Note: Descriptions are shown in the official language in which they were submitted.
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SUCTION COMPRESSOR TEMPERATURE REGULATOR DEVICE FOR
TRANSCRITICAL AND SUBCRITICAL R-744 COMPRESSORS
CROSS REFERENCE TO RELATED APPLICATION
Benefit of U.S. Provisional Application for Patent Serial No. 61/457,817 filed
on
June 10, 2011, is hereby claimed.
FIELD OF THE INVENTION
The present invention concerns refrigeration systems and methods, and more
particularly a suction compressor temperature regulator device for
transcritical
and subcritical R-744 compressors in R-744 refrigeration systems.
BACKGROUND OF THE INVENTION
Refrigeration systems are commonly used in supermarkets to refrigerate or to
maintain in frozen state perishable products, such as foodstuff.
Presently the R-744 subcritical refrigeration systems are defrosted
electrically
for the low temperature applications and by air defrost for the medium
temperature applications.
Furthermore, the suction temperature of R-744 compressors (subcritical or
transcritical) is required to be maintained at a level at least 36 F higher
than the
evaporating temperature in order to avoid oil foaming and to achieve reliable
and stable operation. This is extremely difficult to achieve by the habitual
methods used in Freon TM systems. The most common method used is suction
to liquid heat exchanger. However in the case of R-744 system the liquid
temperature is very low (around 20 F) and is inappropriate for use in such
heat
exchanger. It would be also difficult to regulate the liquid flow rate through
the
heat exchanger in order to achieve stable suction temperature at the required
level.
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Accordingly, it would be desirable to have an improved suction compressor
temperature regulator device for transcritical and subcritical R-744
compressors
for refrigeration systems.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved suction
compressor temperature regulator device for transcritical and subcritical R-
744
compressors for refrigeration systems.
An advantage of the present invention is that the suction compressor
temperature regulator device is simple and allows the corresponding
compressor(s) to substantially remain within efficient operating conditions,
as
possible, by controlling the temperature of the R-744 fluid reaching the
compressor(s). The heating mechanism of the device is typically regulated by a
temperature sensor sensing the temperature of the R-744 fluid located between
the heating mechanism and the compressor(s).
According to an aspect of the present invention, there is provided a suction
compressor temperature regulator device for use with at least one compressor
of a R-744 refrigeration system, said device comprising:
- a heating mechanism located upstream of the at least one compressor
of the refrigeration system, in a suction line of the at least one
compressor for locally controlling the temperature of a R-744 fluid of the
refrigeration system.
In one embodiment, the heating mechanism is in a form of a heat exchanger
connected to the suction line and using a heating fluid, wherein heat from the
heating fluid is transferrable to the R-744 fluid at the heat exchanger.
Conveniently, the heating mechanism includes a heating fluid circuit with
heating fluid modulating valve regulating a rate of heating fluid circulating
through the heat exchanger.
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Typically, the modulating valve is controlled by a temperature of the R-744
fluid
flowing in the suction line between the heat exchanger and the at least one
compressor.
Preferably, the heating fluid circuit includes a pressure regulating valve
located
downstream of the modulating valve and upstream of the heat exchanger.
In one embodiment, the at least one compressor is a transcritical compressor,
the suction line is a transcritical suction line, the heat exchanger is a
transcritical
heat exchanger, and the heating fluid modulating valve is a transcritical
heating
fluid modulating valve; the heating fluid circuit of the device further
including a
subcritical heating fluid modulating valve regulating a rate of heating fluid
circulating through a subcritical heat exchanger connected to a subcritical
suction line of at least one subcritical compressor for transferring heat to
the
R-744 fluid thereat.
Conveniently, the subcritical modulating valve is controlled by a temperature
of
the R-744 fluid flowing in the subcritical suction line between the
subcritical heat
exchanger and the at least one subcritical compressor.
Typically, the pressure regulating valve is located downstream of the
transcritical and subcritical modulating valves and upstream of the
transcritical
and subcritical heat exchangers.
