US3753356A

US3753356A - Means and method for determining the liquid refrigerant charge in a refrigeration system

Info

Publication number: US3753356A
Application number: US00253670A
Authority: US
Inventors: D Kramer
Original assignee: Kramer Trenton Co
Current assignee: Ardco Inc
Priority date: 1972-05-08
Filing date: 1972-05-08
Publication date: 1973-08-21
Anticipated expiration: 1990-08-21

Abstract

Dual sight glass system in the liquid line of a refrigerant circuit. One of the two sight glasses is disposed in the line at a receiver inlet and is inspected to determine the presence of liquid refrigerant in excess of the proper maximum amount. The second sight glass is disposed at the receiver outlet and is inspected to determine whether the liquid refrigerant in the system is insufficient. The latter device and its operation are known by themselves. The refrigerant circuit is hermetically sealed.

Description

United States Paten [191 Kramer Aug. 21, 1973 MEANS AND METHOD FOR DETERMINING THE LIQUID REFRIGERANT CHARGE IN A REFRIGERATION SYSTEM [75] Inventor: Daniel E. Kramer, Yardley, Pa.

[73] Assignee: Kramer Trenton Company, Trenton,

[22] Filed: May 8, 1972 [21] Appl. No.: 253,670

Related US. Application Data [63] Continuation-impart of Ser. No. 73,527, Sept. 18,

1970, abandoned.

[52] US. Cl. 62/56, 62/77, 62/125, 62/292, 62/474 [51] Int. Cl. F251! 49/00 [58] Field of Search 62/77, 56, 81, 125, 62/149, 292, 474; 73/73; 116/117 {56] References Cited UNITED STATES PATENTS 2,325,657 8/1943 Burkness 62/125 2,608,301 8/1952 Graves et a1 62/125 2,844,026 7/1958 Wisehmeyer et a1. 62/125 X 3,108,566 10/1963 Chatlos 62/129 3,150,498 9/1964 Blade 62/81 3,177,929 4/1965 Tennings 165/39 3,225,555 12/1965 Chatlos 62/125 3,525,231 8/1970 Armstrong 62/125 3,545,227 12/1970 Grahl 62/474 Primary Examiner-William F. ODea Assistant Examiner-Peter D. Ferguson Attorney-Albert C. Nolte, Jr. et a1.

[5 7] ABSTRACT Dual sight glass system in the liquid line of a refrigerant circuit. One of the two sight glasses is disposed in the line at a receiver inlet and is inspected to determine the presence of liquid refrigerant in excess of the proper maximum amount. The second sight glass is disposed at the receiver outlet and is inspected to determine whether the liquid refrigerant in the system is insufficient. The latter device and its operation are known by themselves. The refrigerant circuit is hermetically sealed.

8 Claims, 10 Drawing Figures PAIENIEMczn ms.

SHEET 3 BF 3 1 MEANS AND METHOD FOR DETERMINING THE LIQUID REFRIGERANT CHARGE IN A REFRIGERATION SYSTEM This application is a Continuation-in-Part of Ser. No. 73,527 filed Sept. 18, 1970 and now abandoned.

BACKGROUND AND NATURE OF THE INVENTION When a refrigeration system contains an insufficient amount of refrigerant, this condition causes a mixture of liquid and vapor to reach the expansion valve, which then hunts and causes inefficient flooding of the evaporator. In the refrigeration system of an air conditioner this trouble is aggravated as the refrigerant undercharge tends to cause evaporator coil frosting.

When on the other hand there is excessive refrigerant in the system, the refrigerant liquid backs up into the condenser by flooding its tubes and preventing access of the condensing vapor to the tube surfaces. This in turn causes reduction of condenser capacity, excessive head pressure, abnormal wear of the compressor and excess power consumption. Also because refrigerant vapor tends to migrate into the compressor crank case, whenever that case becomes colder than the evaporator, this vapor then enters the compressor lubricant and tends to cause liquid slugging" upon the next start up of the system, thereby'seriously endangering the operating parts of the compressor. This is especially aggravated when there is an excessive charge in the system.

No simple remedy for these several problems has been known up to now, nor has there been a good and simple remedy for detecting an overcharge. Relatively simple remedies have been proposed for detecting an undercharge, but many were quite unsatisfactory. They made use of a refrigerant liquid containing structure usually a receiver vessel or some particular type of duct which is usable also for other purposes, as is known in the art. In several prior systems this structure or receiver has been equipped with numerous sight glasses or valved taps, at various levels, or with a single, vertical sight glass, connected to the vessel at two levels, to determine the level of liquid refrigerant. The chief defect of these prior remedies is that they do not show the presence of an overcharge. Also, points of possible leakage are multiplied and in tapping off system, some of the refrigerant is lost each time the undercharge determination is made.

The danger of leakage can be minimized by a float device in the receiver tank, equipped with magnetic coupling through a thin window in the wall of this tank, to show motion of the float by an outer pointer on a calibrated scale. This variant is not only expensive, but also shares the defect that it will not indicate an overcharge, unless the receiver and the amount of refrigerant therein is relatively large (which, however, leads to useless expense for refrigerant, receiver tank, and installation space).

Still other systems have provided liquid line solenoid valves, heat exchangers, heaters and the like, for example compressor crank case heaters to prevent vapor from migrating into the crank case. Such heaters also vaporize refrigerant liquid that is present in the crank case. While solving one problem, such remedies lead to other service problems.

It is an object of this invention to overcome the disadvantages of the prior art systems by a new method of refrigerant monitoring. It is a further object to provide new, effective and inexpensive apparatus for this purpose.

Briefly described, the new method comprises the steps of observing the condition of flowing refrigerant at the receiver inlet, and separately observing the desirably different condition of the flowing liquid at the receiver outlet. The new apparatus therefore provides a flow-through sight glass unit in the liquid line directly at the receiver inlet and an identically constructed sight glass unit (which however operates very differently). in the liquid line directly at the receiver outlet. The operation of this apparatus, and means for interpreting such operation, will now be described in detail.

DRAWINGS FIG. 1 is a diagrammatic view of a refrigeration system comprising the new dual sight glass unit;

FIG. 2 is a similar view of a modified refrigeration system incorporating the invention;

FIG. 3 shows a detail from FIG. 1, drawn on a larger scale;

FIG. 4 shows another detail desirably used in this system of FIG. 1 or FIG. 2;

FIG. 5 is a fragmentary view similar to FIG. 1 and showing a third embodiment;

FIGS. 6 and 7 are views generally similar to FIG. 5 and showing respectively fourth and fifth embodiments of the present system;

FIG. 8 is a perspective view of a system generally similar to that of the diagram of FIG. 1;

FIG. 9 is a perspective view of a detail from the system of FIG. 8, seen at a different angle; and

FIG. 10 is a perspective view, drawn on a larger scale, of a detail from FIG. 9.

FIG. 1 shows a hermetically closed refrigeration system of a known type having a compressor 10, condenser 12, receiver 14, suction liquid heat exchanger 16, evaporator 18 and thermostatic expansion valve 20. According to the invention,

dual sight glasses

22, 24, both of a type suitable to allow observation of flowing refrigerant, are inserted directly adjacent receiver 14, in its liquid inlet line 26 and liquid outlet line 28, respectively.

As further shown in FIG. 8, condensing unit 12 often is installed in peculiar, elevated or poorly accessible locations, for example on roof R of refrigerator building B. Refrigerant circuit C is illustrated as largely disposed in the building (with evaporators l8, and sometimes with hot gas line H, hot gas check valves G, liquid line L, suction line S and hot gas tee units T, all well known to the art.) The latter details are shown only for complete information, but the elevated position of unit 12 and the precarious nature of access to it is important for this invention. Heretofore it presented a distinct problem.

Receiver 14 and its new dual sight glass system, provided in accordance with the invention, are shown most clearly in FIGS. 9 and 10. These figures also serve to show certain means for installing, operating and servicing the system. Desirably, the new receiver can be of small size, to minimize equipment cost, installing space and refrigerant charge.

Outlet sight glass 24 as illustrated carries a charge diagram Q, a larger view of which is provided in FIG. 4.

As shown in that figure, the chart describes conditions of the fluid (liquid with or without gas) in the inlet sight glass" 22 and in the outlet sight glass 24. Of course it is also possible to utilize a pair of charts, describing these conditions and installed respectively on the inlet and outlet sight glasses. For use in a system of the type of FIG. 1, chart requires the three columns entitled respectively Normal, Short of Charge" and overcharge. For the system of FIG. 2 the chart also requires a further column, shown as and entitled Restricted Filter-Dryer."

In either system, when both sight glasses show the presence of clear liquid, this shows that too much liquid refrigerant is in the system. The liquid flow visible in inlet sight glass 12 should come from an effectively working, unflooded condenser 12, and should therefore be mixed with gas bubbles. Therefore, some of the refrigerant must be removed to remedy the overcharge. For this purpose the serviceman may use a refrigerant tap-off connection (not shown).

If both sight glasses show bubbling fluid, this indicates an undercharge of liquid refrigerant in the system, as already explained. Therefore refrigerant must be added. For the latter purpose, the serviceman removes charging plug F and introduces additional refrigerant from a pressurized supply tank, which he for this purpose, connects to the receiver at point F.

In order to reach point F, particularly in field servicing of larger refrigeration systems where the high side" is above floor level, the serviceman frequently must work from a ladder or lift-truck platform, which of course involves difficulties. Similar difficulties may be encountered when servicing of the unit or recharging it becomes necessary in a so-called Kramer Straddle Unit, known from Kramer US. Pat. Nos. 3,299,658 and 3,498,079: The unit has high-side and low-side parts, connected by refrigerant conduits and supported by structural arms which embrace these conduits therewithin. The Straddle Unit components are mounted on a side wall, by these structural arms; as a result they are often accessible only by a ladder, for example when it becomes necessary to re-charge the Straddle Unit after a slow leak." The servicemans access, by such a ladder, is difficult, and service work from the ladder is well-nigh impossible if he must also carry and control a heavy supply unit for the new charge.

This also applies when the high side is installed on a roof, as shown herein. Here, too, the serviceman may climb a ladder (A) and here he may have to re-charge very substantial amounts of refrigerant. The service work may be relatively simpler than in case of Straddle Units, if he can work from a flat roof, but it still remains difficult. In many such cases the normal equipment for weighing an added refrigerant charge can hardly be raised to the region of filling connection F. The problem is simpler when an entire refrigeration package is installed on a factory floor; servicemen can then work under ideal conditions, as required gages and indicators usually are set up right at the charging stand, and no difficulty is then encountered in weighing the container wherefrom refrigerant is added to the system. These conditions are impossible to obtain in many field installations, including for example such a frequently encountered installation as that of FIG. 8.

Even when plug F is easy to reach, the present system has advantages over the conventional weighing ofthe total refrigerant charge. The reason is that the present system determines the adequacy of the liquid" refrigerant charge, which is most relevant for the usual service problems, considered here.

Heretofore the initial starting of a refrigeration system, as well as the checking up needed from time to time and the refilling of refrigerant in case of trouble due to undercharge were much dependent on guesswork on the part of the serviceman. An outlet sight glass often was provided, or there even were the aforementioned numerous sight glasses or valved tap-off points at different levels, or their other equivalents; such devices allowed determinationof undercharge, but then only tended to induce overcharging of the system. The new dual sight glass system by contrast makes it possible to determine the correct liquid charge neither too much nor too little. It achieves this with even lower equipment cost than was involved in many of the earlier systems. It also achieves the proper determination of the charge in a simple, convenient, and yet exact way. It is not necessary to stop the motors, such as fan motor M, for this purpose. Whatever be the elevation of the refrigerant liquid level LL in receiver 14 above the bottom intake end of liquid outlet pipe 42, the two sight glasses and

chart

22, 24, Q show accurately whether the liquid charge is excessive, correct, or insufficient.

FIG. 2 is identical with the view shown in FIG. 1 with the exception that device 30 is a filter-drier which is both a drier and a liquid receiver and is installed in a vertical down-flow position. The top fitting 32 of the drier 30 functions as the receiver inlet and receives the effluent from the condenser 12. The bottom fitting 34 of the drier is used as the receiver outlet and is connected to the liquid line 28 that connects to the inlet of the heat exchanger 16. The combination of the dual sight glass arrangement with the drier also functioning as a receiver permits the system to have a minimum charge for greater economy and improved compressor protection. The system is more economical because it allows the elimination of the conventional receiver in the system. Moreover, the arrangement provides a positive indication of a plugged drier and furthermore provides for not only an indication of an inadequate charge but also a visual indication of excessive charge.

FIG. 5 shows an arrangement having a condenser 36 which may be integrated with a subcooler 38, and

sight glasses

22 and 24 at the inlet and outlet respectively of said subcooler. In this embodiment when sight glass 24 shows clear, and just before sight glass 22 changes from bubbling to clear, that is a proper charge in the system. Furthermore, if both sight glasses are clear, there is an overcharge. It should be noted that the present arrangement permits the use of a substantial portion of the subcooling coil without the risk of liquid refrigerant backing into the condenser portion of the system causing an overcharge therein.

FIG. 6 is a view of an arrangement similar to that shown in FIG. 5 but additionally having a receiver 40 with the

sight glasses

22 and 24 at the inlet and outlet respectively of the receiver. A condenser 36 and a subcooler 38 are'also present in this arrangement.

FIG. 7 is a view of a receiver 14 tilted toward the outlet standpipe or dip tube 42; The inlet standpipe 44 is shown at the opposite end of the receiver M. The tilting of the receiver 14 reduces the minimum charge required from 20 percent of the total charge which the receiver will hold to 5 percent of the total charge, without in any way affecting the refrigerant holding capacity of the receiver or its functioning in any other respect. This not only minimizes the charge demanded by the receiver, but in so doing also increases the effective capacity of this charge.

What is claimed is:

1. Apparatus for indicating the liquid refrigerant charge in the refrigerant circuit of a refrigeration or air conditioning system of the type having a condenser and expansion means, comprising: a hermetically closed, refrigerant containing structure; first and second sight glass units each providing means for visually observing a flow of fluid through the same, and tubing means for bringing a liquid refrigerant stream discharged from the condenser consecutively through the first sight glass, the said structure, and the second sight glass, to the expansion means.

2. Apparatus as claimed in claim 1, wherein said structure is a receiver.

3. Apparatus as claimed in claim structure is a filter dryer.

4. Apparatus as claimed in claim 1, wherein said structure is a liquid subcooler.

5. Apparatus as claimed in claim 1, wherein said structure is a horizontally elongated tank tilted toward one end, the portion of said tubing connecting to the expansion means being connected to said one end.

6. A method of determining the liquid refrigerant 1, wherein said charge in a hemetically closed refrigerant circuit of a refrigeration or air conditioning system which has, in sequence, a condenser, a liquid refrigerant containing structure, and an expansion means, said method comprising: visually observing the condition of any fluid entering said structure to note a possible overcharge of liquid refrigerant; and visually observing the condition of any fluid leaving said structure to note a possible undercharge of liquid refrigerant.

7. A method of determining the liquid refrigerant charge in a hermetically closed refrigerant circuit which has, in sequence, a condenser, a liquid refrigerant containing structure, and an expansion means, said method comprising: observing whether bubbling liquid enters said structure, to avoid an overcharge of refrigerant; and observing whether clear liquid leaves said structure, to avoid an undercharge of refrigerant.

8. A method of avoiding an overcharge of refrigerant in a refrigerant circuit which has, in sequence, a condenser, a liquid refrigerant containing structure, and an expansion means, said method including: observing the condition of fluid, entering said structure, to determine an overcharge of refrigerant by a clear conditon of said fluid and to determine the absence of such overcharge by a bubbling condition of said fluid.

Claims

2. Apparatus as claimed in claim 1, wherein said structure is a receiver.

3. Apparatus as claimed in claim 1, wherein said structure is a filter dryer.

6. A method of determining the liquid refrigerant charge in a hemetically closed refrigerant circuit of a refrigeration or air conditioning system which has, in sequence, a condenser, a liquid refrigerant containing structure, and an expansion means, said method comprising: visually observing the condition of any fluid entering said structure to note a possible overcharge of liquid refrigerant; and visually observing the condition of any fluid leaving said structure to note a possible undercharge of liquid refrigerant.