WO1994001031A1

WO1994001031A1 - Gas-heated oil cooking apparatus

Info

Publication number: WO1994001031A1
Application number: PCT/FR1993/000683
Authority: WO
Inventors: Pierre Charvet
Original assignee: Paul Charvet
Priority date: 1992-07-02
Filing date: 1993-07-02
Publication date: 1994-01-20

Abstract

A gas-heated oil cooking apparatus including a vat (2) with a bottom and side walls (8, 10), a first gas heater (112, 20) arranged in the vat (2) near and above the bottom thereof, and a rear compartment (16) extending over substantially the whole breadth and height of the rear wall (8) of the vat (2). The apparatus further includes a second heater consisting of a heat exchanger (42) arranged substantially in a lower portion of the rear compartment (16), and an opening (141) provided in the lower portion of the rear wall (8) of the vat (2) so that the oil (4) in the vat (2) can fill the lower part of the rear compartment (16), and be further heated by the heat exchanger (42).

Description

Αaz heating oil cooking appliance

Qbiet of the invention

The present invention relates generally to an oil cooking appliance. The invention can be applied in particular to large capacity fryers usable in collective equipment.

In a conventional manner, a large-capacity oil cooking appliance, for example a fryer for collective equipment, is constituted by a substantially parallelepipedal tank open upwards and by a heating means arranged on the bottom of the tank. , a short distance from it. The oil poured into the tank is heated by the heating means and food, for example French fries, contained in a basket can be immersed in hot oil to be cooked. The heating means can be any, but it is generally either electric or gas. The invention relates more specifically to such a cooking apparatus in oil with gas heating. Conventionally, such a gas heating means consists essentially of several heating units arranged one beside the other, slightly spaced from each other. Each heating unit consists of a conventional gas burner and a substantially straight tube. The gas burner is arranged in the vicinity of one end of the tube, in the axis of the latter, such that the flame of the gas burner is formed in the tube and the hot gases of this flame are flow into the tube and exit through the other end of the tube. The tube is generally arranged horizontally above the bottom of the tray of the cooking appliance, so as to be slightly spaced from the bottom of the tray. Of course, the tube passes tightly, in the vicinity of one and the other of its two ends, two side walls

REPLACEMENT SHEET corresponding opposite of the tank. When oil is poured into the tank, the gas burner can be started, the hot gases which thus circulate in the tube heat it and the external wall of the tube which is in contact with the oil heated by therefore this oil. The length of the tube is in fact substantially equal to the horizontal length of the tank, that is to say to the horizontal distance between two opposite side walls of the tank. As this length is not very important, for example around 60 to 120 cm, the hot gases do not remain long in the tube and therefore exit the tube at a temperature which is still excessive, for example around 400 at 500 ° C. It is therefore seen that a significant part of the thermal energy of the flame is lost since it corresponds to the excessive temperature of the exhaust gases. On the other hand, the heating power of the oil remains relatively modest, and therefore, for a given volume of the pan, the quantity of food to be cooked, for example fries, which can be placed in the basket remains relatively low. In fact, if too much food is cooked in the hot oil at once, since in general these foods are cold and can even be frozen, their sudden immersion causes a drop in temperature. oil, this drop in temperature being detrimental to the proper cooking of food.

It has consequently appeared for a long time desirable to be able to constitute a more powerful gas heating means in order to avoid such a drop in oil temperature and / or to cause a faster rise in temperature. For this purpose, it has already been proposed to increase the number of tubes of the gas heating means, because it is well known that the contact surface between the tubes and the oil increases if the number of tubes is increased by reducing their diameters. However, there are two phenomena which greatly limit this possibility of increasing the number of tubes of the gas heating means.

First, if we decrease the diameter of the tube, for example if we make a tube whose inner diameter is less than 50 mm, it is no longer possible to send a flame from a burner which has good qualities into such a tube.

Second, increasing the number of tubes makes the device more difficult to clean. In particular, if the cooking appliance is a fryer, residues of fries fall on the bottom of the fryer pan and on the tubes of the gas heating means, and these residues must be removed. It is understood that this cleaning of the bottom of the fryer tank is all the more difficult to perform manually as a large number of tubes are arranged above and in the vicinity of this bottom of the fryer and that consequently, the space between the tubes becomes all the more weak.

In practice, it has been found that for a fryer whose rectangular bottom of the tank has dimensions of approximately 600 × 800 mm, no more than 8 tubes can be available, each having an internal diameter of approximately 60 mm. For such a configuration, the heating power is not really sufficient.

To increase this heating power, it has also been proposed to have fins inside each tube which increase the heat exchange between the flame and the tube, but this improvement remains insufficient.

To increase the heating power, it has also been proposed to double the number of tubes by arranging eight sets of two tubes each, the two tubes of a set being arranged one above the other. Such an arrangement makes it possible to slightly increase the heating power but has the drawback that the entire gas heating means occupies a significantly greater height and that this makes it more difficult to clean the bottom of the tank. This also increases the quantity of oil and / or decreases the useful volume of the basket.

To increase the heating power, it has also been proposed to produce the tube so that it has a wavy shape in a vertical plane, but such a tube configuration has not been found to be effective, because the increase in length of the tube, and consequently of the contact surface with the oil, remains relatively small and, on the other hand, the pressure drop in the tube increases significantly, which clearly decreases the quality of the flame which passes through the tube.

It is therefore an object of the present invention to provide a gas-fired oil cooking appliance having increased oil heating power without causing a significant increase in the overall volume of the appliance.

Another object of the invention is to provide such an appliance in which the quantity of oil required is only slightly greater than that of a conventional appliance with the same capacity of cooking material, while the heating power of the oil is significantly increased.

Another object of the invention consists in proposing such an apparatus in which the cleaning of the bottom of the tank remains very easy to perform manually.

Another object of the invention is to provide such an apparatus in which the energy efficiency is increased. Summary of the invention

The invention therefore relates to a gas-fired oil cooking appliance comprising: a pan having a bottom and side walls; a first gas heating means arranged in the tank in the vicinity and above its bottom; and a rear compartment which extends substantially over the width and over the height of the rear wall of the tank.

According to a characteristic of the invention, the apparatus further comprises: a second heating means constituted by a heat exchanger, this second heating means being disposed substantially in a lower part of the rear compartment; and an opening in the lower part of the rear wall of the tank so that the oil contained in the tank can fill the lower part of the compartment rear so that it can be further heated by the heat exchanger.

According to a particular embodiment of the invention, the heat exchanger is constituted by a number of vertical tubes which extend between a lower plate and an upper plate, these plates being substantially horizontal, and a distribution chamber which collects the hot gases which exit from the first heating means and which force them to pass through the vertical tubes so as to exit into an upper part of the rear compartment, the oil contained in the lower part of the compartment being able to pass freely through the opening of the rear wall of the tank and which can pass freely around the tubes of the heat exchanger so as to be strongly heated and to be stirred by this heating in order to cause a circulation which causes it to mix with the oil contained in the bac.

Description of the figures

These objects, characteristics and advantages, as well as others of the present invention will be better understood during the detailed description of an embodiment which follows, illustrated by the appended figures among which: FIG. 1 is a sectional view schematic of an oil cooking appliance of the prior art; Figure 2 is a schematic sectional view of another prior art oil cooking appliance; Figure 3 is a schematic sectional view of yet another prior art oil cooking appliance; Figure 4 is a schematic sectional view of yet another prior art oil cooking appliance; Figure 5 is a schematic sectional view of an oil cooking appliance according to the present invention; Figure 6 is a top view of the apparatus of Figure 5; Figure 7 is a schematic sectional view of another embodiment of the invention; and Figure 8 is a diagram for comparing the performance of an oil cooking appliance of the prior art and a similar oil cooking appliance according to the present invention. Description of the embodiments

In Figures 1 to 4 which illustrate the prior art, the elements which have substantially the same function from one figure to another bear the same reference, even if these elements differ somewhat in terms of their shape, this for the sake of to simplify the explanations.

In FIGS. 1 to 4, four embodiments have been shown in a similar manner which have already been envisaged for a cooking appliance in oil with gas heating. In these exemplary embodiments, these devices are fryers for collective use.

In Figure 1 which illustrates the prior art, there is generally a tray 2 of substantially parallelepiped shape, open upwards and intended to contain a certain amount of cooking oil 4. In practice, a cover (not shown) is provided to be able to close the container 2. The container 2 comprises a bottom 6 and side walls 8, 10. A gas heating means is provided in the bottom of the container 2, slightly above the bottom 6. This heating means is constituted by eight heating devices mounted horizontally in parallel so as to occupy substantially the entire surface of the bottom 6. Each heating device is constituted by a tube 12 which extends horizontally above the bottom, to a certain distance from it, and which crosses, at its two opposite ends, the side walls 8 and 10, respectively, of the container 2. On the front side of the fryer, there is a front compartment 14, of general shape the substantially parallelepiped, which extends vertically in front of the wall 10 of the tank 2. On the rear side of the fryer, is disposed a rear compartment 16, of generally substantially parallelepipedal shape, which extends vertically at the rear of the other opposite side wall 8 of the pan 2. In the lower part of the fryer, there is a lower compartment 18, of generally substantially parallelepipedal shape, which extends horizontally below the bottom 6 of the pan 2. A gas burner 20 is arranged opposite the front end 22 of the tube 12 so that the flame 24 of the burner 20 enters the tube 12. This flame and the hot gases which it produces propagate in the tube 12 and the hot gases exit through the other end 26 of the tube 12 and pass into the rear compartment 16 which constitutes a collector of the combustion gases, this collector 16 being connected to a conventional evacuation duct (not shown). To increase the heating power of the oil 4, it is possible to have inside the tube 12 fins 28 which make it possible to increase the heat exchange between the hot gases produced by the flame 24 and the tube 12, the wall of which external is in contact with the oil 4. However, these fins 28 have an efficiency which remains relatively low, and in practice, it is found that the temperature of the exhaust gases at the outlet 26 of the tube 12 is about 450 to 600 ° C, which is a relatively high temperature. Consequently, it can be seen that these outlet gases which are still relatively hot correspond to a significant loss of energy which it would be advantageous to recover in order to be able to increase the heating power of the oil 4. In FIG. 2 which also illustrates the prior art, there is shown a fryer arranged in a similar manner to that of Figure 1, but in which the gas heating means is slightly modified in order to try to increase the heating power of the oil 4 The tube 12 of each heating device of the gas heating means is arranged in a general shape of inverted U. Consequently, the two opposite ends 22 and 26 of the tube 12 are directed downwards and the tube 12 crosses the bottom 6 of the tank 2 in the vicinity of each of its two ends 22 and 26. The rear compartment 16 is slightly modified in the sense that it further extends down to below the outlet 26 of the tube 12, and the lower compartment 18 is consequently reduced by the same amount in its rear part. The burner 20 is arranged vertically so that the flame 24 enters vertically into the tube 12. This arrangement makes it possible to slightly increase the heating power of the oil 4, although the tube 12 has a diameter identical to that of Figure 1, and it is believed that this increase in heating power is due to the presence of the two elbows of the tube 12 which improve the heat exchange between the hot gases produced by the flame 24 and the tube 12. However, this increase of the heating power remains too modest.

In FIG. 3 which also illustrates the prior art, it can be seen that each heating device of the gas heating means is no longer constituted by a single tube 12, as in the case of the examples represented in FIGS. 1 and 2, but is constituted by two tubes 32, 34 which are both in the shape of an inverted U and which are arranged one above the other. Of course, the lower tube 34 has a length less than that of the upper tube 32 in order to be able to be effectively disposed below. Two burners 20, 21 are disposed respectively at the inlet of each of the two tubes 32, 34. This modification makes it possible to slightly increase the heating power of the oil 4 but it has the drawback that it increases the height of the means gas heating and that it reduces the useful volume of the basket 5 by as much or, if one wishes to keep the same useful volume of the basket 5, it increases the quantity of oil 4 required. On the other hand, this modification requires doubling the number of burners, which significantly increases the complexity of the assembly. The increase in efficiency, that is to say the increase in the heating power of the oil 4 remains, however, relatively small.

