GB2342569A - Commercial gas fryer - Google Patents

Abstract

A commercial fryer includes a gas burner and a heat exchanger 4 formed from multiple ceramic cones. The combustion gases flow over the cones and back around the sides of the cooking vat to exit 11. The flow is induced by a gas extraction system, and secondary air intake at the burner is control by an adjustable baffle.

Description

COMMERCIAL CATERING FRYING PAN FOR USE WITH GASEOUS FUEL This invention relates to a commercial catering frying pan which is normally incorporated into an appliance termed a commercial catering fryer comprising of either one pan or several pans, a typical example of which is seen in most 'fast food'restaurants where speed of tumaround is essential. This invention is for gas fired applications using town's gas, natural gas or propane gas.

Fat or oil fryers are well known in the catering field and the preferred fuel has always been gas as against electricity. In order to achieve rapid boiling times manufacturers of these appliances have traditionally used heat inputs that have been increased beyond the considerations of efficiency or the running cost. With the introduction of'The rational use of energy'under EC Type Testing, using the BSEN 203 Part 2 Standard for minimum efficiency for fat fryers, this now has to meet a minimum of 50% Net. This has resulted in having to downrate the heat input previously used on some designs and the tumround time has consequently increased.

According to the present invention, based on a typical frying pan size used in this industry and a depth of cooking oil of not more than 153mm, the base of the pan incorporates a"double-pass"type of heat exchanger where the combustion products are induced under negative pressure created by the fan used in the fume extraction system, to heat over 50% more of the surface of the pan than previously utilise. This has resulted in rapid boiling times and efficient operation and lower running costs.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which : Figure 1 shows a general outline of the'double pan'with a cutaway section illustrating the ceramic'cones'and intemal flueways.

Figure 2 illustrates the directional flow of the combustion products and their final exit via the flue spigot.

Figure 3 illustrates the location of the main bumer. The spaces provided ensure the correct ratio of secondary air is introduced.

Figure 4. shows the main burner arrangement.

Referring to Figure 1: The outer skin of the pan is shown as 1.

The inner skin of the pan is angled inwards and is shown as 2.

The bottom of the pan is shown as 3.

A combustion chamber is formed by boltlng on a flanged base plate which is enclosed on three sides. This is shown as 4.

Multiple ceramic cones are mounted on the base plate, shown as 5.

The main burner is shown as 6.

The angled baffle at the end of the combustion chamber is shown as 7.

The lower right hand flue duct is shown as 8.

Entry to this duct is shown as 8a.

The lower left hand flue duct is shown as 9.

Entry to this duct is shown as 9a The triangula shaped duct formed by the angled inner sides with the outside casing which is square sided, provides a continuous duct along each side and the end where the flue exit duct is located. This duct is only shown in part detail, the cutaway portions left for clarity. This upper duct is shown as 10 and the left hand duct is identical.

Entry to these ducts is the same as shown on the right hand side as 10a.

The rear duct has the flue spigot fitted, shown as 11.

Referring to Figure 2: The combustion products travel first to the rear of the combustion chamber shown as 4 by the suction created against the flue spigot by the extraction fan system, over the ceramic cones, 5, which rapidly become red hot to provide radiant heat and considerable turbulence which assists heat transfer.

These hot gases then pass left and right through apertures 8a and 9a then backwards towards the front of the pan where they pass upwards through apertures shown as 10a into the upper ducts shown as 10, eventually to pass out through the flue spigot, 11.

Care must be taken during manufacture, as it is a welded mild steel fabrication from sheet steel, to ensure all tolerances are observed to the sizes given.

The combustion products heat the bottom of the pan and are then carried to the lower sides and rear of the pan without further dilution from any excess of secondary air. This is a problem experienced by other designs. Therefore more heat is available over a larger heated surface, usually more than 50%.

Taking a typical fish and chip range as an example, these have extraction systems for both combustion products and cooking odours fitted which provide a negative pressure to combustion zones. The length of the ducts, number of bends employed plus the flue length to outside air reduce the negative pressure it is usual for the ranges to be"commissioned"in the field, i. e. on site. It is very difficutt for a sub-contractor to"set up"a range to provide the maximum efficiency.

The main consideration is that the suction provided is sufficient to exhaust the fumes. If there is a larger amount of suction against the combustion zone more secondary air will be introduced with a resulting drop in efficiency. As long as the bumer functions and the pilots stay alight the installer leaves any further work to specialists, whose attendance will cost nearly as much as the average installation fee.

The design of pan shown herewith requires not only the amount of secondary air controlled but also the rate which the combustion products are allowed to escape.

This is achieved by the use of a finely adjustable butterfly type'damper'which is fitted after the flue spigot, individually. In the factory during the final testing procedures prior to delivery, it will now be possible to"set up"every range using all the analysing equipment necessary, and to seal the adjustments on completion so that any unauthorised interference can be detected. These adjustments will be correct anywhere, given a set negative pressure in the flue extraction duct. This will ensure the high level of efficiency is maintained and that there will not be the possibility of customer complaints regarding the performance claimed for the appliance at the point of sale.

Figure 3 illustrates the buées location and entry to the combustion chamber, 4. The bumer, shown as 6 has fixed spaces around the top, shown as 12, and the bottom, shown as 13. These spaces are arrived at by experimentation and once decided on, are not changed. There is no provision for adjustment.

Figure 4 illustrates the type of bumer that is effective for this type of application.

It is made from rectangular mild steel section, shown as 14. Screwed into the face of the section are a number of bumer nozzles, shown as 15. These provide a long pencil shaped flame with provision for'root'retention. These are spaced at intervals to ensure prompt cross-lighting.

Such a bumer configeration permits an adequate supply of secondary air to mix with the primary air/gas mixture at the point of ignition. This is more important when taking into account, over 75% of secondary air is required for good combustion and that these bumers have a very high port loading due to the short length and the high heat input. Ribbon bumers or continuous strip bumers are unable to provide sufficient secondary air to the centre of the bumer flame.

The mixing tube is shown as 16. This can be straight or bent as shown. Various injector jets can be used so that the bumer can be used for town's gas, natural gas and propane gas applications.

Claims (2)

1. CLAIMS 1. A pan suitable for commercial catering frying purposes using a depth of cooking oil of approximately 153mm incorporating a double-pass heat exchanger covering the bottom of the pan and the sides to the level of the cooking oil used, the combustion products being induced through negative pressure created through the extraction system, provides more than 50% of additional heated surface with increased efficiency, improved boiling times and reduced running cost.
2. 2. A frying pan constructed in accordance with Claim 1, that is provided with a controlled percentage of secondary air for combustion purposes-to ensure dilution of the gases is maintained to achieve the highest combustion efficiency, by the positioning of a gas burner at the entrance of the combustion chamber, thereby controlling the ingress of all secondary air induced by a negative pressure provided by an extraction fan.

   2. A pan constructed in accordance with Claim 1 that provides a controlled amount of secondary air for combustion purposes with an adjustable rate of flow for the combustion products against a set negative pressure.

   3. A pan in accordance with Claim 2 that can be pre-set at the place of manufacture and taken without further adjustment to the installation site with the minimum of commissioning checks.

   4. A gas burner of the design disclosed in association with the pan described in Claim 3, having long pencil flames and providing above average combustion efficiences when used with town's gas, natural gas and propane gas.

   Amendments to the claims have been filed as follows 1. A frying pan using fat or oil is so constructed that the floor and three sides are heated by combustion products produced by a gas burner mounted in front of the pan, whereby the floor, the two sides and the end being double skinned, forming combustion ducts providing a triple-pass heat exchanger, the hot gases first pass under the floor to the rear, secondly returning to the front, heating the lower sides, then thirdly, returning along each side to the end of the pan where the flue exit spigot is located, the combustion products being under negative pressure, provided by an extraction fan.