CN114777345B

CN114777345B - Refrigerating apparatus

Info

Publication number: CN114777345B
Application number: CN202210414896.2A
Authority: CN
Inventors: 王锡元; 丛辉; 李磊
Original assignee: Qingdao Hisense Hitachi Air Conditioning System Co Ltd
Current assignee: Qingdao Hisense Hitachi Air Conditioning System Co Ltd
Priority date: 2022-04-20
Filing date: 2022-04-20
Publication date: 2023-05-30
Anticipated expiration: 2042-04-20
Also published as: CN114777345A

Abstract

The refrigeration equipment comprises: a first refrigerant circuit in which the refrigerant circulates through the first compressor, the condenser, the throttle device, and the evaporator; the discharge end of the first compressor is connected to the suction end via a first switching pipeline provided with a first valve; a second refrigerant loop for circulating the refrigerant through the second compressor, the condenser, the throttling device and the evaporator; the exhaust end of the second compressor is connected with the suction end through a second switching pipeline provided with a second valve; the controller is used for switching the second valve to be opened and guiding the refrigerant in the second switching pipeline to exchange heat with the low-temperature external working medium and then return to the air suction end when the first valve is closed and the second compressor starting instruction is received; or when the second compressor works and the second valve is closed and a first compressor starting instruction is received, the first valve is switched to be opened and guides the refrigerant in the first switching pipeline to exchange heat with the low-temperature external working medium and then return to the air suction end; therefore, the surge and high-temperature alarm of the compressor can be avoided simultaneously.

Description

Refrigerating apparatus

Technical Field

The invention relates to the technical field of refrigeration, in particular to refrigeration equipment.

Background

The centrifugal machine set is widely applied to various refrigeration equipment by virtue of the advantages of high efficiency, reliable operation, low noise and the like, and the multi-head water chilling unit is a common centrifugal machine set. Taking a double-head chiller as an example, two centrifugal compressors are arranged in the double-head chiller, and each compressor and other components (including a condenser, an evaporator and a throttling device) form a refrigerant loop. When the gaseous refrigerant flows through the impeller of the centrifugal compressor, the impeller running at high speed makes the gas under the action of centrifugal force, on the one hand, the pressure is improved, and on the other hand, the speed is also greatly increased. The centrifugal compressor firstly converts mechanical energy of a prime motor into static pressure energy and kinetic energy of a gas refrigerant through an impeller. After that, the gaseous refrigerant flows through the passage of the diffuser again, and as the flow passage section is gradually increased when the gaseous refrigerant flows through the passage of the diffuser, the flow velocity of the gas molecules at the tail end is reduced, and the gas molecules at the front end continuously flow forward, so that most of kinetic energy of the gas is converted into static pressure energy, and the supercharging effect is further realized.

The compressors in the multi-head chiller are not running synchronously. In order to avoid surging, the post-start centrifugal compressor generally directs refrigerant from the discharge port of the compressor directly back to the suction port of the compressor through a conduit, so that the suction-discharge pressure ratio is small and the corresponding surging rotation speed is small for the post-start centrifugal compressor. Therefore, the rotating speed is not lower than the surge rotating speed all the time in the process that the centrifugal compressor is started to reach the target rotating speed after that, and the surge is effectively avoided. However, in this process, the suction superheat may be too high, resulting in a system alarm problem.

Disclosure of Invention

The invention proposes a refrigeration device comprising: a first refrigerant circuit for circulating the refrigerant sequentially through the first compressor, the condenser, the throttle device and the evaporator; the exhaust end of the first compressor is connected with the air suction end of the first compressor through a first switching pipeline, and a first valve is arranged on the first switching pipeline; a second refrigerant loop for circulating the refrigerant sequentially through the second compressor, the condenser, the throttling device and the evaporator; the exhaust end of the second compressor is connected with the air suction end of the second compressor through a second switching pipeline, and a second valve is arranged on the second switching pipeline; the controller is used for controlling the second valve to be switched from being closed to being opened and guiding the refrigerant in the second switching pipeline to exchange heat with the low-temperature external working medium first and then return to the air suction end of the second compressor under the condition that the first compressor works and the first valve is closed and a second compressor starting instruction is received; or when the second compressor works and the second valve is closed and the first compressor starting instruction is received, the first valve is switched from closed to open and the refrigerant in the first switching pipeline is led to exchange heat with the low-temperature external working medium and then returns to the air suction end of the first compressor.

In some embodiments of the present application, the evaporator is connected to the condenser via a first heat exchange line, and a first expansion valve is disposed on the first heat exchange line; the evaporator is connected to the condenser through a second heat exchange pipeline, and a second expansion valve is arranged on the second heat exchange pipeline; when the first compressor works, the first valve is closed, after receiving a second compressor starting instruction and the second expansion valve is switched to a second target opening degree from closing, the controller controls the second valve to be switched to opening from closing and guides the refrigerant in the second switching pipeline to exchange heat with the refrigerant in the second heat exchange pipeline first and then return to the air suction end of the second compressor; or when the second compressor works, the second valve is closed, after receiving a first compressor starting instruction and the first expansion valve is switched to the first target opening degree from closing, the controller controls the first valve to be switched to opening from closing and guides the refrigerant in the first switching pipeline to exchange heat with the refrigerant in the first heat exchange pipeline first and then return to the air suction end of the first compressor.

