Title of Invention

A PROCESS OF CONFIGURATING MICROSIZED CHANNELS HAVING IMPROVED INCLINATION AND FOR ENHANCEMENT OF BOILING HEAT TRANSFER OVER PLANE SURFACE

Abstract Accordingly, there is provided a process of configurating microsized channels having improved inclination and geometry for substantial enhancement of boiling heat transfer over plane surface. The process includes Initially, surfaces with tunnels of constant width (0.25mm), constant pitch (2 mm) and constant depth (2mm) from the top surface, are developed. Variations in respect of the inclination of the tunnel including the additional geometrical feature at the tunnel base is selected. To differentiate between the different tunnel geometries, a hexa-character symbolic specification has been adapted. For example; unidirectional tunnel geometry with vertical tunnel (90° with horizontal), 2 mm pitch, 2 mm depth, 0.25 mm width and Circular base geometry is denoted by U-90-2-2-0.25-Cir. Surfaces are prepared by wire-electro discharge machining (Wire-EDM or WEDM). Micro channel fabrication operation with one machining pass is conducted using a low sparking energy by applying 70 to 100V, and a maximum current of 6 to 10A with 0.08 to 1.02 µm ON and OFF time pulse durations. Demineralized water of high insulation resistance is used as a dielectric medium. Surface is cleaned thoroughly by alkaline cleaner, acid cleaner and water mixture to remove oil or grease from it after preparation. The invention further relates to a device for determining the boiling characteristics of enhanced heat transfer surfaces. The device is configured to determine the pool boiling heat transfer from horizontal, smooth or structured surfaces. The main components of the device are a boiling vessel , a heater assembly , a reflux condenser , a top cover , power supply and instrumentation . The cylindrical boiling vessel, stores the liquid pool and forms a top part of the device. Liquid pool rests on a bakelite plate which also facilitates a horizontal test plate to be in contact with the liquid and resist the liquid to enter in the heater assembly . The horizontal test plate is a part of the heater assembly and it protrudes inside the boiling vessel . A copper plate is used as the test surface.
Full Text -2-
FIELD OF INVENTION
The present invention relates to a technique for enhancing the boiling heat transfer coefficient. More particularly, the invention relates to a process of configurating microsized channels having improved inclination and geometry for substantial enhancement of boiling heat transfer over plane surface. The invention further relates to a device for determining the boiling characteristics of enhanced heat transfer surfaces.
BACKGROUND OF INVENTION
The passive technique of increasing boiling heat transfer by providing different treated surfaces has been investigated extensively for the last eight decades. Surfaces have been designed to provide increased number of nucleation sites and to promote vapor removal including replenishment of the liquid phase. These techniques have also been exploited commercially due to its obvious advantages. Techniques to mass produce such surfaces have been developed for both planner and cylindrical (internal and external) surfaces. Some of the commonly used techniques for the enhancement of heat transfer coefficient are as under:
(a) Roughened surface: The simplest method for enhancing the boiling heat transfer coefficient is by roughening the test surface. Jacob and Fritz [1931] investigated the effect of surface finish on nucleate boiling performance and concluded that roughness can improve the boiling performance. Kurihari and Meyers [1960] boiled water and various organic liquid on roughened copper

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surface and obtained satisfactory result. Using high speed photography, Clark et al. [1969] identified naturally occurring pits and scratches between 8 and 80 jam widths as active boiling sites for pentane. After 80 ^m width, the trend of roughening the surface for the enhancement of boiling heat transfer begins in full bloom. But the percentage increment of heat transfer coefficient is limited in case of such type of boiling surfaces.
(b) Reentrant cavity: Griffith and Wallis [1960] first proposed that reentrant cavities will be very efficient for enhancement of boiling heat transfer by their theoretical analysis. Benjamin and Westwater [1961] were apparently the first to construct a reentrant cavity and demonstrate its superior performance as a vapor trap. Later in the mid-1960s, industrial researches started to achieve the goal of an enhanced boiling surface for commercial application using reentrant cavities. But the continual demand for incremental heat transfer coefficient leads the researchers to search more enhancement techniques.
c) Porous coating: One of the first surfaces developed specifically to enhance nucleate pool boiling by the porous sintered metallic coating by Thome [1995]. The 'particle spraying' technique was recently applied by You et al. [1992] to a flat horizontal surface with a 0.3-3 |im AI2O3 particle. Later O'Connor and You [1995] developed surfaces to enhance boiling heat transfer by painting it in order to increase the number of active nucleation sites. This technique is also not capable of handling large rate of heat transfer coefficient.

