Note: Descriptions are shown in the official language in which they were submitted.
CA 02363340 2001-11-19
CENTRAL HEATING FOR ROOMS TO BE HEATED
The invention pertains to a central heating system for rooms to be heated.
Known central heating systems generally have a heat source and a line system
for transporting a thermal medium to the individual rooms. As a rule, water is
used as
the thermal medium.
Depending on the complexity of the heating system, the line system is
composed of several subcircuits which extend, for instance, in individual
floors of a
multistory building. The subcircuits are supplied by vertical lines.
As a rule, a subcircuit of the line system consists of separate subcircuit
supply
and return lines, at least one line barner and several heating circuits
parallel to one
another connected to the subcircuit supply and return lines. A heating circuit
can have
only one heating element or several heating elements arranged in series and
connected
via supply and return lines to the supply and return lines of the subcircuit.
In the supply line, a line barner is arranged at the start of each subcircuit.
The
line barrier ensures a uniform distribution of water in the subcircuits. It is
intended
thereby to minimize irregular flow through the heating circuits and thus the
heating
elements because of, for instance, the long distance from the vertical supply
line or to
frictional losses due to pipe curvatures.
The regulation or control of desired room temperature is accomplished by way
of valves, specifically, temperature control valves, inserted into the heating
circuits.
The valve aperture and thus the volume flow of thermal medium flowing into the
heating circuits or heating elements is regulated by a pressure-sensitive
actuator. A
spring acts in the closing direction on the actuator.
Known central heating systems have the disadvantage that the installed circuit
barriers produce pressure gradients of varying magnitudes independently of the
flow
amount. The hysteresis of the valves increases or is displaced; in particular,
the
individual temperature settings of the individual rooms cannot be guaranteed.
If the central heating system is operating in the full load range, then there
is a
high flow velocity of the thermal medium in the line system. Associated with
this
high flow velocity, however, is a high pressure gradient at the circuit
barriers. This
has the consequence that a smaller differential pressure is present at the
valves for
controlling the flow of the thermal medium and thus a larger differential
force
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consisting of differential pressure and spring force acts in the closing
direction on the
actuator. The actuator is consequently pressed in the closing direction, so
that the
volume flow of thermal medium decreases. The premature valve closure induced
thereby has the result that the room temperature set/desired at the valves is
not
reached. In order to reach the desired room temperature nonetheless, manual
readjustment at the valves is required, which is linked to increased energy
consumption and increasing costs.
A similar phenomenon occurs in the partial load range of the central heating
unit. Because of the then prevailing low flow velocity of the thermal medium,
only a
small pressure gradient can be observed at the circuit barners. This has the
consequence that a higher pressure is present at the valves inserted into the
heating
circuits and therefore a lower differential pressure acts in the closing
direction on the
actuator. The actuator is thereby pressed less in the closing direction.
Because of the
elevated pressure, the valves close with a temporal offset, that is to say, at
higher room
temperatures. This is once again associated with elevated energy consumption
and
rising costs.
The present invention is based on the problem of refining a central heating
system for rooms to be heated such that energy savings are achieved by
avoiding the
aforementioned disadvantages with a simple design.
The present invention is based on the insight that, by setting a nearly
constant
pressure level in the line system of the heating system, particularly at the
valves, large
energy savings and a reduction of operating costs are possible.
According to the present invention, therefore, each heating circuit is
assigned a
flow limiter inserted in the supply or return line, independently of the
number of
heating elements in the heating circuit. A constant pressure level at the
valves can
thereby be guaranteed in a simple manner.
In order to ease the design of larger heating systems consisting of vertical
lines
and several subcircuits, the installation of flow limners is now done
exclusively in the
supply and return lines of the heating circuits. The circuit barners
previously utilized
are now unnecessary.
It is of no consequence whether a heating circuit contains only one heating
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element or several heating elements connected in series. The flow limiter in
the
heating circuit may be installed in the supply flow line, optionally upstream
or
downstream of a valve, as well as in the return flow line.
Depending on the embodiment of the invention, the flow limiter and the valve
may be designed as an integral structural unit.
The flow limiters are designed so that an equally large pressure gradient is
achieved at all flow limiters, independently of the existing pressure
conditions and, in
particular, independently of the size, number and construction of the heating
element
in a heating circuit.
The installation site of the flow limiters in the individual heating circuits
may
be consistent or different for all subcircuits of a heating system.
So that good maintenance of the system can be assured, the flow limners are
inserted interchangeably into the line network.
According to one embodiment of the invention, the flow limiters are laid out
such that an equally large pressure gradient is achieved at all flow limiters,
independently of the existing pressure conditions and, in particular,
independently of
the size, number and construction of the heating elements of a heating
circuit. This is
important when heating elements of different size, which are supplied
differently by
differing amounts of thermal medium per unit time, are employed. The flow
limner is
thus designed in regard to its size as a function of the size of the heating
element and
as a function of the pressure in the line network.
