Sensor-carrying gas-based falling-film heat exchanger test control method and system

Abstract

The application provides a sensor carrier gas-based falling-film heat exchanger test control method and system, which is compact in structure, convenient to operate, low in operation cost and reliable in performance. The heat transfer film coefficients are compared in two cases of no introduction and introduction of carrier gas, the heat transfer performance of the carrier gas-based falling-film heat exchanger and the falling-film heat exchanger is compared, the carrier gas can be an external gas or a gas evaporated from a liquid, and the heat exchanger tube wall temperature can be tested. Test results show that the heat transfer film coefficient of the carrier gas-based falling-film heat exchanger is obviously improved, the wall temperature and the liquid film surface temperature are reduced, the residence time of the liquid film on the heating tube wall is reduced, and the liquid film distribution is more uniform. The operation conditions of the carrier gas-based falling-film heat exchanger in the vertical tube under various working conditions in actual industrial production are accurately simulated, and the heat transfer performance of the optimized heat transfer element of the heat exchanger is compared and tested, thereby providing a theoretical basis for design.

Description

Technical Field

[0001] This invention relates to the field of thermal experimental equipment technology, specifically to a test and control method and system for a sensor-based carrier gas falling film heat exchanger. Background Technology

[0002] Falling film heat exchangers are a widely used technology in heat exchange equipment, especially exhibiting significant advantages in liquid-gas two-phase flow heat exchange processes. Compared to traditional tubular heat exchangers, falling film heat exchangers offer a larger heat exchange area and higher heat exchange efficiency, and are widely used in various industries such as chemical, pharmaceutical, food, air conditioning, and environmental protection. In practical engineering, falling film heat exchangers not only require good thermal conductivity but also stable fluid distribution to ensure high efficiency and reliability of heat exchange.

[0003] Although falling film heat exchangers are widely used in various industrial applications, they still face some technical challenges in actual operation. First, the stability and uniformity of the liquid film are key factors affecting heat exchange efficiency. During flow, the liquid film is easily affected by external disturbances, such as unstable airflow and temperature variations, leading to a decrease in heat exchange performance. Furthermore, the thickness of the liquid film directly impacts heat exchange efficiency; an excessively thick film may increase thermal resistance, while an excessively thin film may result in insufficient heat exchange.

[0004] Secondly, most traditional falling film heat exchangers rely on empirical formulas and conventional operating parameters (such as flow rate, temperature, and pressure) for control and regulation, lacking real-time monitoring and intelligent control systems. This makes it difficult to dynamically optimize according to changes in operating conditions during actual use, resulting in performance fluctuations of the heat exchanger under different operating conditions, reducing energy utilization efficiency and system stability.

[0005] With the increasing automation and intelligence of industry, sensor-based real-time testing and control methods are gradually becoming an effective way to improve the performance of falling film heat exchangers. By introducing various sensors (such as flow sensors, temperature sensors, pressure sensors, and liquid film thickness sensors) into the falling film heat exchanger, comprehensive monitoring and control of the heat exchanger's operating status can be achieved. Especially in cases involving carrier gas flow control, precise control of changes in carrier gas flow can effectively regulate the stability of the liquid film and optimize the heat exchange process. However, most related technologies still have some shortcomings, particularly in how to effectively combine carrier gas flow and liquid film characteristics for closed-loop control. Summary of the Invention

[0006] This invention addresses the problems of existing technologies by providing a test and control method and system for a sensor-based carrier gas falling film heat exchanger. A small amount of inert gas is introduced into the heating tube as a carrier gas, altering the boiling mechanism and transforming the boiling process on the heating wall into an evaporation process at the gas-liquid interface. Due to the increased bubble agitation and circulation speed, the overall heat transfer coefficient can be increased by 30-60%, while simultaneously reducing wall superheat. This reduces and suppresses the possibility of material overheating, deterioration, and scaling on the heating wall.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] The first aspect of this invention discloses a sensor-based carrier gas falling film heat exchanger test and control system, including a carrier gas pipeline unit, a steam pipeline unit, a test heat exchange unit, a liquid circulation unit, a condensate treatment unit, and a data measurement and control unit. Each unit is connected to form a whole through pipelines or corresponding components.

[0009] The carrier gas pipeline unit includes a first carrier gas pipeline unit, a second carrier gas pipeline unit, and a carrier gas pipeline start / stop control unit. The first carrier gas pipeline unit includes an air compressor and a heater. The outlet of the air compressor is connected to one end of the heater, and the other end of the heater is connected to one end of a heat exchanger. The second carrier gas pipeline unit includes a gas-liquid separator and a plate heat exchanger. One end of the gas-liquid separator is connected to the heat exchanger, and the other end of the gas-liquid separator is connected to one end of the plate heat exchanger. The other end of the plate heat exchanger is connected to the heat exchanger. The carrier gas pipeline start / stop control unit includes an inlet valve / start / stop valve and a return gas regulating valve, used to switch the carrier gas mode of the first and second carrier gas pipeline units. The inlet valve / start / stop valve is located between the air compressor and the heater, used to open or close the first carrier gas pipeline unit. The return gas regulating valve is located between the plate heat exchanger and the heat exchanger, used to control the gas flow rate returning from the plate heat exchanger to the heat exchanger.

[0010] The steam pipeline unit includes a steam generator, a steam pressure tank, and a steam pipeline start / stop control unit. The outlet of the steam generator is connected to the inlet / steam outlet of the steam pressure tank, and the outlet / steam outlet of the steam pressure tank is connected to the shell-side inlet of the heat exchanger. The steam pipeline start / stop control unit includes a steam regulating valve, a shell-side inlet valve, and a safety valve / vent valve. The steam regulating valve is located between the steam pressure tank and the shell-side inlet valve and is used to control the steam flow rate and pressure entering the shell-side inlet of the heat exchanger. The shell-side inlet valve is located between the steam regulating valve and the shell-side inlet of the heat exchanger and is used to control the on / off state of steam entering the shell side of the heat exchanger. The safety valve / vent valve is located at the top of the steam pressure tank or at a high point in the steam pipeline and is used for overpressure relief or start / stop venting.

[0011] The heat exchanger in the test heat exchange unit includes a liquid feed pipe, a carrier gas inlet pipe, a downcomer half-pipe, a carrier gas pipe, a distribution plate, a falling film head, a tube sheet, heat exchange tubes, and a baffle plate, which are used for heat exchange between gas and liquid media.

[0012] The liquid circulation unit includes a liquid storage tank, a centrifugal pump, and a liquid circulation control unit. One end of the liquid storage tank is connected to one end of a gas-liquid separator and / or a plate heat exchanger, and the other end of the liquid storage tank is connected to the centrifugal pump. The liquid circulation control unit includes an inlet valve / start / stop valve and a liquid regulating valve. The inlet valve / start / stop valve is located between the liquid storage tank and the centrifugal pump and is used to control the flow rate of liquid entering the centrifugal pump and / or to start and stop it. The liquid regulating valve is located between the centrifugal pump and the heat exchanger and is used to regulate the liquid flow rate.

[0013] The condensate treatment unit includes a condensate collection tank and a condensate treatment control unit. The condensate collection tank is connected to the shell-side outlet of the heat exchanger. The condensate treatment control unit includes a shell-side outlet regulating valve and a condensate discharge valve. The shell-side outlet regulating valve is located between the condensate collection tank and the heat exchanger and is used to control condensate discharge and shell-side pressure. The discharge valve is located at the bottom of the storage tank and is used for system evacuation or cleaning. The condensate discharge valve is located between the condensate collection tank and the first metering device and is used to control periodic discharge of accumulated liquid or quantitative sampling.

[0014] The data measurement and control unit includes a first flow meter, a second flow meter, a third flow meter, a fourth flow meter, a first metering device, a differential pressure transmitter, and a temperature sensor. The first flow meter is placed in the first carrier gas pipeline unit, the second flow meter is placed in the second carrier gas pipeline unit, the third flow meter is placed in the steam pipeline unit, and the fourth flow meter is placed in the liquid circulation unit. The first metering device is connected to one end of the condensate discharge valve and is used to monitor and control the flow rate of the condensate to ensure the periodic discharge or quantitative sampling of the condensate.