In some embodiments of the present application, when the first compressor is in operation, the first valve is closed, a second compressor start command is received, and when the first compressor discharge temperature is higher than a set discharge temperature threshold, the controller controls the second expansion valve to switch from closed to open, and controls the second expansion valve to maintain at a second target opening; under the condition that the system pressure ratio of the first compressor is higher than a set pressure ratio threshold value and the second expansion valve is kept at a second target opening degree, the controller controls the second valve to be switched from closed to open, and guides the refrigerant in the second switching pipeline to exchange heat with the refrigerant in the second heat exchange pipeline and then return to the suction end of the second compressor; or when the second compressor works and the second valve is closed, the controller controls the first expansion valve to be switched from closed to open and controls the first expansion valve to be kept at a first target opening degree under the condition that the starting instruction of the first compressor is received and the exhaust temperature of the second compressor is higher than a set exhaust temperature threshold value; and under the condition that the system pressure ratio of the second compressor is higher than a set pressure ratio threshold value and the first expansion valve is kept at a first target opening, the controller controls the first valve to be switched from closed to open, and guides the refrigerant in the first switching pipeline to exchange heat with the refrigerant in the first heat exchange pipeline and then return to the suction end of the first compressor.

In some embodiments of the present application, when the first compressor is in operation, the first valve is closed, a second compressor start command is received, and when the first compressor discharge temperature is below a set discharge temperature threshold and the first compressor suction temperature is above a set suction temperature threshold, the controller controls the second expansion valve to switch from closed to open, and controls the second expansion valve to remain at a second target opening; under the condition that the system pressure ratio of the first compressor is higher than a set pressure ratio threshold value and the second expansion valve is kept at a second target opening degree, the controller controls the second valve to be switched from closed to open, and guides the refrigerant in the second switching pipeline to exchange heat with the refrigerant in the second heat exchange pipeline and then return to the suction end of the second compressor; or when the second compressor works, the second valve is closed, a first compressor starting instruction is received, and when the exhaust temperature of the second compressor is lower than a set exhaust temperature threshold value and the suction temperature of the second compressor is higher than a set suction temperature threshold value, the controller controls the first expansion valve to be switched from being closed to being opened, and controls the first expansion valve to be kept at a first target opening; and under the condition that the system pressure ratio of the second compressor is higher than a set pressure ratio threshold value and the first expansion valve is kept at a first target opening, the controller controls the first valve to be switched from closed to open, and guides the refrigerant in the first switching pipeline to exchange heat with the refrigerant in the first heat exchange pipeline and then return to the suction end of the first compressor.

In some embodiments of the present application, the controller controls the second valve to switch from open to closed after the second compressor reaches the set rotational speed; or the controller controls the first valve to switch from opening to closing after the first compressor reaches the set rotating speed.

In some embodiments of the present application, the controller controls the second valve to switch from open to closed after the second compressor reaches the set rotational speed, and switches the second expansion valve from the second target opening to closed after the second valve is closed; or the controller controls the first valve to switch from opening to closing after the first compressor reaches the set rotating speed, and switches the first expansion valve from the first target opening to closing after the first valve is closed.

In some embodiments of the present application, when the first compressor works, the first valve is closed, the second valve is controlled to switch from closing to opening and guide the refrigerant in the second switching pipeline to exchange heat with the external working medium before returning to the suction end of the second compressor when the first valve receives the start command of the second compressor and the system pressure ratio of the first compressor is higher than the set pressure ratio threshold; when the first compressor works, the first valve is closed, a second compressor starting instruction is received, and the system pressure ratio of the first compressor is lower than a set pressure ratio threshold value, the second valve is kept closed, and the second compressor is started; or the controller controls the first valve to be switched from being closed to be opened and guides the refrigerant in the first switching pipeline to exchange heat with external working medium firstly and then return to the air suction end of the first compressor when the second compressor works and the second valve is closed, the starting instruction of the first compressor is received, and the system pressure ratio of the second compressor is higher than a set pressure ratio threshold value; and when the second compressor works, the second valve is closed, the first compressor is started after receiving the first compressor starting command, and the system pressure ratio of the second compressor is lower than the set pressure ratio threshold value, the first valve is kept closed, and the first compressor is started.

In some embodiments of the present application, further comprising: the first fan is arranged corresponding to the first switching pipeline; the second fan is arranged corresponding to the second switching pipeline; when the first compressor works and the first valve is closed and a second compressor starting instruction is received, the controller controls the second valve to be switched from closed to open, the second fan starts to work, and the refrigerant in the second switching pipeline is led to exchange heat with air firstly and then returns to the air suction end of the second compressor; or when the second compressor works and the second valve is closed and the first compressor starting instruction is received, the controller controls the first valve to be switched from closed to open, the first fan starts to work, and the refrigerant in the second switching pipeline is guided to exchange heat with air first and then returns to the air suction end of the first compressor.

In some embodiments of the present application, the controller controls the second valve to switch from open to closed after the second compressor is started, and controls the second fan to close after a predetermined time has elapsed since the second valve stopped; or the controller controls the first valve to switch from opening to closing after the first compressor is started, and controls the first fan to be closed after a preset time from stopping the first valve.

