A heat shock flash evaporation loop up-film heat exchange method
By using the thermally stimulated flash evaporation circulating rising film heat exchange method, the thermally stimulated pressure surge and the kinetic energy of throttling flash evaporation drive the liquid to form a circular flow, which solves the operating difficulties of rising film heat exchangers under narrow temperature difference conditions and achieves efficient and stable heat transfer and low energy consumption rising film heat exchange effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- TIANJIN LEKE ENERGY SAVING TECH CO LTD
- Filing Date
- 2026-04-28
- Publication Date
- 2026-06-19
AI Technical Summary
In energy-saving process systems such as MVR and heat pumps, conventional rising film heat exchangers are difficult to operate effectively under narrow temperature difference conditions, resulting in problems such as excessively long preheating sections, insufficient vaporization rate, difficulty in liquid film formation, and stagnant flow patterns in the tubes, which are either bubbly or slug-like, making it difficult to generate annular flow.
The thermally stimulated flash evaporation circulating rising film heat exchange method is adopted. Through thermally increased pressure storage, throttling flash kinetic energy release and kinetic energy drive, high-temperature live steam is used to heat the feed liquid to a high-pressure saturated state. Then, the steam is throttled to the rising film heat exchanger to form a vapor-liquid two-phase flow energy, which drives the feed liquid to climb the film along the heat exchange tube wall to form a uniform liquid film in a ring flow state.
It achieves efficient and stable operation under narrow temperature difference conditions, improves the heat transfer coefficient by more than 30%, avoids local dry wall and coking problems of heat exchange tubes, reduces the consumption of high-grade energy in the system, and is compatible with energy-saving technologies such as MVR and heat pump.
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Figure CN122230353A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of rising film heat exchange technology, and more specifically to a thermally stimulated flash evaporation circulating rising film heat exchange method. Background Technology
[0002] Rising film heat exchange is a highly efficient in-tube phase change heat transfer technology. Its principle involves using high-speed steam generated by material evaporation to drive the liquid along the inner wall of the heat exchange tube, forming a uniform, ultra-thin liquid film that rises upwards. By reducing the thickness of the liquid film, the thermal resistance is lowered, thereby enhancing heat transfer. Rising film heat exchange is widely used in the processing of low-viscosity, heat-sensitive, and easily foaming materials due to its short material residence time, high heat transfer efficiency, and compact equipment structure. A conventional rising film heat exchange process sequentially goes through five stages: single-phase liquid flow, bubbly flow, slug flow, annular flow, and mist flow. The annular flow stage is the core stage for achieving high-efficiency heat transfer; in this stage, the vapor phase is a continuous phase, and the liquid phase is an ultra-thin liquid film rising along the wall, reaching peak heat transfer efficiency.
[0003] To achieve sufficient driving force for rising film heat exchangers, conventional rising film heat exchangers require high heat flux density input under a large heat transfer temperature difference. This forces the liquid in the inlet section of the heat exchanger to vaporize rapidly, gradually increasing the vapor velocity inside the tubes and driving the flow pattern from single-phase liquid flow, bubbly flow, and slug flow to annular flow. The heat transfer temperature difference requirement for conventional rising film heat exchangers is generally not lower than 20°C. However, in energy-saving processes such as MVR and heat pumps, the heat transfer temperature difference provided by the energy-saving system is generally not higher than 10°C due to the increased boiling point of the liquid and the limitation of the compressor's ultimate pressure ratio. When the heat exchanger operates under this narrow temperature difference condition, problems such as excessively long preheating section, insufficient vaporization rate, difficulty in liquid film formation, and the flow pattern inside the tubes remaining in bubbly or slug flow, making it difficult to generate annular flow, will occur, and the heat exchanger will be unable to achieve effective rising film heat exchange operation. Summary of the Invention
[0004] The present invention aims to provide a thermally stimulated flash evaporation circulating rising film heat exchange method to overcome the shortcomings of the prior art. The technical problem to be solved by the present invention is achieved through the following technical solution.
