Foods and beverages: apparatus – Cooking – Boiler or deep fat fryer type
Patent
1994-04-06
1995-12-19
Scherbel, David
Foods and beverages: apparatus
Cooking
Boiler or deep fat fryer type
99404, 126391, A47J 3712
Patent
active
054760348
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to an oven for frying food products in hot oil, comprising a tank in which the frying oil can be accommodated, a gas-fired heating device connected to a heat exchanger which is situated in the tank and through which the smoke gases flow, and also an outlet for the smoke gases emerging from the heat exchanger. Such ovens are used for factory production of food products such as schnitzels, pre-fried chips, etc. They generally have a conveyor belt through which the frying oil can pass and by means of which the food products are conveyed continuously through the hot frying oil.
A heat exchanger, comprising a number of heat exchange pipes, is provided in the tank in order to heat the frying oil. These pipes preferably extend over as large a part of the tank as possible, in order to heat the oil uniformly in this way. Nevertheless, the part of each heating pipe closest to the heating device has a relatively high temperature. Particularly if the inner wall of this part of the heating pipes is directly exposed to the gas flame supplied by the heating device, there is a risk of the oil film on the pipes becoming too hot. The oil is cracked as a result, so that harmful products are formed. It will be clear that the formation of such harmful products is unacceptable.
The remaining greater part of the heat exchange pipes obtains its heat from the smoke gases flowing through it. However, the temperature of the smoke gases has already fallen greatly, particularly near the end of the pipes, which adversely affects uniform heating of the oil in the tank.
SUMMARY OF THE INVENTION
The object of the invention is therefore to provide an oven of the type described above in which a more uniform heating of the oil in the tank is ensured, in such a way that excessively high local temperatures in the oil are avoided. This object is achieved through a bypass pipe connected to the outlet being provided for conveying at least a part of the outlet smoke gases back through the heat exchanger. According to the invention, the already cooled smoke gases obtained at the outlet are mixed with the smoke gases supplied directly by the heating device, which are still at a relatively high temperature. The mixture formed has a lower temperature, as a result of which overheating of the oil can be prevented.
Mixing in a part of the smoke gases also results in the flow velocity in the heat exchange pipes increasing. A higher flow velocity increases the turbulence in the flow, which has a beneficial effect on the heat transfer. This means that an acceptable temperature level can also be maintained in the oil in the part of the heat exchange pipes lying further downstream.
The admixture of smoke gases thus ensures a more uniform temperature distribution in the oil.
A further advantage of the invention is that a part of the heat present in the smoke gases is recovered. The heating device goes into operation only when the temperature of the oil becomes too low. The new, hot smoke gases formed in the process represent an additional volume which is discharged through the outlet in the form of cooled smoke gases.
In the case of the known gas-fired heating device a gas burner with an open flame is generally used. The oxygen from the environment is used for maintaining the combustion. As already mentioned, this known design has the disadvantage that the first part of the heat exchange pipes becomes too hot. A further disadvantage is the fire risk associated with the open flame. In these respects a further improvement can be obtained in the case of the device according to the invention by providing in the tank, below its nominal oil level, a first chamber into which both the bypass pipe and a flame tube, which is connected in a sealing manner to a gas burner, are connected, which chamber is also connected to the heat exchanger. The gas flame is now not directly in contact with the walls of the chamber flushed by the oil, but with the flame tube. This further reduces the risk of overheating the oil. The ga
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Brinson Patrick F.
Koppens Machinefabriek B.V.
Scherbel David
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