CN116981384A - High-efficiency heating equipment - Google Patents

Abstract

A high efficiency heating apparatus for heating fluids and cooking media (such as oil or shortening) within a deep fryer includes a natural ventilation (non-powered) or powered ventilation combustion chamber attached to the exterior surface of the deep fryer.

Description

High-efficiency heating equipment

Technical Field

The present application relates to deep fryers. In particular, the present application relates to a natural draft combustion system for a deep fryer.

Background

Millions of deep fryers are in use worldwide. They are found in almost every restaurant and business kitchen. Deep fryers are designed for the rapid cooking of fried foods including, but not limited to, french fries, chicken slices, fried vegetables, fried fish, fried ice cream, and the like. Deep fryers generally comprise: (1) A cooking vessel or pan in which a cooking medium such as oil or shortening is heated to an appropriate temperature for cooking; (2) Heat sources including gases such as natural gas or propane and electricity; (3) A control system for controlling the amount of heat input to the cooking medium; and (4) a drain system for draining the cooking medium for treatment or filtration and return to the cooking vessel. As with many commercial appliances, the size and shape (i.e., space occupation) of these deep fryers have been standardized to facilitate their design, installation, maintenance, and replacement.

Gas-driven deep fryers often include a conduit and an open box design. The tube deep fryer transfers heat to the oil contained within the cooking vessel through tubing that enters, passes through and exits the cooking vessel. The combustion systems associated with tube deep fryers include natural ventilation kits, pulse combustion and electric burners-all forced and pilot ventilation. The efficiency of the tube fryers can range from about 30% efficiency to about 55+% efficiency, depending on the heat transfer configuration of the combustion system and piping.

However, tube fryers suffer from several disadvantages. The heat exchange tubes are located in the cooking vessel causing cleaning and maintenance problems. The user must brush clean around and under the pipe. In addition, food during cooking can fall onto the heat pipe, burning and burning the food, thereby degrading the cooking oil. Finally, the walls and the pipes of the cooking vessel undergo thermal expansion, but at different rates. As a result, the pipe may crack into and out of the weld seam of the cooking vessel and its surroundings and elsewhere, resulting in leakage and reliability/maintenance issues.

Open box fryers, on the other hand, provide for the transfer of heat or energy from the combustion process through the side walls of the cooking vessel to the oil. The main advantage of an open box deep fryer is that no heat exchange tubes pass through the cooking vessel and are therefore not present in the cooking oil. The open box fryer provides unobstructed access to the interior of the box, thereby making cleaning easier, eliminating degradation of the cooking oil due to scorching, and eliminating reliability problems associated with weld breakage. Open box fryers are generally less expensive to manufacture, easier to clean, and have a longer oil life than tube fryers. As with the tube fryers, the combustion system of the open box fryers ranges from natural ventilation to a type of electricity with similar efficiency. The efficiency of a low cost, conventional naturally ventilated open box fryer is typically about 30% (inefficiency). The efficiency of the high efficiency open box fryer is approximately 55%.

Efficient tube and open box fryers also have drawbacks. Major drawbacks of the high efficiency open box fryers include: the cost of moving hot combustion gases is high due to complex controllers, electrical burners (with forced draft combustion blowers or fans) and infrared burners, as these complex features increase costs and cause reliability and maintenance problems. For high efficiency tube fryers, the heat exchange design becomes more complex using complex tube designs (longer tubes, bends, different cross sections) or fin heat exchangers to extract more energy from the combustion gases.

Accordingly, there is a need for an efficient open box fryer with a simple, reliable and inexpensive natural ventilation combustion system that also accommodates the space occupation of conventional deep fryers.

Drawings

The novel features of the application are set forth in the appended claims. The application itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description when read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a perspective view of a deep fryer according to the present application;

FIG. 2 is a partial cross-section of the deep fryer of FIG. 1 taken at II-II;

FIG. 3 is a partial cross-section of the deep fryer of FIG. 1 taken at III-III;

FIG. 4 is a partial perspective view showing one of the combustion chambers and the right side wall of the deep fryer of FIG. 1;

FIG. 5A is a partial cross-section (from above) of the flame front and burner assembly of the deep fryer of FIG. 1;

FIG. 5B is a partial cross-section (from the right) of the flame front and burner assembly of the deep fryer of FIG. 1;

FIG. 6 is an upward partial perspective view of the combustion chamber, burner and insulating layer of the deep fryer of FIG. 1;

FIG. 7 is a side partial perspective view of a conical combustion chamber, burner assembly and baffle of a preferred embodiment of a deep fryer in accordance with the present application;

FIG. 8A is a partial cross-section (from above) of a radial cone-shaped combustion chamber, burner, flame front and baffle of an alternative embodiment of a deep fryer according to the application;

FIG. 8B is a partial cross-sectional view (from above) of a radial cone-shaped combustion chamber, burner, flame front, and alternate flow fins or vanes of another alternate embodiment of a deep fryer in accordance with the application;

FIG. 9 is a partial cross-section (from the right) of an alternative embodiment of the deep fryer of the application;

FIG. 10 is a partial right side view of an alternative embodiment of a deep fryer according to the present application;

FIG. 11 is a partial cross-sectional view of the deep fryer of FIG. 10 taken along section A-A of FIG. 10;

FIG. 12 is a partial right side view of another alternative embodiment of a deep fryer according to the present application;

FIG. 13 is a partial cross-sectional view of the deep fryer of FIG. 12 taken along section A-A of FIG. 12;

FIG. 14 is a partial right side view showing an alternative embodiment of an electrically driven deep fryer; and

FIG. 15 is a front view of the deep fryer of FIG. 14.

