Title of Invention

"AN INDUCTION HEATING DEVICE FOR HEATING FLUID IN A NON-METALIC VESSEL OR PIPELINE"

Abstract This invention relates to an induction heating device for heating fluids in non-metallic vessels or pipelines, comprising : an electromagnetic induction heating assembly (5) arranged internally in said non-metallic vessel or pipeline (8); an induction heating working coil (7) of a high frequency pulse width modulation (PWM) inverter circuit (4) being provided around said non-metallic vessels or pipelines (8) for generating eddy current heating in said induction heating assembly wherein the said induction heating working coil (7) acts as a primary coil and heating assembly (5) is provided as a secondary coil.
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The present invention relates to an induction heating device for heating fluids in a non-metal lie vessel or pipeline.
In the case of metallic pipeline or vessel, the pipeline or
vessel can be directly heated, by induction. The induction heating
is a contactiess method of generating the heat in a magnetically-
conductive workpiece from an external high frequency
alternating magnetic field produced by a high frequency pulse
width modulated inverter using semiconductor switching devices.
The high-frequency magnetic field is usually established by a magnetic coil wrapped around the workpiece or held parallel to the workpiece surface. Resonant inverters are widely used for induction-heating over wide frequency ranges from 4KHz to 500KHz. The inverter operating frequency selected far a particular application is based on heat effectiveness and power conversion efficiency. The constant high-frequency resonant inverter circuits using insulated gate bipolar transistor (IGBT) appears more efficient, compact in size and of faster response as compared to the frequency changing bi-junctional transistor (BJT) inverter and conventional electrical heating method.
The electromaqnetic induction based fluid heating appliance using the high-frequency resonant invertter and its related system

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contral technologies can be used in the fields of medical,chemical, mechanical and consumer heat energy processing utilization in the particular system. Direct fluid heating based on electromagnetic induction principle can be done by pipeline surface and wail skin effect heating.
However, in the case of metallic pipeline or vessel,the heat loss from the pipeline or vessel may be considerable. This heat loss lowers the efficiency of the system. Also the heating of fluid in such a system may not be uniform.
Against this a non-metallic pipeline will act as a thermoseal. But a non-metal lie pipeline or vessel is not magnetically conductive and hence cannot be directly heated by induction.
Thus, the main object of the present invention is to provide a high efficiency induction heating device for heating fluids in a non-metallie vessel or pipeline, thereby minimizing heat loss from the vessel or pipeline.
This can be achieved by using a metallie package internally in the vessel or pipeline. Eddy currents are generated in the internal metallic package, thereby heating the fluid in the vessel or pipeline.

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By introducing a metallic package in the vessel or pipeline, eddy currents are induced in the package by means of an external working coil connected either to high—frequency resonant inverter operated by a phase shifted pulse width modulation .PWM scheme or to a frequency changing series bi-junctional transistor BJT inverter.
The metallic package can be made from a plurality of stainless steel sheets arranged in parallel to one another on an insulated
shaft.
The sheets can be made in corrugated form to provide extra surface area for maximum heat transfer to the fluid.
The axis of corrugation can be slanted either to the left from the vertical or to the right from the vertical. Alternate plates (like the first, third, etc) can have their axes with a left slant and the others (second, fourth, etc) with a right slant.
This will result in greater friction as the fluid in the vessel or pipeline moves on from one plate to the other, thereby generating additional heat.

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The corrugations can also be provided with holes, which will generate further turbulece in the fluid, thereby gene ratines additional heat.
The working coi1 or induction coi1 can be wraped around the non-metallic vessel or pipeline in a helical shape. In order to prevent skin effect, bundle conductors are used for the coil.
The present invention thus provides an induction heating device for heating fluids in nan-metallic vessels or pipelines, comprising an electromagnetic induction heating assembly is arranged internally in said non-metallic vessel or pipeline and an induction heating working coil of a high frequency pulse width Invert No.? modulation inverter circuit being provided around said non- metallic vessel or pipeline for generating eddy current heating in said induction heating assembly. For better results, the improved inverter circuit arrangement of co-pending Indian Patent ct Application No 69/CAL/200l filed on Q5/Q2/2001 can be used.
The invention will now be described in detail with the help of the accompanying drawings, where
Fig. 1 shows in schematic form an induction device for heating
fluids in a non—metallic vessel or pipeline; Fig. 2 shows a voltage fed full-bridge type series resonant
inverter;

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Fig. 3 shows the voltage and current waveforms;
Fig.4 shows a phase shifted PWM high frequency inverter;
Fig- 5 shows a metal heating package in the vessel or pipeline;
Fig.6 shows the internal structure of the metallic heating
package of the present invention; Fig = 7 shows the observed output voltage and current waveforms
and the simulated waveform; Fig.8 shows input voltage and current waveform; Fig.9 shows output current waveforms; Fig.10 shows the comparative applications of induction heating
system and existing heating applications.
Fig. 1 shows in schematic form the system configuration of an electromagnetic induction heating appliance of the present invnetion for heating fluid using a radio frequency (RF) power source i of 4ZKHz to 5-00 KHz series resonant pulse width modulation (PWM), invereter 4 with a non-smooth power filter 3 „
An AC/DC diode module" 2 is connected to the power source 1, the DC output of which is econnected to the non-smooth filter 3.
The inverter 4 can be a full-bridge type series resonant insulated gate bipolar transistor (IGBT) inverter with a phase shifted pulse width modulation conbrol.

