Local Heating Systems

Date: 2015-10-07; view: 692.

READING TASK: Text 3

Adjectives

Verbs and verbal phrases

Nouns and noun phrases

27. Answer the following question and read the text below to check your answer.

What was the earliest type of local heating system?

Local heating is in common use in many countries. Such heating comes from fireplaces, or room heaters.

The earliest type of local heating system was the open fire within an enclosure, such as a cave or a tent. Such a fire is not satisfactory because the area heated can accumulate smoke.

If a fireplace is put at one side of a room and provided with a chimney, the smoke and combustion gases will pass up the chimney. The chimney provides a draught by which the air enters the front of the fireplace and passes up the chimney to aid the burning of the fuel. However, this draught reduces the energy efficiency of a fireplace.

Some room heaters burn gas to produce heat. These can be placed in a corner of the room and used with a fan to circulate the heated air. Such heaters should not be used without adequate ventilation to the outside because combustion gases can be harmful to the occupants of the room. Other room heaters burn paraffin and must also be vented.

Electric room heaters pass an electric current through a series of wires. These wires resist the electricity and become red hot. Such electric heaters give off heat by radiation and convection.

Most local sources of heat are relatively hot, compared with steam and hot-water radiators. For this reason they produce a larger proportion of radiant heat. When such large amounts of radiant heat are used, the temperature of the air in the room needs not become so hot. For example, a resistance-type electric heater called a quartz heater warms anyone in the path of its heat rays. But the heat rays do not significantly warm the air through which they travel.