ВУЗ:
Составители:
Рубрика:
48
Embedded pipes and cables
Low-temperature hot-water heating pipes or electric heating cables are
buried in concrete walls, floors or ceilings to provide a large low-temperature
surface that is maintained at a few degrees above room air temperature. Floor-
to-ceiling air temperature gradients tend to be less than those obtained with
more concentrated forms of heat emission and a uniform distribution of comfort
is produced.
Soft copper pipes are laid in position on the concrete floor slab and held
by clips, and the ends are connected to header pipes in service ducts. Joints are
avoided for the underfloor sections. Steel or plastic pipes may be used in some
situations. Thermal expansion and contraction of the pipework must be accom-
modated and the floor surface temperature is limited to avoid damage to the
structure, surface finishes or occupants. This is done by enclosing the pipe in a
hard asbestos sleeve on water pipes operating at 85 °C or by controlling water
temperature to 45 °C with a mixing valve system. Pipes are buried in the floor
screed. Heating elements are evenly distributed to provide uniform radiation
and convection to the occupants.
Warm air
Recirculated room air is heated either directly or indirectly by the energy
source. Direct firing of combustion gases into the air is permissible only in
large well-ventilated factory premises. All other applications require a fuel-to-
air heat exchanger where the combustion products are enclosed in a sheet metal
passageway. Room air is passed over the outside of this heating surface.
Heated air is passed through ducts to the occupied space. It is diffused
into the room through a grille, which mixes it with room air convection currents
and avoids draughts. Each grille has a damper to regulate the air flow. Extract
grilles and ductwork return the air to the heater. Care is needed not to extract air
directly from kitchens and bathrooms, as this would lead to odours and conden-
sation in living areas.
The main advantage of warm-air systems is quick heating up and re-
sponse to thermostatic control. A source of radiant heat is needed in the sitting
room to complement the otherwise purely convective heating. Stub ducts are
used to connect the heater to the supply and recirculation grilles.
Страницы
- « первая
- ‹ предыдущая
- …
- 46
- 47
- 48
- 49
- 50
- …
- следующая ›
- последняя »
