US3242689A - Cooling system and apparatus - Google Patents

Description

March 29, 1966 D. E. CHUBB ETAL COOLING SYSTEM AND APPARATUS Filed March 13, 1964 FROM COOLING UNITS To cooLlNG United States Patent Q 3,242,689 COOLING SYSTEM AND APPARATUS Donald Edward Chubb, Caldwell, Frederic A. MacConnell, Somerville, and John C. Conrad, New Providence,

N.J., assignors to Worthington Corporation, Harrison,

N.J., a corporation of Delaware Filed Mar. 13, 1964, Ser. No. 351,684 Claims. (Cl. 62-498) This invention relates to a refrigeration or air conditioning system. It relates in particular to an improved evaporator for use in the system.

Air conditioning systems particularly in the instance of multi-story buildings, are so designed to permit year round cooling. This characteristic is essential to virtually any cooling system designed for skin type buildings in which outer peripheral surfaces and areas are subject to wide temperature gradients, whereas the inner portions remain relatively stable regardless of ambient conditions.

As a matter of practically, an air conditioning system in such an installation is operated during substantially the entire year to provide necessary cooling and air circulation. It is known, that a suitable degree of cooling can economically be achieved during colder months of the year by utilizing the atmosphere as a heat sink for absorbing heat from the building.

During certain months of the year however, it becomes problematical whether or not to rely on the atmosphere alone or upon the system compressor to furnish the necessary cooling capacity.

Notably, during mild weather months of the year the system can be operated without the compressor where ambient conditions permit. Since the temperature variations during an ordinary day are not constant, and further, since the cooling requirements in a building during a relatively mild day are not constant, it is understandable that there would be a degree of uncertainty as to whether the system should be operated with the compressor or without.

To reduce this uncertainty, the present invention provides an improved refrigeration system which is particularly adapted to operate efliciently during mild temperature periods of the year to provide necessary cooling to a building or other installation. This is achieved by providing the system with a novel, improved evaporator adapted to increase heat exchange efliciency of the system when the compressor is not operated.

It is therefore an object of the invention to provide an improved refrigeration system circulating evaporable refrigerant, which is adapted to function satisfactorily under partial or light load conditions without use of the system compressor.

It is a further object to provide an improved evaporator unit of the shell and tube type in which wetting of the heat exchange tube surfaces provides improved heat transfer from a medium being cooled.

Another object is to provide a novel evaporator holding a pool of refrigerant liquid and having means for circulating said liquid to cause a violent agitation in the pool, and thus promote contact of the said liquid with scription of the system and apparatus, made in conjunction with the appended drawings.

FIGURE 1 of the drawings is a diagrammatic illustration of a refrigeration system of the type presently contemplating adapting to distribute liquid to a plurality of areas to be cooled.

FIGURE 2 is a diagrammatic illustration of an alternate embodiment of the evaporator shown in FIGURE 1.

FIGURE 3 is another diagrammatic illustration of an alternate embodiment of the evaporator shown in FIG- URE 1.

FIGURE 4 is still another alternate embodiment of the evaporator arrangement shown in FIGURE 1.

FIGURE 1 illustrates diagrammatically a refrigeration or air conditioning system adapted to condition a multistory building by the use of air distribution units disposed at various cooling Zones and supplied with streams of chilled water and air. To provide the necessary air chilling, cold water is circulated in from the evaporator, to an air distribution unit, and thereafter returned to the system to be rechilled.

As shown in FIGURE 1, the refrigeration system following accepted practice, is normally located in the basement or in the lower part of a building and includes a centrifugal compressor 14 having a suction inlet 16 and a discharge outlet 17. A driver not presently shown, is coupled to the compressor impeller shaft for rotating the same.

The driver is normally a motor of relatively high horse power depending on the system cooling capacity, and the operation thereof constitutes a major expense in operating the system.

A condenser 18 is formed by tube bundle 19 which is surrounded by an outer shell 21. The said shell is provided with an inlet 22 connected to the compressor discharge outlet 17 for receiving a stream of hot compressed vaporous refrigerant from the latter. Condenser tube bundle 19 is connected to an external piping circuit for carrying cooling water for heat exchange with a sink medium.

