Temperature control system and temperature control method for low flash point heat conducting medium

Abstract

The present invention provides a temperature control system and method for a low-flash-point heat-conducting medium. The temperature control system includes three subsystems: medium circulation, heating, and cooling. The medium circulation system stores the low-flash-point medium through a first expansion tank, which is driven by a main circulation pump to flow through a heat exchanger and an evaporator. The heating system stores the high-temperature heat-conducting medium through a second expansion tank. After being heated by an electric heating pipe, the medium enters the heat exchanger for indirect heat exchange with the low-flash-point medium through a main regulating valve and a bypass regulating valve. The refrigeration system is connected to the evaporator to provide cooling capacity. The temperature control method includes: first preheating the high-temperature medium to 80-85% of the target temperature, and starting the main circulation pump after stabilization; synchronously adjusting the valve and the electric heating pipe, and maintaining the main valve at an opening of 40-60%; and adopting a three-stage strategy in the precise temperature control stage: maintaining the status quo within ±1°C, adjusting only the valve within ±1-5°C, and coordinating the valve and the electric heating pipe when the temperature exceeds ±5°C. The present invention ensures safety and achieves precise temperature control through medium isolation and hierarchical control.

Description

Technical Field

[0001] The present invention relates to the technical field of temperature control of low-flash-point heat-conducting media, and in particular to a temperature control system and a temperature control method of low-flash-point heat-conducting media. Background Art

[0002] Low-flash-point heat transfer media refer to flammable and explosive liquids with low flash points, such as diesel or other organic solvents. They are prone to combustion or explosion under high temperature or local overheating conditions. Such media are often used to transfer heat in industrial temperature control systems, but due to their instability, direct heating poses significant safety risks.

[0003] In the existing technology, some temperature control systems use electric heating tubes to directly heat low-flash point media. Although this method has a simple structure, the surface temperature of the electric heating tube is relatively high, which can easily cause local overheating of the low-flash point media and even cause flash fire or explosion.

[0004] Furthermore, direct heating makes precise temperature control difficult, potentially exacerbating safety risks due to temperature fluctuations. While some technologies have attempted to mitigate this issue by strengthening monitoring or reducing heating power, they have not fundamentally eliminated direct contact between the heating element and the low-flash-point medium, and safety risks remain. Summary of the Invention

[0005] To this end, the technical problem to be solved by the present invention is to overcome the possible safety hazards of directly heating low-flash point media in the prior art, and provide a temperature control system and temperature control method for a low-flash point heat-conducting medium. The temperature control system completely isolates the heating system from the medium circulation system, and indirectly transfers heat through the high-temperature heat-conducting medium to achieve temperature control of the low-flash point heat-conducting medium. The temperature control method applies the staged control strategy and coordinated adjustment mechanism adopted by the temperature control system, which effectively solves the safety hazards and insufficient temperature control accuracy of the traditional direct heating method.

[0006] In order to solve the above technical problems, the present invention provides a temperature control system for a low-flash-point heat-conducting medium, comprising a medium circulation system, a heating system and a refrigeration system, wherein the medium circulation system and the heating system indirectly exchange heat through a heat exchanger;

[0007] The medium circulation system includes a first expansion tank, a main circulation pump, a heat exchanger and an evaporator. The first expansion tank is used to accommodate a low-flash point heat-conducting medium. The low-flash point heat-conducting medium passes through the main circulation pump, the heat exchanger and the evaporator in sequence to form a low-flash point heat-conducting medium circulation loop with an external reflux component.

[0008] The heating system includes a second expansion tank, an electric heating pipe, a high-temperature circulation pump, and a regulating valve group. The second expansion tank is used to accommodate a high-temperature heat-conducting medium. The high-temperature heat-conducting medium passes through the high-temperature circulation pump and the electric heating pipe in sequence to form a high-temperature heat-conducting medium circulation loop. The regulating valve group includes a main regulating valve and a bypass regulating valve. The outlet of the main regulating valve is connected to the heat exchanger, and the outlet of the bypass regulating valve is connected to the high-temperature heat-conducting medium circulation loop.

[0009] The electric heating pipe is completely isolated from the low-flash point heat-conducting medium. The temperature control system controls the flow of the high-temperature heat-conducting medium entering the heat exchanger by adjusting the opening ratio of the main regulating valve and the bypass regulating valve. The high-temperature heat-conducting medium and the low-flash point heat-conducting medium exchange heat in the heat exchanger, thereby indirectly adjusting the temperature of the low-flash point heat-conducting medium.

[0010] The refrigeration system is connected to the evaporator and is used to provide refrigeration capacity.

[0011] In one embodiment of the present invention, the medium circulation system further comprises a first one-way valve and a first gas-liquid separator;

[0012] The first one-way valve is provided on the outlet pipe of the first expansion tank to prevent the low-flash point heat transfer medium from flowing back;

[0013] The first gas-liquid separator is communicated with the first expansion tank, is arranged at the inlet end of the main circulation pump, and is used to separate the gas phase component and the liquid phase component in the low flash point heat transfer medium.

[0014] In one embodiment of the present invention, the heating system further comprises a second one-way valve and a second gas-liquid separator;

[0015] The second one-way valve is provided on the outlet pipe of the second expansion tank to prevent the high-temperature heat transfer medium from flowing back;

[0016] The second gas-liquid separator is communicated with the second expansion tank and is disposed at the inlet end of the high-temperature circulation pump for separating the gas phase component and the liquid phase component in the high-temperature heat-conducting medium.