[0015] According to one embodiment of the present invention, the gas-liquid separator is used to separate gas and liquid two-phase materials from the heat exchange tube, thereby completing the heat exchange of the hot and cold media and the gas-liquid separation of the cold media; the plate heat exchanger is used for gas phase condensation, and the condensate generated therefrom flows into the storage tank together with the condensate of the gas-liquid separator, while the cooled return gas is introduced into the heat exchanger.

[0016] According to one embodiment of the present invention, the data measurement and control unit further includes a sight glass, which is installed at the bottom of the heat exchanger or at the liquid phase outlet pipe section of the gas-liquid separator or at the inlet and outlet of the condensate collection tank or storage tank. The sight glass is equipped with a photoelectric sensor or an image recognition module for acquiring images of the liquid film or gas-liquid interface inside the heat exchanger, and fusing the image signal with the output signals of the flow meter and temperature sensor to form a feedback control signal to control the liquid flow rate or gas flow rate.

[0017] According to one embodiment of the present invention, the data measurement and control unit further includes a second meter, which is located between the liquid storage tank and the plate heat exchanger, and is used to monitor and control the flow rate of condensate from the liquid storage tank to the plate heat exchanger.

[0018] According to one embodiment of the present invention, the data measurement and control unit controls the opening, closing, and ready states of valves F1 to F10 based on the numerical changes of the first flow meter, second flow meter, third flow meter, fourth flow meter, first metering device, second metering device, sight glass, differential pressure transmitter, and temperature sensor, thereby completing the testing and control of the gas pipeline unit, steam pipeline unit, test heat exchange unit, liquid circulation unit, and condensate treatment unit.

[0019] According to one embodiment of the present invention, the differential pressure transmitter is respectively disposed at the shell-side inlet, shell-side outlet and tube-side carrier gas or liquid outlet of the heat exchanger, and the temperature sensor is located at the shell-side inlet, shell-side outlet, tube-side outlet and heat exchange tube wall of the heat exchanger.

[0020] The second aspect of this invention discloses a test and control method for a sensor-based carrier gas falling film heat exchanger. This method applies the aforementioned sensor-based carrier gas falling film heat exchanger test and control system, and includes testing and controlling the carrier gas pipeline unit, steam pipeline unit, test heat exchange unit, liquid circulation unit, and condensate treatment unit based on data displayed by the data measurement and control unit.

[0021] The inlet valve / start / stop valve starts the centrifugal pump, and the liquid flows through the liquid regulating valve. The size of the liquid regulating valve is controlled according to the load requirements. The liquid enters the distribution plate of the heat exchanger and flows into the tube sheet through the small holes of the distribution plate. The liquid on the tube sheet flows into the inner wall of the heat exchange tube through the film distributor, flows directly to the gas-liquid separator, and flows to the liquid storage tank. At the same time, the gas separated from the gas-liquid separator flows to the plate heat exchanger, and the gas in the plate heat exchanger flows back to the heat exchanger to complete the liquid circulation.

[0022] The liquid is dispersed into a thin liquid layer by the film distributor and flows evenly to each heat exchange tube inlet. After entering the tube inlet, the liquid forms a uniform liquid film along the inner wall of the tube under the action of gravity, improving the heat transfer coefficient. This prevents the liquid from concentrating and impacting a single tube inlet, which could lead to localized dry walls and uneven liquid flow distribution. By evenly distributing the liquid to the inner wall of each heat exchange tube, a continuous liquid film is formed, enhancing the heat transfer effect.

[0023] The air compressor is started, and the size of the intake valve / start / stop valve is controlled according to the gas load requirements. The gas is heated by the heater, and the carrier gas enters the falling film head (23) through the carrier gas pipe (21) and is injected into the heat exchange tube (25). The gas flows into the heat exchange tube to complete the gas circulation. The above liquid circulation and steam circulation are heated in the shell side at the same time. The steam generator is turned on, and the steam quantity is controlled by the steam regulating valve.

[0024] According to one embodiment of the present invention, the method further includes: a photoelectric sensor or image recognition module is installed in the sight glass at the lower part of the heat exchanger, at the liquid phase outlet pipe section of the gas-liquid separator, or at the inlet and outlet of the storage tank. This is used to acquire images of the liquid film or gas-liquid interface inside the heat exchanger, and to fuse the image signals with the output signals of the first metering device 16, the second metering device 10, and the temperature sensor to form a feedback control signal to control the liquid flow rate or gas flow rate.

[0025] According to one embodiment of the present invention, the method further includes: a second meter located between the liquid storage tank and the plate heat exchanger, for monitoring and controlling the flow rate of condensate from the liquid storage tank to the plate heat exchanger.

[0026] According to one embodiment of the present invention, the method further includes: controlling the open, closed, and ready states of valves F1 to F10 based on the numerical changes of the first flow meter, second flow meter, third flow meter, fourth flow meter, first metering device, second metering device, sight glass, differential pressure transmitter, and temperature sensor, thereby completing the testing and control of the gas pipeline unit, steam pipeline unit, test heat exchange unit, liquid circulation unit, and condensate treatment unit.

[0027] Compared to existing technologies, the technical effects achieved by this invention are as follows: First, by connecting a heat exchanger and a plate heat exchanger in series, a multi-stage cooling capacity utilization structure of "high-temperature pre-cooling—low-temperature deep cooling—recirculation" is formed. The plate heat exchanger utilizes the uncondensed gas from the upper part of the gas-liquid separator to exchange heat with the cold liquid in the liquid storage tank 4 or the cooling circuit, realizing the recovery and reuse of cooling capacity. Compared with traditional single-stage condensation systems, the cold source utilization rate is increased by 10% to 20%, significantly reducing the external refrigeration load. The return gas is pre-cooled before entering the heat exchanger 7, significantly reducing the cooling load on the heat exchanger; the refrigerant in the liquid storage tank and the plate heat exchanger together form a two-stage cold source network, realizing a "self-cooling cycle," effectively reducing the energy consumption of the compressor.

[0028] Secondly, it improves the stability of gas-liquid separation and circulation. The gas-liquid separator adopts a multi-stage structural design, which can achieve efficient separation of different condensable components. The separated condensate is collected and stored in a liquid storage tank, and the uncondensed gas is cooled by a plate heat exchanger and then returned to the heat exchanger. This cycle achieves continuous separation and continuous recovery, avoiding the problems of gas carrying liquid and low efficiency of secondary condensation. The plate heat exchanger buffers the temperature of the return gas, avoiding excessive temperature difference at the heat exchanger inlet. Temperature and pressure monitoring points are set at each heat exchange and separation stage to monitor the operating status in real time and prevent system fluctuations. This helps maintain the thermal and pressure balance of the system and prevents flash evaporation, liquid slugging, or overcooling.

[0029] Furthermore, the condensate collection tank is equipped with a condensate discharge valve, which can discharge liquid on a timed or automatic basis to prevent the condensation efficiency from decreasing due to rising liquid level. The discharge process also prevents liquid blockage and gas passage blockage, ensuring the continuity of system flow. The flow meter can detect the condensate discharge in real time to judge the condensation effect. Combined with the linkage control of pump 5 and valve F6, multi-parameter closed-loop control of liquid level, flow rate and temperature can be achieved, significantly improving the condensate management and online monitoring effect.

[0030] Meanwhile, it significantly improves the system's automation and intelligent operation. The system is equipped with multiple pressure, temperature, and flow signal monitoring points; the control logic adjusts valve openings in real time based on signal feedback from flow meters and temperature sensors, achieving dynamic load response and automatic energy-saving regulation. The closed-loop system reduces the risk of external pollution and gas leakage, ensuring safe operation. Attached Figure Description

[0031] Figure 1 This is a block diagram of a sensor-based carrier gas falling film heat exchanger test and control system disclosed in an embodiment of the present invention;

[0032] Figure 2 This is a schematic diagram of the sensor-based carrier gas falling film heat exchanger test and control system disclosed in an embodiment of the present invention;

[0033] Figure 3 This is a longitudinal cross-sectional view of the liquid distribution and film distribution structure of the upper part of the heat exchanger in the sensor-based carrier gas falling film heat exchanger test and control system disclosed in an embodiment of the present invention.

