Cryosleep litchi unfreezing system and method based on ultrasonic wave and water bath unfreezing

Abstract

The invention provides a frozen sleep litchi thawing system and thawing method based on ultrasonic synergistic water bath thawing. The thawing system comprises: a water bath tank; an ultrasonic generating assembly and a temperature sensor; a heating assembly; a control module and a protection assembly; a protection assembly; a stirring assembly; according to the thawing method, the thawing system is adopted, the real-time temperature of the litchis is obtained through the thawing state estimation method, the real-time temperature of the litchis is compared with the ideal temperature, and the ultrasonic output power and the heating power are adjusted according to the comparison result so that the thawing efficiency can be guaranteed as much as possible, and meanwhile the flavor of the litchis can be guaranteed as much as possible.

Description

Technical Field

[0001] The present invention relates to the field of lychee thawing, and in particular to a system and method for thawing frozen lychees based on ultrasonic coordinated water bath thawing. Background Art

[0002] Lychee, a tropical fruit, is widely cultivated in southern China and is widely loved by consumers for its unique sweet taste and rich nutritional value. However, lychees are highly seasonal and are usually stored frozen to extend their shelf life. However, traditional thawing methods often damage the lychee cell structure, affecting its taste and flavor. In recent years, ultrasonic technology has shown great potential in the field of food thawing due to its ability to accelerate material transfer and promote ice crystal refinement. However, relying solely on ultrasonic thawing is still difficult to achieve the ideal thawing effect and flavor restoration. Therefore, the present invention proposes a frozen lychee thawing device, medium and method based on ultrasonic coordinated water bath thawing, aiming to optimize the thawing process through an intelligent control algorithm to achieve optimal restoration of the lychee flavor. Summary of the Invention

[0003] The main purpose of the present invention is to provide a system and method for thawing frozen lychees based on ultrasound-assisted water bath thawing, which can realize automatic adjustment of the thawing process.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: a frozen lychee thawing system based on ultrasonic wave-assisted water bath thawing, comprising:

[0005] A water bath, which is a rectangular parallelepiped structure with an upward opening. When thawing, a certain amount of water is placed in the water bath;

[0006] An ultrasonic generating assembly and a temperature sensor are arranged on the inner wall of the water bath, the ultrasonic generating assembly is used to emit ultrasonic waves, and the temperature sensor is used to detect the water temperature in the water bath;

[0007] A heating component is provided at the inner bottom of the water bath, and is used to heat the water;

[0008] A control module and a protection component are arranged outside the water bath, the control module is electrically connected to the ultrasonic generating component, the temperature sensor, the heating component, and the protection component; the protection component is a water level sensor for detecting the water level in the water bath;

[0009] and a stirring component rotatably arranged in the water bath tank, for stirring the water in the water bath tank and the thawed lychees.

[0010] The present invention also provides a method for thawing frozen lychees based on ultrasonic wave-assisted water bath thawing, which uses the above-mentioned thawing system and specifically includes the following steps:

[0011] Step S1: Set the target thawing time t through the control module target , target thawing temperature T target and the initial stirring speed v stir0 ;

[0012] Step S2: thawing time t according to the set target target , target thawing temperature T target and stirring speed v stir0 Calculation of the initial power P of the ultrasonic generating component by the litchi thawing state estimation method ultrasound0 and the initial power P of the heating element heating0 ;

[0013] Step S3: Start the system and continuously estimate the real-time temperature T of the litchi using the thawing state estimation method;

[0014] Step S4: Using the dynamic prediction model, according to the real-time temperature T of the litchi and the target thawing temperature T target And the preset defrost time t target , evaluate the current thawing progress;

[0015] Step S5: Dynamically adjust the ultrasonic power P according to the current thawing progress. ultrasound , heating power P heating、 Water bath temperature T water and stirring speed v stir , to optimize the thawing process.

