U.S. patent application number 13/836779 was filed with the patent office on 2014-09-18 for refrigeration apparatus and method.
The applicant listed for this patent is Benoit RODIER. Invention is credited to Benoit RODIER.
Application Number | 20140260361 13/836779 |
Document ID | / |
Family ID | 51521100 |
Filed Date | 2014-09-18 |
United States Patent
Application |
20140260361 |
Kind Code |
A1 |
RODIER; Benoit |
September 18, 2014 |
REFRIGERATION APPARATUS AND METHOD
Abstract
An energy management system may include a refrigeration
apparatus. Heat rejected from that apparatus may be used for
heating elsewhere. There may be cooling loads which may be prone to
frosting. A defrosting apparatus is provided. It is segregated from
the coolant distribution array. Recaptured heat of the
refrigeration apparatus may be used to defrost the cooling load
heat exchangers, in an alternating or cycling mode, as may be. The
apparatus may be electronically controlled. Ammonia may be used in
a primary refrigeration vapour cycle system. The apparatus may also
use a secondary cooling loop or system, linked to the primary
system. The secondary system may be a distribution system. The
secondary system may use CO.sub.2 as a heat transport medium. The
coolant system may be an high pressure system, whereas the defrost
system is a low pressure system. Separate circuits are provided for
coolant and defrost.
Inventors: |
RODIER; Benoit; (Ville
D'Anjou, Quebec, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
RODIER; Benoit |
Ville D'Anjou, Quebec |
|
CA |
|
|
Family ID: |
51521100 |
Appl. No.: |
13/836779 |
Filed: |
March 15, 2013 |
Current U.S.
Class: |
62/80 ; 165/61;
62/272; 62/340 |
Current CPC
Class: |
F25B 7/00 20130101; F25D
21/12 20130101; F25B 39/02 20130101; F25B 2309/06 20130101 |
Class at
Publication: |
62/80 ; 62/272;
165/61; 62/340 |
International
Class: |
F25D 21/06 20060101
F25D021/06 |
Claims
1. A refrigeration apparatus having a heat exchanger, said heat
exchanger having a first flow path for a moist air cooling load to
be chilled; a second flow path defining an evaporator for a
refrigerant fluid; and a third flow path through which to conduct a
defrost fluid; said second and third flow paths being segregated
from each other whereby refrigerant fluid in said second flow path
is isolated from defrost fluid in said third flow path.
2. The refrigeration apparatus of claim 1 wherein said first flow
path is an ambient air pressure flow path, said second flow path is
a high pressure flow path, and said third flow path is a low
pressure flow path.
3. The refrigeration apparatus of claim 2 wherein said refrigerant
fluid includes a heat transfer transport medium carried in said
second flow path at a pressure of at least 100 psia.
4. The refrigeration apparatus of claim 3 wherein said defrost
fluid is carried in said third flow path at a pressure of less than
100 psig.
5. The refrigeration apparatus of claim 1 wherein said refrigerant
fluid includes CO.sub.2.
6. The refrigeration apparatus of claim 1 wherein said defrost
fluid includes a fluid other than CO.sub.2.
7. The refrigeration apparatus of claim 6 wherein said defrost
fluid is a liquid, the liquid being a brine that includes
glycol.
8. The refrigeration apparatus of claim 1, further comprising a
cooling machine, said cooling machine having a work input, cooling
output, and a heat rejection output, said cooling machine having a
working fluid that is other than CO.sub.2.
9. The refrigeration apparatus of claim 1 wherein said third flow
path is operatively connected with a heat rejection output of said
refrigeration apparatus whereby, in operation, said heat rejection
output is connected to heat the defrost fluid to be conducted
through said third flow path.
10. The refrigeration apparatus of claim 1, further comprising a
controller operable selectively to direct refrigerant fluid to said
heat exchanger during a first time period, and to direct defrost
fluid to said heat exchanger during a second time period, said
second time period being different from said first time period.
11. The refrigeration apparatus of claim 1 wherein: said
refrigeration fluid is at least predominantly CO.sub.2; said
defrost fluid is a brine that is other than CO.sub.2; and said
third flow path includes a portion in which said defrost fluid is
heated by recaptured waste heat rejected from said refrigeration
apparatus.
12. The refrigeration apparatus of claim 11 wherein said heat
exchanger is a first heat exchanger, and said refrigeration
apparatus further comprises: at least a second heat exchanger; a
cooling machine operable to chill CO.sub.2 and to reject heat; said
cooling machine having a working fluid, said working fluid being at
least predominantly ammonia; at least a first receiver reservoir in
which one of (a) said working fluid, and (b) said CO.sub.2 is
maintained in liquid phase; a thermal reservoir in which to store
recaptured waste heat rejected by said cooling machine; and control
apparatus operable selectively to direct chilled CO.sub.2 to any of
said heat exchangers, said control apparatus also being operable
selectively to direct heated defrost fluid to respective ones of
said heat exchangers at times other than when chilled CO.sub.2 is
being directed thereto.
13. The refrigeration apparatus of claim 1 further including a
cooling machine operable to chill CO.sub.2 and to reject heat; and
said cooling machine has a working fluid, said working fluid being
at least predominantly ammonia; whereby said CO.sub.2 is chilled by
heat exchange with cold ammonia, and said defrost fluid is warmed
by heat rejected from hot ammonia.
14. The refrigeration apparatus of claim 1 further including a
cooling machine operable to chill CO.sub.2 and to reject heat; and
said cooling machine has a working fluid, said working fluid being
at least predominantly and HFC; whereby said CO.sub.2 is chilled by
heat exchange with cold ammonia, and said defrost fluid is warmed
by heat rejected from the HFC.
15. A refrigeration apparatus comprising: a cooling machine having
a work input, a cooling output, and a heat rejection output; a
first heat exchanger mounted to extract heat from a first cooling
load, the first cooling load having a frost point; a first
transport apparatus connected to carry a first heat transfer
transport medium that has been chilled by said cooling output of
said cooling machine to said first heat exchanger to cool said
cooling load; a second transport apparatus connected to carry a
second, heated, heat transfer transport medium to said first heat
exchanger; said second transport apparatus being segregated from
said first heat transfer transport medium whereby said first and
second heat transfer transport media are segregated from each
other; when said first heat transport medium is directed to said
heat exchanger, said heat exchanger being operable at a temperature
below the frost point of the first cooling load; and when said
second heat transport medium is directed to said heat exchanger,
said heat exchanger being operable at a temperature above the frost
point of the first cooling load.
16. The refrigeration apparatus of claim 15 wherein said second
transport apparatus is connected to receive heat from said heat
rejection output.
17. The refrigeration apparatus of claim 16 wherein said apparatus
further comprises a thermal storage member connected to receive
heat from said heat rejection output, and said second transport
apparatus is connected to receive heat from said heat rejection
apparatus that has been stored in said thermal storage member.
18. The refrigeration apparatus of claim 15 wherein said first
transport apparatus is an high pressure fluid transport apparatus
operable at pressure greater than 250 psia., and said first heat
exchanger defines an evaporator for the first heat transfer
transport medium.
19. The refrigeration apparatus of claim 15 wherein the first heat
transfer transport medium is CO.sub.2.
20. The refrigeration apparatus of claim 15 wherein the second heat
transfer transport medium is other than CO.sub.2.
21. The refrigeration apparatus of claim 20 wherein the second heat
transfer transport medium is a brine that includes glycol.
