Field of the Invention
[0001] The present invention relates to industrial refrigeration systems.
Background of the Invention
[0002] Prior art industrial refrigeration systems, e.g., for refrigerated warehouses, especially
ammonia based refrigeration systems, are highly compartmentalized. The evaporator
coils are often ceiling mounted in the refrigerated space or collected in a penthouse
on the roof of the refrigerated space, the condenser coils and fans are usually mounted
in a separate space on the roof of the building containing the refrigerated space,
and the compressor, receiver tank(s), oil separator tank(s), and other mechanical
systems are usually collected in a separate mechanical room away from public spaces.
Ammonia-based industrial refrigeration systems containing large quantities of ammonia
are highly regulated due to the toxicity of ammonia to humans, the impact of releases
caused by human error or mechanical integrity, and the threat of terrorism. Systems
containing more than 10,000 lbs of ammonia require EPA's Risk Management Plan (RMP)
and OSHA's Process Safety Management Plan and will likely result in inspections from
federal agencies. California has additional restrictions/requirements for systems
containing more than 500 lbs of ammonia. Any refrigeration system leak resulting in
the discharge of 100 lbs or more of ammonia must be reported to the EPA.
Description of the Drawings
[0003]
Figure 1 is a schematic of a refrigeration system according to an embodiment of the
invention.
Figure 2 is a blow-up of the upper left hand portion of Figure 1.
Figure 3 is a blow-up of the lower left hand portion of Figure 1.
Figure 4 is a blow-up of the lower right hand portion of Figure 1.
Figure 5 is a blow up of the upper right hand portion of Figure 1.
Figure 6 is a three dimensional perspective view of a combined evaporator module and
a prepackaged modular machine room according to an embodiment of the invention.
Figure 7 is a three dimensional perspective view of a combined evaporator module and
a prepackaged modular machine room according to another embodiment of the invention.
Figure 8 is a three dimensional perspective view of the inside of a pre-packaged modular
machine room and condenser unit according to an embodiment of the invention.
Figure 9 is a three dimensional perspective view of the inside of a pre-packaged modular
machine room and condenser unit according to another embodiment of the invention.
Figure 10 is a three dimensional perspective view of combined evaporator module and
a prepackaged modular machine room according to another embodiment of the invention.
Figure 11 shows three-dimensional perspective views of three different embodiments
of combined evaporator module and a prepackaged modular machine room, in which the
embodiment on the left includes a roof mounted air-cooled condenser system.
Figure 12 shows a three-dimensional cut-away view of the inside of a pre-packaged
modular machine room according to another embodiment of the invention.
Figure 13 shows a three-dimensional cut-away view of the inside of a combined penthouse
evaporator module and a prepackaged modular machine room.
Summary of the Invention
[0004] The present invention is a packaged, pumped liquid, recirculating refrigeration system
with charges of 10 lbs or less of refrigerant per ton of refrigeration capacity. The
present invention is a low charge packaged refrigeration system in which the compressor
and related components are situated in a pre-packaged modular machine room, and in
which the condenser is close coupled to the pre-packaged modular machine room. According
to an embodiment of the invention, the prior art large receiver vessels, which are
used to separate refrigerant vapor and refrigerant liquid coming off the evaporators
and to store backup refrigerant liquid, may be replaced with liquid-vapor separation
structure/device which is housed in the pre-packaged modular machine room. According
to one embodiment, the liquid-vapor separation structure/device may be a single or
dual phase cyclonic separator. According to another embodiment of the invention, the
standard economizer vessel (which collects liquid coming off the condenser) can also
optionally be replaced with a single or dual phase cyclonic separator, also housed
in the pre-packaged modular machine room. The evaporator coil tubes are preferably
formed with internal enhancements that improve the flow of the refrigerant liquid
through the tubes, enhance heat exchange and reduce refrigerant charge. According
to one embodiment, the condenser may be constructed of coil tubes preferably formed
with internal enhancements that improve the flow of the refrigerant vapor through
the tubes, enhance heat exchange and reduce refrigerant. According to a more preferred
embodiment, the evaporator tube enhancements and the condenser tube enhancements are
different from one-another. The specification of co-pending provisional application
serial no.
