Title of Invention

METHOD TO IMPROVE HYDRODYNAMICS AND HEAT TRANSFER OF HYDRAULIC JUMP REGION AND HEAT TRANSFER IN JET IMPINGEMENT COOLING BY WATER.

Abstract

A method to improve hydrodynamics and heat transfer of hydraulic jump region in the process of jet impingement cooling, comprising the steps of: dissolving a surfactant additive, which is DuPont™ Zonyl® FSH in a cooling medium and forming an aqueous surfactant solution; providing an impinging jet nozzle module capable of generating an accurately equal flow rate for each nozzle; measuring temperature of the surface to be cooled by attaching thermocouple; creating a fully-developed flow via the nozzle module by using a pump such that the aqueous surfactant solution is impinged on the coolable surface at a flow- rate covering from laminar to turbulent.

Full Text

2 FIELD OF INVENTION The present invention relates to a method of Jet impingement cooling used for Run-Out-Table cooling thermal processing stage in industries such as steel. More particularly, the invention relates to a method to improve hydrodynamics and heat transfer of hydraulic jump region in the process of jet impingement cooling. BACKGROUND OF THE INVENTION Jet impingement cooling is used for Run-Out-Table cooling thermal processing stage in industries such as steel, in addition to other applications such as electronic cooling and high heat flux technology. It offers low thermal resistances and is easy to implement. Liquid jets are created using a straight tube or contracting nozzle. The cooling medium is water with laminar or turbulent jets impinging on the hot surface. When the jet strikes the hot surface, a thin stagnation-zone is formed, which offers little resistance to heat flow. The maximum heat transfer coefficients are present at the stagnation point regions. The whole field of flow after the jet strikes the hot surface consists of stagnation zone, region of boundary-layer type flow, liquid film region, region having similarity velocity profile, hydraulic jump region and the region of undisturbed flow downstream the hydraulic jump (Nakoryakov, et al., 1978). For quick cooling as in the case of steel, the surface temperature drops from its initial temperature to close to the corresponding water temperature very soon after the jet strikes. The hydraulic jump region is the region of reduced heat transfer because of number of issues mainly related to the thick water film. 3 The effects of surface tension tend to become important in the region of the hydraulic jump due to large effects of curvature (Rao and Arakeri, 1998). The heat transfer outside or external to hydraulic jump region is drastically reduced and therefore presents difficulties in removing heat from the hot surface appropriately. In multiple jet configurations, the regions of hydraulic jumps interact and effective cooling is dependent on the jet design aspects such as jet spacing, jet number, and jet flow rates, among others. During thermal processing of steel, uniform temperature establishment across the width and length of steel strip/plate is a concern because of these variable rates of heat transfer from the strip surface. It has been observed (Bush and Aristoff, 2003) that surface tension influence on the circular hydraulic jump has been shown to have useful characteristic of relaxation in hydraulic jump, that is to say, expanding smoothly to a new larger radius, which is approximately 20 to 30% larger for decrease in surface tension with the application of a small volume (1-2 drops) of surfactant (either a commercial detergent or superwetting agent) added to the glycerol-water solutions. These observations were made for laminar circular hydraulic jumps, which were formed on the surface of glycerol-water solutions in the reservoir having base made of circular glass target plate on the center of which the jet impacted. The surface tension influence was found to be most significant for jumps of small radius and small height. Addition of a surfactant (liquid Dove) to the reservoir, which reduces the surface tension from 70 to 40dyn/cm, causes the polygonal jump generated with glycerol-water solution to relax into a circular form, to become less abrupt and to expand slightly (Bush, et al., 2006). Influence of an unknown detergent on splattering of turbulent jets indicates lower Froude number behaviour, that is 4 better heat transfer as observed with water jets (Wasekar, 2007), which is representative of decrease in water film height (Rao and Arakeri, 1998). The influence of surface tension on the stagnation-point heat transfer during impingement of laminar water jets is insignificant except for low-velocity small- diameter jets (Liu, et al., 1993). For the jet diameters in the range of 0.3 to 0.6 mm, the stagnation Nusselt number is more strongly dependent on Reynolds number for initially laminar jets than fully turbulent jets due to surface-tension induced jet broadening and associated modification of the jet flow structure (Elison and Webb, 1994). In liquid film region, the nucleate boiling heat transfer coefficient has been found to increase for aqueous solutions of the surface-active agents compared to water (Shibayama, et al., 1978). There is no patent literature or prior art known to this inventor that discloses invention regarding surfactant addition to water in the field of jet impingement cooling. US patent 3846254 and GB patent 1363063 disclose the addition of surfactant to liquid to increase the rate of evaporation for channel flow or flow through evaporator. The surfactant addition is supported through the reduction in pressure, which creates foamy two-phase vapour liquid flow as the liquid is evaporated while being passed through the flow channel or evaporator. The high heat and/or mass transfer enhancement associated depends upon several factors that include, increase in vapour-liquid interfacial area, thinning of liquid layer in contact with heat transfer surface with the formation of foam network, agitation and continuous renewal of liquid film by vapour bubbles, better wetting and prevention of dryout and reduction in hydrodynamic pressure gradient. The disadvantage of this invention is that it cannot be used for the jet impingement cooling where single phase jet is used. Furthermore, Run-Out-Table cooling application presents open channel flow and foamy two-phase vapour liquid flow through a flow channel, as mentioned in above patents, is not effective because extensive foaming on the water surface can reduce heat transfer rate by blocking vapour removal and due to trapped surfactant concentration in foam. EP 5 1691143A2 disclose addition of defoaming wetting agent or a low foaming wetting agent or a wetting agent and a defoaming agent in the heat transfer fluid of a boiler system to improve heat transfer by reducing the size of bubbles forming on the surface of the element. The disadvantage of this invention is that the additives used are applicable for system requiring bubble nucleation. The jet impingement cooling doesn't necessarily require to have boiling or bubble nucleation. This can be seen from its applications using water without surfactant additive for electronic cooling as disclosed in US patent 5228502 and cooling of a high-power solid state laser as disclosed in US 6859472. OBJECT OF THE INVENTION It is therefore an object of the invention to propose a method to improve hydrodynamics and heat transfer in the jet impingement water cooling process used in steel and other industries which overcomes the disadvantages of prior art. Another object of the invention is to propose a method to improve hydrodynamics and heat transfer in the jet impingement water cooling process used in steel and other industries which is capable of changing and improving cooling characteristics of water by addition of surfactant additives in the cooling medium. 6 A still another object of the invention is to propose a method to improve hydrodynamics and heat transfer in the jet impingement water cooling process used in steel and other industries which achieves causing a change in the surface tension of water in the process of jet impingement cooling of hot material like steel. Yet another object of the invention is to propose a method to improve hydrodynamics and heat transfer in the jet impingement water cooling process used in steel and other industries which incorporates a nozzle test section module in the process to ensure equal flow rate for each nozzle in multi nozzle configuration. A further object of the invention is to propose a method to improve hydrodynamics and heat transfer in the jet impingement water cooling process used in steel and other industries which adapts means to investigate stagnation zone interferences, hydraulic jump interactions, hydrodynamics and heat transfer during the process of cooling. A still further object of the invention is to propose a method to improve hydrodynamics and heat transfer in the jet impingement water cooling process used in steel and other industries which ensures an effective Run-Out- Table cooling of hot steel in the form of strip or plate rolling out of finishing stand. A still another object of the invention is to propose a method to improve hydrodynamics and heat transfer in the jet impingement water cooling process used in steel and other industries which is capable of removing heat without boiling or bubble nucleation. 7 Another object of this invention is to propose a method to improve hydrodynamics and heat transfer in the jet impingement water cooling process used in steel and other industries which ensures removal of heat by thinning of water film, water film conduction and evaporation at the liquid vapour interface. SUMMARY OF THE INVENTION This invention discloses a method to improve hydrodynamics and heat transfer of the hydraulic jump region and heat transfer in jet impingement cooling. The method uses known surfactant additive in water. The method additionally uses a four nozzle test section module, which is designed for equal flow rate for each nozzle and provides accurate adjustments using Tee, Elbow and Tube/Pipe connections to study the effects of nozzle spacing/pitch that help to investigate the stagnation zone interferences, hydraulic jump interactions, hydrodynamics and heat transfer. The flow rate range covers all ranges from laminar to turbulent. The surfactant concentration is small, which changes only the surface tension of water and the other properties remain the same. Jet impingement cooling is used for Run-Out-Table cooling application. Water