Detailed Description

As used herein, the terms "fryer," "deep fat fryer," "box fryer," "commercial flat bottom fryer," and "floor fryer" have the same meaning and refer to a cooking device that generally has four subsystems, including: (1) a cooking vessel or fryer in which a cooking medium (such as oil or shortening) is heated to a suitable temperature for cooking, (2) a heat source comprising a gas (such as natural gas or propane) and electricity, (3) a control system for selectively controlling the heat input to the cooking medium, and (4) a drain system for draining the cooking medium for processing or filtering and returning to the fryer. Furthermore, as used herein, the terms "container," "cooking container," "open-top pot," and "fryer" have the same meaning and refer to a reservoir in a deep fryer where a cooking medium is located.

As used herein, the term "tube fryer" refers to a deep fryer having a cooking vessel that transfers heat into a cooking medium contained in the cooking vessel by way of a combustion conduit into, through, and out of the cooking vessel. In contrast, as used herein, the term "open box fryer" refers to a fryer that transfers heat or energy from the combustion process to the cooking medium through the side walls of the cooking vessel.

As used herein, the term "gas" refers to natural gas, propane, and all other sources of petroleum and/or flammable combustion. Thus, the term "gas" is not meant to be limiting, but includes any suitable combustion source. Furthermore, as used in this document, the terms "natural ventilation system" and "natural ventilation combustion system" have the same meaning, referring to systems that achieve motive force that causes the flow of combustion gases by a natural pressure differential between the hot gases and the surrounding atmospheric conditions. The buoyancy generated is sufficient to transport the combustion products through the combustion zone and the heat exchange zone without the need for additional pressure or flow control sources, such as blowers or fans.

As used herein, the term "business" refers to all dining venues including, but not limited to, large chain operations and individual operators who sell food directly to consumers.

Problems associated with conventional deep fryers (open deep fryers and tube deep fryers) are addressed by the principles and concepts embodied by the high efficiency heating apparatus of the present application.

Referring to fig. 1 of the drawings, there is shown an open box gas combustion deep fryer 8 according to the present application. Deep fryer 8 includes a metal housing that forms a housing for fry vat 12. The housing 10 preferably includes a left side wall 16, a right side wall 17, a rear wall 18, an angled shelf 11, and a front wall 19. The front wall 19 houses the controller 20 and is preferably removable and/or hinged to allow access to control circuitry and other equipment within the housing 10.

Deep fryer 8 is an open box natural draft (non-powered) gas burning deep fryer. Deep fryer 8 is an efficient, low cost heating device for heating fluids and cooking media, such as oil or shortening. Deep fryer 8 is particularly suited for commercial restaurants to cook and prepare fried foods including, but not limited to, french fries, deep-fried ice cream, chicken slices, deep-fried vegetables, deep-fried fish, and the like.

Although deep fryer 8 may be manufactured in any size, shape, and dimension, depending on the intended use and application, in a preferred embodiment deep fryer 8 does not increase the volume space requirements of a conventional deep fryer. Thus, deep fryer 8 is preferably configured to be mounted within the same "footprint" as a conventional deep fryer. Thus, deep fryer 8 preferably uses between 35 pounds and 50 pounds of cooking oil or other cooking medium. In a preferred embodiment, the input rate to deep fryer 8 is 24.6kW (or 84000 Btu/hr). Alternatively, deep fryer 8 may be configured for industrial and automated applications.

Referring now also to fig. 2 and 3 of the drawings, the fryer box 12 is sized to hold one or more baskets 21 and a cooking medium 22 (e.g., oil or shortening). In the preferred embodiment, deep fryer 8 is a floor-standing fryer in which fryer tank 12 is configured to hold between 35 pounds and 50 pounds of cooking medium 22, with fryer tank 12 having a cooking volume of approximately 14 inches wide, 14 inches long and 6 inches deep. Preferably, the volume of the fry vat 12 is configured to hold two or more food baskets 21.

Alternatively, deep fryer 8 may be configured as a Low Volume Fryer (LVF). In the LVF embodiment, the deep fryer 8 has a smaller excess oil capacity than the preferred embodiment described above. However, in the LVF embodiment, the deep fryer 8 is configured with sufficient oil capacity for the desired cooking load, recovery time, and hold-off (oil consumed during cooking). In the LVF embodiment, the volume of fry vat 12 is preferably capable of holding less than or equal to about 35 pounds of cooking medium 22. The reduction in oil capacity saves oil by reducing waste oil and extending oil life. Reducing oil and oil wastage can save a significant amount of money.

Referring now also to fig. 2-6 of the drawings, fry vat 12 includes a lower chamber 30, a transition section 42, and a cooking section 43. Cooking zone 43 is in fluid communication with transition zone 42 and lower chamber 30. The lower chamber 30 includes opposed front and rear walls 32, 34, opposed left and right walls 36, 38, a bottom wall 39, and a large diameter oil drain 40. Preferably, the front and rear walls 32, 34 and the left and right walls 36, 38 are substantially vertical and straight, while the bottom wall 39 is curved. However, minor variations in the linearity, curvature and orientation of the walls will be considered alternative embodiments and are encompassed by the present application.

The bottom wall 39 forms a cold zone 45 and is configured and dimensioned to allow quick and easy hand cleaning. Cold zone 45 is located below lower chamber 30, cold zone 45 being a relatively cool and quiescent zone compared to the portion of oil in which fry vat 12 is located, cold zone 45 having a set temperature typically in the range of 325°f to 375°f. Collecting food particles in the cold zone 45 is desirable because burnt food can degrade the cooking oil, thereby shortening the life of the oil. Generally, a larger cold zone 45 is preferred, especially for broken products, but practical design constraints (e.g. total volume of tank, energy requirements and minimization of oil volume for cooking process) require that this volume be kept small.

The transition zone 42 includes angled walls 52, 54. Cooking zone 43 includes opposed side walls 44, 46, a front wall 48 and a rear wall 50, side walls 44 and 46 preferably being substantially vertical. The left wall 36 and the right wall 38 of the lower chamber 30 are connected to the respective side walls 44, 46 of the cooking zone 43 by respective angled walls 52, 54 of the transition zone 42. The gas combustion process generates heating of the cooking medium 22 and occurs primarily at the sidewalls 36, 38 of the lower chamber 30. The heated air and other byproducts of the combustion process are in fluid contact with the outer surfaces of the walls 36, 38 of the lower chamber 30.

