GB2344508A - Gas fryer with improved heat transfer - Google Patents

Abstract

A fryer in which the frying vat 1 is provided with partially inclined side walls 5,6 shaped with a plurality of contiguous portions 10,11 which are alternately inclined relative to each other, each pair of contiguous portions being joined either by a respective crest 13 or a respective trough 12, gas burners 3 disposed in a position below and to the side of said vat and capable of generating a flow of burnt gases in heat exchange relationship in particular with said contiguous portions; there is disposed a plurality of plates 15 of an elongate shape in a vertical direction, in heat exchange relationship with said vat, each of said plates being positioned in the vertical passage delimited by two of said contiguous portions having a trough in common. Said plates may be connected to the respective trough by means of a single weld spot 30.

Description

GAS FRYER WITH IMPROVED HEATER The present invention relates to a fryer for frying foods, which is capable of heating the frying oil by means of heat exchange between a flow of greatly heated combustion gases and a vat containing the frying bath to be heated.

Fryers are known, either for domestic use or for use on a large scale, in which the oil is heated by means of the heating effect of one or more suitably shaped armoured electrical resistances which are immersed in the frying bath; that structure suffers from three types of disadvantages; the first depends on the fact that thermal inertia of such resistances is rather high, so that even if the bath is thermostatically controlled, such resistances do not ensure that the bath temperature is sufficiently constant.

The second disadvantage derives from the fact that, after the frying operation, such resistances in turn have to be removed to gain access to the bottom of the cooking vat in order to be able to clean off the layer of oil and the frying residues, and that complicates the design configuration of such resistances.

The third disadvantage relates to the operating cost thereof since the use of electrical power is normally the most expensive way of generating heat.

Fryers are known, particularly for use for communities, in which the bath is heated by a plurality of metal tubes which are permanently immersed in the oil and which are heated by a flow of burnt gases which pass through them in a constant direction.

Those gases originate from one or more atomospheric burners disposed at positions corresponding to the mouth openings of the tubes and the burnt gas from the burners flows through them in the interior thereof over their entire length, in order then to be discharged at the opposite end by means of a suitable chimney.

However, that construction is adversely affected by the fact that the heat output which can be furnished per unit of surface area of those tubes is fairly modest since the entire combustion process is at atmospheric pressure and is thus governed by the draw of the chimney, which obviously cannot be increased beyond precise limits which are due in particular to the dimensions of the various components.

In addition it is also known that such tubes are heated much more towards the section where the burnt gases are introduced than towards the discharge section, for well-known reasons, and thus heating of the bath takes place in a non-uniform manner with obvious detriment to the frying performance.

Gas fryers are also known in which heating of the frying vat is achieved by the combustion of gas by means of suitable burners disposed below and to the side of the vat, which is suitably shaped to permit the maximum surface area over which the gases flow; that case involves using a well-known type of vat which is formed approximately in a V-shape provided with smooth side walls, and pairs of burners which are disposed below and to the side of the side walls in such a way as to increase the area over which the burnt gases produced by the burners flows.

However even vats of that type, although improved in comparison with the foregoing types, do not achieve optimum efficiency in terms of energy and particularly short heating times as required by current operating demands.

There is therefore the need to provide a fryer, in particular for feeding groups on a large scale, which permits a significant increase in the level of energy efficiency and a reduction in the temperature-rise times, while the construction thereof is simple, reliable and utilises the available technologies.

The aim of the present invention is thus to provide a fryer which is heated with burnt gas fumes, being provided with side surfaces formed by distinct vertical portions shaped in such a way as to increase the total surface area capable of intercepting a larger amount of heat contained in the combustion gases; as will be better illustrated hereinafter those surface portions of the vat are"accordion shaped", that is to say with a profile similar to that of the radiators for domestic heating with a liquid capable of transferring heat.

