Note: Descriptions are shown in the official language in which they were submitted.
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HEAT TRANSFER METHOD USING A SECONDARY FLUID
TECHNICAL FIELD
This invention is directed toward an improved
refrigerant system.
The invention is also directed toward an
improved air conditioning system incorporating the
improved refrigerant system.
The invention is further directed toward an
improved method for air conditioning a building.
BACKGROUND ART
Refrigerant systems have been using vapor/liquid
phase refrigerants, such as CFC refrigerants, for
heat transfer purposes. However these CFC
refrigerants are being phased out because of their
destructive effect on the ozone layer. The
replacement vapor/liquid phase refrigerants however,
such as HFC refrigerants, while efficient, are often
more costly, less reliable and more subject to
regulations with respect to the handling of it than
the CFC refrigerants. With the replacement
refrigerants operating in both a liquid and vapor
phase, a more expensive recovery method operated by a
certified refrigeration mechanic is required to
service the system. The replacement refrigerants,
such as HFC refrigerants, can also lead to liability
problems if the vapor phase is accidentally leaked to
the atmosphere during installation or servicing. Thus
it would be desirable if the amount of these
replacement refrigerants in refrigerant systems could
be reduced.
Air conditioning systems installed in buildings,
which systems incorporate refrigerant systems, often
have a heat exchanger mounted outside the building to
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remove heat taken out of the building air in the
summer time. The heat exchanger passes the heat to
outside air. This outside heat exchanger IS usually
quite far removed from the main part of the air
conditioning system. The heat exchanger can, for
example, be mounted on the roof of the building while
the remainder of the air conditioning system is
mounted in the basement of the building. The piping
to carry the refrigerant between the heat exchanger
and the remainder of the air conditioning system is
quite long and a large amount of expensive,
vapor/liquid phase refrigerant is needed. Again, it
would be desirable if the amount of refrigerant could
be reduced.
Migration of the refrigerant in an air
conditioning system with an outside heat exchanger is
also a major problem, particularly in the winter,
when using refrigerants with a vapor phase such as
HFC refrigerants. The outside heat exchanger is
normally not used in the winter and a three-way valve
is used to divert the refrigerant to the rest of the
system. However the vapor phase of the refrigerant
in the remainder of the air conditioning system leaks
past the three way valve into the piping leading to
and from the outside heat exchanger and "migrates" in
the piping to the heat exchanger. Because of the
length of the piping to the outside heat exchanger, a
significant amount of refrigerant can leak out of the
main part of the air conditioning system adding to
expense. As the refrigerant migrates, it carries
lubricating oil with it. The loss of this oil can
lead to the compressor or pumps in the system burning
out. Additional equipment and servicing is required
to avoid these lubrication problems thus making the
system more expensive.
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DISCLOSURE OF THE INVENTION
It is the purpose of the present invention to
provide an improved refrigeration system that is less
expensive to install and less expensive to service
and to operate than known systems. It is another
purpose of the present invention to provide an
improved refrigeration system that avoids, or at
least minimizes, the problems involved with using
vapor/liquid phase refrigerants, such as the
"migration" problem. It is another purpose of the
present invention to provide an improved air
conditioning system that incorporates the improved
refrigeration system with all its advantages.
In accordance with the present invention there
is provided an improved refrigeration system having
two different refrigerant circuits with a
vapor/liquid phase refrigerant in one circuit and
with a liquid phase refrigerant in the other circuit.
The one circuit with the vapor/liquid phase
refrigerant is a compact closed loop having an
evaporator therein for taking heat out of a medium,
such as building air, and a condenser for
transferring the heat from the refrigerant. The other
circuit, with the liquid phase refrigerant, is a
longer closed loop having the condenser therein so
that heat is transferred from the vapor/liquid phase
refrigerant to the liquid phase refrigerant and also
having heat exchanger means therein to get rid of
this heat.
When the refrigeration system is incorporated
into an air conditioning system for a building, the
evaporator in the one circuit is located in the main
air duct of the a/c system within the building to
remove humidity from the air. The heat exchanger
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means in the summer mode of operation of the a/c
system can be a heat exchanger located outside the
building, well removed from the condenser and the
first circuit. The heat exchanger means in the winter
mode of operation can be a heat exchanger in an air
inlet duct leading to the main air duct for heating
up makeup outside air being added to the air in the
building.
The use of two separate refrigerant circuits
reduces the amount of expensive vapor/liquid phase
refrigerants required. The first circuit is quite
compact with all the equipment in this circuit near
each other. Thus a relatively small amount of
vapor/liquid phase refrigerant is required. The
longer circuit, using a liquid phase refrigerant, can
be easily installed and serviced by a plumber. More
expensive servicing, employing a refrigerant recovery
method that requires a refrigeration mechanic, is not
needed for the liquid phase refrigerant. More
importantly, the use of a separate circuit filled
with liquid phase refrigerant avoids migration when
operating in the winter mode and the problems
attendant with migration.
The invention is particularly directed toward an
improved refrigerant system having a first
refrigerant circuit with an evaporator and a
condenser in the circuit and a first refrigerant
therein with first means for circulating the first
refrigerant through the circuit. The refrigerant
system has a second circuit with a heat exchanger and
the condenser in the second circuit and a second
different refrigerant therein with second means for
recirculating the second refrigerant through the
circuit. The first refrigerant picks up heat in the
evaporator and gives it up to the second refrigerant
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in the condenser. The second refrigerant picks up the
heat in the condenser and gives it up in the heat
exchanger.
The invention is also particularly directed
toward an air conditioning system for a building
having a main air duct with an evaporator in the duct
to extract humidity from building air passing through
the duct. The system has a first refrigerant circuit
connecting the evaporator to a condenser and a second
refrigerant circuit connecting the condenser to a
heat exchanger in the building. There is a first
refrigerant in the first circuit and first means in
the first circuit for recirculating the first
refrigerant through the first circuit. There is a
second refrigerant in the second circuit along with
means for circulating the second refrigerant through
the second circuit. The first refrigerant takes heat
from the building air in the evaporator and gives it
up to the second refrigerant in the condenser. The
second refrigerant gives up this heat to outside air
in the heat exchanger.
The invention is further directed toward a
method for operating an air conditioning system in a
building comprising the steps of taking heat out of
the air in the building while dehumidifying it with a
first refrigerant, transferring this heat from the
first refrigerant to a second refrigerant in a
condenser and transferring the heat out of the second
refrigerant to outside air through a heat exchanger.
BRIEF DESCRIPTION OF DRAWINGS
The invention will now be described in detail
having reference to the accompanying drawings in
which:
FIG. 1 is a schematic view of a simple
refrigerant system of the present invention;
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FIG. 2 is a schematic view of a more complex
refrigerant system of the present invention; and
FIG. 3 is a schematic of an air conditioning
system incorporating the refrigerant system shown in
Fig. 2.
DESCRIPTION OF PREFERRED EMBODIMENTS
The improved refrigerant system 1 of the present
invention as shown in Fig. 1 has a first circuit 3
that has an evaporator 5, a compressor 7, a condenser
g and an expansion valve 11 in series joined by
piping 13 in a closed loop. This first circuit 3 is
filled by a first refrigerant that operates in
vapor/fluid phases. The refrigerant enters the
evaporator 5 as a mix of vapor and liquid and picks
up heat therein leaving as vapor. The vapor is
compressed and heated by the compressor 7 and passes
to the condenser 9 where it gives up heat and becomes
liquid. The liquid refrigerant then passes to the
expansion valve 11 where it is partly vaporized and
the vapor/liquid mix passes to the evaporator 5 to
repeat the cycle.
The refrigerant system 1 includes a second
circuit 17. This second circuit 17 has the condenser
9, a first heat exchanger 23, and a pump 25, all
joined in series by piping 31. The second circuit 17
is filled with a second refrigerant that is in a
liquid phase.
The second circuit 17 is operated to dissipate
heat picked up by the second refrigerant from the
first refrigerant in the condenser 9. The first heat
exchanger 23 can be located far away from the
condenser 9 A more easily handled, less expensive,
refrigerant is used in the second circuit making the
second circuit, and thus the refrigerant system,
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easier to install and service. The first circuit can
be quite compact and requires relatively little of
the more efficient but more expensive vapor/liquid
phase refrigerant.
The above refrigerant system, slightly modified,
- is particularly suited for use in an air conditioning
system for buildings, particularly buildings housing
swimming pools. As shown in Figs. 2 and 3, the
modified refrigerant system 101 has a first circuit
103 with an evaporator 105, a compressor 107, a
condenser 109 and an expansion valve 111 all in
series connected in a closed loop by piping 113. This
circuit is the same as the circuit 3 in the system
shown in Fig. 1. The evaporator 105 is mounted within
a main air duct 115 in the air conditioning system in
a building for removing humidity from the building
air drawn through the duct 115 by a fan 117. Heat is
taken out of the air to remove humidity by
condensation. The first circuit 103 is filled with a
first refrigerant that operates in vapor/liquid
phases.
