A transcranial magnetic coil liquid cooling device and control method for preventing condensation

Abstract

This invention discloses a transcranial magnetic coil liquid cooling device and control method for preventing condensation. The transcranial magnetic coil liquid cooling device includes a microcontroller unit (MCU), a thermoelectric cooler (TEC), and a coolant storage tank. The TEC has a heat exchange cold plate at its cold end and a cooling fan at its hot end. The outlet of the coolant storage tank is sequentially connected to the inlet of the heat exchange cold plate, the transcranial magnetic coil, and the coolant storage tank via coolant pipes. A gear pump and a flow sensor are mounted on the coolant pipes. The MCU is electrically connected to a host computer, the TEC, the gear pump, the flow sensor, the cooling fan, and multiple temperature sensors. These temperature sensors include a temperature sensor at the inlet of the heat exchange cold plate, a temperature sensor at the cold end of the TEC, a sensor at the outlet of the heat exchange cold plate, an ambient temperature sensor, and a temperature sensor for the transcranial magnetic coil. Using this invention, the temperature variation range of the coil can be reduced, while effectively preventing condensation.

Description

Technical Field

[0001] This invention belongs to the field of transcranial magnetic coil cooling technology, and in particular relates to a transcranial magnetic coil liquid cooling device and control method for preventing condensation. Background Technology

[0002] Transcranial magnetic stimulation (TMS) generates a strong magnetic field through a large current produced by short-circuiting a coil. Due to the coil's internal resistance, a significant amount of heat is generated during TMS, causing the coil to heat up. As the coil heats up, its internal resistance increases, further accelerating the temperature rise. Simultaneously, the excessively hot coil in contact with the patient can cause discomfort. Therefore, cooling the coil during TMS is essential. Currently, the main methods for cooling TMS coils include natural cooling, air cooling, and liquid cooling. Liquid cooling is gaining increasing importance due to its high cooling efficiency and low noise.

[0003] However, precisely controlling the temperature range and preventing condensation during liquid cooling has always been a challenge.

[0004] For example, Chinese patent document CN115623734A discloses an adaptive transcranial magnetic stimulation device cooling method, which adjusts the coil temperature by adjusting the pump speed. However, this method has a limited temperature adjustment range, that is, the power of the cold source is fixed and cannot be adjusted within a large dynamic range.

[0005] Chinese patent document CN112587800A discloses a semiconductor cooling device for a transcranial magnetic stimulation coil; however, this cooling device does not take into account the problem of preventing condensation during the cooling process. Summary of the Invention

[0006] This invention provides a transcranial magnetic coil liquid cooling device and control method for preventing condensation, which can reduce the temperature variation range of the coil and effectively prevent condensation from occurring.

[0007] A transcranial magnetic coil liquid cooling device for preventing condensation includes a microcontroller unit (MCU), a thermoelectric cooler (TEC), and a coolant storage tank; the cold end of the TEC is provided with a heat exchange cold plate, and the hot end of the TEC is provided with a cooling fan.

[0008] The outlet of the coolant storage tank is connected in sequence to the heat exchange cold plate, the transcranial magnetic coil and the inlet of the coolant storage tank via a coolant pipe. The coolant pipe is equipped with a gear pump and a flow sensor.

[0009] The microcontroller unit (MCU) is electrically connected to the host computer, TEC, gear pump, flow sensor, cooling fan, and multiple temperature sensors. Among them, the multiple temperature sensors include a temperature sensor at the inlet of the heat exchange cold plate, a temperature sensor at the cold end of the TEC, a sensor at the outlet of the heat exchange cold plate, an ambient temperature sensor, and a temperature sensor for the transcranial magnetic coil.

[0010] Furthermore, the coolant storage tank is equipped with a gas pressure sensor and a liquid level sensor that are electrically connected to the microcontroller unit (MCU).

[0011] Alternatively, the coolant in the coolant storage tank may be pure water, fluorinated liquid, silicone oil, aqueous solution of ethylene glycol, or aqueous solution of propylene glycol.

[0012] Preferably, the coolant in the coolant storage tank is an aqueous solution of ethylene glycol with a mass ratio of water to ethylene glycol of 1:1.

[0013] The above-mentioned method for preventing condensation in the transcranial magnetic coil liquid cooling device includes the following steps:

[0014] (1) Before the semiconductor cooler TEC starts operating, the transcranial magnetic coil works first. When the temperature rise of the temperature sensor at the inlet of the heat exchange cold plate... Record the time required when the temperature is between 0.5 and 3°C. ;

[0015] (2) Based on coolant parameters and temperature rise Calculate transcranial magnetic coil in Heat generated over time The average power of heat generated by the transcranial magnetic coil was further calculated. ;

[0016] (3) The MCU controls the operation of the semiconductor cooler TEC for cooling. During the cooling process, the average power of the heat generated by the transcranial magnetic coil is used. The theoretical cooling power of TEC Until the cooling capacity of the TEC and the heat generated by the cranial magnetic coil reach thermal equilibrium;

[0017] (4) After thermal equilibrium is reached, determine whether the cold end of the TEC is higher than the ambient temperature; if it is lower than the ambient temperature, then determine the theoretical cooling power of the TEC. The calculation formula is obtained by adjusting the drive current of the TEC. and TEC hot end temperature To control the cold end temperature of the TEC To reduce the cold end temperature It is always above the ambient temperature.

[0018] The calculation formula in step (2) is:

[0019] ;

[0020] ;

[0021] In the formula, For the density of the coolant, For the volume of coolant, This refers to the specific heat capacity of the coolant.

[0022] In step (3), the temperature change recorded by the temperature sensor at the liquid inlet of the heat exchange cold plate is used to determine whether the cooling capacity of the TEC and the heat generation of the cranial magnetic coil have reached thermal equilibrium.

[0023] The theoretical cooling power of the transcranial magnetic coil during each operation is [not specified]. The following formula must be satisfied:

[0024] ;

[0025] In the formula, The heat power carried away by the coolant. This represents the heat exchange power between the heat exchange cold plate and the coolant.

[0026] The heat power carried away by the coolant Calculated using the following formula:

[0027] ;

[0028] In the formula, It refers to the density of the coolant. It is the coolant flow rate. It is the cross-sectional area of ​​the coolant pipe. It is the specific heat capacity of the coolant. It is the temperature at the outlet of the heat exchange cold plate. It is the temperature at the liquid inlet of the heat exchange cold plate;

[0029] Heat exchange power between heat exchange cold plate and coolant Calculated using the following formula:

[0030] ;

[0031] In the formula, It is the convective heat transfer coefficient. It refers to the heat exchange area of ​​the heat exchange cold plate. It is the cold end temperature of the TEC; It is the average temperature of the fluid, the temperature at the outlet of the heat exchanger cold plate. Temperature of the inlet The average value is obtained.

[0032] In step (4), the theoretical cooling power of TEC The calculation formula is as follows:

[0033] ;

[0034] in, The Seebeck coefficient is... For the resistor of TEC, Total thermal conductivity; maintaining the theoretical cooling power of the TEC The current remains unchanged; the driving current of the TEC is adjusted accordingly. and TEC hot end temperature To control the cold end temperature of the TEC TEC hot end temperature The speed of the cooling fan is adjusted by controlling it through an MCU.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. In this invention, the average power of heat generated by the transcranial magnetic coil is first calculated during each transcranial magnetic stimulation. and the average power of heat generated by the transcranial magnetic coil The theoretical cooling power of TEC Cooling is performed to quickly reach thermal equilibrium.

[0037] 2. The target (coil) of this invention has a small dynamic range of temperature control, which helps to avoid discomfort caused to patients by large temperature fluctuations during treatment.