[0017] In one embodiment of the present invention, the medium circulation system further comprises a liquid supply temperature sensor and a return temperature sensor;

[0018] The liquid supply temperature sensor is arranged on the pipeline between the heat exchanger and the external reflux component, and is used to monitor the temperature of the low flash point heat transfer medium about to enter the external reflux component in real time;

[0019] The reflux temperature sensor is arranged on the pipeline between the external reflux component and the evaporator, and is used to monitor the temperature of the low-flash point heat transfer medium after heat exchange through the external reflux component;

[0020] The main regulating valve adjusts its opening based on the temperature value detected by the liquid supply temperature sensor to maintain the liquid supply temperature within a preset target temperature range;

[0021] The refrigeration system adjusts the refrigeration output based on the temperature value detected by the return temperature sensor.

[0022] In one embodiment of the present invention, the heating system further comprises a heating temperature sensor, which is arranged on the pipeline between the outlet of the electric heating pipe and the regulating valve group, and is used to monitor in real time the temperature of the high-temperature heat-conducting medium after being heated by the electric heating pipe;

[0023] The electric heating pipe performs power adjustment based on the temperature value detected by the heating temperature sensor to maintain the temperature of the high-temperature heat-conducting medium within a preset target heating temperature range.

[0024] In one embodiment of the present invention, the pipeline diameters of the main regulating valve and the bypass regulating valve are the same, and are the same as the pipeline diameter of the electric heating pipe outlet; and the total flow of the main regulating valve and the bypass regulating valve is synchronously adjusted to be equal to the flow of the electric heating pipe outlet.

[0025] To solve the above technical problems, the present invention further provides a temperature control method for a low-flash-point heat-conducting medium, which is implemented by applying the above temperature control system. The temperature control method comprises the following steps:

[0026] First, start the high-temperature circulation pump of the heating system to circulate the high-temperature heat-conducting medium in a closed loop. The medium is gradually heated to 80-85% of the target temperature as the preheating temperature through the electric heating tube. After the temperature stabilizes, start the main circulation pump of the medium circulation system.

[0027] After the main circulation pump is started, the regulating valve group and the electric heating tube power are controlled synchronously to keep the main regulating valve open at 40-60%. When the temperature reaches 90-95% of the target temperature, it switches to the precise temperature control mode.

[0028] During the precise temperature control stage, a three-stage adjustment strategy is adopted: when the temperature difference is within the range of ±1°C, the current opening of the regulating valve group and the power of the electric heating tube are maintained; when the temperature difference is within the range of ±1-5°C, only the regulating valve group is controlled, and the temperature is controlled by controlling the flow of the main regulating valve and the bypass regulating valve; when the temperature difference exceeds ±5°C, the regulating valve group and the power of the electric heating tube are controlled synchronously to quickly reduce the temperature difference.

[0029] In one embodiment of the present invention, when it is necessary to switch to the cooling mode, the following steps are performed:

[0030] First, gradually reduce the opening of the main regulating valve to below 10%, and at the same time reduce the power of the electric heating tube to below 30%;

[0031] After the temperature on the high-temperature side of the heat exchanger drops below 60% of the initial temperature, start the refrigeration system;

[0032] The refrigeration system adopts a gradual power increase method when starting up. The initial power is set at 30-50% of the rated power, and then gradually increased to the target power at a rate of 5-10% per minute.

[0033] During the cooling process, the temperature change rate of the low-flash-point medium is monitored in real time. When the cooling rate exceeds 3°C / min, the refrigeration system power is automatically reduced by 10-20%.

[0034] In one embodiment of the present invention, a reflux temperature sensor is provided on the reflux pipeline of the medium circulation system to detect the temperature of the low-flash-point medium refluxed from the external components in real time;

[0035] When the system is in heating mode:

[0036] If the return temperature is detected to be higher than the upper limit of the set range, the speed of the main circulation pump will be gradually increased to increase the medium circulation flow rate and speed up the heat transfer;

[0037] If the return temperature is detected to be lower than the lower limit of the set range, the speed of the main circulation pump will be gradually reduced to slow down the medium circulation flow rate and extend the heat exchange time;

[0038] When the system is in cool down mode:

[0039] If the reflux temperature is detected to be higher than the upper limit of the set range, the speed of the main circulation pump will be gradually reduced to slow down the medium circulation flow rate and extend the cooling time;

[0040] If the return temperature is detected to be lower than the lower limit of the set range, the speed of the main circulation pump will be gradually increased to increase the medium circulation flow rate and accelerate the cooling effect.

[0041] In one embodiment of the present invention, pressure sensors are installed at key nodes of the medium circulation system to monitor the system pressure status in real time. When it is detected that the pressure at any node exceeds a preset safety threshold, a hierarchical safety response is executed:

[0042] If the pressure exceeds 110% of the rated working pressure, the main circulation pump speed will be automatically reduced by 10-20%, and the high-temperature circulation pump speed will be adjusted accordingly;

[0043] If the pressure exceeds 120% of the rated working pressure, immediately close the main regulating valve, fully open the bypass regulating valve, and reduce the power of the electric heating tube to below 30%;

[0044] If the pressure exceeds 130% of the rated working pressure, the emergency shutdown procedure will be triggered, and the electric heating pipe, main circulation pump and high-temperature circulation pump will be shut down in sequence, and the system pressure relief valve will be opened.

[0045] The above technical solution of the present invention has the following advantages over the prior art:

[0046] The temperature control system for the low-flash-point heat-conducting medium described in the present invention adopts an independent medium circulation system and heating system, which are connected by a heat exchanger. The medium circulation system is responsible for the circulation of the low-flash-point medium, while the heating system heats the high-temperature heat-conducting medium through electric heating tubes and then transfers the heat to the low-flash-point medium through the heat exchanger.