The air conditioning system includes a second
circuit 121 with two parallel branches 123, 125. The
first branch 123 has the condenser 109, a first heat
exchanger 127, a pump 131, a check valve 133 and a
second heat exchanger 129 all in series connected in
a closed loop by piping 135. The first heat exchanger
127 is an air preheater and is located in an air
inlet duct 137 connected to the main air duct 115
downstream from the evaporator 105. This first heat
exchanger 127 is used to heat outside air being added
to the system through the inlet duct 137. The outside
air is needed to make up for the loss of some of the
warm, humid, building air that is exhausted through
an air outlet duct 141 leading to the outside from
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the main duct 115 just upstream from the evaporator
105 As this air passes to the outside through duct
141, it passes through the second heat exchanger 129
giving up heat to the refrigerant in the line 135
just before the refrigerant returns to the condenser
109 .
Preferably, the first branch 123 employs a third
heat exchanger 145 located between the first heat
exchanger 127 and the pump 131. This third heat
exchanger 145 is an air reheater and is located in
the main air duct 115 just downstream from the
evaporator 105 and before the air inlet duct 137. The
purpose of the air reheater 145 is to reheat the air,
if needed, after it has been dehumidified. A bypass
line 147 can lead from the piping or line 135
upstream from the reheater 145 to bypass the air
reheater 145 if it is not needed. The bypass line
joins the main line 135 downstream from the reheater
and a diverter valve 149 can control the flow of the
refrigerant to the bypass line 147.
The second branch 125 of the second circuit 121
of the a/c system has a second line 155 branching off
from the main line 135 just after the main line 135
leaves the condenser 109. The second line 155 has a
fourth heat exchanger 157, a second pump 159 and a
second check valve 161 in series with the second line
155 rejoining the main line 135 just before it enters
the second heat exchanger 129. The fourth heat
exchanger 157 is used in the air conditioning system
to transfer heat to the outside air. This heat
exchanger 157 can be far removed from the main part
of the air conditioning system.
The first circuit 103 is quite compact and
employs a relatively small amount of expensive,
relatively efficient, vapor/liquid phase refrigerant.
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g
A suitable vapor/liquid phase refrigerant would be an
HFC refrigerant. The second circuit 121 can be quite
long compared to the first circuit. The refrigerant
in the second circuit is a liquid phase refrigerant
such as propylene glycol by way of example. This
refrigerant is always in the liquid phase and thus is
easier to handle, less expensive and avoids any
migration problems that may occur with a vapor/liquid
phase refrigerant.
In operation, the first refrigerant in the first
circuit 103 dehumidifies the warm, humid, building
air passing through the main air duct 115 by taking
heat out of the air in the evaporator 105. This heat
is then transferred from the first refrigerant to the
second refrigerant in the second circuit 121 in the
condenser 109.
In the winter time, in a heating mode, the first
branch 123 of the second circuit 121 alone would
operate, with first pump 131 operating and second
pump 159 stopped. The second check valve 161 would
prevent back flow through the second branch 125 while
the first pump 131 is operating. As the second
refrigerant is circulated in the first branch 123, it
picks up heat from the first refrigerant in the
condenser 109 and passes through the first heat
exchanger 127 to give up at least some of this heat
to reheat the makeup air entering the system through
the air inlet duct 137. This first heat exchanger 127
has the capacity to reject all of the heat picked up
by the second refrigerant if needed.
If needed, the diverter valve 149 can be
operated to direct the second refrigerant through the
air reheater 145 to heat up the building air in the
main duct 115 which has been cooled during
dehumidification. If air reheating is not needed, the
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diverter valve 149 can be operated to bypass the air
reheater 145. The second refrigerant then passes
through the second heat exchanger 129 to be reheated
to around room temperature by the building air being
exhausted from the system through the air outlet duct
141 The first pump 131 keeps the second refrigerant
recirculating through the first branch 123 while the
second branch 125 is passive. However because the
second refrigerant is in the liquid phase, migration
is not a similar problem as when using a vapor/liquid
phase refrigerant.
In the summer time, in a cooling mode, the first
pump 131 is stopped and the second pump 159 is
started to move the second refrigerant through the
second branch 125. In the second branch 125 the
second refrigerant picks up the heat from the primary
refrigerant in the condenser 109 and gives it up to
the outside air in the fourth heat exchanger 157. The
fourth heat exchanger 157 is sized so that it can get
rid of all the heat taken out of the building air.
The second refrigerant is recirculated by the second
pump 159 through the second heat exchanger 129 to
give up more heat to the exhaust air and then back to
the condenser 109. The first check valve 133 in the
first branch 123 prevents back flow through the first
branch 123 while the second pump 159 is operating.
It is within the ambit of the present invention
to cover any obvious modifications of the preferred
embodiments described herein, provided such
modifications fall within the scope of the appended
claims. For example, it is conceivable to eliminate
the two pumps 131 and 159 and their check valves 133
and 161 respectively and replace them by a three-way
valve connected to lines 135 and 155 and also to the
second heat exchanger 129. A single pump would then
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be connected in the main 135 between the second heat
exchanger 129 and the condenser lO9.