[0038] 3. This invention has an anti-condensation function, that is, by adjusting the driving current of the TEC. and TEC hot end temperature To control the cold end temperature of the TEC This ensures that the TEC cold end temperature is always higher than the ambient temperature, preventing condensation from occurring. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a schematic diagram of the MCU connection in a transcranial magnetic coil liquid cooling device for preventing condensation, according to an embodiment of the present invention.

[0041] Figure 2 This is a flowchart illustrating an anti-condensation control method for a transcranial magnetic coil liquid cooling device according to an embodiment of the present invention.

[0042] Figure 3 The figures show the temperature change curves of the TEC inlet, cold end, and ambient temperature in this embodiment of the invention. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] It should be noted that, unless otherwise specified, the features in the following embodiments and implementation methods can be combined with each other.

[0045] A transcranial magnetic coil liquid cooling device with anti-condensation features includes a microcontroller unit (MCU), a thermoelectric cooler (TEC), and a coolant storage tank. The cold end of the TEC is equipped with a heat exchange cold plate, and the hot end of the TEC is equipped with a cooling fan. The outlet of the coolant storage tank is sequentially connected to the heat exchange cold plate, the transcranial magnetic coil, and the inlet of the coolant storage tank via coolant pipes.

[0046] In this embodiment of the invention, the MCU is an STM32F103 with a Cortex-M3 core. This MCU serves as the main controller of the system and is responsible for pin level control, data acquisition, data processing, interface communication, and protocol parsing.

[0047] The microcontroller unit (MCU) is electrically connected to the host computer, TEC, gear pump, cooling fan, and multiple sensors.

[0048] like Figure 1 As shown, the pressure sensor is used to measure the gas pressure inside the coolant storage tank and provides alarm information when the pressure abnormally increases or decreases. In this embodiment, the coolant in the coolant storage tank is an ethylene glycol aqueous solution with a water-ethylene glycol mass ratio of 1:1.

[0049] A liquid level sensor is used to detect the liquid level of the coolant in the coolant reservoir in real time and to trigger an alarm when the liquid level drops to the warning line.

[0050] There are five temperature sensors: a temperature sensor at the inlet of the heat exchanger cold plate, a temperature sensor at the TEC cold end, a sensor at the outlet of the heat exchanger cold plate, an ambient temperature sensor, and a transcranial magnetic coil temperature sensor. The temperature sensors used here are PT100 thermistors, but PT1000 or NTC thermistors can also be used.

[0051] The flow sensor is installed on the coolant pipe, and the flow measurement range is 0~2L / min.

[0052] The CAN interface is used for communication between the MCU and the host computer.

[0053] The pump interface is used to connect the MCU to the gear pump, which provides power for the circulation of coolant. The pump flow rate is adjustable, ranging from 0 to 1.5 L / min, ensuring that it does not exceed the flow meter's range.

[0054] The fan interface is used to connect the MCU to the cooling fan. The cooling fan has a speed control function. When the TEC power supply voltage increases, the fan speed also increases. The speed control here is achieved through PWM.

[0055] The TEC driver interface is used to connect the MCU to the TEC. The TEC driver model is 12706, and its driver circuit uses an adjustable power supply with an adjustable power supply range of 0~12V. Optionally, this driver can also be used for duty cycle modulation via PWM.

[0056] like Figure 2 As shown, a method for preventing condensation in a transcranial magnetic coil liquid cooling device includes the following steps:

[0057] The purpose of the power-on self-test is to check whether each module of the liquid cooling system is normal. The modules checked include the TEC, gear pump, flow sensor, liquid level sensor, temperature sensor, pressure sensor, and fan.

[0058] The TEC can operate for cooling when all self-tests are normal. If any self-test fails, the fault must be resolved before cooling can begin. Faults include TEC cooling module malfunction, gear pump flow rate malfunction, temperature malfunction, liquid level malfunction, pressure malfunction, and fan malfunction.

[0059] Before TEC operation, the transcranial magnetic coil is activated first, and the temperature rise of the temperature sensor at the inlet of the heat exchange cold plate is monitored. Record the time required at 2℃. At this point, based on the coolant parameters and temperature rise... Calculate transcranial magnetic coil in Heat generated over time The formula is as follows:

[0060] ;

[0061] In the formula, For the density of the coolant, For the volume of coolant, This refers to the specific heat capacity of the coolant.

[0062] Further based on the heating time of the transcranial magnetic coil The average power of heat generated by the transcranial magnetic coil was calculated. :

[0063] ;

[0064] To prevent the coolant temperature from rising, the cooling power must be greater than or equal to the heat generation power. Here, a critical condition is considered. The MCU controls the semiconductor cooler (TEC) to operate, and the average power of the heat generated by the transcranial magnetic coil during the cooling process is... The theoretical cooling power of TEC This allows the cooling capacity of the TEC to reach thermal equilibrium with the heat generated by the transcranial magnetic coil.

[0065] When determining whether the temperature at the liquid inlet is balanced, due to the existence of a certain measurement error, the PT100 Class A temperature sensor used in this embodiment has an accuracy of ±0.1℃. Therefore, when the temperature is detected to be oscillating around a certain value, it is considered that thermal equilibrium has been reached.

[0066] To accelerate the achievement of thermal equilibrium, the cooling capacity can be appropriately increased, the flow rate can be increased, and the temperature difference between the inlet and outlet can be reduced to make the temperature inside the pipe as uniform as possible.

[0067] The control objective of this invention is to keep the temperature at both ends of the coil constant, that is, to achieve a balance between the heat generation of the coil and the cooling of the TEC, while controlling the cold end temperature of the TEC to prevent condensation. The theoretical formula for the cooling power of the TEC is as follows:

[0068] ;

[0069] in, The Seebeck coefficient is... For the drive current of the TEC, Where K is the resistance of the TEC, and K is the total thermal conductivity. This refers to the hot end temperature of the TEC. This refers to the cold end temperature of the TEC.

[0070] Summarized as follows:

[0071] ;

[0072] Since the heat source (treatment coil) is fixed, the cooling power is also fixed. Therefore, the theoretical cooling power of the transcranial magnetic coil (TEC) is [not specified] during each operation. It is a constant, and at the same time, It is a constant. If the temperature remains constant within a certain range, then only the drive current of the TEC needs to be adjusted. and TEC hot end temperature This allows control of the cold junction temperature of the TEC. TEC hot end temperature The speed of the cooling fan is adjusted by controlling it through an MCU.

[0073] By adjusting the drive current of the TEC and TEC hot end temperature To control the cold end temperature of the TEC To reduce the cold end temperature Maintaining a temperature consistently higher than the ambient temperature can effectively prevent condensation.

[0074] If the cold end temperature of the TEC When the temperature is below ambient temperature, increase the fan speed at the hot end of the TEC to reduce the temperature difference between the hot and cold ends of the TEC. At the same time, reduce the voltage across the TEC and increase the coolant flow rate. This can increase the cold end temperature of the TEC without reducing the cooling power, thereby achieving the purpose of regulating the cold end temperature of the TEC.

[0075] In this embodiment of the invention, the hot end of the TEC is cooled by a cooling fan. In practical applications, coolant can also be used for cooling.

[0076] During each operation of the transcranial magnetic coil, when the cooling capacity of the TEC (Transcranial Magnetic Coil) is balanced with the heating capacity of the coil, it is necessary to consider that the cooling capacity of the TEC can be carried away by the coolant, and that the cold end of the TEC can be transferred to the coolant through heat exchange. That is, the following formula needs to be satisfied:

[0077] ;

[0078] In the formula, The heat power carried away by the coolant. This represents the heat exchange power between the heat exchange cold plate and the coolant.

[0079] The heat power carried away by the coolant Calculated using the following formula:

[0080] ;

[0081] In the formula, It refers to the density of the coolant. It is the coolant flow rate. It is the cross-sectional area of ​​the coolant pipe. It is the specific heat capacity of the coolant. It is the temperature at the outlet of the heat exchange cold plate. It is the temperature of the liquid inlet of the heat exchange cold plate.

[0082] Heat exchange power between heat exchange cold plate and coolant Calculated using the following formula:

[0083] ;

[0084] In the formula, It is the convective heat transfer coefficient. It refers to the heat exchange area of ​​the heat exchange cold plate. It is the cold end temperature of the TEC; It is the average temperature of the fluid, the temperature at the outlet of the heat exchanger cold plate. Temperature of the inlet The average value is obtained as follows:

[0085] ;

[0086] at the same time, As the convective heat transfer coefficient, it is divided into laminar and turbulent flow. The laminar flow coefficient can be calculated using the following formula:

[0087] ;

[0088] in, It is the Nusselt number (generally a constant for laminar flow, but 3.66 when the Reynolds number is less than 2300). It is the thermal conductivity of the fluid. It is the characteristic length of the pipe.

[0089] In turbulent flow, the Nusselt number is calculated using the following formula:

[0090] ;

[0091] Among them, when cooling fluid Take 0.3, It is the Reynolds number. This is the Prandtl number. The formula for calculating the Reynolds number is as follows:

[0092] ;

[0093] in, It refers to the density of the coolant. It is the coolant flow rate. It is the feature length.

[0094] The formula for calculating Prandtl's number is as follows:

[0095] ;

[0096] in, It is dynamic viscosity. It is the specific heat capacity of the coolant. It is the thermal conductivity.

[0097] like Figure 3The figure shows a temperature change curve during the implementation of this invention. The blue line segment represents the inlet temperature, sampled at minutes 0, 5, 10, 15, and 20, which corresponds to one treatment cycle of transcranial magnetic stimulation (TMS), approximately 20 minutes. The red line segment represents the cold end temperature, sampled at the same time as the blue line segment; the yellow line segment represents the ambient temperature, also sampled at the same time as the blue line segment. As can be seen from the figure, the cold end temperature remains above the ambient temperature, thus achieving the purpose of preventing condensation. Simultaneously, the inlet temperature fluctuates little and shows a trend of first decreasing and then stabilizing, achieving the purpose of cooling the coil during the treatment process of this invention, while minimizing temperature fluctuations to ensure patient comfort during treatment.

[0098] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preventing condensation in a transcranial magnetic coil liquid cooling device, characterized in that, The transcranial magnetic coil liquid cooling device includes a microcontroller unit (MCU), a thermoelectric cooler (TEC), and a coolant storage tank; the cold end of the TEC is equipped with a heat exchange cold plate, and the hot end of the TEC is equipped with a cooling fan. The outlet of the coolant storage tank is connected in sequence to the heat exchange cold plate, the transcranial magnetic coil and the inlet of the coolant storage tank via a coolant pipe. The coolant pipe is equipped with a gear pump and a flow sensor. The microcontroller unit (MCU) is electrically connected to the host computer, TEC, gear pump, flow sensor, cooling fan, and multiple temperature sensors. The multiple temperature sensors include a temperature sensor at the inlet of the heat exchange cold plate, a temperature sensor at the cold end of the TEC, a sensor at the outlet of the heat exchange cold plate, an ambient temperature sensor, and a transcranial magnetic coil temperature sensor. The aforementioned anti-condensation control method includes the following steps: (1) Before the semiconductor cooler TEC starts operating, the transcranial magnetic coil works first. When the temperature rise of the temperature sensor at the inlet of the heat exchange cold plate... Record the time required when the temperature is between 0.5 and 3°C. ; (2) Based on coolant parameters and temperature rise Calculate transcranial magnetic coil in Heat generated over time The average power of heat generated by the transcranial magnetic coil was further calculated. ; (3) The MCU controls the operation of the semiconductor cooler TEC for cooling. During the cooling process, the average power of the heat generated by the transcranial magnetic coil is used. The theoretical cooling power of TEC Until the cooling capacity of the TEC and the heat generated by the cranial magnetic coil reach thermal equilibrium; (4) After thermal equilibrium is reached, determine whether the cold end of the TEC is higher than the ambient temperature; if it is lower than the ambient temperature, then determine the theoretical cooling power of the TEC. The calculation formula is obtained by adjusting the drive current of the TEC. and TEC hot end temperature To control the cold end temperature of the TEC To reduce the cold end temperature It is always above the ambient temperature.

