Multi-stage counterflow gradient cold storage heat exchange system, control method thereof and beverage machine

Abstract

The application discloses a multi-stage countercurrent gradient cold accumulation type heat exchange system, a control method thereof and a beverage machine. The system comprises at least two serially connected cold accumulation units, a cold exchange pipeline and a heat exchange pipeline. The cold exchange pipeline is an evaporator part of a refrigeration circuit, sequentially serially connected to flow through each cold accumulation unit to exchange cold energy to the cold accumulation medium. The heat exchange pipeline sequentially passes through each cold accumulation unit to provide a to-be-cooled fluid to flow and exchange heat with the cold accumulation medium. The fluid flow direction in the heat exchange pipeline is opposite to the refrigerant flow direction in the cold exchange pipeline. When continuously outputting, the temperature of a previous cold accumulation unit is lower than that of a subsequent unit, thereby forming and maintaining a temperature gradient for countercurrent heat exchange. The volume of the previous cold accumulation unit is less than or equal to that of the subsequent unit. The volume of the first unit is configured according to the single-cup refrigeration demand to realize rapid starting. The volume of the subsequent unit is relatively large, serving as a gradient cold accumulation buffer to ensure the constant temperature of continuous cup output. The application solves the problems of slow starting and unstable temperature of continuous cup output of a traditional beverage machine.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fluid cooling and heat exchange, and in particular to a heat exchange system adopting a multi-stage cold storage and counter-flow heat exchange mechanism. More specifically, the present application is particularly suitable for devices requiring rapid provision of constant-temperature cooling fluid, such as beverage machines, cold beverage preparation devices, etc. BACKGROUND

[0002] In commercial beverage machines (e.g. on-the-go carbonated beverage machines, iced coffee machines) and the like, it is often necessary to continuously supply low-temperature and constant-temperature drinking water for the preparation of cold beverages. The traditional mainstream solution is to use a single large-capacity cold storage water tank for indirect refrigeration: the refrigeration system first cools the entire cold storage water in the water tank to a low temperature, and the drinking water to be prepared is then cooled by flowing through the heat exchange coil immersed in the cold water tank.

[0003] However, this traditional solution has two inherent defects that are interrelated:

[0004] First, the start-up waiting time is long. After starting, the entire single large-capacity cold water tank must be uniformly cooled from room temperature (e.g. 25°C) to the working temperature (usually 1-4°C) before the system can produce cold beverages with qualified temperature. This preheating process often takes as long as 20-30 minutes, which cannot meet the needs of instant business or sudden consumption.

[0005] Second, the temperature stability is poor when continuously outputting. When continuously and highly loaded, the drinking water flowing through the heat exchange coil continuously absorbs heat from the cold storage water. Since the entire cold storage water body is uniformly cooled, the accumulated heat will cause the temperature to continuously and uniformly rise. The speed at which the refrigeration system supplements the cold cannot instantaneously match the changes in heat load, resulting in a significant rise in the temperature of the subsequent beverages, which severely affects the product taste consistency and user experience.

[0006] Some existing improved designs, such as the addition of auxiliary pre-cooling modules or the optimization of control algorithms, have not fundamentally changed the physical nature of "single uniform temperature field cold storage", and thus cannot simultaneously and thoroughly solve the "slow start" and "large temperature difference in continuous cup output" contradiction at the system level. SUMMARY

[0007] In view of the deficiencies of the prior art, the primary purpose of the present application is to provide a multi-stage counter-flow gradient cold storage heat exchange system, which aims to fundamentally change the cold storage and heat exchange mode to simultaneously achieve: 1) the time from starting to providing qualified cooling fluid is extremely short (fast start); 2) in a high-intensity continuous working state, the temperature of the output fluid remains highly constant (constant temperature output). Another purpose of the present application is to provide a control method based on the above-mentioned system. Still another purpose of the present application is to provide a beverage machine integrated with the above-mentioned system.

