Pumps – Motor driven – Fluid motor
Patent
1998-08-24
2000-10-03
Walberg, Teresa
Pumps
Motor driven
Fluid motor
417391, 417 46, 417342, F04B 1700, F04B 3500
Patent
active
06126413&
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an apparatus for use in a liquid circulation system, said system comprising a primary and a secondary liquid circulation circuit defining a primary forward flow, a primary return flow, a secondary forward flow and a secondary return flow.
BACKGROUND ART
In such systems, a need can arise to be able to operate with different pressures in the primary and secondary liquid circulation circuits, respectively, this normally being achieved by leading the primary liquid circulation circuit through a heat exchanger, and leading the secondary liquid circulation circuit through the heat exchanger separate from the primary circulation circuit by means of a pump. In addition to the possibility of operating with different pressures in the primary and secondary circuits, this arrangement also provides protection against liquid from the primary circulation circuit flowing out uncontrollably caused by a possible leak in the secondary circulatory circuit; this may be called for e.g. in district heating systems in order to protect against water damage. The heat exchanger will, however, introduce an undesired loss of heat, and will normally make it necessary to circulate the liquid in the secondary circulatory circuit by means of a circulation pump.
DISCLOSURE OF THE INVENTION
It is the object of the present invention to provide an apparatus, with which the disadvantages of the known separating systems based upon the use of heat exchangers described above are avoided, while at the same time making it possible to maintain different pressures in the primary and secondary liquid circulation circuits, respectively.
This object is achieved with an apparatus of the kind set forth mentioned above, according to the present invention exhibiting the arrangements of two positively interconnected displacement machines, one of which receives the primary forward flow and which delivers the secondary forward flow and the other of which receives the secondary return flow and delivers the primary return flow together with a flow equalization means whereby the volumetric effects of the displacement machines are attuned to each other in a manner to ensure that the volume flows in the primary forward flow, the secondary forward flow, the secondary return flow and the primary return flow are substantially equal.
By arranging the apparatus as set forth in claim 1 it is possible to have the same liquid circulate from primary forward flow to secondary forward flow, to secondary return flow and to primary return flow, without the pressure conditions in these flows necessarily being equal, because a pressure difference between these two liquid circulation circuits is exploited to supply power to one of the displacement machines, this machine then driving the other machine to pump the circulated liquid from the second to the first of these liquid circulation circuits whilst maintaining substantially equal flow volumes to and from the two circuits (primary and secondary, respectively) and without using a separate circulation pump for the secondary circulatory circuit, because the pressure difference between the primary forward flow and the primary return flow is utilized to create a pressure difference between the secondary forward flow and the secondary return flow.
The arrangement where the displacement machines act as a pump and a motor with the pump having a greater volumetric effect which is reduced by a pressure-controlled bypass means. This provides for an active balancing of the volume flows in the apparatus simultaneously with a control of the pressure on one side of the pump (delivery/inlet).
In especially preferred embodiments of the apparatus, in which the displacement machines are in the form of piston-cylinder units. By arranging these piston-cylinder units as two cylinders placed in a coaxial extension of each other the advantage is achieved that the seal between each piston and the associated cylinder solely has to withstand the prevailing differential pressure between a primary forw
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Fastovsky Leonid
T. Smedegaard A/S
Walberg Teresa
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