High-energy-efficiency heating control device and method based on low-temperature enhanced vapor injection

Abstract

The invention belongs to the technical field of low-temperature heating, and particularly relates to a high-energy-efficiency heating control device based on low-temperature enhanced vapor injection, which comprises an enhanced vapor injection compressor, an evaporator, a condenser and an economizer, and gaseous and liquid refrigerants are fed into the economizer by the condenser through a pipeline. By adding the air supply port, the medium-pressure gaseous refrigerant from the economizer is mixed with low-pressure sucked air for secondary compression, the exhaust temperature is increased, the heating capacity is improved, and the air supply device is particularly suitable for the low-temperature environment of-15 DEG C or below; traditional single-stage compression is divided into three stages of air suction compression, air supply mixing and secondary compression, and the purposes of reducing the exhaust temperature of a compressor, avoiding overheating damage, increasing the circulating flow of a refrigerant, improving the heating capacity, optimizing the heat exchange efficiency of a condenser and transferring more heat from the outdoor to the indoor are achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of low-temperature heating technology, in particular to a high-energy-efficiency heating control device and method based on low-temperature jet augment. BACKGROUND

[0002] Under low-temperature environment, the heating performance of ordinary air energy heat pump will be significantly attenuated, and the jet augment technology breaks through this limitation through innovative system design, becoming the key technology for efficient heating in severe cold regions.

[0003] The key to efficient heating in low-temperature environment lies in the following three points: reducing the compressor discharge temperature, increasing the refrigerant circulation flow, and optimizing the condenser heat exchange efficiency.

[0004] The existing heating system lacks controllable air supplement, although the air supplement augment technology can alleviate the above problems, but the air supplement is easily affected by low-temperature working condition fluctuation, leading to "excessive air supplement" or "insufficient air supplement", which in turn causes abnormal exhaust temperature and heat efficiency loss;

[0005] The evaporator outlet refrigerant dryness is less than 0.85, which will cause high liquid knock failure rate;

[0006] When starting for the second time, the compressor starting torque is too high, and there is a certain probability of starting failure;

[0007] The lubricating oil temperature is insufficient, in low-temperature environment, the bearing wear is high, which in turn causes the compressor to be easily damaged or the noise to be too large.

[0008] Therefore, we propose a high-energy-efficiency heating control method based on low-temperature jet augment, which divides the traditional single-stage compression into three stages of "suction compression → air supplement mixing → secondary compression", so as to reduce the compressor discharge temperature, avoid overheating damage, increase the refrigerant circulation flow, improve the heating capacity, and optimize the condenser heat exchange efficiency, so as to transfer more heat from outdoor to indoor. SUMMARY

[0009] In order to overcome the above-mentioned defects of the prior art, the present application provides a high-energy-efficiency heating control method based on low-temperature jet augment, to solve the problems existing in the background art.

[0010] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a high-energy-efficiency heating control device based on low-temperature jet augment, comprising a jet augment compressor, an evaporator, a condenser and an economizer, the jet augment compressor sends the gaseous and liquid states of the refrigerant into the condenser through a pipeline, the condenser sends the gaseous and liquid states of the refrigerant into the economizer through a pipeline, the economizer sends the gaseous and liquid states of the refrigerant into the evaporator through a pipeline, and the vaporizer collects the vapor and liquid through a gas-liquid separator through a pipeline to a corresponding collector and compressor, respectively.

[0011] The jet augmenting compressor is additionally provided with a gas injection port, and a medium pressure steam is injected into the jet augmenting compressor during the compression process, which is formed by combining the medium pressure gas stream of the economizer and the steam of the evaporator;

[0012] The medium pressure gas stream of the economizer and the steam of the evaporator are mixed in the collector, an electromagnetic valve is installed between the economizer and the collector, a first expansion valve is installed in the pipeline connecting the condenser and the economizer, and a second expansion valve is installed in the pipeline connecting the economizer and the evaporator;

[0013] The cooperative control system: the cooperative control system is realized through the controller and the multi-sensor linkage.

[0014] Further, the collector is closed at one end facing the compressor and is connected with a venturi tube, stirring vanes are installed in the collector, and a ring body is installed in the collector, and the middle part of the ring body is connected with the stirring vanes through a bearing.

[0015] Further, the gas injection control is realized by opening the electromagnetic valve to adjust the flow when the ambient temperature is less than -10℃ and the compressor exhaust temperature is greater than 90℃, a target value of the superheat degree is set, the flow of the refrigerant in the economizer is controlled through the opening degree of the first expansion valve, and the medium pressure steam is generated; then the mixing optimization is realized by accelerating the airflow through the venturi tube of the collector and dispersing the liquid droplets through the stirring vanes.

[0016] Further, the economizer control is realized by setting a target value of the economizer pressure and controlling the opening degree through the second expansion valve, so that the liquid refrigerant is fully evaporated in the economizer, the baffle and the screen separator in the economizer intercept the liquid refrigerant, the gaseous refrigerant enters the collector, and the liquid refrigerant enters the evaporator through the second expansion valve to complete the gas-liquid separation.