[0005] A thermally stimulated flash evaporation circulating rising film heat exchange method includes the following steps: S1, Thermal Shock Pressure Storage: The feed liquid is pressurized and sent to the thermal shock heater. High-temperature live steam heats the feed liquid to a high-pressure saturation state, completing the storage of high-temperature thermal energy into the internal energy of the feed liquid. At this time, the temperature of the feed liquid is the thermal shock completion temperature. T j ; S2, throttling flash kinetic energy release; allows high-pressure saturated material to flow through the throttling component, reducing the pressure of the high-pressure saturated material to the evaporation pressure of the rising film heat exchange. P zThe liquid undergoes isenthalpic flash evaporation, converting the internal energy of the liquid into the flow energy of the vapor-liquid two-phase flow. S3, Kinetic Energy Driven Rising Film Heat Exchange: After the high-kinetic-energy vapor-liquid two-phase flow is evenly distributed, it is sent into the heat exchange tube of the rising film heat exchanger. The expansion kinetic energy of the flash vapor drives the liquid to climb along the heat exchange tube wall to form a uniform liquid film in an annular flow state. S4, Vapor-Liquid Separation and Discharge: The vapor-liquid mixture after rising film heat exchange is sent to the vapor-liquid separator for vapor-liquid separation. The separated vapor is heat recovered, and the concentration of the unevaporated liquid phase is detected. The qualified portion is collected, and the unqualified portion is repeated in S1~S4.
[0006] Preferably, in S3, the heat source of the rising film heat exchanger is a low-grade heat source that is 5-10°C higher than the temperature of the feed liquid.
[0007] Preferably, the thermal shock completion temperature in S1 is greater than the evaporation temperature of the rising film heat exchanger in S3.
[0008] Preferably, in S1, the thermal shock completion temperature of the material after passing through the thermal shock heater is... T j Should meet: , in, T j The thermal shock completion temperature is expressed in °C. T z The evaporation temperature of the rising film heat exchanger is expressed in °C. γ The latent heat of vaporization of the liquid feed is expressed in kJ / kg. Cp Specific heat of the liquid feed, expressed in kJ / (kg·℃); A The cross-sectional area of the heat exchanger tubes in a rising film heat exchanger is expressed in m². 2 ; ρ s Evaporation temperature T z The steam density at that time is expressed in kg / m³. 3 ; m This represents the feed rate to the heat exchanger, expressed in kg / s.
[0009] Preferably, in S3, the feed rate of the rising film heat exchanger... m Should meet: , in, T j The thermal shock completion temperature is expressed in °C. T z The evaporation temperature of the rising film heat exchanger is expressed in °C. γ The latent heat of vaporization of the liquid feed is expressed in kJ / kg. ρs Evaporation temperature T z The steam density at that time is expressed in kg / m³. 3 ; ρ L Evaporation temperature T z The liquid phase density at that time is expressed in kg / m³. 3 ; Cp Specific heat of the liquid feed, expressed in kJ / (kg·℃); A The cross-sectional area of the heat exchanger tubes in a rising film heat exchanger is expressed in m². 2 ; m This represents the feed rate to the heat exchanger, expressed in kg / s.
[0010] Preferably, in S3, the apparent vapor velocity of the rising film heat exchanger must satisfy the following formula: , in, ρ s Evaporation temperature T z The steam density at that time is expressed in kg / m³. 3 ; J s The apparent vapor velocity of the rising film heat exchanger is expressed in m / s.
[0011] Preferably, in S3, the apparent liquid velocity of the rising film heat exchanger must satisfy the following formula: , in, ρ L Evaporation temperature T z The liquid phase density at that time is expressed in kg / m³. 3 ; J L The apparent liquid velocity of the rising film heat exchanger is expressed in m / s.