Deep fryer 8 is an open box deep fryer with a natural ventilation (non-powered) gas combustion system 67. The unpowered natural draft gas combustion system 67 includes a gas supply conduit 72, at least one nozzle 68 in fluid communication with the gas supply conduit 72, an injection port 70 in fluid communication with the nozzle 68, an angled burner 66 in fluid communication with the injection port 70, an inlet air plate 73 connected to the angled burner 66, a combustion chamber 60 in fluid communication with the burner 66, and an igniter 80. Combustor 66 terminates at a combustor face 75, and combustor face 75 may be disposed just inside combustion chamber 60 or near combustion chamber 60 in a manner that allows for a small separation between combustor face 75 and combustion chamber 60. In either configuration, the combustor 66 is in fluid communication with the combustion chamber 60. It should be appreciated that in those embodiments of the present application employing multiple combustion chambers 60 and multiple burners 66, the gas supply conduit 72 may act as a manifold that distributes gas between the multiple combustion chambers 60 and burners 66.

Gas is supplied to a gas supply conduit 72 and then flows through a nozzle 68 to a gas injection orifice 70 where the gas mixes with air and then flows down to the angled burner 66 into an inlet air plate 73 and an igniter 80. The igniter 80 burns the premixed gas to produce a selectively angled flame front 81. To facilitate complete combustion, secondary air is introduced into the combustion process through secondary air openings 74 in the inlet air plate 73. Preferably, deep fryer 8 includes one header 72 on each side of lower chamber 30, with each header 72 serving three nozzles 68, three injection ports 70, three burners 66, three air inlet plates 73, and three combustion chambers 60.

In a preferred embodiment, the lower chamber 30 has a size of about 1.0ft ² -1.5ft ² Left and right walls 36, 38 of the housing, thereby creating a total side heat transfer area of two to three square feet. The required heat input to the left and right walls 36, 38 is achieved by convection and radiation from the combustion system 67, the radiation providing approximately one third of the total heat transfer, while the convection provides the remaining heat transfer. Each of the left wall 36 and the right wall 38 delivers about 5kW to 9kW (or 20000 to 30000Btu per hour) to the cooking oil under heavy cooking conditions.

To further optimize heat transfer, the outer wall of each combustion chamber 60 is covered with one or more layers of high temperature insulation 64. Insulation 64 has a low heat capacity and high heat transfer resistance, but is still compact to fit the volume of space of deep fryer 8. Preferably, the thermal insulation 64 is used to maintain the thermal profile of each combustion chamber 60 such that each combustion chamber 60 does not return to the average wall temperature of the lower chamber 30. The relationship of the secondary heat transfer at a given temperature (e.g., q "(W/m) ²⁾ ＝εδ(T ⁴ s-T ⁴ sur) the return to the average wall temperature of lower chamber 30 substantially reduces radiation to fry vat 12.

Referring now specifically to FIG. 4 of the drawings, one possible method of assembling the combustion chamber 60 is illustrated. The combustion chamber 60 is secured to the left wall 36 and the right wall 38 of the lower chamber 30. Each combustion chamber 60 extends substantially horizontally from front wall 32 to rear wall 34, each combustion chamber 60 having an inlet portion 56 and an outlet portion 58. Each combustion chamber 60 is preferably a C-shaped rectangular housing attached to either the left wall 36 or the right wall 38 of the lower chamber. For example, if only one combustion chamber 60 is used, the combustion chamber 60 would be a three-sided C-shaped housing with the left wall 36 or right wall 38 forming the fourth side when the combustion chamber 60 is secured thereto. In the case of multiple combustion chambers 60 on each side of fryer housing 12, each combustion chamber 60 will have three interior surfaces, with the fourth side being formed by left wall 36 and right wall 38 as described above. Various manufacturing processes may be employed so that multiple chambers may share one inner wall. The rectangular combustion chambers 60 are sealed (except at the inlet and outlet) such that the hot gas flowing through each combustion chamber 60 is confined within such combustion chamber 60. Further, various configurations other than the C-shaped configuration may be used. For example, the combustion chamber 60 may be configured as a semicircular or semi-elliptical chamber with its opening secured to the left or right wall 36, 38.

Each outlet portion 58 of the chamber 60 is in fluid communication with an exhaust conduit or stack 35 (see fig. 1 and 3). In the preferred embodiment, six combustion chambers 60 are secured to the lower chamber 30, three combustion chambers on each of the left wall 36 and the right wall 38. This description is illustrative and not limiting as deep fryer 8 may be practiced with more or less than six combustors 60. For example, fewer and/or smaller combustion chambers 60 may be used with LVF embodiments.

For higher temperature operation and quick response, each combustion chamber 60 is preferably made of thin-walled high temperature metal, such as being both economical and durableAlternatively, a cast ceramic shell or segmented high temperature metal liner may be selected. Preferably, each combustion chamber 60 is approximately 2 inches in height, thereby creating a tight radiative coupling between left wall 36 and right wall 38 of fryer tank 12 and combustion chamber 60. However, other heights, including 1 inch, 3 inches, 4 inches, 5 inches, and more are also included in the present application. The high temperature insulation 64 surrounding the combustion chamber 60 maintains the primary heat transfer zone in excess of 1000°f. Preferably, the insulation 64 comprises a high temperature aerogel insulation that minimizes heat loss to surrounding areas and maintains the outer wall of the combustion chamber 60 at the high temperatures required for the desired radiant heat transfer between the combustion chamber 60 and the left and right walls 36, 38.