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d) Extended surfaces: The use of extended surfaces to aid heat transfer has
been routinely practiced for decades. The standard method for achieving greater
heat transfer rates for a given heat exchanger volume in gas flows is to add
extended surfaces, normally in the form of fins. Current interest in fins for
enhancement of convective heat transfer includes developments of
discontinuities called louvers in the fin, and finning inside, as well as outside
tubes. A good amount of enhancement has been reported by these types of
surfaces.
e) Tunnel and pore type surfaces: Fujie et al. [1977], Saier et al. [1979],
Fujikake [1980] developed various reentrant tunnel and pore type surfaces and
patented them that are used for various heat transfer application. Recently
Ramaswamy et al. [2002] studied bubble growth using high speed photography
(1500 frames/sec) on micro-porous structures over subsurface tunnels immersed
in a pool of dielectric coolant (FC-72). They used wafer dicing and wet etching to
fabricate a net of interconnected micro-channels on silicon wafer. This is the
most efficient manner of surface modification developed so far for the
enhancement of boiling heat transfer.
Tunnel type of surface modification was first introduced by Kun and Czikk [1969], who described a method to score a flat aluminum plate with closely pitched parallel grooves (0.13 mm pitch) and 0.25 mm deep. The plate was scored again perpendicular to the first set of grooves. This forms subsurface

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cavities with restricted opening at the top which showed a better performance for various liquids. In 1970 Webb developed bent fin surface and reported that this type of surface is capable of reducing a large amount of degree of superheat for a fixed heat flux.
Arshad and Thome [1983] conducted flow visualization from tunnel type surfaces to understand the mechanism of boiling inside the channels. This study confirmed that the primary mechanism of heat transfer inside the channels was evaporation of the thin liquid menisci in sharp corners. The study also showed that the vapor initiation was from one of the sharp corners and quickly spread to occupy a large portion of the channel volume.
Later on Hahne et al. [1991] experimentally and theoretically studied the effect of pool boiling heat transfer on tube with tunnel geometry. Hubner and Kunstler [1997] developed trapezoid-shaped, T-shaped and Y-shaped tunnels on sandblasted tubular surface and boiled fluorinated hydrocarbon on these tubes. They reported that trapezoid-shaped tunnels produced much better performance that plain tubes. T-shaped and Y-shaped tunnels are enhancing the boiling performance further.
Webb and Pais [1992] developed five different horizontal tunnels over tubular surfaces by wire electrode discharge machining process. Pool boiling data are provided at 40°F(4°C) and 80°F (27°C) for five refrigerants boiling on a plain tube, a GEW A K26 integral-fin tube, and three enhanced tubes. The pool boiling coefficients for alternate refrigerants R-123 and R-l 34a are within 10% of the values for R-ll and R-12, respectively, for all tubes, except the Turbo-B with R-11/23.

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Recently, Chien and Webb [1998] conducted high-speed visuali (100 frames/s) of boiling in R-123 from a finned-tube which was covered with a thin sheet and had pores at regular intervals (Fig. 1). The bubble departure diameter, frequency of bubble formation and the bubble site density were measured. The bubble growth data showed bubbles departing at a faster rate compared to those on a plain surface. The study concluded that the bubble formation phenomenon was thus different than that on a plain polished surface. The bubble data were used to develop a semi-analytical model for the boiling process.
Ghiu et al.[2001] performed a visualization study of pool boiling from transparent quartz structures of the reentrant form. The channel widths studied were 0.090 mm and 0.285 mm. The top of the structures was covered with a quartz plate having the same overall dimensions (10 mm X 10 mm X lmm ). Three boiling regimes were identified: slug formation (in either top or bottom channels), slug migration between the top and bottom channels and slug predominance (most of channels vapor filled). Their study did not contain data for structures made of higher thermal conductivity materials (copper, silicon).
Rajalu et al. [2004] carried out experimental investigation for pool boiling of acetone, iso-propanol, ethanol and water, at atmospheric pressure, on single horizontal reentrant cavity tubes of brass. The boiling heat transfer coefficient has been found to increase with the rise in heat flux and it is lowered with the reduction in cavity mouth size. They also developed a correlation to predict the boiling heat transfer coefficient as a function of heat flux and cavity mouth size.

