An artificial frost refrigeration device and a method of using the same

Abstract

The application discloses an artificial frosting refrigeration device and a use method thereof, and belongs to the technical field of vegetable cultivation. The device comprises a power module, an AC-DC converter, a DC-DC converter, a PWM amplification circuit, a high-power single-phase full-bridge inverter circuit, an ultrasonic atomization module, a heat tracing band, a water treatment module, a local cooling module and a sensing and control module. The ultrasonic atomization module atomizes and sprays water mist to the vegetable leaf surface, and the local cooling module locally cools the leaf surface to form a frost layer; the heat tracing band prevents the water body from freezing; the water treatment module sterilizes and disinfects the water source; the sensing and control module comprises an automatic frequency tracking unit and a cold exposure cumulative amount calculation protection unit. The use method comprises initialization, water treatment, temperature and humidity monitoring, leaf surface cooling, frequency tracking, atomization spraying, frost layer control and ending steps. The application enables the vegetables to obtain the taste and flavor of "post-frost vegetables" in a non-winter environment.

Description

Technical Field

[0001] This invention relates to the field of vegetable cultivation and frost technology, specifically to an artificial frost-forming refrigeration device and its usage method. Background Technology

[0002] In winter or cold regions, many vegetables naturally develop a frost-like layer on their leaves, commonly known as "frost-covered vegetables," which have superior taste, flavor, and nutritional value compared to ordinary vegetables. This is because low temperatures and frost trigger the vegetables' self-protective mechanisms: the starch stored in the leaves is hydrolyzed into soluble sugars by enzymes, significantly enhancing the sweet taste and lowering the cell freezing point to resist frost damage; simultaneously, some bitter substances are broken down, umami amino acids accumulate, and the flavor becomes richer; furthermore, the low temperature slows down the metabolic rate, allowing for more complete accumulation of dry matter, further enhancing the nutritional concentration and flavor profile. However, outside of winter, due to higher ambient temperatures, it is difficult for frost to form on vegetable leaves, preventing consumers from enjoying "frost-covered vegetables" year-round.

[0003] In existing technologies, some refrigeration or low-temperature control devices can lower the ambient temperature, but they also have some problems. For example, it is difficult to create suitable temperature and humidity conditions for frost formation on local leaf surfaces, and it is impossible to atomize water evenly and cover vegetable leaves to form a uniform frost layer. Furthermore, they do not fully consider water source sterilization and anti-icing measures, and there are risks of discontinuous atomized water supply or hygiene risks. Summary of the Invention

[0004] The purpose of this invention is to provide a refrigeration device, comprising: a power module, which uses DC power input, converts it to high-frequency AC power through a full-bridge inverter circuit, steps up the voltage through a step-up transformer, and outputs high-voltage DC power through a voltage doubler rectifier circuit; an energy storage capacitor module, connected in parallel with the output terminal of the power module, for storing electrical energy; an electrode module, including fixed electrodes and movable electrodes, wherein the voltage between the electrodes is supplied by the energy storage capacitor; an electromagnetic drive module, including an electromagnetic coil, an iron core, and a spring structure, for driving the movable electrodes to move to adjust the electrode spacing; and a microcontroller control module, for sampling the capacitor voltage in real time and controlling the charging rate by adjusting the PWM duty cycle to stabilize the capacitor voltage within a set range.

[0005] Furthermore, the voltage multiplier rectifier circuit is a six-stage voltage multiplier circuit, which achieves voltage multiplication through a series and parallel combination of multiple diodes and capacitors.

[0006] Furthermore, the energy storage capacitor module includes a metallized polypropylene film capacitor with a capacitance of 100nF to 500nF and a rated voltage of 35kV.

[0007] Furthermore, a protective resistor is connected in series between the power module and the energy storage capacitor module to limit the charging current.

[0008] Furthermore, the microcontroller control module adopts an STM32F103C8T6 microcontroller, which has PWM output, ADC sampling and serial communication functions, and can adjust the PWM duty cycle in real time according to the capacitor voltage.

[0009] Furthermore, the electrode spacing of the electromagnetic drive module can be adjusted from 0.1 mm to 5 mm.

[0010] Furthermore, the electromagnetic drive module generates a magnetic field through an electromagnetic coil and an iron core. When the coil is energized, the movable electrode moves axially; when the coil is de-energized, the movable electrode returns to its initial position under the action of the spring restoring force.

[0011] Furthermore, it also includes a temperature protection module that automatically adjusts the power input or shuts off the power when the system temperature exceeds a set threshold.

[0012] Furthermore, a method of using a refrigeration device is characterized by comprising the following steps:

[0013] Step S100: The system is powered on and initialized. The microcontroller control module reads the preset parameters and sets the target voltage and current protection thresholds.

[0014] Step S200: The power module converts DC power into high-frequency AC power through a full-bridge inverter circuit, and after being stepped up by a step-up transformer, it outputs high-voltage DC power through a voltage doubler rectifier circuit;

[0015] Step S300: The energy storage capacitor module starts charging. The microcontroller control module samples the capacitor voltage in real time and controls the charging rate by adjusting the PWM duty cycle.

[0016] Step S400: When the capacitor voltage approaches the target value, the microcontroller control module gradually reduces the PWM duty cycle and enters trickle charging mode to stabilize the capacitor voltage within the set range.

[0017] Step S500: The electromagnetic drive module adjusts the electrode spacing according to the instruction. By controlling the current intensity of the electromagnetic coil, it pushes the movable electrode to move, thereby achieving precise adjustment of the electrode spacing.

[0018] Step S600: When the electrode spacing reaches the set value, the system enters the discharge mode, and the energy storage capacitor provides a stable voltage to the electrodes;

[0019] Step S700: Repeat steps S300 to S600 until a stop command is received.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) The present invention uses an ultrasonic atomizing device to atomize disinfected water and spray it onto the vegetable leaves. At the same time, a local cooling module is used to regulate the low temperature of the leaves, so that a uniform frost layer is formed on the vegetable leaves, allowing the vegetables to obtain the taste and flavor of winter "frost vegetables" in non-winter environments.

[0022] (2) The present invention maintains the water source temperature by using a heat tracing cable to prevent the water from freezing and ensure the continuity of atomized water supply; and sterilizes and disinfects the water source by using a water treatment module to ensure the safety of the atomized water source and the hygiene of the system operation.

[0023] (3) The present invention dynamically locks the resonant frequency of the ultrasonic transducer through an automatic frequency tracking unit, and adopts a phase-locked loop and PI controller closed-loop tracking method to compensate for frequency drift caused by water temperature, load and aging in real time, so as to ensure maximum atomization efficiency; and uses a cold exposure accumulation calculation and protection unit to evaluate and prevent vegetables from suffering irreversible frost damage in real time.

[0024] The present invention will now be further described with reference to the accompanying drawings. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the artificial frost refrigeration device according to an embodiment of the present invention.

[0026] Figure 2 This is a schematic diagram of the working process of the artificial frost refrigeration device according to an embodiment of the present invention.

[0027] Figure 3 This is a high-power single-phase full-bridge inverter circuit diagram for an artificial frost refrigeration device according to an embodiment of the present invention.

[0028] Figure 4 The diagram shows the equivalent circuit of the piezoelectric vibrator of the ultrasonic transducer in the artificial frost refrigeration device according to an embodiment of the present invention.

[0029] Figure 5 This is a block diagram of the frequency tracking PI control of the ultrasonic transducer in the artificial frost refrigeration device according to an embodiment of the present invention.

[0030] Figure 6 This is a schematic diagram of the AC-DC converter of the artificial frost refrigeration device according to an embodiment of the present invention.

[0031] Figure 7 This is a schematic diagram of the PWM amplifier circuit of the artificial frost refrigeration device according to an embodiment of the present invention.

[0032] Figure 8 This is a flowchart illustrating the cold exposure monitoring process of the artificial frost refrigeration device according to an embodiment of the present invention.

[0033] Figure 9This is a schematic diagram of the minimum system circuit of the STM32 microcontroller for the artificial frost refrigeration device according to an embodiment of the present invention. Detailed Implementation

[0034] Reference Figure 1 The artificial frost refrigeration device in this embodiment mainly includes a power supply module, an AC-DC converter, a DC-DC converter, a PWM amplifier circuit, a high-power single-phase full-bridge inverter circuit, an ultrasonic atomization module, a heating tape, a water treatment module, a local cooling module, and a sensing and control module.

[0035] Reference Figure 6 An AC-DC converter is used to convert AC power from the mains to DC power. A DC-DC converter connects to a power supply module for input-output voltage conversion, outputting an adjustable voltage from 12V to 60V to power microcontrollers, PWM amplifier circuits, single-phase full-bridge inverter circuits, water treatment modules, local cooling modules, and sensing and control modules.

[0036] Reference Figure 7 The PWM amplifier circuit is used to amplify the PWM waveform and provide sufficient drive voltage and instantaneous charge and discharge current for the MOSFET gate of the single-phase full-bridge inverter circuit, ensuring its fast and reliable turn-on and turn-off.

[0037] Reference Figure 3 A high-power single-phase full-bridge inverter circuit is connected to a PWM amplifier circuit to generate bipolar pulses. This circuit includes four MOSFETs arranged in an H-shape to form a bridge inverter circuit. The amplified PWM waveform is applied to the gates of the MOSFETs, driving the full-bridge MOSFETs in a diagonally complementary manner of "Q1+Q4" and "Q2+Q3" to generate bipolar pulses with adjustable amplitude, frequency, and duty cycle. These pulses are then output to the ultrasonic transducer, driving the piezoelectric ceramic wafer to produce mechanical vibration.

[0038] The bipolar pulse operates within a frequency range of 1.0MHz to 3.0MHz, with an adjustable duty cycle between 5% and 50% and an amplitude range of 20V to 60V. The pulse frequency is dynamically controlled by an automatic frequency tracking unit, while the duty cycle and amplitude are adjusted via a microcontroller.

[0039] The ultrasonic atomization module includes a transducer and a drive source, used to atomize water and spray it onto the surface of vegetables. (See reference) Figure 4 The ultrasonic transducer is a piezoelectric ultrasonic transducer, and its electrostatic characteristics are represented by a parallel static capacitance Cs; its mechanical resonance behavior is represented by a series dynamic branch Lm, Cm, and Rd, where Lm is the magnetizing inductance, Cm is the dynamic capacitance, and Rd is the equivalent dynamic resistance, and the dynamic branch is connected in parallel with the static capacitance. The resonant frequency fs of the dynamic branch satisfies formula (1):

[0040] ;

[0041] The parallel resonant frequency fp satisfies formula (2):

[0042] ;

[0043] The transducer operates in the frequency range of 1.0MHz to 3.0MHz and has a rated power of 50W to 200W.

[0044] Reference Figure 5 The automatic frequency tracking unit is built on the phase-locked loop principle to dynamically maintain the operating frequency of the ultrasonic transducer at its mechanical resonant point. This unit acquires the transducer's drive current and voltage signals in real time through current and voltage sampling circuits. The phase difference between the two signals is calculated by the phase detection module and output as an error signal. This error signal is input to a PI controller for adjustment, and the control voltage is input to a voltage-controlled oscillator (VCO). The VCO outputs a signal with a proportionally varying frequency to a PWM generator, dynamically adjusting the drive frequency of the single-phase full-bridge inverter circuit.

[0045] The heating cable is installed on the outer wall of the water bottle to heat the water and prevent it from freezing. The heating cable is equipped with a digital thermostat; it starts heating when the detected water temperature is below +3°C and stops heating when the water temperature rises to +8°C.

[0046] The water treatment module is used to sterilize and disinfect the water supplied to the ultrasonic atomizer and provides real-time monitoring and protection. This module includes a two-stage series-connected replaceable filter unit, an ultraviolet disinfection unit, and a circulation protection system. The ultraviolet disinfection unit uses a UV-C band disinfection device with a wavelength of 253.7nm and a designed ultraviolet dose of no less than 30mJ / cm². The circulation protection system includes a water supply pump and a water level detection device. The high water level shutdown threshold is set at 90% of the container's rated height, and the low water level shutdown and alarm threshold is set at 10% of the container's rated height.

[0047] The localized cooling module includes a Peltier refrigeration unit, which is used to locally cool the vegetable leaves to form a frost layer.

[0048] The sensing and control module includes an environmental sensor, an automatic frequency tracking unit, and a cold exposure accumulation calculation and protection unit. (Refer to...) Figure 9 The control module uses an STM32 microcontroller. Environmental sensors are used to monitor the ambient temperature and humidity inside the refrigeration unit, as well as the temperature of the vegetable leaves.

[0049] Reference Figure 8The Cold Exposure Dose Calculation and Protection Unit is used to assess and prevent irreversible frost damage to vegetables in real time during the frost process. The Cold Exposure Dose (CED) is defined as the integral of the absolute value of the difference between the leaf temperature T_leaf and the plant's specific critical temperature T_critical over time, expressed in °C·s. CED is calculated using the following discretization formula (3):

[0050] CED=∑[max(T_critical - T_leaf(t), 0)·Δt];

[0051] Where T_critical is the specific critical temperature for the plant, in °C; T_leaf(t) is the leaf surface temperature at time t, in °C; Δt is the sampling time interval, in seconds; the max function is used to take the maximum value between the value in parentheses and 0, ensuring that the cold exposure is accumulated only when the leaf surface temperature is below the critical temperature. When the CED value reaches or exceeds the preset safe dose threshold D_max, the module immediately triggers protection strategies, including reducing the cooling intensity, pausing nebulization, reheating, or alarming.

[0052] Reference Figure 2 The present invention also proposes a method for using an artificial frost-forming refrigeration device, comprising the following steps:

[0053] Step S100: The system is powered on and initialized. The sensing and control module completes self-test and loads the preset frosting parameters.

[0054] Step S200: Start the water treatment module to sterilize and disinfect the stored water, and at the same time turn on the heating cable to keep the water bottle warm and prevent it from freezing.

[0055] Step S300: The sensing and control module continuously monitors the water level and the temperature of the tracing cable. If either is abnormal, the process is paused and an alarm is issued, awaiting manual intervention; if the status is normal, proceed to the next step.

[0056] Step S400: The sensing and control module continuously collects ambient temperature and humidity and vegetable leaf temperature. Ambient temperature and humidity are collected in a cycle of 1 to 5 seconds, and leaf temperature is collected in a cycle of 10 to 200 ms. The real-time dew point is calculated, and the local cooling module is gradually reduced to the target range of -1℃ to -3℃ through leaf PID closed-loop regulation.

[0057] Step S500: The automatic frequency tracking unit dynamically locks the resonant frequency of the ultrasonic transducer. An AD8302 chip is used as the phase measurement module to calculate the voltage-current phase difference, with an update frequency of 200Hz. The phase difference is used as feedback input to the PI controller within the phase-locked loop (PLL) closed loop, with a sampling period of 1ms. Frequency adjustment is implemented in two stages: the coarse scan stage involves a step scan of 0.1% within ±3% of the nominal resonant frequency, with a total coarse scan duration of 0.5s; the fine locking stage involves rapid fine-tuning of the frequency error by the PLL and PI controller, with a loop convergence time ranging from 50ms to 500ms, and a total convergence time not exceeding 2.5s.

[0058] Step S600: When the blade surface temperature reaches the target and the frequency is locked, the sensing and control module issues a start command, and the ultrasonic atomization module operates according to the pulse strategy. The atomization pulse strategy is as follows: pulse envelope opening duration 100ms to 500ms, envelope interval 2s to 10s, single pulse duty cycle 5% to 50%, and drive amplitude 20Vpp to 60Vpp. The transducer breaks the water into micron-sized cold mist, which is then sprayed onto the low-temperature blade surface.

[0059] Step S700: After the water mist comes into contact with the low-temperature leaf surface, it condenses and forms a frost layer. The sensing and control module monitors the growth status of the frost layer in real time, dynamically adjusts the spray volume of the ultrasonic atomization and the power of the local cooling module, and precisely controls the frost formation rate and effect.

[0060] Step S800: When the frost layer reaches the preset target, the ultrasonic atomization module and the local cooling module are stopped sequentially to end the frosting process.

[0061] The system also features multiple safety protection mechanisms: during atomization operation, phase monitoring and overcurrent detection are continuously performed. When a loss of lock, overcurrent, or phase abnormality is detected, the control module immediately reduces the drive amplitude according to preset steps. If the fault persists, atomization is immediately stopped and the fault protection process is initiated. When the cumulative amount of cold exposure exceeds the safety limit, protective actions such as reducing the cooling intensity, pausing atomization, reheating, or alarming are automatically taken.

Claims

1. An artificial frost-forming refrigeration device, characterized in that, include: A power module is used to supply power to the device; AC-DC converters are used to convert AC power from the power grid into DC power. A DC-DC converter, connected to the power supply module, is used for input-output voltage conversion; A PWM amplifier circuit is used to amplify PWM signals. A high-power single-phase full-bridge inverter circuit is used to generate bipolar pulses; An ultrasonic atomizing module, including a transducer and a drive source, is used to atomize water and spray it onto the surface of vegetables. A heating tape, placed on the outer wall of a water bottle, is used to heat the water bottle; The water treatment module is used to sterilize and disinfect water, as well as to detect water level and temperature of the heating cable; The localized cooling module, including the Peltier refrigeration unit, is used to locally cool the vegetable leaves to form a frost layer; The sensing and control module includes an environmental sensor, an automatic frequency tracking unit, and a cold exposure accumulation calculation and protection unit, which are used to monitor environmental parameters and control the ultrasonic atomization module and the local cooling module.

2. The refrigeration device according to claim 1, characterized in that, The high-power single-phase full-bridge inverter circuit consists of an H-bridge structure composed of four MOSFETs, used to generate bipolar pulses with a frequency range of 1.0MHz to 3.0MHz, a duty cycle range of 5% to 50%, and an amplitude range of 20V to 60V.

3. The refrigeration device according to claim 1, characterized in that, The automatic frequency tracking unit is built on the principle of phase-locked loop. It collects the drive current and voltage signals of the transducer, calculates the phase difference, and adjusts the drive frequency to make the transducer work at the mechanical resonance point.

4. The refrigeration device according to claim 1, characterized in that, The water treatment module includes a filtration unit, an ultraviolet disinfection unit, and a circulation protection system. The ultraviolet disinfection unit uses a UV-C band disinfection device with a wavelength of 253.7nm.

5. The refrigeration device according to claim 1, characterized in that, The heating cable is equipped with a digital thermostat, which starts heating when the water temperature is below +3°C and stops heating when the water temperature rises to +8°C.

6. The refrigeration apparatus according to claim 1, characterized in that, The cold exposure accumulation calculation and protection unit uses the formula... CED=∑[max(T_critical - T_leaf(t), 0)·Δt]; Wherein, CED is the cumulative cold exposure amount, in °C·s; T_critical is the specific critical temperature of the plant, in °C; T_leaf(t) is the leaf surface temperature at time t, in °C; Δt is the sampling time interval, in s; when the CED value reaches the preset threshold, the protection strategy is triggered.

7. The refrigeration apparatus according to claim 1, characterized in that, The sensing and control module uses an STM32 microcontroller to control the cooling power of the local cooling module and the start / stop of the ultrasonic atomization module based on ambient temperature and humidity, leaf surface temperature, and frost parameters.

8. A method of using the artificial frost-forming refrigeration device as described in any one of claims 1 to 7, characterized in that, Includes the following steps: Step S100: The system is powered on and initialized. The sensing and control module completes self-test and loads the preset frosting parameters. Step S200: Start the water treatment module to sterilize and disinfect the stored water, and at the same time turn on the heating cable to keep the water bottle warm; Step S300: The sensing and control module continuously monitors the water level and the temperature of the tracing cable. If any abnormality is detected, the process is paused and an alarm is issued. Step S400: The sensing and control module collects ambient temperature and humidity and vegetable leaf surface temperature, and uses PID closed-loop regulation to adjust the local cooling module to reduce the leaf surface temperature to the target range; Step S500: The automatic frequency tracking unit dynamically locks the resonant frequency of the ultrasonic transducer; Step S600: When the leaf surface temperature reaches the target and the frequency is locked, the ultrasonic atomization module operates according to the pulse strategy, atomizing the water and spraying it onto the low-temperature leaf surface; Step S700: After the water mist comes into contact with the low-temperature blade surface, it condenses to form a frost layer. The sensing and control module dynamically adjusts the atomization amount and cooling power. Step S800: When the frost layer reaches the preset target, the ultrasonic atomization module and the local cooling module are stopped sequentially.

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