Vapor compression refrigerating system

Abstract

The utility model discloses a vapor compression refrigeration system, which is characterized by comprising a falling film evaporator, a falling film evaporator, a refrigerant inlet, a liquid outlet and an air outlet, the refrigerant inlet, the liquid outlet and the air outlet are arranged on the barrel, and the air outlet is communicated with an air inlet of a compressor; the condenser air inlet is communicated with the compressor air outlet; a refrigerant inlet of the evaporator is located in the top of the barrel, and a refrigerant distributor and a heat exchange pipe group are further arranged below the refrigerant inlet. The expansion machine is provided with an expansion machine liquid inlet and an expansion machine refrigerant outlet, the expansion machine liquid inlet is communicated with the condenser liquid outlet, and the expansion machine refrigerant outlet is communicated with the falling film evaporator refrigerant inlet. The heat exchange effect is improved, the refrigerant charging amount is reduced, meanwhile, the refrigerating capacity or the electric power consumption is not consumed, and high-efficiency operation of a refrigerating system is maintained.

Description

Technical Field

[0001] This application relates to the field of compression refrigeration technology, and more specifically, to a vapor compression refrigeration system using an expander and a falling film evaporator. Background Technology

[0002] Among the four main components of a vapor compression refrigeration system—compressor, condenser, throttling device, and evaporator—the design of the throttling device and evaporator is crucial. If the evaporator and throttling device are not designed properly, it will result in unsatisfactory heat exchange or excessive refrigerant charge, which is detrimental to energy conservation, environmental protection, and cost control. Therefore, it is very important to design the evaporator and throttling device properly.

[0003] Existing vapor compression refrigeration systems primarily use expansion valves and falling film evaporators as throttling devices and evaporators, which have the following disadvantages:

[0004] Expansion valve: The process by which high-temperature, high-pressure liquid refrigerant is throttled through the expansion valve and transformed into a low-temperature, low-pressure gaseous-liquid two-phase refrigerant is similar to an isenthalpic expansion process. During this process, a portion of the high-temperature, high-pressure liquid refrigerant transforms into a low-temperature, low-pressure gaseous refrigerant, and the work generated by the phase change is completely wasted.

[0005] Falling film evaporator: After the gas-liquid two-phase refrigerant enters the upper part of the falling film evaporator, it is distributed to the heat exchange tube group by a distributor. A sufficient liquid film can form on the surface of the heat exchange tubes in the upper part of the heat exchange tube group, resulting in good heat exchange efficiency. After passing through the upper part of the heat exchange tube group, some of the liquid refrigerant evaporates into a gaseous state and flows to the lower part of the heat exchange tube group, reducing the amount of liquid refrigerant. However, all three conventional designs for heat exchange in the lower part of the heat exchange tube group have drawbacks: 1) When the lower part of the heat exchange tube group is designed for falling film heat exchange, due to the reduction in liquid refrigerant, some heat exchange tube surfaces... 1) Inability to form a sufficient liquid film leads to poor heat exchange effect and increases the heat exchange area; 2) The lower part of the heat exchange tube group is filled with liquid heat exchange, which requires the lower part of the heat exchange tube group to be immersed in liquid refrigerant, resulting in an increase in refrigerant charge; 3) Using an ejector or electric pump to draw liquid refrigerant from the bottom of the evaporator to the evaporator inlet increases the refrigerant circulation volume, which can maintain the heat exchange effect and a smaller refrigerant charge. However, using an ejector will reduce the unit's cooling capacity, and an electric pump will increase power consumption. Both will reduce the efficiency of the refrigeration system. Utility Model Content

[0006] The purpose of this application is to provide a vapor compression refrigeration system that addresses the aforementioned deficiencies in the prior art by improving heat exchange efficiency and reducing refrigerant charge without consuming refrigeration capacity or electrical power, thereby maintaining high-efficiency operation of the refrigeration system.

[0007] Furthermore, this invention can achieve a higher heat transfer coefficient or a smaller heat transfer area, thereby increasing the refrigerant circulation volume.

[0008] Furthermore, this invention can realize energy recovery and storage, keeping the system energy-saving and stable in operation.

[0009] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0010] A vapor compression refrigeration system, characterized in that it comprises:

[0011] The compressor has an air inlet and an exhaust outlet.

[0012] The condenser is equipped with an air inlet and a liquid outlet; the air inlet of the condenser is connected to the exhaust port of the compressor.