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Thus, several techniques are already available for the enhancement of boiling heat transfer coefficient. The most widely used passive techniques are those involving the modification of surface geometry. Rough surface, treated surface, extended surface are attractive because of its capability of producing high boiling performance for lower temperature rise. Reentrant cavities and tunnels are also popular nowadays. The main drawback with most of the prior art passive techniques is the manufacturing intricacy. This restricts the use of these surfaces for various components for thermal devices. There is no easy and simple surfaces prepared and/or, proposed for the enhancement of boiling heat transfer coefficient.
OB3ECTS OF THE INVENTION
It is therefore an object of the present invention to propose a process of configurating micro sized channels having improved inclination and geometry for substantial enhancement of boiling heat transfer over plane surface.
Another object of the present invention is to propose a process of configurating micro sized channels having improved inclination and geometry for substantial enhancement of boiling heat transfer over plane surface which are easy to desigh, and can be manufactured by adapting simpler non-conventional machining processes.
A yet another object of the present invention is to propose a process of configurating micro sized channels having improved inclination and geometry for substantial enhancement of boiling heat transfer over plane surface which achieves high heat transfer coefficient using simple reentrant geometries below the horizontal and inclined tunnels.

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A further object of the present invention is to propose a process of configurating micro sized channels having improved inclination and geometry for substantial enhancement of boiling heat transfer over plane surface which eliminates typical-manufacturing process like chemical etching, chemical milling and similar others, to produce reentrant shape.
Another object of the present invention is to propose a process of configurating micro sized channels having improved inclination and geometry for substantial enhancement of boiling heat transfer over plane surface which suggests the angle of inclination for the micro channels to maximize the rate of heat transfer.
A still further object of the invention is to propose a device for determining the boiling characteristics of enhanced heat transfer surfaces.
SUMMARY OF INVENTION
Accordingly, there is provided a process of configurating microsized channels having improved inclination and geometry for substantial enhancement of boiling heat transfer over plane surface. The process includes Initially, surfaces with tunnels of constant width (0.25mm), constant pitch (2 mm) and constant depth (2mm) from the top surface, are developed. Variations in respect of the inclination of the tunnel including the additional geometrical feature at the tunnel base is selected. To differentiate between the different tunnel geometries, a hexa-character symbolic specification has been adapted. For example; unidirectional tunnel geometry with vertical tunnel (90° with horizontal), 2 mm pitch, 2 mm depth, 0.25 mm width and Circular base geometry is denoted by U-90-2-2-0.25-Cir. Surfaces are prepared by wire-electro discharge machining (Wire-EDM or WEDM). Micro channel fabrication operation with one machining pass is conducted using a low sparking energy by applying 70 to 100V, and a

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maximum current of 6 to 10A with 0.08 to 1.02 ^m ON and OFF time pulse durations. Demineralized water of high insulation resistance is used as a dielectric medium. Surface is cleaned thoroughly by alkaline cleaner, acid cleaner and water mixture to remove oil or grease from it after preparation.
The invention further relates to a device for determining the boiling characteristics of enhanced heat transfer surfaces.
The device is configured to determine the pool boiling heat transfer from horizontal, smooth or structured surfaces. The main components of the device are a boiling vessel , a heater assembly , a reflux condenser , a top cover , power supply and instrumentation . The cylindrical boiling vessel, stores the liquid pool and forms a top part of the device. Liquid pool rests on a bakelite plate which also facilitates a horizontal test plate to be in contact with the liquid and resist the liquid to enter in the heater assembly . The horizontal test plate is a part of the heater assembly and it protrudes inside the boiling vessel . A copper plate is used as the test surface.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Figure 1- shows a typical Wire-EDM machine,
Figure 2(a)- shows a straight unidirectional surface geometry according to the invention,
Figure 2(b)- shows a straight unidirectional surface geometry with circular base, according to the invention,

