Hot gas bypass loop of centrifugal water chilling unit
By adopting a parallel solenoid valve bypass branch design in the centrifugal chiller unit, the problems of slow response and high cost in the existing technology are solved, enabling rapid adjustment and stable compressor operation, reducing surge risk, and improving operational safety and reliability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- ZHEJIANG SINOKING AIR CONDITIONING & REFRIGERATION CO LTD
- Filing Date
- 2025-04-25
- Publication Date
- 2026-05-15
AI Technical Summary
In the existing hot gas bypass design of centrifugal chillers, the proportional regulating valve has a slow response and a large delay, and the single branch design cannot optimize the performance of the compressor under different operating scenarios, resulting in a high risk of surge and high cost.
A parallel bypass branch consisting of a first solenoid valve and a second solenoid valve is adopted. The first solenoid valve has a large diameter and the second solenoid valve has a small diameter, which leads to the liquid phase and gas phase regions of the evaporator respectively, so as to achieve rapid adjustment and stable compressor operation.
It achieves rapid response of hot gas bypass, reduces the compressor's operating pressure ratio, avoids surge, improves the compressor's operational safety and reliability, and reduces design costs.
Smart Images
Figure CN224246478U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of refrigeration and freezing equipment, and in particular to a hot gas bypass circuit for a centrifugal chiller unit. Background Technology
[0002] In chiller units, centrifugal compressors have advantages over screw compressors in that they have a larger single-head cooling capacity, smaller compressor size, and lighter weight. Figure 2 However, centrifugal compressors, being velocity-type compressors, are prone to surge at low-load operating limits, such as less than 30% capacity, and when the compressor's operating pressure ratio is too high. Severe surge can lead to compressor failure, requiring vigilant prevention. Current preventative measures employ hot gas bypass, directly directing the compressor's high-temperature, high-pressure exhaust gas to the low-pressure side, such as the evaporator. Currently, water-cooled chiller units primarily use bypass piping between the condenser and evaporator, with proportional regulating valves to control the bypass flow. The bypass circuit to the evaporator is a branch, with the inlet typically located in the gas phase region above the evaporator shell.
[0003] The current hot gas bypass design method uses proportional control valves with a relatively slow response. The working stroke from fully closed to fully open, and from fully open to fully closed, generally takes more than 30 seconds, which is a significant delay. Proportional control valves consist of a valve body and a regulator, and the specifications required for refrigeration system applications are relatively expensive, generally costing more than 3,000 yuan.
[0004] The current hot gas bypass design method has only one branch leading to the low-pressure evaporator of the refrigeration system, either in the gas phase region above the evaporator or in the liquid phase region at the bottom of the evaporator. This bypass has different effects on compressor operation. For example, at the lower limit of the centrifugal compressor's operating capacity, directing hot gas to the liquid phase region at the bottom of the evaporator requires only a small bypass to produce a significant effect. However, at high pressure ratios, directing hot gas to the gas phase region above the evaporator can also produce an effect more quickly. Clearly, a single branch design cannot optimally match the entire operating scenario of the centrifugal compressor. Utility Model Content
[0005] The purpose of this invention is to provide a hot gas bypass circuit for a centrifugal chiller unit in order to solve the above-mentioned problems.
[0006] This utility model achieves the above objectives through the following technical solutions:
[0007] A hot gas bypass circuit for a centrifugal chiller includes two parallel bypass branches consisting of a first solenoid valve and a second solenoid valve. The first solenoid valve is a large-diameter valve, and the second solenoid valve is a small-diameter valve. The inlet ends of the first solenoid valve and the second solenoid valve are connected to the same hot gas inlet pipe, and the outlet ends of the first solenoid valve and the second solenoid valve are connected to the evaporator through connecting pipe fittings.
[0008] This configuration, using a first and second solenoid valve instead of a proportional regulating valve, offers rapid opening and closing capabilities, accelerating the hot gas bypass effect. Furthermore, both valves are mature, reliable, and inexpensive, effectively reducing design costs. The connecting pipe leads to the shell-and-tube evaporator and features two flow directions: the second hot gas guide pipe leads to the liquid phase region at the bottom of the evaporator shell, while the first hot gas guide pipe leads to the gas phase region at the top of the evaporator shell. This allows for rapid stabilization under various harsh operating conditions of the centrifugal chiller unit by controlling the flow direction of the first and second solenoid valves, ensuring the safe operation of the centrifugal compressor.
[0009] Preferably, the connecting pipe includes a second hot gas guide pipe and a first hot gas guide pipe. The outlet end of the second solenoid valve is connected to the evaporator through the second hot gas guide pipe, and the outlet end of the first solenoid valve is connected to the evaporator through the first hot gas guide pipe. The evaporator is provided with a plurality of heat exchange tubes. The second hot gas guide pipe leads to the liquid phase region at the bottom of the evaporator cylinder, and the first hot gas guide pipe leads to the gas phase space region at the top of the evaporator cylinder.
[0010] In this design, the first solenoid valve has a large flow rate. Through the first hot gas guide pipe, it directs the flow to the area above the evaporator cylinder, quickly bypassing the high-pressure zone to the low-pressure zone, reducing the compressor discharge pressure and the operating pressure ratio, thus facilitating surge relief. During compressor startup, the reduced back pressure also lowers the starting load, aiding in compressor startup.
[0011] In this design, the second solenoid valve has a small flow rate, which is directed through the second hot gas guide pipe to the liquid phase region at the bottom of the evaporator shell. This region is the heat exchange zone of the heat exchange tubes, and the anti-surge baffle is designed there. For the flooded evaporator, the introduction of high-temperature hot gas from the compressor raises the refrigerant temperature in the liquid phase region, reducing the heat exchange temperature difference with the chilled water. The reduction in heat exchange can suppress the drop in chilled water temperature. For centrifugal compressors, the suction port guide vane opening can be increased to increase the flow rate, or for variable frequency compressors, the compressor speed can be increased, thereby avoiding surge. The design of the bypass branch of the second solenoid valve is beneficial for the safe operation of the compressor at its lowest capacity.
[0012] Preferably, the connecting pipe includes a second hot gas guide pipe, the outlet ends of the first solenoid valve and the second solenoid valve are connected to the second hot gas guide pipe through a tee, the evaporator is provided with a plurality of heat exchange tubes, and the second hot gas guide pipe leads to the liquid phase region at the bottom of the evaporator cylinder.
[0013] In this solution, as a further option, for applications with smaller cooling capacity, the two flow branches of the second hot gas guide pipe and the first hot gas guide pipe can be combined, both designed to lead to the bottom area of the evaporator, which can simplify the pipeline design and application.
[0014] Preferably, an anti-impact baffle is installed at the outlet of the second hot gas guide pipe located below the heat exchange pipe.
[0015] Preferably, the anti-impact baffle is bolted to the inside of the evaporator, and the top of the anti-impact baffle is a baffle structure, with through holes on both sides for the medium to pass through.
[0016] Preferably, the inlet end of the hot gas inlet pipe is connected to a tee, and the other two ends of the tee are respectively connected to the inlet end of the condenser pipe and the outlet end of the one-way valve. The inlet end of the one-way valve is connected to a centrifugal compressor, and the inlet end of the centrifugal compressor is connected to an evaporator pipe.
[0017] Compared with existing technologies, the beneficial effects are as follows:
[0018] 1. Compared with the existing hot gas bypass method, hot gas bypass adjustment is faster and can better optimize the matching of various operating scenarios of centrifugal compressors.
[0019] 2. Compared with existing hot gas bypass methods, hot gas bypass design has lower costs and is more reliable. Attached Figure Description
[0020] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0021] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the hot gas bypass circuit of the centrifugal chiller unit described in this utility model;
[0022] Figure 2 This is a schematic diagram of the structure of Embodiment 2 of the hot gas bypass circuit of the centrifugal chiller unit described in this utility model.
[0023] The annotations in the attached figures are explained as follows:
[0024] 1. First solenoid valve; 2. Second solenoid valve; 3. Hot gas inlet pipe; 4. Second hot gas guide pipe; 5. First hot gas guide pipe; 7. Anti-impact baffle; 8. Heat exchanger pipe; 9. Evaporator piping; 10. Centrifugal compressor; 11. Check valve; 12. Condenser piping; 13. Evaporator. Detailed Implementation
[0025] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.