62/188,264 entitled "Internally Enhanced Tubes for Coil Products" is incorporated herein in
its entirety. According to an alternative embodiment, the condenser system may employ
microchannel heat exchanger technology. The condenser system may be of any type known
in the art for condensing refrigerant vapor into liquid refrigerant.
[0005] According to various embodiments, the system may be a liquid overfeed system, or
a direct expansion system, but a very low charge or "critically charged" system is
most preferred with an overfeed rate (the ratio of liquid refrigerant mass flow rate
entering the evaporator versus the mass flow rate of vapor required to produce the
cooling effect) of 1.05: 1.0 to 1.8:1.0, and a preferred overfeed rate of 1.2:1. In
order to maintain such a low overfeed rate, capacitance sensors, such as those described
in
U.S. Patent Application Serial Nos. 14/221,694 and
14/705,781 the entirety of each of which is incorporated herein by reference, may be provided
at various points in the system to determine the relative amounts of liquid and vapor
so that the system may be adjusted accordingly. Such sensors are preferably located
at the inlet to the liquid-vapor separation device and/or at the outlet of the evaporator,
and/or someplace in the refrigerant line between the outlet of the evaporator and
the liquid-vapor separation device and/or at the inlet to the compressor and/or someplace
in the refrigerant line between the vapor outlet of the liquid-vapor separation device
and the compressor.
[0006] Additionally, the condenser system and the machine room are preferably close-coupled
to the evaporators. In the case of a penthouse evaporator arrangement, in which evaporators
are situated in a "penthouse" room above the refrigerated space, the machine room
is preferably connected to a pre-fabricated penthouse evaporator module. In the case
of ceiling mounted evaporators in the refrigerated space, the integrated condenser
system and modular machine room are mounted on a floor or rooftop directly above the
evaporator units (a so-called "split system").
[0007] The combination of features as described herein provides a very low charge refrigeration
system compared to the prior art. Specifically, the present invention is configured
to require less than six pounds of ammonia per ton of refrigeration capacity. According
to a preferred embodiment, the present invention can require less than four pounds
of ammonia per ton of refrigeration. And according to most preferred embodiments,
the present invention can operate efficiently with less than two pound per ton of
refrigeration capacity. By comparison, prior art "stick-built" systems require 15-25
pounds of ammonia per ton of refrigeration, and prior art low charge systems require
approximately 10 pounds per ton of refrigeration. Thus, for a 50 ton refrigeration
system, prior art stick built systems require 750-1,250 pounds of ammonia, prior art
low charge systems require approximately 500 pounds of ammonia, and the present invention
requires less than 300 pounds of ammonia, and preferably less than 200 pounds of ammonia,
and more preferably less than 100 pounds of ammonia, the report threshold for the
EPA (assuming all of the ammonia in the system were to leak out). Indeed according
to a 50 ton refrigeration system of the present invention, the entire amount of ammonia
in the system could be discharged into the surrounding area without significant damage
or harm to humans or the environment.
Detailed Description of the Invention
[0008] Figure 1 is a process and instrumentation diagram for a low charge packaged refrigeration
system according to an embodiment of the invention. Blow-ups of the four quadrants
of Figure 1 are presented in Figures 2 through 5, respectively. The system includes
evaporators 2a and 2b, including evaporator coils 4a and 4b, respectively, condenser
8, compressor 10, expansion devices 11a and 11b (which may be provided in the form
of
valves, metering orifices or other expansion devices), pump 16, liquid-vapor separation device 12, and economizer 14. According to one
embodiment, liquid-vapor separation device 12 may be a recirculator vessel. According
to other embodiments, liquid-vapor separation device 12 and economizer 14 may one
or both provided in the form of single or dual phase cyclonic separators. The foregoing
elements may be connected using standard refrigerant tubing in the manner shown in
Figures 1-5. As used herein, the term "connected to" or "connected via" means connected
directly or indirectly, unless otherwise stated. Optional defrost system 18 includes
glycol tank 20, glycol pump 22, glycol condenser coils 24 and glycol coils 6a and
6b, also connected to one-another and the other element of the system using refrigerant
tubing according to the arrangement shown in Figure 1. According to other optional
alternative embodiments, hot gas or electric defrost systems may be provided. An evaporator
feed pump/recirculator 16 may also be provided to provide the additional energy necessary
to force the liquid refrigerant through the evaporator heat exchanger.
