GB2160127A - Economizer device for refrigeration apparatus - Google Patents

Abstract

An economiser device for a refrigerator, a heat pump, or other system comprises a centrifugal separating device comprising a housing (20), a rotor (21) rotatably mounted in the housing and a drive means (24) for the rotor for separating gas refrigerant from liquid refrigerant, said housing having an inlet (19), a gas outlet at a generally central portion thereof, a liquid outlet at a peripheral portion thereof, said economiser device further comprising a valve (27A) arranged in a liquid line communicating with said housing and means for controlling said valve in such a way as to maintain the radial dimension of the liquid annulus which in operation builds up in the peripheral portion in said housing, when said liquid line communicates with said housing via said inlet and said controlling means are adapted to control reduction of the flow passage through the valve when the radial dimension of the annulus tends to increase and to control increase of the flow passage through the valve when the radial dimension of the annulus tends to decrease. <IMAGE>

Description

SPECIFICATION An economiser device for a refrigerating machine or the like, and a machine equipped therewith This invention relates to an economiser device for a refrigerating machine or the like.

The invention also relates to a machine equipped with such a device, It has been shown in GB-A-2121155 published on 14th December, 1983 how to build a centrifugal economiser for a refrigeration circuit using a rotor to separate the liquid refrigerant from the gas and a control valve to maintain a ring of liquid around said rotor. This is recalled in Figure 1, which is Figure 3 of GB-A-2121155.

Figure 1 shows a refrigeration circuit with a motor 24 driving a compressor 1 which discharges gas in a condenser 3, a receiver 4 and expansion valve 11 actuated by the superheat of an evaporator 10 connected by pipe 2 to the suction side of the compressor. The invention of GB-A-2121155 relates to the economiser, the liquid flowing through the expansion valve 11 being introduced via an orifice 19 into a stationary housing 20 in which a rotor 21, having blades 22 in this embodiment, is rotatably mounted and driven by a shaft 23 coupled to an auxiliary power source or to the shaft of the compressor 1. It could even be possible to drive it in some instances by using the energy of expansion of the mixture introduced by orifice 19.

Upon rotation of the rotor 21, liquid entering through port 19 is projected to the inner periphery of the housing 20 whereas gas remains in a gasregion surrounding the axis of the rotor and leaves the housing 20 via an orifice 25 connected to a conduit 7. The other end of conduit 7 communicates with an economiser hole 8 of the compressor 1. The hole 8 is then subjected to a pressure which is intermediate between suction and exhaust pressures of the compressor. The orifice 25 opens into the gas-region of the housing 20, and more precisely at the centre of one end wall of housing 20.

A wall of the housing 20 has an orifice 26 connected to the conduit 9 via a conduit 30 and a control device 27 adapted to maintain around the rotor 21 a liquid annulus 28 preferably with an approximately constant radial thickness. The liquid annulus is thus maintained independently of system pressure in housing 20. The pressure can indeed vary to a large extent, for example in a ratio of 1:3, due to the operating conditions in the compressor 3.

A three way valve is located after the expansion valve 11 in the circuit going to the centrifugal device. The third way of the three-way valve 43 is connected to a by-pass 44, the other end of which is connected to conduit 9 between valve 27 and evaporator 10. Normally when the centrifugal separation device is operating, the way of the threeway valve 43 towards housing 20 is open and the way towards by-pass 44 is closed. If the operation of the economiser is to be stopped, the path to bypass 44 is opened and the path towards housing 20 is closed.

Though the above invention is of great interest, it has been found that, in the arrangement shown in Figure 1, when the expansion valve is closed because there is temporarily no call for liquid in the evaporator 10, the annulus 28 disappears quickly for various reasons. The valve 27, though closed, is generally not hermetically sealed; the rotation absorbs a little power which, though small, vaporizes the annulus; and the cavity resonates with the economiser hole and heats. As a result, noise develops, created by the economiser hole resonating in the tube, and, as well, heating of the tube and cavity occurs.

The present invention is directed to an economiser device for a refrigerator, a heat pump, or other system, said economiser device comprising a centrifugal separating device comprising a housing, a rotor rotatably mounted in the housing and a drive means for the rotor for separating gas refrigerant from liquid refrigerant, said housing having an inlet, a gas outlet at a generally central portion thereof, a liquid outlet at a peripheral portion thereof, said economiser device further comprising a valve arranged in a liquid line communicating with said housing and means for controlling said valve in such a way as to maintain the radial dimension of the liquid annulus which in operation builds up in the peripheral portion in said housing.

According to the invention, the economiser device is characterised in that said liquid line communicates with said housing via said inlet and in that said controlling means are adapted to control reduction of the flow passage through the valve when the radial dimension of the annulus tends to increase and to control increase of the flow passage through the valve when the radial dimension of the annulus tends to decrease.

According to a second aspect of the invention, a refrigerator, heat pump or similar apparatus comprising a compressor, an evaporator, an expansion valve and an economiser device in accordance with the first aspect of the invention, arranged between the condenser and the evaporator and connected through a gas conduit to said compressor at a position where an intermediate pressure exists, is characterised in that said expansion valve is mounted downstream of the economiser.