[0034] 1-Air compressor, 2-First flow meter, 3-Heater, 4-Liquid storage tank, 5-Centrifugal pump, 6-Fourth flow meter, 7-Heat exchanger 8-Gas-liquid separator, 9-Plate heat exchanger, 10-Second metering device, 11-Second flow meter, 12-Steam generator, 13-Steam pressure stabilizing tank, 14-Third flow meter, 15-Condensate collection tank, 16-First metering device, 17-Sight glass, 18-Liquid feed pipe, 19-Carrier gas inlet pipe, 20-Downcomer half-pipe, 21-Carrier gas pipe, 22-Distribution plate, 23-Falling film head, 24-Tube sheet, 25-Heat exchange tube, 26-Baffle plate, F1-Inlet valve / Start / Stop valve, F2-Liquid regulating valve, F3-Steam regulating valve, F4-Shell side inlet valve, F5-Shell side outlet regulating valve, F6-Pump inlet valve / Start / Stop valve, F7-Return gas regulating valve, F8-Drain valve, F9-Condensate discharge valve, F10-Safety valve / Vent valve, T-Temperature sensor, P-Differential pressure transmitter. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention. It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application.

[0036] The first aspect of this invention discloses a test and control system for a sensor-based carrier gas falling film heat exchanger, such as... Figure 1 The device includes a carrier gas pipeline unit, a steam pipeline unit, a test heat exchange unit, a liquid circulation unit, a condensate treatment unit, and a data measurement and control unit. Each unit is connected to form a whole through pipes or corresponding components.

[0037] like Figure 2 As shown, after the air compressor 1 is connected to the inlet valve / start / stop valve F1, the first flow meter 2, the heater, and other components through pipelines, the gas enters the falling film head through the carrier gas inlet pipe 19 and the carrier gas pipe 21. The carrier gas pipe is directly aligned with the falling film head. The carrier gas can be external gas or gas evaporated from liquid. Meanwhile, liquid from the centrifugal pump 5 enters the feed pipe through the fourth flow meter 6 and is then transported to the heat exchanger 7. The liquid is transported to the distribution plate 22 through the downcomer 20, and flows into the tube sheet through the small holes of the distribution plate. The liquid on the tube sheet is evenly distributed on the inner surface of the heat exchange tubes through the window on the falling film head for heat exchange. The falling film heat exchanger is tested by closing the carrier gas unit channel and opening the liquid delivery unit channel and the steam delivery channel. The heat transfer film coefficient is compared between the cases with and without carrier gas, thus comparing the heat transfer performance of the carrier gas falling film heat exchanger and the falling film heat exchanger.

[0038] This system can test the heat transfer coefficient of both carrier gas falling film heat exchangers and falling film heat exchangers. For the carrier gas falling film heat exchanger test, the air compressor connects to a regulating valve, a first flow meter 2, a heater, and other components via pipelines. Gas then enters the falling film head through the carrier gas inlet pipe 19 and carrier gas pipe 21, with the carrier gas pipe directly aligned with the falling film head. Alternatively, gas from a plate heat exchanger flows into heat exchanger 7 through a second flow meter 11. Additionally, liquid from centrifugal pump 5 enters the feed pipe through a fourth flow meter 6 and is then transported to heat exchanger 7. The liquid is then transported to the distribution plate 22 through the downcomer 20, and flows into the tube sheet 24 through small holes in the distribution plate. The liquid on the tube sheet is evenly distributed on the inner surface of the heat exchange tubes through windows on the falling film head 23 for heat exchange. The falling film heat exchanger test involves closing the carrier gas unit channel and opening the liquid delivery unit channel and the steam delivery channel.

[0039] Specifically, in the implementation of the carrier gas falling film heat exchange test, the carrier gas flow path operates as follows: the air compressor 1 starts and outputs compressed air. The air enters the first flow meter 2 through the F1 valve to measure the carrier gas flow rate. The air continues to be heated to the set temperature through the heater 3. The heated air enters the carrier gas inlet pipe 19 and the carrier gas pipe 21 through the pipeline. The outlet of the carrier gas pipe is aligned with the falling film head 23 and is injected into the heat exchange tube at a certain speed, carrying the liquid film to form a "gas-liquid two-phase" heat exchange.

[0040] Alternatively, in circulation mode, the gas can flow back into the heat exchanger 7 from the outlet of the plate heat exchanger 9 after being regulated by the second flow meter 11, thus achieving gas recirculation.

[0041] In the implementation of the carrier gas falling film heat exchanger test, during the operation of the liquid flow path, the liquid in the storage tank 4 is pressurized by the centrifugal pump 5, and after being measured by the fourth flow meter 6, it enters the feed pipe 18. Figure 3 As shown, the liquid rises along the downcomer 20 to the distribution plate 22. The liquid flows evenly to the tube sheet 24 through the micropores on the distribution plate. At the window of the falling film head 23, the liquid forms a uniform film along the inner wall of the heat exchange tube 25 and carries out heat and mass transfer together with the carrier gas. The mixed gas and liquid enter the gas-liquid separator 8 to separate the gas and condensate.

[0042] The shell side of the heat exchanger is supplied with heat from the steam side. The steam is controlled by the steam generator 12, steam pressure tank 13, regulating valve F3, and third flow meter 14. After heat exchange of the gas-liquid mixture on the tube side, the condensate flows into the condensate collection tank 15. Temperature sensor T and differential pressure transmitter (P) are arranged on the heat exchange tubes, inlet, and outlet. Data is collected by a multi-channel test recorder and sent to a computer to calculate the tube-side / shell-side heat transfer coefficient and the overall heat transfer film coefficient. The differential pressure transmitter P is used to measure the differential pressure and outputs a differential pressure signal ΔP; where ΔP_7 represents the differential pressure across heat exchanger 7, ΔP_9 represents the differential pressure across plate heat exchanger 9, and ΔP_15 is the differential pressure signal of the relevant tube section in condensate collection tank 15.

[0043] The steps for conducting a standard falling film heat exchanger test are as follows: Close the carrier gas passage, and close F1 (compressed air inlet valve) and F7 (return gas valve); open the liquid passage, keeping F5, F6, and F2 open; and simultaneously open the steam passage, opening F3 and F4.

[0044] Liquid is transported from storage tank 4 to heat exchanger 7 via pump 5, forming a single-phase liquid film; shell-side steam enters the outer wall of the heat exchanger and exchanges heat with the liquid film; after heat exchange, the liquid is condensed and the condensate is collected in condensate collection tank 15; the entire process has no carrier gas flow, and heat transfer depends entirely on the phase change and convection between steam and liquid film.

[0045] Specifically, the liquid storage tank 4 is located at the bottom center of the system, connected to the inlet of the centrifugal pump 5 (via valve F6) and the drain port of the gas-liquid separator 8. The liquid storage tank 4 mainly collects the liquid flowing down from the gas-liquid separator 8; the condensate or working fluid generated during the carrier gas or falling film heat exchange process eventually flows into this tank.

[0046] The liquid in storage tank 4 is delivered to the centrifugal pump inlet via valve F6; this ensures a stable liquid level in the pump and prevents dry running and cavitation. During system operation, liquid flow and temperature may fluctuate; the storage tank acts as a volume buffer, making system operation more stable. Simultaneously, it works in conjunction with drain valve F8 to discharge or replace the liquid. F8 is the drain valve at the bottom of the storage tank, used for emptying or draining liquid during cleaning.

[0047] F8 is used for draining liquid during venting or cleaning, or for preventing venting during system maintenance, liquid replacement, or cleaning. For example, it's used for emergency liquid draining when the system experiences abnormal temperature rise or the liquid level is too high. It also removes condensate after the experiment to keep the system clean. F10 is in a ready-to-use state for overpressure relief or venting during start-up and shutdown.

[0048] By measuring temperature, pressure, and flow signals, the heat exchange on the shell side and the heat absorption on the liquid film side are calculated; the heat transfer film coefficient is obtained from the energy balance relationship; the film coefficient is automatically calculated using the data acquisition system, and the differences between the two modes are compared.

[0049] The system achieves "gas-liquid separation, operating condition switching, and parameter measurement" through valves and flow measurement and control, thereby enabling the switching between two heat exchange modes, "carrier gas falling film" and "pure falling film", on the same heat exchanger, and measuring their heat transfer film coefficients respectively, so as to achieve direct comparison and verification of experimental data.

[0050] F1 controls whether compressed air enters the system. It is the main switch valve of the carrier air passage and is used to open or close the entire carrier air circuit.

[0051] F2 is located between the outlet of centrifugal pump 5 and the fourth flow meter 6. It controls the pump outlet flow rate and pressure. Centrifugal pump 5 provides fluid power, but its outlet pressure varies with resistance. F2 controls the liquid flow rate through opening adjustment, which, in conjunction with the fourth flow meter 6, affects the liquid velocity and liquid film thickness entering heat exchanger 7. Hydraulic shocks are easily generated during the start-up or shutdown of the centrifugal pump; F2 allows for slow opening, preventing instantaneous high-pressure liquid flow from impacting the heat exchange tubes.

[0052] Following F2, the fourth flow meter 6 is located on the liquid inlet pipeline of heat exchanger 7. The fourth flow meter 6 contains a rotatable impeller, which rotates as liquid flows through it. The rotation frequency is proportional to the flow velocity, and after signal conversion, it outputs the instantaneous and cumulative flow rates. The flow signals are sent to a multi-channel test recorder for real-time monitoring. F2 adjusts the flow rate, and the fourth flow meter 6 provides feedback data. The control system calculates the film thickness and heat transfer parameters, ensuring stable experimental flow rates, high repeatability, and high data accuracy.

[0053] Liquid flow rate is a key parameter for calculating the convective heat transfer coefficient, Reynolds number (Re), and Nusselt number (Nu) within the pipe; the measurement results provided by the fourth flow meter 6 are directly used to calculate the heat transfer film coefficient. Abnormal flow rates (sudden drops or fluctuations) can indicate air resistance, insufficient liquid level, or pump malfunction; it is an important signal source for experimental safety monitoring. Flow meter 6 is a critical measuring instrument in the liquid circulation system, providing accurate real-time flow data for experimental control and heat transfer parameter calculation.

[0054] F2 determines the liquid flow rate; the fourth flow meter 6 is a measuring instrument that records the liquid flow rate; the two work together to achieve precise control of the liquid supply. F6 is located between the liquid storage tank 4 and the centrifugal pump 5, controlling the flow rate of liquid entering the pump and its start / stop, preventing the pump from running dry when there is no liquid, and is used for filling the system before startup and isolating it when shutting down. It is closed during maintenance to prevent liquid backflow. It must be turned on before starting the liquid circulation system.

[0055] F3 controls the steam flow rate and pressure entering the shell side of the heat exchanger and is the core control valve for the steam heat source. F4 is located between the third flow meter 14 and the shell inlet of heat exchanger 7, controlling the on / off of steam entering the shell side of the heat exchanger. It is the shell inlet valve used for isolation or auxiliary pressure regulation.

[0056] F5 is located between the shell-side outlet of heat exchanger 7 and condensate collection tank 15, controlling condensate discharge and shell-side pressure. This indirectly controls the steam residence time and pressure within the shell side, maintaining stable steam saturation within the heat exchanger. When steam condenses on the shell side, forming condensate, F5's opening adjusts the outflow rate. In steam heat exchange experiments, shell-side pressure corresponds to saturation temperature. If F5 opening is too large, condensate is discharged rapidly, leading to a drop in shell-side pressure and steam subcooling. If F5 opening is too small, shell-side pressure increases, steam stagnates, and the heat exchange driving force weakens. Therefore, by fine-tuning F5, stable shell-side saturation pressure can be achieved.

[0057] The condensate collection tank 15 separates the condensate and uncondensed gas coming out from the shell side of the heat exchanger; the upper gas may flow back (e.g., return to a point in the system), while the lower liquid is discharged.

[0058] F9, located at the bottom of condensate collection tank 15, drains the condensate from the tank, maintaining a stable liquid level and preventing backflow into the gas passage. F9 controls the outflow of condensate from the bottom of condensate collection tank 15; it can be used for periodic drainage of accumulated liquid or quantitative sampling. Connected to the first metering device 16, it can also send the liquid to a recovery or analysis unit. The first metering device 16 collects and measures the condensate output for material balance and analysis.

[0059] The reaction gas is cooled on the shell side of heat exchanger 7; a portion of the gas condenses into liquid; it flows through the shell-side outlet regulating valve F5 into the condensate collection tank 15, and is discharged to the first metering device 16 through F9.

[0060] The condensate collection tank 15 serves as a collection area for liquid after gas condensation. Equipped with a condensate drain valve F9, it achieves the following technical effects: Periodic opening of F9 allows for the drainage of accumulated liquid, preventing excessively high liquid levels that could reduce gas-liquid separation efficiency; simultaneously, it allows for condensate composition sampling and analysis, monitoring the cleanliness and corrosion status of the heat exchange system. It also prevents liquid blockage by promptly draining condensate from the collection tank, avoiding liquid-phase blockage that could obstruct gas flow. Furthermore, it keeps the heat exchange surfaces clean; the draining operation removes impurities deposited in the condensate, keeping the inner walls of the heat exchange tubes clean and improving heat transfer efficiency.

[0061] Installing a first meter 16 on the condensate discharge line allows for real-time monitoring of condensate discharge, achieving the following technical effects: Assessing system condensation efficiency; flow data can be used to calculate the ratio of condensate to intake air, thus reflecting the condensation performance of the gas-liquid separator 8, heat exchanger 7, and plate heat exchanger 9. Determining equipment operating status; a sudden increase or decrease in discharge flow may indicate abnormal system cooling or blockage in the condensate collection tank. Providing maintenance data; long-term data accumulation allows analysis of condensate generation trends, providing data support for discharge cycle optimization and equipment maintenance.

[0062] Meanwhile, the combination of condensate discharge valve F9 at point 15 of the condensate collection tank and the first metering device 16 enables the condensate treatment unit to not only have a discharge function but also online monitoring and maintenance diagnostic functions. This design can significantly improve the safety of system operation, prevent abnormal liquid levels, stably maintain a constant condensation effect, and guide maintenance cycles through data analysis, thus ensuring maintainability.

[0063] The reflux gas circulation system formed by the plate heat exchanger 9, together with the discharge valve F9 and the first metering device 16 at the condensate collection tank 15, realizes a highly efficient and energy-saving system integrating gas-liquid separation, energy recovery, automatic management of condensate and operation monitoring, which significantly improves the energy efficiency, stability and intelligence level of the overall heat exchange device.

[0064] Centrifugal pump 5 is located between liquid storage tank 4 and heat exchanger 7. It pressurizes the liquid in the storage tank and delivers it to heat exchanger 7, ensuring the liquid can smoothly form a falling film or enter the heat exchange tubes. The pump outlet flow rate determines the liquid film thickness, which is an important variable in calculating the heat transfer coefficient. It works in conjunction with valves F6 and F2, and the fourth flow meter 6 to regulate the liquid flow rate. F7 is located on the return pipeline from the outlet of plate heat exchanger 9 to heat exchanger 7, controlling the gas flow rate returning from the plate heat exchanger to the heat exchanger, thus enabling switching between two test modes: carrier gas falling film and ordinary falling film.

[0065] F8 is located at the bottom drain port of liquid storage tank 4, used to drain the liquid in the liquid storage tank, which is convenient for liquid replacement or system cleaning.