[0012] The thermal flash evaporation circulating rising film heat exchange method provided by this invention has the following beneficial effects: 1) This invention proposes for the first time a thermal flash evaporation phase change energy driven rising film heat exchange method, breaking the inherent technology of traditional rising film heat exchange that relies on large heat transfer temperature difference. It couples the energy conversion process of thermal energy, internal energy and kinetic energy with rising film heat exchange. By adjusting the parameter matching relationship, it solves the problem of the kinetic energy source of rising film heat exchange under narrow temperature difference conditions. The rising film heat transfer temperature difference is reduced from the traditional not less than 20℃ to less than 10℃.
[0013] 2) This invention employs an independent kinetic energy pre-generation step, directly propelling the flow pattern within the tube into a highly efficient annular flow stage through the throttling and flash expansion of the thermally stimulated liquid, skipping inefficient flow patterns such as single-phase liquid flow, bubbly flow, and slug flow. Compared to traditional rising film heat exchange systems, the thermally stimulated flash annular rising film heat transfer coefficient of this invention can be increased by more than 30%, while the uniform distribution of the annular liquid film also avoids problems such as localized dry walls and coking in the heat exchange tubes.
[0014] 3) This invention achieves precise control of the parameters of thermally stimulated flash evaporation circulating rising film by clearly defining the quantitative relationship between the thermal stimulating temperature and the feed rate. It eliminates the need for a forced circulation pump to provide additional kinetic energy, and can directly utilize clean energy sources such as industrial preheating and low-grade heat sources. It is compatible with energy-saving processes such as MVR and heat pumps, significantly reducing the high-grade energy consumption of the rising film heat exchange system. Attached Figure Description
[0015] Figure 1 This is a flowchart of the present invention; Figure 2 Here is a pressure-enthalpy diagram of the post-circulation of the feed liquid in this embodiment of the invention; wherein, a→b is the thermal surge pressure storage process, b→c is the throttling flash kinetic energy release process, a→d is the feed evaporation process of the traditional rising film technology; point c is the inlet state point of the rising film heat exchanger, and point d is the inlet state point of the traditional rising film heat exchanger. Figure 3 This is a schematic diagram of the flow pattern inside a rising film heat exchanger tube according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the flow pattern inside the rising film heat exchanger tube in the traditional rising film heat exchange method of this invention. Detailed Implementation
[0016] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.
[0017] Example 1: A thermal flash evaporation circulating rising film heat transfer method, referring to Figure 1 As shown, it includes the following steps: S1, Thermal Shock Pressure Storage: The feed liquid is pressurized and sent to the thermal shock heater. High-temperature live steam heats the feed liquid to a high-pressure saturation state, completing the storage of external high-temperature thermal energy into the internal energy of the feed liquid. At this time, the temperature of the feed liquid is the thermal shock completion temperature. T j Unlike conventional rising film technology for material preheating, the thermal shock heating in this embodiment should be completed at a temperature greater than the evaporation point of the liquid, with the liquid pressure greater than the evaporation pressure, and the liquid in a supercooled or saturated state under high pressure.
[0018] S2, throttling flash kinetic energy release; allows the high-pressure saturated material after thermal shock to flow through the throttling component, reducing the pressure of the high-pressure saturated material to the evaporation pressure of the rising film heat exchange. P z The feed liquid undergoes isenthalpic flash evaporation, converting its internal energy into the latent heat of vaporization of the flashed gas after throttling. This is accompanied by rapid expansion of the vapor-liquid two-phase flow volume after throttling, further converting the feed liquid's internal energy into the flow energy of the vapor-liquid two-phase flow. In this embodiment, the pressure after throttling is the feed liquid evaporation pressure of the rising film heat exchanger. P z This is to ensure that the throttled liquid is in a vapor-liquid two-phase state.
[0019] S3, kinetic energy driven rising film heat exchange: A high-kinetic-energy vapor-liquid two-phase flow is uniformly distributed and fed into the heat exchange tubes of the rising film heat exchanger. The kinetic energy of the flash vapor expansion drives the liquid to climb along the tube wall, forming a uniform liquid film in an annular flow state. The heat required for rising film evaporation within the heat exchange tubes is supplied by a low-grade heat source. This low-grade heat source only provides heating for phase change evaporation in the rising film heat exchanger and does not contribute to the thermal drive of the flow pattern within the tubes.
