WO2008096245A2

WO2008096245A2 - Finger-type evaporator

Info

Publication number: WO2008096245A2
Application number: PCT/IB2008/000270
Authority: WO
Inventors: Anderson Bortoletto; Fernando Luiz Freitas Filho Fernando Luiz Freitas Filho; Rogerio Soares Brisola; William Silva
Original assignee: Whirlpool S.A.
Priority date: 2007-02-05
Filing date: 2008-02-01
Publication date: 2008-08-14
Also published as: WO2008096245A3; BRPI0700228A

Abstract

One describes a finger-type evaporator (1) comprising a substantially cylindrical and elongate main duct (2), through which a flow of cooling fluid flows, and also comprises a plurality of fingers (3) or branches, arranged close to the side surface of the main duct (2) and being in fluid connection therewith. Besides, the evaporator (1 ) comprises flow-diversion elements (4) arranged on the central axles of each finger (3) responsible for directing the flow of cooling fluid of the main duct (2) into the fingers (3), providing equal amounts of fluid in all the fingers (3) associated to the duct (2) and, as a result, the same temperature and the same dimensions of ice pieces produced around the fingers (3).

Description

Title: "FINGER-TYPE EVAPORATOR"

The present invention relates to a finger-type evaporator having internal elements for deviation of cooling-fluid flow into the fingers. Description of the Prior Art Generally speaking, in refrigerators and cooling systems, evaporators are widely applied due to the inherent need to use a device that will remove heat from the medium in which it is inserted.

Usually, in order for this removal of heat to take place, the evaporator is associated to a cooling circuit composed of compressors, condensers, capillary tubes, expansion valves and other adequate devices.

The basis functioning of a circuit with such characteristics takes place in the following way: a compressor raises the temperature of a cooling fluid by raising the pressure provided inside it and forces the circulation of this fluid in the circuit, following a condenser. In the condenser, the fluid, still under pressure, has its temperature reduced by heat exchange, which it makes with the external environment, being then led to an expansion valve arranges before the evaporator. The fluid from the condenser is led to an expansion valve through a capillary tube, undergoing a drop in pressure and temperature, besides the consequent increase, or expansion, of volume, then flowing to the evaporator. Inside this evaporator the fluid that was initially liquid upon coming out to the compressor, changes its state into vapor, thus removing the heat from the medium into which it is immersed.

Closing this circuit, after the fluid has passed through the evaporator, it is led to the compressor, where its state changes from gas to liquid, initiating the cycle again.

The above-described circuit is strongly present in the routine of most people, considering the vast number of individuals who have refrigerators in their homes or in other environments which they attend. Thus, in this broad scenery of daily applications, one can cite, in addition to those already mentioned, the use of a circuit similar to the described one, applied in a machine for making ice.

Typically, in an ice making machine, the evaporator is connected to a number of ice formation places, so that they are directly cooled by the cooling system, these ice formation places being filled with water in this case. When the thickness of the ice produced reaches a predetermined condition, or after a specified period of time, the ice-making machine alters its operation mode to the collection mode. Usually, the collection mode involves an alteration in the valve, so that cooling gases at high temperatures will be directed to the evaporator, until the ice in contact with the evaporator detaches from the ice formation places.

Evaporators with this purpose, for actuation in an ice making machine are known since long ago on the market, an example of the prior art being the object of the patent document US 6,148,621 , which describes an ice making machine provided with an evaporator arranged in vertical position close to a mold having cube-shaped cavities. In this case, the water for making ice fills the mold cavities, which, when the cooling fluid circulates in the evaporator, the heat exchange between this fluid and the water contained in the mold causes the ice to form within the cavities.

Thus, when the ice formation is completed, the pump that supplies water to the mold and the fan that helps in exchanging heat of the compressor are turned off and, as a result, the fluid at high temperature supplied at the compressor outlet does not undergo processes for temperature drop, being supplied to the evaporator in this state. In this way, when the fluid at high temperature flows through the evaporator, the heat transmitted to the ice cubes arranged in the mold is sufficient to detach them from the cavities in which they are inserted, supplying the ice in its final shape to the consumer.

Additionally, the prior art illustrates another type of evaporator for making ice, which is known on the market as a "finger"-type evaporator. In this evaporator, the ice is formed, layer by layer, around its "fingers".