is used as cooling medium. A commercial surfactant, DuPont™ Zonyl® FSH is used, which is a nonionic fluorosurfactant having useful wetting and spreading characteristics. Other surfactants having cooling characteristics as that of DuPont™ Zonyl® FSH are the potential candidates as surfactant additives. Surfactant(s) is/are dissolved in water that strikes/impinges on the surface to be cooled. Circular cross-sectional pipes/tubes are used for impinging jets of aqueous surfactant solution(s). Impinging jet nozzle cross-section can have cross-section other than circular. Impinging jet impinges normally on the surface 8 to be cooled. The orientation of the surface to be cooled need not necessarily be horizontal. Nozzle test section module provides accurately equal flow rate for each nozzle of a four nozzle jet impingement configuration using Tee, Elbow and Tube/Pipe connections that provide accurate adjustments to study the effects of nozzle spacing, pitch that help to investigate the stagnation zone interferences, hydraulic jump interactions and hydrodynamics & heat transfer. Improvement in impingement water jet cooling having surfactant additive in water is evaluated by comparing the jet cooling performance with that for impinging water jet(s) without surfactant additive(s). BRIEF DESCRIPTION OF THE ACCOMPANIED DRAWING Figure 1 - illustrates the schematic drawing of jet impingement cooling system according to the invention. Figure 2 - illustrates the schematic of nozzle test section module of the system according to the invention. 9 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT This invention discloses a method to improve hydrodynamics and heat transfer of the hydraulic jump region and heat transfer in jet impingement cooling. The method uses commercial surfactant additive. In water, in the aqueous impinging jets for the application of Run-Out-Table cooling, the improvement in hydrodynamics and heat transfer in the hydraulic jump region is obtained by reducing the liquid thickness or in other words by reducing the conduction resistance of the water film present over the hot steel strip/plate. Aqueous solutions of commercial surfactant additives DuPont™ Zonyl® FSH have been investigated for the impinging jet cooling flow in this invention and the results show excellent cooling characteristics for the application of interest, where the improvement in the heat transfer from the hot steel surface is experimentally found. The hot steel surface was cooled from around 800°C to temperatures of around 30°C. This invention is applicable to any other heated surface that is required to be cooled by water. The Froude number which is defined as square of jet velocity divided by the product of height of nozzle from the surface to be cooled and the acceleration due to gravity is in the range having values less that 2 or around 2. DuPont™ Zonyl® FSH is a nonionic fluorosurfactant having structure as present below (DuPont, 2001). RfCH2CH2O(CH2CH2O)xH, where Rf=F(CF2CF2)y The commercial surfactant additive DuPont™, Zonyl® FSH gives exceptionally low surface tension in aqueous solutions of the order of 17 to 22 dyn/cm for the 10 surfactant concentration range of 0.1 to 0.001% and provides better wetting and spreading characteristics. Even at very low concentrations, it delivers tremendous wetting power. In addition, in the experiments of this invention, it has been found to be stable in its aqueous solutions at high temperatures required for cooling application of interest. The surfactant additive influences the heat transfer and flow behaviour. The surfactant improves the wetting front velocity as surface tension of water is reduced. This helps in the spreading of water over the hot steel strip/plate faster. This in turn reduces the resident time. Thus, higher metal temperatures can be easily dealt with for cooling. The surfactant concentration is small, which changes only the surface tension of water and the other properties remain the same. DuPont™ Zonyl® FSH is nonhazardous, nonflammable thus making it an appropriate choice as safe and economically useful additive. The method additionally uses a four nozzle test section module as illustrated in Fig. (1), which has been designed for equal flow rate for each nozzle and provides accurate adjustments using Tee, Elbow and Tube/pipe connections to study the effects of nozzle spacing/pitch that help to investigate the stagnation zone interferences, the hydraulic jump interactions, and hydrodynamics & heat transfer. The flow rate range covers all ranges from laminar to turbulent. The surfactant concentration is small which changes only the surface tension of water and other properties remain the same. Fig. (1) shows the schematic of jet impingement cooling facility wherein hot steel strip/plate (1) is cooled using nozzles (2), which are circular tube/pipes having length sufficient to overcome the entrance effects, such that fully developed flow exists form each nozzle. The coolant (water/aqueous surfactant solution) is circulated using a pump (3). Flow rate is measured using turbine flow meter (4). The flow rate range covers all the ranges from laminar to turbulent. 