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The output voltage of the inverter shown in Fig. 2 can be continuously regulated by phase-shifted PWM scheme at constant
frequency. The operating voltage and current waveforms of this
phase shifted PWM inverter are illustrated in Fig.3.
It is seen from Fig. 3 that the turn-on switching currents of S1/S2 in the bridge left leg are positive in PWM regulation mode. As a result, S1/S2 operate at hard-switching but S1/S2 can realize turn-off under a condition of zero current and zero voltage soft-switching in spite of phase shifted PWM conditions.
On the other hand, B3/S4 in the bridge right leg can ideally turn-on under a condition of zero current and zero voltage soft switching in spite of a phase-shifted PWM condition but turn off at a hard switching condition. The operating waveforms as obtained from computer simulation are shown in Fig- 3. Fig. 4 indicates a newly-proposed topology of a soft-switched PWM type series load-resonant inverter using lossless inductor snubber bridge leg and lossless capacitor snubber bridge leg independently of a phase-shifted PWM regulation mode. The lumped Rl-Ll series circuit is an equivalent circuit of the induction heated loaded transformer model 1ing.

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In case the resistance component of the lumped temperature-dependent series load circuit is relatively large, the series compensated capacitor shown in Fig. 4 is introduced for optimising from the view point of power converison. In this case, the resistance component of the lumped series load circuit is relatively small, matching transformer is not required and the parallel capacitor compensated load structure in series with a small auxiliary compensated inductor is more suitable as compared to series ioad-resonant operation.
A specifically designed electromagnetic induction heating assembly 5 is placed internally in the non-metallic vessel or a pipeline as shown in Fig.1 and in greater details in Figs- 5 and 6.
This assembly can be in the form of a metallic package 5 made
from a plurality of stainless steel plates 6 arranged in parallel
to one another and mounted on an insulated shaft, not shown in
Fig.6.
A working coil 7 is wrapped around the non-metallic vessel or pipeline 8 in a helical shape far generating high frequency flux. The metallic package 5 will thus achieve eddy current heating in the system.

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The sheets 6 are made in corrugated form. Such an arrangement will provide extra surface area for higher and faster heat transfer to the fluid. The axis of corrugation can be slanted either to the left or to the right from the vertical. Alternate plates, like the first, third, etc. can have slant to the left and the other plates, second, fourth, etc. can have a slant to the right. This arrangement will geerate additional heat in the system due to greater frictions as the fluid flows through the metallic package 5.
These corrugations can further be provided with holes for generating additional turbulence in the fluid resulting in additional heat and faster heat transfer.
The eddy current heated metallic package 5 of the present invention is tightly incorporated in the non—metallic vessel or" pipeline B.
The mechanically processed package with thin stainless steel plates 6 having many holes on the corrugations are illustraed in Figs.5 and 6. When the fluid flows through the internal metallic package 5 in the vessel or pipeline S with a working coil 7 wrapped around it, the turbulent fluid is heated by the eddy current generated inside the metallic package 5.

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For the purpose of heating, the coil does not get hot directly.
Thus, high power density, large heating surface and
high temperature heating are achieved by introducing high
frequency induction heating principle.
The distribution of power density to the pipeline or vessel can be easily changed with the coil configuration including local heating.
The response of load temperature is quite high because of the high frequency inverter regulation strategy- Implementation of microprocessor-based control can be easily introduced. Phase-shifted PWM regulation under a precise temperature se feting condition by an auto-tuning PID-based feed back implementation scheme would permit stable operation and easy control.
In the proposed scheme heat is being directly generated in the vessel as load and there is practically no consumption of energy due to conduction. This permits sufficient reduction of the running cost and the energy saving.
Eddy currents in the flow-throuoh macmetically-conductive metallic package incorporated into the vessel or tank is induced

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through a contactless high-frequency power transmission in the heating package- So, unlike electric heater, there is no scope for any shock hazard.
Design specification of inverter-fed fluid heating app1iance are
as follows :
I tern Design Specification
Input Voltage Single-phase 200V RMS
Regulated Output Power 0 to 10 KW
Power Regulation strategy Constant-frequency Phase-shifted
PWM
Operating Frequency 30 KHz
Temperature Control System Autotuning PID Control
Above table indicates the practical design specifications of electromagnetic induction fluid-heating appliance using a series load-resonant inverter with self-tuning PID based feedback control scheme. The output power can be continuously regulated according to the phase-shzfted angle between 0 to 180 degree.
Fig. 7 shows the observed operating voltage and current waveforms in the series load-resonant inverter with a phase-shifted PWM