The finger-type evaporator in question comprises a main duct having branches or fingers, which project in the vertical direction from its side surface. These branches are, indeed, small tubes fixed perpendicularly with respect to the main duct by brazing or hot soldering, as this process is also known.

The cooling fluid, in this finger-type evaporator, flows through the main duct, filling the fingers or branches, as it goes through this duct. In this way, since this evaporator has each of its branches soaked with water, the presence of the cooling fluid inside these fingers causes the heat exchange between the fluid and the water, thus forming ice around the branches.

To illustrate this type of evaporator, one can take as an example patent document US 2004/0083753, which relates to an ice making machine comprising a finger-type evaporator substantially S-shaped. For each finger of this evaporator there is an associated ice-mold cavity, so that the water deposited in the cavities will change its state to solid due to the heat exchange carried out by the cooling fluid that flows through this evaporator and, more specifically, the fingers.

The finger-type evaporator of the prior art, in spite of having a relatively simple construction, easy to obtain and apply, still has drawbacks with respect to the maintenance of a homogeneous temperature along the fingers. This occurs because the cooling fluid, in circulating in the main duct of the evaporator under a low pressure, does not fill the fingers uniformly and homogeneously and, as a result, since each finger holds a different amount of cooling fluid, the outer surface of these fingers will also have different temperatures. Thus, with different volumes of fluid and different temperatures, each finger will form around itself ice pieces with different dimensions as well, resulting in irregularity and lack of stability of the process and of the rate of ice production. Therefore, an objective of this invention is to provide a finger- type evaporator that comprises means for guaranteeing homogeneity of distribution of fluid inside the fingers, thus providing pieces of ice with substantially regular sizes. Brief description of the invention The objective of this invention is achieved by means of a finger- type evaporator comprising a main duct capable of leading a flow of cooling fluid and a plurality of protruding fingers arranged sequentially along the extension of the duct, in fluid connection with the duct. The mentioned main duct further comprises flow-diversion elements capable of diverting the direction of the flow of cooling fluid into the fingers.

The fingers, in turn, are arranged perpendicularly with respect to the main duct, are substantially cylindrical in shape and also comprise an opening facing the duct, a side surface and a closing wall opposite the opening. Besides, the flow-diversion elements are aligned with the longitudinal axis of the fingers.

In a first embodiment of this invention, the flow-diversion elements are depressions provided in the portion of the main duct, abut on the opening of the finger and have a rectangular cross-section.

The evaporator, according to a second embodiment of this invention, has its flow-diversion elements in the form of laminar barriers perpendicular to the direction of flow of the cooling fluid and fixed close to the wall of the main duct, in the region abutting on the finger opening. Further, the laminar barriers form a flow-off opening between the lower limit of their height and the closing walls of the fingers.

In addition, in a third embodiment of this invention, the flow- diversion elements are provided in the form of tubular diversion arrangements inside the fingers, these arrangements being folds provided in the body of the main duct. Brief description of the drawings

The present invention will now be described in greater detail with reference to an embodiment represented in the drawings. The figures show: - Figure 1 is a side view of the evaporator of the present invention;

- Figure 2 is a sectional view of a first embodiment of the finger- type evaporator of the present invention;

- Figure 3 is a sectional view of a second embodiment of the finger-type embodiment of the present invention; and

- Figure 4 is a sectional view of a third embodiment of the finger- type evaporator of the present invention. Detailed description of the figures

According to a general embodiment of the present invention, the evaporator 1 comprises a main duct 2, a plurality of branches 3 or flow- diversion fingers and elements 4. Besides, a flow of cooling fluid is conducted by the duct 2 and flows through the fingers or branches 3.

The cooling fluid, before flowing inside the evaporator 1 , passes through a cooling circuit having: (i) at least one compressor for raising the temperature and the pressure of the fluid, making it liquid; (ii) at least one condenser for maintaining the pressure of this fluid still high and lowering its temperature through heat exchange with the environment; (iii) capillary tubes capable of conducting the fluid between the circuit components; and (iv) the evaporator 1 , in which the fluid has its volume expanded, its pressure lowered and its temperature reduced, being capable of removing heat from the medium where it is inserted, this medium being preferably water. Considering a first embodiment of the present invention, illustrated in figure 1 , the main duct 2 of the evaporator 1 has a substantially cylindrical and elongate body, which does not prevent others shapes from being imparted to the main duct 2, as for instance a body comprising an elliptical, triangular, rectangular, trapezoidal or other cross-section. Besides, in this embodiment, since the duct 2 is elongate, it has its body constituted so as to form a horizontal straight line or segment, without this preventing alternative shapes from being implemented for the duct 2 of the evaporator 1 of this invention. For instance, the main duct 2 may be provided in a substantial "S"-shaped form or any other possible shape, depending on the availability of shape or place where the ice pieces are formed.

