Direct liquid refrigerant supply and return system

Abstract

A refrigerant system in which liquid halocarbon compound refrigerant is delivered at pressures in excess of evaporation pressure through metering outlets in a supply header of an evaporator in a manner to provide uniform cooling throughout the evaporator and utilizing a return header and liquid-vapor lift apparatus to return vaporized and unevaporated refrigerant to an accumulator-separator of the refrigeration system.

Parent Case Text

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a countinuation-in-part of applicants' application Ser. No. 352,814 filed April 19, 1973 and now abandoned.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention.

This invention relates generally to direct liquid refrigerant systems of various kinds which may be used as the cooling means for ice rinks and the like and relates specifically to a direct refrigerant supply and return system which provides a substantially uniform refrigerant flow through an evaporator having multiple, single pass, parallel heat exchange pipes and which includes a vapor-liquid lift apparatus to enable unevaporated refrigerant to be entrained in the vaporized refrigerant and returned to an accumulator-separator of a refrigeration system.

2. Description of the Prior Art.

Heretofore many efforts have been directed to providing refrigerant systems for use in heat exchange substructures for ice rinks. In the past, secondary or indirect fluid systems were utilized in which indirect cooling of a surface area was primarily accomplished by using a brine based solution as the heat exchange media which had previously been cooled by a separate refrigerant system. In recent years, indirect fluid systems have become outmoded in favor of direct liquid refrigerant systems due to the expense and inefficiencies of the indirect systems.

Direct liquid refrigerant systems have presented problems due to the difficulty of maintaining substantially constant flow at predetermined pressures throughout the heat exchange area of the system. An example of structures in the prior art is U.S. Pat. No. 3,466,892 to Holmsten which discloses a multiple parallel pipe heat exchange system. This patent discloses a centrally fed supply header which supplies refrigerant fluid to a series of parallel pipes that are connected at one end to the supply header and connected at the opposite end to a return header having a central discharge pipe. This structure at ordinary rates of flow does not provide uniform refrigerant flow through the parallel pipes and thus cooling effect fluctuates as the pressure variance causes a change in the temperature gradient of the system. In order for such a system to operate effectively, it is necessary to force the refrigerant through the system at greater pressures and therefore requires a greater refrigerant flow to obtain a more uniform evaporation rate. Further, there has been no effort to insure a steady and uniform return of the unevaporated liquid refrigerant and vapors to the accumulator-separator in order to reduce or prevent slugging of liquid being returned to the refrigeration system. This slugging causes variations of pressure and liquid levels in the system and subsequently these changes of the operating conditions cause a change in the compression inlet pressure and thereby place an irregular load on the compressor and other components.

Other patents, such as U.S. Pat. No. 3,485,057 to Etter el al. disclose systems for use with a multiple pass floor substructure system using an ammonia refrigerant. This type of system is satisfactory for use with inorganic compounds such as ammonia (Refrigerant 717), where the individual pipes are grouped into feed circuits of two or more pipes by means of return bends.

SUMMARY OF THE INVENTION

The present invention includes a supply and return system for use with a halocarbon compound or other refrigerant to provide a direct heat exchange structure for an ice rink or the like. The system has a supply header which is flooded throughout its length and which supplies liquid refrigerant to multiple, parallel, single pass heat exchange pipes through self-cleaning metering valves. The supply header feeds the heat exchange pipes in a diametric relationship to the order in which the heat exchange pipe delivers vapor and unevaporated liquid refrigerant to a return header, thereby providing uniform cooling through the heat exchange area. The system includes a stepped variable capacity return header which maintains substantially constant pressure within the heat exchange pipes and cooperates with a liquid-vapor lift apparatus in such a manner as to allow unevaporated refrigerant to be entrained in the vaporized refrigerant stream and thus return the unevaporated refrigerant to an accumulator-separator of a refrigeration system in an uninterrupted flow with the vaporized refrigerant.

It is an object of the invention to provide a direct, single pass, multiple parallel pipe refrigerant supply and return system of a type which is appropriate for use as the heat exchange substructure in ice rinks.

Another object of the invention is to provide a system which maintains an even distribution of refrigerant at nearly uniform pressures throughout the multiple pipes of the evaporator.

It is a further object of this system to provide metering valves which are self-cleaning and readily replaceable to insure a constant and uniform delivery of refrigerant to the evaporator from the supply header.

It is a further object of this invention to provide a system having a liquid-vapor lift apparatus which allows unevaporated liquid refrigerant to be raised a substantial height as an entrainment in the vapor stream and discharged into the accumulator-separator of a refrigerating system while the liquid flow rate to the supply header remains relatively constant during compressor operation but regardless of changing compressor capacity in response to changing load.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a top plan view of the direct liquid supply and return system and schematically illustrating its relationship to an accumulator-separator of a refrigeration system.

FIG. 2 is an enlarged side elevation of the return header of the system.

FIG. 3 is an enlarged end view thereof.

FIG. 4 is an enlarged fragmentary section taken along the line 4--4 of FIG. 1.

FIG. 5 is an enlarged vertical section of the vaporliquid lift assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENT

With continued reference to the drawing, a refrigerant supply and return system 10 is provided having an evaporator E for use with a conventional refrigeration system 11 of an ice rink or the like 12. As illustrated in FIG. 1, the conventional refrigeration system 11 includes a separating and delivery apparatus or accumulator-separator 13 having a liquid control L and in which vaporized refrigerant is separated from unevaporated liquid refrigerant returning from the supply and return system 10. The separated refrigerant vapor in the accumulator-separator 13 is discharged through a suction line 14 to one or more compressors 15 which compress the vapor and discharge the same through lines 16, oil separator 17, and line 18 to a condenser 19.

If desired, the compressors 15 could be provided with speed change controls; however, two compressors normally are provided with each compressor having a 50% capacity reduction. Thus, a system such as that illustrated in FIG. 1, usually operates at 25%, 50%, 75% or 100% of its capacity depending upon operating conditions. From the condenser the liquid refrigerant is discharged to a receiver 20 and through a line 21 having an expansion control valve 22 to the accumulator-separator 13. The liquid level control L regulates the amount of liquid refrigerant which is discharged from the receiver 20 into the accumulator-separator 13 so that a substantially constant liquid level is maintained therein.

In the preferred embodiment, refrigerant 22 (Chlorodifluoromethane) is used as the direct heat exchange media. In FIG. 1, liquid refrigerant is delivered under pressure by a pump P from the accumulator-separator 13 to a supply pipe 26 having check valve C. The supply pipe 26 carries the liquid refrigerant to the receiving end or inlet 27 of supply header 28. The refrigerant feed to the supply header is substantially constant and at a rate equal to at least full capacity of the evaporator and usually at a greater capacity.

With reference to FIG. 4, the supply header 28 is provided with a plurality of generally upright discharge pipes 29 within each of which is mounted a metering valve 30. Each metering valve 30 includes a body 31 having a vertically disposed tapered bore 32 and a concentric tapered counterbore 33. The tapered bore 32 is threaded for at least a portion of its length and threadedly receives a metering plug 34 having an axial orifice 35 extending entirely therethrough providing communication between the discharge pipe 29 and the counterbore 33. A closure plug 36 is threadedly received within the counterbore 33 to prevent the passage of refrigerant to the exterior of the body 31.

The orifice 35 is of a size to permit a predetermined quantity of liquid refrigerant to pass therethrough at a desired pressure. In order to make certain that the orifice 35 remains open and to make certain that there is no buildup of material which would restrict flow therethrough, a wire insert 37 having outwardly bent ends 38 is inserted within the orifice 35 with such wire insert being slightly longer than the length of the metering plug 34. Liquid refrigerant passing through the orifice causes the wire insert 37 to jiggle or move in a haphazard manner to keep the orifice clean of all materials. The wire insert is of a specific diameter relative to the diameter of the orifice to permit a predetermined quantity of refrigerant to pass through the orifice. It is contemplated that by changing the diameter of the wire within the orifices, the flow of refrigerant can be either increased or further restricted. It is apparent that the metering plug 34 can be easily removed from the body 31 to repair or replace the wire insert 37 or to replace the metering plug 34 with another plug having a different size orifice or wire insert.

The body 31 is provided with an enlargement or boss 39 at one side and such boss has a bore 40 providing communication between the counterbore 33 and the exterior of the body. A heat exchange pipe 41 of the evaporator E is connected to each of the metering valves 30 in communication with the outlet bore 40 and such pipes are situated in a generally parallel relationship and disposed generally perpendicular to the supply header 28.

The heat exchange pipes 41 are equally spaced along the length of the supply header at intervals determined by the effective heat exchange areas required with a spacing of approximately four inches having been found satisfactory for an ice rink. Vapor and unevaporated refrigerant are discharged from the heat exchange pipes into a return or discharge header 42 disposed generally perpendicular to such pipes and generally parallel to the supply header 28.

The return header is of stepped eccentric construction having sections 43, 44 and 45 of progressively larger diameters respectively. These sections are situated along a common upper grade line 46 which runs across the top of each of the sections 43, 44 and 45 and therefore has a stepped increasing lower grade line 47 defined by the bottom of each pipe. This configuration allows for the necessary increase in capacity without pressure increase as the flow is increased as each successive heat exchange pipe discharges into the return header. Also, the stepped lower grade line 47 permits the refrigerant to flow by gravity from sections 43-45 while allowing the heat exchange pipes to enter the return header 42 at a common elevation.

Although the return header is described here as having three sections, any desired number could be used to achieve the same effect. Also, the lower grade line 47 could have a constant slope from end to end.

The evaporated and unevaporated refrigerant which is received by the return header 42 is discharged through a line 48 into a vapor-liquid lift assembly 49. The discharge line 48 is located diametrically opposite the inlet end 27 of the supply header 28 so that all of the refrigerant flow paths are substantially equal in resistance and the pressures within the heat exchange pipes 41 are substantially constant. The lift assembly 49, FIG. 5, includes a vertically positioned elongated generally cylindrical side wall 50 with a bottom wall 51 at one end and a top wall 52 at the other end forming a receptacle for vaporized and unevaporated refrigerant. The return line 48 enters the side wall at a point below the top wall 52. A pair of vertically disposed discharge pipes 53 and 54 extend through the top wall 52 and are welded or otherwise connected thereto. The vertical discharge pipes 53 and 54 are positioned so that their intakes 55 and 56 respectively are below the discharge line 48. The intake 56 of the vertical discharge pipe is positioned below the intake 55 of the discharge pipe 53 with the spacing between such intakes depending upon the quantity of evaporated and unevaporated refrigerant being introduced to the lift assembly 49 from the return header 42.

The vertical discharge pipe 53 normally is smaller in diameter than the pipe 54 and is of a diameter such that when the compressors are operating at minimum capacity, the suction through line 53 withdraws a mixture of vapor having liquid entrained therein at a velocity of not less than 1,000 feet per minute. Such velocity is necessary to insure that the liquid remains entrained in the evaporated refrigerant and does not collect along the inner wall of the vertical discharge pipe and run back into the lift assembly.

When the compressors 15 are operating at minimum capacity, the liquid level in the lift assembly is relatively high and the flow of the liquid-vapor mixture is entirely through the upper discharge line 53 since the suction is not sufficient to withdraw liquid through line 54. As the capacity of the compressor is increased to meet the load demands which cause increased vaporization in the heat exchange pipes, the volume of flow in lines 53 and 54 increases.

At a predetermined compressor capacity, flow through pipe 54 is initiated and a momentary slug of liquid may be discharged therethrough depending upon the relative elevated spacing between inlets 55 and 56 of pipes 53 and 54, respectively. At maximum compressor capacity, the liquid level in the vapor-liquid lift is such that the flow of the liquid-vapor mixture passes through both pipes 53 and 54. In some instances, it may be advantageous to use three or more vertical discharge pipes situated at various levels in the lift assembly.

The purpose of the lift assembly 49 is to raise excess liquid which is not evaporated, with a minimum of pressure penalty, from the rink floor level into the accumulator-separator which usually is much higher because of the structure of the building. Therefore, it is necessary to provide a velocity of flow in one or more of the vertical pipes 53 and 54 under any of the several capacity steps of the compressors such that the velocity in any vertical pipe is not less than 1,000 feet per minute thus providing a vertical movement of unevaporated liquid as an entrainment in the vapor stream. As an example, if the volume of liquid refrigerant delivered to the supply header is 1.5 times greater than evaporation, then at full load, the weight of the unevaporated liquid is equal to approximately 50% of the weight of the vapor, but the volume of the liquid is very small when compared to the vapor volume. The unevaporated liquid refrigerant returned to the accumulator-separator is inversely proportional to the load on the evaporator but is readily moved with the vapor, providing vapor velocity is never less than 1,000 feet per minute.

In the operation of the device, liquid refrigerant is pumped at a constant volume from the accumulator-separator to the supply header 28 under all load conditions. From the supply header the liquid refrigerant is fed to the plurality of heat exchange pipes 41 through the metering valves 30. The orifice 35 of each metering valve and the wire insert therethrough permit a specific quantity of liquid to be fed to each heat exchange pipe at a desired pressure. The wire insert 37, being free to move with the orifice, also functions to prevent the buildup of any material which would tend to restrict the flow through the valves.

Under normal operating conditions, a portion of the liquid refrigerant undergoes a change of state in the heat exchange pipe 41 as heat energy is absorbed from the ice rink or the like 12. Subsequently, both evaporated and unevaporated refrigerant are discharged into the return header 42.

The progressively larger diameters of the stepped eccentric return header allows for the necessary increase in capacity without pressure increase as the flow increases due to the discharge from successive heat exchange pipes.

The unevaporated and evaporated refigerant is discharged from the return header into the vapor-liquid lift apparatus 49. The discharge from the return header is located diametrically opposite the inlet to the supply header so that refrigerant flow paths through the headers and each heat exchange pipe are substantially equal, thereby aiding in maintaining a more uniform heat exchange rate in the evaporator.

The refrigerant discharged into the vapor-liquid lift apparatus is returned through discharge lines 54 and/or 53, in which suction is created by the compressors 15, to the accumulator-separator as a mixture of unevaporated refrigerant entrained in evaportated refrigerant.

Systems of the type described herein usually have two compressors each of which will have 50% capacity reduction, thus a minimum capacity is 1/4 of the total capacity and the system may be operated at 1/4 , 1/2 , 3/4 and full capacity by controls responsive to operating pressure. The pressure differential necessary to generate a desired velocity in the vertical lift pipes is directly proportional to compressor pumping capacity. Thus, at minimum capacity, the liquid level in the lift assembly is relatively high and the vapor with unevaporated liquid refrigerant entrained therein is raised entirely through the upper suction or vertical line 53 at a rate of at least 1,000 feet per minute. At 1/2 capacity, the velocity in the vertical line 53 is increased and the liquid level is lowered, but not sufficient to uncover the vertical line 54. At substantially 3/4 capacity, the vertical line 54 is uncovered and vapor and unevaporated refrigerant flows vertically through both lines 53 and 54 but the sizes have been proportioned so that the velocity in each line is not less than 1,000 feet per minute. At full capacity the liquid level is further lowered because of the increased flow in both of the vertical pipes.

Claims

We claim:

1. A direct liquid refrigerant supply and return apparatus including an evaporator for use with a refrigeration system having an accumulator-separator, said apparatus comprising a supply header having an inlet at one end for receiving pressurized liquid refrigerant from the accumulator-separator, a plurality of heat exchange pipes located substantially parallel with each other and generally perpendicular to the supply header, each of said heat exchange pipes being connected at one end to said supply header, a return header in spaced generally parallel relationship to said supply header, the opposite end of each of said heat exchange pipes communicating with said return header, said return header having discharge means at one end for discharging vaporized and unevaporated refrigerant therefrom, said discharge means being diametrically opposite said inlet to said supply header so that the refrigerant flow paths from the inlet of said supply header through said heat exchange pipes and said return header are substantially of equal resistance, a vapor-liquid lift apparatus including a receptacle for receiving vaporized and unevaporated refrigerant from the discharge means of said return header, at least one discharge pipe having one end extending into said receptacle and the other end communicating with the accumulator-separator, the unevaporated refrigerant being entrained in the vaporized refrigerant within said receptacle, and means for moving the vaporized refrigerant and the unevaporated refrigerant entrained therein to the accumulator-separator at a velocity to maintain the entrainment of the unevaporated refrigerant.

2. The structure of claim 1 including a plurality of metering means carried by said supply header, each of said metering means having a body with a bore and a counterbore concentric with said bore, plug means having a metering orifice removably mounted in said bore, said body having inlet means providing communication between said supply header and said orifice and oulet means providing communication between said counterbore and said heat exchange pipes, and closure means removably mounted in said counterbore, whereby said plug means may be selectively removed from said body when said closure means is removed from said counterbore.

3. The structure of claim 2 including an insert mounted in said metering orifice and being freely movable therein to prevent clogging of said orifice.

4. The structure of claim 1 wherein said return header includes a plurality of sections of progressively increasing diameters eccentrically connected together along a common substantially horizontal upper grade line and a stepped lower grade line, said discharge means being adjacent the larger end of said return header.

5. The structure of claim 1 in which said receptacle includes a vertically disposed generally cylindrical side wall having a top wall and a bottom wall fixed thereto.

6. The structure of claim 1 including a plurality of discharge pipes having ends terminating at different elevations within said receptacle to provide for varying capacities of flow to the accumulator-separator.

7. The structure of claim 6 in which said discharge pipes are of different diameter.

8. The structure of claim 6 in which the pipe for minimum capacity has the least extension into said receptacle and each additional pipe for increased capacity extends further into said receptacle.