[0020] S4, Vapor-liquid separation discharge: The vapor-liquid mixture after rising film heat exchange is sent to a vapor-liquid separator, where it is separated by gravity settling or a demister. The separated secondary steam enters a heat pump or other system for heat recovery. The unevaporated liquid phase is tested for concentration, and the qualified portion is collected. The unqualified portion is repeated after S1~S4.
[0021] Furthermore, in S3, the heat source of the rising film heat exchanger is a low-grade heat source that is 5-10°C higher than the temperature of the feed liquid.
[0022] Furthermore, the thermal shock completion temperature in S1 is greater than the evaporation temperature of the rising film heat exchanger in S3.
[0023] Furthermore, in S1, the temperature at which the material completes the thermal shock process after passing through the thermal shock heater is... T j Should meet: (7), in, T j The thermal shock completion temperature is expressed in °C. T z The evaporation temperature of the rising film heat exchanger is expressed in °C. γ The latent heat of vaporization of the liquid feed is expressed in kJ / kg. Cp Specific heat of the liquid feed, expressed in kJ / (kg·℃); A The cross-sectional area of the heat exchanger tubes in a rising film heat exchanger is expressed in m². 2 ; ρ s Evaporation temperature Tz The steam density at that time is expressed in kg / m³. 3 ; m This represents the feed rate to the heat exchanger, expressed in kg / s.
[0024] Furthermore, in S3, the feed rate of the rising film heat exchanger... m Should meet: (9), in, T j The thermal shock completion temperature is expressed in °C. T z The evaporation temperature of the rising film heat exchanger is expressed in °C. γ The latent heat of vaporization of the liquid feed is expressed in kJ / kg. ρ s Evaporation temperature T z The steam density at that time is expressed in kg / m³. 3 ; ρ L Evaporation temperature T z The liquid phase density at that time is expressed in kg / m³. 3 ; Cp Specific heat of the liquid feed, expressed in kJ / (kg·℃); A The cross-sectional area of the heat exchanger tubes in a rising film heat exchanger is expressed in m². 2 ; m This represents the feed rate to the heat exchanger, expressed in kg / s.
[0025] Furthermore, in S3, the apparent vapor velocity of the rising film heat exchanger must satisfy the following formula: (6), in, ρ s Evaporation temperature T z The steam density at that time is expressed in kg / m³. 3 ; J s The apparent vapor velocity of the rising film heat exchanger is expressed in m / s.
[0026] Furthermore, in S3, the apparent liquid velocity of the rising film heat exchanger must satisfy the following formula: (8), in, ρ L Evaporation temperature T z The liquid phase density at that time is expressed in kg / m³. 3 ; JL The apparent liquid velocity of the rising film heat exchanger is expressed in m / s.
[0027] Furthermore, in S2, the throttling pressure drop Δ of the throttling component P satisfy: (1), in, P j The pressure of the feed liquid after thermal shock is expressed in bar. P z This represents the evaporation pressure of the liquid feed, expressed in bar.
[0028] Furthermore, in S2, the mass flow rate of flash vapor... m s and volumetric flow rate V s They are respectively: (2), (3), Furthermore, in S3, the apparent steam velocity at the inlet of the rising film heat exchanger... J s and apparent fluid velocity J L They are respectively: (4), (5).
[0029] This embodiment provides a thermally stimulated flash evaporation circulating rising film heat exchange method. Through the synergistic effect of thermally stimulated pressure storage and throttling flash kinetic energy release, the rapidly expanding vapor-liquid mixture after the thermally stimulated liquid undergoes throttling flash evaporation directly drives the circulating rising film operation inside the heat exchange tube. This breaks the dependence of traditional rising film heat exchange on large temperature differences and achieves efficient and stable operation under narrow temperature difference conditions.
[0030] Example 2: Based on Example 1, this example takes ethanol evaporation as an example, and the feed rate of the heat exchanger... m The flow rate is 2.78 kg / s, and the ethanol feed temperature is 70°C. Ethanol undergoes atmospheric pressure evaporation in a rising film heat exchanger, with an evaporation temperature of... T z The temperature is 78℃ and the evaporation pressure is... P z The latent heat of vaporization of ethanol at 78°C is 1 bar (a). γ It is 855 kJ / kg, and its saturated steam density is... ρ s It is 1.579 kg / m 3 ethanol solution density ρ L735 kg / m 3 Specific heat of ethanol solution Cp The total cross-sectional area of the flow channel of the rising film heat exchanger tubes is 3.2 kJ / (kg·℃). A It is 0.0025m 2 The thermal shock heating uses 120°C live steam, while the rising film heat exchanger uses 85°C low-pressure steam for heating and evaporation.
[0031] Reference Figure 1 , Figure 2 As shown, the ethanol thermal flash evaporation circulating rising film heat exchange method in this embodiment includes four steps: thermal surge pressure storage, throttling flash kinetic energy release, kinetic energy-driven rising film heat exchange, and vapor-liquid separation and discharge.
[0032] S1: Thermal surge pressure storage stage, this stage corresponds to Figure 2 The process a→b in the figure. After pressurizing, the ethanol solution is sent to the heater, and the ethanol solution with a flow rate of 2.78 kg / s is heated by 120°C live steam to complete the storage of high-temperature thermal energy into the internal energy of the liquid. According to formula (7), the thermal shock completion temperature of this embodiment should meet the following requirements. T j ≥81℃, the thermal shock completion temperature determined in this embodiment. T j The temperature is 90℃, and the corresponding pressure for heat shock completion is 1.58 bar (a). The ethanol solution is heated from 70℃ to 90℃, the heat shock heating load of the liquid is 179kW, and the consumption of live steam (120℃) for heat shock heating is 280kg / h.
[0033] S2: Throttling flash kinetic energy release, this stage corresponds to Figure 2 The process from b to c is described. A saturated ethanol solution at 1.58 bar flows through a throttling device to reduce its pressure to 1 bar (a) of the rising film heat exchanger. The throttling of the ethanol solution is an isenthalpic flash evaporation process, accompanied by rapid expansion of the liquid and vapor phases. After throttling, the 2.78 kg / s ethanol solution produces 0.125 kg / s flash vapor. In the vapor-liquid mixture after throttling, the mass ratio of ethanol vapor is 4.49%, and the volume fraction of ethanol vapor is 95.6%. The volume of the vapor-liquid mixture after throttling is 21.9 times that before throttling. This process converts the internal energy accumulated in the liquid during stage S1 into the expansion kinetic energy of the liquid and vapor phases.
[0034] S3: Kinetic energy drives the rising film heat exchanger; the ethanol vapor-liquid mixture, after throttling, expands 21.9 times in volume before entering the rising film heat exchanger; For example... Figure 3As shown, the expansion kinetic energy of the flash vapor after throttling in step S2 drives the ethanol solution to climb the film along the heat exchanger tube wall, directly forming a circulating liquid film. The apparent vapor velocity at the inlet of the rising film heat exchanger is 31.6 m / s, and the apparent liquid velocity is 1.44 m / s. In this stage, low-pressure steam at 85℃ is used to heat the rising film heat exchanger. The ethanol evaporation rate and the heat load of the rising film heat exchanger are 2254 kW, the heat transfer temperature difference of the rising film heat exchanger is 7℃, and the consumption of low-pressure steam (85℃) is 3522 kg / h.
[0035] S4: Vapor-liquid separation and discharge. The vapor-liquid mixture after rising film heat exchange enters the vapor-liquid separator, where efficient vapor-liquid separation is achieved through gravity settling or demister. Secondary steam can be recovered through heat pumps and other systems. Unevaporated ethanol solution is returned to S1, and steps S1 to S4 are repeated for continued evaporation.
[0036] Comparative example a: This comparative example uses a traditional rising film heat exchange method for the evaporation of an ethanol solution. Comparative example a illustrates the traditional rising film heat exchange method and its specific steps. (The feed rate to the heat exchanger is not specified.) m The flow rate is 2.78 kg / s, and the ethanol feed temperature is 70°C. Ethanol undergoes atmospheric pressure evaporation in a rising film heat exchanger, with an evaporation temperature of... T z The temperature is 78℃ and the evaporation pressure is... P z The heat source for the rising film heat exchanger is 1 bar (a); the heat source is live steam at 120°C.
[0037] S101, Material preheating stage; this stage corresponds to the pressure-enthalpy of the circulating liquid. Figure 2 The process is a→d. The ethanol solution is pumped into the preheater through a circulating pump. The ethanol solution is preheated to the bubble point of 78°C by live steam at 120°C. The heat load of the preheater is 69.5kW and the consumption of live steam (120°C) is 109kg / h.
[0038] S201, Rising Film Evaporation Stage: The preheated ethanol solution to its bubble point is supplied to the rising film heat exchanger, which is heated by 120°C live steam. The ethanol solution evaporates at atmospheric pressure at an evaporation temperature of 78°C. Figure 4 As shown, the ethanol solution at the inlet of the heat exchange tube undergoes nucleus boiling upon heating. Numerous tiny bubbles are generated and detach from the vaporization nuclei on the tube wall, forming a bubbly flow. With continuous heat input, small bubbles continuously converge and merge into larger bubbles, and the ethanol liquid phase is squeezed against the tube wall to form a liquid plug. The vapor and liquid phases alternately advance forward, and the flow pattern transforms into a slug flow. Subsequently, the slug bubbles burst and merge to form a continuous vapor column, dragging the ethanol liquid phase along the inner wall of the heat exchange tube to climb the film and form an annular flow. In this process, the heat load of the rising film heat exchanger is 2364 kW, and the consumption of live steam (120℃) is 3694 kg / h.
[0039] The main technical parameters of Comparative Example a and Example 2 are compared in the table below: Table 1
[0040] As shown in Table 1, compared to traditional rising film heat exchange methods, the thermally stimulated flash evaporation circulating rising film heat exchange method of this invention, through a pre-energized kinetic energy supply mode of thermally induced pressure storage and throttling flash evaporation kinetic energy release, directly forms a gas-liquid two-phase flow with a high vapor-to-liquid ratio at the inlet of the rising film heat exchanger. This achieves a one-step transition to a highly efficient circulating flow, completely skipping the inefficient flow stages of single-phase liquid flow, bubbly flow, and slug flow, thus improving the heat transfer performance of the heat exchanger by more than 30%. The circulating rising film configuration does not rely on the heat source for heating the rising film heat exchanger itself; only a low-grade heat source with a narrow temperature difference of 7°C is needed to maintain the stable operation of the rising film heat exchanger. The high-temperature live steam consumption of this invention is only 7.4% of that of traditional technologies, significantly reducing system energy consumption.
[0041] Example 3: Based on Example 1, this example specifies the thermal excitation completion temperature of the heat exchanger. T j The document then explains how to determine the feed rate range for the rising film heat exchanger.
[0042] This embodiment uses the concentration of a 5% sodium chloride aqueous solution as an example. The solution feed temperature is 80℃, the heat shock completion temperature is 100℃, and the rising film evaporation temperature is... T z At 85℃, the evaporation pressure P z The latent heat of vaporization of water at 85°C is 0.58 bar (a) and the discharge concentration is 10%. γ It is 2294 kJ / kg, and the saturated water vapor density is... ρ s It is 0.352 kg / m 3 Density of sodium chloride solution ρ L 1010 kg / m 3 Specific heat of solution Cp The total cross-sectional area of the flow channel of the rising film heat exchanger tubes is 3.95 kJ / (kg·℃). A It is 0.00037m 2 The thermal shock heating uses 120℃ live steam, and the heating source for the rising film heat exchanger uses 90℃ low-pressure steam.
[0043] The sodium chloride aqueous solution thermal flash evaporation circulating rising film heat exchange method of this embodiment includes four steps: thermal surge pressure storage, throttling flash kinetic energy release, kinetic energy driven rising film heat exchange, and vapor-liquid separation and discharge.
[0044] S1, thermal surge pressure storage: Sodium chloride at 80°C is pressurized by a booster pump and sent to the heater. The solution is heated to 100°C by live steam at 120°C. The corresponding thermal shock completion pressure is 1 bar (a), completing the storage of high-temperature thermal energy into the internal energy of the liquid. The feed rate of the thermal shock flash circulating rising film heat exchanger is calculated according to equation (9). m The range is 0.381 kg / s ≥ m ≥ 0.085 kg / s, thus determining the feed rate of this embodiment to be 0.35 kg / s.
[0045] In S2, the kinetic energy of flash evaporation is released through throttling. The sodium chloride solution at 100°C is depressurized to an evaporation pressure of 0.578 bar(a). This throttling is an isenthalpic flash evaporation process, accompanied by a rapid expansion of the vapor-liquid mixture after throttling. A 0.35 kg / s sodium chloride solution produces 0.009 kg / s of flash steam after throttling. The mass percentage of water vapor in the vapor-liquid mixture after throttling is 2.58%, and the volume fraction is 98.7%. The volume of the vapor-liquid mixture after throttling is 75.2 times that before throttling. This process converts the internal energy accumulated in stage S1 into the expansion kinetic energy of the vapor-liquid two-phase system.
[0046] In step S3, kinetic energy drives the rising film heat exchanger. The vapor-liquid mixture, after throttling, expands in volume and is introduced into the rising film heat exchanger. The kinetic energy of the flash vapor expansion after throttling in step S2 drives the sodium chloride solution to climb the heat exchanger tube wall, directly forming a circulating liquid film. The apparent vapor velocity at the inlet of the rising film heat exchanger is 69.5 m / s, and the apparent liquid velocity is 0.91 m / s. Low-pressure steam at 90℃ is used to heat the rising film heat exchanger in this stage, and the heat transfer temperature difference of the rising film heat exchanger is 5℃.
[0047] S4, vapor-liquid separation and discharge: The vapor-liquid mixture after rising film heat exchange enters the vapor-liquid separator, where efficient separation of vapor and liquid is achieved through gravity settling. The secondary steam can be recovered through heat pumps and other systems. The concentration of the unevaporated liquid phase is detected. If the concentration reaches 10% of the preset value, it is collected. If the concentration does not reach 10%, it is returned to S1, and steps S1 to S4 are repeated for further processing.
[0048] This embodiment determines the feed rate range of the rising film heat exchanger by fixing the thermal shock completion temperature and using a given method. High-kinetic-energy vapor-liquid two-phase flow is generated through thermal shock flash evaporation. The inlet gas volume fraction of the rising film heat exchanger is 98.7%, which can directly drive the formation of a stable annular flow pattern. The rising film heat exchanger only requires a narrow temperature difference and low-grade heat source of 5°C to maintain efficient heat exchange.
[0049] It should be noted that the above detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.
[0050] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments described in this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.
[0051] It should be noted that the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.
[0052] Furthermore, the terms “comprising” and “having”, and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or apparatus.
[0053] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways, such as rotated 90 degrees or in other orientations, and the spatial relative descriptions used herein will be interpreted accordingly.
[0054] In the detailed description above, reference has been made to the accompanying drawings, which form part of this document. In the drawings, similar symbols typically identify similar parts unless the context otherwise indicates otherwise. The illustrated embodiments described in the detailed specification, drawings, and claims are not intended to be limiting. Other embodiments may be used and other changes may be made without departing from the spirit or scope of the subject matter presented herein.
[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A thermally stimulated flash evaporation circulating rising film heat transfer method, characterized in that: Includes the following steps: S1, Thermal Shock Pressure Storage: The feed liquid is pressurized and sent to the thermal shock heater. High-temperature live steam heats the feed liquid to a high-pressure saturation state, completing the storage of high-temperature thermal energy into the internal energy of the feed liquid. At this time, the temperature of the feed liquid is the thermal shock completion temperature. T j ; S2, throttling flash kinetic energy release; allows high-pressure saturated material to flow through the throttling component, reducing the pressure of the high-pressure saturated material to the evaporation pressure of the rising film heat exchange. P z The liquid undergoes isenthalpic flash evaporation, converting the internal energy of the liquid into the flow energy of the vapor-liquid two-phase flow. S3, Kinetic Energy Driven Circulating Rising Film Heat Exchange: After the high-kinetic-energy vapor-liquid two-phase flow is evenly distributed, it is sent into the heat exchange tube of the rising film heat exchanger. The expansion kinetic energy of the flash vapor drives the liquid to climb along the heat exchange tube wall to form a uniform liquid film in a ring-shaped flow state. S4, Vapor-Liquid Separation and Discharge: The vapor-liquid mixture after rising film heat exchange is sent to the vapor-liquid separator for vapor-liquid separation. The separated vapor is heat recovered, and the concentration of the unevaporated liquid phase is detected. The qualified portion is collected, and the unqualified portion is repeated in S1~S4.
2. The thermal flash evaporation circulating rising film heat exchange method according to claim 1, characterized in that: In S3, the heat source of the rising film heat exchanger is a low-grade heat source that is 5~10℃ higher than the temperature of the feed liquid.
3. The thermal flash evaporation circulating rising film heat exchange method according to claim 1, characterized in that: The thermal shock completion temperature in S1 is higher than the evaporation temperature of the rising film heat exchanger in S3.
4. The thermal flash evaporation circulating rising film heat exchange method according to claim 1, characterized in that: In S1, the thermal shock completion temperature of the material after passing through the thermal shock heater T j It should meet the following requirements: ， in, T j The thermal shock completion temperature is expressed in °C. T z The evaporation temperature of the rising film heat exchanger is expressed in °C. γ The latent heat of vaporization of the liquid feed is expressed in kJ / kg. Cp Specific heat of the liquid feed, expressed in kJ / (kg·℃); A The cross-sectional area of the heat exchanger tubes in a rising film heat exchanger is expressed in m². 2 ; ρ s Evaporation temperature T z The steam density at that time is expressed in kg / m³. 3 ; m This represents the feed rate to the heat exchanger, expressed in kg / s.
5. The thermal flash evaporation circulating rising film heat exchange method according to claim 4, characterized in that: In S3, the feed rate of the rising film heat exchanger m It should meet the following requirements: ， in, T j The thermal shock completion temperature is expressed in °C. T z The evaporation temperature of the rising film heat exchanger is expressed in °C. γ The latent heat of vaporization of the liquid feed is expressed in kJ / kg. ρ s Evaporation temperature T z The steam density at that time is expressed in kg / m³. 3 ; ρ L Evaporation temperature T z The liquid phase density at that time is expressed in kg / m³. 3 ; Cp Specific heat of the liquid feed, expressed in kJ / (kg·℃); A The cross-sectional area of the heat exchanger tubes in a rising film heat exchanger is expressed in m². 2 ; m This represents the feed rate to the heat exchanger, expressed in kg / s.
6. The thermal flash evaporation circulating rising film heat exchange method according to claim 5, characterized in that: In S3, the apparent vapor velocity of the rising film heat exchanger must satisfy the following formula: ， in, ρ s Evaporation temperature T z The steam density at that time is expressed in kg / m³. 3 ; J s The apparent vapor velocity of the rising film heat exchanger is expressed in m / s.
7. The thermal flash evaporation circulating rising film heat exchange method according to claim 6, characterized in that: In S3, the apparent liquid velocity of the rising film heat exchanger must satisfy the following formula: ， in, ρ L Evaporation temperature T z The liquid phase density at that time is expressed in kg / m³. 3 ; J L The apparent liquid velocity of the rising film heat exchanger is expressed in m / s.