[0017] Further, the pressure gradient control is realized by opening the electromagnetic bypass valve when the pressure difference between the high-pressure side and the low-pressure side is greater than 1.5 MPa after the jet augmenting compressor is stopped, and then the refrigerant on the high-pressure side slowly flows into the low-pressure side through the capillary tube, so that the pressure difference is reduced to less than 0.3 MPa within a time period to complete the pressure release.

[0018] Further, the temperature linkage control is realized by opening the heating belt when the ambient temperature is less than -10℃ and the oil temperature is less than 40℃, and the PID algorithm is used to adjust the heating power to maintain the oil temperature at 40±2℃ to complete the constant temperature control.

[0019] A high energy efficiency heating control method based on low temperature jet augmenting;

[0020] S1: The refrigerant liquid and steam are sent to the condenser, the economizer and the evaporator in sequence through the pipeline by the jet augmenting compressor, the liquid and the steam are separated through the gas-liquid separator of the evaporator, and the liquid is sent back to the jet augmenting compressor by the evaporator;

[0021] S2: The steam is sent to the collector by the gas-liquid separator, and the medium-pressure steam of the economizer is sent to the collector synchronously by the electromagnetic valve, and the two streams are mixed in the collector and sent to the injection port of the compressor through the Venturi tube;

[0022] S3: The injection control is controlled by the electromagnetic valve to control the injection of the economizer to the collector, the refrigerant flow into the economizer is adjusted by the first electronic expansion valve, the medium-pressure steam of the economizer is mixed with the evaporator steam in the collector to generate pure gaseous medium-pressure steam, when the ambient temperature is less than -10°C and the compressor discharge temperature is greater than 90°C, the electromagnetic valve is opened for flow regulation to set the superheat degree to 5-8°C, the economizer refrigerant flow is controlled by the opening of the first expansion valve, and when the ambient temperature is -20°C, the opening is increased from 20% to 40%, so that the medium-pressure steam reaches 0.5-1.0 MPa, the gas flow is accelerated by the Venturi tube of the collector, and the liquid droplets are dispersed by the flow mixing leaves, so that the steam dryness is greater than 0.98;

[0023] S4: The economizer control adjusts the refrigerant flow of the economizer into the evaporator through the second electronic expansion valve, the gaseous refrigerant output by the economizer is sent to the injection control, and the liquid refrigerant is sent to the evaporator, the pressure value of the economizer is 0.2-0.5 MPa, and the liquid refrigerant is intercepted by the baffle and the wire mesh separator in the economizer, the gaseous refrigerant enters the collector, and the liquid refrigerant enters the evaporator through the second expansion valve.

[0024] S5: The pressure gradient control opens the electromagnetic bypass valve when the high-low pressure side pressure difference is greater than 1.5 MPa after the jet augmenting compressor is stopped, and the high-pressure side refrigerant slowly flows into the low-pressure side through the capillary tube, and the pressure difference is reduced to less than 0.3 MPa within 55-65 seconds.

[0025] S6: The temperature linkage control is provided with active heating by the crankcase heating belt at the bottom of the jet augmenting compressor; the oil temperature is monitored in real time by the internal oil temperature sensor, and when the ambient temperature is less than -10°C and the oil temperature is less than 40°C, the heating belt is opened; the heating power is adjusted by the PID algorithm, and when the oil temperature is 35°C, the power is increased from 50W to 100W, and the oil temperature is maintained at 40±2°C;

[0026] S7: The four control modes in S3-S6 are completed by the controller through the coordinated control system through multiple sensor linkage;

[0027] In the defrosting period, when the evaporator is frosted, the controller closes the injection electromagnetic valve, switches the four-way valve to reverse defrosting, and melts the frost layer by using the heat of the compressor exhaust;

[0028] In high load operation, when the compressor current > rated value 90%, the controller down-regulates the compressor frequency, and at the same time, the double expansion valve opening degree is reduced, so that the refrigerant flow is synchronously reduced;

[0029] When the ambient temperature fluctuates, when the ambient temperature rises by 8-12℃, the controller reduces the opening degree of the first expansion valve to reduce the amount of air supplement, so as to maintain the heating capacity matching the load.

[0030] Compared with the prior art, the technical effects and advantages of the present application are:

[0031] (1) The high energy efficiency heating control device based on low temperature jet enthalpy increase of the present application increases the air supplement port, mixes the medium pressure gaseous refrigerant from the economizer with the low pressure suction, and then performs secondary compression, so as to improve the exhaust temperature and the heating capacity, especially suitable for low temperature environment below-15℃, through quasi-secondary compression+intermediate air supplement, the traditional single-stage compression is divided into "suction compression→air supplement mixing→secondary compression" three stages, so as to reduce the compressor exhaust temperature, avoid overheating damage, increase the refrigerant circulation flow, improve the heating capacity, optimize the condenser heat exchange efficiency, and transfer more heat from the outdoor to the indoor.

