DESCRIPTION

In general, the present invention relates to refrigerating machines, which such terms meaning freezers, refrigerators (whether for household or industrial use) for food preservation, ice forming apparatuses or other similar machines operating in accordance with the refrigeration cycle principles (2nd principle of thermodynamics).

As known, such machines exploit the thermodynamic properties of compressible fluids which can be liquefied after reaching certain temperature and pressure conditions.

To this end, these machines comprise an evaporator and a condenser; in the former, the fluid exchanges heat with an environment or a material to be cooled, whereas in the latter the fluid yields heat to the outside environment; the condenser generally consists of a coil tube which, for a better thermal exchange, may be cooled either by water or by forced ventilation.

The circulation of the refrigerating fluid between the evaporator and the condenser is ensured by a compressor which is used for having the fluid passing from a lower pressure in the evaporator to a higher pressure in the condenser.

Between the condenser outlet and the evaporator inlet an expansion valve is provided, which reduces the pressure and temperature related to the enthalpic energy of the fluid (the energy reduction determines a decrease in temperature).

In some of the refrigerating machines taken into account herein there may be more than one evaporator, as in the case of ice forming apparatuses.

In these cases, the refrigerating fluid circuit includes a distributor which splits the fluid flow downstream of the expansion valve and delivers it to the various evaporators.

De facto, this is a two-way or multiple-way fitting that receives the fluid from the expansion valve and directs it to the evaporators downstream thereof; an example of these machines is described in US patent no. 3,766,744 to Morris.

Such machines are rather complex because, in addition to all the parts already mentioned above (evaporator, condenser, etc.), they also include a receiver upstream of the expansion valve, which essentially consists of a tank that accumulates the refrigerating fluid coming from the condenser; the receiver is used for accumulating liquid so as to make the operation of the machine more constant, since it acts for compensating the fluid flow, which changes depending on whether the compressor is on or off. However, ice making apparatus where the condenser is cooled by forced ventilation, may not always operate regularly due to the thermodynamic conditions of the fluid, which change with the air and water temperatures.

In fact, should one evaporator fail, the fluid flow rate may change and lead to fluid temperature and pressure variations, with the risk that the other evaporators will receive a mixture of liquid and gas instead of the required undercooled liquid.

The same happens as the operating conditions related to the compressor on-off cycles vary, since the fluid temperature and pressure conditions downstream of the distributor change over time.

These situations produce internal unbalances in the operation of the apparatus (in practice, some evaporators are more efficient than others), especially in the case ice making apparatus to which the present invention particularly relates.

In fact, the above-mentioned unbalances lead to an uneven quality of the ice produced, whether in the form of cubes or scales, granules or the like.

The present invention therefore aims at improving the state of the art by providing a refrigerating machine, in particular an ice making apparatus having structural and operating features that ensure the regular functioning of the evaporators even when the operating conditions change.

As a corollary of this object, the invention also aims at providing an apparatus having a simplified configuration, even in the case it has a plurality of evaporators.

These objects are achieved by an apparatus having the features set out in the appended claims.

Such features and the advantages deriving therefrom from will become more apparent from the following description of a preferred, though non-limiting, embodiment of the invention, given with reference to the annexed drawings, wherein:

- Fig. 1 is a general diagram of an apparatus according to the invention;

- Fig. 2 shows a detail of the apparatus of Fig. 1;

- Figs. 3 to 5 are respective diagrams showing the trend of some operating parameters of the apparatus illustrated in the preceding drawings.

In the drawings, reference numeral 1 designates as a whole a granular ice forming apparatus according to the invention.

The apparatus 1 comprises a condenser 2 and a plurality of evaporators 3 and 4; the latter are only two in this case, but there may be more of them, as explained hereafter.

The condenser 2 is a known condenser for ice making machines; therefore, for further details reference should be made to the numerous technical and commercial publications on this matter.

It must be pointed out that the apparatus 1 is of the type intended for granular ice production, and therefore the evaporators 3 and 4 are set up accordingly; however, unless otherwise specified, the following description and the appended claims should be understood as being also applicable to any apparatus for the production of ice in cubes, scales or the like.

The apparatus 1 has a linear operating cycle, i.e. it is intended for the continuous production of granular ice, whereas on the contrary ice cubes are produced cyclically by freezing the water in the evaporators during a first step and then detaching the ice cubes during a subsequent step, by warming up the evaporator.

Although the example of the invention taken into consideration herein refers to a continuously operating granular ice making machine, the following should be considered to apply also to cyclically operating machines for producing ice cubes.

Downstream of the evaporators 3, 4 and upstream of the condenser 2, the apparatus 1 also comprises a compressor 5 that processes a refrigerating fluid flow in order to bring it to the appropriate pressure levels for feeding the condenser 2.

Downstream of the latter there is an expansion valve 6, which reduces the pressure of the fluid flowing out of the condenser 2 to the same pressure levels as in the evaporators 3, 4. In this case as well, the compressor 5 and the valve 6 are of the type commonly in use for these applications, and therefore they will not be described any further.

Downstream of the expansion valve 6 there is a two-way distributor 7 and according to the invention, a receiver 8 is arranged there between.

The latter is a tank having adequate capacity according to the flow of refrigerating fluid circulating in the system, thus acting as an accumulator capable of compensating for any flow oscillations related to the compressor operating cycles.

Preferably, as shown in Fig. 2, the receiver 8 is arranged vertically, so as to keep the distributor 7 under a hydraulic head; in addition, according to the preferred embodiment shown in Fig. 2, the distributor 7 must be close to the receiver 8, so that it can make use of all the quantity of liquid coolant present within the receiver 8.

