U.S. patent application number 12/064857 was filed with the patent office on 2008-09-25 for refrigerant dehumidification system with variable condenser unloading.
Invention is credited to Alexander Lifson, Michael F. Taras.
Application Number | 20080229764 12/064857 |
Document ID | / |
Family ID | 37906424 |
Filed Date | 2008-09-25 |
United States Patent
Application |
20080229764 |
Kind Code |
A1 |
Taras; Michael F. ; et
al. |
September 25, 2008 |
Refrigerant Dehumidification System with Variable Condenser
Unloading
Abstract
A condenser in a refrigerant system is provided with a plurality
of refrigerant circuits, with at least one of the plurality of
circuits being equipped with a shut off device. A reheat coil is
also incorporated into the refrigerant system to provide enhanced
dehumidification functionality. By selectively shutting off at
least one of the active refrigerant circuits in the condenser, the
amount of heat rejected by the condenser as well as by the reheat
coil can be controlled shifting the heat load between the condenser
and reheat coil. In this manner, and in combination with operation
of the reheat cycle, incremental dehumidification and
cooling/heating can be provided and humidity and temperature can be
precisely controlled.
Inventors: |
Taras; Michael F.;
(Fayetteville, NY) ; Lifson; Alexander; (Manlius,
NY) |
Correspondence
Address: |
CARLSON, GASKEY & OLDS, P.C.
400 WEST MAPLE ROAD, SUITE 350
BIRMINGHAM
MI
48009
US
|
Family ID: |
37906424 |
Appl. No.: |
12/064857 |
Filed: |
September 15, 2005 |
PCT Filed: |
September 15, 2005 |
PCT NO: |
PCT/US2005/033695 |
371 Date: |
February 26, 2008 |
Current U.S.
Class: |
62/90 ;
62/498 |
Current CPC
Class: |
F25B 6/02 20130101; F25B
2400/0403 20130101; F24F 3/153 20130101 |
Class at
Publication: |
62/90 ;
62/498 |
International
Class: |
F25D 17/06 20060101
F25D017/06; F25B 1/00 20060101 F25B001/00 |
Claims
1. A refrigerant system comprising: a compressor, said compressor
delivering a refrigerant to a downstream condenser through a
discharge line, said discharge line communicating with a plurality
of parallel flow paths passing through said condenser, and at least
one of said plurality of flow paths having a shut-off device; a
line communicating downstream of said condenser to an expansion
device, and downstream of said expansion device to an evaporator,
and a line communicating from said evaporator back to said
compressor; and a reheat circuit incorporated into said refrigerant
system, said reheat circuit receiving a refrigerant, and passing
said received refrigerant through a reheat heat exchanger, and from
said reheat heat exchanger back into a main refrigerant circuit, an
air-moving device for moving air over said evaporator, and over
said reheat heat exchanger, and a control for selectively opening
said shutoff device to achieve desired control in combination with
said reheat circuit.
2. The refrigerant system as set forth in claim 1, wherein a bypass
line allows selective bypass of at least a portion of refrigerant
around said condenser, and said bypass line also includes a bypass
valve, with said control selectively controlling said bypass
valve.
3. The refrigerant system as set forth in claim 1, wherein said
reheat circuit taps refrigerant from a location downstream of said
condenser.
4. The refrigerant system as set forth in claim 1, wherein said
reheat circuit taps refrigerant from a location upstream of said
condenser.
5. The refrigerant system as set forth in claim 4, wherein said
discharge line from said compressor branches into said plurality of
parallel flow paths, and said reheat circuit taps refrigerant from
a location upstream of a branching point.
6. The refrigerant system as set forth in claim 1, wherein there
are at least three of said flow paths, and at least two of said at
least three flow paths having shut-off devices.
7. The refrigerant system as sot forth in claim 1, wherein said
control operating said shut-off device to block flow of refrigerant
through said at least one of said plurality of flow paths when less
cooling is desired.