22. The refrigeration apparatus of claim 15 wherein said cooling
machine has a working fluid other than CO.sub.2.
23. The refrigeration apparatus of claim 22 wherein said working
fluid of said cooling machine is at least predominantly
ammonia.
24. The refrigeration apparatus of claim 15 wherein said cooling
machine is housed in a first location, said first heat exchanger is
housed in a second location, and said first location is
independently ventilated to external ambient.
25. The refrigeration apparatus of claim 22 wherein said
refrigeration apparatus includes a receiver reservoir for said
working fluid of said cooling machine.
26. The refrigeration apparatus of claim 15 wherein said apparatus
comprises a receiver reservoir for the second heat transfer
transport medium.
27. The refrigeration apparatus of claim 15 wherein said first
transport apparatus is a high pressure transport apparatus operable
at pressures exceeding 250 psia.
28. The refrigeration apparatus of claim 15 wherein said second
transport apparatus is a low pressure transport apparatus having an
operating envelope pressure lower than 100 psig.
29. The refrigeration apparatus of claim 15 wherein said apparatus
includes at least a second heat exchanger mounted to extract heat
from a second cooling load, the second cooling load having a frost
point.
30. The refrigeration apparatus of claim 15 wherein said apparatus
includes an ice-making refrigeration load.
31. The refrigeration apparatus of claim 30 wherein said ice-making
refrigeration load includes an ice-builder.
32. The refrigeration apparatus of claim 15 wherein said apparatus
includes at least an additional heating load and associated heat
transfer transport apparatus connected to conduct rejected heat
from said cooling machine thereto.
33. The refrigeration apparatus of claim 32 wherein said additional
heating load includes at least one of: (a) human activity space
heating; (b) a washing facility; (c) an ice melt pit; (d) a
swimming pool; and (e) water heating.
34. The refrigeration apparatus of claim 15 further comprising a
controller operable selectively to direct refrigerant fluid to said
first heat exchanger during a first time period, and to direct
defrost fluid to said first heat exchanger during a second time
period, said second time period being different from said first
time period.
35. The refrigeration apparatus of claim 33 wherein said controller
is operable selectively to direct chilled heat transfer transport
medium fluid to any cooling load of said apparatus at different
time periods, and is operable selectively to direct warmed heat
transfer transport medium fluid to any heating load of said
apparatus.
36. The refrigeration apparatus of claim 15 wherein said apparatus
is operable to direct heat rejected by said cooling machine at a
first time to said first heat exchanger at a later time,
notwithstanding that at such later time said cooling machine may be
one of (a) shut down; and (b) dormant.
37. A method of defrosting a heat exchanger, the heat exchanger
having a first flow path for a moist air cooling load to be
chilled; a second flow path defining an evaporator for a
refrigerant fluid; and a third flow path through which to conduct a
defrost fluid; said second and third flow paths being segregated
from each other whereby refrigerant fluid in said second flow path
is isolated from defrost fluid in said third flow path, said method
comprising conducting refrigerant fluid to second flow path in a
first time period, during which frost accumulates on said heat
exchanger; and conducting heated defrost fluid through said second
flow path during a second time period whereby the previously
accumulated frost diminishes.
38. The method of claim 37 wherein said method includes ceasing
flow of said refrigerant during flow of said defrost fluid.
39. The method of claim 37 wherein the step of conducting the
refrigerant fluid includes conducting the refrigerant fluid at a
pressure of at least 120 psia.
40. The method of claim 37 wherein the method includes using
CO.sub.2 as the refrigerant fluid.
41. The method of claim 37 wherein the step of conducting heated
defrost fluid occurs at a pressure less than 100 psig.
42. The method of claim 37 wherein the method includes using a
brine as the defrost fluid, the brine including glycol.
43. The method of claim 37 wherein the method includes using a
refrigerating apparatus to chill said refrigeration fluid,
rejecting heat from said refrigeration apparatus while chilling
said refrigeration fluid; and using said rejected heat to heat the
defrost fluid.
44. The method claim 43 wherein said method includes saving heat
rejected at a first time, and using that rejected heat to heat the
defrost fluid at a later time.
45. The method of claim 43 wherein said method includes employing
ammonia as a working fluid in the refrigeration apparatus.
46. The method of claim 43 wherein said method includes using heat
rejected from said refrigeration apparatus also to address at least
one additional heating load other than heating said defrost
fluid.
47. The method of claim 37 wherein said method includes using
refrigerant chilled by said refrigerating apparatus to address at
least one additional cooling load other than chilling refrigerating
fluid for chilling said moist air cooling load of said heat
exchanger.
48. The method of claim 37 wherein there is a plurality of heat
exchangers having moist air cooling loads, and said method includes
cycling refrigerant fluid and defrost fluid to said plurality of
heat exchangers selectively whereby each heat exchanger has a
defrost cycle.
49. The method of claim 37 wherein the method includes using a
refrigeration apparatus to chill the refrigeration fluid, and the
method includes using CO.sub.2 as the refrigeration fluid.
Description
FIELD OF INVENTION
[0001] This application relates to refrigeration apparatus.
BACKGROUND OF THE INVENTION
[0002] In refrigeration systems in which the cooling load involves
passing moist air over a heat exchanger having a surface
temperature below the dew point temperature of the air,
accumulation of frost on the heat exchanger has been a
long-standing problem.
[0003] Quite typically, defrosting involves ceasing the flow of
chilled coolant to the heat exchanger, and passing a heated heat
transport medium through the heat exchanger instead. Other methods
of defrosting may include hot water defrost, electric defrost, and
warm air defrost. In known systems, the heat transport medium,
namely the fluid selected as the coolant, is used for both
purposes. In the cooling mode, the coolant is taken from the
receiver on the low pressure side of the equipment. In the heating
mode the same fluid, heated by whatever means, is passed through
the cooling apparatus instead. Defrost systems of this general type
are shown and described, for example, in U.S. Pat. No. 6,481,231 of
Vogel et al., issued Nov. 19, 2002, and in U.S. Pat. No. 4,102,151
of Kramer et al.
SUMMARY OF INVENTION
[0004] The following summary may introduce the reader to the more
detailed discussion to follow. The summary is not intended to, and
does not, limit or define the claims. The disclosure may disclose,
and the claims may claim, more than one invention or more than one
inventive aspect or features of any such invention.
[0005] In an aspect of the invention there is a refrigeration
apparatus. The refrigeration apparatus has a heat exchanger. The
heat exchanger has a first flow path for an air cooling load to be
chilled; a second flow path defining an evaporator for a
refrigerant fluid; and a third flow path through which to conduct a
defrost fluid. The second and third flow paths are segregated from
each other whereby refrigerant fluid in the second flow path is
isolated from defrost fluid in the third flow path.
[0006] In a feature of that aspect of the invention, the first flow
path is an ambient air pressure flow path, the second flow path is
a low temperature flow path where the fluid evaporates, and the
third flow path is a higher temperature flow path where the fluid
does not change phase. In a further feature, the refrigerant fluid
includes a heat transfer transport medium carried in the second
flow path at a temperature below 0 C. The refrigerant fluid is
carried at a pressure of greater than 100 psig. In a still further
feature, the defrost fluid is carried in the third flow path at a
temperature greater than 0 C. The defrost fluid is carried at a
pressure of less than 100 psig. In another feature, the refrigerant
fluid includes CO.sub.2. In still another feature, the defrost
fluid includes a fluid other than CO.sub.2. In a further feature,
the defrost fluid is a liquid, the liquid is a brine that includes
glycol.