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scheme as compared with a computer-aided simulating wavefarms. The observed input voltage and current waveforms of this appliance are displayed in Fig. 8. The output high-frequency current waveform displayed in Fig.9. Fig. 10 shows the feasible application of inverter-fed electromagnetic induction heated boiler with a precise, intelligent and stable feedback control.
Present invention provides an electromagnetic induction based fluid heating appliance which is fed from a series load-resonant PWM high-frequency inverter using I G B T. modules. The working principle of the proposed PWM control inverter topology has been described for modern induction heating. The proposed appliance is expected to be most-cost effective for induction-heated boiler heat exchanger and evaporator because of compactness in size, high efficiency conversion, quick response and precise temperature control than the other method containing mare harmonics in high frequency a.c. generation and more noise and also mare loss in conventional electric heating.
The induction heating device for heating fluid in a non-metallic vessel or pipeline described above is highly acceptable for fluid

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heat transfer and delivery processing plants as well as heat energy storage and heat exchange processing because of clean, compact, efficient and smart response. From practical view point the above appliance is cost effective for induction heated boiler, evaporator, hot water supplier and super heating unit in the pipeline system.
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WE CLAIM:
1. An induction heating device for heating fluids in non-metallic vessels or pipelines, comprising :
an electromagnetic induction heating assembly (5) arranged internally in said non-metallic vessel or pipeline (8);
an induction heating working coil (7) of a high frequency pulse width modulation (PWM) inverter circuit (4) being provided around said non-metallic vessels or pipelines (8) for generating eddy current heating in said induction heating assembly wherein the said induction heating working coil (7) acts as a primary coil and heating assembly (5) is provided as a secondary coil.
2, An induction heating advice as claimed in claim 1, wherein said
electromagnetic induction heating assembly (5) is a metallic package
comprising stainless steel plates (6).
3. An induction heating device as claimed in claim 1, wherein said
stainless steel plates (6) are arranged in parallel to one another and
mounted on an insulated shaft,
4, An induction heating device as claimed in claim 1, wherein said
stainless steel plates (5) are made in corrugated form and the axis of
corrugation are given a slant either to the left or to the right from the
vertical axis,
5. An induction heating device as claimed in claim 1, wherein the
alternating stainless steel plates (6) are given a slant to the left and a
slant to the right of the vertical axis.

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6. An induction heating device as claimed in claim 1, wherein the corrugation in the stainless steel plates are provided with holes for generating additional turbulence in the fluid.
7. An induction heating device as claimed in claim 1, wherein the inverter circuit is a series resonant inverter with IGBT or BJT.
8. An induction heating, device as claimed in claim 1, wherein said induction heating working coil 9. An induction heating device as claimed in claim 1, wherein
said inverter working heating coil is made from bundle conductors for preventing skin effect.
10. An induction heating device for heating fluid in a non-
metallic vessel or pipelines substantially as herein described and
illustrated in the accompanying drawings.
Dated this 1st day of February
AN INDUCTION HEATING DEVICE FOR HEATING FLUID IN NON-METALLIC VESSELS OR PIPE LINE
This invention relates to an induction heating device for heating fluids in non-metallic vessels or pipelines, comprising :
an electromagnetic induction heating assembly (5) arranged internally in said non-metallic vessel or pipeline (8);
an induction heating working coil (7) of a high frequency pulse width modulation (PWM) inverter circuit (4) being provided around said non-metallic vessels or pipelines (8) for generating eddy current heating in said induction heating assembly wherein the said induction heating working coil (7) acts as a primary coil and heating assembly (5) is provided as a secondary coil.

Documents:

0071-cal-2001 abstract.pdf

0071-cal-2001 assingnment.pdf

0071-cal-2001 claims.pdf

0071-cal-2001 correspondence.pdf

0071-cal-2001 description(complete).pdf

0071-cal-2001 drawings.pdf

0071-cal-2001 form-1.pdf

0071-cal-2001 form-18.pdf

0071-cal-2001 form-2.pdf

0071-cal-2001 form-26.pdf

0071-cal-2001 form-3.pdf

0071-cal-2001 form-5.pdf

0071-cal-2001 letters patent.pdf

0071-cal-2001 p.a.pdf

0071-cal-2001 reply f.e.r.pdf


Patent Number 205322
Indian Patent Application Number 71/CAL/2001
PG Journal Number 13/2007
Publication Date 30-Mar-2007
Grant Date 30-Mar-2007
Date of Filing 06-Feb-2001
Name of Patentee BIRLA INSTITUTE OF TECHNOLOGY MESRA
Applicant Address RANCHI,PIN 835215
Inventors:
# Inventor's Name Inventor's Address
1 SADHU PRADIP KUMAR RANCHI,PIN 835215
2 CHKRABORTY R N RANCHI,PIN 835215
3 CHOUDHURY S P RANCHI,PIN 835215
PCT International Classification Number H 05 B 6/10
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA