Liquid nitrogen spray cooling test system

Abstract

The invention provides an integrated liquid nitrogen spray cooling test system which is mainly composed of a liquid nitrogen supply module, a heat source simulation module, a spray atomization module, a visual monitoring module, a temperature acquisition and control module and a spray cavity module. According to the system, temperature sensors arranged at multiple points are combined with a fuzzy PID control strategy, so that the temperature of the heat sink is accurately adjusted; and through the adjustability of the spraying height and the arrangement design of multiple nozzles, the spraying uniformity and the cooling efficiency are effectively improved. In addition, a low-temperature flowmeter and a low-temperature electromagnetic valve are integrated in the system, and real-time monitoring and fine control over the liquid nitrogen flow are achieved. Experimental results show that the system can realize stable operation under various spray parameter working conditions, has good heat exchange performance testing capability, and is suitable for cooling requirements under high heat flux density conditions. The test platform has the advantages of compact structure, high control precision, perfect monitoring means and the like, and provides reliable support for deep research and engineering application of a liquid nitrogen spray cooling technology.

Description

Technical Field

[0001] The present invention relates to low-temperature spray cooling technology, and specifically to a spray heat exchange performance test system based on liquid nitrogen as a cooling medium. By precisely controlling the liquid nitrogen flow rate, spray height, nozzle particle size and number, combined with high-precision temperature acquisition and visual monitoring, the stability and reliability of the liquid nitrogen spray process are ensured. The system is suitable for studying the heat transfer characteristics and related parameter optimization during liquid nitrogen spray cooling, as well as spray cooling optimization research in high heat flux density heat dissipation scenarios. Background Art

[0002] Liquid nitrogen spray cooling technology, as a highly efficient low-temperature heat exchange method, is widely used in aerospace, electronic device cooling, superconductor cooling, cryogenic wind tunnels, and other fields. Based on the rapid evaporation and heat absorption characteristics of liquid nitrogen, it can achieve effective temperature control and uniform cooling of high-heat-load components. Existing liquid nitrogen spray cooling devices suffer from defects such as inaccurate spray parameter control, insufficient heat exchange process monitoring, and unstable cooling effects, making it difficult to meet system requirements under high heat flux conditions. In particular, when it comes to fine-tuning key parameters such as spray height, droplet size, spray flow rate, and nozzle arrangement, existing technologies lack a unified, systematic experimental platform for in-depth research.

[0003] Liquid nitrogen spray cooling technology holds broad application prospects in thermal management applications in high-heat-load environments. However, current technology suffers from issues such as insufficient liquid nitrogen spray flow control precision, uneven spray coverage, and delayed temperature control response. These issues hinder stable and efficient cooling performance under complex thermal conditions. In particular, under multi-parameter coupling conditions (such as spray flow rate, spray height, droplet size, and number of nozzles), the lack of an experimental platform capable of systematic and quantitative research has limited in-depth exploration of the coupling mechanisms between spray parameters and heat transfer performance.

[0004] In existing technologies, factors such as uneven spray distribution, dynamic lag in the measurement and control system, and thermal interference introduced by the device structure severely impact the accuracy and repeatability of experimental results. Current equipment generally lacks the ability to monitor the spray process in real time, collect data on key parameters, and perform closed-loop control, further hindering the development of liquid nitrogen spray cooling systems in terms of performance optimization and engineering applications. Therefore, designing a liquid nitrogen spray cooling test platform with a rational structure, comprehensive data collection, and precise control is of great significance. Summary of the Invention

[0005] To solve the above problems, the present invention provides a liquid nitrogen spray cooling test system with a compact structure, precise control, and complete visual monitoring. It can dynamically adjust the spray parameters, accurately measure the heat exchange performance, and is suitable for experimental needs of various nozzle combinations.

[0006] An integrated liquid nitrogen spray cooling test system includes: (1) an insulated liquid nitrogen storage bottle, (2) a cryogenic shut-off valve, (3) a Coriolis cryogenic flowmeter, (4) a cryogenic solenoid valve, (5) an insulated delivery pipeline, (6) a liquid nitrogen nozzle, (7) an endoscope camera, (8) a thermocouple, (9) a copper heat sink, (10) an alumina ceramic heating plate, (11) a PT100 thermal resistor temperature acquisition module, (12) a signal output adapter, (13) a power supply, (14) an H-bridge motor driver module, (15) an H-bridge motor driver module, (16) a PWM signal output, (17) an industrial control host, and (18) an ESP32-S3 main control chip.