In some embodiments of the present application, further comprising: the first water cooling pipeline is arranged corresponding to the first switching pipeline; the second water-cooling pipeline is arranged corresponding to the second switching pipeline; when the first compressor works and the first valve is closed and a second compressor starting instruction is received, the controller controls the second valve to be switched from closed to open, and the refrigerant in the second switching pipeline is led to exchange heat with water in the second water cooling pipeline and then returns to the air suction end of the second compressor; when the second compressor works and the second valve is closed and a first compressor starting instruction is received, the controller controls the first valve to be switched from closed to open, and the refrigerant in the first switching pipeline is led to exchange heat with water in the first water cooling pipeline and then returns to the air suction end of the first compressor.

The invention can effectively avoid the abnormal states of compressor surge and high-temperature alarm at the same time.

Drawings

Fig. 1 is a schematic configuration view of a refrigeration cycle of a first embodiment of a refrigeration apparatus;

FIG. 2 is a schematic diagram of valve control when the refrigeration appliance of FIG. 1 switches a second compressor;

FIG. 3 is a schematic view of valve control when the refrigeration appliance of FIG. 1 switches the first compressor;

Fig. 4 is a schematic structural view of a refrigeration cycle of a second embodiment of the refrigeration apparatus;

FIG. 5 is a schematic diagram of valve control when the refrigeration appliance of FIG. 4 switches the second compressor;

FIG. 6 is a schematic diagram of valve control when the refrigeration appliance of FIG. 4 switches the first compressor;

fig. 7 is a schematic view of a refrigeration cycle of a third embodiment of a refrigeration apparatus;

FIG. 8 is a schematic diagram of valve control when the refrigeration appliance of FIG. 7 switches the second compressor;

FIG. 9 is a schematic view of valve control when the refrigeration appliance of FIG. 7 switches the first compressor;

fig. 10 is a control flow diagram of a refrigeration appliance.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by one of ordinary skill in the art without undue burden on the person of ordinary skill in the art based on the embodiments of the present invention, are intended to be within the scope of the present application.

In the description of the present application, it should be understood that the terms "center," "upper," "lower," "front," "rear," "top," "bottom," "inner," "outer," and the like indicate orientations or positional relationships based on the orientation or positional relationships shown in the drawings, merely to facilitate description of the present application and simplify the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be configured and operated in a particular orientation, and therefore should not be construed as limiting the present application.

In the description of the present application, it should be understood that the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or an implicit indication of the number of technical features being indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present application, unless otherwise indicated, the meaning of "a plurality" is two or more.

In the description of the present application, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the terms in this application will be understood by those of ordinary skill in the art in a specific context.

First, a refrigeration apparatus according to a first embodiment of the present invention will be described with reference to fig. 1 to 3, and fig. 10. Fig. 1 is a schematic configuration diagram of a refrigeration cycle of a first embodiment of a refrigeration apparatus. The refrigeration apparatus shown in fig. 1 is a double-head chiller including a first compressor 11 and a second compressor 21. More specifically, the double head chiller includes a first refrigerant circuit in which the refrigerant circulates through the first compressor 11, the condenser 12, the throttle device 13, and the evaporator 14 in this order, and a second refrigerant circuit in which the refrigerant circulates through the second compressor 21, the condenser 12, the throttle device 13, and the evaporator 14 in this order. The first compressor 11 and the second compressor 21 are independent from each other, i.e., a refrigeration (heating) cycle of the chiller is performed by using the first compressor 11, the condenser 12, the throttle device 13, and the evaporator 14; or by performing a cooling (heating) cycle of the chiller by using the second compressor 21, the condenser 12, the throttle device 13 and the evaporator 14; or simultaneously executing the refrigeration (heating) cycle of the water chiller through the first refrigerant loop and the second refrigerant loop. The refrigeration (heating) cycle includes a series of processes involving compression, condensation, expansion and evaporation, and further uses water to cool or heat an indoor space.

The first compressor 11 and/or the second compressor 21 compress the low-temperature low-pressure refrigerant into a high-temperature high-pressure refrigerant gas and discharge the compressed refrigerant gas. The discharged refrigerant gas flows into the condenser 12. The condenser 12 condenses the compressed refrigerant into a liquid phase, and heat is released to the surrounding environment through the condensation process. This heat is absorbed by the cooling water in the cooling water line near the condenser 12 (cooling water inlet is shown as w2_in in fig. 1, cooling water outlet is shown as w2_out in fig. 1), and further sent to the outdoor cooling tower via the cooling water, and finally released to the ambient air. After heat exchange with the ambient air, the cooling water with reduced temperature flows out of the cooling tower and is returned to the cooling water pipeline for the next cycle.

The expansion device 13 expands the liquid-phase refrigerant in a high-temperature and high-pressure state condensed in the condenser 12 into a low-pressure liquid-phase refrigerant.

The evaporator 14 evaporates the refrigerant expanded in the throttle device 13 and returns the refrigerant gas in a low-temperature and low-pressure state to the compressor. The evaporator 14 can bring the chilled water to a lower temperature by absorbing heat of the chilled water in the nearby chilled water piping (chilled water inlet shown as w1_in in fig. 1 and chilled water outlet shown as w1_out in fig. 1) by using the latent heat of evaporation of the refrigerant. The low-temperature chilled water is further subjected to heat exchange with indoor air, takes away heat in a room or space, and finally returns to the water return pipeline. The heat exchange between the chilled water and the indoor air is driven by the indoor fan, the indoor fan blows the air through the chilled water pipeline, the indoor air temperature is reduced, and the indoor heat exchange is accelerated.

In the whole cycle, the water chiller can adjust the temperature of the indoor space.

In other embodiments of the present invention, the refrigeration apparatus may also be a multi-head chiller, including the first compressor 11, the second compressor 21, …, and the nth compressor. More specifically, the multi-head chiller includes a first refrigerant circuit, a second refrigerant circuit …, and an nth refrigerant circuit in which the refrigerants circulate in order. The first compressor 11 and the second compressor 21 and … are independent of each other.

Taking a double-head chiller as an example, the exhaust end of the first compressor 11 is connected to the intake end of the first compressor 11 via a first switching pipeline 15, and a first valve 16 is provided on the first switching pipeline 15. The discharge end of the second compressor 21 is connected to the suction end of the second compressor 21 via a second switching pipe 25, and a second valve 26 is provided in the second switching pipe 25. The first valve 16 and the second valve 26 are controlled by a controller. The controller includes a microprocessor and a memory, and is capable of controlling the first compressor 11, the second compressor 21, the throttle device 13, the first valve 16, and the second valve 26 in accordance with a program or the like stored in the memory.

A non-return valve 24 is arranged between the first switching pipeline 15 and the condenser 12, and a non-return valve 23 is arranged between the second switching pipeline 25 and the condenser 12.

The controller is configured to control the second valve 26 to switch from closed to open and guide the refrigerant in the second switching pipe 25 to return to the suction end of the second compressor 21 after heat exchange with the external working medium when the first compressor 11 is operated and the first valve 16 is closed while receiving a start command of the second compressor 21. When the first compressor 11 is operated and the first valve 16 is closed, the controller determines that the first compressor 11 is in a normal operation state, and the ratio of suction and discharge pressures of the first compressor 11 (hereinafter referred to as a pressure ratio) is measurable. After the first compressor 11 enters a normal operation state, the load of the refrigeration equipment increases, the second compressor 21 is started and is lifted to a target rotating speed according to a preset program, the controller receives a starting instruction of the second compressor 21, controls the second valve 26 to be switched from being closed to being opened and guides the refrigerant in the second switching pipeline 25 to exchange heat with the low-temperature external working medium first and then return to the air suction end of the second compressor 21. In the process of starting the second compressor 21 to the target rotating speed, when the controller receives a starting instruction of the second compressor 21, namely, controls the second valve 26 to be switched from closed to open, simultaneously guides the refrigerant in the second switching pipeline 25 to exchange heat with the low-temperature external working medium and then return to the air suction end of the second compressor 21, and because the pipeline resistance of the second switching pipeline 25 is small, the refrigerant with the reduced temperature in the second switching pipeline 25 returns to the air suction end of the second compressor 21 in a state of very close pressure and low temperature, on one hand, the air suction pressure and the air discharge pressure of the second compressor 21 are very close, and the pressure ratio is in a very low state; because the pressure ratio is in a very low state, the corresponding surge rotation speed is very small, and in the process of increasing the rotation speed of the second compressor 21, the actual rotation speed is ensured to be higher than the surge rotation speed corresponding to the pressure ratio, so that the surge of the second compressor 21 is effectively avoided; on the other hand, if the evaporating temperature is higher or the time interval from the last stop of the second compressor 21 is shorter and is in a thermal state, the refrigerant with lower temperature in the second switching pipeline 25 can avoid the secondary rise of the refrigerant temperature at the suction end of the second compressor 21, so that the suction superheat is too high, and the overheat of the second compressor 21 is too high to alarm; and the alarm of the too high exhaust temperature of the second compressor 21 caused by the too high suction superheat degree can be avoided.

Correspondingly, the controller is configured to control the first valve 16 to switch from closed to open and guide the refrigerant in the first switching pipeline 15 to exchange heat with the external working medium first and then return to the suction end of the first compressor 11 when the second compressor 21 is operated and the second valve 26 is closed and simultaneously the start command of the first compressor 11 is received. When the second compressor 21 is operated and the second valve 26 is closed, the controller determines that the second compressor 21 is in a normal operation state, and the pressure ratio of the second compressor 21 is measurable. After the second compressor 21 enters the normal operation state, the load of the refrigeration equipment increases, the first compressor 11 is started and is lifted and works at the target rotating speed according to the preset program, the controller receives the starting instruction of the first compressor 11, controls the first valve 16 to be switched from being closed to being opened and guides the refrigerant in the first switching pipeline 15 to exchange heat with the low-temperature external working medium first and then return to the air suction end of the first compressor 11. In the process of starting the first compressor 11 to the target rotating speed, when the controller receives a starting instruction of the first compressor 11, namely, controls the first valve 16 to be switched from closed to open, simultaneously guides the refrigerant in the first switching pipeline 15 to exchange heat with low-temperature external working medium and then return to the air suction end of the first compressor 11, and because the pipeline resistance of the first switching pipeline 15 is small, the refrigerant with reduced temperature in the first switching pipeline 15 returns to the air suction end of the first compressor 11 in a state of very close pressure and low temperature, on one hand, the air suction pressure and the air discharge pressure of the first compressor 11 are very close, and the pressure ratio is in a very low state; because the pressure ratio is in a very low state, the corresponding surge rotating speed is very small, and the actual rotating speed is higher than the surge rotating speed corresponding to the real-time pressure ratio in the process of increasing the rotating speed of the first compressor 11 to the target rotating speed by self-starting, so that the surge of the first compressor 11 is effectively avoided; on the other hand, if the evaporating temperature is higher or the time interval from the last stop of the first compressor 11 is shorter and is in a thermal state, the refrigerant with lower temperature in the first switching pipeline 15 can avoid the secondary rise of the refrigerant temperature at the suction end of the first compressor 11, so that the suction superheat degree is too high, and the overheat degree of the first compressor 11 is alarmed; and the alarm of the too high exhaust temperature of the first compressor 11 caused by the too high suction superheat degree can be avoided. Switching from closed to open of the first valve 16 and the second valve 26 may be understood as switching from closed to open, for example, a valve open state corresponding to a set of level signals, or switching from a minimum to a maximum opening.