[0026] Example 1
[0027] like Figure 1 As shown, a hot gas bypass circuit for a centrifugal chiller unit includes two parallel bypass branches consisting of a first solenoid valve 1 and a second solenoid valve 2. The first solenoid valve 1 is a large-diameter valve, and the second solenoid valve 2 is a small-diameter valve. The inlet ends of the first solenoid valve 1 and the second solenoid valve 2 are connected to the same hot gas inlet pipe 3, and the outlet ends of the first solenoid valve 1 and the second solenoid valve 2 are connected to the evaporator 13 through connecting pipe fittings.
[0028] The proportional regulating valve is replaced by a first solenoid valve 1 and a second solenoid valve 2. The first and second solenoid valves 1 and 2 have rapid opening and closing characteristics, accelerating the hot gas bypass effect. Furthermore, the first and second solenoid valves 1 and 2 are mature, reliable, and inexpensive, effectively reducing design costs. The connecting pipe is the pipe 9 leading to the shell-and-tube evaporator, with two flow directions: the second hot gas guide pipe 4 leads to the liquid phase region at the bottom of the evaporator 13, and the first hot gas guide pipe 5 leads to the gas phase space region at the top of the evaporator 13. Under different harsh operating conditions of the centrifugal chiller unit, by controlling the flow direction of the first and second solenoid valves 1 and 2, the stabilizer function can be quickly activated, ensuring the safe operation of the centrifugal compressor 10.
[0029] In this embodiment, the connecting pipes include a second hot gas guide pipe 4 and a first hot gas guide pipe 5. The outlet of the second solenoid valve 2 is connected to the evaporator 13 through the second hot gas guide pipe 4, and the outlet of the first solenoid valve 1 is connected to the evaporator 13 through the first hot gas guide pipe 5. The evaporator 13 is provided with several heat exchange tubes 8. The second hot gas guide pipe 4 leads to the liquid phase region at the bottom of the evaporator 13 cylinder, and the first hot gas guide pipe 5 leads to the gas phase space region at the top of the evaporator 13 cylinder. The two bypass branches are designed in parallel, and different bypass flow rates can be achieved by controlling the opening and closing of the solenoid valves.
[0030] In this design, the first solenoid valve 1 has a large flow rate, which is directed to the area above the evaporator 13 cylinder through the first hot gas guide pipe 5. This allows for the rapid bypassing of a large flow of hot gas from the high-pressure zone to the low-pressure zone, reducing the compressor discharge pressure and the operating pressure ratio, thus facilitating the elimination of surge. During the compressor start-up phase, the reduced back pressure also lowers the starting load, which is beneficial for compressor startup.
[0031] In this design, the second solenoid valve 2 has a small flow rate and is directed through the second hot gas guide pipe 4 to the liquid phase region at the bottom of the evaporator 13 cylinder. This region is the heat exchange zone of the heat exchange tubes and is equipped with an anti-surge baffle 7. For the flooded evaporator 13, the introduction of high-temperature hot gas from the compressor raises the refrigerant temperature in the liquid phase region, reducing the heat exchange temperature difference with the chilled water. The reduction in heat exchange can suppress the drop in chilled water temperature. The centrifugal compressor 10 can increase the opening of the suction port guide vanes to increase the flow rate, or the variable frequency compressor can increase the compressor speed, thereby avoiding surge. The bypass branch design of the second solenoid valve 2 is beneficial for the safe operation of the compressor at its lowest capacity.
[0032] In this embodiment, an anti-impact baffle 7 is installed at the outlet of the second hot gas guide pipe 4, located below the heat exchange pipe 8.
[0033] In this embodiment, the anti-impact baffle 7 is bolted to the inside of the evaporator 13, and the top of the anti-impact baffle 7 is a baffle structure, with through holes for the medium to pass through on both sides.
[0034] In this embodiment, the inlet end of the hot gas inlet pipe 3 is connected to a tee, and the other two ends of the tee are respectively connected to the inlet end of the condenser pipe 12 and the outlet end of the one-way valve 11. The inlet end of the one-way valve 11 is connected to the centrifugal compressor 10, and the inlet end of the centrifugal compressor 10 is connected to the evaporator pipe 9.
[0035] Working principle: The first solenoid valve 1 is a large-diameter valve that opens when the compressor starts and closes after startup. After the compressor starts running, when the centrifugal compressor 10 is in its high-pressure ratio operating range or near the upper limit of the condensing temperature, the first solenoid valve 1 opens to quickly bypass the compressor discharge to the evaporator 13. This reduces the compressor discharge pressure and effectively lowers the operating pressure ratio of the centrifugal compressor 10, thus preventing surge. When the compressor moves away from the high-pressure ratio or the upper limit of the condensing temperature, the first solenoid valve 1 closes.
[0036] The second solenoid valve 2 is a small-diameter valve. When the centrifugal compressor 10 is running at its minimum capacity, if a reduction in compressor capacity is still required, the second solenoid valve 2 is opened to guide the high-temperature, high-pressure gas from the compressor into the liquid phase zone of the evaporator 13. This effectively weakens the heat transfer intensity. Therefore, the required increased cooling capacity can be obtained by increasing the flow rate through the suction guide vanes of the centrifugal compressor 10 or by increasing the compressor speed. This adjustment can prevent surge. When the compressor capacity enters the holding range, the second solenoid valve 2 can be closed.
[0037] If opening a single solenoid valve during compressor operation fails to achieve the desired effect, another bypass branch can be activated to maximize the bypass function.
[0038] Example 2
[0039] like Figure 2 As shown, a hot gas bypass circuit for a centrifugal chiller unit includes two parallel bypass branches consisting of a first solenoid valve 1 and a second solenoid valve 2. The first solenoid valve 1 is a large-diameter valve, and the second solenoid valve 2 is a small-diameter valve. The inlet ends of the first solenoid valve 1 and the second solenoid valve 2 are connected to the same hot gas inlet pipe 3, and the outlet ends of the first solenoid valve 1 and the second solenoid valve 2 are connected to the evaporator 13 through connecting pipe fittings.
[0040] The proportional regulating valve is replaced by a first solenoid valve 1 and a second solenoid valve 2. The first and second solenoid valves 1 and 2 have rapid opening and closing characteristics, accelerating the hot gas bypass effect. Furthermore, the first and second solenoid valves 1 and 2 are mature, reliable, and inexpensive, effectively reducing design costs. The connecting pipe is the pipe 9 leading to the shell-and-tube evaporator, with two flow directions: the second hot gas guide pipe 4 leads to the liquid phase region at the bottom of the evaporator 13, and the first hot gas guide pipe 5 leads to the gas phase space region at the top of the evaporator 13. Under different harsh operating conditions of the centrifugal chiller unit, by controlling the flow direction of the first and second solenoid valves 1 and 2, the stabilizer function can be quickly activated, ensuring the safe operation of the centrifugal compressor 10.
[0041] In this embodiment, the connecting pipe includes a second hot gas guide pipe 4. The outlet ends of the first solenoid valve 1 and the second solenoid valve 2 are connected to the second hot gas guide pipe 4 through a tee. The evaporator 13 is provided with a plurality of heat exchange tubes 8. The second hot gas guide pipe 4 leads to the liquid phase region at the bottom of the evaporator 13 cylinder.
[0042] In this scheme, as a further option, for applications with smaller cooling capacity, the two flow branches of the second hot gas guide pipe 4 and the first hot gas guide pipe 5 can be combined and both designed to lead to the bottom area of the evaporator 13, which can simplify the pipeline design and application.
[0043] In this embodiment, an anti-impact baffle 7 is installed at the outlet of the second hot gas guide pipe 4, located below the heat exchange pipe 8.
[0044] In this embodiment, the anti-impact baffle 7 is bolted to the inside of the evaporator 13, and the top of the anti-impact baffle 7 is a baffle structure, with through holes for the medium to pass through on both sides.
[0045] In this embodiment, the inlet end of the hot gas inlet pipe 3 is connected to a tee, and the other two ends of the tee are respectively connected to the inlet end of the condenser pipe 12 and the outlet end of the one-way valve 11. The inlet end of the one-way valve 11 is connected to the centrifugal compressor 10, and the inlet end of the centrifugal compressor 10 is connected to the evaporator pipe 9.
