The main types of heat transfer in everyday life are the redistribution of temperatures by heating, radiation or convection. Different materials have different properties. Good conductors are all metal products.
Classification
There are the main types of heat transfer in everyday life: thermal conductivity (between solids), convection (related to gaseous media), radiation (heat transfer in a non-contact way). Heat transfer refers to the action of energy conversion within an object without exerting external influence on it. Heat transfer occurs due to internal processes.
Types of heat transfer in the home:
- Energy transfer from the heated sole of the iron to the tissues.
- Heating the metal insert of the knife handle after lowering its tip into boiling water.
- The handle of a metal soup ladle becomes fiery after lowering it in a hot soup.
- Heated light from an incandescent lamp placed inside the chandelier.
The listed processes describe only some types of heat transfer in everyday life. Heating the air from a battery is an example of convection when energy is passively transferred from a solid to a gaseous substance. This process is described by the interaction of molecules with each other.
Materials
It is easiest to consider examples of heat transfer in nature and everyday life on metal objects. They have the highest rates of thermal conductivity. These include copper rods (tripods, wire, pipes, springs), steel and alloys.
Proof of heat transfer is a glass thermometer. The steel leg is in contact with mercury, heated by the human body. The liquid substance begins to expand, which we see on the built-in scale.
Plastics also transmit heat well. We observe this process in the process of charging a smartphone, tablet or laptop. The back cover is always warmer. There the redistribution of internal energy takes place.
The studied types of heat transfer in nature and in everyday life are used everywhere. In a conventional kettle, heat is transferred from the metal casing to the liquid. And she, in turn, heats the handle of plastic material. The energy transfer in the latter case is due to steam.
Patterns around us
Heat transfer in nature, technology, everyday life depends on many conditions. The materials in contact with each other transmit energy in different ways. This we can see on the example of a regular window. Between the glass surfaces, a gap from the air gap is conceived. The latter weakly transfers heat.
Glass surfaces quickly receive and give off energy. Porous materials have practically zero thermal conductivity. Therefore, they are used for insulation of building facades during construction.
The proof of various thermal conductivity is clothing made from fabrics of various properties. Wool and other fleecy materials do not conduct heat well. And raincoat fabric (synthetics) transmits energy instantly. Therefore, in products made from such fabrics it is cold in winter.
Patterns of the house
In the morning, pouring a mug of hot tea, what kind of heat transfer can we see? Their accounting and use in everyday life will look like this:
- A mug of hot tea is placed in a cup holder made of weakly heat-conducting material. Often this option is used by conductors on trains.
- Metal pans are equipped with lids with handles made of balsa wood or plastic. The latest materials practically do not heat up.
- Handles of knives, spoons, ladles are also made out with plastic inserts.
- For gas and electric stoves, the surface of the oven is covered with foil material that can reflect heat. And between the body and the heating elements, air gaps are provided.
For a rational air flow in the room, the air vents on the windows are located upstairs. Heat always rises, and cold air from the street helps to evenly distribute energy in the room. When we open the window, it is primarily the feet that freeze . This unevenness is evened out by convection.
Differences
There are peculiarities of different types of heat transfer. In convection, mainly heat transfer occurs due to the mixing of gases. Molecules transmit energy through contact. At the end of the process, the temperature in the closed volume is equalized. After closing the window in the room, the air temperature is the same everywhere, if there are no other sources of heat or cold.
Heat transfer depends on the type of material. So, steel and copper after contact will differ in temperature. This is due to various properties of energy transfer. A heated metal object does not heat the cork material. A spoon in a glass of tea is heated so that it is impossible to pick it up. However, it can be made of aluminum alloy, and it has low thermal conductivity.
Radiation is observed in all of the above examples. Due to this phenomenon, a slight loss of energy occurs. In household appliances, this phenomenon is observed especially strongly: in heaters, irons, soldering irons. You can notice the rays by raising your hand at a distance to the heating surface. It should feel a little warmth - this is due to infrared radiation.
Radiation
All types of heat transfer are used in nature, everyday life, and technology. Infrared radiation can be found in medical devices. It has a positive effect on the surface of the body. In this way, muscles, joints, internal organs are warmed up.
In nature, the main source of heat is the sun's rays. It is radiation that warms the planet Earth. All plants feed on this energy. The seas and oceans, the air moves. Winds form under the influence of the infrared spectrum.
Radiation is taken into account in the production of all household appliances operating on electric current. Telephone mobile devices are constantly heated. That is why it is not recommended to place smartphones in the region of the heart.
Evidence of patterns by experiments
For a simple experiment, a small copper wire is required. Two ends are exposed, one of which is taken in the hand. The second is placed over a fire or in boiling water.
Gradually, both ends become hot. But in the field of insulation, the wire can be safely held. This is evidence of thermal conductivity. For a convection experiment, just open the window. The items below will be colder than the ceiling. After closing the window, the temperature of the bodies will equalize.
Radiation can be felt from any heated object. At a distance, heat transfer is felt. When ice melts at a distance, cold is also felt. You can feel the invisible rays with your hand if you shove it into the space of the refrigerator freezer.
Thermal conductivity is felt when the washing machine. It is enough to touch the hatch when heating the water. Wax on a candle is needed to reduce heat transfer so that it burns longer.
Experiments with various materials
Evidence of thermal conductivity can be obtained by heating steel and silver spoons. Two metals have different energy transfer properties. At the end of the handle of each spoon you need to apply wax. Then both objects are heated from the same heat source on the other hand.
In a steel spoon, the wax melts much earlier, which indicates better thermal conductivity. Instead of wax, you can take a slice of frozen butter or margarine for the experience at home.
The second experiment proves the dependence of thermal conductivity on the color of the material. It will take dark and light teapots. Both vessels are heated to boiling water in them and the cooling time of each is detected.
According to the laws of physics, a dark kettle cools down longer. This proves that light materials heat less. Therefore, in hot weather, white panama hos are worn. After all, the sun's rays are attracted by black fabric.
In the cold, we wear warm scarves so that the face does not freeze. So, in a woolen mitt, the hand absolutely does not freeze in the freezer. This indicates a low thermal conductivity of the material.