[0008] To achieve the above object, the present application adopts the following technical solutions:

[0009] In a first aspect, a multi-stage counter-flow gradient cold storage heat exchange system is provided. The system comprises: at least two cold storage units arranged in series, each of which is enclosed with a cold storage medium; a cold exchange pipeline which is an evaporator part of a refrigeration circuit and sequentially flows through the at least two cold storage units to exchange the cold energy of the refrigerant to the cold storage medium; and a heat exchange pipeline which sequentially passes through the at least two cold storage units to provide a flow passage for a fluid to be cooled and exchanges heat with the cold storage medium through the wall of the pipeline when flowing through each cold storage unit; wherein the overall flow direction of the fluid to be cooled in the heat exchange pipeline is opposite to the overall flow direction of the refrigerant in the cold exchange pipeline; and the system is configured to form and maintain a temperature gradient for counter-flow heat exchange between the at least two cold storage units in a working state of continuously outputting the cooled fluid, the temperature of the cold storage medium in the preceding cold storage unit in the flow direction of the refrigerant being lower than that in the subsequent cold storage unit, and the temperature gradient being jointly established by the volume difference of the cold storage units and the series counter-flow arrangement of the cold exchange pipeline and the heat exchange pipeline.

[0010] As a preferred embodiment, the volume of the preceding cold storage unit is less than or equal to the volume of the subsequent cold storage unit in the flow direction of the refrigerant.

[0011] Further, the volume of the first cold storage unit in the flow direction of the refrigerant is configured to only accommodate the equivalent of the cold storage medium required to cool a single maximum preset flow of the fluid to be cooled from an initial temperature to a target temperature; and / or the total volume of the second and subsequent cold storage units is significantly greater than the volume of the first cold storage unit.

[0012] As an embodiment, the at least two cold storage units are physically independent sealed containers or independent chambers formed by a heat insulation structure in a shared container.

[0013] Further, the adjacent cold storage units are connected through a limited flow structure. The flow area of the limited flow structure is configured to allow static pressure balance between the adjacent units (such as facilitating water injection) but to inhibit convection circulation caused by density difference which is sufficient to significantly destroy the temperature gradient.

[0014] As an intelligent control embodiment, the system further comprises a control unit and a first temperature sensor. The first temperature sensor is arranged in the first cold storage unit in the flow direction of the refrigerant. The control unit is in communication connection with the first temperature sensor and the refrigeration circuit and is configured to control the operation of the refrigeration circuit according to the temperature feedback in the first cold storage unit to maintain the temperature of the cold storage medium in the first cold storage unit within a preset target temperature range above the freezing point.

[0015] Based on the above structure, the system is configured to output cooling fluid through the heat exchange pipeline when the temperature of the cold storage medium in the first cold storage unit reaches the first preset threshold, without waiting for the remaining cold storage units to reach the first preset threshold.

[0016] Also based on the above structure, in the steady state operation of continuous output of cooling fluid, the fluctuation range of the temperature of the cold storage medium in the preceding cold storage unit in the flow direction of the refrigerant is smaller than that of the following cold storage unit.

[0017] In a second aspect, a control method for the above system is provided. The method comprises: starting the refrigeration circuit to make the refrigerant flow through the cold exchange pipeline in a first direction; when cooling fluid needs to be output, making the fluid to be cooled flow through the heat exchange pipeline in a second direction opposite to the first direction; wherein the operation of the refrigeration circuit is controlled so that, during the continuous output of cooling fluid, the temperature of the cold storage medium in the preceding cold storage unit in the first direction is lower than that of the following cold storage unit, thereby forming and maintaining a temperature gradient for counterflow heat exchange between the at least two cold storage units.

[0018] In a third aspect, a beverage machine is provided. The beverage machine comprises a beverage mixing assembly, and the key point is that the beverage machine is integrated with the multi-stage counterflow gradient cold storage heat exchange system as described above. The outlet end of the heat exchange pipeline of the system is connected to the beverage mixing assembly for providing cooling fluid (such as cold water) to the beverage mixing assembly.

[0019] Energy transfer framework:

[0020] In order to more clearly illustrate the energy transfer path of the present application, the system comprises two core energy exchange circuits:

[0021] Cold exchange circuit: refers to the circuit composed of the refrigeration circuit and its cold exchange pipeline. Its core function is to actively generate cold energy through the evaporation phase change of the refrigerant and transfer (exchange) the cold energy to the cold storage medium in each cold storage unit, which can be regarded as the "cold production-cold storage" link of the system.

[0022] Heat exchange circuit: refers to the circuit composed of the heat exchange pipeline. Its core function is to passively absorb (exchange) the stored cold energy of the cold storage medium when the fluid to be cooled (such as drinking water) flows through each cold storage unit, so as to be cooled to the target temperature, which can be regarded as the "cold taking-cold using" link of the system.

[0023] The present application realizes the dual purposes of rapid start and constant temperature output by making the flow direction of the fluid in the heat exchange circuit opposite to the flow direction of the refrigerant in the cold exchange circuit, and combining with the specific cold storage unit capacity configuration. Advantages

[0024] Compared with the prior art, the technical scheme provided by the application has at least the following advantages:

[0025] By means of "structural grading" and "controlling focus", the system does not need to cool all the cold storage medium at start-up, but only needs to cool the first cold storage unit to a target temperature, so that qualified cold water can be output through the counterflow flow channel. In particular, by miniaturizing the first unit to the capacity required for "single-cup refrigeration", the cooling time is extremely shortened. This shortens the start-up waiting time of the traditional scheme for tens of minutes to within a few minutes, and realizes "ready-to-use after start-up".

[0026] By means of combination of counterflow design and series connection of cold storage, a stable gradient field from low temperature to high temperature is automatically formed and maintained during continuous operation. The large-capacity cold storage unit in the rear stage serves as a high-efficiency "temperature step buffer pool", which can fully pre-cool the normal-temperature fluid flowing in, and absorb most of the heat load, so that the temperature of the fluid flowing to the first small unit is close to the target value, thereby ensuring that the temperature fluctuation of the core low-temperature unit is extremely small. The "gradient buffer" effect fundamentally eliminates the temperature rise phenomenon during continuous cup dispensing.

[0027] Counterflow heat exchange provides a larger logarithmic mean temperature difference, and improves the heat exchange efficiency. The system works in a dynamic equilibrium gradient state, and the refrigeration circuit load is stable, which avoids frequent start-stop or high-load impact of the compressor caused by large and uniform temperature fluctuation, and is beneficial to reduce energy consumption and prolong the service life of the core components of the equipment.

[0028] The principle of the application is clear, and the implementation is strong. The cold storage unit can adopt multiple independent containers for modular production and maintenance, or adopt an integrated multi-chamber structure to save space. The static pressure balance and thermal isolation contradiction between the multi-chambers are ingeniously solved by the flow-through structure. Through accurate temperature control of the first cold storage unit, icing of the medium in the first cold storage unit can be effectively prevented, and safe and reliable operation of the system is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The system structure and working principle diagram of an embodiment of the application.

[0030] Explanation of reference signs: 11, first cold storage unit; 12, second cold storage unit; 13, third cold storage unit; 21, condenser; 22, cold exchange pipeline (evaporator part); 3, heat exchange pipeline; F1, refrigerant flow direction (first direction); F2, to-be-cooled fluid flow direction (second direction); 4, first temperature sensor. DETAILED DESCRIPTION

[0031] In order to make the objects, technical solutions and advantages of the present application clearer, the embodiments of the present application will be further described in detail below with reference to the drawings. It should be noted that the following description is only for the preferred embodiments of the present application and is not intended to limit the present application.

[0032] Embodiment 1: System structure

[0033] Referring to Figure 1 This embodiment discloses a multi-stage counter-flow gradient cold storage heat exchange system. The system comprises three independent cold storage units arranged in series, i.e. a first cold storage unit 11, a second cold storage unit 12 and a third cold storage unit 13. Each cold storage unit is encapsulated with water as the cold storage medium.

[0034] The refrigeration circuit comprises a compressor, a condenser 21 and a throttling device connected in sequence. The throttling device is followed by a cold exchange pipeline 22, which is the evaporator part of the refrigeration circuit. The cold exchange pipeline 22 is sequentially connected in series through the first, second and third cold storage units. The refrigerant flows in the cold exchange pipeline 22 in the direction F1, and absorbs the heat of the cold storage water in each unit in sequence to evaporate, thereby exchanging cold to the cold storage medium. Therefore, the first cold storage unit 11 obtains the largest cooling strength and the lowest temperature; the third cold storage unit 13 obtains the smallest cooling strength and the relatively highest temperature.

