85 C ( 185 F), and the second heater gets steam at
about 2. 4 kg/cm2 abs (34.1 psi abs), whereby the
temperature of the circulating water may be further increased to about 100 C (212 F).
If a still higher temperature is required the
circulating water may be passed through a third
heater receiving steam from the 8-15 kg/cm2 steam
system and in which the water may be heated to
115 C (23~ F). For the greater part of the year,
in fact for all but about 1,000 hours, heating in
the first heater only is necessary. The temperature
of the water is regulated primarily by using one
or two heaters and, if necessary, by partly bypassing one of the heaters on the water side. At part
-- Connected load in fO' /real/hour.
---- Annual sales of heat in fOg /real.
'0·0 , - -
, -, IJ V
load on the turbine the pressure at the tap-off may
not be sufficient to give the desired temperature.
In such case this pressure may be increased by
throttling the flow of steam to the last stages of
the turbine by means of a flap-valve installed as
indicated on the diagram.
The development of the district heating system
through the years will be apparent from Fig. 2,
which shows the connected load and the annual
sales of heat.
The city of Copenhagen has about 753,000
inhabitants. Fig. 3 is a map of the city showing
the extent of the district heating' system. Heating
mains and buildings served are shown in black.
The heating system extends about 5 km ( 3. 1 miles)
from the generating stations. The principal data
are given in Table I.
Number of customers.
Total connected load.
Total sales, year 1957/58, steam
... 639,400 . lOG. kcal
Total sales, year 1957/58, warm water. 143,600 .106 kcal
Hours use at connected load. . . . . . .. .. 1,601 hours
Length of mains
Maximum size of mains.
103.2 km (64.1 miles)
. .. 400 mm (16")