In addition in order further to receive an even greater amount of heat from the combustion gases, disposed between two contiguous portions is an additional reflecting metal plate capable of having flowing thereover the combustion fumes not directly in heat exchange contact with said portions and, thus being heated to an enhanced degree, transmitting by irradiation the heat which is received towards said vat portions which are disposed, even if inclined, in front of the respective metal plate.

A further aim of the invention is to ensure a significant improvement in the uniformity of temperature along the entire external heat exchange surface.

Those aims are also to be achieved by means of simple technologies and materials which are normally commercially available.

According to the present invention there is provided a fryer, in particular for group use, including: a frying vat containing a bath of frying oil or fat and provided with at least one vertical or at least partially inclined side wall; at least one gas burner disposed in a lower and lateral position with respect to said wall and capable of generating a flow of burnt gases in heat exchange relationship with said wall, wherein said wall is shaped with a plurality of contiguous portions which are alternately inclined relatively to each other, each pair of contiguous portions being joined either by a respective vertically disposed crest or by a respective vertically disposed trough.

The invention will be better appreciated from the following description given solely by way of non-limiting example and with reference to the accompanying drawings in which: Figure 1 diagrammatically shows a vertical longitudinal section of a fryer provided with a frying vat according to the invention, a portion of which is shown on an enlarged scale; Figure 2 shows a vertical cross-section of the fryer of Figure 1; Figure 3 shows a frying vat on section line A-A in Figure 2; and Figure 4 is perspective view showing the lower portion of a frying vat in diagrammatic form in accordance with the invention.

Referring to Figures 1 and 2, shown therein is the basic structure of a fryer according to the invention, comprising a vat 1, a bath of oil 2 contained in the vat, a gas burner 3 disposed externally of the vat in a lower and lateral region, and a chimney or flue 4 for heating of said vat and for discharge of the combustion gases.

The lower region of the vat is of a known shape, that is to say in the shape of very narrow"V"afforded by coupling together two lower walls 5 which are mutually symmetrically inclined with respect to the vertical plane, and the upper region of the vat is in the shape of a very wide"V", which is similarly symmetrical, in such a way that there is formed a space 7 defmed laterally by a lower wall 8 of said vat and, on the opposite side, by a wall 9 of said chimney or flue 4 and the upper portion by said respective wall 5 of said upper region of the vat, as moreover is clearly shown in Figure 1.

In accordance with the invention the lower wall 5 of the vat is formed by a continuos succession of portions 10 and 11 which alternately extend inwardly and outwardly from the central profile of the wall, said portions being joined by respective troughs 12 and crests 13 which are also connected in such a way as not to have sharp corner, being disposed vertically.

The aim of such shaping for the lower wall is that of increasing the exchange area capable of being passed over by the burnt gases produced by the subjacent gas burner 3, for the purpose of enhancing thermal efficiency.

In accordance with the present invention that construction can be effectively improved, bearing in mind that, between the inwardly and outwardly extending contiguous portions 10 and 11, there passes a flow of gas which, involving little or no turbulence because of the constraint imposed by said walls, passes over said portions only with the parts thereof which are more outward and thus closer to same, while the more inward part of said flows of gas, without passing over the respective part, flows away, bearing with it the heat contained therein which thus is not put to use.

The invention achieves the desired result by means of the implementation of the positioning of a plurality of heat-radiating plates 15 which are thus substantially metallic, being of an elongate rectangular shape and being disposed with an edge thereof along said troughs 12, while the opposite edge is positioned in the vertical secant middle plane of the dihedron defined by two of said contiguous portions and the respective trough.

It has in fact been proven that those plates succeed in collecting a significant amount of heat by intercepting the flows of combustion gases which flow: -both in the more inward part of the total flow of the gas current which passes within each passage defined by two contiguous, inwardly and outwardly extending portions in angled relationship, and -partially on the outside of said passage.

In the absence of such plates indeed the heat intercepted thereby would be destined to be dispersed together with the more inward part of the flow of gas passing within said contiguous portions; they are thus heated to a high temperature sufficient to produce a heat radiation effect which naturally is directed at least in part towards the wall portions within which said respective plate has been positioned.

