Principles of heating
Comfort. Human beings are warm-blooded animals. Their body has the relatively high average temperature of 98.6° F. (37° C). Food provides fuel for this body heat. When the temperature surrounding the body is extremely cold, the body loses too much heat. Clothing reduces the loss of heat. But for comfort in regions that are cold during the winter, indoor heating must be provided.
Most people feel comfortable in a room with a temperature of from 70° F. (21° C) to 78° F. (26° C). The humidity in a room also affects comfort. If two rooms have the same temperature but different humidity, most people will feel warmer in the room with the higher humidity. An indoor relative humidity of from 30 per cent to 60 per cent is the most comfortable for most people. The temperature in a home can be lower without sacrificing comfort for some people if moisture is added to the air with a device called a humidifier. However, adding the moisture may require more energy than simply raising the temperature.
Heat transfer. Heat is transferred in three important ways: conduction, convection, and radiation. Conduction is the heating of matter by bringing it in contact with a hot object. The heat passes directly from the hot object to the adjacent matter. This is much like the heat passing along an iron rod, one end of which is held in the hand while the other end is in a fire.
In natural convection, the hot object heats the surrounding air. This heated air rises because of its lighter weight The hot air, in turn, is replaced by cool air which, in turn, is heated and rises. In this way, a continuous current of warm air rises from near a hot object, just as hot air rises over a bonfire or a hot stove.
A hot object radiates heat in the form of waves much like radio and light waves. These waves can go through a vacuum or through dry air without heating it. The earth receives radiant heat from the sun.
1. Study the following words:
Crude caves, warm-blooded, humidity, moisture, humidifier, conduction, adjacent matter, iron rod, bonfire, light waves.
2. Complete the sentences with appropriate words from the text:
a) An indoor ….. …. of from 30 per cent to 60 per cent is the most comfortable for most people.
b) ……..is the heating of matter by bringing it in contact with a hot object.
c) ……. are used in many homes, office and industrial buildings, and schools today.
d) The ….. in a room also affects comfort.
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3.Insert necessary prepositions:
a) ….natural convection, the hot object heats the surrounding air.
b) This heated air rises because … its lighter weight.
c) Food provides fuel … this body heat.
d) Later on, these fireplaces were provided …. separate chimneys.
e) These waves can go through a vacuum or ….. dry air without heating it.
4. Ask the questions:
a) Conduction is the heating of matter by bringing it in contact with a hot object.
b) Human beings are warm-blooded animals.
c) The heat passes directly from the hot object to the adjacent matter.
d) However, adding the moisture may require more energy than simply raising the temperature.
e) These waves can go through a vacuum or through dry air without heating it.
5. Translate:
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