[0047] During the heat exchange process, the electric heating tubes never come into direct contact with the low-flash-point medium, thus completely avoiding the safety risks caused by local overheating. Furthermore, the introduction of a control valve group further enhances temperature control accuracy: the opening ratio of the main control valve and the bypass control valve is dynamically adjusted to control the flow of high-temperature medium entering the heat exchanger, ensuring that the temperature of the low-flash-point medium can be stably maintained within the target range. The addition of a refrigeration system ensures that the system can respond quickly when cooling is required, absorbing excess heat through the evaporator, achieving two-way temperature control.

[0048] In principle, the temperature control system of the present invention solves the safety problem of direct heating through physical isolation and indirect heat exchange, and at the same time improves the stability and response speed of temperature control by using valve group adjustment and independent circulation design; its beneficial effects are mainly reflected in three aspects: first, the complete isolation of the electric heating tube and the low-flash point medium fundamentally eliminates the risk of flash fire; second, the indirect heat exchange method makes the temperature control more uniform and avoids local overheating; finally, the design of the dynamic adjustment valve group realizes precise temperature control, meeting the high requirements for temperature stability in industrial applications.

[0049] In addition, the temperature control system of the present invention is not only suitable for low-flash-point media, but can also be extended to other fluid temperature control scenarios that are sensitive to temperature or have safety hazards, and has strong practicality and promotion value.

[0050] The temperature control method for the low-flash-point heat-conducting medium described in the present invention first establishes a stable thermal foundation through a preheating stage, and preheats the high-temperature heat-conducting medium to 80-85% of the target temperature. This design avoids the impact of sudden temperature changes on the system, and at the same time creates favorable conditions for subsequent precise temperature control; a progressive adjustment strategy is adopted in the heating stage, and by synchronously controlling the regulating valve group and the electric heating tube power, both the heating efficiency and the system stability are guaranteed; after entering the precise temperature control stage, the innovative three-stage adjustment strategy adopts different control methods according to the temperature difference range: maintaining steady-state operation within a small temperature difference range of ±1°C to reduce unnecessary adjustment actions; preferentially adjusting the valve opening within a medium temperature difference range of ±1 to 5°C, and utilizing the thermal inertia of the heat exchange system to achieve smooth adjustment; when the temperature difference exceeds ±5°C, the coordinated adjustment of the electric heating tube power is initiated to achieve rapid response. This hierarchical control strategy fully considers the physical properties of the low-flash-point heat-conducting medium and achieves the unity of safety and accuracy through the optimized control combination. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0052] Figure 1 Schematic diagram of the structure of the temperature control system of the low flash point heat conducting medium of the present invention;

[0053] Figure 2 It is a flow chart of the steps of the temperature control method of the low flash point heat conducting medium of the present invention;

[0054] Figure 3 This is a flow chart of the steps of switching the temperature control system of the low flash point heat conducting medium of the present invention from a heating mode to a cooling mode;

[0055] Figure 4 It is a flow chart of the steps of the temperature-flow rate adjustment mechanism in the temperature control method of the low flash point heat conducting medium of the present invention.

[0056] Explanation of the accompanying drawings in the specification: 1. Medium circulation system; 11. First expansion tank; 12. Main circulation pump; 13. Heat exchanger; 14. Evaporator; 15. First one-way valve; 16. First gas-liquid separator; 17. Liquid supply temperature sensor; 18. Reflux temperature sensor; 19. Pressure sensor; 2. Heating system; 21. Second expansion tank; 22. Electric heating tube; 23. High-temperature circulation pump; 241. Main regulating valve; 242. Bypass regulating valve; 25. Second one-way valve; 26. Second gas-liquid separator; 27. Heating temperature sensor; 3. Refrigeration system. DETAILED DESCRIPTION

[0057] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0058] Reference Figure 1 As shown, the present invention discloses a temperature control system for a low-flash-point heat-conducting medium, comprising a medium circulation system 1, a heating system 2 and a refrigeration system 3. The medium circulation system 1 and the heating system 2 exchange heat indirectly through a heat exchanger.

[0059] The medium circulation system 1 includes a first expansion tank 11, a main circulation pump 12, a heat exchanger 13 and an evaporator 14. The first expansion tank 11 is used to accommodate a low-flash point heat-conducting medium, such as flammable liquids such as diesel. Its function is to provide a stable medium reserve for the system and at the same time buffer the medium volume fluctuations caused by temperature changes.

[0060] After the low flash point heat transfer medium flows out of the first expansion tank 11, it is driven by the main circulation pump 12 and passes through the heat exchanger 13 and the evaporator 14 in sequence to form a complete circulation loop;

[0061] In the heat exchanger 13 , the low-flash-point medium performs indirect heat exchange with the high-temperature heat-conducting medium from the heating system 2 , absorbing heat to increase the temperature or releasing heat to decrease the temperature.

[0062] In the evaporator 14, the low-flash-point medium exchanges with the cooling energy provided by the refrigeration system 3, rapidly reducing the temperature.

[0063] After completing the heat exchange, the medium passes through external return components (such as test equipment or process pipelines), absorbs the heat continuously generated in the external return components or provides heat to the external return components, and then returns to the system to form a closed-loop flow. This design ensures that the low-flash point medium always circulates in a closed environment, avoiding direct contact with high-temperature components such as electric heating pipes, and fundamentally eliminating the risk of flash fire.

[0064] The heating system 2 includes a second expansion tank 21, an electric heating pipe 22, a high-temperature circulation pump 23 and a regulating valve group. The second expansion tank 21 is used to accommodate a high-temperature heat-conducting medium, such as a high-flash point heat-conducting oil. Its function is to provide a stable medium source for the heating system 2 and adapt to volume expansion under high temperature.

[0065] The high-temperature heat transfer medium is driven by the high-temperature circulation pump 23, flows through the electric heating tube 22 and is heated to the set temperature, and then enters the regulating valve group;

[0066] The regulating valve group includes a main regulating valve 241 and a bypass regulating valve 242:

[0067] The outlet of the main regulating valve 241 is connected to the heat exchanger 13. The main regulating valve 241 controls the flow of the medium entering the heat exchanger 13 and directly participates in heating the low flash point medium.

[0068] The outlet of the bypass regulating valve 242 is connected to the high-temperature heat-conducting medium circulation loop, and part of the high-temperature medium is directly returned to the circulation loop to form an internal circulation.

[0069] By dynamically adjusting the opening ratio of the two valves, the system can accurately control the heating capacity of the heat exchanger 13. Specifically, the opening of the main regulating valve 241 is set to a% (the range of a is 0-100), and the bypass regulating valve 242 is adjusted to (1-a%) according to the main regulating valve 241. When the supply liquid temperature is relatively high, the opening of the main regulating valve 241 is reduced and the opening of the bypass regulating valve 242 is increased. More high-temperature heat-conducting medium enters the internal circulation, the flow rate of high-temperature heat-conducting medium in the heat exchanger 13 is reduced, and the heating capacity of the medium circulation system 1 is reduced. When the supply liquid temperature is relatively low, the opening of the main regulating valve 241 is increased and the opening of the bypass regulating valve 242 is reduced. The flow rate of high-temperature medium entering the heat exchanger 13 is increased, and more high-temperature medium enters the heat exchanger 13, increasing the heating capacity of the medium circulation system 1. By controlling the flow rate of the regulating valve group, the temperature of the low-flash point medium is indirectly adjusted. The electric heating pipe 22 only heats the high-temperature heat-conducting medium and is completely isolated from the low-flash point medium, thus eliminating the potential risk of local overheating caused by directly heating the low-flash point medium.

[0070] The refrigeration system 3 is connected to the evaporator 14 and is used to provide cooling in the cooling mode: when cooling is required, the refrigeration system 3 is started, and the refrigerant exchanges heat with the low-flash point medium in the evaporator 14 and quickly absorbs its heat. At this time, the main regulating valve 241 of the heating system 2 is closed, and the high-temperature medium only circulates through the bypass valve to avoid interfering with the refrigeration process.

[0071] The coordinated operation of the refrigeration system 3 and the medium circulation system 1 enables seamless switching of the system between heating and cooling modes, ensuring rapid response and stability of temperature control.

[0072] Specifically, in this embodiment, although a basic circulation loop is formed by the main circulation pump 12, the heat exchanger 13 and the evaporator 14, there may be two key problems in actual operation: first, the low-flash point medium is prone to vaporization when the temperature changes, resulting in gas-liquid two-phase flow affecting the normal operation of the pump; second, when the system is shut down, the medium may flow back due to gravity, causing equipment damage. To solve these problems, this embodiment adds two key components, a first one-way valve 15 and a first gas-liquid separator 16, to the medium circulation system 1.

[0073] The first one-way valve 15 is carefully arranged on the outlet pipeline of the first expansion tank 11. Its one-way conduction characteristic effectively prevents the backflow of the medium, especially when the system is shut down or the pressure fluctuates. This design avoids the impact of the backflow of the medium on the expansion tank and the pipeline.

[0074] The first gas-liquid separator 16 is arranged at the inlet end of the main circulation pump 12, forming a connecting structure with the first expansion tank 11. This position selection has been carefully considered and can effectively separate the gas phase components generated by temperature changes in the medium before it enters the circulation pump.

[0075] When the medium containing bubbles enters the gas-liquid separator, the lighter gas phase components are separated into the upper space, while the pure liquid phase medium flows out from the bottom to supply the main circulation pump 12. This process ensures that the pump always operates in a pure liquid phase medium environment, significantly improving the operating efficiency and life of the pump.

[0076] The synergistic effect of these two newly added components enables the system to show better adaptability when facing medium phase change and pressure fluctuation. The first one-way valve 15 ensures the stability of the medium flow direction, while the first gas-liquid separator 16 ensures the uniformity of the medium quality. From the actual effect, this design not only solves the potential cavitation risks and backflow problems in the basic system, but also indirectly improves the temperature control accuracy of the entire system by maintaining a stable medium state; especially when dealing with low-flash point media, which are working fluids that are sensitive to temperature changes, the addition of the first one-way valve 15 and the first gas-liquid separator 16 enables the medium circulation system 1 to maintain stable operation within a wider temperature range, while reducing the control difficulty caused by medium phase change, and providing a more reliable implementation guarantee for the basic temperature control function.

[0077] Similarly, there are also key issues that need to be improved during the actual operation of the heating system 2. Especially under high-temperature conditions, the high-temperature heat-conducting medium is prone to vaporization due to temperature fluctuations. If these bubbles enter the circulation pump, they will cause cavitation damage. At the same time, when the system is shut down, the high-temperature medium may flow back due to pressure changes, affecting the service life of the equipment. In order to solve these problems, two key components, a second one-way valve 25 and a second gas-liquid separator 26, are also added to the heating system 2.

[0078] The second one-way valve 25 is precisely installed on the outlet pipe of the second expansion tank 21. Its unique one-way conduction design effectively blocks the possibility of backflow of high-temperature medium under any abnormal working conditions, especially when the system suddenly stops or the pressure fluctuates. This design avoids the impact of the backflow of high-temperature medium on key components such as the expansion tank and the electric heating pipe 22;

[0079] The second gas-liquid separator 26 is carefully arranged at the inlet end of the high-temperature circulation pump 23, forming a connecting structure with the second expansion tank 21. This position selection has been strictly calculated and can effectively separate the gas phase components generated by temperature changes in the high-temperature medium before it enters the circulation pump.

[0080] When the high-temperature medium flows through the gas-liquid separator, the lighter gas phase components are efficiently separated into the upper space, while the pure liquid phase medium flows out steadily from the bottom to supply the high-temperature circulation pump 23. This process ensures that the pump always operates under the best working conditions.

[0081] The coordinated operation of these two newly added components enables the heating system 2 to exhibit greater stability in the face of high-temperature medium phase changes and pressure fluctuations. The second one-way valve 25 ensures the certainty of the medium flow direction, while the second gas-liquid separator 26 optimizes the medium quality. From the actual operating results, this design not only solves the cavitation risks and backflow hazards existing in the basic system, but also significantly improves the temperature control accuracy and response speed of the entire system by maintaining the stable state of the high-temperature medium. Especially when dealing with high-temperature heat-conducting media, which are easily vaporized working fluids, the addition of the second one-way valve 25 and the second gas-liquid separator 26 enables the heating system 2 to maintain reliable operation within a higher temperature range, while greatly reducing the control difficulty caused by medium phase change, providing more powerful implementation support for the basic temperature control function.

[0082] In the medium circulation system 1 of this embodiment, although the basic function of indirect heat exchange is achieved through the heat exchanger 13, there are two key control difficulties in actual operation: first, it is difficult to grasp the actual temperature of the medium entering the external reflux component in real time, and second, it is impossible to accurately evaluate the temperature change of the medium after external heat exchange. These problems result in the system being able to only perform open-loop or semi-closed-loop control, making it difficult to achieve precise temperature regulation. To solve these control difficulties, two key detection elements, a liquid supply temperature sensor 17 and a return temperature sensor 18, are added to the medium circulation system 1.

[0083] The supply temperature sensor 17 is strategically placed in a key pipeline between the heat exchanger 13 and the external return flow component. This location, carefully selected after rigorous validation, accurately captures the real-time temperature of the medium entering the external device. The return temperature sensor 18, located in the pipeline between the external return flow component and the evaporator 14, precisely monitors changes in the medium's temperature after external heat exchange. These two sensors form a complete temperature monitoring network. The main control valve 241 dynamically adjusts based on real-time feedback from the supply temperature sensor 17, maintaining the supply temperature within a preset target range through control algorithms such as PID. The refrigeration system 3 intelligently adjusts the cooling output based on the detection value of the return temperature sensor 18, forming a closed-loop control system.

[0084] This dual-sensor collaborative design enables the system to perceive the actual heat exchange effect of the medium in the external reflux component in real time, and dynamically adjust the operating parameters according to the heat exchange demand. From the actual operating effect, it not only solves the temperature control lag problem existing in the basic system, but also enables the system to respond quickly to changes in external heat exchange load by establishing a complete temperature feedback mechanism; especially when dealing with low-flash point media, which are working fluids that are sensitive to temperature fluctuations, this precise temperature monitoring and control design enables the system to maintain stable temperature control performance under more stringent working conditions.

[0085] In the heating system 2 of this embodiment, although the basic heating function of the high-temperature heat-conducting medium is achieved through the electric heating tube 22 and the regulating valve group, there is a key control defect in actual operation: the actual temperature of the high-temperature medium at the outlet of the electric heating tube 22 cannot be accurately monitored in real time, resulting in lag and inaccuracy in the heating control, which may cause excessive temperature fluctuations or energy waste; to solve this control problem, a heating temperature sensor 27, a key detection element, is added to the heating system 2. The sensor is carefully arranged in the key pipeline between the outlet of the electric heating tube 22 and the regulating valve group. This position selection has been strictly considered and can accurately capture the real-time temperature of the high-temperature medium after being heated by the electric heating tube 22.

[0086] Based on real-time temperature feedback from the heating temperature sensor 27, the electric heating pipe 22 dynamically adjusts the heating power through an intelligent control algorithm, so that the temperature of the high-temperature medium is strictly maintained within the preset target heating temperature range. This closed-loop control mechanism enables the system to sense the heating effect in real time and quickly adjust the output of the electric heating pipe 22 based on the actual temperature deviation. From the actual operating results, it not only solves the problem of inaccurate heating control existing in the basic system, but also significantly improves the response speed and temperature stability of the heating system 2 by establishing a real-time temperature feedback adjustment mechanism. Especially when dealing with high-temperature heat-conducting mediums, which are working fluids with strict temperature control requirements, this precise temperature monitoring and control design enables the system to achieve more accurate heating control while ensuring safety.

[0087] In this embodiment, the basic control function of the high-temperature medium flow is achieved by the regulating valve group. In actual operation, it is also necessary to consider that the difference in pipe diameters between the main regulating valve 241 and the bypass regulating valve 242 or the mismatch with the outlet of the electric heating pipe 22 may lead to uneven flow distribution, resulting in throttling effect and pressure fluctuation, affecting the system heat exchange efficiency and temperature control accuracy; for this purpose, the regulating valve group is precisely designed for fluid matching, and it is stipulated that the pipe diameters of the main regulating valve 241 and the bypass regulating valve 242 remain the same and are strictly consistent with the pipe diameter of the outlet of the electric heating pipe 22.

[0088] This equal-diameter design ensures balanced flow resistance of the fluid in the branch pipes, avoiding eddy currents and pressure losses caused by sudden changes in pipe diameter. Furthermore, in this embodiment, a flow balance control principle is proposed. By synchronously adjusting the openings of the main regulating valve 241 and the bypass regulating valve 242, the total flow of the two is always equal to the flow at the outlet of the electric heating pipe 22. This design concept fundamentally eliminates the common problem of uneven flow distribution in traditional systems. From the actual operating results, it not only solves the problem of inaccurate fluid control in the basic system, but also significantly improves the heat exchange efficiency and temperature stability of the system by establishing a strict flow conservation mechanism.