It is thus apparent that such thermal radiation effect which involves said portions is added to the direct heating effect due to convection by virtue of the combustion gases, thus increasing the total application of heat to the wall of the vat and ultimately achieving the desired improvement in thermal efficiency.

As regards the ways of fixing the plates, they can be connected using known means to any point or region not only of the frying vat but also of the fryer; however it will be apparent that the most logical solution involves using for example welding to join the vertical aligned edge of each of the plates to the corresponding trough.

However the procedure involved in welding the entire length of the edge of the plate to the respective trough, while it could be implemented, would be found to be very onerous from the point of view of production costs since it would be necessary to implement long and delicate welding operations, probably by hand.

To obviate that problem, it has been found that substantially the same result in terms of thermal radiation can be achieved even without welding all said length of said edge of the plate, but welding only some points thereof, in such a way however as to be sufficient to guarantee sufficient strength in that edge/trough connection.

Indeed, the function of the plate is to heat the vat 1 in particular by radiation, and it is thus virtually irrelevant, from the thermal point of view, whether it is connected more or less extensively to the wall of the vat.

In consideration also of the fact that said discharge gases rise not only in the interior of the passage defined by the adjacent, inwardly and outwardly extending portions, but also on the outside, more specifically in the chimney 4, it is advantageous to improve the present invention by extending the horizontal dimension of said plates by an amount such that the external edges 21,22 and 23 which are illustrated in Figures 1 and 3 project from the plane H which joins the external crests 13 of said angled adjacent portions which are contained in the frying vat.

In that way the heat which otherwise would be for a large part dispersed with the discharge fumes is effectively intercepted, recovered and re-radiated.

The operating principle of the invention will now be clear: in practice the arrangement involves an additional grid of heat-conducting plates along the path of flow of the combustion gases, which however does not impede the gas flow; the grids are heated to an increased degree thereby to a temperature such that they can re-radiate the relevant heat to the adjacent inwardly and outwardly extending portions of the vat.

In addition, advantageously, said blades can be joined to the vat by a limited number of spot welds, preferably a single spot weld 30 as shown in Figure 1 and in the portion thereof shown on an enlarged scale, without compromising the validity of the invention and the effectiveness of the result.

It will be apparent that the best configuration for the purposes of distributing the gases, the capacity and dimension of the chimneys, the dimensions and geometry of said portions and related plates, like all the other components which influence the final result, can be obtained by means of a careful series of easy experiments, all within the scope of the man skilled in the art.

Claims (8)

1. CLAIMS 1. A fryer, in particular for group use, including: a frying vat containing a bath of frying oil or fat and provided with at least one vertical or at least partially inclined side wall; at least one gas burner disposed in a lower and lateral position with respect to said wall and capable of generating a flow of burnt gases in heat exchange relationship with said wall, wherein said wall is shaped with a plurality of contiguous portions which are alternately inclined relatively to each other, each pair of contiguous portions being joined either by a respective vertically disposed crest or by a respective vertically disposed trough.
2. 2. A fryer according to claim 1, wherein there is provided a plurality of plates of elongate shape in a vertical direction, in heat exchange relationship with said vat, each of said plates being positioned in the vertical passage delimited by two of said contiguous portions having a trough in common.
3. 3. A fryer according to claim 2, wherein said plates are exclusively supported by means of a connection to the respective trough in common between two of said contiguous portions.
4. 4. A fryer according to claim 3, wherein said connection is produced by means of continuous welding between an edge of said plate and the respective trough.
5. 5. A fryer according to claim 3, wherein said connection is produced by means of welding of a plurality of weld spots between an edge of said plate and the respective trough.
6. 6. A fryer according to claim 3, wherein said connection is produced by means of a single weld spot between a vertical edge of said plate and a restricted portion of the respective trough.
7. 7. A fryer according to any one of the preceding claims, wherein a plurality of said plates project beyond the geometrical plane which joins the external crests of a plurality of said contiguous portions.
8. 8. A fryer substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.