Referring now specifically to fig. 5A and 5B of the drawings, an angled burner 66, a burner face 75, and a flame are depictedThe unique configuration and function of the front portion 81. In the preferred embodiment, each burner face 75 has a region of approximately 1 inch wide by 3 inches high and has a burn rate of approximately 3kW to 5kW (or 12000Btu/hr to 14000 Btu/hr) and a combustion heat release volume of greater than 50in ³ . Preferably, each nozzle 68 operates at a pressure of 3.5 inches of water such that each nozzle 68 is capable of entraining 50% -60% of the primary air. Preferably, the length of the body of each burner 66 is 6 inches to 7 inches, allowing good mixing of the fuel stream and primary air. Due to the amount of entrained primary air, a relatively compact primary flame is created with the introduction of secondary air at the periphery of the burner face 75. Preferably, the secondary inlet air plate 73 controls the amount of secondary air introduced into the flame. Preferably, the premixed gas and air is introduced into the burner 66 and ignited by the igniter 80. Thereafter, secondary air is introduced into the burner 66 through the secondary air opening 74, thereby allowing complete combustion.

The burner 66 is configured with a downward angle that allows the primary air/gas mixture to flow down the burner 66 to a substantially vertical burner face 75 and then contact the bottom wall of the combustion chamber 60 at a downward angle (see fig. 5B). This downward angle of the flame front 81 is typically due to the momentum of the gas stream. This unique selective inclination of the flame front 81 helps the combustion chamber 60 to remain as hot as possible while maintaining the highest temperature profile. The downward angle of orientation of burner 66 and the resulting downward directed flame front 81 allow for greater contact of the hot combustion gas stream with the bottom of combustion chamber 60 for a longer residence time, thereby enhancing heat transfer to cooking medium 22.

Alternatively, the burner 66 may be configured with an upward angle, thereby allowing the primary air/gas mixture to flow down the burner 66 to a substantially vertical burner face 75 and then contact the top wall of the combustion chamber 60 at an upward directional angle. This upwardly directed angular configuration of the burner 66 is shown in the embodiment of fig. 10. Such upward directional angle of the flame front 81 is typically due to the momentum of the gas stream. This selective tilting of the flame front 81 helps the combustion chamber 60 to remain as hot as possible while maintaining a maximum temperature profile. The upward angle of orientation of burner 66 and the resulting upward directed flame front 81 allow for greater contact of the hot combustion gas stream with the top of combustion chamber 60 for a longer residence time, thereby enhancing heat transfer to cooking medium 22.

Various other orientations of burner 66 may be utilized to enhance heat transfer to cooking medium 22. Thus, by disclosing the downward and upward angles of the flame front 81, applicants do not intend to limit the possibility of the flame front 81 being oriented at an angle to the burner 66.

Convection and radiation from the combustion products provide heat transfer to the left wall 36 and right wall 38 of the lower chamber 30. As used herein, a "burner tilt angle" is defined as the angle between normal vectors from the burner face 75 to the surfaces (e.g., vertically disposed side surfaces) of the left wall 36 and right wall 38 adjacent to the burner face 75. The burner tilt angle of zero degrees means that the combustion process occurs parallel to the walls 36, 38. For burner tilt angles greater than zero degrees, the flame front 81 is in intimate contact with the right wall 38 and the left wall 36.

As shown in FIG. 5A, the ignited combustion gases pass through the burner 66 toward the left wall 36 and the right wall 38 at a burner tilt angle greater than zero degrees. The burner 66 is inclined toward the walls 36, 38 according to a selected burner inclination angle such that hot gases from the turbulent combustion process are in intimate contact with the left wall 36 and the right wall 38. The flame front 81, with burner tilt angles between 5 ° and 15 °, can achieve complete combustion and can also "attach" to the left wall 36 and right wall 38, resulting in higher convective heat transfer efficiency. FIG. 5A illustrates a burner tilt angle greater than zero degrees.

Referring again to fig. 3, the combustion chamber 60 is offset upwardly from the horizontal axis by draft angle 62. The upward draft angle is greater than zero degrees from the horizontal axis and promotes efficient combustion under relatively cold start conditions of the flue 35. The draft angle 62 enables small positive draft and promotes hot gas flow by increasing the buoyancy effect. Although draft angles greater than 0 degrees and less than 15 degrees are preferred (as these angles promote small positive draft), draft angles greater than 15 degrees may be used.

The combustion chamber 60 has three separate zones or regions: a combustion zone 90, a first heat transfer zone 95, and a second heat transfer zone 98. The combustion zone 90 provides sufficient volume for primary and secondary gas combustion. The burner 66 is a partially premixed burner that uses less than 100% stoichiometric air. Thus, the primary combustion air is mixed with gaseous fuel upstream of the combustion zone 90. In the burner 66, the primary air level sets the combustion rate and thus defines the general combustion volume and shape. To drive the combustion reaction of the burner 66 to completion, additional secondary air is introduced into the combustion volume. Typically, secondary air is supplied to the combustion process in an amount in excess of 100% -150% of stoichiometric requirements.

The combustion process is accomplished by a flame front 81 having a short, compact flame from the burner 66, with a majority of the combustion process being accomplished in a combustion zone 90 within about 20% of the length of the front of the combustion chamber 60. This allows maximum contact of the hot gas with the walls 36, 38. The combustion zone is the volume associated with the combustion gases within combustion chamber 60. The size and shape of the combustion zone is determined by the fuel input rate, the amount of primary air, the amount of secondary air, and the mixing efficiency.

Only a portion of the total convective heat exchange occurs within combustion zone 90. The directional gas from the combustion zone 90 next enters the first heat transfer zone 95. The first heat transfer zone 95 is approximately 50% -60% of the length of the combustion chamber 60. One or more baffle systems 100 (see fig. 7, 8A, and 8B) direct the flow of hot gases around, through, and to the left wall 36 and right wall 36. The baffle system 100 is typically a high temperature component made of metal and is heated to red to white by a combustion gas stream that creates convection and radiant heating of the left wall 36 and right wall 38. Various baffle arrangements may be employed to achieve the flow of hot gases to the left wall 36 and the right wall 38. The baffle system 100 is located just outside the combustion zone 90, approximately in the middle of the combustion chamber 60, and is designed such that the baffle system 100 does not inhibit the combustion process. The hot gas flow directed by baffle system 100 operates at temperatures in excess of 1100F.