In Figure 4 which further illustrates the prior art, there is shown another improvement which has been envisaged for such an apparatus for cooking in oil with gas heating. In this variant, each heating device of the gas heating means is constituted by a single tube, as in the cases represented in FIGS. 1 and 2, but this tube has a general shape of inverted U and also has a certain number of 'additional corrugations, formed in a vertical plane, in order to further increase the length of the tube 36. This modification of the shape of the tube 36 does not bring much improvement with regard to the heating power of the oil and also has the drawback of increasing the height of the heating means, as in the case shown in FIG. 3.

In FIG. 5, which illustrates a particular embodiment of the present invention, a gas-heated fryer is distinguished which comprises a certain number of elements which can be formed in a similar manner to the corresponding elements of a conventional fryer such as that which has been described in relation to FIG. 1. In particular, it can be seen that the fryer according to the invention likewise comprises a tank 2 comprising a bottom 6 and opposite side walls 8, 10, a basket 5 intended to contain the food to be cooked, this basket 5 being able to be immersed in the oil 4 poured into the tank 2, a front compartment 14, a rear compartment 16 and a bottom compartment 18. A gas heating means is constituted by a number heating elements. Each of these heating elements of the first heating means can be constituted in any conventional manner, for example in a manner which has been described in relation to FIGS. 1, 2, 3, 4 which illustrate different embodiments of prior art. However, each heating element of this first heating means can preferably be constituted in the conventional manner which has been described in relation to FIG. 1. In this case, the heating means is constituted by eight heating devices mounted horizontally in parallel so as to occupy substantially the entire surface of the bottom 6. Each heating device is constituted by a tube 12 which extends horizontally above the bottom, at a certain distance from it, and which crosses, at its two opposite ends, the side walls 8 and 10, respectively, of the container 2. The characteristics that are more co nstitu e particularly the object of the present invention are those which will be described below. Each tube 12 opens, at its end 26, 'into the rear compartment 16, but more precisely opens into a distribution chamber 40. Above the distribution chamber 40, is disposed a second heating means which is constituted by a heat exchanger 42 which forms a block extending horizontally in the rear compartment 16 so as to occupy horizontally all the space of this rear compartment 16. It follows from this that the rear compartment 16 is divided into an upper part 16A and a lower part 16B, the compartment parts 16A and 16B being separated by the heat exchanger 42. The heat exchanger 42 consists of a lower plate 44, an upper plate 46 and a number of tubes 48 which extend vertically between the lower and upper plates 44 and 46, so that each tube 48 opens down into the distribution chamber 40 and opens ve rs the top in a collector chamber which is in fact constituted by the upper part 16A of rear compartment 16. One or more openings 49 are provided in the lower part of the side wall 8 of tank 2 so that the oil 4 passes through the lower part 16B and fills the space of the heat exchanger 42 which surrounds the vertical tubes 48. The lower plate 44 includes passage holes allowing the oil to pass through it and the upper plate 46 is waterproof to prevent oil from passing into the upper part 16A. It is in fact the upper plate 48 which separates the lower parts 16B and upper 16A. It follows from this that the hot gases coming from the flame 24 exit at the end 26 of the tube 12, pass into the distribution chamber 40, pass through tubes 48 and arrive in the upper part 16A from where they are evacuated in an evacuation duct (not shown). When passing through the tubes 48, these gases impart heat to the oil which surrounds the tubes 48. This oil which surrounds the tubes 48 is relatively confined in a very limited volume and it consequently heats up strongly producing significant mixing effects which result from convection phenomena. These significant movements of the oil at the heat exchanger 42 or in its vicinity, in particular in the lower part 16B (illustrated by arrows in FIG. 5), prevent the accumulation of calcined food debris which, without it , could accumulate in this inaccessible part of the device. It is understood that the heat exchanger 42 significantly increases the amount of heat which is communicated to the oil 4 by recovering a significant part of the amount of heat supplied by the hot gases after they exit the tubes 12. This increases by significantly the heating power of the gas heating means of the device, without however increasing the size of the device since the heat exchanger 42 is housed in a part of the device which is otherwise unused, namely the lower part of rear compartment 16.

In Figure 6, we see the fryer of Figure 5 in top view. It can mainly be seen that the heat exchanger 42 occupies substantially the entire space, in a horizontal plane, of the rear compartment 16.

Figure 7 is a schematic sectional view of another embodiment of the invention in which the tube 112 is an inverted U-shaped tube. The exchanger 142 is arranged relatively low so that its lower plate 144 is substantially at the bottom 6 of the tank 2. The lower plate 144 and the upper plate 146 of the exchanger are sealed, so that the oil 4 can pass around the tubes 148 in the space which separates these two plates 144 and 146, passing to the through an opening 141 formed in the rear wall 8 of tank 2.

In FIG. 8, a graph has been represented which illustrates in a comparative manner, respectively the evolution of the temperature of the oil when immersing a given charge of material to be cooked, respectively using an apparatus according to the present invention (lines solid) ¹ and using a conventional device such as that shown in Figures 1 to 4 (dotted lines). It can be seen that when a large mass of material to be cooked is abruptly immersed in the oil, with a device according to the invention, the drop in temperature of the oil is less rapid (the drop starts at t1 and stops at t2, instead of t3 for a device of the prior art), the minimum temperature of the oil thus reached is higher (165 ° instead of 150 ° for a device of the prior art) and the rise in temperature is faster. This phenomenon results directly from the fact that by using an apparatus according to the present invention, the heating power of the oil is significantly greater. This increase in heating power can be estimated at around 15 to 50% depending on the size of the exchanger 42.

The fact that the oil which is in direct contact with the large number of tubes 48 causes it to heat up very significantly locally, although the temperature of the tubes 48 is lower than that of the tubes 12 since the tubes 48 are located downstream, and this very significant local heating of the oil in the vicinity of the tubes 48 causes energetic movements by convection of the oil located in the lower part 16B of the rear compartment 16, and this oil, thus strongly stirred, mixes rapidly with the oil contained in the tray 2. This energetic mixing avoids fouling of the lower part 16B and of the heat exchanger 42. On the other hand, this energetic mixing also causes an increase in the heat exchange at the level of the tubes 12 because these tubes 12 are in contact with a circulating oil and not with a substantially immobile oil. Finally, this energetic mixing improves homogeneity of the temperature of the oil contained in the whole of tank 2 and causes greater circulation of the oil around the food to be cooked contained in the basket 5, which can have an advantage in terms of their cooking. The invention is not limited to the embodiments which have just been described in relation to FIGS. 5 to 8, but on the contrary encompasses all the modifications or variants which can be envisaged.

Claims

1. A gas-fired oil cooking appliance comprising: a tank (2) having a bottom (6) and side walls (8, 10): a first gas heating means (12, 20) arranged in the tank (2) in the vicinity and above its bottom (6); and a rear compartment (16) which extends substantially over the width and over the height of the rear wall (8) of the tank (2), characterized in that it further comprises: a second heating means constituted by a heat exchanger (42), this second heating means being arranged substantially in a lower part (16B) of the rear compartment (16); and an opening (41) made in the lower part of the rear wall (8) of the tank (2) so that the oil (4) contained in the tank (2) can fill the lower part (16B) of the rear compartment ( 16) so that it can be further heated by the heat exchanger (42).

2. Apparatus according to claim 1, characterized in that the heat exchanger (42) is constituted by a number of vertical tubes (48) which extend between a lower plate (44) and an upper plate (46), these plates being substantially horizontal, and a distribution chamber (40) which collects the hot gases which exit from the first heating means (12, 20) and which forces them to pass through vertical tubes (48) so as to exit into an upper part (16A) of the rear compartment (16), the oil contained in the lower part (16B) of the compartment (16) being able to pass freely through the opening (41) of the rear wall (8) of the tank (2) and being able to pass freely around the tubes (48) of the heat exchanger (42) so as to be strongly heated and to be stirred by this heating in order to cause a circulation which causes it to mix with the oil contained in the tank (2).