[0066] The F10 safety valve / vent valve is located on the top or side of the steam pressure tank 13. It automatically releases pressure when the steam pressure in the steam pressure tank is too high to prevent overpressure damage to the equipment; it can also be used for the venting system during startup or shutdown.

[0067] The F9 condensate drain valve and the F10 safety valve / vent valve ensure safe operation of the equipment and prevent overpressure and condensate retention.

[0068] F2, F3, and F5 control the liquid or vapor flow rate, which is crucial for determining the heat transfer intensity and the accuracy of the film coefficient test. F1, F6, F7, and F8 control whether the gas, liquid, and return paths are open, enabling the switching of system operating modes (carrier gas or no carrier gas). F5 adjusts the shell-side outlet back pressure to maintain a stable heat exchange state.

[0069] The gas-liquid separator 8 is used to separate the gas and liquid phase materials from the heat exchange tube 25, and complete the heat exchange of the hot and cold media and the gas-liquid separation process of the cold media; the plate heat exchanger 9 is used for gas phase condensation, and the condensate produced therefrom flows into the liquid storage tank 4 together with the condensate of the gas-liquid separator 8.

[0070] like Figure 2 As shown, the gas-liquid separator 8 separates the condensed gas-liquid mixture from the heat exchanger 7, and the separated condensate enters the storage tank 4 through a pipeline. The uncondensed gas then enters the plate heat exchanger 9 through a pipeline. In the plate heat exchanger 9, the uncondensed gas exchanges heat with the fluid from the storage tank 4 or an external cooling medium, further reducing its temperature. The cooled gas then enters the inlet (upper or middle) of the heat exchanger 7 through valve F7 and the second flow meter 11, achieving self-circulating reflux heat exchange.

[0071] The plate heat exchanger 9 and the flow meter play a crucial role in gas reflux, primarily achieving energy recovery and energy saving. The plate heat exchanger 9 utilizes the temperature difference of the uncondensed gas itself to exchange heat with the refrigerant or reflux liquid in the storage tank 4. This heat exchange reduces the cooling load on the heat exchanger 7, improving the overall system's energy efficiency ratio. This achieves a closed-loop energy recovery process that pre-cools the reflux gas, reduces the burden on the heat exchanger, and improves the utilization rate of cooling capacity.

[0072] Secondly, to reduce system temperature fluctuations, directly introducing the separated gas into heat exchanger 7 would result in excessively high temperatures and unstable heat exchange; plate heat exchanger 9 can keep the gas temperature within a narrow range, smoothing system heat load fluctuations.

[0073] Furthermore, it improves gas-liquid separation efficiency. When the return gas, cooled by the plate heat exchanger 9, enters the heat exchanger 7, its temperature is even lower, promoting the continued condensation reaction in the heat exchanger; thus, the gas-liquid separator 8 has a lighter separation load in the next cycle, resulting in higher separation efficiency.

[0074] The technical effects achieved by the second flow meter 11 connected to the plate heat exchanger 9 are as follows: First, it accurately monitors the circulating flow rate. The second flow meter 11 is placed in the second carrier gas pipeline unit, located on the return pipeline from the outlet of the plate heat exchanger 9 to the heat exchanger 7, and can measure the volumetric flow rate of the return gas in real time. This data can be used to determine the system's heat exchange efficiency and whether the gas-liquid separation load is balanced.

[0075] Secondly, it achieves automatic control and energy-saving operation. The flow meter signal is input to the control system, which can control the load of valve F7 or centrifugal pump 5. When the flow rate is too high or too low, the system automatically adjusts the valve opening to maintain the dynamic balance of gas-liquid separation, heat exchange, and reflux.

[0076] Furthermore, it can reflect the health status of the equipment. Abnormal flow (increase or decrease) often indicates scaling in plate heat exchangers, gas leaks, or separator blockages; therefore, flow monitoring also has online diagnostic functions, improving operational reliability.

[0077] Compared to traditional single-stage condensation and discharge processes, this solution adds a plate heat exchanger 9, a return pipeline, a flow meter, additional valves such as F7, and a control system. In summary, the gas self-circulation heat exchange system formed by the plate heat exchanger 9 achieves staged heat transfer. The return gas is pre-cooled by the plate heat exchanger 9 and then undergoes deep heat exchange in the heat exchanger 7. It utilizes its own waste heat to cool the system, eliminating the need for an external cold source and reducing irreversible energy loss. It avoids refrigerant or gas emissions, achieving energy conservation and environmental protection, and forming a closed-loop cycle. Precise feedback from the flow meter ensures continuous stability of the gas-liquid ratio, cooling load, and energy flow, improving system stability.

[0078] This circulating system, through a closed loop consisting of a gas-liquid separator 8, a plate heat exchanger 9, and a flow meter, pre-cools the uncondensed gas before it enters the heat exchanger 7, achieving full energy recovery and recycling. This significantly reduces cold source energy consumption; improves gas-liquid separation efficiency; enhances system thermal balance and operational stability; and enables automatic monitoring and energy-saving control.

[0079] The sight glass 17 monitors and records the flow state of liquid or gas inside the heat exchanger 7 in real time through built-in photoelectric sensors or image recognition technology. It combines the image data with other sensor signals (such as flow meters and temperature sensors) to provide additional feedback signals to the control system, thereby assisting in optimizing flow control and improving heat transfer efficiency.

[0080] The sight glass 17 is installed at the bottom of the heat exchanger 7 or at the liquid phase outlet pipe section of the gas-liquid separator 8 or at the inlet and outlet of the condensate collection tank 15 or the storage tank 4; it facilitates direct observation of the fluid state (gas-liquid interface, flow state, color, foam, etc.).

[0081] It adopts a high-pressure, high-temperature resistant tempered glass observation window with anti-fog and explosion-proof design. It can be used with LED lighting and protective cover, and is suitable for low-temperature and high-pressure working conditions.

[0082] The technical benefits of adding the sight glass 17 are as follows: First, it enhances the system's visualization and operational monitoring capabilities. Operators can observe the gas-liquid separation status in real time, including assessing liquid level, flow conditions, and the presence of entrained air bubbles or liquid hammer risks. The sight glass allows direct observation of condensate color changes and impurity deposition, enabling assessment of condensation effectiveness and contamination levels. It also helps verify the accuracy of flow meters and level sensors, preventing misjudgments caused by instrument errors. Finally, it achieves dual detection of visual data and signals, significantly improving the reliability and practicality of system operational status assessment.

[0083] Secondly, it improves the efficiency of equipment maintenance and fault diagnosis. If the gas-liquid separator 8 or condensate collection tank 15 becomes clogged, has an abnormal liquid level, or experiences poor drainage, the problem area can be quickly located through the sight glass. When incomplete condensation or uneven flow occurs in the plate heat exchanger 9, the presence of liquid in the return gas can be observed. Maintenance personnel can confirm the operating conditions through the sight glass without shutting down the system, and without disassembling the pipelines. This significantly shortens the maintenance cycle, reduces downtime, and improves maintenance safety and economy.

[0084] Furthermore, it enhances safety monitoring and early warning capabilities. During transient processes such as system startup, shutdown, and switching of operating conditions, the sight glass allows operators to visually observe fluid flow direction and phase changes. When temperature or pressure is abnormal, it can observe whether liquid backflow, gas boiling, or frost formation occurs. By combining temperature and pressure sensors with flow meter signals, a visualized safety control system can be formed. This effectively prevents accidents such as liquid slugging, overpressure, and condensate backflow, thus improving the system's safety level.

[0085] Finally, it assists in process optimization and adjustment. Operators can adjust valve openings (such as F5, F6, and F9) based on liquid level fluctuations observed in the sight glass; they can visually observe the flow patterns in throttling, heat exchange, and discharge processes, providing on-site data for process parameter optimization; and in tests with new operating conditions or new media, the sight glass can visually assess the matching of heat exchange, separation, and condensation. This enhances the system's adjustability and experimental verification capabilities, making process operation more flexible and reliable.

