GB2164736A - Means for protecting compressors of refrigeration plants and heat pumps - Google Patents

Abstract

A suction collector 14 is used for liquid refrigerants and/or oil on the suction side of one or more compressors of a refrigeration plant or heat pump. To prevent liquid discharges from arriving at the compressor, after it has started, causing impacts, and damaging it, a siphon 22 is provided in the end of the standpipe 12 projecting into the suction collector. The end of the long leg of the siphon is provided with a Venturi diffuser nozzle 24, which sprays the liquid sucked in from the bottom of the suction collector. <IMAGE>

Description

SPECIFICATION Means for protecting compressors of refrigeration plants and heat pumps The invention relates to means for protecting compressors of refrigeration plants and heat pumps against continuous discharges of liquid refrigerants and/or oil.

As described in the German Patent Application no. P 28 45032, an evaporator system of a refrigerator comprises a small deepfreezer compartment and a great main-freezer compartment, as mainiy used for homefridges. In the operation the refrigerant flows to the evaporator of the deep-freezer compartment from the compressor through a condenser and thence to the evaporator of the mainfreezer compartment additionally, and returns to the deep-freezer compartment finally, in which a horizontal collecting receptacle is provided, the bottom of which is normally covered with the liquid refrigerant, while the vaporized refrigerant above it is exhausted to the compressor upwards. Said liquid refrigerant returned from the main-freezer compartment.As soon as the compressor is turned-off, the high pressure of the refrigerant prevailing in the condenser tries to compensate for the low pressure in the evaporators, in a suction pipe, and in the capsule of the compressor. Due to such a pressure rise within the low-pressure portions of the system, particularly within the great volume of the capsule of the compressor a balancing flow of the refrigerant is caused, and forces the liquid refrigerant to the horizontal collecting receptacle from the deepfreezer and main-freezer evaporators, and to the capsule of the compressor additionally, whereby the refrigerant vaporizes and is deposited in the collecting receptacle, resp.

To prevent this balancing flow of refrigerant, which transfers the refrigerant destined for the deep-freezer compartment to the main-freezer compartment in an unwelcome way, after the compressor has been turned-off, so that the main-freezer compartment is continued to be cooled, a shunting tube comprising a throttle and a siphon is arranged between the collecting receptacle and a line bulged and shaped like a C and extending to the evaporator of the main-freezer compartment from the evaporator of the deep-freezer compartment. At the same time the siphon is mounted to the top of the collecting receptacle in a direct juxtaposition to the orifice of the suction pipe extending to the compressor, i. e. on a level being beneath the last curve of the siphon. The lowest point of its last-but-one curve in the opposite direction, however, incides with the bottom of the collecting receptacle.This second curve is yet connected to a third curve of the siphon, the peak of which substantially extends at the level of the top of the collecting receptacle. From this curve the shunting tube falls down to the throttle, the opposite end of which is connected to the before-mentioned C-shaped bulge of the line connecting the two evaporators.

In the operation the normal flow of the refrigerant to the evaporator of the main-freezer compartment from the evaporator of the deepfreezer compartment along the C-shaped bulge causes a negative pressure near the throttle and in the shunting tube, while the compressor brings about a low pressure in the suction pipe, in the upper interior of the collecting receptacle, and in the siphon on the other end of the shunting tube. As a result of the running compressor, the siphon, the shunting tube and the throttle are substantially kept free of the liquid refrigerant. Only small quantities of the liquid refrigerant are able to gather within the second curve of the siphon, and thereby to separate the flow through the collecting receptacle from the flow of the refrigerant through the line connecting the evaporators.

When the compressor turned-off, the before-mentioned balancing flow of the refrigerant is initiated towards the evaporator of the main-freezer compartment from the evaporator of the deep-freezer compartment. At first a portion of the balancing flow penetrates the throttle near the C-shaped bulge of the line connecting the two evaporators, and the siphon subsequently. As the line connecting the evaporators extends up to a level above the siphon and thus above the collecting receptacle too, the entire balancing flow penetrates the throttle, the shunting tube and the siphon up to the collecting receptacle in its further course, while no liquid refrigerant can reach the evaporator of the main-freezer compartment from the evaporator of the deep-freezer compartment.

Consequently, the task of the siphon used in this known refrigeration plant consists in separating the collecting receptacle connected with the compressor through the suction pipe, from the line connecting the evaporators of the deep-freezer and main-freezer compartments in the operation of the compressor, and to communicate them in its inaction.

If such a collecting receptacle substantially horizontal would be filled with the liquid refrigerant up to a level, where the mouth of the suction pie extending to the compressor can be closed, there would be the danger that, with re-starting the compressor, some discharge of the liquid refrigerant is abruptly taken in the suction pipe, and then will impinge on the driving engine of the compressor like a rigid body. In addition to the loud-audible impact the material is excessively loaded, and the life of the compressor would be diminished. Moreover particles of the material knocked loose by the impact are collected by the refrigerant and taken-up in the circulation of the refrigerant thereby.

A cylindrical collector for liquid refrigerant and/or oil is known from U. S. Patent no.

3,698,207, and is connected between an evaporator and the compressor of the refrigeration plant, to prevent excessive discharges of the liquid refrigerant and/or oil from direct entering the compressor. For the same purpose said cylindrical collector is erected, such that its symmetrical longitudinal axis extends in perpendicular, and the standpipe extending to the compressor emanates from its cover vertically upwards, while the line leaving the evaporator is received by the cylindrical collector nearly in the half height of its shell.

Under the action of the gravity the output of the evaporator, i. e. the liquid refrigerant and/ or oil are deposited down on the bottom of the collector, while the associated volatile refrigerant flows to the cover upwards, and is sucked towards the compressor from that point through the standpipe. The standpipe inserted in the cover is elongated by a Ushaped pipe of the same internal diameter in the interior of the collector; the other open end of which pipe is provided close to the underside of the cover. The negative pressure produced by the compressor and transmitted through the standpipe is therefore effective in an annular area near the underside of the cover in the interior of the collector.Condensing refrigerant and/oil which is still supplied to the collector in a volatile state, is consequently able to deposite as drops on the internal cylindrical wall, on the underside of the cover as well as on the U-shaped internal wall of the elongation of the standpipe, which drops run down or fall with their increasing magnitude to the bottom of the collector or to the deepest point of the U-shaped elongation of the standpipe.

For removing the liquid refrigerant and/or oil appearing on the bottom of the collector in this way, a suction pipe of constant diameter is mounted along the cylindrical internal wall of the collector; its lower orifice is close to the bottom of the collector, and its upper orifice is inserted in that leg of the U-shaped elongation of the standpipe, where the standpipe is directly connected. As the cross-section of the elongation available to the flow is decreased by the upper end of the suction pipe within the mentioned leg, an effect of amplifying the suction capacity is caused in addition to the negative pressure caused by the compressor, to draw the liquid refrigerant and/or oil to the area of the cover from the bottom of the collector in opposition to the gravity.

The behaviour of the liquid composed of the refrigerant and/or oil emanating from the upper end of the suction line, however, is essentially determined by the individual suction capacity of the connected compressor.ln the one extreme case, i. e. if the suction capacity of the compressor is high, this liquid is dragged like a continuous beam in the centre of the standpipe towards the compressor by means of the volatile components surrounding the liquid, whereby said beam can be compared with a beam of water emanating from a cock, and bears the internal portions of the compressor as a rigid, compact rod damaging them. Even if the beam of the liquid refrigerant and/or oil should be divided into individual drops, when dragged, such drops impact the internal portions of the compressor in a similar way as grain of shot shooted off, due to their high velocity of flow.In the other extreme case, i. e. when the suction capacity of the compressor will be low, the liquid cannot be driven forward along the standpipe towards the compressor against the gravity; if the liquid consisting of the refrigerant and/or oil emanates from the top of the suction pipe, it will flow down along the outer sheathing of the suction pipe in the opposite direction and be collected in the groove of the U-shaped elongation of the standpipe. As soon as a pool of the liquid has been gathered there, such that its cross-section has been filled-up, the compressor will surge it like a continuous entirety to itself. With respect to the fact its volumn is heavy, it can affect the internal portions of the compressor as injurious means.

In addition to these two discussed extreme cases very unfavorable in operation, the liquid emanating from the top of the suction pipe, as composed of the liquid refrigerant and/or oil, can also act more favorable in response to the power of the compressor. But some uncertainty in the operative response of the known system cannot be excluded because of this dependency. It is the object of the invention therefore, to provide means for spraying the liquid composed of the refrigerant and/or oil, and emanating from a suction collector with some safety before reaching the compressor, thereby being independent of its suction capacity applied to the standpipe.

According to the invention there is provided a siphon within the upper end of the standpipe projecting into the suction collector, whereby the input of the shorter leg of the siphon is an orifice in the wall of the standpipe close to the bottom of the suction collector, and its longer leg extends in the direction of the standpipe towards the compressor and terminates in a Venturi diffusor nozzle, and the curve of the siphon reaches a level substantially above the bottom of the suction collector.

Said inventive means diesrupts any communication between a horizontal suction collector and the standpipe extending to the compressor in the inactive times of the compressor; in case the compressor is operative, the liquid refrigerant and/or oil sucked in this siphon will be sprayed by the Venturi diffusor nozzle within the standpipe, such that the driving engine of the compressor is protected against impacts caused by liquid discharges.

Moreover the Venturi diffusor nozzle amplifies the suction capacity, which can be transferred to the liquid deposited upon the bottom of the suction collector, and thus the suction collector is exhausted in an easier manner.

One embodiment of the invention, as shown in the accompanying drawings, will hereinafter be explained in greater detail by way of example. The most important features are disclosed in the drawings, in which Figures 1 and 2 show a longitudinal section and a cross-section of the suction collector, resp., and of means according to the invention, and Figure 3 shows a cross-section of the Venturi diffusor nozzle.

As shown in Figs. 1 and 2, a vertical standpipe 10 extends from a compressor (not shown) upwards, and its upper end 12 projects into the interior 14 of a suction collector 16. Close to the bottom 20 of the suction collector 16 there is an orifice 18 penetrating the wall of the standpipe 10, so that any liquid refrigerant and/or oil deposited and collected on the bottom 20 can be sucked-off through the orifice 18 and a siphon 26 into the interior 28 of the standpipe 10 towards the compressor.

To avoid that considerable discharges of such a liquid closed in itself will directly reach the compressor and cause impacts thereon, the siphon 26 is provided in the interior 28 of the standpipe 10, and communicates the orifice 18 with a Venturi diffusor nozzle 24 for distributing the liquid discharges sucked in through the siphon 26 into a spray, while entering the interior 28 of the standpipe 10. As used here, the siphon 26 comprises only one curve 22, the position of which is defined by a level above the bottom 20 of the suction collector 16; said level can substantially no more reached by the liquid in the suction collector 16 in the inactive state of the compressor, in which the liquid normally rises from the bottom 20.

At the top of the suction collector 16 a supply 30 is mounted for a connection to evaporators (not shown). Naturally a plurality of compressors can be connected in parallel to the suction collector 16 in a similar arrangement as shown; also those compressors can provide different powers.

In Fig. 3 a section of the Venturi diffusor nozzle 24 is illustrated in detail. The crosssection available to the flow of fluids decreases downstream to the end of the long leg of the siphon 26 and reaches a narrow neck 34, from which the cross-section widens abruptly; downstream the enlargement 36 is joined with a funnel 32, the cross-section of which uniformly increases up to its edge 38 being the output of the Venturi diffusor nozzle 24, which is left by a fine spray of the liquid sucked in through the orifice 18.

The effect of spraying the liquid is initiated within the curve 22 of the siphon 16, whereby eddies are produced due to the sharp variation of the direction of flux.These eddies are subsequently taken along with the liquid stream through the long leg with decreasing cross-sections of the Venturi diffusor nozzle 24 up to the narrow neck 34, where the liquid flow tears open in finest droplets as mist after having arrived at the transient to the enlargement 36. The spaces between the droplets are still increasing downstream, when the droplets pass the funnel 32 with its increasing cross-section available to their flow.

As it is generally known, each refrigeration system can be re-functioned to a heat pump by rather easy measures. But this does not result in any significant modifications of the described embodiment of the invention.

Claims (3)

1. Means for protecting compressors of a refrigeration plant or a heat pump against closed continuous discharges of liquid refrigerant and/or oil comprising a tubular suction collector and one or more standpipes extending from each compressor and projecting into said collector, wherein a siphon is arranged within the upper end of each standpipe, whereby the input of the shorter leg of the siphon is an orifice within the wall of the standpipe close to the bottom of said collector, and its longer leg extends in the direction of the standpipe and terminates in a Venturi diffusor nozzle, while at least one curve of the siphon reaches a level being substantially above the bottom of said collector.

2. Any and every aspect and/or combination of features not otherwise specifically claimed of the apparatus hereinbefore described with reference to and as illustrated by the accompanying diagrammatic drawings.

3. An apparatus substantially as hereinbefore described with reference to and as illustrated by the accompanying diagrammatic drawings.