The process of heat exchange between the refrigerant in the first switching pipe 15 or the second switching pipe 25 and the low-temperature external working medium will be described below. Referring to fig. 1 to 3, the evaporator 14 is connected to the condenser 12 via a first heat exchange line 18, and a first expansion valve 19 is provided on the first heat exchange line 18. The evaporator 14 is simultaneously connected to the condenser 12 via a second heat exchange line 28, the second heat exchange line 28 being provided with a second expansion valve 29.

After the first compressor 11 is operated and the first valve 16 is closed and the second compressor 21 is started and the second expansion valve 29 is switched from closed to open to a second target opening, the controller controls the second valve 26 to switch from closed to open and guides the refrigerant in the second switching pipeline 25 to exchange heat with the refrigerant in the second heat exchange pipeline 28 and return to the suction end of the second compressor 21. When the first compressor 11 is operated, the first refrigerant circuit (as indicated by an arrow F1 in fig. 2) is operated, a pressure difference exists between the evaporator 14 and the condenser 12, and after the second expansion valve 29 is controlled to switch from the closed state to the second target opening degree, the second expansion valve 29 plays a role in throttling. The second expansion valve 29 expands the liquid-phase refrigerant in a high temperature and high pressure state condensed in the condenser 12 into a low pressure liquid-phase refrigerant and returns the low pressure liquid-phase refrigerant to the evaporator 14 through the second heat exchange line 28 (as indicated by an arrow F4 in fig. 2), and the controller controls the second valve 26 to switch from closed to open and directs the refrigerant in the second switching line 25 to exchange heat with the refrigerant in the second heat exchange line 28 that has been cooled down before returning the refrigerant to the suction end of the second compressor 21 (as indicated by an arrow F3 in fig. 2). In an alternative embodiment, a portion of the second switching line 25 (shown as 27) and the second heat exchange line 28 may be integrated into a single fluorine-cooled heat exchanger 30. The fluorine cold heat exchanger 30 is optionally disposed upstream or downstream of the second valve 26.

Correspondingly, after the second compressor 21 works and the second valve 26 is closed, and the first compressor 11 is started and the first expansion valve 19 is switched from being closed to a first target opening degree, the controller controls the first valve 16 to be switched from being closed to being opened and guides the refrigerant in the first switching pipeline 15 to exchange heat with the refrigerant in the first heat exchange pipeline 18 first and then return to the suction end of the first compressor 11. When the second compressor 21 is operated, the second refrigerant circuit (as indicated by an arrow F2 in fig. 3) is operated, and a pressure difference is also present between the evaporator 14 and the condenser 12, so that the first expansion valve 19 is controlled to switch from the closed state to the first target opening degree, and then the first expansion valve 19 plays a role in throttling. The first expansion valve 19 expands the liquid-phase refrigerant in a high temperature and high pressure state condensed in the condenser 12 into a low pressure liquid-phase refrigerant and returns the low pressure liquid-phase refrigerant to the evaporator 14 through the first heat exchange line 18, and the controller controls the first valve 16 to switch from closed to open and guides the refrigerant in the first switching line 15 to exchange heat with the cooled refrigerant in the first heat exchange line 18 and return the cooled refrigerant to the suction end of the first compressor 11. In an alternative embodiment, the first switching line 15 and the first heat exchange line 18 may be integrated in a single fluorine-cooled heat exchanger 20 (as shown at 17). The fluorine cold heat exchanger 20 is optionally disposed either upstream or downstream of the first valve 16.

A specific flow chart of the controller is given in fig. 10. As shown in the figure, in the above control, the controller performs the following specific steps.

If both the first compressor and the second compressor are in a shutdown state, then the respective input/output ports remain waiting and are monitored.

If one of the first compressor and the second compressor is in an operating state, the first compressor is in an operating state, for example, the second compressor is to be started, for example, the controller performs the steps as in fig. 10.

It is determined whether a second compressor start command is received.

If a second compressor start command is received, it is further determined whether the first valve is in a closed state.

And if the second compressor starting instruction is not received, keeping the current running state unchanged.

If the first valve is in a non-closed state, indicating that the first compressor has not been brought into a normal operating state (e.g., the start-up process has not been completed), the current operating state of the components is maintained unchanged.

If the first valve is in a closed state, it is further determined whether the first compressor discharge temperature is above a set discharge temperature threshold.