[0086] The sight glass 17 works in conjunction with the first metering device 16 to visually verify flow changes and liquid flow, providing dual monitoring to prevent missed detections of abnormal flow. The sight glass 17 also works with the plate heat exchanger 9 to observe the condensation of the return gas, ensuring heat exchange efficiency and separation effect. Furthermore, the sight glass 17 works in conjunction with the condensate collection tank 15 and the condensate discharge valve F9 to visualize the drainage process, preventing liquid blockage and gas entrainment. Finally, the sight glass 17 works in conjunction with the temperature and pressure monitoring point components to form a visualized safety control system, achieving "visible safety" operation.

[0087] In summary, the sight glass 17 upgrades the system from a signal monitoring type to a visual diagnostic type, greatly improving the practicality, reliability and intelligence of the invention.

[0088] The system is equipped with multiple flow meters: a first flow meter 2, a second flow meter 11, a third flow meter 14, and a fourth flow meter 6, which are used to monitor the flow rates of the carrier gas pipeline unit, the second carrier gas pipeline unit, the steam pipeline unit, and the liquid circulation unit, respectively; and a first meter (16) is used to monitor the condensate discharge flow rate. The system automatically adjusts the working status of each unit based on these flow data to achieve multi-level feedback control, ensuring that the system can operate efficiently and stably under different operating conditions.

[0089] The gas-liquid separator 8 optimizes the separation efficiency of gas and liquid through multi-stage separation technology. The condensate and gas enter the storage tank 4 and the reflux system, respectively. The reflux gas then enters the heat exchanger 7 through the plate heat exchanger 9, achieving efficient energy recovery. The condensate treatment unit cleans the condensate periodically and discharges or samples it periodically through the condensate discharge valve F9, ensuring the stability and cleanliness of the heat exchange system.

[0090] First, the liquid circulates. Open the inlet valve / start / stop valve F6 to start the centrifugal pump 5. The liquid flows through the liquid regulating valve F2. The size of F2 is controlled according to the load requirements. The flow rate is observed through the fourth flow meter 6. The liquid enters the distribution plate 22. The liquid in the distribution plate flows into the tube sheet through the small holes of the distribution plate. The liquid on the tube sheet flows into the inner wall of the heat exchange tube through the film distributor and flows directly to the gas-liquid separator 8. The liquid flows to the liquid storage tank 4, and the gas flows to the plate heat exchanger 9 for further recirculation.

[0091] Next, start the air compressor 1, control the size of the intake valve / start / stop valve F1 according to the gas load requirements, observe the flow rate through the first flow meter 2, and the gas is further heated by the heater 3. Then, the gas flows into the heat exchange tube through the carrier gas pipe 21 in the distribution plate and is aligned with the heat exchange tube.

[0092] The above cycle also requires shell side heating. The steam generator 12 is turned on, and the steam volume is controlled by the steam regulating valve F3. The steam volume is observed by the third flow meter 14.

[0093] Specifically, the valve positions are: F6 closed, F2 closed, F1 closed, F3 closed, F4 / F5 / F7 slightly open, F9 closed, and F10 ready.

[0094] First flow meter 2, second flow meter 11, third flow meter 14, and fourth flow meter 6 are zeroed / calibrated; metering instruments (10 / 16) are zeroed; T and ΔP self-tests pass; sight glass 17 illumination is available, and the viewing window is clean. ΔP_7, ΔP_9, T_max, T_min, and liquid level (high / low) are all written to the controller. ΔP_7 represents the pressure difference across heat exchanger 7 (gas / liquid channel). The controller reads this pressure difference signal in real time and compares it with the set upper limit. If the limit is exceeded, it indicates blockage, liquid hammer, or frosting, and automatically reduces flow, alarms, or shuts down. In this embodiment, an alarm or automatic valve closure F1 / F2 is triggered. ΔP_9 represents the pressure difference of plate heat exchanger 9, used to determine whether the heat exchange surface of 9 is scaled or blocked; when the set limit is exceeded, the control system performs bypass or load reduction.

[0095] T_max / T_min represent the upper and lower limits of the temperature, generally referring to the outlet temperature of the heat exchanger or the temperature of the liquid storage tank. This information is written into the controller, and the PLC will automatically maintain the temperature within the range; if the temperature exceeds the range, an alarm will sound or the steam valve / cooling valve will be activated to automatically shut off the cooling circuit to prevent overcooling or icing.

[0096] High-high / Low-low indicates the liquid level limit alarm point of the liquid storage tank 4, gas-liquid separator 8, etc. When the liquid level is too high or too low, an alarm or interlock action is triggered. In this embodiment, when the liquid level exceeds the limit alarm point, the pump 5 inlet and valve F6 are automatically shut off.

[0097] In the liquid circulation unit, a liquid film is first established to form a stable liquid film on the inner wall of the heat exchange tube, preventing subsequent gas phase entry from causing dry wall and liquid hammer. Open the inlet / start / stop valve F6 to start the centrifugal pump 5, and gradually open the liquid regulating valve F2. Use the fourth flow meter 6 as the controlled variable for PID regulation. Observe the inlet and outlet temperatures and ΔP_9 of the liquid storage tank 4 and the plate heat exchanger 9 to confirm that the plate heat exchanger 9 is unobstructed.

[0098] The liquid enters the inner wall of the heat exchange tube through F2, riser, distribution plate 22 / tube sheet 24, and film distributor. The sight glass 17 (located at the lower part of the heat exchanger 7) should show a continuous and uniform liquid curtain without any breaks or sprays. If this occurs, increase the set flow rate of the liquid circulation loop to allow pump 5 to output more liquid to the heat exchanger.

[0099] Downstream gas-liquid separator 8 separates the carried bubbles / vapor from the liquid phase. The liquid goes to the storage tank 4, and the tank level is accumulated by the second meter 10 (recovery / replenishment amount). The gas is cooled and recirculated through plate heat exchanger 9.

[0100] If the pressure difference between the shell side and tube side of ΔP_7 is stable within the allowable value, but gradually increases while the flow meter 6 remains unchanged, it is determined that there may be scaling or partial liquid blockage (liquid blockage) on the inner wall of the heat exchanger, triggering flow reduction and preparing for online flushing.

[0101] Regarding the gas pipeline unit, the gas phase is fed into the carrier gas pipe aligned with the heat exchange tube according to the set load, and enters the pipe to flow in parallel / counter-current with the liquid film for heat transfer. Air compressor 1 is started, valve F1 is gradually opened, and PID regulation is performed with the first flow meter 2 as the controlled variable.

[0102] After being heated by heater 3, the gas's inlet temperature (T_g, in) and gas channel pressure difference (ΔP_g) are monitored in real time before entering heat exchanger 7. These two parameters are used to determine whether heating is sufficient and gas flow is smooth, and the heating power or gas flow rate is automatically adjusted accordingly to ensure stable temperature, normal flow, and no blockage or liquid slugging when the gas enters the heat exchanger. The gas enters the distribution plate, and the carrier gas pipe 21 is aligned with the heat exchange tube before proceeding to the heat exchange tube. Sight glass 17 confirms that no continuous liquid column is blown up from the bottom (to prevent entrainment / liquid slugging). The flow rate of the first flow meter 2 is lowered, or the flow rate of the fourth flow meter 6 is increased, while simultaneously slightly closing F7 to reduce the reflux ratio.

[0103] Temperature sensor T is used to measure temperature and outputs a temperature signal; T_g,in is the carrier gas inlet temperature, and T_max / T_min are the control thresholds.

[0104] The temperature difference between the hot-side outlet temperature and the gas inlet temperature of the heat exchanger, i.e., the target end temperature difference value ΔT_end, is used to characterize the heat exchanger's heat exchange effect and thermal balance state. By adjusting the steam flow rate or gas flow rate, ΔT_end is kept within the set range to achieve a stable and efficient heat exchange process. If ΔT_end is too low, steam should be added first, followed by reducing the gas flow rate; if ΔT_end is too high, steam should be reduced and the gas flow rate increased. A sharp increase in ΔP_7 / ΔP_9 indicates frost / liquid blockage. Immediately reduce the gas flow rate by 20%, open the F5 bypass to release pressure, and if necessary, switch to the defrost / flushing procedure. If the sight glass 17 shows a continuous liquid curtain / foam, there may be entrainment / abnormal liquid level. Reduce the reflux ratio, briefly open F9 to drain the liquid, and check the liquid level.

