FIELD OF THE INVENTION

The present invention relates to an improved design for biscuit baking ovens. More
particularly, the present invention relates to an oven design, which employs different
combination of heating medium like thermic fluid / infra-red heaters / infra-red rays / radio frequency rays to transfer the heat to bake biscuits.

BACKGROUND AND PRIOR ART

Conventionally baking industry uses the following types of ovens: Indirect fired oven, Direct Fired oven, Hybrid ovens and Electric ovens. In indirect fired ovens, the heat source is independent of the baking chamber atmosphere and heat transfer takes place through heat
exchanger. In direct fired ovens, heat transfer takes place directly through flames to the
baking chamber. The hybrid ovens are the combination of both direct and indirect fired ovens and the electric coil heaters are used inside the baking chamber as a heat source.
The major drawback of the existing technology is that the heat transfer takes place from air to air for which the thermal conductivity is quite low and hence the net heat utilized by the
system is less. In due course of time the efficiency of the oven drastically reduces because of the radiator tubes getting coated/choked with carbon particles especially during burning of unclean fuel. This result in non-uniform distribution of heat inside the baking chamber between operating and non-operating sides is unequal inside the baking chamber and also due to large variation in temperature and heat transfer. Also because of design constraints, the gap between the heat emitting surface (radiator tubes) and heat absorbing body surface (unbaked biscuits) is of the order of 5 inches, which further reduces the amount of heat transfer as it depends on the distance between the two bodies. Apart from these factors, the response time of the oven is also quite high.
US 6146677 A teaches an instant high efficiency carousel pizza oven which is an oven of the
open cavity or open input type which permits food access and fluid communication with the
atmosphere through a proximal or front opening within the oven housing. The present oven is
preferably defined in terms of a method which employs a solid rotating thermal reservoir in
the nature of a circular ceramic panel capable or storing large amounts of thermal energy.

Rotation of the panel assures that hot spots will not develop thereby eliminating scorching of food items cooked therein. Provided beneath said panel, in thermal communication therewith,
and preferably along a radius thereof situated substantially normal to an axis of rotation of
said ceramic panel, is a flame burner which furnishes greater heat to the panel as a function of increase in distance from said axis to thereby provide substantially uniform heating to the rotating panel as a function of increase in circumference relative to distance from the axis.
Thereby, thermal values are very efficiently transferred from the gas burner flames to the
panel which, through conduction, provides heating to the pizza through the bottom surface
thereof. In a further step, there is provided an infrared radiant heat source positioned within the oven but over said rotating panel to thereby provide radiant heat into the region above the plane of rotation of said panel, this while directly striking the toppings of that pizza, this within a narrow area of said plane which is characteristic of the line of site function of heating by radiation. The relative intensities of the above forms of heat transfer are balanced through the use of a thermostat, preferably located beneath the rotating panel. In such balancing, it is recognized that the heating by conduction which occurs beneath the rotating panel entails the use of a lower temperature, however with greater heat or energy content,while the infrared heat source positioned over panel, i.e., the rotating thermal reservoir,
entails use of a higher temperature, however in a much lower amount of total heat or energy
in that the primary function of the latter is to provide cooking to the pizza toppings which is a more delicate cooking function than is that of baking of crust of the pizza from beneath.
Though electric ovens can reduce most of the drawbacks they are not the economically
favored as the power consumption for these ovens is quite high and the supply of power is
also not consistent.
Thus there is a need to provide a biscuit baking oven, which overcomes the drawbacks of the prior technology which necessitated inventing this design with various combinations of heat sources.
The present inventors have found that capturing the losses and regularly doing thermal audit
for the ovens can improve the efficiency of the ovens currently in use.

The idea conceived by the present inventors is wholly different from the construction
described in US6146677A as it does not involve a rotary type oven but an oven where the
product moves from one end to another passing through varied temperature zones and
conditions in a manner entirely different from US6146677A. No part of the teachings of
US6146677A is relevant to the present invention.

OBJECTS OF THE INVENTION

Accordingly, it is an object of the present invention to overcome the drawbacks of the prior
art.
It is another object of the present invention to provide a design for biscuit baking oven.
It is yet another object of the present invention to provide a design for biscuit baking oven which works on the principle of heat transfer through various sources like fluid media, infra red rays, radio frequency rays etc.
It is yet another object of the present invention to provide a design for biscuit baking oven which environment friendly.
It is yet another object of the present invention to provide the product at a equal distributed moisture level across the biscuit in turn helps improving the quality and the shelf life of the product.