If the discharge temperature of the first compressor is higher than the set discharge temperature threshold, under the current pressure condition of the refrigeration system, if the refrigerant at the discharge end of the second compressor is led to the suction end of the second compressor, the high-temperature alarm is generated at the latter with extremely high probability. To avoid this, the second expansion valve is controlled to switch from closed to open, and the opening degree of the second expansion valve is adjusted to the second target opening degree. Alternatively, a corresponding data table may be measured under experimental conditions, where a one-to-one correspondence between the deviation of the first compressor discharge temperature from the set discharge temperature threshold and the target temperature of the second heat exchange line is recorded. The target temperature of the corresponding second heat exchange pipeline can be called through a table lookup through deviation of the measured exhaust temperature of the first compressor from the set exhaust temperature threshold in real time. The target temperature of the second heat exchange pipeline can meet the cooling requirement of the refrigerant in the second switching pipeline. The target temperature and the actual temperature of the second heat exchange pipeline can be used for determining the second target opening of the second expansion valve through PID control. In other embodiments of the present invention, the second target opening degree may be a constant value. In this way, when the high temperature alarm exists, the refrigerant in the second heat exchange pipeline is cooled by controlling the second expansion valve, and the refrigerant is fully heat-exchanged with the refrigerant in the second switching pipeline.

If the first compressor discharge temperature is below the set suction temperature threshold, it is further determined whether the first compressor suction temperature is above the set suction temperature threshold. If the first compressor suction temperature is above the set suction temperature threshold, there is also a probability of a high temperature alarm. In order to avoid the situation, the second expansion valve is controlled to be switched from closed to open, the opening of the second expansion valve is regulated to the second target opening, the refrigerant in the second heat exchange pipeline is cooled by controlling the second expansion valve, and the refrigerant in the second switching pipeline is prepared to fully exchange heat with the refrigerant.

After the heat exchange preparation is made, it is further determined whether the system pressure ratio of the first compressor is higher than a set pressure ratio threshold. If the system pressure ratio of the first compressor is higher than the set pressure ratio threshold, the second valve is controlled to be switched from closed to open, the refrigerant is led to enter the second switching pipeline, the refrigerant in the second switching pipeline is further led to return to the air suction end of the second compressor after heat exchange with the refrigerant in the second heat exchange pipeline, the pressure ratio of the air suction end and the air discharge end of the second compressor is reduced, and surging is avoided. If the system pressure ratio of the first compressor is below the set pressure ratio threshold, optionally, the second valve is kept closed and the second compressor is started.

After the second compressor is started, the rotating speed of the second compressor is regulated, and when the rotating speed of the second compressor is the set rotating speed, the second valve is controlled to be switched from opening to closing; and switching the second expansion valve from the second target opening degree to close after the second valve is switched from open to close.

The set exhaust temperature threshold, the set suction temperature threshold and the set pressure ratio threshold are tested under experimental conditions and stored in the controller in advance.

In some embodiments of the present invention, the control conditions of the second expansion valve may also be set only to the first compressor discharge temperature above the set discharge temperature threshold, or only to the first compressor suction temperature above the set suction temperature threshold.

Similarly, if the second compressor is in an operating state and the first compressor is in a ready-to-start state, the controller performs the following steps.

It is determined whether a first compressor start command is received.

If a first compressor start command is received, it is further determined whether the second valve is in a closed state.

And if the first compressor starting instruction is not received, keeping the current running state unchanged.

If the second valve is in a non-closed state, indicating that the second compressor has not been brought into a normal operating state (e.g., the start-up process has not been completed), the current operating state of the components is maintained unchanged.

If the second valve is in a closed state, it is further determined whether the second compressor discharge temperature is above a set discharge temperature threshold.

If the second compressor discharge temperature is higher than the set discharge temperature threshold, under the current pressure condition of the refrigeration system, if the refrigerant at the discharge end of the first compressor is led to the suction end of the first compressor, the latter has extremely high probability of occurrence of high temperature alarm. To avoid this, the first expansion valve is controlled to switch from closed to open, and the opening degree of the first expansion valve is adjusted to the first target opening degree. Alternatively, a corresponding data table may be measured under experimental conditions, where a one-to-one correspondence between the deviation of the exhaust temperature of the second compressor from the set exhaust temperature threshold and the target temperature of the first heat exchange pipeline is recorded. The target temperature of the corresponding first heat exchange pipeline can be called through a table lookup through deviation of the measured exhaust temperature of the second compressor from the set exhaust temperature threshold in real time. The target temperature of the first heat exchange pipeline can meet the cooling requirement of the refrigerant in the first heat exchange pipeline. The target temperature and the actual temperature of the first heat exchange pipeline can be used for determining the first target opening of the first expansion valve through PID control. In other embodiments of the present invention, the first target opening degree may be a constant value. Therefore, when the high-temperature alarm exists, the refrigerant exists in the first heat exchange pipeline through the control of the first expansion valve, the refrigerant is reasonably cooled, and the refrigerant is fully heat-exchanged with the refrigerant in the second switching pipeline.

If the second compressor discharge temperature is below the set suction temperature threshold, it is further determined whether the second compressor suction temperature is above the set suction temperature threshold. If the first compressor suction temperature is above the set suction temperature threshold, there is also a probability of a high temperature alarm. In order to avoid the situation, the first expansion valve is controlled to be switched from closed to open, the opening of the first expansion valve is regulated to be the first target opening, the control of the first expansion valve is firstly used for cooling the refrigerant in the first heat exchange pipeline, and the refrigerant in the first switching pipeline is ready for full heat exchange.