[0007] In still another feature of that aspect, the refrigeration
apparatus includes a cooling machine. The cooling machine has a
work input, a cooling output, and a heat rejection output. The
cooling machine has a working fluid that is other than CO.sub.2. In
still another feature, the third flow path is operatively connected
with a heat rejection output of the refrigeration apparatus
whereby, in operation, the heat rejection output is connected to
heat the defrost fluid to be conducted through the third flow path.
In yet another feature, the refrigeration apparatus has a
controller operable selectively to direct refrigerant fluid to the
heat exchanger during a first time period, and to direct defrost
fluid to the heat exchanger during a second time period, the second
time period is different from the first time period.
[0008] In another feature, the refrigeration fluid is at least
predominantly CO.sub.2; the defrost fluid is a brine that is other
than CO.sub.2; and the third flow path includes a portion in which
the defrost fluid is heated by recaptured waste heat rejected from
the refrigeration apparatus. In still another feature, the heat
exchanger is a first heat exchanger. The refrigeration apparatus
further includes at least a second heat exchanger; and a cooling
machine operable to chill CO.sub.2 and to reject heat. The cooling
machine has a working fluid. The working fluid is at least
predominantly ammonia. There is at least a first receiver reservoir
in which one of (a) the working fluid, and (b) the CO.sub.2 is
maintained in liquid phase. There is a thermal reservoir in which
to store recaptured waste heat rejected by the cooling machine. The
control apparatus is operable selectively to direct chilled
CO.sub.2 to any of the heat exchangers, the control apparatus also
is operable selectively to direct heated defrost fluid to
respective ones of the heat exchangers at times other than when
chilled CO.sub.2 is directed thereto.
[0009] In still another feature, the apparatus includes a cooling
machine operable to chill CO.sub.2 and to reject heat. The cooling
machine has a working fluid. The working fluid is at least
predominantly ammonia. The CO.sub.2 is chilled by heat exchange
with cold ammonia, and the defrost fluid is warmed by heat rejected
from hot ammonia.
[0010] In another aspect of the invention there is a refrigeration
apparatus. It has a cooling machine having a work input, a cooling
output, and a heat rejection output. A first heat exchanger is
mounted to extract heat from a first cooling load. The first
cooling load has a frost point. A first transport apparatus is
connected to carry a first heat transfer transport medium that has
been chilled by the cooling output of the cooling machine to the
first heat exchanger to cool the cooling load. A second transport
apparatus connected to carry a second, heated, heat transfer
transport medium to the first heat exchanger. The second transport
apparatus is segregated from the first heat transfer transport
medium whereby the first and second heat transfer transport media
are segregated from each other. When the first heat transport
medium is directed to the heat exchanger, the heat exchanger is
operable at a temperature below the frost point of the first
cooling load. When the second heat transport medium is directed to
the heat exchanger, the heat exchanger is operable at a temperature
above the frost point of the first cooling load.
[0011] In a feature of that aspect of the invention, the second
transport apparatus is connected to receive heat from the heat
rejection output. In another feature, the apparatus further
comprises a thermal storage member connected to receive heat from
the heat rejection output, and the second transport apparatus is
connected to receive heat from the heat rejection apparatus that
has been stored in the thermal storage member. In another feature,
the first transport apparatus is a low temperature fluid transport
apparatus operable at a temperature less than 0 C (or,
alternatively, at a pressure of greater than 100 psig), and the
first heat exchanger defines an evaporator for the first heat
transfer transport medium. In a further feature, the first heat
transfer transport medium is CO.sub.2. In another feature, the
second heat transfer transport medium is other than CO.sub.2. In a
further feature, the second heat transfer transport medium is a
brine that includes glycol. In another feature, the cooling machine
has a working fluid other than CO.sub.2. In a further feature of
that other feature, the working fluid of the cooling machine is at
least predominantly ammonia. In still another feature, the cooling
machine is housed in a first location, the first heat exchanger is
housed in a second location, and the first location is
independently ventilated to external ambient.
[0012] In still another feature, the refrigeration apparatus
includes a receiver reservoir for the working fluid of the cooling
machine. In another feature, the apparatus comprises a receiver
reservoir for the second heat transfer transport medium. In still
another feature, the first transport apparatus is a transport
apparatus operable at temperatures of less than 0 C. In another
feature, the second transport apparatus is a high temperature
transport apparatus having an operating envelope at temperatures
greater than 0 C. In yet another feature, the apparatus includes at
least a second heat exchanger mounted to extract heat from a second
cooling load, the second cooling load having a frost point. In
still yet another feature, the apparatus includes an ice-making
refrigeration load.
[0013] In another aspect of the invention there is a method of
defrosting a heat exchanger. The heat exchanger has a first flow
path for a moist air cooling load to be chilled; a second flow path
defining an evaporator for a refrigerant fluid; and a third flow
path through which to conduct a defrost fluid. The second and third
flow paths are segregated from each other whereby refrigerant fluid
in the second flow path is isolated from defrost fluid in the third
flow path, the method comprising conducting refrigerant fluid to
second flow path in a first time period, during which frost
accumulates on the heat exchanger; and conducting heated defrost
fluid through the second flow path during a second time period
whereby the previously accumulated frost diminishes.
[0014] In a feature of that aspect, the method includes ceasing
flow of the refrigerant during flow of the defrost fluid. In a
further feature, the method includes using CO.sub.2 as the
refrigerant fluid. In another feature, the step of conducting
heated defrost fluid occurs at a temperature greater than 0 C. In a
further feature, the method includes using a brine as the defrost
fluid, the brine including glycol. In another feature, the method
includes using a refrigerating apparatus to chill the refrigeration
fluid, rejecting heat from the refrigeration apparatus while
chilling the refrigeration fluid; and using the rejected heat to
heat the defrost fluid. In a further feature, the method includes
saving heat rejected at a first time, and using that rejected heat
to heat the defrost fluid at a later time. In still another
feature, the method includes employing ammonia as a working fluid
in the refrigeration apparatus. In yet still another feature, the
method includes using heat rejected from the refrigeration
apparatus also to address at least one additional heating load
other than heating the defrost fluid. In another feature, the
method includes using refrigerant chilled by the refrigerating
apparatus to address at least one additional cooling load other
than chilling refrigerating fluid for chilling the air cooling load
of the heat exchanger. In a further feature, there is a plurality
of heat exchangers having air cooling loads, and the method
includes cycling refrigerant fluid and defrost fluid to the
plurality of heat exchangers selectively whereby each heat
exchanger has a defrost cycle. In another feature, the method
includes using a refrigeration apparatus to chill the refrigeration
fluid, and the method includes using CO.sub.2 as the refrigeration
fluid.
[0015] In another aspect, there is an energy management system. The
energy management system includes a refrigeration apparatus. The
refrigeration apparatus is operable to reject heat. A heating load
apparatus is connected to be heated by the heat rejected from the
refrigeration apparatus. The heating load apparatus includes a
defrost apparatus. A load management control system is operable at
a first time to cause ice to be made at the refrigeration load ice
sheet apparatus and to cause heat to be directed from the
refrigeration apparatus to the defrost apparatus. The load
management control system is operable at a second time to cause the
thermal storage apparatus to be charge as a cold sink and to cause
heat to be directed from the refrigeration apparatus to the heating
load apparatus.