[0105] In the condensate treatment unit, F9 is opened periodically, and the first meter 16 accumulates the discharge volume for that period. When sight glass 17 shows foam covering / liquid level rising, or ΔP_15 rises to the threshold, liquid is immediately discharged. During discharge, ΔP_7 and sight glass 17 are monitored simultaneously. If a liquid curtain appears to rise, F9 is closed and F5 is opened for pressure stabilization. ΔP_15 represents the pressure differential in the condensate collection tank.

[0106] The heat exchange unit was tested, and the reflux ratio was calculated using the fourth flow meter 6 and the first flow meter 2. The opening of the automatic reflux gas regulating valve F7 is adjusted so that... Maintaining the system within the set range (0.15–0.40) stabilizes the system's cooling recovery and heat exchange performance. A continuous liquid curtain appears on sight glass 17 for >5 seconds. Automatically reduce by 20%. The steam flow rate is adjusted based on the third flow meter 14 on the steam side. If ΔT_end is low (indicating insufficient heat exchange), the steam flow rate is increased first; if ΔT_end is high (indicating excessive heat exchange), the steam flow rate is decreased. Changes in steam volume directly affect the shell-side temperature and are the primary control mechanism.

[0107] Secondary adjustment: The gas flow rate is measured using the first flow meter 2. If ΔT_end is too high (overheating, increase gas flow rate); the reflux gas regulating valve F7 controls the reflux ratio of the plate heat exchanger 9. Valve F5 / F6 controls the flow rate and pressure distribution of liquid before the distribution plate.

[0108] In the study of the effect of introducing carrier gas on the heat transfer film coefficient, the heating steam pressure is controlled to a constant value. For a specific carrier gas flow rate, the liquid flow rate is changed and the data is recorded. The evaporation heat transfer film coefficient can be plotted against different liquid Reynolds numbers. The relationship between the heat transfer film coefficient and the liquid Reynolds number is shown in the cases of no introduction and introduction of carrier gas. If the liquid Reynolds number increases, the heat transfer film coefficient will increase.

[0109] For a specific liquid flow rate, when the carrier gas flow rate is changed, if the carrier gas Reynolds number increases, more vaporization nuclei can be provided, thereby enhancing liquid evaporation and increasing the heat transfer coefficient. It can also be observed whether the heat transfer coefficient continues to increase when the carrier gas flow rate increases to a certain extent.

[0110] Meanwhile, the effect of introducing carrier gas on wall superheat was investigated by varying the system heating steam pressure under different carrier gas flow rates. The introduction of carrier gas triggered mass transfer in the system, enhancing heat transfer, primarily manifested in a reduction in wall temperature and wall superheat. With a constant liquid flow rate, varying the system heating steam pressure under different carrier gas flow rates yielded results for the same wall heat load. The wall superheat was significantly reduced after introducing carrier gas compared to when no carrier gas was introduced. The reduction was approximately 2–6°C for different carrier gas flow rates, with the reduction increasing with increasing carrier gas flow rate.

[0111] The technical effects achieved by this invention are as follows: First, by connecting a heat exchanger and a plate heat exchanger in series, a multi-stage cooling capacity utilization structure of "high-temperature pre-cooling—low-temperature deep cooling—recirculation" is formed. The plate heat exchanger utilizes the uncondensed gas from the upper part of the gas-liquid separator to exchange heat with the cold liquid in the liquid storage tank 4 or the cooling circuit, realizing the recovery and reuse of cooling capacity. Compared with the traditional single-stage condensation system, the cold source utilization rate is increased by 10% to 20%, significantly reducing the external refrigeration load. The return gas is pre-cooled before entering the heat exchanger 7, significantly reducing the cooling load of the heat exchanger; the refrigerant in the liquid storage tank and the plate heat exchanger together form a two-stage cold source network, realizing a "self-cooling cycle," effectively reducing the energy consumption of the compressor.

[0112] Secondly, it improves the stability of gas-liquid separation and circulation. The gas-liquid separator adopts a multi-stage structural design, which can achieve efficient separation of different condensable components. The separated condensate is collected and stored in a liquid storage tank, and the uncondensed gas is cooled by a plate heat exchanger and then returned to the heat exchanger. This cycle achieves continuous separation and continuous recovery, avoiding the problems of gas carrying liquid and low efficiency of secondary condensation. The plate heat exchanger buffers the temperature of the return gas, avoiding excessive temperature difference at the heat exchanger inlet. Temperature and pressure monitoring points are set at each heat exchange and separation stage to monitor the operating status in real time and prevent system fluctuations. This helps maintain the thermal and pressure balance of the system and prevents flash evaporation, liquid slugging, or overcooling.

[0113] Furthermore, the condensate collection tank is equipped with a condensate discharge valve, which can discharge liquid on a timed or automatic basis to prevent the condensation efficiency from decreasing due to rising liquid level. The discharge process also prevents liquid blockage and gas passage blockage, ensuring the continuity of system flow. The flow meter can detect the condensate discharge in real time to judge the condensation effect. Combined with the linkage control of pump 5 and valve F6, multi-parameter closed-loop control of liquid level, flow rate and temperature can be achieved, significantly improving the condensate management and online monitoring effect.

[0114] Meanwhile, it significantly improves the system's automation and intelligent operation. The system is equipped with multiple pressure, temperature, and flow signal monitoring points; the control logic adjusts valve openings in real time based on signal feedback from flow meters and temperature sensors, achieving dynamic load response and automatic energy-saving regulation. The closed-loop system reduces the risk of external pollution and gas leakage, ensuring safe operation.

[0115] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A test and control system for a sensor-based carrier gas falling film heat exchanger, characterized in that, The system includes a carrier gas pipeline unit, a steam pipeline unit, a test heat exchange unit, a liquid circulation unit, a condensate treatment unit, and a data measurement and control unit. Each unit is connected to form a whole through pipelines or corresponding components. The carrier gas pipeline unit includes a first carrier gas pipeline unit, a second carrier gas pipeline unit, and a carrier gas pipeline start / stop control unit. The first carrier gas pipeline unit includes an air compressor (1) and a heater (3). The outlet of the air compressor (1) is connected to one end of the heater (3), and the other end of the heater (3) is connected to one end of the heat exchanger (7). The second carrier gas pipeline unit includes a gas-liquid separator (8) and a plate heat exchanger (9). One end of the gas-liquid separator (8) is connected to the heat exchanger (7), and the other end of the gas-liquid separator (8) is connected to one end of the plate heat exchanger (9). The other end of the device (9) is connected to the heat exchanger (7); the carrier gas pipeline start / stop control unit includes an inlet valve / start / stop valve (F1) and a return gas regulating valve (F7) to switch the carrier gas mode of the first carrier gas pipeline unit and the second carrier gas pipeline unit; the inlet valve / start / stop valve (F1) is located between the air compressor (1) and the heater (3) to open or close the first carrier gas pipeline unit; the return gas regulating valve (F7) is located between the plate heat exchanger (9) and the heat exchanger (7) to control the gas flow rate of the plate heat exchanger (9) returning to the heat exchanger (7); The steam pipeline unit includes a steam generator (12), a steam pressure tank (13), and a steam pipeline start-stop control unit. The outlet of the steam generator (12) is connected to the inlet / steam outlet of the steam pressure tank (13), and the outlet / steam outlet of the steam pressure tank (13) is connected to the shell-side inlet of the heat exchanger (7). The steam pipeline start-stop control unit includes a steam regulating valve (F3), a shell-side inlet valve (F4), and a safety valve / vent valve (F10). The regulating valve (F3) is located between the steam pressure tank (13) and the shell-side inlet valve (F4) to control the steam flow rate and pressure entering the shell-side inlet of the heat exchanger (7); the shell-side inlet valve (F4) is located between the steam regulating valve (F3) and the shell-side inlet of the heat exchanger (7) to control the on / off state of steam entering the shell side of the heat exchanger (7); the safety valve / vent valve (F10) is located at the top of the steam pressure tank (13) or at the high point of the steam pipeline to release overpressure or start / stop venting. The heat exchanger (7) in the test heat exchange unit includes a liquid feed pipe (18), a carrier gas inlet pipe (19), a downcomer half pipe (20), a carrier gas pipe (21), a distribution plate (22), a falling film head (23), a tube sheet (24), a heat exchange tube (25), and a baffle plate (26), which are used for heat exchange between gas and liquid media. The liquid circulation unit includes a storage tank (4), a centrifugal pump (5), and a liquid circulation control unit. One end of the storage tank (4) is connected to one end of the gas-liquid separator (8) and / or the plate heat exchanger (9), and the other end of the storage tank (4) is connected to the centrifugal pump (5). The liquid circulation control unit includes an inlet valve / start / stop valve (F6) and a liquid regulating valve (F2). The inlet valve / start / stop valve (F6) is located between the storage tank (4) and the centrifugal pump (5) and is used to control the flow rate of liquid entering the centrifugal pump (5) and / or start / stop. The liquid regulating valve (F2) is located between the centrifugal pump (5) and the heat exchanger (7) and is used to regulate the liquid flow rate. The condensate treatment unit includes a condensate collection tank (15) and a condensate treatment control unit. The condensate collection tank (15) is connected to the shell-side outlet of the heat exchanger (7). The condensate treatment control unit includes a shell-side outlet regulating valve (F5) and a condensate discharge valve (F9). The shell-side outlet regulating valve (F5) is located between the condensate collection tank (15) and the heat exchanger (7) and is used to control the condensate discharge and shell-side pressure. The drain valve (F8) is located at the bottom of the storage tank (4) and is used for system evacuation or cleaning. The condensate discharge valve (F9) is located between the condensate collection tank (15) and the first metering device (16) and is used to control the periodic discharge of accumulated liquid or quantitative sampling. The data measurement and control unit includes a first flow meter (2), a second flow meter (11), a third flow meter (14), a fourth flow meter (6), a first metering device (16), a differential pressure transmitter (P), and a temperature sensor (T); the first flow meter (2) is placed in the first carrier gas pipeline unit, the second flow meter (11) is placed in the second carrier gas pipeline unit, the third flow meter (14) is placed in the steam pipeline unit, and the fourth flow meter (6) is placed in the liquid circulation unit; the first metering device (16) is connected to one end of the condensate discharge valve (F9) and is used to monitor and control the flow rate of the condensate.

2. The system according to claim 1, characterized in that, The gas-liquid separator (8) is used to separate the gas and liquid phase materials from the heat exchange tube (25) to complete the heat exchange of the hot and cold media and the gas-liquid separation of the cold media; the plate heat exchanger (9) is used for gas phase condensation, and the condensate produced therefrom flows into the storage tank (4) together with the condensate of the gas-liquid separator (8), while the cooled return gas is introduced into the heat exchanger (7).

3. The system according to claim 1, characterized in that, The data measurement and control unit also includes a sight glass (17), which is installed at the bottom of the heat exchanger (7) or at the liquid phase outlet pipe section of the gas-liquid separator (8) or at the inlet and outlet of the condensate collection tank (15) or the storage tank (4). The sight glass (17) is equipped with a photoelectric sensor or an image recognition module to collect images of the liquid film or gas-liquid interface inside the heat exchanger (7) and fuse the image signal with the output signals of the flow meter and temperature sensor to form a feedback control signal to control the liquid flow rate or gas flow rate.

4. The system according to claim 1, characterized in that, The data measurement and control unit also includes a second meter (10), which is located between the liquid storage tank (4) and the plate heat exchanger (9) and is used to monitor and control the flow rate of condensate from the liquid storage tank (4) to the plate heat exchanger (9).

5. The system according to any one of claims 1 to 4, characterized in that, The data measurement and control unit controls the opening, closing, and ready states of valves F1 to F10 based on the numerical changes of the first flow meter (2), the second flow meter (11), the third flow meter (14), the fourth flow meter (6), the first metering instrument (16), the second metering instrument (10), the sight glass (17), the differential pressure transmitter (P), and the temperature sensor (T), thereby completing the testing and control of the gas pipeline unit, the steam pipeline unit, the test heat exchange unit, the liquid circulation unit, and the condensate treatment unit.

6. The system according to claim 5, characterized in that, The differential pressure transmitter (P) is respectively installed at the shell-side inlet, shell-side outlet and tube-side gas or liquid outlet of the heat exchanger (7), and the temperature sensor (T) is located at the shell-side inlet, shell-side outlet, tube-side outlet and the wall of the heat exchange tube (25) of the heat exchanger (7).

7. A test and control method for a sensor-based carrier gas falling film heat exchanger, characterized in that, The method, applied to the system of claim 1, includes testing and controlling the carrier gas pipeline unit, steam pipeline unit, test heat exchange unit, liquid circulation unit, and condensate treatment unit based on data displayed by the data measurement and control unit, including: Open the inlet valve / start / stop valve (F6) and start the centrifugal pump (5). The liquid flows through the liquid regulating valve (F2). The opening of the liquid regulating valve (F2) is controlled according to the load requirements. The liquid enters the distribution plate (22) of the heat exchanger (7) and flows into the tube sheet (24) through the small holes of the distribution plate (22). The liquid on the tube sheet (24) flows into the inner wall of the heat exchange tube (25) through the film distributor and flows directly to the gas-liquid separator (8) and then to the liquid storage tank (4). At the same time, the gas separated from the gas-liquid separator (8) flows to the plate heat exchanger (9). The gas after heat exchange in the plate heat exchanger (9) flows back to the heat exchanger (7) to complete the liquid circulation. The film distributor is located directly above the tube sheet (24), below the distribution plate, and between the liquid inlet and the tube sheet (24). It is used to evenly distribute the liquid to the inner wall of each heat exchange tube to form a continuous liquid film. Start the air compressor (1), control the opening of the intake valve / start / stop valve (F1) according to the gas load requirements, heat the gas through the heater (3), the carrier gas enters the falling film head (23) through the carrier gas pipe (21) and is sprayed into the center of the heat exchange tube (25), and the gas flows into the heat exchange tube (25) to complete the gas circulation; While the liquid circulation and carrier gas circulation are running, the shell side steam is heated, the steam generator (12) is turned on, and the steam supply is controlled by the steam regulating valve (F3).

8. The method according to claim 7, characterized in that, The method further includes: a photoelectric sensor or image recognition module is installed in the sight glass (17), which is installed at the bottom of the heat exchanger (7) or at the liquid phase outlet pipe section of the gas-liquid separator (8) or at the inlet and outlet of the condensate collection tank (15) or the storage tank (4) to collect images of the liquid film or gas-liquid interface inside the heat exchanger (7), and the image signal is fused with the output signals of the flow meter and temperature sensor to form a feedback control signal to control the liquid flow rate or gas flow rate.

9. The method according to claim 7, characterized in that, The method further includes a second meter (10) located between the liquid storage tank (4) and the plate heat exchanger (9) for monitoring and controlling the flow rate of condensate from the liquid storage tank (4) to the plate heat exchanger (9).

10. The method according to claim 7, characterized in that, The method further includes: controlling the open, closed, and ready states of valves F1 to F10 based on the numerical changes of the first flow meter (2), the second flow meter (11), the third flow meter (14), the fourth flow meter (6), the first meter (16), the second meter (10), the sight glass (17), the differential pressure transmitter (P), and the temperature sensor (T), thereby completing the testing and control of the gas pipeline unit, the steam pipeline unit, the test heat exchange unit, the liquid circulation unit, and the condensate treatment unit.

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