[0013] A falling film evaporator includes a cylinder and a refrigerant inlet, a liquid outlet, and a gas outlet on the cylinder. The gas outlet is connected to the compressor inlet to draw gas from the evaporator container through the compressor. The liquid outlet is used to discharge refrigerant from the bottom. The refrigerant inlet is located at the top of the cylinder. A refrigerant distributor and a heat exchange tube group are also provided below the refrigerant inlet. The refrigerant inlet is used to input gas-liquid mixed refrigerant and deliver it to the refrigerant distributor. The refrigerant distributor evenly disperses and delivers the refrigerant into the cylinder space, so that the refrigerant is dispersed and diffused between the heat exchange tube group below.

[0014] An expander is provided with an expander inlet and an expander refrigerant outlet, and the expander inlet is connected to the condenser outlet, while the expander refrigerant outlet is connected to the falling film evaporator refrigerant inlet.

[0015] In the above technical solution, a load adjustment power mechanism is provided, and the expander is connected to the load adjustment power mechanism to form an adjustable load expander whose load is matched with the compressor load.

[0016] In the above technical solution, the load adjustment power mechanism is equipped with a refrigerant inlet and a refrigerant outlet. The refrigerant inlet is connected to the drain port of the falling film evaporator, and the refrigerant outlet is connected to the refrigerant inlet of the falling film evaporator.

[0017] In the above technical solution, when the expander at the condenser inlet is set to the working state, it generates expansion work through a phase change process, and the expansion work is used to drive the load adjustment power mechanism; the phase change process is set to the expander recovering at least part of the liquid refrigerant and converting it into a gaseous state.

[0018] In the above technical solution, the distributor is set in the upper part of the inner cavity of the falling film evaporator cylinder, the distributor inlet is set through the falling film evaporator cylinder, and only one area of ​​heat exchange tube group is set between the lower part of the distributor and the upper limit of the liquid level zone.

[0019] In the above technical solution, two sets of distributors are arranged at intervals inside the falling film evaporator, and heat exchange tube groups in two regions are arranged between the two sets of distributors. The lowermost heat exchange tube group is located above the upper limit of the liquid level zone.

[0020] In the above technical solution, the load adjustment power mechanism is a pump, and the expander and power pump are integrated into one unit.

[0021] In the above technical solution, the expander and the pump are directly connected by a shaft and integrated into a single component.

[0022] In the above technical solution, the expander and the power pump are integrated into a single unit by connecting a generator.

[0023] In the above technical solution, the expander and the power pump are connected in sequence to a generator and a storage battery to form a whole.

[0024] In the above technical solution, a control system is set up to control the operation of the load adjustment power mechanism in order to adjust the load of the expander to match the load of the compressor.

[0025] In the above technical solutions, the control system can be a general-purpose control system with a microcontroller or controller.

[0026] In the above technical solution, the expander is equipped with nozzles, and the load is adjusted by adjusting the nozzle opening or speed to match the refrigerant flow required by the compressor load.

[0027] The above-mentioned vapor compression refrigeration system can operate using a variable load control method, and its working principle is as follows:

[0028] An adjustable load expander is used, which is configured to match the compressor load. The expander load is adjusted according to the compressor load to match the refrigerant flow required by the compressor load.

[0029] When the expander is set to the working state, it generates expansion work through a phase change process to drive the load adjustment power mechanism; the phase change process is set to the expander recover at least part of the liquid refrigerant and convert it into gas, and draw the liquid refrigerant at the bottom of the evaporator to the refrigerant inlet of the evaporator to form a secondary cycle.

[0030] The expander adjusts the load by regulating the nozzle opening or rotation speed to match the refrigerant flow required by the compressor load.

[0031] This includes the initial load adjustment of the expander before the compressor starts, and the load adjustment of the expander when the compressor load increases or decreases.

[0032] In the above method, the load adjustment of the expander is gradually increased or decreased according to the threshold values ​​when the compressor load increases or decreases.

[0033] Before the compressor starts, the initial load adjustment of the expander first sets a small first load opening threshold. After the compressor starts, the load is increased to the second load opening threshold and maintained for a set time until the liquid level in the falling film evaporator stabilizes.

[0034] The second load opening threshold is greater than the first load opening threshold.