The external circuit includes an outdoor cooling tower 23, or similar cooling means, positioned normally on the roof of the building, and having a spray header 24 passing water into contact with atmospheric air drawn through the cooling tower by induction fan 26. A pool of cooling water 27 held in the cooling tower sump, is passed through a return line 28 to the condenser tube bundle 19 for recirculation therein.

The condenser shell 21 holds liquid refrigerant which has been condensed by contact with the colder condenser tube bundle 19.

The lower part of condenser shell 21 is connected by conduit 30 to a high pressure float regulator 31 including a valve 31' operable in response to the level of liquid in the float regulator to control liquid feed therethrough.

An evaporator 32 includes a tube bundle 33 disposed within a surrounding shell 35, and a conduit 36 which extends vertically thereof and is connected'to the outlet of high pressure float regulator 31 for receiving a stream of condensate therefrom. The said condensate stream will partially flash into vapor upon entry into the evaporator due to the lower pressure in the evaporator. Conduit 36 includes an outlet 36' which is preferably below the surface of the liquid pool in the evaporator, and includes means connected thereto for distributing the condensate into the pool across an extensive area.

.The evaporator tube bundle 33 is connected as shown to an external water circulating system for passing chilled water through pump 37 to the various cooling areas in the system. Evaporator shell 35 includes discharge outlet 38 connected to the compressor suction inlet 16. Outlet 38 may be provided with a mist collector 39 or other means for preventing liquid refrigerant from entering the compressor suction inlet.

A by-pass conduit 40 connected between the respective condenser and evaporator shells, is provided with a valve 41 adjustable through open and closed positions for controlling vapor flow between the condensing and evaporator portions of the system under certain operating conditions.

Valve 41 may be manually operable or preferably is automatically controlled to regulate flow therethrough in response to predetermined load conditions in the system.

The arrangement herein above described is not uncommon to the art and embodies the usual components and parts which normally make up such a system.

It is to be further understood that the system presently disclosed is for the purpose of illustrating the invention which is not limited to air conditioning of buildings, but rather, may be extended to other uses such as the production of chilled or cold process water for uses in which a chilled medium is required.

The novel features of the present evaporator unit are shown in the embodiments of the invention illustrated in FIGURES 1 through 4. Referring specifically to FIG- URE I, under normal operating conditions, evaporator 32 receives condensate metered through high pressure fiow regulator 31, and passed into the evaporator shell 35. Flashing of condensate in the reduced pressure atmosphere causes the condensate, which comes into contact with the surfaces of the evaporator tube bundle 32, to vaporize thereby chilling the medium circulating through tube bundle 33.

To increase heat the exchange characteristics of the evaporator, it is desirable to provide maximum heat exchange coefficient between the refrigerant and the surface of the tube bundle 33. This as shown by the prior art, may be achieved through a number of different means including the use of spray headers or nozzles positioned above evaporator tube bundle 33 for spraying liquid against the tube surfaces. Thus, liquid refrigerant may be drawn from the pool in the lower part of the evaporator shell and carried to the top thereof.

Since these overhead evaporator spray headers are rigidly held in place, it is understandable that an evaporator tube 33 will receive liquid in a substantially constant pattern depending on the disposition and number of the liquid headers and nozzles. Spray liquid then flows downwardly between and onto the respective tube walls for heat exchange with the chilled medium.

According to the present invention, the evaporator, rather than relying on sprayed refrigerant for the tube cooling, is provided with means for causing a violent and active foaming of the refrigerant pool held in the evaporator shell. The resulting foam will tend to substantially fill shell 34 as shown, thereby enveloping the tube bundle to more fully utilize the heat transfer areas thereof.

Referring again to FIGURE 1 one embodiment of the invention includes conduit means 46, having a fan, blower, or other means for propelling a forced feed stream of vapor therethrough. The inlet end of conduit 46 is connected as shown to the upper or vapor holding portion of the evaporator shell 35 for withdrawing a stream of vaporous refrigerant and supplying it to the suction inlet of the blower 47. The blower discharge end 47 of the blower 47 is connected as shown through conduit 46 to injection or vapor distribution means 49 disposed in the lower part of the evaporator beneath the liquid pool of refrigerant held in the evaporator shell 35.

As shown in FIGURE 1, blower 47 and conduit means 46 are prefer-ably disposed externally of evaporator shell 35, and include valves 51 and 60 connected in the said conduit means to facilitate replacement or repair of the blower upon the closing of the said valves.

As shown in FIGURE 2, the entire refrigerant foaming unit may be incorporated within the evaporator shell as indicated at 62 in the subject figure. Thus, the said shell will include an inlet 63 receiving condensate which is carried to condensate pool 64. A blower 66 is supported as shown within evaporator shell '62 and includes a suc- 4 tion inlet disposed in the upper, vapor holding portion of the said shell.

A filter, screen, or demister 67 may be connected to the blower inlet although this is not essential since a small amount of. vapor can be expected to condense in the blower without harming or hampering operation of the latter. Vapor distribution means 68 is connected to the blower discharge for injecting high pressure vapor streams into the condensate pool to cause the foaming action.

Referring again to FIGURE 1, the vapor distribution means presently contemplated consists generally of a manifold chamber connected to the lower discharge end of conduit 46 to receive va-porous refrigerant thereupon. A plurality of constricted openings 50' passing through the wall of the distributions means 49 deliver high velocity streams of vapors upward and throughout the condensate pool.

As shown in FIGURE 3, still another embodiment of the vapor injector or distribution means comprises a plurality of elongated manifolds '52 and 53 extending substantially the length of the evaporator shell as indicated at 54 in the subject figure along the bottom portion thereof. Manifolds 52 and 53 are fed by blower 74 through acornmon line 65, and are provided with a multiplicity of outlets defining constricted nozzles for individually introducing high velocity streams of refrigerant vapor to the surrounding liquid pool. It is advantageous as will be appreciated to dispose the vapor carrying manifolds as widely as possible through the refrigerant pool to achieve a degree of uniformity of foaming action. However, it is understood that the disposition of the manifolds and nozzles is dependent on the size of the evaporator and the amount of liquid refrigerant normally contained therein.

As shown in FIGURE 4, distribution means 56 includes a single manifold 57 formed by an enclosure extending the length of the evaporator shell, as indicated at 75 in the subject figure, along the bottom surface thereof and connected to the shell discharge outlet by conduit 75 with blower 68 connected therein as shown. A plurality of outlets 58 formed in manifold 57 inject high velocity streams into the liquid pool.

It has been found that a preferred structural arrangement of a vapor distribution means dictates that the manifold be so formed to minimize the pressure drop in the discharge line from the blower, to provide maximum pressure at the manifold nozzles. A perforate pipe or conduit extending lengthwise of the evaporator shell exemplifies one embodiment found to provide the desired foaming action in the refrigerant liquid.

Referring again to FIGURE 1, vaporous refrigerant drawn from the vapor holding portion of the evaporator shell 35 may be fed into one, or both ends of the vapor distribution means 49 or from a multiplicity of inlets communicated with the blower in order to provide balance to the entire system and to achieve uniformity of refrigerant foaming of the evaporator pool.

Since the refrigerant pool in the evaporator constitutes a head of liquid above the vapor distribution manifold 49, it is understood that blower 47 forceably introduces a vapor stream and must be of sufiicient discharge pressure to overcome the head pressure established by the liquid pool. A high speed, turbine type blower connected into conduit means 46 is found to provide the necessary injecting force to cause violent foaming throughout the refrigerant pool. The design of the blower however, is a matter of expediency depending on the capacity of the entire system which is reflected in the size of the evaporator shell and the amount of refrigerant used therein.

Operation of the system Referring to FIGURE 1, under normal operating conditions, requiring the provision of a desired degree of cooling to a building or other structure, the centrifugal compressor 14 is operated to feed a hot, compressed vaporous refrigerant into condenser shell 21. Hot refrigerant vapors upon contacting the cooler surfaces of condenser tube bundle 19, condense and fall to the lower condenser portion. Thereafter saturated liquid condensate is passed into high pressure flow regulator chamber 31 and is metered through valve 31' to conduit 36.

As previously mentioned, cooling Water circulated through condenser tube bundle 19 is passed to the upper or outer parts of the building and brought into contact with the atmosphere through a cooling tower or other appropriate means. With the compressor running under normal conditions, valve 41 within by-pass conduit 40 is closed thereby permitting only liquid flow from the high pressure condenser 18 to the lower pressure evaporator 32.

It is understood that by-pass conduit 40 and valve 41 constitute a device found in the prior art and may function to avoid compressor surge under limited load conditions. This is achieved by regulating the fiow of hot refrigerant vapor moving directly from the condenser to the evaporator through the said bypass conduit. For the present device and to facilitate the description, it is assumed that there will normally be no such flow through the by-pass conduit 40.

Flow of cooling water to condenser coil 19 is provided by pump 61 disposed in the external water circuit for directing heated condenser water to the cooling tower 23 in which the water is exposed to the atmosphere and cooled to a desired temperature.

Regulation of the system cooling capacity under normal operating conditions may be through the usual means such as valving, or compressor control in response to the condition of the chilled medium leaving the evaporator.

System operation without compresser During those seasons of the year particularly in the spring and the fall, which include days having temperatures approximating 58 wet bulb or lower, the necessary degree of cooling to discrete sections of the building may be provided without use of the high pressure side of the system. During such days, with the centrifugal compressor 14 completely out of operation, vaporous refrigerant is passed from evaporator shell 32 into compressor suction inlet 16, through the impeller and compressor discharge outlet 17 to discharge into the upper condenser shell 21. By-pass conduit valve 41 is opened permitting a free passage of warmed vapor, upward from the evaporator into the condenser portion to supplement the vaporous flow through the non-operating compressor.

Pump 61 in the external water circulatory system maintains a continuous flow from condenser coils 19 to the cooling tower 23 such that heated condenser water is sprayed into the 58 F. atmosphere. Thus, the condenser will continue to function and condense vaporous refrigerant received from the compressor discharge 17 and from the by-pass conduit 40, forming saturated liquid for passage into evaporator 32.

Without use of the present evaporator injection, the small amount of refrigerant condensed under free or noncompressor cooling conditions, would be inadequate to completely wet the surfaces of evaporator tube bundle 33 to a sufiicient degree for satisfying a load condition. However, regardless of the degree of the loading or the amount of liquid received from the condenser 21, the present evaporator foaming system will always be operable to inject a pressurized stream of vapor into the evaporator liquid pool. This will result since the evaporator, being located within the lower part of the system, will tend to accumulate refrigerant by gravitational feed under all loading conditions.

To provide the necessary evaporator tube wetting without use of centrifugal compressor 14, valves 51 and 60 are opened and blower 47 is actuated. Thus, a portion of refrigerant vapor rising from the liquid pool in the evaporator shell 35 will be drawn into blower 47 and discharged therefrom at a high velocity into the vapor distribution means 49. Thereafter vapor, on being forcibly discharged through constricted opening 50 into the refrigerant pool, causes a violent bubbling and boiling such that the refrigerant pool tends to foam up in the shell and rise about the evaporator tube bundles 33 into intimate contact therewith.

Since the primary source of evaporator tube wetting comes from the action of the evaporator vapor injection, it may be readily appreciated that the amount of liquid refrigerant required in any ststem will be much less than the amount required for operating the system without benefit of the evaporator injection. In the latter instance, the only tube wetting which might be achieved when the compressor is inoperable, comes from the accumulation of refrigerant at the bottom of the evaporator which would tend to form a pool sufficiently deep to wet only the lower portion of the tube bundle.

It may also be readily appreciated that thepresent evaporator and its utilization in a system of the type described results in several economic advantages. For example a considerable savings is realized in operating expenses since the centrifugal compressor 14 need not run so constantly. In addition, free cooling without the compressor is achieved by fully utilizing the systems refrigerant charge under all operating conditions, and without changing the capacity of the charge. Although the present system has been described herein as using evaporator injection as an alternative to compressor operation, this does not prohibit simultaneous use of both the compressor and evaporator injection if the need presents itself.

It is understood that the foregoing description constitutes a preferred embodiment of the novel concept and that certain modifications and changes may be made in the apparatus and method without departing from the spirit and scope of the invention.

What is claimed is:

1. For use in a refrigeration system circulating a vaporizable refrigerant and having compression means, condensing means connected to the compression means, and an evaporator connected to said condensing means and receiving expanded liquid condensate therefrom and discharging vaporous refrigerant to the compressor means, said evaporator comprising:

(a) a tube bundle carrying a medium to be cooled,

(b) a shell enclosing said tube bundle and holding liquid and vaporous refrigerant, said shell having a lower portion thereof holding a pool of said liquid refrigerant,

(c) a conduit communicating the upper portion of said shell holding vaporized refrigerant with said lower shell portion holding liquid refrigerant,

(d) means in said conduit for receiving vaporous refrigerant from the evaporator upper portion, and forming a high velocity vaporous stream thereof for introduction to liquid refrigerant contained in the evaporator.

2. In the system defined in claim 1 wherein said evaporator includes:

(a) vapor distribution means connected to the outlet of said conduit and positioned in said evaporator beneath the surface of said liquid refrigerant pool for introducing high velocity streams of vapor to the latter.

3. In a refrigeration system as defined in claim 2 wherein said vapor distribution means includes:

(a) a manifold, having an inlet communicated with the conduit;

(b) means in said manifold forming a plurality of constricted orifices for discharging high velocity vaporous streams into the liquid refrigerant pool.

4. In a refrigeration system defined in claim 3 wherein 7 said manifold extends substantially the length of the evaporator shell and being normally submerged beneath said refrigerant pool.

5. The combination claimed in claim 1 wherein (a) the last mentioned means includes a blower means disposed internally of the shell (b) the blower means to receive vaporized refrigerant from the upper portion of the shell and to discharge the vaporized refirigerant into the liquid refrigerant at the lower portion of the shell.

References Cited by the Examiner UNITED STATES PATENTS 101,682 4/1870 Tuttle et a1 62-309 228,487 6/1880 Tessie et al 62-121 X 310,025 12/1884 Brewer 6'2-121 1,781,051 11/1930 Carrier 62-114 LaWler 62-310 Boileau et al. 62-222 Han-son 62-310 Crawford 62-121 Newt-on 62-181 Zwickl 62-117 Camilli et al. 62-309 X Imperatore et al. 621 17 X Lowe 62-527 X Bunch 62-307 X Anderson et al. 62-117 Germany.

ROBERT A. OLEARY, Primary Examiner.

LLOYD L. KING, Examiner.

Claims (1)

1. FOR USE IN A REFRIGERATION SYSTEM CIRCULATING A VAPORIZABLE REFRIGERANT AND HAVING COMPRESSION MEANS, CONDENSING MEANS CONNECTED TO THE COMPRESSION MEANS, AND AN EVAPORATOR CONNECTED TO SAID CONDENSING MEANS AND RECEIVING EXPANDED LIQUID CONDENSATE THEREFROM AND DISCHARGING VAPOROUS REFRIGERANT TO THE COMPRESSOR MEANS, SAID EVAPORATOR COMPRISING: (A) A TUBE BUNDLE CARRYING A MEDIUN TO BE COOLED, (B) A SHELL ENCLOSING SAID TUBE BUNDLE AND HOLDING LIQUID AND VAPOROUS REFRIGERANT, SAID SHELL HAVING A LOWER PORTION THEREOF, HOLDING A POOL OF SAID LIQUID REFRIGERANT, (C) A CONDUIT COMMUNICATING THE UPPER PORTION OF SAID SHELL HOLDING VAPORIZED REFRIGERANT WITH SAID LOWER SHELL PORTION HOLDING LIQUID REFRIGERANT, (D) MEANS IN SAID CONDUIT FOR RECEIVING VAPOROUS REFRIGERANT FROM THE EVAPORATOR UPPER PORTION, AND FORMING A HIGH VELOCITY VAPOROUS STREAM THEREOF FOR INTRODUCTION TO LIQUID REFRIGERANT CONTAINED IN THE EVAPORATOR.

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