[0035] The heat exchange pipeline sequentially passes through the first, second and third cold storage units. The drinking water to be cooled enters from the inflow end and flows in the direction F2. First, it flows through the pipeline part arranged in the third cold storage unit 13 and preliminarily exchanges heat (pre-cooling) with the cold storage water with a higher temperature. Then, the water flowing out of the third unit enters the pipeline part in the second cold storage unit 12 and is further cooled. Finally, it flows into the pipeline part in the first cold storage unit 11, where it completes the final heat exchange with the cold storage water with the lowest temperature, and is output from the outflow end after reaching the target low temperature (e.g. 3-5℃). The flow direction F2 of the drinking water is completely opposite to the flow direction F1 of the refrigerant.

[0036] In this embodiment, in the direction F1, the volume relationship of the cold storage units is: V101 ≤ V102 ≤ V103. In particular, the volume of the first cold storage unit 11 is precisely designed to be equivalent to the cold storage water required to release the heat for cooling a single cup of the maximum capacity (e.g. 500ml) of drinking water from 25℃ to 4℃. The total volume of the second cold storage unit 12 and the third cold storage unit 13 is much larger than the volume of the first unit 11, for example, 5-10 times the volume of the first unit 11, and constitutes the main gradient cold storage buffer zone.

[0037] The adjacent independent cold storage units (containers) are connected at the bottom by a balance pipe with a small aperture (i.e. a restricted flow passage). The balance pipe allows the water level in each container to be kept uniform when the system is being filled, but the aperture is small enough (e.g. 2-5 mm in diameter) to effectively suppress natural convection caused by temperature differences, thereby protecting the temperature gradient formed during operation.

[0038] Example 2: Control method

[0039] With reference to the above description of the system, the control method is described as follows. Figure 1 A first temperature sensor 4 is provided in the first cold storage unit 11. The control unit receives the temperature signal from the first temperature sensor 4 and controls the operation of the refrigeration circuit accordingly.

[0040] Start-up phase: The control unit starts the refrigeration circuit. The refrigerant flows in the direction of F1, preferentially cooling the first cold storage unit 11. The control unit continuously monitors the reading of the first temperature sensor 4 and, when the temperature is detected to have reached a first preset operating value (e.g. 4°C), it is determined that the system can output qualified cold water. At this time, the temperatures of the second and third cold storage units can still be at a high level (e.g. 15°C, 20°C), but this does not affect the rapid output of cold water by the system.

[0041] Steady-state operating phase: When continuously outputting cold water, the core control objective of the control unit is to maintain the temperature of the first cold storage unit 11 within a set range (e.g. 3-5°C). Due to the buffering effect of the counterflow gradient, the normal temperature drinking water is fully pre-cooled when flowing through the second and third units, and the temperature is already low when it flows into the first unit, so the temperature fluctuation of the first unit is limited to a very small range. The control unit maintains this dynamic balance by controlling the start-stop or frequency conversion of the compressor, thereby ensuring the constant temperature of the outlet water.

[0042] The flow of the control method mainly includes: system power-on initialization; starting the refrigeration, preferentially cooling the first unit; determining whether the temperature of the first unit reaches the threshold value; if so, allowing the output of cold water; during the output process, continuously monitoring the temperature of the first unit and controlling the refrigeration circuit to maintain the stability of the gradient.

[0043] Example 3: Beverage machine application

[0044] A beverage machine comprises a multi-stage counterflow gradient cold storage heat exchange system as described in Example 1. The cold water output from the outlet end of the heat exchange pipeline 3 of the system is directly delivered to the beverage mixing components of the beverage machine (such as syrup valves, carbon dioxide injection valves, etc.), for the immediate preparation of cold beverages with consistent taste temperature, such as ice-cold carbonated beverages or iced coffee.

[0045] Example 4: Integrated cold storage unit structure

[0046] As another embodiment, the cold storage unit can also be an integral insulation container, which is divided into three independent cold storage chambers (11, 12, 13 respectively) by insulation partitions. The cold exchange pipeline 22 passes through the chambers in sequence. Small passages are opened at the bottom of the partitions between the chambers (i.e. restricted flow structure) to achieve static pressure balance. The coil of the heat exchange pipeline 3 is also arranged in the chambers in sequence. Its working principle is exactly the same as that of the embodiment 1.

[0047] It should be noted that the above embodiments are only used to illustrate the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and not to limit the protection scope of the present application. Any equivalent changes or modifications made in accordance with the spirit and essence of the present application, such as the increase or decrease of the number of cold storage units, the replacement of the type of cold storage medium (such as the use of phase change material), the slight adjustment of the control logic, the specific winding form change of the cold / heat exchange pipeline, etc. should be covered within the protection scope of the present application.