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Figure 2 (c )- shows a 60° inclined unidirectional surface geometry, according to the invention,
Figure 2(d)- shows a 60° inclined unidirectional surface geometry with circular base, according to the invention,
Figure 3(a)- shows a pictorial view of straight unidirectional surface geometry according to the invention.
Figure 3(b)- shows a 60° inclined unidirectional surface geometry, according to the invention
Figure 3(c) - shows a straight unidirectional surface geometry with circular base according to the invention,
Figure 3(d)- shows a 60° inclined unidirectional surface geometry with circular base according to the invention.
Figures 4(a) to 4 (d)- show cross-sectional view of surface geometry straight
tunnel with various degree of inclination according to the invention.
Figures 5(a) to 5 (d)- show cross sectional view of surface geometry of straight
circular base tunnel with various inclinations according to the invention.

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Figure 6 (a)- a schematic view of a test device according to the invention. Figure 6 (b)- detailed view of heater assembly of the device of Figure 6(a).
Figure 7- a graphical representation of boiling curves for enhanced and plane surfaces according to the invention.
Figure 8- shows a boiling curve for various inclination angles for straight tunnel according to the invention.
Figure 9- graphically shows the effect of angle of inclination in straight circular base tubbel according to the invention.
Figure 10- shows an overall effect of tunnel inclination at 105°C according to the invention.
Figure 11- shows a qualitative comparisons of the enhance surfaces according to the invention.
DETAIL DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
Initially, surfaces with tunnels of constant width (0.25mm), constant pitch (2 mm) and constant depth (2mm) from the top surface, are developed. Variations in respect of the inclination of the tunnel including the additional geometrical feature at the tunnel base is selected. To differentiate between the different tunnel geometries, a hexa-character symbolic specification has been adapted. For example; unidirectional tunnel geometry with vertical tunnel (90° with horizontal), 2 mm pitch, 2 mm depth, 0.25 mm width and Circular base

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geometry is denoted by U-90-2-2-0.25-Cir as explained in Table 1. The details of all these surfaces developed are given in Table 2.

Arrangement Inclination Pitch Depth Width Base
with geometry
U-90-2-2- horizontal
0.25-N line
Unidirectional 90 2 2 0.25 Nil
Table 1 Significance of hexa-character symbol used for surface nomenclature
Surfaces are prepared by wire-electro discharge machining (Wire-EDM or WEDM). WEDM is a machining method in which thermo electric energy (8000-12000°C) is applied through a dielectric medium (14) between the tool electrode (15) and an electrically conductive work piece (16). The material removal is achieved by controlled erosion through a series of repetitive sparks between the electrodes, that is,between the work-piece (16) and a wire (17). A schematic view of the process is shown in Figure 1. Micro channel fabrication operation with one machining pass is conducted using a low sparking energy by applying 70 to 100V, and a maximum current of 6 to 10A with 0.08 to 1.02 ^m ON and OFF time pulse durations. A copper electrode (15) coated with a zinc layer of 0.05 to 1.50 is used. The plate (16) is kept always connected to the positive polarity and the electrode (15) to the negative polarity. Demineralized water of high insulation resistance is used as a dielectric medium (14). Surface is cleaned thoroughly by alkaline cleaner, acid cleaner and water mixture to remove oil or grease from it after preparation. The geometry and the pictorial view of the surfaces are shown in Figure 2 and 3 respectively. Experiments results show a clear enhancement as depicted below:

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Geometry
Serial Name Specification
No. Angle Pitch Width Depth Base
geometry
1 Straight U-90-2-2- 90 2 0.25 2 Nil
unidirectional 0.25-N
l2 60° inclined U-60-2- 60 2 0.25 1.732 Nil
unidirectional 1.732-0.25-N
3 45° inclined U-45-2- 45 2 0.25 1.414 Nil
1.414-0.25-N
4 30° inclined U-30-2-1- 45 2 0.25 1 Nil
0.25-N
5 Straight U-90-2-2- 90 2 0.25 2 ( Circular
unidirectional 0.25-Cir
with circular
base
6 60° inclined U-60-2- 60 2 0.25 1.732 Circular
unidirectional 1.732-0.25-
with circular Cir
base
7 45° inclined U-45-2- 60 2 0.25 1.414 Circular
unidirectional 1.414-0.25-
with circular Cir
base
8 30° inclined U-30-2-1- 60 2 ( ).25 1 Circular
unidirectional 0.25-Cir
with circular
base
Table 2 Characterization of tunnel shape and geometry

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To clearly bring out the effect of inclination, a second set of surfaces have been configured where the angles are varied keeping the tunnel length same. Four discrete angles-90° (Vertical, 60°, 45° and 30°) have been adapted. Additionally, same tunnel geometries with circular pocket at the base have also been developed. The surfaces are depicted in Figure 4 and 5.
Data on Table-2 show that the enhancement effect increases with the decrease in angle of inclination. But after some limit (45°) boiling performance starts to reduce with the further decrease in inclination.
The invention further proposes a device for determining the boiling characteristics of enhanced surfaces. The device shown in Figure 6 ( a and b), primarily constitutes a pool boiling device. The device is configured to determine the pool boiling heat transfer from horizontal, smooth or structured surfaces. The main components of the device are a boiling vessel (1), a heater assembly (2), a reflux condenser (8), a top cover (10), power supply and instrumentation (12 and 13). The cylindrical boiling vessel (I), stores the liquid pool and forms a top part of the device. Liquid pool rests on a bakelite plate which also facilitates a horizontal test plate (3) to be in contact with the liquid and resist the liquid to enter in the heater assembly (2). The horizontal test plate (3) is a part of the heater assembly (2) and it protrudes inside the boiling vessel (1). A copper plate is used as the test surface. The copper plate is press fitted to a copper block (4) and which acts as the main part of the heater assembly (2). The detail of the heater assembly is shown in Fig 1. a. The heater assembly (2) consists of four cartridge heaters (5) for uniform heating of the cylinder. The side (6) and bottom faces (7) of the cylinder are heavily insulated to facilitate unidirectional heat flow only towards the top.

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Fiber blanket insulation is provided around the copper cylinder while its bottom is lagged by a ceramic insulation. The heating assembly (2) is placed inside a brass casing. Teflon bush is disposed radially around the extended test plate (3) to restrict the nucleation from the vertical surfaces. Liquid evaporated from the pool is condensed in the reflux type condenser (8) and the condensate returns to the pool due to gravity. This maintains a constant pool height over the boiling surface during the operation. A heater coil (9) is provided for initial heating of the pool and maintenance of the pool temperature during the test-run. The Boiling vessel (1) is covered in the top by a bakelite plate which acts as a top cover (10). Provisions are made for allowing auxiliary heater leads to come out of the boiling vessel (1) and the generated vapor to enter into the condenser (8). Power supply to the primary and secondary heaters is varied by controlling variacs. To measure the average temperature of the test plate (3) , a copper constantan (T type) sheathed thermocouple (shown in figure 6.b) is embedded inside it through its bottom face. It is placed below the top surface of the test plate (3) to get the accurate temperature reading.
Pool temperature is also measured by an insulated copper constantan thermocouple placed above the test surface. Power input to the heaters and voltage signals from the thermocouples are analyzed and stored using a data acquisition means (12) and a personal computer (13). The heat flux is determined by recording the voltage and current input to the heater assembly. To prevent the leakage from the Copper-Teflon contact line and Bakelite-Teflon contact line, high temperature thermal paste is used. This ensures leak-proof joints up to a temperature of around 1000°C. A circular gasket is provided in the glass bakelite junction to resist the vapor leakage from the boiling vessel (1). A digital camera with a low frame rate is used to record the images of the growing bubble and the boiling phenomena. Three leveling screws (11) are used to make the test plate (3) perfectly horizontal.

