
At present, use electronic expansion valve control's unit, electronic expansion valve control strategy generally adopts the superheat degree control of breathing in or the control of exhaust superheat degree, and its control theory mainly is through guaranteeing that the evaporimeter export is superheated steam to the protection compressor does not take place liquid compression, thereby protects the compressor.
For the traditional control of the suction superheat degree, the control is mainly the superheat degree of a refrigerant at the outlet of an evaporator, when the superheat degree at the outlet of the evaporator is 3-5 ℃, the condition that the compressor does not generate hydraulic compression can be ensured, but when the compressor is used for heating at high ambient temperature, if the control is still carried out according to the superheat degree of 3-5 ℃, the evaporation temperature is very high at the moment and even exceeds the evaporation temperature allowed to operate by the compressor, and at the moment, the compressor is possibly damaged for the reason.
The control strategy of the expansion valve is adjusted through different working conditions, so that the unit adapts to various environmental working conditions, and the unit can be safely and reliably allowed.
To solve this problem, the present invention is hereby proposed.
Disclosure of Invention
The invention aims to provide a control method of an expansion valve of a heat pump unit, which adopts a control strategy combining evaporation temperature control and superheat degree control.
The purpose of the invention can be realized by the following technical scheme:
a control method for an expansion valve of a heat pump unit comprises the following steps:
s1, acquiring the current environment temperature Tn, and turning to S2;
s2, judging whether Tn is less than or equal to the interval environment temperature Ts, if yes, turning to S3, if no, turning to S4;
s3, controlling the expansion valve by adopting normal suction superheat degree;
s4, controlling the expansion valve by adopting evaporation temperature control.
Preferably, the compartment ambient temperature Ts is 35 ℃.
Further, the control of the expansion valve adopts the normal suction superheat degree control to determine the numerical value of the control target superheat degree, the control target superheat degree is the set target superheat degree + a correction value S, and the correction value S is obtained by searching a superheat degree correction value S value taking table.
Preferably, the target degree of superheat is set to 1 ℃.
Further, the specific search method of the superheat correction value S value taking table is as follows:
s31, acquiring the current environment temperature Tn and the effluent temperature Tw, and turning to S32;
s32, searching a superheat correction value S value taking table to obtain a correction value S, and turning to S33;
and S33, setting the control target superheat degree as the set target superheat degree + the correction value S.
Preferably, the control of the expansion valve adopts evaporation temperature control, namely, the highest evaporation temperature Th allowed by the compressor is obtained, the opening degree of the expansion valve is kept unchanged when the evaporation temperature of the evaporator is between intervals (20, Th-1), the expansion valve is closed every 10s for 5s when the evaporation temperature is > (Th-1) DEG C, and the expansion valve is opened every 30s for 10s when the evaporation temperature is < (Th-1) DEG C and the evaporation temperature is 5 s.
Further, the control of the expansion valve by adopting the evaporation temperature comprises the following specific steps:
s41, obtaining the maximum evaporation temperature Th allowed by the compressor, and turning to S42;
s42, judging whether the evaporation temperature of the evaporator is in the interval (20, Th-1), if so, turning to S43, and if not, turning to S44;
s43, keeping the opening of the expansion valve unchanged;
s44, judging whether the evaporation temperature is greater than (Th-1) DEG C and continues for 5S, if so, turning to S45, if not, turning to S46;
s45, closing the expansion valve for 10 steps every 10S;
s46, judging whether the evaporation temperature is less than (Th-1) DEG C and continues for 5S, if so, turning to S47, if not, turning to S41;
s47, opening the expansion valve every 30S for 10 steps.
Preferably, the maximum allowable operating evaporating temperature Th of the compressor is 25 degrees.
The invention also provides a control system of the expansion valve of the heat pump unit, which is used for realizing the control method.