Claims

1. A multi-stage counter-current gradient cold storage heat exchange system, characterized in that, include: At least two cold storage units are connected in series, and each cold storage unit is encapsulated with a cold storage medium; The cold exchange pipeline, which is the evaporator part of the refrigeration circuit, flows in series through the at least two cold storage units to exchange the cold energy of the refrigerant to the cold storage medium. A heat exchange pipeline, which passes through the at least two cold storage units in sequence, is used to supply the fluid to be cooled and exchanges heat with the cold storage medium through the pipe wall when flowing through each cold storage unit; The overall flow direction of the fluid to be cooled in the heat exchange pipeline is opposite to the overall flow direction of the refrigerant in the cold exchange pipeline. The system is configured such that, under the operating state of continuous output of cooling fluid, the temperature of the cold storage medium in the preceding cold storage unit along the refrigerant flow direction is lower than that in the subsequent cold storage unit, thereby forming and maintaining a temperature gradient for countercurrent heat exchange between the at least two cold storage units. Along the refrigerant flow direction, the volume of the preceding cold storage unit is less than or equal to the volume of the following cold storage unit; The volume of the first cold storage unit along the refrigerant flow direction is configured to hold only the amount of cold storage medium equivalent required to cool a single unit of the maximum preset flow rate of the fluid to be cooled from the initial temperature to the target temperature; or the total volume of the second and subsequent cold storage units is significantly greater than the volume of the first cold storage unit.

2. The multi-stage counter-current gradient cold storage heat exchange system according to claim 1, characterized in that, The at least two cold storage units are physically independent sealed containers, or independent chambers separated by a thermal insulation structure within a shared container.

3. The multi-stage counter-current gradient cold storage heat exchange system according to claim 2, characterized in that, Adjacent cold storage units are connected by a restricted flow structure, the cross-sectional area of ​​which is configured to allow static pressure balance between adjacent units, but suppress convection circulation caused by density difference that could significantly disrupt the temperature gradient.

4. The multi-stage counter-current gradient cold storage heat exchange system according to any one of claims 1 to 3, characterized in that, It also includes a control unit and a first temperature sensor; the first temperature sensor is disposed in the first cold storage unit along the refrigerant flow direction and is used to detect the temperature of its cold storage medium; the control unit is communicatively connected to the first temperature sensor and the refrigeration circuit and is configured to: control the operation of the refrigeration circuit according to the temperature feedback in the first cold storage unit, so that the temperature of the cold storage medium in the cold storage unit is maintained within a target temperature range higher than its freezing point.

5. The multi-stage counter-current gradient cold storage heat exchange system according to claim 4, characterized in that, The system is configured such that when the temperature of the cold storage medium in the first cold storage unit reaches a first preset threshold, it can output a cooling fluid with a preset temperature through the heat exchange pipeline without waiting for the other cold storage units to reach the first preset threshold.

6. The system according to claim 4, characterized in that, During steady-state operation with continuous output of cooling fluid, the temperature fluctuation of the cold storage medium in the preceding cold storage unit along the refrigerant flow direction is smaller than that in the subsequent cold storage unit.

7. A control method for a multi-stage countercurrent gradient cold storage heat exchange system as described in any one of claims 1 to 6, characterized in that, The method includes: Start the refrigeration circuit so that the refrigerant flows sequentially through the cold exchange pipeline in the first direction; When cooling fluid needs to be output, the fluid to be cooled flows through the heat exchange pipeline in a second direction opposite to the first direction. The operation of the refrigeration circuit is controlled such that during the continuous output of cooling fluid, the temperature of the cold storage medium in the preceding cold storage unit along the first direction is lower than that in the subsequent cold storage unit, thereby forming and maintaining a temperature gradient for countercurrent heat exchange between the at least two cold storage units.

8. A beverage machine, comprising a beverage mixing component, characterized in that, The beverage machine integrates a multi-stage counter-current gradient cold storage heat exchange system as described in any one of claims 1 to 7, wherein the outlet end of the heat exchange pipeline of the system is connected to the beverage mixing assembly for providing cooling fluid to the beverage mixing assembly.

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