Conveying Temperature
When you talk about temperature, you may also talk about heat together. However, temperature and heat are different.
While temperature is a measure of the warmth and coolness of an object, heat is the energy stored in the object. Heat is exchanged between objects, and the result is called temperature. The heat and temperature are discussed in this section.
Materials with higher temperatures have more heat (energy).
What is “heat” in the first place? Its identity is the vibrations of atoms and molecules called thermal vibrations. When you touch something and feel hot, the atoms on the surface of the object are vigorously vibrating.
It is also known that low temperatures have a limit. This is because as the temperature of the material decreases, the thermal vibration will eventually stop. The temperature at this time is called absolute zero.
Around 1800, two French scientists, Charles and Gay-Lussac, discovered that the volume of the gas was proportional to temperature, with an absolute zero of-273.15°C.
Humans and objects have heat.
When a person touches an object, it feels cold or warm.
People’s skin has thermal receptors called cold sense and warmth, so when a person touches something that is cooler than its own body temperature, the chill feels cool by responding and sending a signal to the brain. On the other hand, when a person touches something that is warmer than his or her own body temperature, his or her sense of temperature responds and sends a signal to his or her brain, and he or she feels warm.
There are three types of heat transfer.
A phenomenon in which heat is transferred directly from the other party by touching an object is called heat conduction. If you touch the handle of the wok directly, it will feel so hot that you will burn yourself.
The way of heat transfer varies depending on the object. The ladle of the Chinese ladle is very hot and not touched with bare hands, but I think it will be touched with the plastic handle.
This is due to the inherent thermal conductivity of the material. The higher the thermal conductivity, the easier it is to transfer heat.
Heat transfer is a phenomenon whereby air conducts heat even if it does not directly touch an object. Direct contact (heat conduction) with the flame by a fire can cause burns, but if it hits the flame at a certain distance, it will cause it to warm up. This phenomenon is called heat transfer, in which the air is heated by an open-air fire and the air feels warm because it transmits heat to people (the “wind blows up the tub”).
This phenomenon, in which heat is transferred neither to the object nor to the air, is called radiation. In our familiar case, the heat from the sun reaches us on the earth. Because of the vacuum between the sun and Earth in space, there is no gas for heat transfer. Even so, the heat from the sun is transmitted. This is because objects always emit energy (electromagnetic waves, which are difficult to say), which does not affect the distance or the medium but can reach the other party directly. This phenomenon is called radiation.
The phenomenon of burning when a flammable material is heated and a fire source is brought close
※Flash point: Minimum temperature at which combustibles generate flammable vapors required for combustion
| Material | Flash point[°C] |
|---|---|
| Gasoline | -43 or less |
| Acetone | -18 |
| Benzene | -11 |
| Methyl alcohol | 11 |
| Kerosene | 40 ～ 60 |
| Light oil | 40 ～ 70 |
| Heavy oil | 60 ～ 100 |
| Naphthalene | 79 |
| Glycerin | 160 |
| Sewing oil | 289 ～ 304 |
| Rapeseed oil | 313 ～ 320 |
A phenomenon in which flammable substances are heated and burnt even if a fire source is not brought close
※Ignition point: Minimum temperature at which combustible materials will burn
| Material | Ignition point[°C] |
|---|---|
| Light oil | 250 |
| Heavy oil | 250 ～ 380 |
| Kerosene | 255 |
| Gasoline | 300 |
| Rapeseed oil | 360 ～ 380 |
| Glycerin | 393 |
| Methyl alcohol | 464 |
| Benzene | 498 |
| Naphthalene | 526 |
| Acetone | 538 |
When the temperature of food exceeds 200°C, sugar, oil, and protein will be carbonized and char.
Change from brown to black. A burning offensive odor is generated.
To heat food deliciously, heat it within the range of 160 to 180°C [medium fire] where the Maillard reaction occurs.
Top 10 Metal Heat Resistance Ranking !
Hydrogen is attracting attention as a next-generation energy source. The lightest gas in the world that reacts violently with oxygen to form water. As a method of storing and transporting the hydrogen, it is considered to be made into a liquid. The reason is that at room temperature, if gaseous hydrogen is used as a liquid, the volume is only about 1/800, which is highly efficient. Liquid hydrogen is also used as fuel for rockets. Hydrogen has a boiling point of-253°C, so a refrigerator that is kept at a very low temperature is required to be stored as a liquid. A thermometer is also required to check the temperature inside this refrigerator. YAMARI INDUSTRIES, LIMITED also produces thermometers for measuring these cryogenic temperatures.
Analog thermometers include dial and tubular thermometers.
The dial type is used for gas and industrial applications. In principle, two metals with different coefficient of thermal expansion are laminated together, and the dial rotates to indicate the temperature according to the degree of deformation of the laminated metal.
Tubular shape is used for air (air temperature), water (water temperature), etc. The principle is that in the case of a mercury thermometer, the temperature is displayed when the mercury expands and moves up and down.
A thermometer that uses cameras that have become more visible in recent years.
This is a camera-type thermometer. Because such camera-type body temperature measurement is non-contact, it is thought to reduce the risk of transmission of viruses, etc. compared to contact body temperature measurement.
This camera is called a thermal camera and detects heat.
Humans and objects always emit infrared rays. By detecting the infrared rays and converting the intensity of the object’s infrared rays into temperature, the temperature of the object is measured by a camera.
The metal with the highest melting temperature is tungsten!
All BEST 3 materials exceed 3000°C.
Tungsten and rhenium in rankings 1 and 2 are the component materials of C thermocouples.