US20140260361A1

US20140260361A1 - Refrigeration apparatus and method

Info

Publication number: US20140260361A1
Application number: US13/836,779
Authority: US
Inventors: Benoit RODIER
Original assignee: Individual
Current assignee: Toromont Industries Ltd
Priority date: 2013-03-15
Filing date: 2013-03-15
Publication date: 2014-09-18

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 CO₂as 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.

Description

FIELD OF INVENTION

This application relates to refrigeration apparatus.

BACKGROUND OF THE INVENTION

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.
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

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.
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.
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 CO₂. In still another feature, the defrost fluid includes a fluid other than CO₂. In a further feature, the defrost fluid is a liquid, the liquid is a brine that includes glycol.
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 CO₂. 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.
In another feature, the refrigeration fluid is at least predominantly CO₂; the defrost fluid is a brine that is other than CO₂; 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 CO₂and 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 CO₂is 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 CO₂to 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 CO₂is directed thereto.
In still another feature, the apparatus includes a cooling machine operable to chill CO₂and to reject heat. The cooling machine has a working fluid. The working fluid is at least predominantly ammonia. The CO₂is chilled by heat exchange with cold ammonia, and the defrost fluid is warmed by heat rejected from hot ammonia.
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.
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 CO₂. In another feature, the second heat transfer transport medium is other than CO₂. 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 CO₂. 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.
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.
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.
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 CO₂as 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 CO₂as the refrigeration fluid.
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

These and other features and aspects of the invention may be explained and understood with the aid of the accompanying illustrations, in which:

FIG. 1 shows a schematic representation of an example of a refrigeration apparatus embodying principles of the invention;

FIG. 2 shows a schematic representation of an alternate example of a refrigeration apparatus to that of FIG. 1, showing a cascade system; and

FIG. 3 shows a schematic of a heat exchanger of the refrigeration apparatus of FIG. 1

DETAILED DESCRIPTION

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.
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.
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.
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.
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.
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.
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.
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.
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 (CO₂), ammonia (NH₃). The term “volatile brine” is sometimes used to describe a CO₂system in which the CO₂does 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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 CO₂. 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 CO₂operation, 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.
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.
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.
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.
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.
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.
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.
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).
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.
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.
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 CO₂to be a suitable distribution array heat transfer transport fluid. At normal operating temperatures between, for example −40 C and +200 C, however, CO₂may 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 CO₂may be at about 130 psia. In general operation, the CO₂pressure 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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 CO₂cycle machine in second cooling circuit 118.
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.
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 CO₂based array, in which CO₂at 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 CO₂then flows through a check valve and into the distribution piping to cooling heat exchanger array cooling load elements 42, 44, 46. Flashed CO₂returns to the cascade heat exchanger, where it is once again cooler.
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.
As may be appreciated, from time to time the distribution array frosts up. In this example, the evaporators each have a CO₂circuit and a glycol circuit. When there is a need to defrost the system, the flow of CO₂to 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.
In this embodiment, (a) the system uses three working fluids (NH₃, CO₂, 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 CO₂and the glycol. Alternatively an HFC fluid, such as Freon or an HCFC, could also be used as one of the three fluids.
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.

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 CO₂.

6. The refrigeration apparatus of claim 1 wherein said defrost fluid includes a fluid other than CO₂.

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 CO₂.

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 CO₂;

said defrost fluid is a brine that is other than CO₂; 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 CO₂and 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 CO₂is 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 CO₂to 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 CO₂is being directed thereto.

13. The refrigeration apparatus of claim 1 further including a cooling machine operable to chill CO₂and to reject heat; and said cooling machine has a working fluid, said working fluid being at least predominantly ammonia; whereby said CO₂is 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 CO₂and to reject heat; and said cooling machine has a working fluid, said working fluid being at least predominantly and HFC; whereby said CO₂is 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 CO₂.

20. The refrigeration apparatus of claim 15 wherein the second heat transfer transport medium is other than CO₂.

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 CO₂.

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 CO₂as 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 CO₂as the refrigeration fluid.