8. The refrigerant system as set forth in claim 7, wherein said
control operates said shut-off device to block the flow of
refrigerant through said at least one of said plurality of flow
paths to achieve a desired amount of dehumidification, with lesser
cooling, when less cooling is desired.
9. The refrigerant system as set forth in claim 1, wherein said
control shuts said shut-off device to block flow of refrigerant
through at least one of said plurality of flow paths, while still
allowing flow through at least one other of said plurality of flow
paths to reduce the cooling load provided by refrigerant passing
through the condenser.
10. A method of controlling a refrigerant system comprising:
providing a compressor, said compressor delivering a compressed
refrigerant to a downstream condenser through a discharge line,
said discharge line communicating with a plurality of parallel flow
paths passing through said condenser, and at least one of said
plurality of flow paths having a shut off device; communicating
refrigerant downstream of said condenser to an expansion device,
and downstream or said expansion device to an evaporator, and
communicating refrigerant from said evaporator back to said
compressor; and a reheat circuit incorporated into said refrigerant
system, said reheat circuit receiving a refrigerant, and passing
said received refrigerant through a reheat heat exchanger, and from
said reheat heat exchanger back into a main refrigerant circuit, an
air-moving device moving air over said evaporator, and over said
reheat heat exchanger, and a control selectively opening said
shutoff device to achieve desired control in combination with said
reheat circuit.
11. The method as set forth in claim 10 wherein a bypass line
allows selective bypass of at least a portion of refrigerant around
said condenser, and said bypass line also includes a bypass valve,
with said control selectively controlling said bypass valve.
12. The method as set forth in claim 10, wherein said reheat
circuit taps refrigerant from a location downstream of said
condenser.
13. The method as set forth in claim 10, wherein said reheat
circuit taps refrigerant from a location upstream of said
condenser.
14. The method as set forth in claim 13, wherein said discharge
line from said compressor branches into said plurality of parallel
flow paths, and said reheat circuit taps refrigerant from a
location upstream of a branching point.
15. The method as set forth in claim 10, wherein there are at least
three of said flow paths, and at least two of said at least three
flow paths having shut off devices.
16. The method as set forth in claim 10, wherein said control
operating said shut-off valve device to block flow of refrigerant
through said at least one of said plurality of flow paths when less
cooling is desired.
17. The method as set forth in claim 10, wherein said control
operating said shut-off device to block flow of refrigerant through
said at least one of said plurality of flow paths when less cooling
is desired.
18. The method as set forth in claim 10, wherein said control
operates said shut-off device to block the flow of refrigerant
through said at least one of said plurality of flow paths to
achieve a desired amount of dehumidification, with lesser cooling,
when less cooling is desired.
19. The method as set forth in claim 10, wherein said control shuts
said shut-off device to block flow of refrigerant through at least
one of said plurality of flow paths, while still allowing flow
through at least one other of said plurality of flow paths to
reduce the cooling load provided by refrigerant passing through the
condenser.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to a refrigerant system incorporating
a reheat function and a condenser comprising a number of
refrigerant passages, with at least some of the passages being
selectively shut off to control the total heat rejection
distribution between the condenser (outdoor section) and reheat
coil (indoor section).
[0002] Refrigerant systems are utilized to control the temperature
and humidity of air in various indoor environments to be
conditioned. In a typical refrigerant system operating in the
cooling mode, a refrigerant is compressed in a compressor and
delivered to a condenser (or an outdoor heat exchanger in this
case). In the condenser, heat is exchanged between outside ambient
air and the refrigerant. From the condenser, the refrigerant is
passed to an expansion device, at which the refrigerant is expanded
to a lower pressure and temperature, and then to an evaporator (or
an indoor heat exchanger). In the evaporator, heat is exchanged
between the refrigerant and the indoor air, to condition the indoor
air. When the refrigerant system is operating, the evaporator cools
the air that is being supplied to the indoor environment. In
addition, as the temperature of the indoor air is lowered, moisture
usually is taken out of the air as well. In this manner, the
humidity level of the indoor air can also be controlled.
[0003] Another way of controlling an environment in the conditioned
space with a refrigerant system is the utilization of a reheat
coil. Typically, a reheat coil is provided in the path of air that
has been blown over the evaporator. The air passes over the reheat
coil to regain heat from a refrigerant that is at a temperature
higher than the temperature of air leaving the evaporator. The
reheat coil is thus able to raise the temperature of the air
leaving the evaporator. Hence, the air is dehumidified and
overcooled in the evaporator and then is reheated back to a
comfortable temperature level in the reheat coil.
[0004] Another option with known refrigerant systems is to use a
bypass line to reroute the refrigerant flow around the condenser.
In this manner, at least a portion of refrigerant may bypass the
condenser, which will lower its cooling potential as it approaches
the evaporator. The condenser bypass has been employed in the prior
art systems in combination with the reheat coil to control the
thermodynamic state of the refrigerant entering the reheat coil. On
the other hand, the condenser passages are typically sized to
handle the normal volume of refrigerant flowing through the
condenser, and how much refrigerant passes through each circuit
should be carefully managed at a wide spectrum of environmental and
operating conditions for proper system functionality and reliable
operation. Further, pulsating flow in the bypass line (in case
pulse width modulation method is used) may introduce some undesired
instabilities within the refrigerant circuit that may be difficult
to control. Consequently, the condenser bypass alone has a
restricted range of applications limited by efficiency, head
pressure control, oil holdup and other considerations.
[0005] Thus, there is a need in a refrigerant dehumidification
system that would have a variable reheat capacity and provide
reliable and efficient operation without further complexity and at
marginal cost.
SUMMARY OF THE INVENTION
[0006] In a disclosed embodiment of this invention, a condenser,
within a refrigerant system incorporating a reheat function, has a
plurality of refrigerant passages with at least some of these
passages being provided with shut off devices. Thus, as fewer
passages are open to allow refrigerant flow through the main
condenser, less heat is rejected by the condenser and more reheat
capacity is provided at the reheat coil.
[0007] This increase in the reheat capacity can be accomplished by
selectively turning off some of the condenser circuits. Thus, the
condenser size and condenser load can be reduced in stages in
accordance with application requirements and design
constraints.
[0008] Another side benefit of this proposed concept is that a head
pressure control is naturally provided by varying the number of
active refrigerant circuits in the condenser, regardless of the
mode of operation. Obviously, the pressure drop through the
condenser has to be maintained within design guidelines, and in one
disclosed embodiment, a bypass line around the condenser may be
included for additional operational flexibility. The bypass line
could also have an application in combination with the reheat
cycle.
[0009] These and other features of the present invention can be
best understood from the following specification and drawings, the
following of which is a brief description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 shows a first schematic incorporating the present
invention.
[0011] FIG. 2 shows an alternate schematic.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0012] A refrigerant system 20 is illustrated in FIG. 1 including a
compressor 22 compressing refrigerant and delivering it to a
downstream condenser 24. An expansion device 26 is located
downstream of the condenser 24, and an evaporator 28 is positioned
downstream of the expansion device 26. The refrigerant returns from
the evaporator 28 to the compressor 22. As shown, a number of
parallel refrigerant passages (or circuits) 30, 32 and 34 pass
through the condenser 24. Shutoff devices such as valves 36 are
placed on two of the three circuits 32 and 34. A control operates
to open or close the shutoff valves 36, as will be explained below.
A bypass line 38 includes a valve 40 for selectively allowing
bypass at least a portion of refrigerant around the condenser
24.
[0013] A three-way valve 42 selectively routes refrigerant into a
line 44 and through a reheat heat exchanger 46. A fan 48 pulls air
over the evaporator 28 and then over the reheat heat exchanger 46.