Fig. 8A and 8B show two such illustrative baffle designs. The baffle arrangement is closely coupled to the housing geometry, flame and/or combustion characteristics, and burner angle. To "grab" and direct the airflow in a low-loss manner, baffle system 100 preferably uses a series of flow fins or vanes 112. Vanes 112 are positioned to direct both the hot gas through baffle system 100 and the partial gas flow to left wall 36 and right wall 38. Baffle system 100 operates in the hot portion of the airflow and will approach the temperature of the airflow and act as a very efficient radiation source for fryer boxes 12. As shown in fig. 8A, baffle system 100 may be configured from a single piece of material 101, as shown in fig. 8B, or may be configured from a separate single piece of material 103.

The combustion gases flowing through the combustion chamber 60 begin to cool as they pass through the baffle system 100, and the combustion chamber wall temperature profile decreases from about 1100°f or higher to about 550°f or more prior to the outlet portion 58. The tapering of the combustion chamber 60 (see fig. 7) reduces the cross-section of the combustion chamber 60 and forces the hot outer walls of the combustion chamber 60 closer to the left and right walls 36, thereby increasing the heat transfer coupling. The exhaust gases then exit the combustion chamber 60 and enter the flue 35. Without tapering, the velocity of the combustion gases decreases over the length of the combustion chamber 60. A combustion chamber with a constant cross-sectional area will experience an undesirable reduction in local convective heat transfer with the cooling flow. The increase in local flow density with gas cooling and the resulting decrease in overall flow rate results in lower local heat transfer. The tapered combustion chamber 60 increases the local flow rate and increases the local convective heat transfer coefficient.

The burner 66 may be held in place by an indexing tab 59. As shown in fig. 8A and 8B of the drawings, in these embodiments, the taper of the combustion chamber 60 is curved. Convective heat exchange occurs in the combustion zone 90 of the combustion chamber 60, radiation and convective heat exchange occurs in the first heat transfer zone 95, and heat transfer in the form of convection occurs in the second heat transfer zone 98. As shown, the combustion zone 90 is approximately 20% of the length of the combustion chamber 60, the first heat transfer zone 95 is approximately 50% -60% of the combustion chamber 60, and the second heat transfer zone 98 is approximately 20% -30% of the length of the combustion chamber 60. Exhaust exits the combustion chamber through outlet portion 58 and enters flue 35. Flue 35 is the collection point for the hot gases exiting combustion chamber 60 and discharges the exhaust gases from deep fryer 8 to the atmosphere. While most to almost all of the heat transfer to fry vat 12 occurs within combustion chamber 60, a small amount of beneficial heat transfer occurs between lower chamber 30, rear wall 34 and flue 35.

Referring now also to fig. 6, 7, 8A and 8B, alternative configurations of the combustion chamber 60 are illustrated, including external (fig. 7, 8A, 8B) and non-external (fig. 6) tapered embodiments. The combustion chamber 60 preferably has a length 102 of about 12 inches to 14 inches, a height 104 of about 1 inch to 1.5 inches, and a width 108 (for the tapered embodiment shown in fig. 7, 8A, and 8B) of about 2 inches, where the width dimension is relative to the width of the combustion chamber at the inlet portion 56. For the externally tapered embodiment, the width 108 tapers to about 1 inch to 1.5 inches at the outlet portion 58.

Various methods of tapering or reducing the volume of the combustion chamber 60 may be used. For example, radial tapers (see fig. 8A and 8B), angular tapers (see fig. 7), or a combination thereof may be used for the conical combustion chamber 60. Although the examples described are provided for illustrative purposes, other tapering methods may be employed and are contemplated by the present application. For example, the adjustable or fixed deflector 125 may be mounted within the combustion chamber 60 or at least partially within the combustion chamber, thereby reducing the volume of the combustion chamber 60. Adjustable deflector 125 (see fig. 6) may be connected to the control system of deep fryer 8 and may be turned on or off depending on performance requirements and/or programming. Alternatively, the deflector 125 may be controlled manually. Although the combustion chamber 60 of fig. 6 (i.e., having a constant cross-sectional area) functions well, the angled, tapered combustion chamber 60 of fig. 7 (i.e., having a selectively reduced cross-sectional area) is preferably used with deep fryer 8. The usable pressure due to the tapering is not overly limited nor does it block or reduce the secondary air flow.

The natural draft combustion system of the present application provides significant advantages including, but not limited to: 1) Eliminating heat exchange tubes passing through the fryer tank; 2) Eliminating reliability and maintenance problems associated with piping in fryers; and 3) eliminates the need for expensive control systems, blowers, and other devices in existing electrically efficient open fryers.

Referring now to fig. 9 of the drawings, an alternate embodiment of a deep fryer 8' according to the application is illustrated. In this embodiment, the combustion chamber 60' is oriented generally vertically between the front wall 48' and the rear wall 50 '. Deep fryer 8 'includes a fryer housing 12' sized to hold one or more baskets 21 'and a cooking medium 22' (e.g., oil or shortening). Deep fryer 8' is a floor-standing fryer in which a fryer tank 12' is configured to hold between 35 pounds and 50 pounds of cooking medium 22' having a cooking volume of approximately 14 inches wide, 14 inches long and 6 inches deep. Preferably, the volume of the fry vat 12 'is used to hold two or more food baskets 21'.

Deep fryer 8 'is an open box deep fryer with a natural ventilation (non-powered) gas combustion system 67'. The unpowered natural draft combustion system 67' includes a gas supply conduit 72', at least one nozzle 68' in fluid communication with the gas supply conduit 72', an injection port or pump 70' in fluid communication with the nozzle 68', a substantially vertical burner 66' in fluid communication with the injection port 70', an inlet air plate 73' connected to the burner 66', a combustion chamber 60' in fluid communication with the burner 66', and an igniter 80'. The burner 66' terminates at a burner face that is disposed just inside the combustion chamber 60' or in the vicinity of the combustion chamber 60' in a manner that allows for a small separation between the burner face 75' and the combustion chamber 60'. In either configuration, the burner 66 'is in fluid communication with the combustion chamber 60'. The gas is supplied to the gas supply conduit 72 'and then flows through the nozzle 68' to the gas injection ports 70 'where the gas mixes with the air and then flows up the burner 66' to the inlet air plate 73 'and igniter 80'. The igniter 80 'combusts the premixed gas, creating a substantially vertical flame front 81'. To facilitate complete combustion, secondary air is introduced into the combustion process through secondary air openings in the inlet air plate 73'. Preferably, deep fryer 8' includes one manifold 72' on each side of lower chamber 30', each manifold 72' serving three nozzles 68', three injection ports 70', three burners 66', three air inlet plates 73', and three combustion chambers 60'.

The hot combustion gases move through the combustion chamber 60', interact with the baffle system 100', and may be affected by tapering or deflection as previously described before rising and collecting in a horizontal collection chamber 121 fluidly connected to the flue 35 '. Alternatively, the combustion chamber 60 'may be configured without a tapered and/or skewed narrow passage because the motive force required to move the hot gas through the chamber 60' and into the collection chamber 21 is due to the natural vertical flow of the hot gas (hot air rise). The collection chamber 121 is fixed to the transition walls 52', 54'. Although the combustion gas entering the collection chamber 121 is cooled, it may still provide secondary heat directly to the transition walls 52', 54'.

Referring now to fig. 10-13 of the drawings, two additional alternative embodiments of the present application are shown. Fig. 10 and 11 depict an open box natural ventilation (non-powered) gas-fired deep fryer having a lower chamber with substantially vertical sidewalls with a combustion chamber recessed into the sidewalls. Figures 12 and 13 depict an open box natural ventilation (non-powered) gas-fired deep fryer having a lower chamber with angled side walls into which the combustion chamber is recessed. The deep fryer shown in fig. 10-13 is similar in form, function, operation and efficiency to the deep fryer 8 of fig. 1-8B. Thus, although deep fryer 8 is used in the embodiments of FIGS. 10-13, not all of the components of deep fryer 8 are shown and described herein for these embodiments.

In the embodiment of fig. 10 and 11, deep fryer 308 comprises a rectangular metal housing that forms the housing of fry vat 312. The housing preferably includes a left side wall, a right side wall, a rear wall, an angled shelf 311, and a front wall. The front wall houses the control means and is preferably removable and/or hinged to allow access to control circuitry and other equipment within the housing. Deep fryer 308 is an efficient, low cost heating device for heating fluids and cooking media, such as oil or shortening. The fry vat 312 is sized to hold one or more baskets 321 and a cooking medium 322 (e.g., oil or shortening). As with deep fryer 8, deep fryer 308 may be configured as a Low Volume Fryer (LVF).

The fry vat 312 includes a lower chamber 330, a transition section 342, and a cooking section 343. Cooking zone 343 is in fluid communication with transition zone 342 and lower chamber 330. The lower chamber 330 includes opposing front and rear walls 332, 334, opposing left and right walls 336, 338, a bottom wall 339, and a large diameter drain port 340. Preferably, the front and rear walls 332, 334 and the left and right walls 336, 338 are substantially vertical, while the bottom wall 339 is curved. The bottom wall 339 forms a cold zone 345 and is configured and dimensioned to allow quick and easy hand cleaning. The cold zone 345 is located below the lower chamber 330 and is a relatively cold and stationary zone compared to the majority of the oil remaining in the fryer box 312.

The transition zone 342 includes angled walls 352, 354. The cooking zone 343 includes opposed side walls 344, 346, a front wall 348 and a rear wall 350, the side walls 344, 346 preferably being substantially vertical. The left wall 336 and right wall 338 of the lower chamber 330 are connected to the respective side walls 344, 346 of the cooking zone 343 by respective angled walls 352, 354 of the transition zone 342. The gas combustion process generates heating of the cooking medium 322 and occurs primarily at the sidewalls 336, 338 of the lower chamber 330. The heated air and other byproducts of the combustion process are in fluid contact with the outer surfaces of the sidewalls 336, 338 of the lower chamber 330.

Deep fryer 308 is an open box deep fryer with a natural ventilation (non-powered) gas combustion system 367. The non-powered natural ventilation gas combustion system 367 includes a gas supply conduit 372, at least one nozzle 368 in fluid communication with the gas supply conduit 376, an injection port 370 in fluid communication with the nozzle 368, an angled burner 366 in fluid communication with the injection port 370, an inlet air plate 373 connected to the angled burner 366, and an igniter. The burner 366 terminates at a burner face that may be disposed just inside the combustion chamber 360 or near the combustion chamber 360 in a manner that allows for a small separation between the burner face and the combustion chamber 360. In either configuration, the burner 366 is in fluid communication with the combustion chamber 360. It should be appreciated that when multiple combustion chambers 360 and multiple burners 366 are employed, the gas supply conduit 372 may act as a manifold that distributes gas between the multiple combustion chambers 360 and burners 366.

In the embodiment of fig. 10 and 11, the burners 366 are angled upward. In addition, the burners 366 may also be angled inwardly toward the outer surfaces of the left and right walls 336, 338 of the lower chamber 330. However, it should be appreciated that the burners 366 may be angled downwardly and/or inwardly as the burners 66. Gas is supplied to a gas supply conduit 372 and then flows through a nozzle 368 to a gas injection orifice 370 where the gas mixes with air and then flows up to an angled burner 366 to an inlet air plate 373 and igniter. The igniter burns the premixed gas, creating a selectively upwardly angled flame front 381 similar to the flame front 81. To aid in complete combustion, secondary air is introduced into the combustion process through secondary air openings 374 in the inlet air plate 373. Preferably, deep fryer 308 includes one header 372 on each side of lower chamber 330, each header 372 serving three nozzles 368, three injection ports 370, three burners 366, three air inlet plates 373, and three combustion chambers 360.

To further optimize heat transfer, the outer wall of each combustion chamber 360 is covered with one or more layers of high temperature insulation. The insulating material has a low heat capacity and high heat transfer resistance, but is still compact to fit the volume of space of deep fryer 308. Preferably, an insulating material 364 is used to maintain the heat distribution of each combustion chamber 360 so that each combustion chamber 360 does not return to the average wall temperature of the lower chamber 330. The relationship of the secondary heat transfer at a given temperature (e.g., q "(W/m) ² )＝εδ(T ⁴ s-T ⁴ sur), the return to the average wall temperature of the lower chamber 330 greatly reduces the radiation to the fryer box 312.

The combustion chamber 360 is secured to the left wall 336 and the right wall 338 of the lower chamber 330. Each combustion chamber 360 extends substantially horizontally from front wall 332 to rear wall 334, each combustion chamber 360 having an inlet portion 356 and an outlet portion 358. The combustion chambers 360 are sealed (except at the inlet and outlet) such that the hot gases flowing through each combustion chamber 360 are confined within such combustion chamber 360.

As used herein, the term "wetted area" refers to a surface in heat exchange relationship with the cooking medium 322. In this embodiment, the combustion chamber 360 is recessed within the sidewalls 336, 338, thereby partially surrounding the combustion chamber 360. Although in fig. 10, the combustion chamber 360 is shown as being substantially horizontal from the front wall 332 to the rear wall 334, the combustion chamber 360 may also be inclined upward from the horizontal axis at a selected draft angle greater than zero degrees (e.g., draft angle 62 in fig. 3).

As shown in fig. 11, the sidewalls 336, 338 are angled and curved about the combustion chamber 360, which allows the combustion chamber 360 to embed into the lower chamber 330, thereby increasing the wetted area at the sidewall portions 386, 387, 388, and 389. In addition, forming sidewalls 336, 338 to be partially recessed into combustion chamber 360 increases the heat transfer wetted perimeter of combustion chamber 360 and has the additional benefit of reducing the area of the outer sidewall of combustion chamber 360. As shown, the area of the combustion chamber 360 in direct contact with the side walls 336, 338 increases and the wall portions 390, 391, 392, 393, 394 and 395 in the combustion chamber 360 are in direct heat transfer relationship with the side walls 336, 338. As an additional advantage, with this configuration, less insulation is required for the reduction of the outer sidewall area of the combustion chamber 360. This embodiment improves heat transfer to the cooking medium and reduces manufacturing investment costs because less insulation is required for combustion chamber 360 at bends 386, 387, 388, and 389. As used herein, the terms "form" and "shaping" refer to any method of modifying and/or shaping the sidewalls 336, 338 to concavely embed the combustion chamber 360 in the lower chamber 330, including welded cross-sections shaped by a brake press, and any other means that allows the combustion chamber 360 to fit within the concavely embedded portions of the sidewalls 336 and 338.

The embodiment of fig. 12 and 13 is substantially similar to the embodiment of fig. 10 and 11, except that the vertical sidewalls 336, 338 of the lower chamber 330 have been replaced with angled sidewalls 436, 438 that slope from top to bottom to form a V-shaped lower chamber 430 that is wider at the top than at the bottom. This arrangement adds additional advantages because the inner surface area of the lower chamber 430 increases slightly and the volume of the lower chamber 430 increases.

To facilitate ease of cleaning of the lower chamber 430 and cold zone 345, the concave embedding channels of the combustion chamber 360 are formed with sloped surfaces and radius curves, rather than sharp folds. Thus, the bevel is easily brushed clean. Upwardly facing sloped portions 394, 395, 396 and 397 of the side walls 436, 438 are abrupt to facilitate easy passage of food particles through the cold zone 345 without settling on the inner surfaces of the side walls 436, 438. The sidewalls 436, 438 of the lower chamber 430 are sloped or inclined from the vertical to increase the opening to the lower chamber 430, allowing better access for brushing or hand wiping around the recessed area. The angled side walls 436, 438 are easily manufactured using typical sheet metal forming tools (e.g., computer controlled pressure brakes).

It should be appreciated that the sloped side walls of the lower chamber 430 may also be used in alternative embodiments in which the combustion chamber is not recessed within the angled side walls 436, 438. In such an alternative embodiment, the sidewalls 436, 438 would be sloped but straight. Thus, as shown in the embodiment of FIG. 2, the combustion chamber 360 will be in heat transfer communication with the outer surfaces of the sidewalls 436, 438. Thus, in the transverse direction, the lower chamber 430 is wider at the upper end of the lower chamber 430 where it connects with the transition zone 342 than at the lower end of the lower chamber 4.3 where it connects with the cold zone 345.

Although combustion chambers 60 and 360 have been described and shown herein as being secured to side walls 36, 38, 336, 338, 436, and 438, respectively, it should be understood that additional combustion chambers 60, 360 may also be secured to the outer surfaces of transition walls 52, 54, 352, and 354 of transition sections 42 and 342, extending from front walls 48 and 348 to rear walls 50 and 350, respectively.

Referring now to fig. 14-15 of the drawings, another alternative embodiment of the present application is shown. As used herein, the term "power" refers to a deep fryer combustion system in which the motive force causing combustion and exhaust gas flow is achieved by an unnatural pressure differential between the hot gases and the surrounding atmospheric conditions.

Various configurations of deep fryer 308 may utilize power and applicant does not intend to be limited by the examples herein. For example, applicant has proposed substantially parallel side walls 36, 38, 336, 338 and perpendicular side walls 436, 438. In addition, deep fryer 308 may have any number of combustion chambers 360 on each side of lower tank 30, 430. Various configurations have been described that combine slot geometry (substantially parallel slot side walls and substantially parallel side walls) with the number of combustion chambers per side (whether one or more per side). Other configurations are possible and, as such, applicant does not intend to limit the scope of applicant's invention by the examples listed.