[0089] Reference Figure 2As shown, based on the above embodiment, the present invention also discloses a temperature control method for a low-flash-point heat-conducting medium, which is implemented by applying the above temperature control system and achieving a safe and efficient temperature control effect through a systematic process step design. The temperature control method includes the following steps:

[0090] First, start the high-temperature circulation pump 23 of the heating system 2 to circulate the high-temperature heat-conducting medium in the closed loop, and gradually heat the medium to 80-85% of the target temperature as the preheating temperature through the electric heating tube 22. After the temperature stabilizes, start the main circulation pump 12 of the medium circulation system 1.

[0091] The key to this design step is to first establish a stable high-temperature medium circulation system 1 to avoid temperature shock caused by the intense heat exchange between the cold and hot media when the main circulation pump 12 is directly started. Preheating to 80-85% of the target temperature ensures subsequent heating efficiency while leaving ample room for adjustment. This gradual startup significantly improves system stability while avoiding potential safety hazards caused by sudden temperature changes.

[0092] After the main circulation pump 12 is started, the power of the regulating valve group and the electric heating tube 22 is synchronously controlled to keep the main regulating valve 241 open at 40-60%. When the temperature reaches 90-95% of the target temperature, it enters the precise temperature control mode.

[0093] During this stage, a medium-opening main regulating valve 241 design is adopted, which not only ensures sufficient heat transfer but also avoids the impact of sudden flow changes on the system. The opening range of 40% to 60% has been optimized and tested, and can achieve the best balance between heating efficiency and system stability; synchronously adjusting the power of the electric heating tube 22 ensures the stable output of the heat source. This coordinated control method enables the system to heat up smoothly according to the preset curve, avoiding the temperature overshoot phenomenon common in traditional methods, and laying a good foundation for subsequent precise temperature control.

[0094] In the precise temperature control stage, an innovative three-stage adjustment strategy is adopted:

[0095] When the temperature difference is within ±1°C, the current state is maintained. This "steady-state maintenance" within a small temperature difference range reduces unnecessary adjustment actions and increases system life.

[0096] When the temperature difference is within the range of ±1-5℃, only the valve opening is adjusted, and the thermal inertia of the heat exchange system is used to achieve smooth regulation. This single parameter adjustment method simplifies the control logic.

[0097] When the temperature difference exceeds ±5°C, the valve and the electric heating tube 22 are activated for coordinated adjustment. This rapid response mechanism in emergency situations ensures the stability of the system.

[0098] The temperature control method using graded processing fully considers the system characteristics within different temperature difference ranges, and achieves precise temperature control through the optimized control combination, which not only ensures the response speed but also avoids the increase in energy consumption and equipment wear caused by excessive adjustment.

[0099] Specifically, the temperature control method of this embodiment is based on the above-mentioned temperature control system. It is necessary to control not only the heating temperature but also the cooling temperature. There is no specific solution for the transition control when the system switches from heating mode to cooling mode. This control gap may lead to safety hazards such as sudden temperature drop and thermal shock. To solve this key control problem, refer to Figure 3 As shown, a complete set of cooling mode switching processes is also proposed in this embodiment.

[0100] First, by gradually reducing the opening of the main regulating valve 241 to below 10% and simultaneously reducing the power of the electric heating tube 22 to below 30%, a smooth load reduction of the heating system 2 is achieved. This step-by-step load reduction strategy avoids sudden changes in system pressure; the refrigeration system 3 is started after the temperature on the high-temperature side of the heat exchanger 13 drops to a critical threshold below 60% of the initial temperature. The selection of this temperature node ensures that the system is in a safe thermal equilibrium state; the refrigeration system 3 is started using a progressive power increase method, starting from 30-50% of the rated power and gradually increasing at a rate of 5-10% per minute. This slow start design effectively prevents thermal shock of the refrigerant on the evaporator 14; the intelligent control mechanism that monitors the temperature change rate in real time and dynamically adjusts the refrigeration power during the cooling process ensures a smooth and controllable cooling process.

[0101] This systematic cooling control design achieves seamless integration between the heating system 2 and the cooling system 3 through a phased, progressive operating strategy. Strict logical associations and status judgment conditions are established between each step. This not only solves the problem of inconsistent mode switching in the basic method, but also enables the system to achieve smooth mode conversion and precise temperature control while ensuring safety by establishing a complete cooling control process. Especially when dealing with low-flash point media, a working fluid that is sensitive to temperature changes, this refined cooling control design effectively avoids the temperature drop and thermal stress problems common in traditional methods.

[0102] Furthermore, the temperature control method of this embodiment is to control the temperature of the flowing medium. Figure 4 As shown, based on the above embodiment, a temperature-flow rate adjustment mechanism is introduced to target this feature. Specifically, the temperature sensor provided on the return line can accurately capture the actual temperature of the medium after external heat exchange. The acquisition of this key parameter provides the system with a direct basis for evaluating the external heat exchange effect.

[0103] Among them: in the heating mode, when the reflux temperature is high, higher than the upper limit of the set range, the design of increasing the speed of the main circulation pump 12 enhances the heat transfer efficiency of the heat exchanger 13 by increasing the flow rate of the low-flash point heat transfer medium; and when the reflux temperature is low, lower than the lower limit of the set range, the operation of reducing the flow rate prolongs the residence time of the low-flash point heat transfer medium in the heat exchanger 13, thereby improving the heat transfer capacity of a single cycle. This differentiated adjustment fully considers the heat transfer characteristics under heating conditions and achieves a precise match between flow rate and heat exchange requirements.

[0104] The reverse regulation logic in the cooling mode reflects the special optimization of the refrigeration conditions. The flow rate is reduced during high-temperature reflux to enhance the cooling effect, and the flow rate is increased during low-temperature reflux to avoid overcooling.