In one embodiment, the heating fluid circuit is part of a heat reclaim circuit
of the
refrigeration system.
Conveniently, the heating fluid reaches the heat exchanger before reaching a
heat recuperator of the heat reclaim circuit.
Typically, the heat recuperator is located between the at least one compressor
and a gas cooler of the refrigeration system such that heat from the
compressed
R-744 fluid is transferred to the heating fluid of the heat reclaim circuit.
In one embodiment, the heating mechanism is in a form of an electrical heating
device located at the suction line for transferring heat to the R-744 fluid
thereat.
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According to an aspect of the present invention, there is provided a R-744
refrigeration system having at least one compressor and a suction compressor
temperature regulator device as claimed in claim 1 for use therewith.
Other objects and advantages of the present invention will become apparent
from a careful reading of the detailed description provided herein, with
appropriate reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Further aspects and advantages of the present invention will become better
understood with reference to the description, provided for purposes of
illustration only, in association with the following figure, wherein:
Figure 1 is a schematic diagram of a suction compressor temperature regulator
device for transcritical and subcritical R-744 compressors in R-744
refrigeration
systems, in accordance with an embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
In Figure 1, there is shown a simplified R-744 transcritical refrigeration
system
101 with a heat reclaim capabilities using a glycol solution as heat transfer
fluid,
incorporating an embodiment of a suction compressor temperature regulator
device 100 for transcritical and subcritical R-744 compressors in accordance
with the present invention.
In the suction line 1' of the transcritical compressors 1 of the refrigeration
system 101, the suction compressor temperature regulator device 100 includes
a heating mechanism that is preferably in the form of a heat exchanger 4 that
is
connected through conduit 9 and through modulating valve 14 to conduit 15,
and through conduit 8 to conduit 16 after the pressure regulating valve 10 of
a
heat reclaim circuit 11 having a typical recuperator 5 used to cool down the
hot
gas downstream of the compressors 1 (and provide comfort heating for the
building (not shown) at the same time, or the like) before the gas reaches the
gas cooler 6, thus allowing a warm glycol solution or the like to flow through
heat exchanger 4 at a controlled rate. The flow rate of the warm glycol
solution
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is typically regulated by modulating valve 14 and is controlled by the
temperature, via a temperature sensor (not shown) or the like, of the R-744
fluid
vapours between heat exchanger 4 and compressor 1.
Similarly, in the suction line 2' of the subcritical compressors 2 of the
5 refrigeration system 101, the suction compressor temperature regulator
device
100 includes the heating mechanism that is preferably in the form of a heat
exchanger 3 that is connected through conduit 7 and through modulating valve
13 to conduit 15, and through conduit 8 to conduit 16 after the pressure
regulating valve 10, thus allowing a warm glycol solution or the like to flow
through heat exchanger 3 at a controlled rate. The flow rate of the warm
glycol
solution is typically regulated by modulating valve 13 and is controlled by
the
temperature, via another temperature sensor (not shown) or the like, of the
R-744 fluid vapours between heat exchanger 3 and compressor 2.
Although not shown, it would be obvious to one skilled in the art that any
other
warm fluid solutions could be considered to be used with the heat exchangers 3
and 4, or even different types of heating mechanism for controlled local
heating,
such as electrical heating device 3' or the like, of the fluid just upstream
(in the
suction line) of the transcritical 1 and/or subcritical 2 compressors, and
preferably controlled by the temperature, via a temperature sensor (not shown)
or the like, of the R-744 fluid vapours inside the suction line 2' just
upstream of
the compressor 2, without departing from the scope of the present invention.
Although the present invention has been described with a certain degree of
particularity, it is to be understood that the disclosure has been made by way
of
example only and that the present invention is not limited to the features of
the
embodiments described and illustrated herein, but includes all variations and
modifications within the scope and spirit of the invention as hereinafter
claimed.