[0007] In a preferred embodiment of the present invention, the overall process of the liquid nitrogen spray cooling test system is as follows: the insulated liquid nitrogen storage bottle (1) transports liquid nitrogen to the liquid nitrogen nozzle (6) through the heat-insulating delivery pipeline (5), and the nozzle sprays liquid nitrogen onto the surface of the copper heat sink block (9) of the heat source simulation module. The PT100 thermal resistor temperature acquisition module (11) is distributed inside the heat sink block, and the signal is transmitted to the ESP32-S3 main control chip (18) via the RS485 bus through the temperature acquisition module. The main control board adjusts the power of the alumina ceramic heating plate (10) and the spray solenoid valve switch, and the data is fed back to the industrial control host (17) to realize real-time monitoring and parameter setting.

[0008] In a preferred embodiment of the present invention, the (18) ESP32-S3 main control chip is connected to the (11) PT100 thermal resistor temperature acquisition module, the (3) Coriolis low-temperature flowmeter, the (10) alumina ceramic heater, the (14) H-bridge motor driver module, the (15) H-bridge motor driver module, and the (4) low-temperature solenoid valve via an RS485 interface. The (18) ESP32-S3 main control chip regulates the heater power and spray control via a PWM signal, and is serially connected to the (17) industrial control host computer to achieve human-computer interaction.

[0009] In a preferred embodiment of the present invention, the (7) endoscopic camera is fixed to the side of the cavity, and LED lights surround the camera to ensure that the spray area is bright and uniform, meeting the requirements of high-definition shooting.

[0010] In a preferred embodiment of the present invention, the cavity is made of polytetrafluoroethylene, filled with a polyurethane insulation layer, and has a pressure relief hole at the bottom. (7) An endoscope camera and an LED light are installed on the top, and (6) a liquid nitrogen nozzle can adjust the spray height.

[0011] The present invention has the following advantages: 1. The entire device uses a computer control system for flow rate control, improving production efficiency. 2. The cryogenic chamber can achieve a low-temperature environment of -196°C, which can be selected according to needs, saving materials and being energy-efficient and environmentally friendly. 3. The liquid nitrogen atomization process is fully carried out, saving equipment investment and material consumption, while also improving productivity and the quality of processed workpieces. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The present invention is further described below with reference to the accompanying drawings and embodiments. Figure 1 This is a flow chart of the liquid nitrogen spray cooling test system of the present invention. It shows the overall device layout, including the liquid nitrogen storage bottle, spray chamber, heat source module, control module, and touch screen layout.

[0013] (1) Insulated liquid nitrogen storage bottle, (2) Cryogenic shut-off valve, (3) Coriolis cryogenic flowmeter, (4) Cryogenic solenoid valve, (5) Insulated delivery pipeline, (6) Solid conical nozzle, (7) Endoscopic camera, (8) Thermocouple, (9) Copper block, (10) Alumina ceramic heating plate, (11) PT100 thermal resistor temperature acquisition module, (12) Signal output adapter, (13) Power supply, (14) H-bridge motor driver module, (15) H-bridge motor driver module, (16) PWM signal output, (17) Industrial control host, (18) ESP32-S3 main control chip DETAILED DESCRIPTION

[0014] like Figure 1The (1) insulated liquid nitrogen storage bottle is equipped with an insulated double-layer structure, and the liquid nitrogen inside is kept at a low temperature of -196°C. The liquid nitrogen is transported through the (5) insulated transmission pipeline, and the outer layer of the pipeline is wrapped with a polyurethane insulation layer and low-radiation aluminum foil to reduce the heat transfer from the outside. At the end of the pipeline, there are (4) low-temperature solenoid valves and (2) low-temperature stop valves, which are used for on-off control and flow regulation respectively to ensure the stability of the liquid nitrogen flow at the nozzle. The heat source simulation module (HS-Block) uses (10) alumina ceramic heating plate with a size of 50×50×3 mm and a maximum power of 1000W. The voltage and power are adjustable through the controller. The bottom of the heating plate is bonded to the (9) copper block with high thermal conductivity silicone grease. The heat sink has a size of 50×50×25 mm and a thermal conductivity of 401 W / (m·K), ensuring that heat is evenly transferred to the spray surface. The remaining surface of the heat sink is covered with thermal insulation foam to achieve effective insulation and prevent heat loss. The spray atomization module (Spray-Control) uses a (6) solid cone nozzle produced by Jie Li Spray Technology, with a standard 1 / 8 inch interface and nozzle diameters of 0.8mm, 1.0mm, 1.5mm and 2.0mm. The nozzle is connected to the liquid nitrogen pipeline through a three-way splitter, supporting single nozzle to multi-nozzle combination arrangement. The spray height is adjusted by the Z-axis guide mechanical lifting structure, with a lifting range of 60-120mm and an adjustment accuracy of 0.5mm. The spray coverage is uniform and meets different working conditions. The visual monitoring module is installed on the top of the spray chamber (7) endoscope camera with a resolution of 1600×1200 pixels and 8 LED lights to achieve clear real-time acquisition of the spray process. The image data is transmitted to the (17) industrial control host for real-time analysis and storage. The temperature acquisition and control module (Temp-Control) has three layers of (11) PT100 thermal resistor temperature acquisition modules distributed along the axial direction of the heat sink, with two (8) thermocouples arranged on each layer, all coated with low-temperature thermal grease. After the sensor signal is converted by the (11) PT100 thermal resistor temperature acquisition module, it is transmitted to the (18) ESP32-S3 main control chip via the high-speed RS485 bus using the Modbus RTU protocol. The main control board has an embedded fuzzy PID control algorithm that adjusts the (16) PWM signal output power control (10) alumina ceramic heating plate output and spray solenoid valve switch according to temperature feedback to achieve precise temperature control. Human-computer interaction is completed through the 10-inch serial port (17) industrial control host. The interface supports temperature setting, spray parameter adjustment and real-time data display. The spray chamber module uses a 12mm thick polytetrafluoroethylene plate with dimensions of 500×500×500 mm. The inner cavity is filled with a 100mm thick polyurethane insulation layer. A 10mm diameter pressure relief hole is set at the bottom to maintain the chamber pressure stable. The spray target plate inside the cavity can be replaced to meet diverse test needs. In this embodiment, through the organic combination of the above structure and control method, high-precision monitoring and control of the liquid nitrogen spray cooling process is achieved, the stability and repeatability of the experimental data are ensured, and the requirements of multi-parameter and multi-operating condition heat transfer performance research are met.