The purpose of the invention can be realized by the following technical scheme:
a control system of an expansion valve of a heat pump unit comprises a controller, a compressor, an evaporator, an ambient temperature sensor and an expansion valve, wherein the controller is respectively connected with the compressor, the evaporator, the ambient temperature sensor and the expansion valve; the control mode judging module is used for comparing the current environment temperature with the interval environment temperature and operating the expansion valve superheat degree control module if the current environment temperature is less than or equal to the interval environment temperature; and if the temperature of the current environment is higher than the temperature of the interval environment, operating an expansion valve evaporation temperature control module.
Furthermore, the expansion valve superheat degree control module is used for setting a target superheat degree and adding a correction value to obtain a control target superheat degree; the expansion valve evaporation temperature control module is used for obtaining the highest evaporation temperature Th allowed by the compressor to operate, and is used for judging that the opening degree of the expansion valve is kept unchanged when the evaporation temperature of the evaporator is between intervals (20, Th-1), closing the expansion valve every 10s for 5s when the evaporation temperature is higher than (Th-1) DEG C, and opening the expansion valve every 30s for 10s when the evaporation temperature is lower than (Th-1) DEG C and continues for 5 s.
The invention has the beneficial effects that:
under normal operating mode, use the superheat degree control strategy to ensure the compressor on the hydraulic basis of not taking place, improve the heat exchange efficiency of evaporimeter as far as, make the unit operation more energy-conserving, when high ambient temperature operating mode, use the evaporation temperature control strategy, under the highest evaporating temperature that does not exceed the operation that the compressor allows, stabilize and operate with the highest efficiency in injecing.
Drawings
The invention will be further described with reference to the accompanying drawings.
Fig. 1 is a flow chart of a control method of the expansion valve of the present invention.
FIG. 2 is a flowchart of a lookup method of the correction value S value table according to the present invention.
Fig. 3 is a flow chart of the expansion valve evaporation temperature control of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
Referring to fig. 1, a method for controlling an expansion valve of a heat pump unit includes the following steps:
s1, acquiring the current environment temperature Tn, and turning to S2;
s2, judging whether Tn is less than or equal to the interval environment temperature Ts, if yes, turning to S3, if no, turning to S4;
s3, controlling the expansion valve by adopting normal suction superheat degree;
s4, controlling the expansion valve by adopting evaporation temperature control.
Preferably, the compartment ambient temperature Ts is 35 ℃.
The control of the expansion valve adopts the value of the control target superheat degree which needs to be determined by normal suction superheat degree control, the control target superheat degree is the set target superheat degree + a correction value S, preferably, the set target superheat degree is 1 ℃, and the correction value S is obtained by searching a superheat degree correction value S value taking table.
The value table for finding the superheat correction value S includes three regions, namely an ambient temperature, an effluent temperature, and unique correction values S corresponding to the ambient temperature and the effluent temperature, the ambient temperature is divided into 5 intervals, namely { (∞, -10], (-10, 0], (0, 15], (15, 25], (25, 35] }, the effluent temperature is divided into 4 intervals, namely { (∞, 25], (25, 35], (35,45], (45, + ∞ ] }, and the correspondence is { (∞, -10], (∞, 25], 0}, { ∞, -10], (25, 35], (1 }, (∞, -10], (35,45], -2}, { ∞, -10], (45, + ∞ ], -3}, { (-10, 0], (-25, 25], 0}, { (-10, 0], (25, 35], 0}, { (-10, 0], (35,45], -1}, { (-10, 0], (45, + ∞ ], -2}, { (0, 15], (∞, 25), { (1 }, { (0, 15], (25, 35], 0}, { (0, 15], (35,45], 0}, { (0, 15], (45, (+ -) 1}, { (15, 25], (∞, 25], 2}, { (15, 25], (∞, 25), { (35, 35], 2}, { (15, 25], (35,45 }, { (15, 25], (+ ∞, 1}, (+ - ∞, 25), { (25, 35], (-%, 3}, (-%, (-) 25, 35], (-) 3}, { (25, 35], { (25, 35 }, (- ], { (0 }, { (0, (25, 35], 3}, { (25, 35], (35,45], 2}, { (25, 35], (45, + ∞ ], 2 }.