BRIEF DESCRIPTION OF THE ILLUSTRATIONS
[0016] These and other features and aspects of the invention may be
explained and understood with the aid of the accompanying
illustrations, in which:
[0017] FIG. 1 shows a schematic representation of an example of a
refrigeration apparatus embodying principles of the invention;
[0018] FIG. 2 shows a schematic representation of an alternate
example of a refrigeration apparatus to that of FIG. 1, showing a
cascade system; and
[0019] FIG. 3 shows a schematic of a heat exchanger of the
refrigeration apparatus of FIG. 1
DETAILED DESCRIPTION
[0020] The description that follows, and the embodiments described
therein, are provided by way of illustration of an example, or
examples, of particular embodiments incorporating one or more of
the principles, aspects and features of the present invention.
These examples are provided for the purposes of explanation, and
not of limitation, of those principles, aspects and features of the
invention. In the description, like parts are marked throughout the
specification and the drawings with the same respective reference
numerals.
[0021] The scope of the invention herein is defined by the claims.
Though the claims are supported by the description, they are not
limited to any particular example or embodiment, and any claim may
encompass processes or apparatuses other than the specific examples
described below. Other than as indicated in the claims themselves,
the claims are not limited to apparatuses or processes having all
of the features of any one apparatus or process described below, or
to features common to multiple or all of the apparatus described
below. It is possible that an apparatus, feature, or process
described below is not an embodiment of any claimed invention.
[0022] The terminology used in this specification is thought to be
consistent with the customary and ordinary meanings of those terms
as they would be understood by a person of ordinary skill in the
art in North America. The Applicants expressly exclude all
interpretations that are inconsistent with this specification, and,
in particular, expressly exclude any interpretation of the claims
or the language used in this specification such as may be made in
the USPTO, or in any other Patent Office, other than those
interpretations for which express support can be demonstrated in
this specification or in objective evidence of record,
demonstrating how the terms are used and understood by persons of
ordinary skill in the art, or by way of expert evidence of a person
or persons of experience in the art.
[0023] In the discussion herein, a refrigeration machine, or
chiller, is one that draws heat from a heat source at a lower
temperature, and rejects heat to a heat sink at a higher
temperature. Machines of this nature are sometimes referred to as
heat pumps. In general, such a machine may be a gas cycle machine
or a vapour cycle machine, and will have a work input, a cooling
load output, and a rejected heat output. The work input may
correspond to the mechanical work required to drive a compressor
(or compressors) and may be supplied by an electric or hydraulic
motor, or by an internal combustion engine, or other suitable power
source.
[0024] The embodiments of refrigeration apparatus described herein
may be vapour cycle machines employing a gas phase compressor (or
compressors), whether single stage, multiple stage or cascade
system; a high pressure side condenser whence heat is rejected from
the working fluid and in which the working fluid changes phase from
gas to liquid; a pressure reduction device which may be a nozzle or
valve; and an evaporative device such as an evaporator in which
chilled working fluid may absorb heat from air as it is cooled and
in which the working fluid may "flash", i.e., change phase, from
liquid to gas as it extracts heat from the heat source to be
cooled. Of course, whether a device is a heating or cooling device
has an aspect of arbitrariness depending on point of view: An
evaporator may be a heating device for the working fluid, but is
equally a cooling device to the cooling load; the condenser is a
cooling device for the working fluid, but a heating device for the
medium to which that heat is rejected.
[0025] A distinction is made herein between a primary, or direct,
system, in which the working fluid passed through the compressor is
also the cold side heat transfer transport medium circulated
through a cooling distribution array; and an indirect system in
which there is a separate or secondary distribution array, which
may employ a heat transfer transport medium that is either the same
as, or different from, the working fluid of the primary system in
the refrigeration machine. In an indirect system the working fluid
uses as its heat source a heat exchanger of the secondary system
that forms the heat rejection side of the distribution or secondary
system.
[0026] Where the heat transfer transport fluid of the secondary
system is a phase changing fluid, the heat source heat exchanger of
the primary system may function as the condenser of the secondary
system, with the distribution array of heat exchangers of the
secondary systems being the evaporators of the secondary fluid.
[0027] Whether the system is a primary, or direct, system, or an
indirect system having a secondary loop for distribution, where
there is a phase changing fluid in either the primary or the
secondary loop there may be a receiver, or reservoir, in which to
collect a portion of the heat transport medium, be it primary or
secondary. Typically, a receiver may be located on the low pressure
side, downstream of the condenser and upstream of the
evaporator.
[0028] In this specification there is reference to heat transfer
transport media. In general this term refers to substances that are
heated or cooled at one location, and cooled or heated at a distant
location, thereby transferring heat between the two locations. Most
typically, such media are fluids. Many fluids have been used as
coolants, refrigerants, or heating fluids. The fluids may be liquid
in one portion of their use in operation, and in gas form in
another portion of their use or operation. Some fluids are single
phase (whether liquid or gas) or two-phase (typically liquid and
gas). In the refrigeration industry these fluids are often
coolants, and many of these fluids may be referred to as a "brine"
or "brines". A brine can be a single phase liquid, and, typically,
the term "brine" is used where that liquid has a freezing point
other than (generally lower than) the freezing point of water.
Although perhaps historically the term brine may have been derived
from a liquid such as water having a salt in solution therein, such
as to alter its freezing point, the contemporary use of the word
"brine" includes substances that do not necessarily include
dissolved salts such as alcohol, carbon dioxide (CO.sub.2), ammonia
(NH.sub.3). The term "volatile brine" is sometimes used to describe
a CO.sub.2 system in which the CO.sub.2 does not undergo
compression, but is circulated as a cooling medium and undergoes a
phase change. Brines may also include such things as glycol (more
properly, ethylene glycol), or partial mixtures of glycol and
water. A brine may also be a two phase fluid, in which the brine
material is at its boiling point, or in which one component (or
more) of the mixture is in a gas phase, and another is in a liquid
phase.
[0029] There is also discussion in this specification of "working
fluids". In the context of a refrigeration system, the "working
fluid" is used herein as a fluid in a primary refrigeration circuit
or system that is compressed in one stage, has heat withdrawn from
it in another stage, is de-pressurized in a third stage, and has
heat added to it in a fourth stage. Over the last 120 years many
fluids have been used as working fluids, including air, Freon
(CFC's), HFC's, ammonia, and carbon dioxide. There may also be
"working fluids" used in secondary circuits such as the heat
rejection piping array, and in the cooling distribution array.
[0030] Ammonia may be chosen as a working fluid in the
refrigeration cycle compressor for a number of reasons. It is
readily available; it is relatively inexpensive; it dissipates
relatively quickly and easily in air, it does not tend to cause
lasting environmental damage in terms of either ozone depletion or
greenhouse gas emissions if it leaks, and does not tend to present
a long lasting toxicity problem when disposal is desired; and, in
ice making technology, there is a well-established level of
knowledge and expertise in the industry in using ammonia. Further,
the working range of pressures and temperatures for ammonia may
tend to be suitable for the present purposes. Ammonia may tend to
permit the use of relatively common oil lubricants, as opposed to
highly specialized (and expensive) hygroscopic oils. Ammonia may
tend to permit smaller pipe sizes, better heat transfer and smaller
heat exchangers. Leaks may tend to be relatively easy to detect.