After the heat exchange preparation is made, it is further determined whether the system pressure ratio of the second compressor is higher than a set pressure ratio threshold. If the system pressure ratio of the second compressor is higher than the set pressure ratio threshold, the first valve is controlled to be switched from closed to open, the refrigerant is led to enter the first switching pipeline, the refrigerant in the first switching pipeline is further led to return to the air suction end of the first compressor after heat exchange with the refrigerant in the first heat exchange pipeline, the pressure ratio of the air suction end and the air discharge end of the first compressor is reduced, and surging is avoided. If the system pressure ratio of the second compressor is below the set pressure ratio threshold, optionally, the first valve is kept closed and the first compressor is started.

After the first compressor is started, the rotating speed of the first compressor is regulated, and when the rotating speed of the first compressor is the set rotating speed, the first valve is controlled to be switched from opening to closing; and after the first valve is switched from open to closed, switching the first expansion valve from the first target opening to closed.

In some embodiments of the present invention, the control conditions of the first expansion valve may also be set only to the second compressor discharge temperature above the set discharge temperature threshold, or only to the second compressor suction temperature above the set suction temperature threshold.

Since the first compressor and the second compressor may have different capacities, the first target opening degree is calculated independently. When the first compressor and the second compressor have different capacities, the set discharge temperature threshold, the set suction temperature threshold, and the set pressure ratio threshold corresponding thereto may also be different in value.

A second embodiment of the refrigeration appliance according to the present invention will be described with reference to fig. 4 to 6. Unlike the first example, the first heat exchange line and the second heat exchange line are not provided in this embodiment. As shown in detail, the refrigeration apparatus further includes a first fan 35 and a second fan 37. The first fan 35 is disposed corresponding to the first switching line, and the second fan 37 is disposed corresponding to the second switching line. The first fan 35 and the section of the first switching line (shown as 17) may be integrated in one air-cooled heat exchanger 36, and the second fan 37 and the section of the second switching line (shown as 27) may be integrated in another air-cooled heat exchanger 38.

As shown in fig. 5, when the first compressor is operated and the first valve is closed and the second compressor start command is received, the first refrigerant circuit is turned on (as shown by arrow F1 in fig. 5), the controller controls the second valve to switch from closed to open, and the second fan 37 starts to operate, so that the refrigerant in the second switching pipeline is guided to exchange heat with air first and then returns to the suction end of the second compressor (as shown by arrow F3 in fig. 5).

Similarly, when the second compressor is operated and the second valve is closed and the first compressor start command is received, the second refrigerant circuit is turned on (as indicated by arrow F2 in fig. 6), the controller controls the first valve to switch from closed to open, and the first fan 35 starts to operate, so that the refrigerant in the second switching pipeline is led to exchange heat with air first and then returns to the suction end of the first compressor.

The controller controls the second valve to switch from open to close after the second compressor is started, and controls the second fan 37 to close after a predetermined time has elapsed since the second valve stopped.

Similarly, the controller controls the first valve to switch from open to closed after the first compressor is started, and controls the first fan 35 to be closed after a predetermined time has elapsed since the first valve stopped.

A third embodiment of the refrigeration appliance according to the present invention will be described with reference to fig. 7 to 9. Unlike the first embodiment, the first heat exchange line and the second heat exchange line are not provided in this embodiment, and as shown in detail, the refrigeration apparatus further includes a first water cooling line 31 and a second water cooling line 33. The first water-cooling line 31 is provided corresponding to the first switching line, and the second water-cooling line 33 is provided corresponding to the second switching line. The first water cooling line 31 and the section of the first switching line (as shown in fig. 17) may be integrated in one water cooling heat exchanger 32 and the second water cooling line 33 and the section of the second switching line (as shown in fig. 27) may be integrated in the other water cooling heat exchanger 34.

As shown in fig. 8, when the first compressor is operated and the first valve is closed and the second compressor start command is received, the first refrigerant circuit is turned on (as shown by arrow F1 in fig. 8), and the controller controls the second valve to switch from closed to open, so as to guide the refrigerant in the second switching pipeline to exchange heat with the water in the second water cooling pipeline 33 first and then return to the suction end of the second compressor (as shown by arrow F3 in fig. 8).

Similarly, when the second compressor is operated and the second valve is closed and the first compressor start command is received, the second refrigerant circuit is turned on (as indicated by arrow F2 in fig. 9), and the controller controls the first valve to switch from closed to open, so as to guide the refrigerant in the first switching pipeline to exchange heat with the water in the first water cooling pipeline 31 and return to the suction end of the first compressor.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the invention in any way, and any person skilled in the art may make modifications or alterations to the disclosed technical content to the equivalent embodiments. However, any simple modification, equivalent variation and variation of the above embodiments according to the technical substance of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. Refrigeration equipment, characterized in that it comprises:

a first refrigerant circuit for circulating the refrigerant sequentially through the first compressor, the condenser, the throttle device and the evaporator; the exhaust end of the first compressor is connected with the air suction end of the first compressor through a first switching pipeline, and a first valve is arranged on the first switching pipeline; the evaporator is additionally connected with the condenser through a first heat exchange pipeline, and a first expansion valve is arranged on the first heat exchange pipeline;

a second refrigerant loop for circulating the refrigerant sequentially through the second compressor, the condenser, the throttling device and the evaporator; the exhaust end of the second compressor is connected with the air suction end of the second compressor through a second switching pipeline, and a second valve is arranged on the second switching pipeline; the evaporator is additionally connected with the condenser through a second heat exchange pipeline, and a second expansion valve is arranged on the second heat exchange pipeline; and