The fingers or branches 3 are preferably small tubes or cylinders having a closing wall 5, a side surface 7 and an upper opening 6, which is arranged close to the outer surface of the main duct 2. Thus, the branches 3 are not only physically associated to the duct 2, but also in fluid connection therewith, so that the cooling fluid flowing through the evaporator 1 will also be capable of passing through these fingers 3.

These fingers 3 are arranged perpendicular and beneath the duct 2 and in a serial or sequential form, beside each other along the evaporator 1. However, this does not at all prevent other arrangements or shapes designed for the fingers 3 of the evaporator 1of the present invention, depending on the shape which one wished to impart to the ice pieces produced and on the mold or place intended for the ice to form.

For ice formation, one can provide molds having cavities with the shape in which one intends to obtain the ice pieces, and it is important to consider that for each finger 3 there should be an associated cavity. In this way, the fingers 3 are dipped into these cavities, and the heat exchange between the cooling fluid inside the fingers 3 and the water inside the cavities is responsible for the obtainment of the ice pieces. However, instead of molds, the evaporator 1 of the present invention may simply and practically be placed inside a water reservoir, in which the formation of the pieces will occur in a manner similar to the procedure in which the mold is used. The evaporator 1 further comprises flow-diversion elements 4, responsible for the flow path in the main duct 2 into the branches 3. These diversion elements are present not only in this first embodiment of the invention, but also in all the other possible ones, having an important actuation to the effect of achieving the objectives of the invention. As already said before, the finger-type evaporators of the prior art are not capable of forming ice pieces with uniform dimensions, since they do not have means guaranteeing the homogeneous temperature of the fluid deposited in the various fingers. Thus, the present invention proposes a way to guarantee the desired homogeneity in temperature and distribution of cooling fluid in the fingers by means of mechanisms (flow-diversion elements 4).

These mechanisms or flow-diversion elements 4 basically comprise a sort of barrier or obstacle to the flow of cooling fluid. In this way, instead of the cooling fluid having the direction of flow adjacent the upper openings 6 of the fingers 3, as is the case in the prior art, it is necessarily directed into the fingers 3, filling them completely, and then goes along the duct 2 to the next finger 3, where this step will take place again. Thus, it is possible to guarantee that all the fingers 3 will have the same amount of cooling fluid and, therefore, the same temperature, besides the consequent homogeneity in dimensions of the ice pieces formed around the fingers 3. Thus, since the fingers 3 will be completely filled with cooling fluid, the size of the ice pieces will be maximized, generating ice-formation cycles with high yield and uniformity in dimensions of each piece.

In the first preferred embodiment of this invention, the flow- diversion elements 4 are provided in the form of mechanical barriers in the main duct 2, more specifically in the form of small depressions 8 arranged in the portion of the main duct 2 that abuts on the opening 6 of each finger 3, being also aligned with the longitudinal axis thereof, so that, for each finger 3 there is an associated depression 8. In figure 1 , this depression 8 has its cross-section substantially rectangular, but the fact that the depressions 8 have other shapes, such as for example pyramidal shape, implying a triangular cross-section is not restrictive of the protection scope of this invention.

This depression 8 generates an obstruction, decreasing the flow area of cooling fluid exactly on the longitudinal axis of the fingers 3, so that the fluid flowing through the main duct 2 will undergo whirling, being diverted into the fingers 3 so as to fill them.

In a second embodiment of the invention, illustrated in figure 2, another type of flow-diversion element 4 is provided. In this case, instead of a depression 8, the flow is diverted by a laminar barrier 9, the front surface 10 for which for contact with the cooling fluid has a substantially larger area than the side area 11. The barriers 9 are also preferably provided in line with the longitudinal axis of the fingers 3, so as not to occupy considerable portions of its internal volume and be perpendicular to the direction of flow of cooling fluid. In order to allow the flow of cooling fluid through the fingers 3, the laminar barriers 9 are attached close to the surface of the main duct 2 in the region that abuts on the opening 6 of the fingers 3, or close to the upper inner wall of the main duct 2, so that its height will not reach the closing walls 5 of the fingers 3, leaving a flow-off clearance for the cooling fluid to flow off.

Thus, upon passing through the main duct 2, the fluid has its flow directly diverted into the fingers 3, and the flowing-off, upon reaching a new finger 3, has the preceding ones totally filled by with the cooling fluid, since the only passage allowed by the laminar barrier 10 is the small clearance in the lower portion of the fingers 3.

The two embodiments described so far use mechanical barriers acting as flow-diversion elements 4. However, in the third embodiment of this invention another category of mechanism is implemented for diverting the flow of cooling fluid into the fingers 3. More specifically, a tubular diversion arrangement 12 is applied to the main duct 2 so that the cooling fluid will go inside the fingers 3.

Thus, according to a third embodiment of this invention, illustrated in figure 3, the main duct 2 has its structure altered so that it will be possible to use the flow-diversion element 4 in question. This structure is flexible and may be divided into two portions, the first one being defined between each of the fingers 3, having a substantially vaulted or arched shape, and a second one contained within the fingers 3. The tubular diversion arrangement 12 is provided in the second portion of the flexible structure of the duct 2, this arrangement 12 being preferably folds of the duct 2 body or still a sort of knot or interlacing, located beneath the longitudinal axis of the fingers 3, being arranged so as to enable the cooling flow to circulate through a large part of the internal volume of these fingers 3. Other constructions may be designed for the tubular diversion arrangement 12, without it being necessarily a knot or an interlacing.

Thus, considering that all the fingers 3 of the evaporator 1 of this third embodiment have the same knot or interlacing pattern inside them, the temperature for the formation of ice will be made uniform, guaranteeing the achievement of the objectives of this invention.

As can be seen, by means of the flow-diversion elements 4 of the evaporator 1 of the present invention, it is possible to obtain a homogeneous distribution of cooling fluid along the various fingers 3, which implies a uniformity of temperature for making ice" and the production of ice pieces of the same size. Additionally, due to the fact that the fingers 3 are completely filled with fluid at a low temperature, the pieces obtained will have maximized dimensions and the temperatures around the evaporator 1 will be lower.

Examples of preferred embodiments having been described, one should understand that the scope of the present invention embraces other possible variations, being limited only by the contents of the accompanying claims, which includes the possible equivalents.

Claims

1. Finger-type evaporator (1) comprising:

- a main duct (2) capable of conducting a flow of cooling fluid and

- a plurality of projecting fingers (3), arranged sequentially along the duct (2) and in fluid connection with the duct (2); characterized in that the main duct (2) further comprises flow- diversion elements (4) capable of diverting the direction of the flow of cooling fluid into the fingers (3).

2. Evaporator according to claim 1 , characterized in that the fingers (3) are arranged perpendicularly with respect to the main duct (2) and have a substantially cylindrical shape, comprising an opening (6) facing the duct (2), a side surface (7) and a closing wall (5) opposite the opening.

3. Evaporator according to claim 1 , characterized in that the flow- diversion elements (4) are aligned with the longitudinal axis of the fingers (3).

4. Evaporator according to claims 1 , 2 and 3, characterized in that the flow-diversion elements (4) are depressions (8) provided in the portion of the main duct (2) that abuts on the opening (6) of the finger (3).

5. Evaporator according to claim 4, characterized in that the depressions (8) have rectangular cross-section.

6. Evaporator according to claims 1 , 2 and 3, characterized in that the flow-diversion elements (4) are laminar barriers (9) perpendicular to the direction of the flow of cooling fluid and attached close to^' the wall of the main duct (2) in the region that abuts on the opening of the fingers (3), such that the laminar barriers (9) form a flow-off clearance between the lower limit of their height and the closing walls (5) of the fingers (3).

7. Evaporator according to claim 1 , 2 and 3, characterized in that the flow-diversion elements (4) are tubular diversion arrangements arranged inside the fingers (3).

8. Evaporator according to claim 7, characterized in that the tubular diversion arrangements (12) are folds provided on the body of the main duct (2).