[0016] Preferably, the method for estimating the thawing state of litchi comprises the following steps:

[0017] Step a: Calculate the total energy E input by the ultrasonic generating component and the heating component according to the power and operation time of the ultrasonic generating component and the heating component. input :

[0018] E input =P ultrasound ×t ultrasound +P heating ×t heating ,

[0019] Among them, P ultrasound and P heating are the power of ultrasonic generating component and heating component respectively, t ultrasound and t heating are the operating time of the ultrasonic generating component and the heating component respectively;

[0020] Step b: Use a temperature sensor to monitor the change in water temperature in the water tank, and calculate the energy absorbed by the water temperature rise based on the specific heat capacity of water and the amount of water:

[0021] Ewater =m water ·C water ΔT water ,

[0022] Among them, E water Refers to the energy required to increase the water temperature, m water is the amount of water in the water bath, C water is the specific heat capacity of water, ΔT water is the change in water temperature;

[0023] Step c: According to the law of conservation of energy, the energy absorbed by the litchi is equal to the total energy input by the system minus the energy absorbed by the water temperature rise and the energy loss of the system, that is:

[0024] E lychee =E input -E water -E loss ,

[0025] E lychee The energy absorbed by litchi, E loss is the energy lost during the thawing process;

[0026] E loss Heat loss due to conduction E thermal , ultrasonic energy scattering loss E ultrasound , mechanical friction loss E mechanical And electrical efficiency loss E electrical It consists of four parts:

[0027] E loss =E thermal +E ultrasound +E mechanical +E electrical ,

[0028] Among them, the heat conduction loss E thermal The calculation formula is as follows:

[0029] E thermal =U·A·ΔT ambient ·t total ,

[0030] Where U is the comprehensive thermal conductivity of the water bath, which is related to the material and insulation layer; A is the effective heat dissipation area of the water bath; ΔT ambient is the difference between the water bath temperature and the ambient temperature; t total is the cumulative thawing time;

[0031] Ultrasonic energy scattering loss E ultrasound The calculation formula is as follows:

[0032] E ultrasound=η scatter ·P ultrasound ·t ultrasound ,

[0033] Where η scatter is the scattering efficiency coefficient; P ultrasound is the ultrasonic power (W); t ultrasound is the cumulative running time of ultrasound (s);

[0034] Mechanical friction loss E ultrasound The calculation formula is as follows:

[0035]

[0036] Where μ is the fluid friction coefficient; ρ water is the water density; v stir is the stirring speed; t stir Cumulative stirring time;

[0037] Electrical efficiency loss E ultrasound The calculation formula is as follows:

[0038] E electrical =(1-ε heating )·P heating ·t heating +(1-ε ultrasound )·P ultrasound ·t ultrasound ,

[0039] Where, ε heating , ε ultrasound The power conversion efficiency of the heating component and the ultrasonic generating component;

[0040] Step d: establishing the relationship between the energy absorbed by litchi and the temperature change of litchi:

[0041] Q=m·C p ΔT,

[0042] Q=E lychee , m is the mass of litchi; C p is the specific heat capacity of litchi; ΔT is the change in temperature of litchi, ΔT = T target -T0, T0 is the initial temperature of litchi before thawing.

[0043] Preferably, in step S5, the control module adopts PID control to perform dynamic adjustment, and the specific steps are as follows:

[0044] Step S51: When the thawing progress is delayed, that is, the litchi real-time temperature T<target temperature T target If the remaining time is not enough to reach the target at the current speed, the ultrasonic power P needs to be increased. ultrasoundand heating power P heating , the adjustment formula is as follows:

[0045]

[0046]

[0047] Among them: K p , K d , K i is the dynamic gain coefficient output by the fuzzy PID controller, α and β are energy coupling factors, and m lycee is the total mass of litchi, t remain The remaining thawing time.

[0048] Preferably, the step S5 further includes a step S52: if the thawing progress is ahead, that is, the current temperature T is higher than the expected temperature or has reached the target temperature T target But there is still time left, then the ultrasonic power P needs to be reduced ultrasound and heating power P heating , the adjustment formula is as follows:

[0049]

[0050]

[0051] Where λ is the ultrasonic attenuation coefficient and η is the heating power attenuation exponent.

[0052] Preferably, the step S5 further includes step S53: introducing an online learning mechanism to update the control parameters according to the historical thawing data:

[0053]

[0054]

[0055] Among them, E loss is the system energy loss function, and δ is the learning rate.

[0056] Preferably, the step S5 specifically includes step S54: adjusting the stirring speed, the stirring speed v stir Coupled with power adjustment to prevent local overheating:

[0057]

[0058] ρ is the density of water, C water is the specific heat of water, V water is the volume of water; v base is the base stirring speed (default 200 rpm), which can be the initial stirring speed v stir0 .

[0059] Compared with the prior art, the present invention has the following beneficial effects:

[0060] 1) The present invention introduces ultrasound on the basis of heating. Ultrasonic waves cooperate with water bath to accelerate the melting of ice crystals and shorten the thawing time;

[0061] 2) An adaptive control algorithm was added to adjust the thawing conditions according to the characteristics of litchi. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 is a perspective view of the thawing system of the present invention;

[0063] Figure 2 It is a cross-sectional view. DETAILED DESCRIPTION

[0064] The following description is intended to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are merely examples, and those skilled in the art may conceive of other obvious variations.

[0065] Example 1

[0066] A frozen lychee thawing system based on ultrasonic-assisted waterbath thawing includes a waterbath 2, an ultrasonic generator assembly 1 and a temperature sensor 3 disposed on the inner wall of the waterbath 2, a heating assembly 5 disposed on the inner bottom of the waterbath 2, a control module 4 and a protective assembly 7 disposed on the outer side of the waterbath 2, and a stirring assembly 6 rotatably disposed within the waterbath 2. The waterbath 2 is a rectangular parallelepiped structure with an upward opening. During thawing, a certain amount of water is placed in the waterbath 2, and lychees are placed in the water. After thawing begins, the ultrasonic generator assembly 1 and the heating assembly 5 operate simultaneously, and the stirring assembly 6 stirs simultaneously. The temperature sensor 3 monitors the water temperature in real time. The control module 4 can obtain the temperature detected by the temperature sensor 3 and control the power of the ultrasonic generator assembly 1 and the heating assembly 5, as well as the stirring speed of the stirring assembly 6. A PID control model is integrated into the control module 4. The protective assembly is a water level sensor that detects the water level in the waterbath 2. When the water level falls below a certain value, the control module 4 stops the ultrasonic generator assembly 1, the heating assembly 5, and the stirring assembly 6 to prevent dry burning.

[0067] Example 2

[0068] This embodiment is a method for thawing litchi using the system in Example 1, which specifically includes the following steps:

[0069] Step S1, set the target thawing time t target , target thawing temperature T target and the initial stirring speed v stir0 ;

[0070] Step S2: thawing time t according to the set target target , target thawing temperature T target and stirring speed v stir0 Calculate the initial power P of the ultrasonic generating component 1 by the litchi thawing state estimation method ultrasound0 and the initial power P of the heating component 5 heating0 ;

[0071] Step S3: Start the system and continuously estimate the real-time temperature T of the litchi using the thawing state estimation method;

[0072] Step S4: Using the dynamic prediction model, according to the real-time temperature T of the litchi and the target thawing temperature T target And the preset defrost time t target , evaluate the current thawing progress;

[0073] According to the real-time temperature T of litchi and the target thawing temperature T target And the preset defrost time t target , the current thawing progress is evaluated by a dynamic prediction model; the dynamic prediction model is based on the law of conservation of energy, and the current temperature change rate ΔT / Δt and the target temperature difference (T target -T), calculate the remaining thawing time t remain_estimate and the preset remaining time t remain Compare and determine whether power adjustment is necessary.

[0074] Step S5: Dynamically adjust the ultrasonic power P according to the current thawing progress. ultrasound , heating power P heating、 Water bath temperature T water and stirring speed v stir , to optimize the thawing process.