In use, the economiser device according to the invention is mounted upstream of the expansion valve. It has been found that the economiser device solves the noise problems. It is not usually advisable to set the expansion valve between the economiser and the evaporator because the pressure drop is relatively small and the expansion valve does not therefore operate under good conditions. Therefore, in the prior invention of GB-A2121155, the economiser device had its control valve in the liquid outlet, so as to be adapted to be mounted downstream of the expansion valve.

But it has been found that the rotor of the centrifugal economiser can easily build up pressures in the range of a few bars and therefore there is no more objection to putting the expansion valve between the economiser and the evaporator.

Moreover, even at part load conditions, when the economiser pressure becomes equal to intake pressure, there is enough centrifugal built-in pressure to continue to operate the valve so it is not needed to have a short-circuit as shown at 44 of Figure 1.

The invention will be more readily understood from the description hereafter and the accompanying drawings, given by way of non limitative examples and in which: Figure 2 is a schematic diagram of a refrigerating system in accordance with the invention, and Figure 3 is a schematic diagram of a variation in the embodiment of Figure 2.

The device according to the invention will be described primarily by reference to its differences from the device of Figure 1.

Referring now to the drawings, it can be seen that the expansion valve 1 1a is now located between the centrifugal economiser and the evaporator and is, for instance, actuated by the superheat at exhaust of the evaporator. It can also be seen that the control valve 27a is mounted upstream of housing 20, in communication with inlet 19, and is actuated by control line 70, which itself is triggered by a control device or system such as is shown on Figure 6 of GB-A-2121155, and sends liquid into the separating system as soon as the liquid annulus diminishes and even if there is no liquid leaving by the expansion valve ?lea. Thus, even if the expansion valve 11 a is closed, a continuous flow of gas evolving from vaporization of the liquid annulus which is continuously renewed, leaves by tube 7 toward the compressor.Moreover, the valve 27a can be made to assure a constant leak such as by use of bleed ports (not shown) or by less than complete seating in the "closed" condition thereof.

The effect of the leak is that when expansion valve 11a closes, the liquid ring increases until liquid flows toward tube 7. It has been found that a small amount of liquid returning through the economiser line is enough to eliminate the noise created by a resonating economiser line.

An alternative to the constant leak in the valve 27a is shown in Figure 3. In this alternative, the liquid annulus is connected to the tube 7 by means of a tube 71 with a nozzle 72. The pressure around the annulus generates a spray of liquid through the nozzle 72 into the tube 7 and such spray stops the noise.

It should be noted that one incidental advantage of this arrangement is that, in case of opening of the expansion valve, the evaporator is immediately fed with liquid, whereas in the case of Figure 1, there is some time lag due to the time needed to rebuild the liquid annulus if the system has run long enough, without fresh inflow, to make the annulus disappear.

It should be noted that though it is not normally recommended to set the expansion valve between economiser and evaporator due to the low pressure difference which leads to unsteady valve operation unless large and expensive valves are used, a happy consequence of using a centrifugal separating system is that pressure is created in the liquid ring around it and such pressure can easily reach a few bars which brings the expansion valve back into its normal operating range.

It should also be noted that it is not necessary to short-circuit the centrifugal economiser when the economiser hole 8 is brought back to intake pressure (at part load conditions for instance). The pressure built-up by the liquid ring is still there and can, by design, be set at values needed to operate the expansion valve, usually a few bars.

Having disclosed several embodiments of the invention, it will be apparent to those skilled in the art and it is contemplated that modifications and/or changes in the illustrated and described embodiments may be made without departure from the invention.

Claims (7)

1. An economiser device for a refrigerator, a heat pump, or other system, said economiser device comprising a centrifugal separating device comprising a housing, a rotor rotatably mounted in the housing and a drive means for the rotor for separating gas refrigerant from liquid refrigerant, said housing having an inlet, a gas outlet at a generally central portion thereof, a liquid outlet at a periperhal portion thereof, said economiser device further comprising a valve arranged in liquid line communicating with said housing and means for controlling said valve in such a way as to maintain the radial dimension of the liquid annulus which in operation builds up in the peripheral portion in said housing, wherein said liquid line communicates with said housing via said inlet and said controlling means are adapted to control reduction of the flow passage through the valve when the radial dimension of the annul us tends to increase and to control increase of the flow passage through the valve when the radial dimension of the annulus tends to decrease.

2. An economiser device according to Claim 1, wherein a fluid conduit connects the peripheral region of the housing to the first gas conduit and a nozzle is positioned in said fluid conduit.

3. An economiser device according to Claim 1 or 2, comprising means providing a minimum flow passage to the inlet in an extreme closure position of the valve.

4. A refrigerator, heat pump or similar apparatus comprising a compressor, an evaporator, an expansion valve and an economiser device according to any one of Claims 1 to 3, arranged between the condenser and the evaporator and connected through a gas conduit to said compressor at a position where an intermediate pressure exists, wherein said expansion valve is mounted downstream of the economiser.

5. An economiser device, substantially as hereinbefore described with reference to, and as shown in, Figure 2 of the accompanying drawings.

6. An economiser device, substantially as hereinbefore described with reference to, and as shown in, Figure 3 of the accompanying drawings.

7. Any novel feature or combination of features described herein.