In accordance with one aspect of the present invention there is provided a
central heating system for rooms to be heated in one or more buildings with a
line
network with supply and return lines, at least one flow limiter arranged in
the line
network, a fluid as thermal medium in the line network, several heating
circuits each
connected to the line network via supply flow and return flow lines, each
having a
valve for regulation/control of room temperature and at least one heating
element,
wherein a flow limiter, which is inserted into supply flow or return flow
line, is
associated with each heating circuit.
In accordance with another aspect of the present invention there is provided a
central heating unit for rooms to be heated of one or more buildings with a
line
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network with outgoing and return lines, at least one flow limner arranged in
the line
network, a fluid as thermal medium in the line network, several heating
circuits, each
connected to the line network in parallel to one another via inflow and
outflow lines,
each having a valve for regulation/control of room temperature and at least
one
heating element, wherein a flow limiter, which is inserted into inflow or
outflow line,
is associated with each heating circuit.
Additional characteristics and advantages may be deduced from the
description below of an embodiment of the present invention in conjunction
with the
drawing wherein:
Figure 1, a schematic circuit diagram of a central heating system according to
the invention in a building consisting of several floors.
Figure 1 schematically shows a building 2 that comprises a service room 4 in
the basement for accommodating the heat source 6 and three heated stories 8a-
8c,
namely ground floor 8a, first upper floor 8b and second upper floor 8c. Three
subcircuits 12a-12c which are part of a central heating unit 10 according to
the present
invention are installed in building 2. Subcircuit 12a extends in ground floor
8a,
subcircuit 12b in first upper floor 8b, and subcircuit 12c in second upper
floor 8c.
Subcircuits 12a-12c each have a supply flow line 18 and a return flow line 20
which run separately. Subcircuits 12a-12c are connected to heat source 6 via
vertical
lines 14 and 16, each also having a supply flow and a return flow.
In each heated story 8a-8c, three heating circuits 32-36 are connected to the
corresponding subcircuit 12a-12c. Every heating circuit 32-36 is connected via
an
inflow line 24 to outflow 18 of the associated subcircuit 12a-12c and via a
return flow
line 30 to return flow 20 of the associated subcircuit 12a-2c. While the first
two
heating circuits 32 and 34 each have one heating element 22, two heating
elements 22
are arranged in series in the third illustrated heating circuit 36. The
diameters of
supply flow line 18 and return flow lint 20 of a subcircuit 12a-12c are
identical.
A thermostat valve 28 for regulating the room temperature is inserted in the
supply flow line 24 of each heating circuit 32-36.
A flow limner 26 is installed in supply flow line 24 or return flow line 30 of
each heating circuit 32. The installation site of flow limiter 26 in supply
line 24 or
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return line 30 of each heating circuit 32-36 is identical inside a given
subcircuit 12a-
12c, but the installation site differs for each individual one of the three
subcircuits
12a-12c. In subcircuit 12a, flow limiter 26 is downstream of the thermostat
valve 28
in supply line 24 of each heating circuit 32-36, and in subcircuit 12b, flow
limner 26
is upstream of thermostat valve 28 in supply line 24 of each heating circuit
32-36. In
subcircuit 12c, flow limiter 26 is inserted in return line 30 of each heating
circuit 32-
36 and thus downstream-of thermostat valve 28 and the heating element 22 or
heating
elements 22.
In thermostat valves 28 that are opened in the majority of cases, for
instance,
differently high flow velocities of the thermal medium occur in central
heating system
10. By providing flow limners 26 in supply flow line 24 or return flow line 30
of each
heating circuit 32-36, an essentially constant flow velocity in central
heating system
10 results. Because of the essentially constant flow velocities, pressure
fluctuations
inside the line system of central heating system 10 are avoided, in
particular, in supply
flow lines 24 and return flow lines 30 of each heating circuit 32, and thus at
temperature control valves 28. Consequently the hysteresis of the thermostat
valves
28 with respect to one another remains unchanged. This has the advantage that
the
room temperature is more precisely regulated and thus manual resetting of the
room
temperature is no longer necessary; consequently energy savings are achieved.
The present invention is characterized in that considerable energy can be
saved
by the central installation of flow limiters in supply flow line 24,
optionally upstream
or downstream of thermostat valve 28, or in return flow line 30 of each
heating circuit
32.
Although a preferred embodiment if the present invention has been described,
those of skill in the art will appreciate that variations and modifications
may be made
without departing from the spirit and scope thereof as defined by the appended
claims.
List of reference numerals
2 Building
4 Service area
6 Heat source
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8a-8c Floors
Central heating system
12a-12c Subcircuits
14 Vertical line supply
5 16 Vertical line return
18 Supply line of a subcircuit
Return line of a subcircuit
22 Heating element
24 supply flow line of a heating
circuit
10 26 Flow limiter
28 Thermostat/temperature control
valve
Return flow line of a heating
circuit
32 First heating circuit
34 Second heating circuit
15 36 Third heating circuit