The controller is used for controlling the second valve to be switched from being closed to be opened and guiding the refrigerant in the second switching pipeline to exchange heat with the refrigerant in the second heat exchange pipeline and then return to the air suction end of the second compressor after the first compressor works and the first valve is closed and simultaneously a second compressor starting instruction is received and the second expansion valve is switched from being closed to be a second target opening; or when the second compressor works, the second valve is closed, and after receiving the starting instruction of the first compressor and the first expansion valve is switched to the first target opening degree from closing, the first valve is switched to opening from closing, and the refrigerant in the first switching pipeline is led to exchange heat with the refrigerant in the first heat exchange pipeline and then returns to the air suction end of the first compressor.

2. A refrigeration device according to claim 1, wherein,

when the first compressor works and the first valve is closed, a second compressor starting instruction is received, and when the exhaust temperature of the first compressor is higher than a set exhaust temperature threshold value, the controller controls the second expansion valve to be switched from being closed to being opened, and controls the second expansion valve to be kept at a second target opening;

under the condition that the system pressure ratio of the first compressor is higher than a set pressure ratio threshold value and the second expansion valve is kept at a second target opening degree, the controller controls the second valve to be switched from closed to open, and guides the refrigerant in the second switching pipeline to exchange heat with the refrigerant in the second heat exchange pipeline and then return to the suction end of the second compressor; or (b)

When the second compressor works and the second valve is closed, a first compressor starting instruction is received, and when the exhaust temperature of the second compressor is higher than a set exhaust temperature threshold value, the controller controls the first expansion valve to be switched from being closed to being opened, and controls the first expansion valve to be kept at a first target opening;

and under the condition that the system pressure ratio of the second compressor is higher than a set pressure ratio threshold value and the first expansion valve is kept at a first target opening, the controller controls the first valve to be switched from closed to open, and guides the refrigerant in the first switching pipeline to exchange heat with the refrigerant in the first heat exchange pipeline and then return to the suction end of the first compressor.

3. A refrigeration device according to claim 1, wherein,

when the first compressor works, the first valve is closed, a second compressor starting instruction is received, and when the exhaust temperature of the first compressor is lower than a set exhaust temperature threshold value and the suction temperature of the first compressor is higher than a set suction temperature threshold value, the controller controls the second expansion valve to be switched from being closed to being opened, and controls the second expansion valve to be kept at a second target opening;

When the second compressor works and the second valve is closed, a first compressor starting instruction is received, and when the exhaust temperature of the second compressor is lower than a set exhaust temperature threshold value and the suction temperature of the second compressor is higher than a set suction temperature threshold value, the controller controls the first expansion valve to be switched from being closed to being opened, and controls the first expansion valve to be kept at a first target opening;

4. A refrigeration device according to claim 1, wherein,

the controller works at the first compressor, the first valve is closed, the second valve is controlled to be switched from closed to open after receiving a second compressor starting instruction, and the second valve is controlled to be switched from open to closed after the second compressor reaches a set rotating speed; or alternatively

The controller works at the second compressor, the second valve is closed, the first valve is controlled to be switched from closed to open after receiving a first compressor starting instruction, and the first valve is controlled to be switched from open to closed after the first compressor reaches a set rotating speed.

5. A refrigeration device according to claim 1, wherein,

the controller works at the first compressor, the first valve is closed, the second valve is controlled to be switched from closed to open after receiving a second compressor starting instruction, the second valve is controlled to be switched from open to closed after the second compressor reaches a set rotating speed, and the second expansion valve is switched from a second target opening to close after the second valve is closed; or (b)

The controller works at the second compressor, the second valve is closed, the first valve is controlled to be switched from closed to open after receiving a first compressor starting instruction, the first valve is controlled to be switched from open to closed after the first compressor reaches a set rotating speed, and the first expansion valve is switched from a first target opening to close after the first valve is closed.

6. A refrigeration device according to claim 1, wherein,

the controller controls the second valve to be switched from being closed to be opened and guides the refrigerant in the second switching pipeline to exchange heat with the second heat exchange pipeline and then return to the air suction end of the second compressor when the first compressor works and the first valve is closed, a second compressor starting instruction is received, and the system pressure ratio of the first compressor is higher than a set pressure ratio threshold value; when the first compressor works, the first valve is closed, a second compressor starting instruction is received, and the system pressure ratio of the first compressor is lower than a set pressure ratio threshold value, the second valve is kept closed, and the second compressor is started; or (b)

The controller controls the first valve to be switched from being closed to be opened and guides the refrigerant in the first switching pipeline to exchange heat with the first heat exchange pipeline and then return to the air suction end of the first compressor when the second compressor works and the second valve is closed, a first compressor starting instruction is received, and the system pressure ratio of the second compressor is higher than a set pressure ratio threshold value; and when the second compressor works, the second valve is closed, the first compressor is started after receiving the first compressor starting command, and the system pressure ratio of the second compressor is lower than the set pressure ratio threshold value, the first valve is kept closed, and the first compressor is started.