PROVISIONAL PATENT APPLICATION
Title: Embossing station for lengthwise-multiple enhanced surfaces on metal strips
Inventor: Vivek M. Wasekar
Organisation: TATA STEEL LIMITED, Jamshedpur, India
1. Field of Application
The invention is for the manufacturing of lengthwise-multiple enhanced surfaces on metal strips. These enhanced surfaces are typically used in heat transfer applications for improving the heat transfer from a plain, smooth surface and to control the heat transfer coefficient of a heat transfer surface or tube when used as lengthwise-multiple enhanced surfaces. Typical applications include, single-phase convection, boiling and condensation, among others.
2, Background of the Invention
Embossing on one side of a metal strip is carried out by guiding the strip between an embossing roll with a surface design complementary to the desired enhancement pattern on the strip surface and a support roll. In tubeside (or inside) enhancement for heat transfer generally this approach is applied before the tube forming process. Chiang, et al. (US Patent No. 5458191) presents this to enhance thermal performance of a heat transfer tube by roll embossing the enhancement pattern on one surface of the metal strip before the strip is formed
1

into a tube by roll forming and seam welding. This provides an economical approach to produce internally enhanced heat transfer tubes.
Gaffaney, et af. (US Patent No. 5975196) used two embossing stations to produce the pattern of ribs and notches on one side of flat metal strip before roll forming the strip into tubular shape with embossed pattern on the interior of the tubular shape.
In above approaches, enhancement pattern is uniform along the circumference of the tube. Variation in peripheral direction of the enhancement pattern on the inside of a heat transfer tube is presented by Walther, et al. (US Patent No. 6722420). They use embossing to obtain enhancement patterns on one side of metal strip by subjecting the metal strip to one-step embossing.
In all the above patents, embossing is used to obtain tubeside (or inside) enhancement with either uniform or non-uniform enhancement pattern(s) along the tube periphery (or circumference). Present invention discloses an approach that uses embossing to obtain lengthwise-multiple enhanced surfaces for tubeside (or inside) enhancement. This type of enhancement approach provides control over heat transfer coefficient along the length of heat transfer tube. The embossing is carried out using an approach, which presents modification to the roil arrangement presented by Halmos (2006). As presented by Halmos (2006), roll forming line has a metal channel-plastic roller assembly used in the conveyors, where automatically inserted plastic rolls are enclosed into the conveyor channel. These plastic rolls have smooth surfaces and cannot make enhancement patterns on the metal strip surface. Present invention employs metal embossing roils with surface designs complementary to the desired enhancement patterns on the strip surface in a metal channel-roller assembly. This creates enhancement patterns on one side of the metal strip, which passes between these embossing rolls and the support roll. The embossing rolls are
2

moving in the metal conveyor channel, which moves around the two rolls, one of which is used to apply force required for embossing. The desired enhancement pattern lengths can be obtained through the variations of the embossing roll designs (size, shape and other relevant parameters), distance(s) between two embossing rolls, the distance between the rolls carrying the conveyor channel and the sizes of these rolls. Additionally, variations in enhancement patterns can be obtained with the patterns on the embossing rolls in addition to some of the factors mentioned above. This approach thus provides an enhanced heat transfer surface, which can be formed into a tube leading to tubeside enhancement with control over heat transfer coefficient along its length.
3. Summary of the Invention
Following points summarise this invention:
1. Lengthwise control over heat transfer coefficient for a heat exchange
surface or tube using multiple enhancement patterns along the length
2. Metal embossing rolls with surface designs complementary to the desired
enhancement patterns on the strip surface in the metal channel-roller
assembly of embossing station
3. Metal strip is passed between the metal embossing rolls and the support
roll
4. Lengthwise-multiple enhancement patterns on one side of metal strip are
produced for tubeside (inside) enhancement
5. The enhancement pattern lengths can be obtained through the variations
of the embossing roll designs (size, shape and other relevant parameters),
distance(s) between two embossed rolls, the distance between the rolls
carrying the conveyor channel and the sizes of these rolls
4.
6. Variations in enhancement patterns can be obtained with the patterns on the embossing rolls in addition to some of the factors mentioned above in 5
4. Brief Description of the Drawings
Figure 1 presents schematic of embossing station having metal channel -roller assembly using metal embossing rolls for obtaining lengthwise multiple enhancement patterns for enhanced heat transfer applications.
As depicted in the above schematic, the rolls (1) and (3) carry metal conveyor channel (5) having metal embossing rolls (4). The metal strip (6) on which lengthwise- multiple enhanced surfaces are to be made is passed between the support roll (2) and the metal embossing rolls (4). The metal embossing roll designs (size, shape and other relevant parameters), distances between them, the distance between the rolls (1) and (3) carrying the conveyor channel and the sizes of these rolls give the variations as desired by the required multiple enhanced surfaces with respect to the enhancement patterns and their lengths. Additionally, variations in enhancement patterns can be obtained with the patterns on the embossing rolls in addition to some of the factors mentioned above.
4

Fig. 1 Schematic of embossing station having metal channel - roller assembly for lengthwise-multiple enhanced surfaces for heat transfer (Not to scale)
5. Detailed Description
Lengthwise-multiple enhanced surfaces are useful for controlling heat transfer coefficient. This helps in the designing of compact heat transfer surfaces and also improves efficiency and cost-effectiveness. The present invention discloses an approach, which is economical and uses embossing for producing such enhanced surfaces. This embossing approach can be used in a continuous fashion with the tube forming mill operations. With enhanced surfaces produced on one side of the metal strip, tubeside (or inside) enhancement can be obtained, which finds applications in single-phase convection, boiling and condensation, among others.
The approach disclosed by the present invention uses embossing station having metal channel - roller assembly for producing lengthwise multiple
5

enhanced surfaces for heat transfer. The metal strip to be embossed is passed through the embossing station. The metal embossing rolls are moving in the metal conveyor channel. These metal embossing rolls produce the enhanced surfaces on one side of the metal strip. The metal embossing roll designs (size, shape and other relevant parameters), distances between them, the distance between the rolls carrying the conveyor channel and the sizes of these rolls give the variations as desired by the required multiple enhanced surfaces with respect to the enhancement patterns and their lengths. Additionally, variations in enhancement patterns can be obtained with the patterns on the embossing rolls in addition to some of the factors mentioned above.
6

Claims:
1. Embossing station, which comprises of support roll and rolls carrying
metal conveyor channel having metal embossing rolls for lengthwise-
multiple enhanced surfaces on metal strips
2. The use of metal channel - roller assembly for obtaining desired
lengthwise-multiple enhanced surfaces with respect to the enhancement
patterns and their lengths
3. The manufacturing of lengthwise-multiple enhanced surfaces on one side
of metal strips for control of heat transfer coefficient along the length of
heat transfer surface or tube
4. The lengthwise-multiple enhanced surfaces on one side of metal strips for
application as enhanced heat transfer surface
5. The lengthwise-multiple enhanced surfaces on one side of metal strips,
which then are formed into tube for tubeside (or inside) heat transfer
enhancement.
6

Referred Patents
1. Chiang, R.H.L. and Esformes, J.L, 1995, "Heat transfer tube", US Patent
No. 5,458,191.
2. Gaffaney, D.P., Spencer, S.J., Bennette, D.L, Heiskanen, H.T., Riggs,
G.L., Rottmann, E.G., and Satterly, J.M., 1999, "Heat transfer tube", US
Patent No. 5,975,196.
3. Walther, C. and Wamsler, R., 2004, "Internally finned heat transfer tube
with staggered fins of varying height", US Patent No. 6,722,420.
Reference
1. Halmos, G.T., Roll Forming Handbook, Taylor & Francis, Boca Raton, 2006, Fig. 4.137, pp. 4-58.

Following points summarise this invention:
1. Lengthwise control over heat transfer coefficient for a heat exchange
surface or tube using multiple enhancement patterns along the length
2. Metal embossing rolls with surface designs complementary to the desired
enhancement patterns on the strip surface in the metal channel-roller
assembly of embossing station
3. Metal strip is passed between the metal embossing rolls and the support
roll
4. Lengthwise-multiple enhancement patterns on one side of metal strip are
produced for tubeside (inside) enhancement
5. The enhancement pattern lengths can be obtained through the variations
of the embossing roll designs (size, shape and other relevant parameters),
distance(s) between two embossed rods, the distance between the rolls
carrying the conveyor channel and the sizes of these rolls
6. Variations in enhancement patterns can be obtained with the patterns on the embossing rolls in addition to some of the factors mentioned above in 5