Also, a check valve 140 is placed downstream of the reheat heat
exchanger 46 within the reheat loop.
[0014] As is known, the reheat loop is utilized when
dehumidification is desired. Essentially, the evaporator is
controlled to cool air to a temperature level lower than the
temperature that would be desired by an occupant of a space to be
conditioned by the refrigerant system 20 in order to remove
sufficient amount of moisture from the air stream. This cold and
dehumidified air then passes over the reheat coil 46, which will be
at a higher temperature (while in operation) than the air exiting
the evaporator 28. The reheat coil thus reheats the air up toward
the temperature desired by the occupant of the space to be
conditioned. The control of the reheat coil is known.
[0015] At times, it may be desirable to vary the amount of cooling
and/or dehumidification being provided. By limiting the number of
refrigerant circuits passing through the condenser 24, the amount
of heat rejected by the main condenser 24 and reheat provided by
the reheat coil 46 can be controlled. In the refrigerant system 20,
the incremental steps of reheat control can be achieved by either
shutting the valves 36, opening the valve 40, or both. In this
manner, the amount of heat load placed on the condenser as well as
the amount of refrigerant circulating through the condenser can be
varied, and the total heat rejected can be shifted between the main
condenser 24 and the reheat coil 46. By decreasing the amount of
heat exchanged in the condenser 24, the amount of cooling and
dehumidification achieved in the evaporator 28 can also be
adjusted.
[0016] For instance, if a higher air temperature is desired
downstream of the reheat heat exchanger 46 then some of the
refrigerant circuits 36 passing through the main condenser 24 will
be shut off or taken off-line. As a result, a smaller heat transfer
surface will be utilized in the condenser 24, and the pressure
differential of the refrigerant circulating through the remaining
circuits 30 may simultaneously increase. Consequently, although
condensation temperature (or discharge pressure) will rise, the net
effect would be such that heat rejected by the main condenser 24
will diminish. Since the temperature difference in the reheat coil
46 will increase and the refrigerant leaving the main condenser 24
may have higher enthalpy, the heat rejected in the reheat coil 46
will rise providing the desired higher temperature of the air
supplied to the conditioned environment. Further, the valve 40
could be used in combination with the valves 36 to assure precise
control as well as safe and reliable operation. Finally, the number
of circuits incorporating shutoff devices 36 may vary and is
determined by the equipment type and practical considerations.
[0017] Thus, a control in this invention operates the valves 36 and
40 in combination with the valve 42 to achieve desired levels of
cooling and dehumidification, while the refrigerant system 20 is
operating in the reheat mode.
[0018] A worker of ordinary skill in the art would recognize under
what conditions these several valves mentioned above should be
opened and/or closed. Another side benefit of this invention is
that a head pressure control is naturally provided by varying the
number of active refrigerant circuits in the main condenser,
regardless of the mode of operation.
[0019] FIG. 2 shows another system 50 wherein a reheat line 52 taps
refrigerant from a three-way valve 54, and returns the refrigerant
through a reheat heat exchanger 46 and a check valve 140 back to a
main refrigerant circuit upstream of a condenser 56 (as well as
upstream of a pair of refrigerant circuits 58 and 60 passing
through the condenser 56). A shut off valve 62 is shown only on the
circuit 60. Once again, a number of circuits incorporating valves
62 may vary.
[0020] This refrigerant system is controlled similarly to the
refrigerant system 20. Essentially, the valve 62 is opened and
closed to change the heat load on the condenser 56 and consequently
on the reheat coil 46.
[0021] While two basic reheat concepts are shown in FIGS. 1 and 2,
a multitude of other system configurations can equally benefit from
this invention.
[0022] Although preferred embodiments of this invention have been
disclosed, a worker of ordinary skill in the art would recognize
that certain modifications would come within the scope of this
invention. For that reason, the following claims should be studied
to determine the true scope and content of this invention.
* * * * *