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After degassing the pool by vigorous boiling (with the help of the pool heater) power is given to the heater. Power supply to the heater is increased in small steps such that steady state conditions are achieved for a particular value of test plate temperature. All the tests are carried-out under saturated pool condition. In the device, the test surface is fitted to obtain the boiling performance of the augmented surfaces. Results obtained from the tests are compared with the performance of a plane surface to get qualitative information for enhanced surfaces.
Firstly, a straight unidirectional parallel tunnel (U-90-3-2-0.4-N) is used for the test, and the results obtained are shown in figure 7. From the figure, it can be seen that U-90-3-2-0.4-N shows a definite enhancement over plane surface.
To obtain still better enhancement, a straight tunnel with circular base (U-90-3-2-0.4-Cir) is then adapted. It serves both the effect of re-entrant cavity and helps smooth removal of vapor. Using this surface, a boiling test has been done and a substantial amount of enhancement has been obtained (Figure 7). Performance of U-90-3-2-0.4-Cir is better than U-90-3-2-0.4-N. Actually the circular base tunnel acts as a vapor pocket at the base and helps to maintain continuous liquid menisci inside the tunnel circular base.
To study the effect of inclination, a second set of test is undertaken by adapting 4 different angle of inclination (90°, 60°, 45°, 30°). Both straight tunnels and the inclined tunnels are adapted for this test.

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Figure 8 presents the heat transfer characteristics from surfaces with straight tunnels of different inclination. Compared to plane surface, all the surfaces have high heat transfer rate as expected. All the surfaces having inclined tunnels exhibit higher rate of heat transfer compared to the surface with vertical tunnels. But interestingly, the rate of heat transfer monotonically increases when the inclination angle is changed from 90° (vertical ) to 60° and further from 60° to 45°. However, when the inclination angle is changed to 30°, the rate of heat transfer decreases.
Finally, to determine the effect of circular base at the end of the inclined tunnel on the heat transfer characteristics, the boiling curves obtained from such surfaces are plotted and shown in Figure 9. In this case also the rate of heat transfer increases as the inclination angle decreases from 90° to 60° to 45°. But thereafter it decreases as the inclination angle is changed from 45° to 30°. This corroborates the earlier observation presented in figure 8.
In Figure 10 a comparative view for the heat flux with respect to angle of inclination is plotted at a fixed degree of superheat to get a realistic view of the effect of angle of inclination.
From the test results, it may be concluded that continuous longitudinal tunnels can be another option for augmentation. Two geometrical configurations of the tunnel geometry offer definite advantage.

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• Firstly, inclined tunnels show better performance compared to vertical
tunnels. But after a certain degree of inclination, the heat transfer
coefficient decreases.
• Secondly, reentrant geometry like circular pocket at the end of the tunnel
base enhances the boiling heat transfer further. It may further be
mentioned that such geometry needs the least manufacturing effort.
A qualitative comparison among all the surfaces prepared along with plane surface has been shown in Figure 11 to get an overview of the characteristics of the enhanced surface.

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WE CLAIM:
1. A process of configurating microsized channels having improved
inclination and geometry for substantial enhancement of boiling heat
transfer over plane surface, comprising the steps of:
- developing surfaces with tunnels of constant width, constant pitch,
and constant depth;
- configurating variations in respect of the inclination of the tunnel
including additional geometrical features by adapting a hexa-
character symbolic specification; and
- cleaning the developed surface by alkaline cleaner, acid cleaner
and water mixture.

2. The process as claimed in claim 1, wherein the hexa-character symbolic
specification comprises unidirectional tunnel geometry with vertical tunnel
and circular base.
3. The process as claimed in claim 1, wherein the surfaces of constant width,
constant pitch, and constant depth are configured by adapting wire-
electro discharge machining, and wherein micro-channel fabrication being
conducted in one machining pass using a low sparking energy.
4. The process as claimed in claims 1 to 3, wherein the micro-channel
fabrication is conducted by applying 70 to 100V, and a maximum current
of 6 to 10 amp with 0.08 to 1.02 ^m ON and OFF time pulse duration.

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5. The process as claimed in claim 1 or 3, wherein the surfaces with tunnels
of constant width, constant pitch, and constant depth is prepared by
applying thermo electric energy (8000-12000°C) including application of a
dielectric medium between a tool electrode and an electrically conductive
work piece.
6. The process as claimed in claim 5, wherein the dielectric medium is
dimenarilised water of high insulation resistance.
7. The process as claimed in claim 5, wherein the material removal is carried
out by controlled erosion through a series of repetitive sparks between the
electrodes.
8. A pool boiling device for determining the boiling characteristics of
enhanced surfaces comprising:

- a boiling vessel (1) having a top cover (10) for storing the liquid
pool, the side and bottom faces (6,7) being insulated to facilitate
unidirectional heat flow only toward upper direction;
- a horizontal test plate (3), disposed in contact with the liquid via at
least three leveling screws (11);
- a reflex type condenser (8) for condensing the liquid evaporated
from the vessel (1);

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at least two copper constantan sheathed thermocouple one each, placed below and above the test plate (3) to obtain temperature readings of the liquid pool;
a heater assembly (2) comprising a copper block (4), and at least four cartridge heaters (5) protrudingly placed adjacent the vessel (1) for uniform heating of the vessel (1);
an auxiliary heater coil (9) provided for initial heating of the liquid pool and maintenance of the temperature during device operation;
power supply sources variable by controlling variacs, to the primary (5) and the auxiliary (9) heaters;
a data acquisition means (12) with a PC(13) for measuring, analyzing and storing data relating to power input and voltage signals from the thermocouples; and
a digital camera for recording images of the growing bubble and the boiling phenomenon.

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9. A process of configurating microsized channels having improved inclination and geometry for substantial enhancement of boiling heat transfer over plane surface, as substantially described and illustrated herein with reference to the accompanying drawings.
10. A pool boiling device for determining the boiling characteristics of enhanced surfaces as substantially described and illustrated herein with reference to the accompanying drawings.
Dated this 19th day of JANUARY 2007

Accordingly, there is provided a process of configurating microsized channels having improved inclination and geometry for substantial enhancement of boiling heat transfer over plane surface. The process includes Initially, surfaces with tunnels of constant width (0.25mm), constant pitch (2 mm) and constant depth (2mm) from the top surface, are developed. Variations in respect of the inclination of the tunnel including the additional geometrical feature at the tunnel base is selected. To differentiate between the different tunnel geometries, a hexa-character symbolic specification has been adapted. For example; unidirectional tunnel geometry with vertical tunnel (90° with horizontal), 2 mm pitch, 2 mm depth, 0.25 mm width and Circular base geometry is denoted by U-90-2-2-0.25-Cir. Surfaces are prepared by wire-electro discharge machining (Wire-EDM or WEDM). Micro channel fabrication operation with one machining pass is conducted using a low sparking energy by applying 70 to 100V, and a

maximum current of 6 to 10A with 0.08 to 1.02 ^m ON and OFF time pulse durations. Demineralized water of high insulation resistance is used as a dielectric medium. Surface is cleaned thoroughly by alkaline cleaner, acid cleaner and water mixture to remove oil or grease from it after preparation.
The invention further relates to a device for determining the boiling characteristics of enhanced heat transfer surfaces.
The device is configured to determine the pool boiling heat transfer from horizontal, smooth or structured surfaces. The main components of the device are a boiling vessel , a heater assembly , a reflux condenser , a top cover , power supply and instrumentation . The cylindrical boiling vessel, stores the liquid pool and forms a top part of the device. Liquid pool rests on a bakelite plate which also facilitates a horizontal test plate to be in contact with the liquid and resist the liquid to enter in the heater assembly . The horizontal test plate is a part of the heater assembly and it protrudes inside the boiling vessel . A copper plate is used as the test surface.

Documents:

00070-kol-2007-correspondence-1.1.pdf

00070-kol-2007-correspondence-1.2.pdf

00070-kol-2007-form-1-1.1.pdf

00070-kol-2007-form-18.pdf

0070-kol-2007 abstract.pdf

0070-kol-2007 assignment.pdf

0070-kol-2007 claims.pdf

0070-kol-2007 correspondence others.pdf

0070-kol-2007 description(complete).pdf

0070-kol-2007 drawings.pdf

0070-kol-2007 form-1.pdf

0070-kol-2007 form-2.pdf

0070-kol-2007 form-3.pdf

70-KOL-2007-(08-05-2012)-ABSTRACT.pdf

70-KOL-2007-(08-05-2012)-AMANDED CLAIMS.pdf

70-KOL-2007-(08-05-2012)-CORRESPONDENCE.pdf

70-KOL-2007-(08-05-2012)-FORM-1.pdf

70-KOL-2007-(08-05-2012)-FORM-2.pdf

70-KOL-2007-(08-06-2012)-ABSTRACT.pdf

70-KOL-2007-(08-06-2012)-AMANDED CLAIMS.pdf

70-KOL-2007-(08-06-2012)-CORRESPONDENCE.pdf

70-KOL-2007-(08-06-2012)-FORM-1.pdf

70-KOL-2007-(08-06-2012)-FORM-2.pdf

70-KOL-2007-(11-04-2012)-CORRESPONDENCE.pdf

70-KOL-2007-(12-03-2012)-ABSTRACT.pdf

70-KOL-2007-(12-03-2012)-AMANDED CLAIMS.pdf

70-KOL-2007-(12-03-2012)-DESCRIPTION (COMPLETE).pdf

70-KOL-2007-(12-03-2012)-DRAWINGS.pdf

70-KOL-2007-(12-03-2012)-EXAMINATION REPORT REPLY RECEIVED.pdf

70-KOL-2007-(12-03-2012)-FORM-1.pdf

70-KOL-2007-(12-03-2012)-FORM-2.pdf

70-KOL-2007-(12-03-2012)-OTHERS.pdf

70-KOL-2007-(27-07-2012)-ABSTRACT.pdf

70-KOL-2007-(27-07-2012)-AMANDED CLAIMS.pdf

70-KOL-2007-(27-07-2012)-CORRESPONDENCE.pdf

70-KOL-2007-(27-07-2012)-FORM-1.pdf

70-KOL-2007-(27-07-2012)-FORM-2.pdf

70-KOL-2007-CORRESPONDENCE 1.2.pdf

70-KOL-2007-CORRESPONDENCE 1.3.pdf

70-KOL-2007-CORRESPONDENCE OTHERS 1.3.pdf

70-KOL-2007-EXAMINATION REPORT.pdf

70-KOL-2007-FORM 1-1.1.pdf

70-KOL-2007-FORM 18.pdf

70-KOL-2007-FORM 3.pdf

70-KOL-2007-FORM 8 1.1.pdf

70-KOL-2007-FORM 8.pdf

70-KOL-2007-GPA.pdf

70-KOL-2007-GRANTED-ABSTRACT.pdf

70-KOL-2007-GRANTED-CLAIMS.pdf

70-KOL-2007-GRANTED-DESCRIPTION (COMPLETE).pdf

70-KOL-2007-GRANTED-DRAWINGS.pdf

70-KOL-2007-GRANTED-FORM 1.pdf

70-KOL-2007-GRANTED-FORM 2.pdf

70-KOL-2007-GRANTED-LETTER PATENT.pdf

70-KOL-2007-GRANTED-SPECIFICATION.pdf

70-KOL-2007-OTHERS.pdf

70-KOL-2007-REPLY TO EXAMINATION REPORT.pdf

abstract-00070-kol-2007.jpg


Patent Number 253807
Indian Patent Application Number 70/KOL/2007
PG Journal Number 35/2012
Publication Date 31-Aug-2012
Grant Date 27-Aug-2012
Date of Filing 19-Jan-2007
Name of Patentee INDIAN INSTITUTE OF TECHNOLOGY
Applicant Address INDIAN INSTITUTE OF KHARAGPUR-721302
Inventors:
# Inventor's Name Inventor's Address
1 PRASANTA KUMAR DAS DEPARTMENT OF MECHANICAL ENGINEERING, IIT, KHARAGPUR-721302
2 PARTHA SAHA MECHANICAL DEPARTMENT, IIT, KHARAGPUR-721302
3 ARUP KUMAR DAS DEPARTMENT OF MECHANICAL ENGINEERING, IIT, KHARAGPUR-721302
PCT International Classification Number B63G8/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA