CN111261006A

CN111261006A - Leidenfrost effect observation and measurement device based on mobile phone video

Info

Publication number: CN111261006A
Application number: CN202010158872.6A
Authority: CN
Inventors: 姚夙; 韦寿莲; 汪洪武
Original assignee: Zhaoqing University
Current assignee: Zhaoqing University
Priority date: 2020-03-09
Filing date: 2020-03-09
Publication date: 2020-06-09

Abstract

The invention provides a leidenfrost effect observation and measurement device based on mobile phone video, which can be used for researching the vaporization process of liquid drops on the surface of a sample by observing and recording the leidenfrost effect through the mobile phone video with a close-up lens without using expensive equipment such as a macro lens, a high-speed camera and the like, thereby greatly saving the experiment cost; the device measures the surface temperature of the sample in a non-contact manner by using the infrared temperature measuring probe, so that the interference of heat transfer of the sample caused by contact measurement is avoided; the device can observe experimental details with the resolution ratio that exceeds the naked eye, can playback repeatedly and carry out quantitative analysis, is favorable to student's study and teacher to examine experimental result, is fit for popularizing in the teaching.

Description

Leidenfrost effect observation and measurement device based on mobile phone video

Technical Field

The invention relates to the field of experimental teaching instruments, in particular to a leidenfrost effect observation and measurement device based on mobile phone video.

Background

The Leidenfrost Phenomenon (Leidenfrost Phenomenon) refers to the Phenomenon that liquid drops are boiled in a film shape on a high-temperature surface, a layer of steam film is generated to separate the liquid drops from the high-temperature surface, and the liquid drops are slowly gasified. The leidenfrost phenomenon has obvious influence on the processes of gasification, heat transfer and the like, and has important research value in the field of chemical industry. The research on the leidenfrost phenomenon requires the amplified observation and measurement of tiny droplets, and the requirements on a video recording device are high. At present, the research on the Laidenfrost phenomenon lacks mature observation equipment, and expensive macro lenses and high-speed cameras are generally needed to build measuring devices, so that the experiment is difficult to be widely developed in teaching.

Disclosure of Invention

In order to solve the problems, the invention provides a leidenfrost effect observation and measurement device based on mobile phone video.

The purpose of the invention is realized by adopting the following technical scheme:

a leidenfrost effect observation and measurement device based on mobile phone video comprises a mobile phone, a close-up lens, a heater, a sample clamp and an infrared temperature measurement probe, wherein the infrared temperature measurement probe is connected with the heater through a circuit.

Preferably, the heater is made of metal and internally provided with an electric heating coil or electric heating ceramic.

Preferably, the device further comprises a base, an object stage and a mobile phone clamp, wherein the object stage and the mobile phone clamp are respectively arranged on the base.

Further preferably, the stage is made of a heat-resistant material.

Further preferably, the stage is stainless steel or aluminum.

Another objective of the present invention is to provide an experimental method for the leidenfrost effect observation and measurement apparatus based on the mobile phone video:

a sample with a smooth bottom is placed on a heater and is clamped by a sample clamp, so that the bottom of the sample is in close contact with a heater panel, a pit is formed in the upper surface of the sample, an infrared temperature measuring probe above the sample measures the temperature of the sample in a real-time non-contact mode, the temperature of the sample is increased by adjusting the heater, liquid drops are added into the pit, a mobile phone with a close-up lens is close to the pit, the liquid drops are located in the center of a view field, and the vaporization process is.

Further preferably, the sample is a metal, an alloy, a ceramic or the like.

Further preferably, the pits are 5mm in diameter and 1mm deep.

The invention has the beneficial effects that:

(1) the device uses the mobile phone video recording function to observe and measure the leidenfrost phenomenon, does not need expensive equipment such as a macro lens, a high-speed camera and the like, and greatly saves the experiment cost. Meanwhile, experimental details can be observed with a resolution ratio exceeding that of naked eyes, repeated playback and quantitative analysis can be carried out, the experimental result can be favorably checked by students and teachers, and the experimental result monitoring device is suitable for popularization in teaching.

(2) The surface temperature of the sample is measured in a non-contact manner by using the infrared temperature measuring probe, so that the interference of the heat transfer condition of the sample caused by contact measurement is avoided.

(3) The sample surface is provided with pits for limiting the position of the liquid drop and avoiding the liquid drop from rolling to other positions during boiling.

(4) The device has the advantages of simple structure, low cost, convenient manufacture, simple operation and convenient popularization.

Drawings

The invention is further illustrated by means of the attached drawings, but the embodiments in the drawings do not constitute any limitation to the invention, and for a person skilled in the art, other drawings can be obtained on the basis of the following drawings without inventive effort.

FIG. 1 is a schematic structural diagram of a leidenfrost effect observation and measurement device based on a mobile phone video record according to the present application;

FIG. 2 is a difference between nucleate boiling and film boiling;

FIG. 3 is the Leidenfrost effect of water droplets on a copper sheet;

FIG. 4 is a graph of water drop volume as a function of time for a water drop to exhibit the Leidenfrost effect on a copper sheet;

FIG. 5 is a graph of drop volume versus time for the Leidenfrost effect of alcohol and water on a copper sheet.

Reference numerals: 1-a base; 2-an object stage; 3-a heater; 4-sample; 5-a sample holder; 6-infrared temperature measuring probe; 7-liquid droplet; 8-a close-up lens; 9-a mobile phone; 10-mobile phone clamp.

Detailed Description

The invention is further described with reference to the following examples.

Detailed Description

The invention provides a Leidenfrost phenomenon observation device based on a mobile phone video recording function, and the device comprises a base 1, an object stage 2, a heater 3, a sample 4, a sample clamp 5, an infrared temperature measuring probe 6, a close-up lens 8, a mobile phone 9 and a mobile phone clamp 10, and is combined with a figure 1.

Wherein the object stage 2 is installed on the base 1, the object stage 2 is made of heat-resistant material such as stainless steel or aluminum, and can move on three axes X, Y, Z to adjust the position; the heater 3 is flat in surface, made of metal, internally provided with an electric heating coil or electric heating ceramic and arranged on the objective table 2; the sample 4 can be made of metal, alloy, ceramic and other materials, a pit with the diameter of about 5mm and the depth of about 1mm is processed on the upper surface, the bottom of the pit is flatly placed on the heater 3 and is clamped by the sample clamp 5, so that the pit is tightly contacted with the heater panel, and heat transmission is facilitated; the infrared temperature probe 6 is arranged above the sample, can measure the temperature of the sample 4 in a real-time non-contact manner, avoids the interference of contact measurement on the heat transfer of the sample, and can realize real-time temperature control and constant temperature maintenance by the circuit connection of the infrared temperature probe 6 and the heater 3.

When in use, the heater 3 is adjusted to ensure that the sample 4 is at a proper temperature, about 3 mu L of liquid is added into the pit of the sample 4 by using the microsyringe to form a liquid drop 7, and the liquid drop is continuously gasified on the surface of the sample 4; the pits on the surface of the sample 4 limit the position of the liquid drop 7, so that the liquid drop does not roll around when boiling; when the surface temperature of the sample 4 is low, the heat transferred from the surface to the liquid drop 7 is not enough to maintain film boiling, and the sample does not boil or shakes violently to carry out nucleate boiling; when the surface temperature of the sample 4 is higher, the liquid drop 7 is spherical, stable film boiling occurs, and the gasification time is obviously prolonged compared with the nucleate boiling.

A mobile phone 9 with a close-up lens 8 is arranged on a mobile phone clamp 10, a camera of the mobile phone is about 4cm away from the liquid drops 7, the objective table 2 is adjusted to enable the liquid drops to be positioned at the center of a view field, and the whole process of vaporization of the liquid drops 7 is recorded by video recording; the close-up lens 8 reduces the resultant focal length of the lens so that the lens can be focused on the droplet 7 at a closer distance, thereby achieving a higher resolution, observing more details of the droplet 7; after the experiment is finished, the experiment video can be played back repeatedly, which is beneficial to students to study and teachers to check the experiment result; in addition, the water drop volume can be calculated by measuring the water drop diameter at different moments by combining time information in the video, a curve of the water drop volume along with the change of time is drawn, the gasification speed is calculated, and quantitative research is carried out on the Leidenfrost effect.

Example 1

Observation of the difference between nucleate boiling and film boiling

In this example, a copper sheet was used as a sample, droplets were used as water droplets, the copper sheet was heated to 150 ℃ and 210 ℃ respectively, 3. mu.L of pure water was added to the pits of the copper sheet, and the water atomization process was observed by video recording. As shown in figure 2, when the surface temperature is 150 ℃, the water beads are steeply nucleate and boiled on the copper sheet, the hoarse sound is generated, and the water beads are rapidly disappeared within 6s, when the surface temperature is 210 ℃, the water beads are subjected to stable film boiling, the disappearance time is 39s, and the gasification speed is obviously lower than that when the surface temperature is 150 ℃.

Example 2

Observation of the Leidenfrost effect of water droplets on a copper sheet

In this example, a copper sheet was used as a sample, a droplet was used as a water droplet, the copper sheet was heated to 240 ℃, 3 μ L of pure water was added to the pit of the copper sheet, and the process of water vaporization was observed by video recording. As shown in fig. 3, it is clearly observed that the water droplets remained substantially spherical, gradually decreased and disappeared during the entire vaporization process, and the time from the addition of the water droplets to the completion of the vaporization of the water droplets was 28 seconds. The water drop volume was calculated by measuring the water drop diameter, and the change of the water drop volume with time was also quantitatively investigated, and the result is shown in fig. 4.

Example 3

Observation of the leidenfrost effect of alcohols and water on copper sheets

In this example, the copper sheet was used as a sample, and differences between methanol, ethanol, isopropanol, and n-butanol and the leidenfrost effect of the water droplet were studied. The initial temperatures were all set at 210 ℃, as shown in fig. 5, the time for vaporization of methanol, ethanol, isopropanol, n-butanol and water droplets was 19s, 9s, 13s, 10s and 40s, respectively, where the vaporization time of water was significantly longer, which may be related to the specific heat capacity of alcohols being much smaller than that of water.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the protection scope of the present invention, although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. The leidenfrost effect observation and measurement device based on mobile phone video is characterized by comprising a mobile phone, a close-up lens, a heater, a sample clamp and an infrared temperature measurement probe, wherein the infrared temperature measurement probe is in circuit connection with the heater.

2. The leidenfrost effect observation and measurement device based on the mobile phone video according to claim 1, wherein the heater is made of metal and internally installed with an electric heating coil or an electric heating ceramic.

3. The leidenfrost effect observation and measurement device based on videophone as claimed in claim 1, further comprising a base, a stage and a cell phone holder, wherein the stage and the cell phone holder are respectively mounted on the base.

4. The leidenfrost effect observation and measurement device based on the mobile phone video according to claim 3, wherein the stage is made of heat-resistant material.

5. The leidenfrost effect observation and measurement device based on videophone as claimed in claim 4, wherein the stage is stainless steel or aluminum.

6. A method for using the observation and measurement device of any one of claims 1 to 5, wherein a sample with a flat bottom is placed on a heater, and is clamped by a sample clamp, so that the bottom of the sample is in close contact with a heater panel, a pit is arranged on the upper surface of the sample, an infrared temperature measuring probe above the sample measures the temperature of the sample in real time in a non-contact manner, the heater is adjusted to heat the sample, a liquid drop is added into the pit, a mobile phone with a close-up lens is close to and enables the liquid drop to be positioned in the center of a visual field, and the vaporization process is recorded.

7. Use according to claim 6, wherein the sample is a metal, an alloy or a ceramic.

8. Use according to claim 6, wherein the pits are 5mm in diameter and 1mm deep.