[0105] This intelligent identification and automatic adjustment mechanism based on working mode enables the system to autonomously adapt to changes in external heat exchange conditions. Each adjustment action is based on strict temperature feedback and working condition judgment. By establishing a closed-loop temperature-flow rate adjustment mechanism, the system can not only control the temperature according to actual heat exchange, but also coordinately control the flow rate of the system's low-flash point heat transfer medium.

[0106] Specifically, in this embodiment, the upper and lower limits of the reflux temperature setting range are comprehensively determined by the three dimensions of the system's thermodynamic characteristics, safety requirements and process requirements; from the perspective of thermodynamic characteristics, the setting of the upper and lower limits first considers the phase change characteristics of the low-flash-point medium to ensure that the operating temperature is always far away from the flash point and boiling point of the medium. Usually, the lower limit is set to a safety margin of 15-20°C higher than the flash point of the medium, while the upper limit is controlled within the range of 10-15°C lower than the boiling point; in terms of safety requirements, the setting range needs to meet the pressure bearing capacity of the equipment and the temperature tolerance limit of the sealing material. For example, for a system with a rated working pressure of 1.6MPa, the upper limit temperature generally does not exceed 150°C to avoid overpressure risks; the process requirement dimension is determined according to the specific application scenario. For precision temperature control occasions, the upper and lower limit ranges are usually set to a narrow fluctuation of ±2°C of the target temperature; for ordinary industrial applications, it can be relaxed to ±5°C to reduce energy consumption.

[0107] Specifically, in practical applications, the safety of the entire temperature control system must also be considered. Although a complete temperature control strategy has been established, there is a lack of targeted protection measures for potential safety hazards caused by system pressure fluctuations. The lack of such safety monitoring may lead to equipment damage or medium leakage risks. To address this key safety issue, a set of graded pressure response mechanisms is also constructed in the temperature control method of this embodiment. By setting pressure sensors 19 at key nodes of the medium circulation system 1, all-round real-time monitoring of the system pressure is achieved.

[0108] Specifically, when the pressure exceeds the primary threshold of 110% of the rated operating pressure (derived from a comprehensive assessment of the system's mechanical strength, medium properties, and process requirements; each temperature control system has a specific rated operating pressure), the system automatically reduces the speed of the main circulation pump 12 by 10-20% and simultaneously adjusts the speed of the high-temperature circulation pump 23. This gentle speed reduction mitigates the rising pressure trend and avoids drastic fluctuations in system operation. If the pressure continues to climb to the secondary threshold of 120%, the system immediately implements more stringent protection measures. The operation of closing the main regulating valve 241 and fully opening the bypass regulating valve 242 effectively diverts system flow and reduces the power of the electric heating pipe 22 to below 30%, quickly reducing the heat load. When the pressure reaches the emergency threshold of 130%, the system activates the highest level of safety protection, executing an emergency shutdown in the order of the electric heating pipe 22, the main circulation pump 12, and the high-temperature circulation pump 23. This orderly shutdown sequence avoids pressure shock, and the opening of the pressure relief valve provides a rapid pressure relief channel for the system.

[0109] This hierarchical response design concept enables the system to adopt the most appropriate response strategy according to the degree of pressure abnormality by setting up gradually upgraded protection measures. Each response level maintains a strict logical progressive relationship while reserving sufficient buffer space. It not only solves the problem of insufficient safety protection, but also enables the system to maintain safe operation or orderly shutdown under various abnormal working conditions by establishing an intelligent pressure monitoring and response system.

[0110] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A temperature control system for a low-flash-point heat-conducting medium, characterized in that: It includes a medium circulation system, a heating system and a refrigeration system, wherein the medium circulation system and the heating system indirectly exchange heat through a heat exchanger; The medium circulation system includes a first expansion tank, a main circulation pump, a heat exchanger and an evaporator. The first expansion tank is used to accommodate a low-flash point heat-conducting medium. The low-flash point heat-conducting medium passes through the main circulation pump, the heat exchanger and the evaporator in sequence to form a low-flash point heat-conducting medium circulation loop with an external reflux component. The heating system includes a second expansion tank, an electric heating pipe, a high-temperature circulation pump, and a regulating valve group. The second expansion tank is used to accommodate a high-temperature heat-conducting medium. The high-temperature heat-conducting medium passes through the high-temperature circulation pump and the electric heating pipe in sequence to form a high-temperature heat-conducting medium circulation loop. The regulating valve group includes a main regulating valve and a bypass regulating valve. The outlet of the main regulating valve is connected to the heat exchanger, and the outlet of the bypass regulating valve is connected to the high-temperature heat-conducting medium circulation loop. The electric heating pipe is completely isolated from the low-flash point heat-conducting medium. The temperature control system controls the flow of the high-temperature heat-conducting medium entering the heat exchanger by adjusting the opening ratio of the main regulating valve and the bypass regulating valve. The high-temperature heat-conducting medium and the low-flash point heat-conducting medium exchange heat in the heat exchanger, thereby indirectly adjusting the temperature of the low-flash point heat-conducting medium. The refrigeration system is connected to the evaporator and is used to provide refrigeration capacity.

2. The temperature control system for low-flash-point heat-conducting medium according to claim 1, characterized in that: The medium circulation system further includes a first one-way valve and a first gas-liquid separator; The first one-way valve is provided on the outlet pipe of the first expansion tank to prevent the low-flash point heat transfer medium from flowing back; The first gas-liquid separator is communicated with the first expansion tank, is arranged at the inlet end of the main circulation pump, and is used to separate the gas phase component and the liquid phase component in the low flash point heat transfer medium.