[0075] The method for estimating the thawing state of litchi specifically comprises the following steps:

[0076] Step a: Calculate the total energy input by the ultrasonic generating component 1 and the heating component 5 according to the power and operating time of the ultrasonic generating component 1 and the heating component 5:

[0077] E input =P ultrasound ×t ultrasound +P heating ×t heating ,

[0078] Among them, P ultrasound and P heating are the power of ultrasonic generating component 1 and heating component 5, t ultrasound and t heating are the operating time of the ultrasonic generating component 1 and the heating component 5 respectively;

[0079] Step b: Use a temperature sensor to monitor the change in water temperature in the water tank, and calculate the energy absorbed by the water temperature rise based on the specific heat capacity of water and the amount of water:

[0080] E water =m water ·C water ΔT water ,

[0081] Among them, E water Refers to the energy required to increase the water temperature, m water is the amount of water in the water bath, C water is the specific heat capacity of water, ΔT water is the change in water temperature;

[0082] Step c: According to the law of conservation of energy, the energy absorbed by the litchi is equal to the total energy input by the system minus the energy absorbed by the water temperature rise and the energy loss of the system, that is:

[0083] E lychee =E input -E water -E loss ,

[0084] E lychee The energy absorbed by litchi, E loss It is the energy lost during the thawing process;

[0085] E loss Heat loss due to conduction E thermal , ultrasonic energy scattering loss E ultrasound , mechanical friction loss E mechanical And electrical efficiency loss E electrical It consists of four parts:

[0086] E loss =E thermal +E ultrasound +E mechanical +E electrical ,

[0087] Among them, the heat conduction loss E thermal It is caused by the heat exchange between the water bath and the surrounding environment. The calculation formula is as follows:

[0088] E thermal =U·A·ΔT ambient ·t total ,

[0089] Where U is the comprehensive heat conductivity coefficient of the water bath (W / m 2 ·℃), which is related to the material and insulation layer; A is the effective heat dissipation area of the water bath (m 2); ΔT ambient is the difference between the water bath temperature and the ambient temperature (°C); t total is the cumulative thawing time (s);

[0090] Ultrasonic energy scattering loss E ultrasound The non-ideal propagation of ultrasonic waves in the medium causes:

[0091] E ultrasound =η scatter ·P ultrasound ·t ultrasound ,

[0092] Where η scatter is the scattering efficiency coefficient (needs experimental calibration); P ultrasound is the ultrasonic power (W); t ultrasound is the cumulative running time of ultrasound (s);

[0093] Mechanical friction loss E ultrasound Energy loss caused by friction during operation of the stirring assembly 6:

[0094]

[0095] Where μ is the fluid friction coefficient (related to the shape of the stirring blade); ρ water is the water density (kg / m 3 );v stir is the stirring speed (m / s); t stir is the cumulative stirring time (s).

[0096] Electrical efficiency loss E ultrasound Caused by insufficient power conversion efficiency of the heating system and ultrasonic generator:

[0097] E electrical =(1-ε heating )·P heating ·t heating +(1-ε ultrasound )·P ultrasound ·t ultrasound ,

[0098] Where, ε heating , ε ultrasound It is the electrical energy conversion efficiency of the heating component 5 and the ultrasonic generating component 1.

[0099] Step d: establishing the relationship between the energy absorbed by litchi and the temperature change of litchi:

[0100] Q=m·C p ΔT,

[0101] Q=E lychee, m is the mass of litchi (unit: kilogram); C p is the specific heat capacity of litchi (unit: joule / kg·degrees Celsius); ΔT is the change in litchi temperature, that is (unit: degrees Celsius), ΔT = T target -T0, T0 is the initial temperature of litchi before thawing.

[0102] In step S2, the target is unfrozen for a period of time t target , target thawing temperature T target Substituting into step d, we can get E lychee , and then we can get E by reverse deduction input In practice, the ratio between ultrasonic energy and heating energy needs to be allocated based on experience. Once the ratio is determined, the initial power P can be determined. ultrasound0 and initial power P heating0 .

[0103] In step S3, after determining the initial power P ultrasound0 and initial power P heating0 Afterwards, the total energy input from the beginning to the current moment can be calculated, as well as the energy absorbed by the water and the energy lost. Finally, the heat input into the lychee at the current moment can be calculated. ΔT can be calculated through step d, and the temperature at the current moment can be estimated.

[0104] In step S5, PID control is used for dynamic adjustment. The specific steps are as follows:

[0105] Step S51: When the thawing progress is delayed, that is, the litchi real-time temperature T<target temperature T target , and the remaining time is not enough to reach the target at the current speed, it is necessary to increase the ultrasonic power P ultrasound and heating power P heating , in order to increase the thawing rate. At the same time, appropriately increase the stirring speed v stir , to promote the uniform distribution of heat and ultrasonic energy. Specifically, the dynamic gain coefficient method is used to adjust the power:

[0106]

[0107]

[0108] Among them: K p , K d , K i is the dynamic gain coefficient output by the fuzzy PID controller (adjusted in real time according to the litchi variety and quality); α and β are energy coupling factors, which are determined by the thermal conductivity of the water bath medium and the ultrasonic penetration efficiency; m lychee is the total mass of litchi, t remain The remaining thawing time;

[0109] Calculate the remaining time and clarify the judgment logic of thawing progress based on the temperature change rate and energy demand:

[0110] Define the current temperature change rate:

[0111] Calculate the remaining time estimate:

[0112] Remaining time estimate: If t remain_estimate >t remain , it is judged as "insufficient remaining time".

[0113] Step S52: If the thawing progress is ahead, that is, the current temperature T is higher than the expected temperature or has reached the target temperature T target But there is still time left, then the ultrasonic power P needs to be reduced ultrasound and heating power P heating To prevent over-thawing. Stirring speed v stir Or reduce it appropriately to reduce unnecessary energy consumption and possible damage to the litchi. The specific power is reduced according to the exponential decay strategy:

[0114]

[0115]

[0116] Where: λ is the ultrasonic attenuation coefficient (negatively correlated with litchi cell density), η is the heating power attenuation exponent (determined by the heat capacity of the water bath).

[0117] Step S53: Introduce an online learning mechanism to update control parameters based on historical thawing data:

[0118]

[0119]

[0120] Where: E loss is the system energy loss function, δ is the learning rate (adaptive adjustment, initial value 0.01);

[0121] Step S54: Adjust the stirring speed. stir Coupled with power adjustment to prevent local overheating:

[0122]

[0123] ρ is the density of water, C water is the specific heat of water, V water is the volume of water; v base is the base stirring speed (default 200 rpm), which can be the initial stirring speed vstir0 .

[0124] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions merely illustrate the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the invention as claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A frozen litchi thawing system based on ultrasonic wave assisted water bath thawing, comprising: A water bath, which is a rectangular parallelepiped structure with an upward opening. When thawing, a certain amount of water is placed in the water bath; An ultrasonic generating assembly and a temperature sensor are arranged on the inner wall of the water bath, the ultrasonic generating assembly is used to emit ultrasonic waves, and the temperature sensor is used to detect the water temperature in the water bath; A heating component is provided at the inner bottom of the water bath, and is used to heat the water; A control module and a protection component are arranged outside the water bath, the control module is electrically connected to the ultrasonic generating component, the temperature sensor, the heating component, and the protection component; the protection component is a water level sensor for detecting the water level in the water bath; and a stirring component rotatably arranged in the water bath tank, for stirring the water in the water bath tank and the thawed lychees.

2. A method for thawing frozen lychees based on ultrasonic wave-assisted water bath thawing, using the thawing system according to claim 1, characterized in that: The specific steps include: Step S1: Set the target thawing time t through the control module target , target thawing temperature T target and the initial stirring speed v stir0 ; Step S2: thawing time t according to the set target target , target thawing temperature T target and stirring speed v stir0 Calculation of the initial power P of the ultrasonic generating component by the litchi thawing state estimation method ultrasound0 and the initial power P of the heating element heating0 ; Step S3: Start the system and continuously estimate the real-time temperature T of the litchi using the thawing state estimation method; Step S4: Using the dynamic prediction model, according to the real-time temperature T of the litchi and the target thawing temperature T target And the preset defrost time t target , evaluate the current thawing progress; Step S5: Dynamically adjust the ultrasonic power P according to the current thawing progress. ultrasound , heating power P heating、 Water bath temperature T water and stirring speed v stir , to optimize the thawing process.