[0035] When the compressor is overloaded, the expander load increases until the liquid level in the falling film evaporator stabilizes; when the compressor is underloaded, the expander load decreases until the liquid level in the falling film evaporator stabilizes.

[0036] During expander load adjustment, compressor suction pressure, discharge pressure, compressor load, and heat exchanger liquid level are continuously monitored.

[0037] Therefore, this utility model uses an adjustable load expander to replace a single expansion valve to recover expansion work. The recovered expansion work drives a pump to draw the liquid refrigerant at the bottom of the evaporator to the inlet of the falling film evaporator, forming a secondary cycle, so as to solve the problems of increased refrigerant charge, increased heat exchanger area, or decreased refrigeration efficiency in the refrigeration system.

[0038] Compared to existing technologies, the beneficial effects of this application are:

[0039] This invention utilizes an expander to recover the work generated during the expansion process, which drives the pump. By replacing a single expansion valve with an adjustable load expander to recover expansion work, the refrigeration capacity is recycled twice. Compared to existing methods using ejector pumps or electric pumps, this invention has the advantages of not consuming refrigeration capacity or electrical power, and achieving high refrigeration efficiency.

[0040] The liquid refrigerant at the bottom of the falling film evaporator of this invention is pumped to the upper inlet of the evaporator for recirculation. Compared with falling film evaporators that do not use recirculation, it has the advantages of high heat transfer coefficient or small heat transfer area without increasing the amount of refrigerant.

[0041] Layered design: The falling film evaporator is equipped with two sets of distributors, one above the other. The recirculated refrigerant is drawn to the lower distributor, which can ensure that there is a sufficient liquid film thickness on the lower heat exchange tube group and avoid the heat exchange efficiency from decreasing due to the surface of the lower heat exchange tube group drying out.

[0042] By using a control system to match the expander load and the compressor load, compared to a fixed-load expander, an adjustable-load expander can adjust the load by adjusting the nozzle opening or outlet pressure, etc., to match the refrigerant flow required by the compressor load, and has the advantage of high operational stability.

[0043] Adding generators and batteries also enables energy recovery and storage, ensuring stable system operation. Attached Figure Description

[0044] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a structural diagram of a vapor compression refrigeration system using an expander and a falling film evaporator, as described in Embodiment 1 of this application.

[0046] Figure 2 This is a typical workflow diagram of the vapor compression refrigeration system according to an embodiment of this application.

[0047] Figure 3 This is a comparison diagram illustrating the effects of the vapor compression refrigeration system in this application.

[0048] Figure 4 This is a structural diagram of a vapor compression refrigeration system using an expander and a falling film evaporator, as shown in Embodiment 2 of this application.

[0049] Figure 5 This is a structural diagram of a vapor compression refrigeration system using an expander and a falling film evaporator, as described in Embodiment 3 of this application.

[0050] Figure 6 This is a structural diagram of a vapor compression refrigeration system using an expander and a falling film evaporator, as shown in Embodiment 4 of this application. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0052] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0053] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0054] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this application is in use. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0055] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0056] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" 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 application based on the specific circumstances.

[0057] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0058] The features and performance of this application will be further described in detail below with reference to the embodiments.

[0059] Example 1

[0060] The technical solution adopted in this embodiment is as follows: Figure 1As shown: A vapor compression refrigeration system using an expander and a falling film evaporator. The refrigeration system includes: a compressor 1, a falling film evaporator 2, a condenser 3, an expander 4, a pump 5, a control system, etc. The load of the expander 4 is matched and adjusted by the control system according to the load of the compressor.

[0061] In a further preferred configuration, the expander 4 and the pump 5 are integrated into a single unit, meaning the expander and the pump are directly connected via a shaft and integrated into one component. This can be achieved using conventional connection methods from existing technologies, which will not be elaborated further.

[0062] The high-temperature, high-pressure refrigerant at the outlet of condenser 3 in this patent passes through expander 4 and is converted into low-temperature, low-pressure refrigerant, which then enters distributor 6 of falling film evaporator 2. Falling film evaporator 2 includes distributor 6 and heat exchange tube group 7. The expansion work recovered by expander 4 drives pump 5 to pump the liquid refrigerant at the bottom of falling film evaporator 2 to distributor 6, forming a secondary cycle. In contrast, the process of expanding work recovered by expander 4 does not consume electricity and does not cause a decrease in refrigeration capacity, thus eliminating the refrigeration capacity and power consumption of traditional ejector pumps or electric pumps. After passing through distributor 6 in falling film evaporator 2, the low-temperature, low-pressure refrigerant evaporates into gaseous refrigerant on heat exchange tube group 7, and is then compressed into high-temperature, high-pressure gaseous refrigerant by compressor 1 before entering condenser 3. The high-temperature, high-pressure gaseous refrigerant condenses into high-temperature, high-pressure liquid refrigerant in condenser 3, forming a refrigeration cycle. The expander load is matched and adjusted by the control system according to the compressor load. The expander load can be adjusted by adjusting nozzle opening or speed to match the refrigerant flow rate required by the compressor load. (See appendix) Figure 2 This includes initial load regulation of the expander before compressor startup, and load regulation of the expander when the compressor load increases or decreases. Additionally, the system may include a level sensor to detect the liquid level at the bottom of the falling film evaporator 2, for load regulation of the expander 4 and / or control pump 5.

[0063] The vapor compression refrigeration system based on this invention, which uses an expander and a falling film evaporator, employs, as follows: Figure 2 The load control procedure is as follows:

[0064] Step 1: After the unit is started, check the compressor startup requirements and determine the compressor startup requirements:

[0065] If there is a startup requirement, proceed to the next step; otherwise, recheck the compressor startup requirement.

[0066] Step 2: Pre-open the expander to the first load threshold;

[0067] Monitor the compressor suction pressure, discharge pressure, load, and heat exchanger liquid level. Pre-start the expander to load A%, typically 30% to 90%.

[0068] The pre-opening degree of the expander is achieved by adjusting the expander nozzle opening, rotation speed, outlet pressure, or by installing a flow divider at the outlet.

[0069] Step 3: Increase the compressor load to the second load threshold;

[0070] After the compressor starts and increases the load to a specific load B% (40~90%), the duration is T1 (10s~300s).

[0071] Step 4: Adjust the expander load until the heat exchanger liquid level stabilizes; during this process, the compressor suction pressure, discharge pressure, load, and heat exchanger liquid level are continuously monitored;

[0072] Step 5: Compressor load assessment to determine whether the expander load should be increased;

[0073] If the compressor load increases by C%, the expander load increases by D%; if the compressor load does not increase by C%, then the compressor unload judgment is entered.

[0074] Step 6: Compressor load reduction judgment:

[0075] If the compressor is unloaded by E, the expander load will decrease by F.

[0076] Step 7: Adjust the expander load until the heat exchanger liquid level stabilizes;

[0077] During this process, the compressor suction pressure, discharge pressure, load, and heat exchanger liquid level are continuously monitored; the expander nozzle opening, speed, or other load adjustment mechanisms are activated.

[0078] The process ends, returning to the initial state or performing other operations.

[0079] Figure 2 A typical compressor start-up and load adjustment process is described to ensure the stability and efficiency of the system during start-up and operation. This is merely an auxiliary illustration of the structure and working principle of this invention. The disclosure of the structure of this invention does not depend on... Figure 2 The process of disclosure.

[0080] An expander is used in a refrigeration system, as follows: Figure 3As shown, 1-2-3-4b-1 represents a conventional refrigeration cycle with an expansion valve, 3-4b is approximately an isenthalpic process, and 3-4s is an ideal isentropic process (assuming 100% expander efficiency). In contrast, 1-2-3-4-1 represents the refrigeration cycle of this invention with an expander, and 3-4 represents the expander's operating process. This process consumes no electrical power and does not cause a decrease in cooling capacity (in actual operation, the expander efficiency cannot reach 100%). It can be seen that the advantages of using an expander compared to an expansion valve are: recovering some of the expansion work from process 3-4 and increasing the cooling capacity per unit refrigerant.

[0081] Example 2

[0082] Compared to Example 1, this embodiment is, for example... Figure 4 and Figure 2 As shown, a new generator 9 is added, and the expander 4 drives the generator 9 to generate electricity. The generator 9 drives the electric pump 5, which can utilize a conventional electric pump.

[0083] By adding a generator, energy recovery and storage can be achieved if a battery is configured, ensuring stable system operation.

[0084] Example 3

[0085] Compared to Example 1, this embodiment is, for example... Figure 2 and Figure 5 As shown, the falling film evaporator 2 has a secondary distributor 10 and an upper distributor 6 added inside to form two independent distributors; the lower heat exchange tube group 11 is set below the secondary distributor 10.