Referring to fig. 2, the specific search method of the superheat correction value S fetch table is as follows:
s31, acquiring the current environment temperature Tn and the effluent temperature Tw, and turning to S32;
s32, searching a superheat correction value S value taking table to obtain a correction value S, and turning to S33;
and S33, setting the control target superheat degree as the set target superheat degree + the correction value S.
The following table is a superheat correction value S value table: (unit is. degree. C.)
The control of the expansion valve adopts evaporation temperature control, namely, the highest evaporation temperature Th allowed by the compressor is obtained, the opening degree of the expansion valve is kept unchanged when the evaporation temperature of the evaporator is between intervals (20, Th-1), the expansion valve is closed for 10 steps every 10s when the evaporation temperature is higher than (Th-1) DEG C and lasts for 5s, and the expansion valve is opened for 10 steps every 30s when the evaporation temperature is lower than (Th-1) DEG C and lasts for 5 s.
The maximum evaporating temperature that the compressor is allowed to operate may vary depending on the type or brand of compressor.
Preferably, the maximum evaporating temperature Th allowed by the compressor is 25 deg., so that the opening of the expansion valve is kept constant when the evaporating temperature of the evaporator is between the intervals (20, 24), 10 steps are closed every 10s when the evaporating temperature is > 24 deg.C and lasts for 5s, and 10 steps are opened every 30s when the evaporating temperature is < 24 deg.C and lasts for 5 s.
Referring to fig. 3, the control of the expansion valve by adopting the evaporation temperature comprises the following specific steps:
s41, obtaining the maximum evaporation temperature Th allowed by the compressor, and turning to S42;
s42, judging whether the evaporation temperature of the evaporator is in the interval (20, Th-1), if so, turning to S43, and if not, turning to S44;
s43, keeping the opening of the expansion valve unchanged;
s44, judging whether the evaporation temperature is greater than (Th-1) DEG C and continues for 5S, if so, turning to S45, if not, turning to S46;
s45, closing the expansion valve for 10 steps every 10S;
s46, judging whether the evaporation temperature is less than (Th-1) DEG C and continues for 5S, if so, turning to S47, if not, turning to S41;
s47, opening the expansion valve every 30S for 10 steps.
Example 2
A control system of an expansion valve of a heat pump unit comprises a controller, a compressor, an evaporator, an ambient temperature sensor and an expansion valve, wherein the controller is respectively connected with the compressor, the evaporator, the ambient temperature sensor and the expansion valve, the ambient temperature sensor is used for measuring ambient temperature, the expansion valve is positioned on a pipeline of a refrigerant inlet of the compressor, an evaporation temperature sensor is arranged on the evaporator and used for measuring the temperature of the refrigerant during evaporation in the evaporator, the control system comprises an ambient temperature acquisition module, a control mode judgment module, an expansion valve superheat degree control module and an expansion valve evaporation temperature control module, and the ambient temperature acquisition module is used for acquiring the current ambient temperature; further, the environment temperature acquisition module reads the current environment temperature measured by the environment temperature sensor through the controller, and controls the mode judgment module, the control mode judgment module compares the current environment temperature with the interval environment temperature, and if the current environment temperature is less than or equal to the interval environment temperature, the expansion valve superheat degree control module is operated; and if the temperature of the current environment is higher than the temperature of the interval environment, operating an expansion valve evaporation temperature control module.
The expansion valve superheat degree control module is used for setting a target superheat degree and adding a correction value to obtain a control target superheat degree.
The expansion valve evaporation temperature control module is used for obtaining the highest evaporation temperature Th allowed by the compressor to operate, and is used for judging that the opening degree of the expansion valve is kept unchanged when the evaporation temperature of the evaporator is between intervals (20, Th-1), closing the expansion valve every 10s for 10 steps when the evaporation temperature is higher than (Th-1) DEG C and lasts for 5s, and opening the expansion valve every 30s for 10 steps when the evaporation temperature is lower than (Th-1) DEG C and lasts for 5 s.
While there have been shown and described what are at present considered the fundamental principles and essential features of the invention and its advantages, it will be apparent to those skilled in the art that the invention is not limited to the details of the foregoing exemplary embodiments, but is capable of other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.