3. A thawing method according to claim 2, characterized in that: The method for estimating the thawing state of litchi specifically comprises the following steps: Step a: Calculate the total energy E input by the ultrasonic generating component and the heating component according to the power and operation time of the ultrasonic generating component and the heating component. input : E input =P ultrasound ×t ultrasound +P heating ×t heating Among them, P ultrasound and P heating are the power of ultrasonic generating component and heating component respectively, t ultrasound and t heating are the operating time of the ultrasonic generating component and the heating component respectively; Step b: Use a temperature sensor to monitor the change in water temperature in the water tank, and calculate the energy absorbed by the water temperature rise based on the specific heat capacity of water and the amount of water: E water =m water ·C water ·ΔT water , Among them, E water Refers to the energy required to increase the water temperature, m water is the amount of water in the water bath, C water is the specific heat capacity of water, ΔT water is the change in water temperature; Step c: According to the law of conservation of energy, the energy absorbed by the litchi is equal to the total energy input by the system minus the energy absorbed by the water temperature rise and the energy loss of the system, that is: AND lychee =And input -AND water -AND loss , E lychee The energy absorbed by litchi, E loss is the energy lost during the thawing process; E loss Heat loss due to conduction E thermal , ultrasonic energy scattering loss E ultrasound , mechanical friction loss E mechanical And electrical efficiency loss E electrical It consists of four parts: AND loss =And thermal +E ultrasound +E mechanical +E electrical Among them, the heat conduction loss E thermal The calculation formula is as follows: E thermal =U·A·ΔT ambient ·t total , Where U is the comprehensive thermal conductivity of the water bath, which is related to the material and insulation layer; A is the effective heat dissipation area of the water bath; ΔT ambient is the difference between the water bath temperature and the ambient temperature; t total is the cumulative thawing time; Ultrasonic energy scattering loss E ultrasound The calculation formula is as follows: AND ultrasound =η scatter ·P ultrasound ·t ultrasound , Where η scatter is the scattering efficiency coefficient; P ultrasound is the ultrasonic power (W); t ultrasound is the cumulative running time of ultrasound (s); Mechanical friction loss E ultrasound The calculation formula is as follows: Where μ is the fluid friction coefficient; ρ water is the water density; v stir is the stirring speed; t stir Cumulative stirring time; Electrical efficiency loss E ultrasound The calculation formula is as follows: E electrical =(1-e heating )·P heating ·t heating +(1-e ultrasound )·P ultrasound ·t ultrasound , Where, ε heating , ε ultrasound The power conversion efficiency of the heating component and the ultrasonic generating component; Step d: establishing the relationship between the energy absorbed by the litchi and the temperature change of the litchi: Q=m·C p ·ΔT, Q=E lychee , m is the mass of litchi; C p is the specific heat capacity of litchi; ΔT is the change in temperature of litchi, ΔT = T target -T0, T0 is the initial temperature of litchi before thawing.

4. A thawing method according to claim 3, characterized in that: In step S5, the control module uses PID control to perform dynamic adjustment. The specific steps are as follows: Step S51: When the thawing progress is delayed, that is, the litchi real-time temperature T<target temperature T target If the remaining time is not enough to reach the target at the current speed, the ultrasonic power P needs to be increased. ultrasound and heating power P heating , the adjustment formula is as follows: Among them: K p , K d , K i is the dynamic gain coefficient output by the fuzzy PID controller, α and β are energy coupling factors, and m lycee is the total mass of litchi, t remain The remaining thawing time.

5. A thawing method according to claim 4, characterized in that: The step S5 further includes a step S52: if the thawing progress is ahead, that is, the current temperature T is higher than the expected or has reached the target temperature T target But there is still time left, then the ultrasonic power P needs to be reduced ultrasound and heating power P heating , the adjustment formula is as follows: Where λ is the ultrasonic attenuation coefficient and η is the heating power attenuation exponent.

6. A thawing method according to claim 5, characterized in that: The step S5 further includes step S53: introducing an online learning mechanism to update the control parameters according to the historical thawing data: Among them, E loss is the system energy loss function, and δ is the learning rate.

7. A thawing method according to claim 6, characterized in that: The step S5 specifically includes step S54: adjusting the stirring speed, the stirring speed v stir Coupled with the power adjustment amount, the adjustment formula is as follows: ρ is the density of water, C water is the specific heat of water, V water is the volume of water; v base is the base stirring speed.

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