US2871680A - Refrigerating apparatus - Google Patents

Description

Feb. 3, 1959 E.- w. zEARFoss, JR 2,871,680

REFRIGERATING APPARATUS Filed July'lz, 1955 2 sheets-sheet 1 FIG.!

INVENTOR.

ELMER ZEARFOSS Jr.

ATTQRNEY FIG.

Feb. 3, v1959 Filed July l2, 1955 'E.-w. ZEARFOSS, JR

, REFRIGERATING APPARATUS 2 Sheets-Sheet 2 INVENTOR.

ELMER W. ZEARFOSS Jr.

ATTORNEY f asemis Patented Feb. 3, 1959 ice The present invention relates to a refrigerating apparatus of the type in which a capillary tube is employed to control the llow of refrigerant from the high pressure side to the low pressure side of the apparatus.

One object of the invention is to produce an improved refrigerating apparatus of the type set forth.

When capillary tubes are employed as stated above, the evaporator circuit must be designed to keep liquid refrigerant from flooding or spilling into the suction line. Conventional llooded type of evaporator construction incorporates refrigerant storage capacity such as to suffice for maximum load requirements while obviating the spillage problem. The practicable configurations of the circuit arel limited, however, and a relatively large quantity of ,refrigerant is required. In the dry expansion or series type of circuit an accumulator is employed at the outlet of the evaporator to trap excess liquid. This expedient results in undesirable peak load and onset cycle performance which reects improper refrigerant distribution and flow control. Furthermore the inclusion of an accumulator creates oil logging problems.

A further object of the present invention is to produce a system wherein all of the foregoing problems are overcome.

More specifically, the object of the invention is to produce a wholly self-regulating refrigerating apparatus in which the amount of refrigerant distributed to the evaporator is automatically controlled by the demand imposed on the evaporator to the end that the evaporator will, at all times, receive asupply of refrigerant which is a function of the refrigerant leaving the evaporator.

A still further object is to produce an improved refrigerating apparatus in which flow control of the refrigerant reaching the evaporator is effected without any moving parts and in a manner which does not appreciably increase the manufacturing cost of the apparatus and whichl involves no maintenance cost whatever.

In most types of apparatus involving use of a capillary tube it is necessary that the refrigerant charge introduced into the sealed circuit be accurately or, at least, very closely estimated. Otherwise, for well known reasons, satisfactory and eflicient operation may become impossible.

It is therefore a kstill further object of the invention to produce an improved refrigerating apparatus in which the quantity of refrigerant introduced into the system is not so critical and need not be accurately predetermined.

In all refrigerating machines, over-rides or extremes of evaporator temperature, be they on the cold or on the warm side are not desirable. In other words, the cycling of the apparatus should be such as uniformly to maintain the desired temperature range or limits.

It is therefore a still further object of the invention to produce an improved refrigerating apparatus which has cycling performance without undue over-ride.

These and other objects are attained by my invention as set forth in the followingspecification and as shown in the accompanying drawings in which:

Figure l is a diagrammatic representation of a refrigerating apparatus embodying my invention.

Figure la is a fragmentary and diagrammatic view showing slight modifications which can be made in the apparatus shown in Figure 1.

Fig. 2 is similar to Fig. l, but showing a second embodiment of the invention.

The embodiment of Fig. 1

When a refrigerating cycle begins, compressor 1 delivers compressed gaseous refrigerant to condenser 2 in which the gas is liquefied and delivered to capillary tube 3 which leads to an accumulator 5, either directly, or

through nonrestrictive tube 4. In either case, a mixture of liquid and gaseous refrigerant is delivered to the accumulator. A restrictor 6 leads from the bottom of the accumulator and a restrictor 7 leads from the top of the accumulator and, as can be seen from Fig. l, both of these restrictors lead to the inlet end of an evaporator 8. It will be noted that at this point in the refrigerating cycle, and with a relatively large pressure drop across restrictors 6 and 7, the flow capacity of restrictor 6 will be sufficient to allow the passage of all of the liquid refrigerant which is delivered to the accumulator, as well as some of the ash gas so that tube 7 need only accommodate the remaining flash gas. The flow of liquid refrigerant through the evaporator, refrigerates the latter, and its surrounding, and, as the frost point progressively advances, liquid refrigerant will flow through discharge pipe 9 which is coiled around, or otherwise brought into heat exchange relation as at l@ with the accumulator. At this point in the cycle, the accumulator contains refrigerant gas only and because of the pressure drop across restrictors 6 and 7, the temperature of the accumulator and its contents, is higher than the temperature of pipe 9. Therefore heat will flow via heat exchange l@ from the accumulator to pipe 9. This heat transfer condenses the refrigerant gas in the accumulator, and since the evaporator pressure is not alected by the heat exchange between the accumulator and pipe 9, the condensation of refrigerant gas reduces` the pressure within the accumulator and correspondingly decreases the pressure drop across restrictors 6 and 7. With the pressure in the accumulator thus reduced, liquid refrigerant will not ow out through restrictor 6 at the rate at which it is delivered to the accumulator through capillary tube 3, and therefore liquid refrigerant collects in the accumulator and submerges the lower end, or mouth, of restrictor 6. The diminished flow of liquid refrigerant to the evaporator is reliected by the absence of liquid refrigerant in pipe 9. In the absence of liquid refrigerant in pipe 9, the condensation of refrigerant gas in the accumulator ceases and the now increased pressure within the accumulator will again increase liquid refrigerant to ow, through restrictor 6, to the evaporator until liquid refrigerant again reaches pipe 9 to begin a new cycle.

I have only described the extremes of the cycle, but it will be understood that in practice, moderate variations in the flow of liquid refrigerant at heat exchange 1li of pipe 9, will regulate the ilow of liquid refrigerant through restrictor 6. This between extremes modulation of the cycle is especially effective when the load demand on the evaporator is substantially constant. v

It is thus clear that, for best results restrictors 6 and 7 should be so proportioned that heat exchange effects aside, restrictor 6 will allow adequate flow of liquid ref frigerantto the -evaporator and that the combined impedance of restrictor 6 and 7 shall besuch that the heat transfer potential of heat exchange 10 will be adequate to cause the flash gas component in the accumulator to be reduced to a value whereby the reduced ow of liquid refrigerant through restrictor 6 will result in the accumulation of liquid refrigerant in accumulator 5. It follows from the foregoing that the amount of liquid refrigerant in the accumulator, at any given time, will be a function of the load demand on the evaporator, so that the higher the load demand, the lower the level of liquid in the accumulator, and vice versa.

In designs where load demands are high, heat exchange is also effected by bringing pipe 9 into heat exchange with non-restrictive tube l at ll. In this arrangement, heat exchange 1l supplements the heat exchange at lo. It is also possible to omit the heat exchange at l@ and to use the heat exchange at Il alone. Under still other conditions, it is possible to omit the heat exchange at Il) and the heat exchange at Trl. In this arrangement, the heat exchange at l2 is employed and will exercise sole control of the system as follows: When liquid refrigerant in pipe 9, is brought into heat exchange with capillary 3 at l2, the generation of flash gas is reduced, so that less gaseous refrigerant reaches the accumulator, The reduction of gas pressure in the accumulator decreases the pressure drop'across restrictors 6 and 7 and correspondingly reduces the ow of liquid refrigerant, through restrictor 6 to the evaporator. As a result, only superheated gas will iiow in heat exchange with capillary 3, at l2, and therefore the amount of gaseous refrigerant delivered to the accumulator by capillary 3 will be greatly increased. The resultant increase in the pressure drop across restrictors 6 and 7 will increase the flow of liquid refrigerant from the accumulator to the evaporator, and so on. If it is desired to operate the system under substantially the exclusive control of heat exchange l2, the accumulator should be adequately insulated as, otherwise, changes in ambient temperature will affect the pressure-temperature potential across the accumulator-evaporator circuit.

I am aware that in conventional systems a heat exchange similar to heat exchange l2 has been used, but in these arrangements, the heat exchange referred to only served to improve the eliiciency and to prevent liquid refrigerant from reaching the compressor. As far as I am aware, I am the first to interpose an accumulator between the capillary and the inlet of the evaporator and to use heat exchange l2 as a thermal control mechanism for the iow of refrigerant from the accumulator to the evaporator by modulation of the flash gas developed in the capillary in response to the state of the refrigerant in the suction line. In fact, in its broadest aspect, my invention may be said to consist of accumulator 5, restrictors 6 and 7 and heat exchange l2 because these parts, alone will insure satisfactory operation for most purposes. In other words, the heat exchange at lll, or the heat exchange at ll, need be added when more refined control of the system is indicated.

The embodiment of Fig. 1A

In this embodiment, restrictors 6 and 7 of Fig. l are replaced by restrictive openings l and 16 which are formed near the bottom and near the top, respectively, of a nonrestrictive tube 1d disposed within accumulator 5 which corresponds to accumulator S. In this embodiment, liquid refrigerant, flows into tube ld through lower hole I5 and gaseous refrigerant will flow into tube E4 through upper hole 16.

In cases where practical considerations limit the size and, hence, the restrictive value of openings l5 and 16, an auxiliary restrictor 17 can be provided between tube 14 and the evaporator, to supplement the restrictive action of holes l5 and f6. Preferably, the restrictive yalue of holes 15 and i6 themselves should be suicient to overcome the maximum hydrostatic effects which could be encountered during the operation of the system, to the end that the control of the system may not be materially affected by the variable level of liquid refrigerant in the accumulator.

The parts of this embodiment which have not been specifically described and which are also found in the embodiment of Fig. l have been designated by the prime of the numerals of Fig. l. in this embodiment too, heat exchange 1l may be used alone, or as supplement to heat exchange 10 and both of these heat exchanges may be omitted whereby the system will be operated subject to the control of heat exchange 12 only in the manner set forth in connection with the embodiment of Fig. l.

The embodiment of Fig. 2

In this embodiment the 'accumulator is disposed hori- Zontally to minimize hydrostatic effects and a riser i9 extends upwardly from the top of the accumulator. Extending within riser 19 is a tube 21, the lower open end of which is near the bottom of the accumulator and the upper portion of which is provided with a restrictive hole 22. Tube 2l leads through restrictor 23, to the inlet end of the evaporator. Except for parts 19, 2l, 22 and 23, the remaining parts are the same as those of the embodiment of Fig. l and therefore have been designated by the same numeral with the addition of the letter n to each of said numerals.

It will be apparent from inspection of Fig. 2 that hydrostatic factors are essential to the operation and control of the system. Thus, at the beginning of the refrigeration cycle, the pressure differential between accumulator 5a and the inside of tube 2l by virtue of holes 22, is such as to cause liquid refrigerant to flow lthrough tube 2l. When liquid refrigerant flows through heat exchange lfcz, the gas in accumulator Ea is condensed and the pressure drop across hole 22 is reduced, correspondingly to reduce the llow of liquid refrigerant through tube 2l. The resultant starvation of the evaporator causes superheated gas to ow through heat exchange 10a to increase the pressure differential across hole 22, whereby flow of liquid refrigerant to the evaporator increases and so on. From the foregoing it will be seen that the restrictive action of hole 22 must be correlated to thehydrostatic pressure of the liquid column in tube 21 or vice versa. Restrictor 23 increases the pressure and temperature differential between accumulator 5a and evaporator 8a in the same manner as restrictor 17 does in the embodiment of Fig. la. Since the restrictive action of tube 23'has a dynamic effect, this must be taken into consideration in proportioning restrictive passageway or hole 22, and the height of the column of liquid in tube 21.

In this embodiment too, heat exchanges lla and 12a may be treated as the equivalents of their counterparts in Figs. 1 and la.

What I claim is:

l. In a refrigerating system including a compressor, a condenser, a capillary, a rst conduit, an accumulator, a rst restrictor, an evaporator, and a second conduit in a series flow path for refrigerant, said first restrictor leading from the bottom of said accumulator, asecond restrictor leading from the 'topy of said accumulator toward the inlet of said evaporator, and a heat exchange between said first and said second conduits whereby said heat exchange effects cooling of said first conduit to modulate refrigerant pressure in said accumulator and correspondingly control flow of refrigerant to said evaporator.

2. In a refrigerating system including a compressorcondenser unit, a first conduit, an evaporator, and a second conduit in a series ilow circuit, flow control means comprising; an accumulator, two restrictive outiow passages from said accumulator, said one of said passages leading from the upper portion thereof and said second of said passages leading from the lower portion thereof, said accumulator and said passages being interposed between the outlet of said first conduit and the inlet of said evaporator, and a heat exchange relation between portions ofsaidfirst andy said second conduits, whereby said heat exchange effects cooling of refrigerant flowing in said rst conduit to modulate refrigerant pressure in said accumulator and correspondingly to control flow of refrigerant to said evaporator.

3. The structure recited in claim 2 and further characterized in that said first conduit includes a capillary tube.

4. The structure recited in claim 2 and further characterized in that said restrictive passages are dened by measured openings formed in a tube disposed within said accumulator7 said tube leading to the inlet of said evaporator.

5. The structure recited in claim 4 and further characterized in that a restrictor is interposed between said tube and said evaporator inlet.

6. In a refrigerating system including a compressor condenser unit, an evaporator and a suction line for refrigerant flowing from said evaporator to said unit, ilow control elements comprising; means defining a passage for refrigerant flowing from the outlet of said unit to the inlet of said evaporator, said passage including a capillary tube, a conduit, an accumulator, and a first restrictor disposed in series ow relationship, said first restrictor leading from the bottom of said accumulator, a second restrictor adapted for the ow of refrigerant from the top of said accumulator toward the inlet of said evaporator, and a heat exchange between a portion of said suction line and a portion of said passage, said portion of said passage being upstream of said restrictors, whereby said heat exchange effects cooling of refrigerant flowing in said passage to modulate refrigerant pressure in said accumulator and correspondingly control ow of refrigerant to said evaporator.

7. Refrigerating apparatus of the kind including a compressor and a condenser for supplying refrigerant to a capillary tube, an evaporator and a suction conduit for delivering gaseous refrigerant from said evaporator to said compressor, ow control means comprising; an accumulator disposed to receive a mixture of refrigerant from said capillary, a spaced pair of restrictive outflow ports defining passage for liquid and gaseous refrigerant from said accumulator to said evaporator, and a heat exchange between portions of said suction conduit an said accumulator.

8. In a refrigerating apparatus of the type which includes a compressor-condenser unit, 4au evaporator, and a suction line between said evaporator and said unit, ow control means for modulating the ow of refrigerant towards said evaporator according to temperature changes in said suction line, said flow control means being defined by a passageway having a portion thereof in heat exchange with said suction line, said passageway connecting said unit and said evaporator and including a capillary tube, an accumulator, and two restrictive elements porting spaced regions of said accumulator to said evaporator, and said portion of said passageway being upstream of said restrictive elements.

9. The structure recited in claim 8 and a conduit interposed between said capillary tube and said accumulator.

l0. In a refrigerating system, a flow control combination comprising; a -compressor-condenser unit, a passageway leading from said unit, said passageway including a capillary tube and an accumulator, an evaporator, a suction line between said evaporator and said unit, and two restrictive elements adapted to connect spaced regions of said accumulator with said evaporator, said suction line being in heat exchange with a portion of said passageway; whereby the temperature of said suction line on said passageway modulates the flow of refrigerant toward said evaporator.

References Cited in the le of this patent UNITED STATES PATENTS 2,459,173 McCloy Ian. 18, 1949 2,520,045 McGrath Aug. 22, 1950 2,685,780 Zearfoss Aug. l0, 1954 2,697,331 Zearfoss Dec. 21, 1954 2,719,407 Zearfoss Oct. 4, 1955

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