For this reason, in the illustrated example the receiver 8 is connected upstream of the distributor 7 by means of a welded sleeve 9, which de facto is a spacer that allows to keep the distance between the two parts at the minimum.

The distributor 7 is in fluid communication with the evaporators 3, 4 through tubes 11, 12, which must be of a size suitable to ensure an equal distribution of liquid to the evaporators. In this regard, it has already been mentioned that the number of evaporators may be larger than the two taken into account in this example: of course, in such a case the distributor 7 will be appropriate for the number of evaporators in use; it may therefore be different from the simple two-way fitting shown in the drawings, thus featuring a larger number of ways connected to respective conduits.

In this embodiment, the apparatus 1 is completed by an intake line 12 that connects the evaporators 3 and 4 to the compressor 5; in the case of a water-condensed apparatus, it is complemented by a heat exchanger 13. The latter advantageously warms up the refrigerating fluid taken in by the compressor 5, thus improving the operating conditions of the latter.

From a thermodynamic viewpoint, the operation of the apparatus 1 described so far is similar to that of any typical refrigerating machine, i.e. the compressor 5 compresses the refrigerating fluid and delivers it to the condenser 2, at the outlet of which the fluid becomes liquid again and arrives at the expansion valve 6. The latter allows to reduce the pressure of the liquid fluid.

Unlike what happens in the prior art, according to the invention the undercooled liquid is then accumulated in the receiver 8.

The latter ensures a stable pressure of the liquid supplied to the evaporators 3 and 4, thus making the operation thereof regular and balanced; it follows that the ice produced by the apparatus 1 will have a uniform quality over time, notwithstanding the operating cycles of the compressor and any defects or failures of the evaporators.

These results have been confirmed by laboratory tests carried out on linearly operating apparatuses made in accordance with the invention, a diagram of which is shown in Fig. 3 and is commented below.

EXAMPLE 1

The tests were carried out on a water-condensed apparatus containing a charge of approx. 1,150 gr. of R404A refrigerating fluid, wherein two capillaries having a length of approx. 800 mm and an inside diameter of 2 mm branch off from the distributor 7, whereas the upstream receiver 8 consists of a tank having a length of 190 mm and a diameter of 30 mm. The same apparatus was also fitted with a heat exchanger.

1st Test (T air: 21 °C; T water: 15 °C)

The objective of this test is to balance the evaporators; based on the trend over time of the temperature values shown in Fig. 3, it is possible to extract the average values listed in the following table:

Table 1

As can be argued from the above-listed values, there is an optimal match between the temperatures of both evaporators (in the same machine not fitted with the distribution system, the evaporator temperatures were offset by 2-3 °C.)

2nd Test (T air: 32 °C; T water: 18 °C)

The objective of this test is to verify the energy consumption and the ice production at different ambient temperatures.

The temperature trend is substantially equal to that of the previous test; the energy consumption values (energy-power) are shown in Fig. 4 as a function of time; the energy consumption turned out to be 3.5 kW/h.

3rd Test (T air: 32 °C; T water: 18 °C)

Finally the apparatus was tested under intermittent operation by subjecting it to various on-off cycles; for this purpose, the value stabilization times were analyzed with on cycles of 45 minutes and shorter off cycles of 15 minutes.

The results are illustrated graphically in the last drawing (Fig. 5), which shows the transient temperatures in the various points of the apparatus, thus highlighting how both condensation and evaporation occur in a stable manner.

It is apparent from the above description how the apparatus according to the invention achieves the expected object.

Indeed, as confirmed by experimental tests, the operating temperatures of the evaporators 3 and 4 remain aligned over time even when the apparatus operates intermittently; in this respect, it should be pointed out that this occurs with very narrow tolerances of 1°C at most. Such a stable and uniform operation can be attributed to the presence of a refrigerating fluid accumulation volume upstream of the evaporators, represented by the receiver 8; in this regard, the importance of the receiver position downstream of the expansion valve 6 must also be stressed.

Indeed in this manner it contains undercooled liquid only, thereby ensuring a correct supply to the evaporators; on the contrary, in the typical prior art the receiver is located upstream of the expansion valve, so that it may contain both the liquid phase and the gaseous phase in equilibrium of the refrigerating fluid.

However, the apparatus according to the invention also achieves further advantageous effects. In fact, as can be easily understood, the particular arrangement of the receiver 8 allows to use a single expansion valve 6 for all evaporators (in the example described herein the latter are just two, but they may be more); there is no need to employ one valve for each evaporator, as in some known refrigerating machines, thus attaining clear cost benefits when many evaporators are used.

In addition, the refrigerating system as a whole is simpler thanks to a reduction in the number of conduits required for feeding the evaporators, since the latter are not connected each to a dedicated expansion valve.

It must also be stressed that, if one evaporator fails, the expansion valve 6 will adjust the quantity of liquid delivered to the receiver 8 according to the requirements of the other active evaporators: in this manner, the machine will maintain a balanced operation and the compressor 5 will be safeguarded.

Of course, the invention may be subject to many variations with respect to the description provided so far.

As aforementioned, the evaporators may be more than the two shown in the drawings, and therefore also the distributor 7 may have a larger number of ways with respective tubes for connecting it to the evaporators.

The apparatus 1 shown in the first drawing is of course only a schematic and simplified representation; the real apparatus will be more complex and of course will have additional components, such as filters, temperature and pressure sensors, flow meters and any other devices required for ensuring a correct operation and ice production.

It is barely worth mentioning that the apparatus 1 also comprises a control system adapted to handle the various sensors and control elements (switches, thermostats, pressure switches, etc.).

Those skilled in the art will have no difficulties in introducing all these elements, which however will still fall within the scope of the following claims.