Ammonia tends to be relatively tolerant of moisture in the
system.
[0031] In the embodiments described, the logic of the system may
dictate that the fluid in a particular conduit must flow in a
particular direction. This may be indicated in the illustrations by
arrowheads. Although pumps and check valves may be indicated in the
illustrations, it may be understood that each embodiment is
provided with such circulation pumps and check valves as may be
appropriate to cause fluid to flow in the correct direction,
without cluttering the illustrations with unnecessary detail. It is
also understood that systems shown and described herein have
suitable pressure relief and surge protection, as would be
understood by persons of skill without such features being
shown.
[0032] Referring to the general arrangement of FIG. 1, a
refrigeration apparatus is shown generally as 20. In general,
refrigeration apparatus 20 includes a cooling machine 22 that has a
work input such as provided at compressors 24, 26 (which may be in
parallel, or may be staged in series). Refrigeration apparatus 20
also includes one or more heat rejection outputs, such as
condensers 28; a working-fluid pressure drop apparatus 30, such as
a nozzle or turbine or motor or work-extracting pump; and a cooling
load output 32, such as at an evaporator 34. There may be more than
one evaporator 34. The cooling load output 32 can also be thought
of equivalently as a heat input to the system. A receiver or
accumulator, or reservoir 36 may also be included. Reservoir 36 may
be located downstream of condenser 28, and upstream of evaporator
34. All of items 24, 26, 28, 30, 32 and 34 define elements of a
primary circuit, or loop, or system, of a refrigeration machine
such as cooling machine 22.
[0033] Refrigeration apparatus 20 may be located in a building
facility, such as may have a cooling or refrigeration load, or a
variety of such loads, indicated generally as 40. The facility may
be a factory, such as a food processing factory, but may also be
any other facility having a refrigeration load. That refrigeration
load may include first, second, third, and perhaps more, individual
heating load members or elements, each of those cooling loads being
represented generically by a heat exchanger, such as heat
exchangers 42, 44 and 46. Each of heat exchangers 42, 44, 46 may be
an evaporator. Each of heat exchangers 42, 44, 46 is connected to
the rest of refrigeration apparatus 20 by a heat transfer medium
transport apparatus 50, which may have the form of pipes, or
piping, or conduits, however termed, for carrying the heat transfer
transport medium, namely the coolant fluid. It may be that each of
heat exchangers 42, 44, 46 has its own independent circuit, or flow
path of piping, in a parallel and independently controllable path,
or one or more units may be arranged in series depending on cooling
loads and needs in the facility.
[0034] In the embodiment shown in FIG. 1, transport apparatus 50
includes delivery piping 52 that carries a first heat transfer
transport medium, in the form of a chilled coolant, from a heat
rejection heat exchanger, such as heat exchanger 34, to the
refrigeration or cooling load or loads 40, and such others as may
be, that define a cold sink (or heat source) at which heat from
loads 40 is added to the coolant, thus raising its enthalpy.
Transport apparatus 50 may also include return piping 54 that
carries higher enthalpy (i.e., heated) coolant back to heat
exchange 34. As may be understood, the cooling circuit, or loop,
that includes items 42, 44, 46, 50, 52 and 54 is a secondary loop,
or secondary system, and it is a coolant distribution system or
circuit or array, all of which may be indicated generally as 58.
The secondary loop may include a pump 48, although a pump may not
be necessary in all applications. The secondary loop 58 may include
a receiver 56. Receiver 56 may define a reservoir for condensed
coolant, and may be located downstream of heat exchanger 34 (which,
in the context of secondary loop 58 may act as a condenser), and
upstream of such of heat exchangers 42, 44, 46 of cooling load 40
as may be.
[0035] Similarly, refrigerating apparatus 20 may include a
transport apparatus 60, which may have the form of pipes, or
piping, or conduits, however termed, for carrying a second heat
transfer transport medium from the heat rejection output of cooling
machine 22 to heat exchangers 42, 44, 46. Transport apparatus 60
may include delivery tubing or pipes or conduits, however called,
indicated as 62, and return tubing, or pipes, or conduits however
called, indicated as 64. Transport apparatus 60 may be termed a
defrost fluid transport apparatus, or circuit, or loop and may have
pumps, such as pump 74, control valves, and check valves as may be
appropriate.
[0036] On the heat rejection side, there may be heating loads 66,
68. Whether there are heating loads 66, 68 or not, refrigeration
apparatus 20 may include a thermal storage reservoir 70, which may
have the form of a tank 72 in which heated material may be
retained. As noted, there may be more than one condenser 28. In the
embodiment of FIG. 1, there may be a first condenser 76.
Alternatively there may be both a first condenser 76 and a second
condenser 78. First condenser 76 may be connected via piping
manifolds 71 and 73 to thermal storage reservoir 70, and either
through manifolds 71 and 73 or through reservoir 70 to heating
loads such as loads 66, 68, or such other heating loads as the
facility may have, including the defrost load fed by transport
apparatus 60. Second condenser 78 of apparatus 20 may be an
evaporative condenser 78. In the event that either condenser 76
cannot extract enough heat from the primary working fluid, or in
the event that there is too much heat stored in thermal storage
reservoir 70, that heat can be rejected to ambient at second
condenser 78. That is, second condenser 78 acts in two modes. In a
first mode, it exchanges heat from the heat rejection side working
fluid to external atmosphere through one side or coil, with the
return line running in effectively a parallel path back to receiver
36 as opposed to coolant passing through condenser 76. In a second
mode, second condenser 78 exchanges heat from the thermal storage
reservoir 70 (or from fluid diverted from manifolds 75) through
another side or coil of second condenser 78 to external ambient. In
the second side or coil it may not be functioning as a condenser,
in the sense that the transport fluid may be single phase liquid,
such as glycol or a glycol mixture, that is not intended to flash
from liquid to vapour.
[0037] The heated material may be the transport medium to which
heat is rejected from condenser 28. Whether as a decanting tap from
thermal storage reservoir 70, a pipe connection to hot manifold 71;
or as a segregated flow path through a heat exchange coil heated by
condenser 76 or thermal storage reservoir 70, transport apparatus
60 may be operated to carry defrost fluid that has been heated by
the captured (i.e., retained) waste heat output of machine 22,
either directly or in a time-shifted, or time-delayed, manner from
reservoir 70. The heat transfer transport medium used as the
defrost fluid may be any suitable fluid. For this purpose, although
other fluids might be used in either liquid or gas form, the
transport fluid may be either polyethylene glycol or a mixture that
is partially glycol. In the refrigeration loop the transport fluid
may be a liquid, and may remain a liquid throughout passage through
the defrost loop.
[0038] In the embodiment of FIG. 1, at least one of the
refrigerating loads faced by heat exchanger 42, 44 or 46 is a moist
air cooling load. The nature of refrigeration is such that the
possibility of frosting is expected where the desired temperature
of the materials to be cooled at the output cooling load end is to
be below the freezing temperature of water. To that end, any or all
of heat exchangers 42, 44, 46 may be used to chill air in a zone to
be maintained below freezing; frost may accumulate on the air flow
path side of the heat exchanger. From time to time, it may be
necessary to remove the frost build-up in a defrosting cycle. In
this discussion, "moist" means that the airflow has high enough
absolute humidity for frost to form on a below-freezing temperature
surface.
