How It Works: Science and Technology - Vol. 8

By Wendy Horobin | Go to book overview

Heating and Ventilation Systems

The archaeological
remains of a Roman
hypocaust. The system of
supporting brick columns
indicates that this was a
pillared hypocaust. Hot
gases from a furnace
would have passed below
this floor, warming the
room above.

Heating and ventilation systems enable humans to live comfortably in conditions of varying ambient temperature. Humans need to maintain a body temperature of about 98°F (37°C) and begin to feel uncomfortable when exposed to temperatures that fall below 70°F (21°C). Warm clothing can be worn to insulate the body, but this solution tends to be heavy and cumbersome. The body may also experience discomfort when exposed to excessive heat. Therefore, various methods have been developed to heat, cool, and ventilate interiors.


Heating systems

Heating systems can be divided into those that heat the area in the immediate vicinity of the heat source, or direct heating, and those where the heat source is remote from the rooms heated, or central heating. The earliest methods of heating were direct, consisting simply of burning a fuel, such as wood or turf, usually in the middle of a room, the smoke produced escaping through a hole in the roof. This method inevitably resulted in very smoky interiors, so chimneys were developed to carry the smoke away from the living space to the exterior of the building. In Europe, the first chimneys appeared during the 12 th century.

One problem with chimneys is that the heat tends to escape up the flue as combustion gases, making open fires an inefficient use of fuel. Fires also need a supply of air to burn, and in the case of open fires, this air is drawn from the room, resulting in drafts. An improvement on the open fire was the enclosed stove, first used in China around 600 B.C.E. In this system, the heat of the fire is absorbed by the stove walls, which then emit this heat to the surrounding room.


Central heating

The first central heating system was invented by the Romans and consisted of an elaborate form of underfloor heating called hypocausts. Two systems were devised that worked in similar ways. In the channeled hypocaust, a network of tunnels ran under the rooms to be heated, while in the pillared hypocaust the floors of the rooms were raised on a series of pillars, creating a hollow area underneath. In both cases, however, hot gases from a furnace ran through the spaces under the floor, warming the rooms above. As the Roman Empire declined, the system of hypocausts ceased to be used, and central heating was not reintroduced until 1,500 years later.

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How It Works: Science and Technology - Vol. 8
Table of contents

Table of contents

  • Title Page *
  • Contents *
  • Gold 1013
  • Governor 1017
  • Grass-Cutting Equipment 1018
  • Gravity 1020
  • Gun 1023
  • Gyrocompass 1028
  • Gyroscope 1030
  • Hair Treatment 1032
  • Halogen 1034
  • Hang Glider 1037
  • Head-Up Display 1039
  • Hearing 1041
  • Heart 1045
  • Heart Pacemaker 1048
  • Heart Surgery 1049
  • Heat Engine 1053
  • Heat Exchanger 1054
  • Heating and Ventilation Systems 1056
  • Heat Pump 1063
  • Helicopter 1065
  • Hi-Fi Systems 1071
  • High-Speed Photography 1077
  • Holography 1080
  • Hormone 1084
  • Horticulture 1088
  • Hosiery and Knitwear Manufacture 1090
  • Hurricane and Tornado 1094
  • Hydraulics 1100
  • Hydrocarbon 1105
  • Hydrodynamics 1109
  • Hydroelectric Power 1112
  • Hydrofoil 1116
  • Hydrogen 1118
  • Hydroponics 1120
  • Hygrometer 1123
  • Ignition System, Automobile 1124
  • Image Intensifier 1128
  • Immunology 1132
  • Induction 1138
  • Inertia 1142
  • Information Technology 1147
  • Ink 1151
  • Index i
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