Claims

1. A liquid nitrogen spray cooling test system, characterized by: (1) Insulated liquid nitrogen storage bottle, (2) Cryogenic shut-off valve, (3) Coriolis cryogenic flowmeter, (4) Cryogenic solenoid valve, (5) Insulated delivery pipeline, (6) Solid conical nozzle, (7) Endoscopic camera, (8) Thermocouple, (9) Copper block, (10) Alumina ceramic heating plate, (11) PT100 thermal resistor temperature acquisition module, (12) Signal output adapter, (13) Power supply, (14) H-bridge motor driver module, (15) H-bridge motor driver module, (16) PWM signal output, (17) Industrial control host, (18) ESP32-S3 main control chip.

2. A liquid nitrogen spray cooling test system according to claim 1, characterized in that: The liquid nitrogen supply module (LN-Supply) is provided with (1) an insulated liquid nitrogen storage bottle, (5) an insulated delivery pipeline and (2) a low-temperature stop valve, wherein the pipeline is wrapped with an insulation layer and low-emissivity aluminum foil; the heat source simulation module (HS-Block) includes a (9) copper heat sink block coupled with a (10) alumina ceramic heating plate, and the power of the (10) alumina ceramic heating plate is adjustable, and the temperature can reach up to 800°C; the spray atomization module (Spray-Control) includes multiple replaceable (6) solid cone nozzles, and the (6) solid cone nozzles can be replaced through a standard threaded interface. The spray height is adjusted by a mechanical lifting device; the visual monitoring module (VIS-Optic) is equipped with (7) endoscope cameras and LED light sources for real-time monitoring of the spray process; the temperature acquisition and control module (Temp-Control) includes a multi-point (11) PT100 thermal resistor temperature acquisition module, (18) ESP32-S3 main control chip, fuzzy PID control algorithm, and a human-computer interactive touch screen; the spray chamber module (Spray-Chamber) is made of polytetrafluoroethylene material and polyurethane insulation filling, and is equipped with a pressure relief hole to form a closed and thermally insulated environment.

3. The liquid nitrogen spray cooling test system according to claim 1, characterized in that: The number of the nozzles is 1 to 4, and the nozzles are connected by a three-way splitter to ensure that the liquid nitrogen flow is evenly distributed among the nozzles.

4. The liquid nitrogen spray cooling test system according to claim 1, characterized in that: The (11) PT100 thermal resistor temperature acquisition module is arranged in three layers along the axial direction of the heat sink block, with two sensors on each layer, and the sensor surface is coated with low-temperature thermal conductive silicone grease to reduce thermal contact impedance.

5. The liquid nitrogen spray cooling test system according to claim 1, characterized in that: The (11) temperature acquisition module communicates with the (18) ESP32-S3 main control chip via a high-speed RS485 to TTL interface using the Modbus RTU protocol to achieve multi-channel data synchronous acquisition.

6. The liquid nitrogen spray cooling test system according to claim 1, characterized in that: The fuzzy PID control algorithm dynamically adjusts the PWM output power of the alumina ceramic heating plate (10) based on the temperature error and the error change rate to achieve temperature stability control.

Images