Heat conduction, convection and thermal radiation are two examples in life.

1, an example of heat conduction in life: put one end of a metal spoon into boiling water, and after a while, the other end in contact with boiling water will also heat up; When cooking, the iron pot uses the heat conduction of iron to cook.

2. Examples of convection in life: cold and hot air convection forms wind; Hot air near the radiator surface flows upward.

3. Examples of thermal radiation in life: when burning firewood in the stove, sitting on the side will feel burning; Solar radiation raises the temperature.

Matters needing attention

1, thermal radiation is a way of heat transfer, which does not contain chemicals and will not cause harm to people;

2. Strong convective weather, you can't hide under a tree or stay in an open place when you are outdoors;

3. Heat transfer depends on whether the object is a good conductor.

Extended data:

fundamental form

There are three basic forms: natural convection, forced convection and turbulence, among which turbulence has the highest heat transfer rate.

Natural convection is the uneven pressure or density in the fluid caused by uneven temperature, which leads to circular flow. For example, when boiling water, the water circulates up and down. Household refrigerators generally rely on natural convection to cool things, so don't fill the refrigerator too full to affect convection.

Due to the uneven heat obtained by various parts of the earth's surface from solar radiation, the warm air mass at the equator keeps rising and flowing to the poles, and the cooler air keeps flowing to the equator. This thermal convection is one of the reasons for the formation of natural wind.

As for electric fans, indirect cooling refrigerators, generators and liquid pump cooling devices of various engines, forced convection of gas or liquid is used. Controlling convection between gas and liquid is the main means to increase or decrease heat transfer.

Opening doors and windows in summer can promote indoor and outdoor air convection and achieve the purpose of heat dissipation; Closing doors and windows in winter can avoid indoor and outdoor air convection and achieve the purpose of keeping warm. Sometimes hanging curtains can prevent convective airflow from reaching the window, further reducing indoor heat loss. ?

influencing factor

The main factors affecting thermal convection are: temperature difference, thermal conductivity, thickness and cross-sectional area of heat-conducting objects.

The greater the thermal conductivity and the smaller the thickness, the more heat is conducted. The larger the area of ventilation holes in the fire, the faster the thermal convection speed; The higher the ventilation hole, the faster the thermal convection speed. Thermal convection is an important way of heat transfer and the most important factor affecting the development of initial fire.

Baidu encyclopedia-thermal convection