SUMMARY OF THE INVENTION

An improved biscuit baking oven for improved heat transfer rate comprising a infra red
heaters and a radio frequency heater kept close to the product surface and a thermic fluid
heater, thermic heater burner, thermic pump, wherein the distance between the heat emitting
surface of all above different combinations and heat absorbing surface is reduced.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Figure 1 illustrates piping and instrumentation diagram of the oven design including Thermic
Fluid Heater, New apparatus and related accessories
Figure 2 illustrates the graphical representation of the working of the system and the flow
circuit inside the developed system.

Figure 3 illustrates the cross sectional view of the oven design for various heating medium
Figure 4 illustrates the general arrangement of different combinations of heaters and
positions.
DETAILED DESCRIPTION OF THE ACCOMPANYING FIGURE
Figure 1 shows the Piping and Instrumentation Diagram of the system which plays a crucial
role in the desired operation of the invention. The thermic fluid is heated in the thermic fluid
heater (3) and is circulated in the circuit by means of thermic fluid pumps (5). The thermic
fluid enters the system through inflow headers and comes out from outflow headers. The
return line from the system goes to the de-aerator tank (4) which takes care of the thermal
expansion and contraction of thermic fluid. From de-aerator tank (4) the fluid goes to the
suction of the thermic fluid pump (5) and then to thermic fluid heater (3). An additional dump
tank (6) is provided to store the thermic fluid whenever the thermic fluid from the pipeline
needs to be drained out for maintenance purpose. The flue gases from the thermic fluid heater
can be letout through chimney (1) which is open to atmosphere after being utilized in the
waste heat recovery system (2).
Figure 2 demonstrates the general arrangement of the thermic fluid system, which comes in
between inflow and outflow headers as shown in figure 1. For illustration purpose a system
comprises 4 identical zones has been considered with top and bottom modules i.e., 4 zones
with 16 modules (Z-1TM1, TM2; Z-1BM1,BM2; Z-2TM1,TM2; Z-2BM1,BM2; Z3TM1,TM2; Z-3BM1,BM2; Z-4TM1,TM2; Z-4BM1,BM2), which form the baking chamber
of the system. Thermic fluid from the thermic fluid heater (Fig. 1 [3]) enters the system
through inlet header. From the inlet header, thermic fluid enters the respective zones through 8 different branches (T1, T2, T3, T4 for top modules and B1, B2, B3, B4 for bottom
modules). Each module consists of a set of radiant banks inside which the thermic fluid
flows. The arrangement of the tubes inside the radiant banks is such that the direction of flow of thermic fluid in any adjacent tube is in opposite direction. Further, each tube has extended fin, which maximizes the heat transfer area and hence the heat to the corresponding zone.
Also, since the thermal conductivity and heat carrying capacity of the thermic fluid is higher,
the heat source can be placed close to the product. The flow of thermic fluid through bypass
lines can be controlled through control valves provided. Once the circulation through the

module is complete or bypassed as the case may be, the thermic fluid enters the return header
and leaves the system through outflow.
Figure 3 shows the cross-sectional view of the system. The radiant banks (fig. 2 [15], [16],
[17], [18]) form the top and bottom covering (9) for the band (10). The heat is trapped inside
the baking chamber by means of additional reflector plates (4, 5). For the purpose of
cleaning, the bottom reflector plate (4) is inclined. Air, which is known to be the best
insulators, is used as insulation (1, 2) in the area beyond the reflector plates (5, 4). This
enclosure is further insulated using Rockwool Ceramic Insulation (7). The inlet headers (8)
bring the thermic fluid to radiator tubes (9) and once circulated, the fluid exits the chamber
through outlet header (11). To arrest the heat loss from the fluid exiting the system, an extra
insulation is provided. Beyond the first layer of insulation (7), air is again used as an insulator
(6). The outer insulation panels (15) form the final enclosure for the system. A hinge (13) is
provided so that the top cover of the system can be opened. In order to monitor temperature, a
slot for thermo-well (12) is provided. The system is supported on the supporting channel (16),
which are wheel mounted (17).
Figure 4 illustrates the complete system of heating with the combination of different heating
medium like thermic fluid (2), radio frequency rays (3) and infra red rays (1) with their
respective positions with respect to other heating source being fixed depending upon the type
of the biscuit being produced. The above combination of all these heating medium in any
sequences with respect to each other depending upon heat source required by the particular
biscuit is used to heat the biscuits in baking oven (4). Thus the new invention we call it a
biscuit baking oven (4), which over comes the draw backs of prior technology / method
which necessitated inventing this design with various heat sources.
DETAILED DESCRIPTION OF THE INVENTION
As per laws of thermodynamics, whenever a hot media or body comes in the vicinity of cold
media or body heat transfer takes place until both the bodies attain at same temperature
(Thermal Equilibrium). Also the amount of heat transfer is inversely proportional to the
distance between the two bodies.