[0046] Working principle: Hot gas bypass application control. When the compressor starts, the first solenoid valve 1 is opened to reduce the compressor starting load. After the start-up is completed, the first solenoid valve 1 is closed.
[0047] In the hot gas bypass application control, when the compressor is running, if the current compressor working pressure ratio is 97% of the upper limit of the pressure ratio, solenoid valve 2 is opened. If the working pressure ratio is still maintained at 97% after 60 seconds, the first solenoid valve 1 is opened and the second solenoid valve 2 is closed. If the working pressure ratio is less than 94% of the upper limit of the pressure ratio, the first bypass solenoid valve 1 is closed and the second solenoid valve 2 is opened. When the working pressure ratio is less than 90% of the upper limit of the pressure ratio, all bypass solenoid valves are closed.
[0048] In the hot gas bypass control application, if the compressor is currently operating at its minimum capacity, but the control water temperature determines that the compressor still needs to reduce its load, then the second solenoid valve 2 is opened. If, after 180 seconds, the compressor is still operating at its minimum capacity and still needs to reduce its load, then the first solenoid valve 1 is opened. When the control water temperature determines that the compressor is switching to a capacity-maintaining state, then the first solenoid valve 1 is closed. When the control water temperature determines that the compressor is switching to a capacity-loaded state, then all bypass solenoid valves are closed.
[0049] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed utility model.
Claims
1. A hot gas bypass circuit for a centrifugal chiller unit, characterized in that: It includes two parallel bypass branches consisting of a first solenoid valve (1) and a second solenoid valve (2). The first solenoid valve (1) is a large-diameter valve, and the second solenoid valve (2) is a small-diameter valve. The inlet ends of the first solenoid valve (1) and the second solenoid valve (2) are connected to the same hot gas inlet pipe (3). The outlet ends of the first solenoid valve (1) and the second solenoid valve (2) are connected to the evaporator (13) through connecting pipe fittings.
2. The hot gas bypass circuit of a centrifugal chiller unit according to claim 1, characterized in that: The connecting pipe includes a second hot gas guide pipe (4) and a first hot gas guide pipe (5). The outlet of the second solenoid valve (2) is connected to the evaporator (13) through the second hot gas guide pipe (4). The outlet of the first solenoid valve (1) is connected to the evaporator (13) through the first hot gas guide pipe (5). The evaporator (13) is provided with a plurality of heat exchange tubes (8). The second hot gas guide pipe (4) leads to the liquid phase region at the bottom of the evaporator (13) cylinder, and the first hot gas guide pipe (5) leads to the gas phase space region at the top of the evaporator (13) cylinder.
3. The hot gas bypass circuit of a centrifugal chiller unit according to claim 1, characterized in that: The connecting pipe includes a second hot gas guide pipe (4). The outlet ends of the first solenoid valve (1) and the second solenoid valve (2) are connected to the second hot gas guide pipe (4) through a tee. The evaporator (13) is provided with several heat exchange tubes (8). The second hot gas guide pipe (4) leads to the liquid phase region at the bottom of the evaporator (13) cylinder.
4. A hot gas bypass circuit for a centrifugal chiller unit according to any one of claims 1 or 2, characterized in that: An anti-impact baffle (7) is installed at the outlet of the second hot gas guide pipe (4) located below the heat exchange pipe (8).
5. A hot gas bypass circuit for a centrifugal chiller unit according to claim 4, characterized in that: The anti-impact baffle (7) is bolted inside the evaporator (13), and the top of the anti-impact baffle (7) is a baffle structure, and the two sides are through holes for the medium to pass through.
6. A hot gas bypass circuit for a centrifugal chiller unit according to claim 5, characterized in that: The inlet end of the hot gas inlet pipe (3) is connected to a tee, and the other two ends of the tee are respectively connected to the inlet end of the condenser pipe (12) and the outlet end of the one-way valve (11). The inlet end of the one-way valve (11) is connected to the centrifugal compressor (10), and the inlet end of the centrifugal compressor (10) is connected to the evaporator pipe (9).