THE PATENT ACT, 1970
COMPLETE SPECIFICATION
(SECTION-10)
TITLE
EXTENDED STEAM GENERATOR'
APPLICANT
THERMAX LIMITED,
D-13, MIDC INDUSTRIAL AREA, CHINCHWAD, PUNE-411 019, MAHARASHTRA, INDIA, AN INDIAN COMPANY
The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed.

Extended Steam Generator. INTRODUCTION TO THE FIELD OF THE INVENT ION.
The invention relates to improved extended steam generator.
This invention more particularly relates to extended steam generator fired by fuels, which can be solid, or oil or a gas.
This invention still more particularly relates to a steam generator fired by oil or gas or fuel.
PRIOR ART AND DRAW BACKS.
It is already known in the prior art to generate steam from liquid /gaseous fuels.
In these conventional steam Generators, it is known to generate steam by exchange of heat from hot Flue Gases to the Water/Steam.
It is also known that all the steam generators with water hold-up less than 22.75 litres are of coil type (tubes wound in helical coil from) water tube boilers. In order to provide adequate heat transfer area for different steam generator sizes, several configuration of coils are being used.
In all designs, with the water hold-up not exceeding 22.75 litres, there is a limitation in providing higher and higher gas side heat transfer area to increase the steam generator capacity. As such the maximum capacity of the steam generator is limited to 850 Kg/h of steam generation from and at 100°C
The main limitation of the prior art is that higher capacity steam generators cannot be made beyond 850 Kg/hr F&A 100° C capacity by providing higher and higher extended surfaces, but yet maintain the water hold up bellow 22.75 litres.
The peak metal temperature of the extended surface increases with the increase in the width/length of the extended surface.
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OBJECTS OF THE INVENTION
It is the principal object of this invention to propose a new design or improved in the exciting steam
generators.
It is another object of this invention to propose the use of an extended surface made of a metal or a
combination of metals with high thermal conductivity of the extended surface in order to maintain the
peak metal temperature below the safe operating temperature of the extended surfaces.
A further object of the invention is to propose an improved method of generating steam in an extended steam generator keeping the water hold up less than 22.75 litres to come out of BRA the purview of I BR.
Yet another object is to provide less steam generator which will be easy to manufacture and operate and in which the manufacturing operational cost will be minimum.
BRIEF STATEMENT OF THE INVENTION.
According to this invention is provided an extended steam generator compressing a set of helical coals for passing cold water into the inlet and recovering steam from the outlet, said coil being disposed in a hot gas flow path and having extended heat transfer surfaces interposed between the adjacent coils, characterized in that the extended heat transfer surfaces interposed between the coils is in the form of helical coil in close contact with the coils carrying water and wherein said interposed coils are dry try tube or air cooled tubes.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS.
In the accompanying figure 1 and figure 2 of the drawings we have schematically represented the present existing concept and the concept of the invention respectively.
DETAILED DESCRIPTION OF THE DRAWINGS.
Figure 1a- shows a conventional construction where the gas side heat transfer area between the helical coils 2 has been increased by using extended heat transfer surfaces 3a. Thus, between each coil there is inter posed an extended transfer surface. The extended heat transfer surface is most preferably a carbon steel flat.
Figure 1 b shows the water flow details in the coil of figure 1a.
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Figure 2a: shows the improved construction where the same helical coil steam generator is made by inter spacing between two adjacent coils 2, a further tubular surface 3b contact with each other.
Tube which replies the flats shown in figure 1.
It will thus be appreciated in figure 2 that there is heat transfer within the inter space tube which is
conductive heat transfer compared to the conductive heat transfer in figure 1 across the carbon steel
flats. It will further be seen that the gas side heat transfer area is increased in the improved
construction. However, there is limitation in the case of Carbon steel flat.
Figure 2 b : shows the water flow details in the coil of figure 2a.
Figures 3 and 4 respectfully show schematically representation of the coil construction of figures 1a and 2a.
In both resistance the cold water is allowed into lower most tube of the coil and it is pumped through the coil. The water passing through the coil absorbs heat from the gas side and leaves the top tube of the coil as steam from where it has sent to a conventional steam water separator. Between figure 1a and 2a will be appreciated that while there is heat transfer to the water in the coil in an identical manner in both the cases from the hot gases, in the instance of Figure 1a the extended flat surface absorbs by conduction and transfer the same to the tube again by conduction. However, in the construction figure 2a the inter spaced tube absorbs heat from the hot gases by conduction which is absorbed by the dry air which transfer the heat to the adjacent tube of the coil in a fast and efficient manner.
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We Claim:-
1) An extended steam generator compressing a set of helical coals for passing cold water into the inlet and recovering steam from the outlet, said coil being disposed in a hot gas flow path and having extended heat transfer surfaces interposed between the adjacent coils, characterised in that the extended heat transfer surface s interposed between the coils is in the form of helical coil in close contact with the coils carrying water and wherein said interposed coils are dddry try tube or air cooled tubes.
2) And extended steam generator substantially as herein described with reference to the figures of the accompanying drawings.

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ABSTRACT
TITLE: Ah extended steam generator.
There is proposed, an extended steam generator compressing a set of helical coals for passing cold water into the inlet and recovering steam from the outlet, said coil being disposed in a hot gas flow path and having extended heat transfer surfaces interposed between the adjacent coils, characterized in that the extended heat transfer surface s interposed between the coils is in the form of helical coil in close contact with the coils carrying water and wherein said interposed coils are dry try tube or air cooled tubes.
6.