[0009] According to the embodiment shown in Figures 1-5, low pressure liquid refrigerant
("LPL") is supplied to the evaporator by pump 16 via expansion devices 11. The refrigerant
accepts heat from the refrigerated space, leaves the evaporator as low pressure vapor
("LPV") and liquid and is delivered to the liquid-vapor separation device 12 (which
may optionally be a cyclonic separator) which separates the liquid from the vapor.
Liquid refrigerant ("LPL") is returned to the pump 16, and the vapor ("LPV") is delivered
to the compressor 10 which condenses the vapor and sends high pressure vapor ("HPV")
to the condenser 8 which compresses it to high pressure liquid ("HPL"). The high pressure
liquid ("HPL") is delivered to the economizer 14 which improves system efficiency
by reducing the high pressure liquid ("HPL") to intermediate pressure liquid "IPL"
then delivers it to the liquid-vapor separation device 12, which supplies the pump
16 with low pressure liquid refrigerant ("LPL"), completing the refrigerant cycle.
The glycol flow path (in the case of optional glycol defrost system) and compressor
oil flow path is also shown in Figures 1-5, but need not be discussed in more detail
here, other than to note that the present low charge packaged refrigeration system
may optionally include full defrost and compressor oil recirculation sub-systems within
the packaged system. Figures 1-5 also include numerous control, isolation, and safety
valves, as well as temperature and pressure sensors (a.k.a. indicators or gages) for
monitoring and control of the system. In addition, optional sensors 26a and 26b may
be located downstream of said evaporators 2a and 2b, upstream of the inlet to the
liquid-vapor separation device 12, to measure vapor/liquid ratio of refrigerant leaving
the evaporators. According to alternative embodiments, optional sensor 26c may be
located in the refrigerant line between the outlet of the liquid-vapor separation
device 12 and the inlet to the compressor 10. Sensors 26a, 26b and 26c may be capacitance
sensors of the type disclosed in
U.S. Serial Nos. 14/221,694 and
14/705,781, the disclosures of which are incorporated herein by reference, in their entirety.
Figure 6 shows an example of a combined penthouse evaporator module and a prepackaged
modular machine room according to an embodiment of the invention. According to this
embodiment, the evaporator is housed in the evaporator module, and the remaining components
of the system shown in Figures 1-5 are housed in the machine room module. Various
embodiments of condenser systems that may be employed according to the invention include
evaporative condensers, with optional internally enhanced tubes, air cooled fin and
tube heat exchangers with optional internal enhancements, air cooled microchannel
heat exchangers, and water cooled heat exchangers. In the case of air cooled condenser
systems, the condenser coils and fans may be mounted on top of the machine room module
for a complete self-contained rooftop system. Other types of condenser systems may
be located inside the machine room. According to this embodiment, the entire system
is completely self-contained in two roof-top modules making it very easy for over-the-road
transport to the install site, using e.g., flat bed permit load non-escort vehicles.
The penthouse and machine room modules can be separated for shipping and/or for final
placement, but according to a most preferred embodiment, the penthouse and machine
room modules are mounted adjacent to one-another to maximize the reduction in refrigerant
charge. According to a most preferred embodiment, the penthouse module and the machine
room module are integrated into a single module, although the evaporator space is
separated and insulated from the machine room space to comply with industry codes.
Figures 7, 10 and 11 show other examples of adjacent penthouse evaporator modules
and machine room modules.
[0010] Figures 8, 9 and 12 are three dimensional cutaway perspective views of the inside
of a pre-packaged modular machine room and condenser unit according to an embodiment
of the invention, in which all the elements of the low charge packaged refrigeration
system are contained in an integrated unit, except the evaporator. As discussed herein,
the evaporator may be housed in a penthouse module, or it may be suspended in the
refrigerated space, preferably directly below the location of the machine room module.
According to these embodiments, the evaporator is configured to directly cool air
which is in or supplied to a refrigerated space.
[0011] According to alternative embodiments (e.g., in which end users to not wish refrigerated
air to come into contact with ammonia-containing parts/tubing), the evaporator may
be configured as a heat exchanger to cool a secondary non-volatile fluid, such as
water or a water/glycol mixture, which secondary non-volatile fluid is used to cool
the air in a refrigerated space. In such cases, the evaporator may be mounted inside
the machine room.
[0012] Figure 13 is a cutaway three-dimensional perspective view of the inside of a combined
penthouse evaporator module and a prepackaged modular machine room.
[0013] The combination of features as described herein provides a very low charge refrigeration
system compared to the prior art. Specifically, the present invention is configured
to require less than six pounds of ammonia per ton of refrigeration capacity. According
to a preferred embodiment, the present invention can require less than four pounds
of ammonia per ton of refrigeration. And according to most preferred embodiments,
the present invention can operate efficiently with less than two pounds per ton of
refrigeration capacity. By comparison, prior art "stick-built" systems require 15-25
pounds of ammonia per ton of refrigeration, and prior art low charge systems require
approximately 10 pounds per ton of refrigeration. Thus, for a 50 ton refrigeration
system, prior art stick built systems require 750-1,250 pounds of ammonia, prior art
low charge systems require approximately 500 pounds of ammonia, and the present invention
requires less than 300 pounds of ammonia, and preferably less than 200 pounds of ammonia,
and more preferably less than 100 pounds of ammonia, the report threshold for the
EPA (assuming all of the ammonia in the system were to leak out. Indeed according
to a 50 ton refrigeration system of the present invention, the entire amount of ammonia
in the system could be discharged into the surrounding area without significant damage
or harm to humans or the environment.
[0014] While the present invention has been described primarily in the context of refrigeration
systems in which ammonia is the refrigerant, it is contemplated that this invention
will have equal application for refrigeration systems using other natural refrigerants,
including carbon dioxide.
[0015] The description of the invention is merely exemplary in nature and, thus, variations
that do not depart from the concept of a packaged (one-or two-module integrated and
compact system) low refrigerant charge (i.e., less than 10lbs of refrigerant per ton
of refrigeration capacity) refrigeration system are intended to be within the scope
of the invention. Any variations from the specific embodiments described herein but
which otherwise constitute a packaged, pumped liquid, recirculating refrigeration
system with charges of 10 lbs or less of refrigerant per ton of refrigeration capacity
should not be regarded as a departure from the spirit and scope of the invention set
forth in the following claims.
[0016] The invention may be defined according to the following numbered paragraphs:
- 1. A refrigeration system comprising:
a refrigerant evaporator coil,
vapor/liquid separation structure connected to an outlet of said evaporator coil via
refrigerant line configured to separate low pressure refrigerant vapor from low pressure
refrigerant liquid;
a refrigerant compressor connected to an outlet of said liquid-vapor separation device
via refrigerant line and configured to compress refrigerant vapor from said vapor
liquid separation structure;
a refrigerant condenser connected to an outlet of said refrigerant compressor via
refrigerant line and configured to condense refrigerant vapor produced in said compressor
to refrigerant liquid,
a high pressure-side expansion device connected to an outlet of said refrigerant condenser
via refrigerant line and configured to reduce pressure of refrigerant liquid received
from said refrigerant condenser;
a collection vessel connected to an outlet of said high pressure-side expansion device
via refrigerant line for receiving refrigerant liquid from said high pressure-side
expansion device;
a low pressure-side expansion device connected to an outlet of said collection vessel
via refrigerant line and configured to reduce pressure of refrigerant liquid received
from said collection vessel;
refrigerant line connecting an outlet of said low pressure-side expansion device to
an inlet of said vapor/liquid separation structure and configured to deliver refrigerant
liquid to said separation structure;
said vapor/liquid separation structure having a liquid outlet that is connected via
refrigerant line to an inlet of said evaporator;
wherein said vapor/liquid separation structure, said compressor, said high pressure
side expansion device, said collection vessel, and said low pressure side expansion
device are situated inside a pre-packaged modular machine room;
wherein said refrigeration system requires less than six pounds of refrigerant per
ton of refrigeration capacity.
- 2. A refrigeration system according to 1, wherein said refrigerant is ammonia.
- 3. A refrigeration system according to 1, wherein said vapor/liquid separation structure
comprises a cyclonic separator.
- 4. A refrigeration system according to 1, wherein said vapor/liquid separation structure
comprises a recirculator vessel.
- 5. A refrigeration system according to 1, wherein said collection vessel comprises
a cyclonic separator.
- 6. A refrigeration system according to 1, wherein said collection vessel comprises
an economizer.
- 7. A refrigeration system according to 1, wherein said evaporator coil has internal
enhancements to improve the flow of liquid/vapor therein and improve heat exchange
and refrigerant charge.
- 8. A refrigeration system according to 1, wherein said condenser comprises coils having
internal enhancements.
- 9. A refrigeration system according to 1, wherein said condenser comprises a microchannel
heat exchanger.
- 10. A refrigeration system according to 1, further comprising a liquid to vapor mass
ratio sensor situated inside refrigerant line connecting said evaporator coil and
said vapor/liquid separation structure.
- 11. A refrigeration system according to 1, further comprising a liquid to vapor mass
ratio sensor situated inside refrigerant line connecting said vapor/liquid separation
structure and said compressor.
- 12. A refrigeration system according to 1, further comprising an oil separator vessel
configured to separate compressor oil from refrigerant vapor received from said compressor.
- 13. A refrigeration system according to 1, wherein said condenser is an air-cooled
condenser comprising coil and condenser fans located on top of said pre-packaged modular
machine room.
- 14. A refrigeration system according to 1, wherein said condenser is located inside
said pre-packaged modular machine room.
- 15. A refrigeration system according to 1, which requires less than four pounds of
refrigerant per ton of refrigeration capacity.
- 16. A refrigeration system according to 1, which requires less than two pounds of
refrigerant per ton of refrigeration capacity.
- 17. A refrigeration system comprising:
a refrigerant condenser; and
a pre-fabricated modular machine room containing:
vapor/liquid separation structure configured to be connected to an outlet of an evaporator
via refrigerant line;
a refrigerant compressor connected to an outlet of said separation structure via refrigerant
line; and connected to an inlet of said condenser via refrigerant line;
a collection vessel connected to an outlet of said refrigerant condenser via refrigerant
line;
refrigerant line connecting an outlet of said collection vessel to an inlet of said
vapor/liquid separation structure;
wherein said vapor/liquid separation structure has an outlet that is configured to
be connected via refrigerant line to an inlet of an evaporator;
and wherein said refrigeration system requires less than six pounds of refrigerant
per ton of refrigeration capacity.
- 18. A refrigeration system according to 17, further comprising an evaporator connected
to an inlet of said vapor/liquid separation structure and connected to an outlet of
said vapor/liquid separation structure.
- 19. A refrigeration system according to 18, wherein said evaporator is mounted in
a pre-fabricated modular evaporator room.
- 20. A refrigeration system according to 18, wherein said evaporator is mounted in
a refrigerated space adjacent to or below said pre-fabricated modular machine room.
- 21. A refrigeration system according to 17, further comprising a recirculator pump
situated in a refrigerant flow path between a fluid outlet of said vapor/liquid separation
structure, and an inlet of an evaporator.
- 22. A refrigeration system according to 17, wherein said condenser is an air-cooled
condenser comprising coils and a fan that are configured to be mounted on top of said
pre-fabricated modular machine room.
- 23. A method for reducing the amount of refrigerant per ton of refrigeration capacity
in a refrigeration system having an evaporator, liquid/vapor separator, a compressor,
a condenser, and a collection vessel, said method comprising packaging said compressor,
said liquid vapor separator and said collection vessel in a pre-fabricated modular
machine room, mounting said condenser on a roof of said pre-fabricated modular machine
room in the case of an air-cooled condenser, and connecting said evaporator to said
pre-fabricated modular machine room via refrigerant line.
- 24. A method according to 23, wherein said evaporator is mounted in a pre-fabricated
modular evaporator room.
- 25. A method according to 24, wherein said pre-fabricated modular evaporator room
is installed adjacent to said pre-fabricated modular machine room.
- 26. A method according to 23, wherein said evaporator is mounted in a refrigerated
space directly beneath said pre-fabricated modular machine room.
- 27. A method for reducing the amount of refrigerant per ton of refrigeration capacity
in a refrigeration system having an evaporator, liquid/vapor separator, a compressor,
a condenser, and a collection vessel, said method comprising installing a pre-fabricated
modular machine room including said compressor, said liquid vapor separator and said
collection vessel, and connecting said evaporator to said pre-fabricated modular machine
room using refrigerant line.
- 28. A method according to 27, comprising installing a pre-fabricated modular evaporator
room adjacent to said pre-fabricated modular machine room.
- 29. A method according to 27, comprising installing said evaporator in a refrigerated
space directly beneath said pre-fabricated modular machine room.
- 30. A method according to 27, wherein said condenser is located inside said pre-fabricated
modular machine room.
- 31. A method according to 27, wherein said condenser is an air-cooled condenser comprising
coils and fans, and wherein said method comprises mounting said condenser on top of
said pre-fabricated modular machine room.
1. A refrigeration system comprising:
a pre-fabricated modular evaporator room containing an evaporator (2a;2b) comprising
a refrigerant evaporator coil (4a, 4b),
a pre-fabricated refrigerant condenser unit including a refrigerant condenser (8),
said condenser is an air-cooled condenser which comprises which a coil and fans, and
which condenser is configured to condense refrigerant vapour to refrigerant liquid;
a pre-fabricated modular machine room;
wherein the pre-fabricated modular evaporator room, the pre-fabricated refrigerant
condenser unit and the pre-fabricated machine room are capable of being transported
over-the-road to an install site;
the pre-fabricated modular machine room containing:
liquid-vapor separation structure (12) connected to an outlet of said evaporator coil
via refrigerant line configured to separate low pressure refrigerant vapor from low
pressure refrigerant liquid;
a refrigerant compressor (10) connected to an outlet of said liquid-vapor separation
structure and to an inlet of said refrigerant condenser via refrigerant line and configured
to compress refrigerant vapor from said liquid-vapor separation structure;
a high pressure-side expansion device connected to an outlet of said refrigerant condenser
via refrigerant line and configured to reduce pressure of refrigerant liquid received
from said refrigerant condenser;
a collection vessel (14) connected to an outlet of said high pressure-side expansion
device via refrigerant line for receiving refrigerant liquid from said high pressure-side
expansion device;
a low pressure-side expansion device connected to an outlet of said collection vessel
via refrigerant line and configured to reduce pressure of refrigerant liquid received
from said collection vessel;
refrigerant line connecting an outlet of said low pressure-side expansion device to
an inlet of said liquid-vapor separation structure and configured to deliver refrigerant
liquid to said separation structure;
said liquid-vapor separation structure having a liquid outlet that is connected via
refrigerant line to an inlet of said evaporator;
wherein one or both of liquid-vapor separation device and collection vessel are in
the
form of single or dual phase cyclonic separators;
wherein said pre-fabricated refrigerant condenser unit is configured to be installed
atop said pre-fabricated modular machine room, and wherein said pre-fabricated modular
evaporator room is configured to be installed adjacent said pre-packaged modular machine
room;
wherein said refrigeration system comprises less than 2.72Kg (six pounds) of refrigerant
per 3.52 kW of refrigeration capacity (per ton of refrigeration capacity).
2. A refrigeration system according to claim 1, wherein said condenser unit (8) comprises
a microchannel heat exchanger.
3. A refrigeration system according to claim 1, further comprising a liquid to vapor
mass ratio sensor (26a, 26b) situated inside refrigerant line connecting said evaporator
coil and said liquid-vapor separation structure (12).
4. A refrigeration system according to claim 1, further comprising a liquid to vapor
mass ratio sensor (26a, 26b) situated inside refrigerant line connecting said liquid-vapor
separation structure (12) and said compressor (10).
5. A refrigeration system according to claim 1, further comprising an oil separator vessel
configured to separate compressor oil from refrigerant vapor received from said compressor
(10).
6. A refrigeration system according to claim 1, which comprises less than 1.81Kg (four
pounds) of refrigerant per 3.52 kW of refrigeration capacity (ton of refrigeration
capacity).
7. A method for reducing the amount of refrigerant per ton of refrigeration capacity
in a refrigeration system having an evaporator (2a, 2b), liquid/vapor separator, a
compressor, a condenser (8), and a collection vessel, wherein said condenser is an
air-cooled condenser comprising coils and fans, said method comprising installing
a pre-fabricated modular machine room which includes said compressor, said liquid
vapor separator and said collection vessel, and the method further comprising installing
a pre-fabricated modular evaporator room, which comprises the evaporator, adjacent
to said pre-fabricated modular machine room, wherein said installing step comprises
connecting said evaporator to said pre-fabricated modular machine room using refrigerant
line, and the method further comprises mounting said condenser on top of said pre-fabricated
modular machine room.