[0032] (2) The high energy efficiency heating control method based on low temperature jet enthalpy increase of the present application precisely adjusts the medium pressure steam flow through air supplement control, optimizes the compressor air supplement efficiency through adjusting the medium pressure steam flow generated by the economizer, and improves the low temperature heating capacity; through the economizer control, two-stage throttling and gas-liquid separation optimization are completed, so as to ensure efficient gas-liquid separation in the economizer, avoid liquid refrigerant entering the compressor air supplement port, and reduce the compressor liquid return failure rate; through pressure gradient control, the restart difficulty problem caused by the pressure difference between the high pressure side and the low pressure side after the compressor stops is solved, the bearing wear caused by the compressor high load start can be reduced; temperature control, low temperature start reduces the torque, so that the compressor wear is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 It is a whole structure schematic diagram of the present application;

[0034] Figure 2 It is a collector structure schematic diagram of the present application.

[0035] The figure mark is: 1, compressor; 2, condenser; 3, economizer; 4, evaporator; 5, gas-liquid separator; 6, collector; 61, ring body; 62, flow stirring blade; 63, venturi; 7, first expansion valve; 8, second expansion valve; 9, electromagnetic valve. DETAILED DESCRIPTION

[0036] The technical solutions in the present application will be described clearly and completely in combination with the drawings in the present application. In addition, the forms of the structures described in the following embodiments are only examples, and the structures involved in the present application are not limited to the structures described in the following embodiments. All other embodiments obtained by those of ordinary skill in the art without creative labor belong to the scope of protection of the present application.

[0037] Embodiments:

[0038] Please refer to Figures 1-2 The present application provides a technical solution: a high-energy-efficiency heating control device based on low-temperature jet augment, comprising a jet augment compressor 1, an evaporator 4, a condenser 2 and an economizer 3. The jet augment compressor 1 sends gaseous and liquid refrigerants into the condenser 2 through a pipeline. The condenser 2 sends gaseous and liquid refrigerants into the economizer 3 through a pipeline. The economizer 3 sends gaseous and liquid refrigerants into the evaporator 4 through a pipeline. The steam generator is connected to the collector 6 and the compressor 1 through a gas-liquid separator 5.

[0039] The flow path from the condenser 2 to the economizer 3: After the high-pressure gaseous refrigerant is liquefied in the condenser 2, most of the saturated liquid refrigerant flows out of the main outlet of the condenser 2 and flows to the first expansion valve 7 through a pipeline leading to the economizer 3. After the liquid refrigerant enters the economizer 3, the pressure drops suddenly, part of the liquid flashes into low-temperature medium-pressure gas to form secondary gas, and the remaining liquid is further cooled to become supercooled liquid due to energy loss and latent heat carried away by the evaporated gas.

[0040] Gas injection from the economizer 3 to the compressor 1: The medium-pressure gas generated in the economizer 3 is introduced through an independent gas pipeline and directly injected into the middle part of the compressor 1 through the gas injection port, reducing the power consumption of the compressor 1 and improving the heating / cooling efficiency under low-temperature conditions.

[0041] The jet augment compressor 1 is additionally provided with a gas injection port. During the compression process of the jet augment compressor 1, medium-pressure steam is formed by the combination of the medium-pressure gas stream from the economizer 3 and the steam from the evaporator 4.

[0042] The medium-pressure gas stream from the economizer 3 and the steam from the evaporator 4 are mixed in the collector 6. An electromagnetic valve 9 is installed between the economizer 3 and the collector 6. A first expansion valve 7 is installed in the pipeline connecting the condenser 2 and the economizer 3. A second expansion valve 8 is installed in the pipeline connecting the economizer 3 and the evaporator 4.

[0043] Cooperative control system: The cooperative control system is realized through a controller and multiple sensors.

[0044] Wherein, the collector 6 is tapered at one end facing the compressor 1, and is connected with a Venturi tube 63, the collector 6 is installed with a stirring blade 62, and the collector 6 is installed with a ring body 61, and the middle part of the ring body 61 is connected with the stirring blade 62 through a bearing.

[0045] The medium-pressure gas flow and steam are mixed by the stirring blade 62, and the low-pressure area is formed through the throat of the Venturi tube 63, and the external air is sucked in by the effect of jet suction and mixed with the main gas flow.

[0046] Wherein, the air supplement control is controlled by the electromagnetic valve 9 to control the air supplement on-off of the economizer 3 to the collector 6, the refrigerant flow into the economizer 3 is adjusted by the first electronic expansion valve, the medium-pressure steam in the economizer 3 is mixed with the steam in the evaporator 4 in the collector 6 to generate pure gaseous medium-pressure steam.

[0047] When the ambient temperature is <-10℃ and the discharge temperature of the compressor 1 is >90℃, the electromagnetic valve 9 is opened to adjust the flow, the target value of the superheat degree is set, the economizer 3 is controlled by the opening of the first expansion valve 7 to adjust the flow of the refrigerant, and the medium-pressure steam is generated; then the mixing optimization is carried out, the airflow is accelerated by the Venturi tube 63 of the collector 6, and the liquid drops are dispersed by the stirring blade 62.

[0048] The air supplement control trigger condition and execution action, when the ambient temperature is <-10℃, the low-temperature air supplement mode is activated, and the crankcase heating belt is started to maintain the oil temperature >40℃;

[0049] When the discharge temperature of the compressor 1 is >90℃, the electromagnetic valve 9 is opened, and the first expansion valve 7 is adjusted to adjust the flow of the refrigerant in the economizer 3;

[0050] The target superheat degree of the medium-pressure steam is 5±0.5℃, and the opening of the first expansion valve 7 is dynamically adjusted by the PID algorithm to adjust the accuracy ±5%

[0051] Or, the target of the air supplement superheat degree is 5-8℃, the flow of the refrigerant in the economizer 3 is controlled by the opening of the first expansion valve 7, and when the ambient temperature is -20℃, the opening is increased from 20% to 40%, and the generated medium-pressure steam is ensured to be 0.5-1.0MPa;

[0052] The airflow is accelerated by the Venturi tube 63 of the collector 6, the liquid drops are dispersed by the stirring blade 62, and the steam dryness is ensured to be >0.98, thereby avoiding liquid impact.

[0053] The main problem to be solved is to increase the mass flow of the compressor 1, so that the air supplement amount is increased by 10%, the mass flow is increased by 8%, the heating capacity is increased by 15%-20%, and the heating capacity attenuation rate is <15% at -25℃;

[0054] The medium-pressure steam cools the inside of the compressor 1, and the discharge temperature is reduced by 8-12℃, such as from 120℃ to below 105℃, and the carbonization of the lubricating oil is avoided.

[0055] Experimental environment configuration

[0056] Parameters Setting values According to Low temperature laboratory -30℃ ~ -10℃ adjustable environmental cabin Simulation of extreme working condition 1 Refrigerant R410A (charge amount ± 2% error) Thermal physical stability under low temperature environment Sensor layout Pressure sensor (± 0.01 MPa precision) Monitor pressure difference (0.2-0.5 MPa) 3 Thermocouple (± 0.5℃ precision) Monitor exhaust temperature / overheating degree

[0057] Key experimental data

[0058] Working condition: ambient temperature -25℃, initial exhaust temperature 95℃

[0059] Control action Result change Energy efficiency improvement Open electromagnetic valve + first expansion valve opening degree 40% Exhaust temperature dropped to 82℃ (↓13℃) COP increased by 18% Venturi tube + mixing blade work together Overheating degree stabilized at 4.8℃ (fluctuation <0.3℃) Heating capacity +23% Close the air supplement (control group) Exhaust temperature rose to 105℃, heating capacity decayed by 35% COP decreased by 28%

[0060] (Heating COP is the core parameter for measuring the energy efficiency of heating equipment).

[0061] Pressure differential protection: when the high-low pressure differential > 0.55 MPa, the second expansion valve 8 is forced to close to prevent liquid hammering of the compressor 1.

[0062] Temperature linkage: when the oil temperature < 35℃, the crankcase heating band power is automatically increased (up to 200W) to ensure effective lubrication.

[0063] Through precise gas supplement control and mixture optimization, the two core problems of low-temperature heating attenuation and compressor 1 overheating are solved, and it is suitable for low-temperature environments above -15℃.

[0064] Among them, the economizer 3 control sets an economizer 3 pressure target value, and the opening degree control is performed through the second expansion valve 8, so that the liquid refrigerant is fully evaporated in the economizer 3. The baffle and wire mesh separator in the economizer 3 intercept the liquid refrigerant, the gaseous refrigerant enters the collector 6, and the liquid refrigerant enters the evaporator 4 through the second expansion valve 8 to complete the gas-liquid separation.

[0065] The pressure value of the economizer 3 is set to 0.2-0.5 MPa, and the opening degree control is performed through the second expansion valve 8. When the evaporator 4 temperature is -25℃, the opening degree increases from 15% to 30%, so that the liquid refrigerant is fully evaporated in the evaporator 4. The baffle and wire mesh separator in the economizer 3 intercept the liquid refrigerant, the gaseous refrigerant enters the collector 6, and the liquid refrigerant enters the evaporator 4 through the second expansion valve 8.

[0066] Evaporator 4 temperature at -25℃ and economizer 3 pressure correlation

[0067] The saturation pressure of the refrigerant corresponding to the target temperature of the evaporator 4 is about 0.1-0.2 MPa (specifically determined according to the type of refrigerant).

[0068] The pressure of the economizer 3 needs to be higher than the pressure of the evaporator 4 to form a throttling pressure differential, and it also needs to be controlled at 0.2-0.5 MPa through the opening degree adjustment of the second expansion valve 8. The opening degree is corrected in combination with the evaporator 4 outlet superheat or liquid level signal, with the economizer 3 pressure as the direct control target.

[0069] Economizer 3 real-time pressure through pressure sensor acquisition, compared with the target pressure 0.2-0.5MPa, using PID control algorithm to adjust the valve opening, and then the opening increases → flow increases → economizer 3 pressure rises, otherwise decreases.

[0070] Solve the problem: evaporator 4 outlet refrigerant dryness > 0.95 (conventional system < 0.85), liquid hammer failure rate decreases, two-stage throttling increases the "supercooling degree" of refrigerant 5-10℃, improves the heat exchange efficiency of evaporator 4 increases 10% ~ 15% heat absorption.

[0071] Among them, the pressure gradient control, after the jet enthalpy compressor 1 stops, when the high and low pressure side pressure difference > 1.5MPa, open the electromagnetic bypass valve, and then the high pressure side refrigerant slowly flows into the low pressure side through the capillary, and the pressure difference is reduced to < 0.3MPa in a time period to complete the pressure release.

[0072] After the jet enthalpy compressor 1 stops, when the high and low pressure side pressure difference > 1.5MPa, open the electromagnetic bypass valve, and then the high pressure side refrigerant slowly flows into the low pressure side through the capillary, and the pressure difference is reduced to < 0.3MPa in 55-65 seconds, the compressor 1 startup torque is reduced, the startup success rate is improved, the motor overload is avoided, and the compressor 1 life is prolonged.

[0073] Through the high pressure side pressure sensor, the range is 0-4MPa, the accuracy is ± 0.5%, and the low pressure side pressure sensor, the range is 0-2MPa, the accuracy is ± 0.5%, real-time monitoring of pressure difference.

[0074] If the ambient temperature < -15℃, the trigger threshold is reduced to 1.2MPa, the low temperature lubricating oil viscosity increases, which leads to the increase of starting resistance, and the temperature compensation is formed.

[0075] The pilot operated solenoid valve 9 has a response time < 10ms, a pressure resistance of 4MPa, and a diameter of Φ3mm. The capillary has an inner diameter of 0.8mm and a length of 1.2m.

[0076] Pressure relief rate control: the length of the capillary increases by 0.1m, and the pressure relief time is extended by 8-10 seconds (experimental verification data);

[0077] By adjusting the inner diameter of the capillary (0.6-1.2mm), different system capacities can be adapted, such as 10-30kW heat pump unit.

[0078] Stage pressure relief: first stage (0-30 seconds): fully open the electromagnetic valve 9, quickly release the high pressure side pressure;

[0079] Second stage (30-60 seconds): control the opening of the electromagnetic valve 9 by PWM (50% duty cycle) to prevent the sudden rise of the low pressure side pressure from causing the evaporator 4 to overload.

[0080] Experimental conditions and data

[0081] Compressor 1 Model: ZW series jet enhanced scroll compressor 1 (refrigerating capacity 20 kW, discharge capacity 80 m³ / h);

[0082] Refrigerant: R410A (charge 3.5 kg);

[0083] Environmental simulation cabin: adjustable from -30℃ to 20℃, humidity ≤60%;

[0084] Data acquisition system: sampling frequency 1 Hz5.

[0085] Test working conditions:

[0086] Low temperature working condition A: environmental temperature -25℃, condensing temperature 50℃, evaporation temperature -30℃;

[0087] Medium temperature working condition B: environmental temperature -10℃, condensing temperature 45℃, evaporation temperature -15℃;

[0088] High temperature working condition C: environmental temperature 0℃, condensing temperature 40℃, evaporation temperature -5℃.

[0089] Experimental data

[0090] Working condition Shutdown pressure difference (MPa) Pressure relief time (seconds) Final pressure difference (MPa) Compressor restart success rate A 1.8 62 0.25 100% (10 times in a row) B 1.6 58 0.28 100% (10 times in a row) C 1.3 53 0.22 100% (10 times in a row)

[0091] Comparative experiment without electromagnetic bypass valve:

[0092] Compressor 1 restart failure rate 30% under working condition A (motor locked due to high pressure difference);

[0093] Under working condition B, the first starting current exceeds the rated value by 150%, and the bearing wear rate increases by 20%.

[0094] Capillary parameter influence

[0095] Capillary inner diameter (mm) Pressure relief time (seconds) Pressure difference decay rate (MPa / s) 0.6 85 0.021 0.8 62 0.029 1.0 48 0.038

[0096] Reduce starting loss: pressure difference <0.3MPa after pressure relief, compressor starting current is reduced (compared with no control scheme);

[0097] Prolong the service life of the equipment: the bearing wear rate is reduced;

[0098] Adapt to extreme environment, still able to restart stably at -25℃ low temperature, heating decay rate ≤8% (conventional system decay rate >25%).

[0099] Among them, the temperature linkage control, when the environmental temperature < -10℃ and the oil temperature < 40℃, the heating band is turned on, the heating power is adjusted by PID algorithm to maintain the oil temperature 40±2℃ to complete the constant temperature control.

[0100] Active heating is provided by the crankcase heating belt at the bottom of the jet augmenting compressor; the oil temperature is monitored in real time by the internal oil temperature sensor; when the ambient temperature is < -10℃ and the oil temperature is < 40℃, the heating belt is turned on; the heating power is adjusted using the PID algorithm; when the oil temperature is 35℃, the power increases from 50W to 100W, maintaining the oil temperature at 40±2℃.

[0101] The crankcase heating belt at the bottom of the jet augmenting compressor is wrapped around the electric heating element on the compressor crankcase shell, directly heating the metal shell, and the heat is transferred to the internal lubricating oil through conduction and convection. Its control mode is on-off or power regulation control by the controller through solid-state relays or contactors.

[0102] The actual temperature of the lubricating oil in the crankcase is accurately measured by a temperature sensor, preferably installed in the oil pool or closely attached to the inner wall of the crankcase to accurately reflect the oil temperature (such as the oil temperature detection port reserved by the compressor manufacturer).

[0103] PID algorithm is the core control strategy to achieve constant oil temperature:

[0104] The PID controller calculates the control output (OP) to the heating belt based on the error e(t)=SP-PV) between the set value (SP=40℃) and the current oil temperature measurement value (PV=T_oil).

[0105] PID control law:

[0106]

[0107] Proportional term :

[0108] Effect: produces a control action proportional to the current error e(t), so the greater the error, the greater the heating power output (or the higher the duty cycle).

[0109] Influence: increasing Kp can speed up the system response, but too large can lead to overshoot and even oscillation, which is the basis of control response speed.

[0110] Integral term :

[0111] Effect: accumulates historical errors, as long as there is an error (even if it is very small), the integral term will continuously increase (or decrease) the output until the steady-state error is eliminated.

[0112] Influence: the key to eliminating system static error, increasing Ki can eliminate static error faster, but too large will cause integral saturation, leading to large overshoot and long-time oscillation, which is crucial to resist environmental heat dissipation, oil volume changes and other disturbances.

[0113] Derivative term :

[0114] Function: Predict the future error trend, adjust according to the error rate, reduce the heating power in advance when the oil temperature rises rapidly, increase the heating power in advance when the oil temperature drops rapidly, which plays a "damping" or "anticipation" role.

[0115] Influence: Suppress overshoot, improve system stability, improve dynamic response, increase damping effect by increasing Kd, but too large will amplify noise and be sensitive to measurement noise.

[0116] PID output processing and control execution:

[0117] Output limiting: OP calculation results will be limited to the effective range (such as 0%~100%), 0% represents completely closing the heating band, and 100% represents full power heating.

[0118] Execution mode:

[0119] Time proportion control (PWM): Controller output PWM signal drives SSR, OP value corresponds to PWM duty cycle (DutyCycle).

[0120] For example, OP=50% means that in a fixed period (such as 2 seconds), the heating band is powered on for 1 second and off for 1 second. The above is the smoothest and most precise control method.

[0121] Bit control (ON / OFF): When OP> threshold (such as 50%), SSR (solid state relay) is fully on (100%); when OP< threshold, SSR is completely off (0%). This method is simple but rough control, which will produce large fluctuations (±2℃) around the set value, not recommended for high-precision ±2℃ control.

[0122] System control is not only a simple PID constant temperature, but also needs to judge when to start heating according to the ambient temperature (T_amb) and set the upper limit of heating intensity (protect the compressor).

[0123] It should be noted that only when the ambient temperature is extremely low (<-10℃) and the oil temperature does not meet the standard (<40℃), the crankcase heating band is allowed to start work.

[0124] When the start condition is met, the set value SP of the PID controller is fixed at 40℃.

[0125] PID algorithm works continuously, calculates the required heating power (OP) according to the difference between actual oil temperature T_oil and 40℃, and drives the heating band through PWM, the goal is to accurately maintain T_oil=40±2℃.

[0126] Environmental temperature limit on heating power upper limit (protection mechanism):

[0127] Problem: The heating band needs to run at full power in extremely low ambient temperatures, but if the ambient temperature rises (e.g., >-5°C) and the oil temperature is still low (still needs heating), full power heating may cause the oil temperature to rise too fast or eventually exceed the upper limit (>42°C).

[0128] Solution: Introduce the ambient temperature T_amb to dynamically constrain the maximum output limit value (OP_max) of the PID.

[0129] Establish a functional relationship (linear or piecewise linear) between T_amb and OP_max.

[0130] Principle: The lower the T_amb, the greater the maximum heating power allowed (OP_max is higher, such as 100%); the higher the T_amb (but still meets the start condition), the smaller the maximum heating power allowed (OP_max is lower, such as 60%, 40%).

[0131] Formula example:

[0132]

[0133] T_min: The lowest ambient temperature supported by the system design (e.g., -30°C)

[0134] k: Slope, determined according to the system thermal characteristics (e.g., k=4% / °C, i.e., for every 1°C increase in ambient temperature, the maximum heating power limit decreases by 4%).

[0135] Effect: While ensuring sufficient heating capacity at low temperatures, it prevents excessive heating when the ambient temperature is relatively high (but still below -10°C), avoiding oil temperature exceeding the standard and protecting the compressor. The OP output value calculated by the PID will not exceed the OP_max corresponding to the ambient temperature.

[0136] Stop condition:

[0137] When T_oil (oil) ≥ 42°C (reaches the temperature upper limit) or T_amb ≥ -10°C (ambient conditions no longer meet), immediately stop the heating band work (OP=0%).

[0138] When T_oil drops to ≤38°C due to environmental heat dissipation, and T_amb <-10°C, restart the PID heating control.

[0139] In different constant low temperature environments (e.g., -25°C, -20°C, -15°C), key parameters also need to be adjusted and system debugged.

[0140] The viscosity of the lubricating oil can be reduced to below 100 cP (optimal lubrication range), reducing bearing wear (from 0.05 mm / 1000 hours to 0.02 mm / 1000 hours);

[0141] Low temperature start, good lubricating oil flow, compressor noise reduction.

[0142] The above four control modes are completed by the controller through the multi-sensor linkage of the cooperative control system.

[0143] The cooperative control system can also complete:

[0144] In the defrosting cycle, when the evaporator 4 is frosted, the controller closes the air supplement solenoid valve 9, switches the four-way valve to reverse defrosting, and melts the frost layer using the exhaust heat of the compressor 1.

[0145] In high load operation, when the compressor 1 current > rated value 90%, the controller reduces the compressor 1 frequency, and at the same time, reduces the double expansion valve opening degree, so that the refrigerant flow is reduced synchronously.

[0146] When the ambient temperature fluctuates, when the ambient temperature rises by 8-12℃, the controller reduces the opening degree of the first expansion valve 7 to reduce the air supplement amount, so as to maintain the heating capacity and load matching.

[0147] The above shows and describes the basic principles and main features of the present application and the advantages of the present application. For those skilled in the art, it is obvious that the present application is not limited to the details of the above exemplary embodiments, and the present application can be realized in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting, and the scope of the present application is defined by the appended claims rather than the above description, and therefore all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present application, and any reference signs in the claims should not be regarded as limiting the claims.

[0148] Although embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A high-efficiency heating control device based on low-temperature vapor injection enthalpy enhancement, comprising a vapor injection enthalpy enhancement compressor (1), an evaporator (4), a condenser (2), and an economizer (3), wherein the vapor injection enthalpy enhancement compressor (1) sends gaseous and liquid refrigerant into the condenser (2) through a pipeline, the condenser (2) sends gaseous and liquid refrigerant into the economizer (3) through a pipeline, and the economizer (3) sends gaseous and liquid refrigerant into the evaporator (4) through a pipeline, characterized in that: The steam generator connects steam and liquid to the collector (6) and compressor (1) respectively through a gas-liquid separator (5); The jet enthalpy compressor (1) is equipped with a gas injection port, which injects medium-pressure steam formed by the medium-pressure airflow of the economizer (3) combined with the steam of the evaporator (4) during the compression process of the jet enthalpy compressor (1); The medium-pressure airflow of the economizer (3) and the steam of the evaporator (4) are mixed in the collector (6). A solenoid valve (9) is installed between the economizer (3) and the collector (6). A first expansion valve (7) is installed on the pipe connecting the condenser (2) and the economizer (3). A second expansion valve (8) is installed on the pipe connecting the economizer (3) and the evaporator (4). Collaborative control system: The collaborative control system enables multi-sensor linkage through the controller.

2. The high-efficiency heating control device based on low-temperature jet enthalpy enhancement according to claim 1, characterized in that: The collector (6) is tapered at the end facing the compressor (1) and is connected to a venturi tube (63). An agitator (62) is installed inside the collector (6), and an annular body (61) is installed inside the collector (6). The agitator (62) is connected to the middle of the annular body (61) via a bearing.

3. The high-efficiency heating control device based on low-temperature jet enthalpy enhancement according to claim 2, characterized in that: In the gas replenishment control, when the ambient temperature is <-10℃ and the compressor (1) exhaust temperature is >90℃, the solenoid valve (9) is opened to regulate the flow rate, the target value of superheat is set, and the refrigerant flow rate in the economizer (3) is controlled by the opening degree of the first expansion valve (7) to generate medium-pressure vapor; then the mixing optimization is carried out, the airflow is accelerated by the venturi tube (63) of the collector (6), and the droplets are dispersed by the agitator (62).

4. The high-efficiency heating control method based on low-temperature jet enthalpy enhancement according to claim 2, characterized in that: Economizer (3) control: Set a target pressure value for economizer (3) and control the opening degree through the second expansion valve (8) so that the liquid refrigerant can fully evaporate in the economizer (3). The baffle and wire mesh separator in the economizer (3) intercept the liquid refrigerant, and the gaseous refrigerant enters the collector (6). The liquid refrigerant enters the evaporator (4) through the second expansion valve (8) to complete the gas-liquid separation.

5. The high-efficiency heating control method based on low-temperature jet enthalpy enhancement according to claim 2, characterized in that: Pressure gradient control: After the jet enthalpy compressor (1) stops, when the pressure difference between the high and low pressure sides is >1.5MPa, the electromagnetic bypass valve is opened, and the refrigerant on the high pressure side slowly flows into the low pressure side through the capillary tube, reducing the pressure difference to <0.3MPa within a time period to complete the pressure release.

6. The high-efficiency heating control method based on low-temperature jet enthalpy enhancement according to claim 2, characterized in that: Temperature linkage control: When the ambient temperature is <-10℃ and the oil temperature is <40℃, the heating belt is turned on, and the heating power is adjusted by PID algorithm to maintain the oil temperature at 40±2℃ to complete constant temperature control.

7. A high-efficiency heating control method based on low-temperature jet enthalpy enhancement, and a high-efficiency heating control device based on low-temperature jet enthalpy enhancement according to claims 1-6, characterized in that: S1: The refrigerant liquid and vapor are sent to the condenser (2), economizer (3) and evaporator (4) in sequence through the pipeline by the jet enthalpy compressor (1). The liquid and vapor are separated by the gas-liquid separator (5) of the evaporator (4), and the vaporizer sends the liquid back to the jet enthalpy compressor (1). S2: Steam is sent into collector (6) by gas-liquid separator (5), and medium-pressure steam from economizer (3) is sent into collector (6) simultaneously through solenoid valve (9). The two streams of steam mix in collector (6) and are sent into the air supply port of compressor (1) through venturi tube (63). S3: Gas replenishment control, the gas replenishment from economizer (3) to collector (6) is controlled by solenoid valve (9), the refrigerant flow rate entering economizer (3) is regulated by first electronic expansion valve, the medium-pressure steam in economizer (3) and steam in evaporator (4) are mixed by collector (6) to generate pure gaseous medium-pressure steam, when the ambient temperature is <-10℃ and the exhaust temperature of compressor (1) is >90℃, solenoid valve (9) is opened to regulate the flow rate to set the superheat at 5-8℃, the refrigerant flow rate in economizer (3) is controlled by the opening degree of first expansion valve (7), when the ambient temperature is -20℃, the opening degree is increased from 20% to 40% to make the medium-pressure steam reach 0.5-1.0MPa, the airflow is accelerated by venturi tube (63) of collector (6), and the agitator (62) disperses the droplets to make the steam dryness >0.98; S4: Economizer (3) control, the refrigerant flow rate from the economizer (3) to the evaporator (4) is adjusted by the second electronic expansion valve. The gaseous refrigerant output by the economizer (3) is sent to the gas supply control, and the liquid refrigerant is sent to the evaporator (4). The pressure value of the economizer (3) is kept at 0.2-0.5MPa. The opening degree of the second expansion valve (8) is controlled. When the temperature of the evaporator (4) is -25℃, the opening degree is increased from 15% to 30%, so that the liquid refrigerant can be fully evaporated in the evaporator (4). The baffle and wire mesh separator in the economizer (3) intercept the liquid refrigerant. The gaseous refrigerant enters the collector (6), and the liquid refrigerant enters the evaporator (4) through the second expansion valve (8). S5: Pressure gradient control. After the jet enthalpy compressor (1) stops, when the pressure difference between the high and low pressure sides is >1.5MPa, the electromagnetic bypass valve is opened, and the refrigerant on the high pressure side slowly flows into the low pressure side through the capillary tube, reducing the pressure difference to <0.3MPa within 55 to 65 seconds. S6: Temperature linkage control, active heating is provided by the crankcase heating belt at the bottom of the jet enthalpy compressor (1); the oil temperature is monitored in real time by the internal oil temperature sensor, and the heating belt is turned on when the ambient temperature is <-10℃ and the oil temperature is <40℃; the heating power is adjusted by PID algorithm, and the power is increased from 50W to 100W when the oil temperature is 35℃, maintaining the oil temperature at 40±2℃; S7: The four control methods in S3-S6 are completed through the controller of the collaborative control system to achieve multi-sensor linkage; During the defrosting cycle, when the evaporator (4) is frosted, the controller closes the gas supply solenoid valve (9) and switches the four-way valve to defrost in reverse, using the heat from the compressor (1) to melt the frost layer. During high-load operation, when the compressor (1) current is greater than 90% of the rated value, the controller reduces the compressor (1) frequency and simultaneously reduces the opening of the dual expansion valve, so that the refrigerant flow rate decreases synchronously. When the ambient temperature fluctuates, when the ambient temperature rises by 8-12℃, the controller reduces the opening of the first expansion valve (7) to reduce the amount of supplementary air, so as to maintain the matching of heating capacity with load.

Images