2. The anti-condensation control method for the transcranial magnetic coil liquid cooling device according to claim 1, characterized in that, The coolant storage tank is equipped with a gas pressure sensor and a liquid level sensor that are electrically connected to the microcontroller unit (MCU).

3. The anti-condensation control method for the transcranial magnetic coil liquid cooling device according to claim 1, characterized in that, The coolant in the coolant storage tank is pure water, fluorinated liquid, silicone oil, ethylene glycol aqueous solution, or propylene glycol aqueous solution.

4. The anti-condensation control method for the transcranial magnetic coil liquid cooling device according to claim 1, characterized in that, The coolant in the coolant storage tank is an aqueous solution of ethylene glycol with a mass ratio of water to ethylene glycol of 1:

1.

5. The anti-condensation control method for the transcranial magnetic coil liquid cooling device according to claim 1, characterized in that, The calculation formula in step (2) is: ； ； In the formula, For the density of the coolant, For the volume of coolant, This refers to the specific heat capacity of the coolant.

6. The anti-condensation control method for the transcranial magnetic coil liquid cooling device according to claim 1, characterized in that, In step (3), the temperature change recorded by the temperature sensor at the liquid inlet of the heat exchange cold plate is used to determine whether the cooling capacity of the TEC and the heat generation of the cranial magnetic coil have reached thermal equilibrium.

7. The anti-condensation control method for the transcranial magnetic coil liquid cooling device according to claim 1, characterized in that, The theoretical cooling power of the transcranial magnetic coil during each operation is [not specified]. The following formula must be satisfied: ； In the formula, The heat power carried away by the coolant. This represents the heat exchange power between the heat exchange cold plate and the coolant.

8. The anti-condensation control method for the transcranial magnetic coil liquid cooling device according to claim 7, characterized in that, The heat power carried away by the coolant Calculated using the following formula: ； In the formula, It refers to the density of the coolant. It is the coolant flow rate. It is the cross-sectional area of ​​the coolant pipe. It is the specific heat capacity of the coolant. It is the temperature at the outlet of the heat exchange cold plate. It is the temperature at the liquid inlet of the heat exchange cold plate; Heat exchange power between heat exchange cold plate and coolant Calculated using the following formula: ； In the formula, It is the convective heat transfer coefficient. It refers to the heat exchange area of ​​the heat exchange cold plate. It is the cold end temperature of the TEC; It is the average temperature of the fluid, the temperature at the outlet of the heat exchanger cold plate. Temperature of the inlet The average value is obtained.

9. The anti-condensation control method for the transcranial magnetic coil liquid cooling device according to claim 1, characterized in that, In step (4), the theoretical cooling power of TEC The calculation formula is as follows: ； in, The Seebeck coefficient is... For the resistor of TEC, Total thermal conductivity; maintaining the theoretical cooling power of the TEC The current remains unchanged; the driving current of the TEC is adjusted accordingly. and TEC hot end temperature To control the cold end temperature of the TEC TEC hot end temperature The speed of the cooling fan is adjusted by controlling it through an MCU.

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