[0039] In the embodiments shown and described, any or all of heat
exchangers 42, 44 and 46 may have three flow passages, or pathways,
or coils, or circuits, however they may be called. There is a first
flow path 80, a second flow path 82, and a third flow path 84.
[0040] First flow path 80 may be understood to be the flow path of
the fluid of the cooling load, namely a moist air flow path. As may
be understood, air may be urged along the flow path by a blower or
fan 85 in a forced air system.
[0041] Second flow path 82 may be understood to be the flow path of
the refrigerant. This flow path may include a finned conduit 86 for
the cooling medium. In one embodiment the coolant is a substance
that is a liquid which may be converted to a gas at operating
pressures, and that is carried under pressure. Finned conduit 86
may be an evaporator for that cooling medium. The cooling medium
may be CO.sub.2. Finned conduit 86 (and the rest of the circuit of
which it is part), may have the physical property of being capable
of containing fluids at high pressure. For the purpose of this
description, high pressure is a pressure in excess of 250 psia. For
CO.sub.2 operation, although under various operating conditions the
pressures may be higher or lower, the piping of the refrigerant
flow path may have the physical property of being operable not only
in excess of 500 psia, but also in excess of 1000 psia, and
possibly of operation at 2000 psia. In normal refrigerating
operation, the refrigerant flows through the finned tube, and the
moist air to be cooled flows through the fin-work, with heat
flowing from the load to be cooled and into the coolant, reducing
the enthalpy of the load and increasing the enthalpy of the
coolant, possibly to such an extent as may cause the coolant to
boil in whole or in part.
[0042] Third flow path 84 is a defrost flow path. It may include a
finned coil 88. Finned coil 88 may be parallel to finned coil 86,
or it may share the same finwork as finned coil 86, or it may be
immediately upstream of finned coil 86. Finned coil 86 may share
the same fins or finwork as finned coil 88. Finned coil 88 and the
other components of the defrost circuit, define a low pressure
circuit or system, which has the physical property of being
operable up to 250 psia. It may be that the components will contain
fluid at higher pressures, however the operating range may be less
than 100 psig, and may be less than 50 psia. It may be of the order
of less than 10 psig.
[0043] Third flow path 84 is segregated from second flow path 82.
That is, the flow paths of the refrigerating and defrost circuits
are segregated such that coolant from second flow path 82 is
prevented from entering third flow path 84, and coolant from third
flow path 84 is prevented from entering second flow path, such that
neither fluid can contaminate the other. Similarly, air from first
flow path 80 cannot enter either second flow path 82 or third flow
path 84. In normal operation, second flow path 82 operates at a
lesser pressure than the third flow path 84. In normal operation
both second flow path 82 and third flow path 84 operate at
pressures greater than first flow path 80.
[0044] To that end refrigeration apparatus 20 has a controller,
which may be an electronic controller, and which may be a
programmed digital electronic controller. The controller is
operable to direct chilled coolant through second flow path 82
during normal refrigerating operation. The controller is also
operable to direct heated defrost fluid through third flow path 84.
The controller is also operable to cease flow of chilled coolant
during a defrost cycle and to cease flow of defrost fluid during a
refrigeration cycle.
[0045] In a system with multiple cooling loads, such as 42, 44 and
46 (or however many more loads there may be) the controller is
operable selectively to cycle the chilled coolant and defrost flows
for each unit by causing valves to open an closed appropriately.
That is, during a defrost cycle one cooling unit may be taken
off-line at a time for defrost, while the remainder continue to
chill the cooling load. When defrost is complete on that unit, it
may be brought back on-line, and the next unit taken off-line and
heated by defrost fluid, and so on in turn. Furthermore, where a
rejected heat thermal energy storage reservoir 70 is employed, heat
rejected during a chilling cycle may be retained and used to
defrost the same heat exchanger previously chilled. It is not
necessary that the compressors be run constantly. That is, there
may be time periods where neither chilling nor defrosting is
required, and the compressors may be off or dormant. Alternatively,
there may be periods where chilling is required, but that cooling
demand can be met, if temporarily, by the quantity of chilled
coolant previously accumulated in the receiver, whether in the
cooling machine or in the coolant fluid distribution array, as may
be. Similarly, the defrost fluid pump 74 may be operated to
circulate heated defrost fluid whether the compressors are in
operation or not. When operated in this manner, the refrigeration
system also permits heating load-shifting from one time of day to
another.
[0046] It may be that refrigeration apparatus 20 is part of a
larger facility or building 90. Referring to the general
arrangement of FIG. 1, a facility such as a meat or fish packing
plant 92 may include a zone to be chilled by heat exchangers 42,
44, 46, etc., and may also include other facilities such as a
heated water tank, offices or meeting rooms, change rooms and
showers, and so on. The refrigeration equipment may be fully
integrated with building mechanical systems in a combined heating,
air conditioning and refrigeration system. It may be advantageous
to employ the rejected heat for additional purposes. It may be
advantageous to employ the refrigeration apparatus as a heat pump
to provide a source of heat for rejection, with an ice by-product
that can be melted at a subsequent opportunity at which heat is
required. That is, heating and cooling loads may not occur during
the same time period, or may be unequally matched. Given that both
heating and cooling loads may vary during the day, it may be
advantageous to provide a large amount of rejected heat at one time
of day, and a large amount of refrigeration at another.
[0047] The building may include a meat or fish packing plant 92, a
hot water tank 94, offices, conference rooms, or meeting rooms 96,
change rooms 98, showering facilities 100, or some combination
thereof. The packing plant may include an ice builder 102, i.e., a
facility designed to cool ice into blocks or cubes, such as may be
used, for example, in the food service industry or grocery stores,
or within the plant itself. Such a building may have cooling loads
(that is, a need for cooling or refrigeration) and heating loads
(that is, a need for heating) that may vary with the time of day,
the season of the year, the activities occurring in the building,
and the amount of sunshine per day. There may be simultaneous
heating and cooling loads, as when there is a cooling load to make
ice, and a heating load to keep the occupied office or meeting
spaces warm. A space that requires heating at one time of day may
require cooling at another time of day.
[0048] In general, there will be time varying-cooling and heating
load profiles for building 90. The cooling load may tend to be
lowest at night, and higher during the day, particularly when the
Sun is shining. During the night the facility may be on "night
set-back", since the packing facilities may be closed for the
night, and need only be maintained in its condition. The heat loads
may be less at night as well, given the generally cooler external
ambient at night, the absence of a lighting load (assuming the
lights are turned off at night).
[0049] Building 90 may be equipped with an energy management
system, indicated generally as 110, for responding to these
environmental loading conditions. Energy management system 110 may
include refrigeration apparatus 20, as described above; a cold sink
thermal storage member, or apparatus, indicated as "ice builder"
102; a hot water supply 104, such as may be used to provide
domestic hot water within the plant for whatever uses; a building
fan coil heating or air conditioning system 106, a building heat
pump 108, and a supplemental heating device 112, such as may be a
back-up oil or gas fired boiler.
[0050] Cooling machine 22 of refrigerating apparatus 20 may be
contained in a separate building, or segregated structure, from the
building or structure in which the coolant distribution apparatus
of items 40 and 50 are located. This construction permits all
devices through which the primary system working fluid passes
(which may be referred to as the refrigeration plant) to be
segregated from, and to be separately ventilated from, the enclosed
building structure of the facility in which persons may be at work.
In this way, a leak of the working fluid may tend not to migrate
into occupied areas of the facility, and may be vented to external
ambient.
[0051] The coolant delivery apparatus, or array, so defined by
items 40 and 50 may be quite large in physical extent. In such a
system use of a two phased, or phase changing, transport system may
permit a large enthalpy change per unit mass of the distribution
fluid, and a corresponding reduction in both the mass flow rate of
that fluid, and of the pumping power requirement. The inventor
considers CO.sub.2 to be a suitable distribution array heat
transfer transport fluid. At normal operating temperatures between,
for example -40 C and +200 C, however, CO.sub.2 may be maintained
under quite high pressures. Those pressures may be well in excess
of 250 psia (1.75 MPa), and may typically be higher than 500 psia.
A typical operating regime may be in the order or 900-1200 psia.
High pressure piping may be used, that piping having the physical
property of being operable at those pressures, and possibly at much
higher pressures in the range of 2000-3000 psia. The high pressure
piping may be steel piping, and may be stainless steel piping. In
operation, at very cold (-40 F) refrigerating conditions the
CO.sub.2 may be at about 130 psia. In general operation, the
CO.sub.2 pressure may be substantially higher. This may be
contrasted with a low pressure liquid piping system, such as may
carry glycol, which may typically operate at 10 psig. Thus it is
expected that the waste-heat defrost line will operate at less than
100 psig., whereas the high pressure evaporator side will operate
at substantially higher pressures than 100 psig, typically greater
than 120 psia, and almost always at greater than 130 psia. It
follows that to require defrosting, there must be cooling below 32
F or 0 C in the evaporator or high pressure path. Similarly, to
defrost, the low pressure defrost fluid must be warmer than 32 F or
C.
[0052] In keeping with this, heat transfer transport medium conduit
assemblies, namely the heating and cooling circuits emanating from
segregated structure, such as low pressure defrost circuit piping
of apparatus 60 that carry defrost fluid to and from heat
exchangers 42, 44, 46, may tend to be relatively low pressure
conduits operating at modest positive pressure over ambient,
carrying a more-or-less non-corrosive liquid heat transfer medium
in the nature of a liquid coolant of relatively low toxicity, and
low volatility, and such as may tend not to pose an undue
environmental hazard if a leak should occur, such an antifreeze or
antifreeze mixture, of which one type may be glycol or may include
glycol as a component of a mixture. Further, when used in the
context of this application the term "glycol" may refer to a
mixture of glycol and water such as may be suitable for the
operating range of the equipment, be it -30 C to +60 C, -40 C to
+70 C or some other range. The pressure of the defrost piping may
be less than 200 psia, less than 100 psig, may be less than 50 psig
(or 50 psia, as may be), and may typically be of the order of 10
psig. In the inventor's view it is desirable to keep the high
pressure coolant circuit segregated from the low pressure
defrosting circuit such that, for example, defrost fluid does not
contaminate the coolant system.
[0053] Optional ice builder 102 defines a cold sink thermal storage
member, or thermal capacitance member may, for brevity and
simplicity be referred to as an "ice reservoir". It may be that the
ice reservoir is an accumulation of ice, typically enclosed in an
insulated wall structure, or tank. It may also be that it is not
"ice" at all, but rather a brine, or an eutectic fluid, or some
other medium such as may tend to have a significant thermal mass,
such that the ice reservoir may tend to work as a thermal
capacitance that can be "charged up" by being cooled over a period
of time, so that it may then have a large capacity to cool other
objects at a later time. It may be that the ice reservoir employs a
phase change material, such as a eutectic fluid as noted above,
where there is a significant enthalpy drop between the warm state,
possibly a liquid state, and the cool, or cold state, possibly a
solid or quasi-solid state. A liquid freezing point would, for
example, tend to be just such a large enthalpy, narrow temperature
range phenomenon. Where an eutectic material is used, it may be an
eutectic having a phase change temperature lying in the range of
-40 to +20 F, or possibly in the narrower range of -20 F to +0 F.
The phase change medium may be water, or an aqueous solution.
[0054] The arrangement described may tend to permit coolant to flow
selectively to either ice builder 102 or to the elements of cooling
loads 40, such as evaporators 42, 44, 46, or to both in parallel
depending on valve positions in the system. Ice builder 102 may be
a large insulated enclosure, or box, or fluid-tight chamber through
which liquid coolant can be pumped. The enclosure may contain a
large number of thermal storage elements such as steel coils. They
may be stacked to permit interstitial flow of the liquid coolant,
and segregate the heat transfer storage medium phase change
material from the heat transfer transport medium. Ice builder 102
has an inlet, and an outlet, such that coolant fed in at the inlet
may tend to work its way through any of a large number of possible
flow paths by wending about the collection, or stacked array, to
the outlet, this process being accompanied by heat transfer between
the diffusely moving liquid and the thermal storage medium.
[0055] Thermal storage reservoir 70 is a large heat exchange fluid
heat transfer medium stratification reservoir, or tank. The cold
side loop drawing hot coolant from the outlet of condenser 76 is
carried to the hot side inlet near the top of reservoir 70, and may
be drawn out at the relatively lower temperature the outlet located
near the bottom of reservoir 70, through such pumps as may be used,
and back to the inlet of evaporator 34.
[0056] Thermal storage reservoir 70 is a reservoir in which the
rejected-heat side heat transfer fluid transport medium may settle
and stratify according to temperature. Thus hot return flow from
condenser 76 is added to the top of thermal storage reservoir 70,
and cooled coolant directed to the inlet of condenser 76 is drawn
from the bottom of thermal storage reservoir 70. Similarly, hot
fluid for direction to the various heating loads is drawn from the
upper region of storage reservoir 70, and returned to the
bottom.
[0057] On occasions where there may not be sufficient rejected heat
available from condenser 76 to meet all of the heating loads of the
facility 20, or where the temperature of the heat rejected is not
fully sufficient to meet the temperature requirements of, for
example, a radiant or fan coil heater or a hot water heater, that
unmet demand may be met by the employment of a supplemental heating
device 112, such as may be an oil or gas fired boiler. In this
embodiment supplemental heat, for defrost or such other purpose as
may be, in whole or in part, may be employed in the event that
refrigeration apparatus 20 is not in service, and an alternate heat
source is required. To that end, pumps may urge coolant from
thermal storage reservoir outlet manifold 73 to the boiler. In the
event that extra heating is not required, the coolant may pass
through the supplemental heating device, or through a bypass,
without the heating element being in operation. After leaving the
supplemental heating device, the fluid medium, having had a
temperature boost (or not, as may be appropriate in the
circumstances), may be directed to a pump such as may be used to
urge the warmed coolant through the building fan coil forced air
heating system, such as may be used in the facility, offices, and
so on. At some times of year this system may be used to provide
heating, and at other times of year to provide cooling (e.g. to act
as an air conditioner), such as when coolant from ice builder 102
is directed through cooling circuit of apparatus 50 and the
building fan coil and returned. When used for heating, coolant in
apparatus 70 exiting the fan coil heating system is carried along
return line to the inlet manifold.
[0058] Alternatively, or additionally, warm coolant leaving the
supplemental heating device may be directed through building
radiant zone heating apparatus such as may be installed in the
various rooms of the facility.
[0059] Operation of apparatus 20 is governed by an electronic
control system, such as may be termed energy management system 110,
that includes a controller, and an array of sensors such as may
include (a) temperature sensors; (b) pressure sensors; (c) humidity
sensors; (d) volumetric flow rate sensors; (e) thermostat settings;
(f) external ambient condition sensors (g) solar sensors; and (h) a
clock, or clocks. The use of temperature and pressure sensors in
refrigeration apparatus permits the operating statepoints to be
known, and adjusted, according to existing heating and cooling
demands, and according to anticipated demand such as may be
determined from historic demand parameters stored in memory, and on
the basis of external weather conditions.
[0060] The electronic control system may include a memory having
climatic data for the site of installation, including sun rise and
sunset times for the location, and it may have stored ambient
temperature and pressure information from recent days for use in
extrapolating thermal load management estimates. It may include
setting temperatures for the various heat sinks and heat sources.
The memory data may include data for working fluid pressure,
temperature, enthalpy, entropy, and density, from which other,
intermediate statepoint conditions may be interpolated. The
electronic control system may also include programmed steps for
calculating the statepoints at which refrigeration apparatus 20
might best operate for given loading conditions, or expected
loading conditions based on time of day, weather, and historic
demand.
[0061] The electronic controller may assess heating and cooling
loads throughout the facility. Having done so, it may determine the
output heat rejection temperature at the thermal storage reservoir,
and may signal the various heat load pumps to operate as may be
required. Where there is surplus heat rejection, the controller may
cause the closed circuit cooler to operate to soak up the extra
rejected heat. Where there is insufficient rejected heat to meet
the heating load demand, the controller may cause the supplemental
heating element to operate to boost the temperatures in the heating
system or systems. Where a larger amount of rejected heat is
desired, and before causing the supplemental heating element to
operate, the controller may poll the condition of ice builder, may
check against values stored in memory for expected heating demand,
and may, if the ice builder is not fully charged (that is, it is
not at or below its low set point temperature, and not at the
minimum temperature that can be achieve by refrigeration apparatus
20). Provided that the time of day, and the point in the expected
load cycle is appropriate, the controller may then signal
refrigeration apparatus 20 to maintain a higher than otherwise high
side pressure, with corresponding higher rejection temperature, or
it may cause the compressor to run at a higher mass flow rate,
while also causing the heating load pumps to operate at a higher
flow rate, the net result being a greater rate of heat transfer.
Adjustment of the expansion device nozzle may also permit a change
in upstream pressure to be obtained. That is, where a specific
thermal rejection temperature is desired to achieve, for example,
an 80-95 F temperature in the radiant space heating apparatus, the
system may operate both to increase massflow rate of the working
fluid in the cooling machine 22, but, in addition, to choke the
system to yield a higher pressure in condenser 76 to give a
combination of higher temperature and higher mass flow rate. This
may then be accompanied by direction of coolant from the hot side
of evaporator 34 to ice builder 102. In the event that greater
heating is required, the electronic controller may signal for
supplemental heat.
[0062] Where ice builder 102 is used to provide cooling to the
condenser side, the freezing point of the thermal storage medium
may in some circumstances be in excess of 32 F., but less than the
desired heat rejection temperature of the condenser.
[0063] In an alternate embodiment, as shown in FIG. 2, an alternate
refrigeration apparatus is shown as 120. Apparatus 120 is
substantially the same as apparatus 20, but differs therefrom in
being a cascade system, rather than the volatile brine system of
apparatus 20. That is, apparatus 120 has a first cooling cycle
circuit 116, which includes compressors 24, 26; condenser 28;
pressure drop apparatus 30, and evaporator 34. Apparatus 120 also
has a second cooling circuit 118 or second cooling machine 122,
which includes compressors 124, 126; evaporator 34 serving as the
condenser 128 of second cooling circuit 118; a pressure drop
apparatus, such as a nozzle or valve 130; and a cooling load output
132, namely that of cooling or refrigeration load 40, and its
evaporators 42, 44, 46. Second cooling circuit 118 may also include
a receiver 136 mounted downsteam of nozzle 130 and upstream of load
40. Second cooling circuit 118 may include a refrigerant pump 148
operable to draw refrigerant from receiver 136 and to urge that
refrigerant to load 40 (or to ice builder 102, if used). The return
from load 40 is directed back into receiver 136. Compressors 124,
126 draw from the vapour of receiver 136, and output compressed gas
to condenser 128, and so on. Thus second cooling circuit 118 is
cascaded from first cooling circuit 116 the through the shared heat
exchange medium of evaporator 34--condenser 128, both of circuits
116 and 118 having their own respective compressor stages. The
upper cascade cycle is defined by a system such as ammonia vapour
cycle cooling machine 22, and the lower cascade cycle is defined by
a system such as a CO.sub.2 cycle machine in second cooling circuit
118.
[0064] In a summary of one embodiment, an industrial refrigeration
system includes an ammonia vapour cycle machine as cooling machine
22. A pair of compressors 24, 26 feed a heat exchanger, such as
condenser 28, with the condensate being collected in a high
pressure reservoir 36. Working fluid leaves the high pressure
reservoir through an expansion valve, or nozzle 30, whence it
passes into another heat exchanger 34 in which the ammonia
evaporates. The evaporated ammonia then flows back to the
compressors, and so on.
[0065] The use of ammonia in a distribution system inside an
enclosed building may not be desired. In the system illustrated
there is a cooling array symbolised by cooling loads 40, which may
be the cooling distribution system of a meat packing plant. It may
be a CO.sub.2 based array, in which CO.sub.2 at perhaps about 1000
psia (+ or -100 psi) is condensed to liquid in the heat exchanger
34 that is cooled by the ammonia system. The liquefied CO.sub.2
then flows through a check valve and into the distribution piping
to cooling heat exchanger array cooling load elements 42, 44, 46.
Flashed CO.sub.2 returns to the cascade heat exchanger, where it is
once again cooler.
[0066] The system includes a heat rejection and recapture circuit,
namely thermal storage reservoir 70. In the embodiment the heat
recapture system is a glycol system. In this system heat rejected
from the ammonia primary system is carried by the glycol from the
condenser 28, 76 to a reservoir identified as a thermal equalizer
tank 72.
[0067] As may be appreciated, from time to time the distribution
array frosts up. In this example, the evaporators each have a
CO.sub.2 circuit and a glycol circuit. When there is a need to
defrost the system, the flow of CO.sub.2 to the array is
interrupted, and flow of hot glycol from the thermal equalizer is
directed to the evaporators of the distribution system instead.
This heats the evaporators, causing them to defrost.
[0068] In this embodiment, (a) the system uses three working fluids
(NH.sub.3, CO.sub.2, Glycol); (b) two of the three fluids are two
phase-change fluids; (c) The heat for defrost is stored in a
reservoir; the heat for defrost is transported by a third fluid,
namely the glycol; (e) The heat exchangers on the refrigeration
array side have segregated flow circuits for the CO.sub.2 and the
glycol. Alternatively an HFC fluid, such as Freon or an HCFC, could
also be used as one of the three fluids.
[0069] What has been described above has been intended illustrative
and non-limiting and it will be understood by persons skilled in
the art that other variances and modifications may be made without
departing from the scope of the disclosure as defined in the claims
appended hereto. Various embodiments of the invention have been
described in detail. Since changes in and or additions to the
above-described best mode may be made without departing from the
nature, spirit or scope of the invention, the invention is not to
be limited to those details but only by a purposive construction of
the appended claims as required by law.
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