[0086] The refrigerant, pressurized by pump 5, flows into secondary distributor 10 to form a recirculation.

[0087] By installing two sets of distributors inside the falling film evaporator, and using an expander-driven pump to draw the recirculated refrigerant to the lower distributor, a sufficient liquid film can be ensured on the lower heat exchange tube group, preventing the surface of the lower heat exchange tube group from drying out and causing a decrease in heat exchange efficiency.

[0088] Example 4

[0089] Compared to Example 1, this embodiment is, for example... Figure 2 and Figure 6 As shown, generator 9 and battery 12 are added.

[0090] Expander 4 drives generator 9 to generate electricity, which is then stored in battery 12. Battery 12 drives electric pump 5. A liquid level sensor 13 is also added to detect the liquid level at the bottom of the evaporator and adjust the load on electric pump 5 based on the liquid level. Through the energy storage function of battery 12, the electric pump maintains stable operation even when the expansion energy recovered by the expander fluctuates due to changes in operating conditions and load.

[0091] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A vapor compression refrigeration system, characterized in that... include: The compressor has an air inlet and an air outlet. The condenser is equipped with an air inlet and a liquid outlet. The condenser inlet is connected to the compressor outlet; A falling film evaporator includes a cylinder and a refrigerant inlet, a liquid outlet, and a gas outlet provided on the cylinder. The gas outlet is connected to the compressor inlet to draw gas from the evaporator container through the compressor, and the liquid outlet is used to output the refrigerant from the bottom. The refrigerant inlet is located at the top of the cylinder. A refrigerant distributor and a heat exchange tube group are also installed below the refrigerant inlet. The refrigerant inlet is used to input gas-liquid mixed refrigerant and deliver it to the refrigerant distributor. The refrigerant distributor evenly distributes the refrigerant into the cylinder space, so that the refrigerant is dispersed and diffused between the heat exchange tube group below. An expander is provided with an expander inlet and an expander refrigerant outlet, and the expander inlet is connected to the condenser outlet, while the expander refrigerant outlet is connected to the falling film evaporator refrigerant inlet.

2. The vapor compression refrigeration system according to claim 1, characterized in that... A load adjustment power mechanism is provided, and the expander is connected to the load adjustment power mechanism to form an adjustable load expander whose load is matched with the compressor load.

3. The vapor compression refrigeration system according to claim 1, characterized in that... The load adjustment power mechanism is equipped with a refrigerant inlet and a refrigerant outlet. The refrigerant inlet is connected to the drain port of the falling film evaporator, and the refrigerant outlet is connected to the refrigerant inlet of the falling film evaporator.

4. The vapor compression refrigeration system according to claim 2 or 3, characterized in that... When the expander is set to the working state, it generates expansion work through a phase change process, and the expansion work is used to drive the load adjustment power mechanism; the phase change process is set so that the expander recovers at least a portion of the liquid refrigerant and converts it into a gaseous state.

5. The vapor compression refrigeration system according to claim 1, characterized in that... The distributor is located in the upper part of the inner cavity of the falling film evaporator. The distributor inlet passes through the falling film evaporator. Only one area of ​​heat exchange tube group is set between the lower part of the distributor and the upper limit of the liquid level zone.

6. The vapor compression refrigeration system according to claim 1, characterized in that... The falling film evaporator is equipped with two sets of distributors, one above the other, and heat exchange tube groups in two zones are set between the two sets of distributors. The lowermost heat exchange tube group is located above the upper limit of the liquid level zone.

7. The vapor compression refrigeration system according to claim 1, characterized in that... The load adjustment power mechanism is a pump, with the expander and power pump integrated into one unit.

8. The vapor compression refrigeration system according to claim 1, characterized in that... The expander and pump are integrated into one component by direct connection of the shaft.

9. The vapor compression refrigeration system according to claim 1, characterized in that... The expander and power pump are integrated into a single unit by connecting a generator.

10. The vapor compression refrigeration system according to claim 1, characterized in that... The expander and power pump are connected in sequence to a generator and a storage battery, forming a single unit.

11. The vapor compression refrigeration system according to claim 1, characterized in that... A control system is installed to control the operation of the load adjustment power mechanism.

12. The vapor compression refrigeration system according to claim 1, characterized in that... The expander is equipped with nozzles with adjustable opening.

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