The power may force the combustion gases and exhaust gases through the system, or may pull the combustion gases and exhaust gases through the combustion and exhaust system, and may include one or more fans, blower motors, vacuum systems, induced fans, and any other components required to apply power to the combustion and exhaust gases.

As shown in fig. 13, a blower motor 501 is used to apply power to the combustion gases and flue gases 79. The motive force (suction applied to the outlet end of flue 35) allows burner 366 and combustion chamber 360 to operate at slightly sub-atmospheric or sub-atmospheric pressures. Thus, an inexpensive, generally horizontally oriented and partially premixed burner 366 may be used, or a conventional burner, such as in a jet burner. Such a burner is simple and inexpensive.

Furthermore, the motive force applied to the combustion gases and exhaust gases allows the combustion chamber 360 to be simplified and made cheaper. Fully premixed burners (e.g., infrared), baffles, deflectors, and separate secondary fin convective heat transfer elements may be eliminated by introducing motive force into a substantially horizontal combustion chamber secured outside of the slot walls 436, 438.

The jet burner produces a short, compact flame and the combustion of the gas within the chamber 360 is completed within about the first 20% of the length of the chamber 360. This efficient combustion of the gases allows for maximum contact of the hot combustion gases with the slot side walls 436, 438 and the introduction of secondary air near the inlet periphery of the combustion chamber 360 creates a highly turbulent combustion flow with high heat transfer capability.

The introduction of motive force can reduce the flow area (cross section) of the combustion chamber, increase the local flow velocity and increase the local convective heat transfer coefficient hc (Btu/hr-ft) ² -F). Given the pressure/suction availability of the blower 501, the combustion chamber 360 may be substantially narrowed in depth to promote convective heat transfer by accelerating the hot gas flow as the gas cools.

The motive force described herein may push or pull the hot combustion gases and exhaust gases through the restrictive flow circuit, substantially enhancing convective and radiant heat transfer to the slot side walls 436, 438.

It is apparent that there has been described and illustrated an application with significant advantages. While the application has been illustrated in a limited number of forms, it is not limited to those forms, but is amenable to various changes and modifications without departing from the spirit thereof.

Claims (19)

1. A deep fryer comprising:

a fryer housing for holding a cooking medium, the fryer housing comprising:

a cooking zone; and

a lower chamber below the cooking zone, the lower chamber comprising:

a front wall and a rear wall; and

a right side wall and a left side wall; and

a combustion system, the combustion system comprising:

at least one gas supply conduit for receiving and distributing combustion gases;

at least one partially premixed burner in fluid communication with the at least one gas supply conduit;

at least one substantially horizontal combustion chamber in fluid communication with the at least one burner, the combustion chamber coupled to an outer surface of the right side wall or the left side wall of the lower chamber for heat transfer communication with the outer surface of the right side wall or the left side wall; and

at least one blower system for applying power to the combustion gases;

wherein the combustion gas is directed to the right side wall and the left side wall of the lower chamber.

2. The deep fryer of claim 1, wherein said blower system comprises at least one of:

a blower motor;

a fan; and

and (5) a draught fan.

3. The deep fryer of claim 2, wherein said blower system is coupled to a chimney of said fryer tank.

4. The deep fryer of claim 2, wherein said blower system allows said at least one burner to operate at a sub-atmospheric pressure.

5. The deep fryer of claim 2, wherein said blower system allows said at least one combustion chamber to operate at a sub-atmospheric pressure.

6. The deep fryer of claim 1, wherein said at least one combustion chamber is embedded in said left side wall or said right side wall.

7. The deep fryer of claim 1, wherein said lower chamber is wider at an upper end than at a lower end in a lateral direction.

8. The deep fryer of claim 1, wherein said at least one burner is a jet burner.

9. The deep fryer of claim 1, wherein said burner extends from said gas supply conduit at a selected vertical angle in a generally downward direction and then is inclined in a generally horizontal direction prior to entering said combustion chamber.

10. The deep fryer of claim 1, wherein said burner extends from said gas supply conduit at a selected vertical angle in a generally upward direction and then is inclined in a generally horizontal direction prior to entering said combustion chamber.

11. The deep fryer of claim 1, wherein said burner is sloped inwardly toward an outer surface of said lower chamber.

12. The deep fryer of claim 1, wherein at least one burner is a plurality of burners located on each side of said lower chamber; and

wherein the at least one substantially horizontal combustion chamber is a plurality of substantially horizontal combustion chambers located on each side of the lower chamber.

13. The deep fryer of claim 1, wherein said combustion chamber has an upward draft angle relative to a horizontal plane from an inlet portion to an outlet portion.

14. The deep fryer of claim 1, wherein the combustion chamber tapers inwardly from an inlet portion to an outlet portion.

15. A deep fryer comprising:

a fryer housing for holding a cooking medium, the fryer housing comprising:

A cooking zone; and

a lower chamber below the cooking zone, the lower chamber comprising:

a front wall and a rear wall; and

a right side wall and a left side wall; and

a combustion system for distributing combustion gases, the combustion system comprising:

a plurality of right side combustion chambers connected to an outer surface of a right side wall of the lower chamber for heat transfer communication with the outer surface of the right side wall; and

a plurality of left side combustion chambers connected to an outer surface of a left side wall of the lower chamber for heat transfer communication with the outer surface of the left side wall; and

means for moving the combustion gases through the combustion chamber;

wherein the combustion gases are partially premixed with air prior to entering each combustion chamber and mixed with secondary air within each combustion chamber.

16. The deep fryer of claim 15, wherein the means for moving combustion gases through the combustion chamber comprises at least one of:

a blower motor;

a fan; and

and (5) a draught fan.

17. The deep fryer of claim 15, wherein said right side combustion chamber is embedded in a right side wall of said lower chamber and said left side combustion chamber is embedded in a left side wall of said lower chamber.

18. The deep fryer of claim 15, wherein said right side wall and said left side wall are substantially parallel in a substantially vertical direction.

19. The deep fryer of claim 15, wherein said right side wall and said left side wall are angled with respect to each other in a V-shaped orientation.