3. The temperature control system for low-flash-point heat-conducting medium according to claim 1, characterized in that: The heating system further includes a second one-way valve and a second gas-liquid separator; The second one-way valve is provided on the outlet pipe of the second expansion tank to prevent the high-temperature heat transfer medium from flowing back; The second gas-liquid separator is communicated with the second expansion tank and is disposed at the inlet end of the high-temperature circulation pump for separating the gas phase component and the liquid phase component in the high-temperature heat-conducting medium.

4. The temperature control system for low-flash-point heat-conducting medium according to claim 1, characterized in that: The medium circulation system also includes a liquid supply temperature sensor and a return temperature sensor; The liquid supply temperature sensor is arranged on the pipeline between the heat exchanger and the external reflux component, and is used to monitor the temperature of the low flash point heat transfer medium about to enter the external reflux component in real time; The reflux temperature sensor is arranged on the pipeline between the external reflux component and the evaporator, and is used to monitor the temperature of the low-flash point heat transfer medium after heat exchange through the external reflux component; The main regulating valve adjusts its opening based on the temperature value detected by the liquid supply temperature sensor to maintain the liquid supply temperature within a preset target temperature range; The refrigeration system adjusts the refrigeration output based on the temperature value detected by the return temperature sensor.

5. The temperature control system for low-flash-point heat-conducting medium according to claim 1, characterized in that: The heating system further includes a heating temperature sensor, which is arranged on the pipeline between the electric heating pipe outlet and the regulating valve group, and is used to monitor the temperature of the high-temperature heat-conducting medium after the electric heating pipe is heated in real time; The electric heating pipe performs power adjustment based on the temperature value detected by the heating temperature sensor to maintain the temperature of the high-temperature heat-conducting medium within a preset target heating temperature range.

6. The temperature control system for low-flash-point heat-conducting medium according to claim 1, characterized in that: The pipe diameters of the main regulating valve and the bypass regulating valve are the same, and are the same as the pipe diameter of the electric heating pipe outlet; and the total flow of the main regulating valve and the bypass regulating valve is equal to the flow of the electric heating pipe outlet by synchronously regulating.

7. A method for controlling the temperature of a low-flash-point heat-conducting medium, implemented by using the temperature control system according to any one of claims 1 to 6, characterized in that: The temperature control method comprises the following steps: First, start the high-temperature circulation pump of the heating system to circulate the high-temperature heat-conducting medium in a closed loop. The medium is gradually heated to 80-85% of the target temperature as the preheating temperature through the electric heating tube. After the temperature stabilizes, start the main circulation pump of the medium circulation system. After the main circulation pump is started, the regulating valve group and the electric heating tube power are controlled synchronously to keep the main regulating valve open at 40-60%. When the temperature reaches 90-95% of the target temperature, it switches to the precise temperature control mode. During the precise temperature control stage, a three-stage adjustment strategy is adopted: when the temperature difference is within the range of ±1°C, the current opening of the regulating valve group and the power of the electric heating tube are maintained; when the temperature difference is within the range of ±1-5°C, only the regulating valve group is controlled, and the temperature is controlled by controlling the flow of the main regulating valve and the bypass regulating valve; when the temperature difference exceeds ±5°C, the regulating valve group and the power of the electric heating tube are controlled synchronously to quickly reduce the temperature difference.

8. The temperature control method of a low-flash-point heat-conducting medium according to claim 7, characterized in that: When you need to switch to cooling mode, perform the following steps: First, gradually reduce the opening of the main regulating valve to below 10%, and at the same time reduce the power of the electric heating tube to below 30%; After the temperature on the high-temperature side of the heat exchanger drops below 60% of the initial temperature, start the refrigeration system; The refrigeration system adopts a gradual power increase method when starting up. The initial power is set at 30-50% of the rated power, and then gradually increased to the target power at a rate of 5-10% per minute. During the cooling process, the temperature change rate of the low-flash-point medium is monitored in real time. When the cooling rate exceeds 3°C / min, the refrigeration system power is automatically reduced by 10-20%.

9. The temperature control method of a low-flash-point heat-conducting medium according to claim 7, characterized in that: A reflux temperature sensor is installed on the reflux pipeline of the medium circulation system to detect the temperature of the low-flash point medium returning from the external components in real time; When the system is in heating mode: If the return temperature is detected to be higher than the upper limit of the set range, the speed of the main circulation pump will be gradually increased to increase the medium circulation flow rate and speed up the heat transfer; If the return temperature is detected to be lower than the lower limit of the set range, the speed of the main circulation pump will be gradually reduced to slow down the medium circulation flow rate and extend the heat exchange time; When the system is in cool down mode: If the reflux temperature is detected to be higher than the upper limit of the set range, the speed of the main circulation pump will be gradually reduced to slow down the medium circulation flow rate and extend the cooling time; If the return temperature is detected to be lower than the lower limit of the set range, the speed of the main circulation pump will be gradually increased to increase the medium circulation flow rate and accelerate the cooling effect.

10. The temperature control method of a low-flash-point heat-conducting medium according to claim 7, characterized in that: Pressure sensors are installed at key nodes of the medium circulation system to monitor the system pressure status in real time. When the pressure at any node exceeds the preset safety threshold, a hierarchical safety response is executed: If the pressure exceeds 110% of the rated working pressure, the main circulation pump speed will be automatically reduced by 10-20%, and the high-temperature circulation pump speed will be adjusted accordingly; If the pressure exceeds 120% of the rated working pressure, immediately close the main regulating valve, fully open the bypass regulating valve, and reduce the power of the electric heating tube to below 30%; If the pressure exceeds 130% of the rated working pressure, the emergency shutdown procedure will be triggered, and the electric heating pipe, main circulation pump and high-temperature circulation pump will be shut down in sequence, and the system pressure relief valve will be opened.

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