The operation of the new oven is based on the principle of heat transfer through different
media like infra red rays, fluid media, radio frequency rays. The infra red heaters and radio
frequency heaters are fitted in appropriate place for heating the product and the thermic fluid
is heated in the thermic fluid heater and then it is circulated through the pipes inside the oven.
Since the thermal conductivity of the fluid are higher than that of the air, and heat transfer
rate of infra red rays and radio frequency are higher and thereby enabling the efficient heat
transfer. Each zone inside an oven has a set of radiator tubes fitted across the width in which
thermic fluid will be circulated in the opposite direction so as to get consistent temperature
across the band. The hot circulating thermic fluid transfers heat to radiator tubes through
conduction, which in turn transfer the heat to unbaked biscuits through radiation and
convection.
Also, in the new oven, the gap between the heat emitting surface (radiator tubes, heater
filaments) and heat absorbing body surface (unbaked biscuit) has been reduced thereby
enabling efficient heat transfer. Apart from that, since the fluid is re-circulated within the
system the stack losses are reduced which further helps to increase the efficiency.
The combined effects of these factors provide improved efficiency of the new oven.
According to the present invention, the said oven has the following advantages:
 Better heat transfer rate as thermal conductivity for liquid (Thermonol-55) used is
higher than that of air which will improve efficiency drastically.
 Better and quick heat transfer through infra red rays
 Better and uniform heat transfer which keeps the moisture level uniform through out
the product.
 Better temperature profile control and consistent performance as the response time of
the oven is less and temperature can be controlled by controlling the flow rate of the
fluid.
 Achieving drastic reduction in fuel and power consumption since the efficiency is
high as compared to conventional oven.
 Delivering trouble free sustained operation is possible as there will be no carbon
deposition inside the radiator tubes.

 Helping in offsetting the impact of fuel cost increase on the business because fuel
consumption will be less.
 Helping in reducing the adverse effect on environment as GHG emissions will be less.
The design of the oven is unique as it minimizes the gap between the heat source and the
product. Further, additional fins in the radiator tubes are provided in order to maximize
the heat transfer area, thus enabling the oven to be operated at lower temperature.
Moreover, the temperature difference between operating and non-operating position is
zero.
Accordingly, the present invention provides an improved design for baking oven with
enhanced efficiency as compared with the existing designs. The efficiency of the oven
design of the present invention is in the range of 70-75% whereas for existing ovens, it is
merely 35-40%. Moreover, the reduction in energy consumption is also remarkably
improved as it is found that the reduction in energy consumption per kg of production is
of the order of 34% approximately.

WE CLAIM:
1. A baking system with improved heat transfer comprising:
plurality of baking chambers having multiple zones;
a thermic fluid system comprising arrangement of conduits for conveying fluid
medium around such baking chambers such that said fluid medium is circulated in the
said system by means of a thermic fluid pumping means which in turn is operatively
connected to with a de-aerator means; and
heating means which is adapted to supply heat of pre-determined temperatures
to the multiple zones, the products to be baked enters from one end and exits the
system from another end.
2. The baking system as claimed in claim 1 wherein the said baking chamber comprises at
least four zones.
3. The baking system as claimed in claim 2 wherein the said zones comprises at least four
modules.
4. The baking system as claimed in claim 1 wherein the gaseous waste is discarded by an
outlet means or utilized in a waste heat recovery system.
5. The baking system as claimed in claim 1 wherein the distance between the said heat
emitting surface and the said heat absorbing surface is 2 to 3 inches.
6. The baking system as claimed in claim 1 wherein the heating means comprises of thermic
fluid, infra-red rays, and radio frequency rays in combination.