11 The temperature measurements are carried out by connecting thermocouples (5) on the back side of the strip/plate. Fig 2 illustrates the schematic diagram of nozzle test section module. It is designed for equal flow rate for each nozzle. The set up provides accurate adjustment to study the effects on nozzle spacing/pitch that help to investigate the stagnation zone interferences, the hydraulic jump interactions, and hydrodynamics & heat transfer. The system also has provision for the connection of turbine flow meter (4) for low rate measurements. Circular cross-sectional pipes/tubes are used for impinging jets of aqueous surfactant solutions, wherein other sections can also be used. Nozzle test section module (6) is designed as a four nozzle jet impingement configuration using Tee, Elbow, Tube/pipe connections as shown in Fig 2. Improvement of impingement water jet cooling having surfactant additive in water is evaluated by comparing the jet cooling performance with that for impinging water jet (s) without surfactant additives. Referred Patents: 1. Sephton, H.H., 1974, "Interface Enhancement Applied to Evaporation of Liquids", US Patent 3846254. 2. Sephton, H.H., 1974, "Interface Enhancement Applied to Evaporation of Liquids", GB Patent 1363063. 12 3. Jassal, M., 2006, "An Additive", EP Patent 1691143A2. 4. Chu, R. C, Goth, G. F., Messina, G. P., Moran, K. P. and Zumbrunnen, M. L, 1993, "Cooling by use of Multiple Parallel Convective Surfaces", US Patent 5228502. 5. Betin, A. A. and Griffin, W. S., 2005, "Multi-Jet Impingement Cooled Slab Laser Pumphead and Method", US Patent 6859472B2. References: 1. Nakoryakov, V. E., Pokusaev, B. G., and Troyan, E. N., 1978, "Impingement of an Axissymmetric Liquid Jet on a Barrier", Int. J. Heat Mass Trans. Vol. 21, pp 1175-1184. 2. Rao, A. and Arakeri, J. H., 1998, "Integral Analysis Applied to Radial Film Flows", Int. J. Heat Mass Trans., vol. 41, pp. 2757-2767. 3. Bush, J. W. M. and Aristoff, J. M., 2003, "The Influence of Surface Tension on the Circular Hydraulic Jump", J. Fluid Mech., vol. 489, pp. 229-238. 4. Bush, J. W. M., Aristoff, J. M. and Hosoi, A. E. 2006, "An Experimental Investigation of the Stability of the Circular Hydraulic Jump", J. Fluid Mech., vol. 558, pp. 33-52. 5. Wasekar, V. M., 2007, "Accelerated Cooling Approaches for Run Out Table Applications", TATA SEARCH 2007, pp. 259-265, TATA STEEL. 13 6. Liu, X., Gabour, L. A., and Lienhard V., J. H. 1993, "Stagnation-Point Heat Transfer during Impingement of Laminar Liquid Jets: Analysis including Surface tension", J. heat Trans., vol. 115, pp. 99-105. 7. Elison, B. and Webb, B. W., 1994, "Local Heat Transfer to Impinging Liquid Jets in the Initially Laminar, Transitional, and Turbulent regimes", Int. J. Heat Mass Trans., vol. 37, no. 8 pp. 1207-1216. 8. Shibayama, S., Kurose, T., Suzuki, K., Katsuta, M. and Hatano, Y., 1978, "A Study on Boiling Heat Transfer in Thin Liquid Film, Part 1, in case of pure water and aqueous solution of surface-active agents as working liquid", Trans. Japan Soc. Mech. Engrs., Vol. 44, pp. 2429-2438. 9. DuPont, 2001, "DuPont™ Zonyl® FSH Fluorosurfactant" (Information on technical data). 14 We Claim 1. A method to improve hydrodynamics and heat transfer of hydraulic jump region in the process of jet impingement cooling, comprising the steps of: - Using DuPont™ Zonyl® FSH in water and forming an aqueous surfactant solution; - providing an impinging jet nozzle module capable of generating an accurately equal flow rate for each nozzle; - measuring temperature of the surface to be cooled by attaching thermocouple; - creating a fully-developed flow via the nozzle module by using a pump such that the aqueous surfactant solution is impinged on the coolable surface at a flow-rate covering from laminar to turbulent. 2. The method as claimed in claim 1, wherein the surface to be cooled comprises of hot steel strips or plates, and wherein the aqueous impinging jet is adaptable for Run-Out-Table cooling. 3. The method as claimed in claim 1 or 2, wherein the heat transfer from the steel strip/plate is achieved by reducing the conduction resistance of the water film formed by jet impingement on the hot surface. 4. The method as claimed in claim 1 or 2, wherein the surfactant additive is DuPont™ Zonyl® FSH. 15 5. The method as claimed in any of the preceding claims, wherein the impinging jet removes the heat without phase change. 6. The method as claimed in claim 5 or 6, wherein the impinging jet removes the heat by conduction through water film and evaporation at the liquid- vapour interface. 7. The method as claimed in claim 1, wherein the impinging jet nozzle module comprises of more than one nozzle configuration having Tee, elbow connection, and tube/pipe connection so as to provide accurate adjustment of equal flow rate for each nozzle. 8. A method to improve hydrodynamics and heat transfer of hydraulic jump region in the process of jet impingement cooling as substantially described herein with respect to the accompanying drawings. A method to improve hydrodynamics and heat transfer of hydraulic jump region in the process of jet impingement cooling, comprising the steps of: dissolving a surfactant additive, which is DuPont™ Zonyl® FSH in a cooling medium and forming an aqueous surfactant solution; providing an impinging jet nozzle module capable of generating an accurately equal flow rate for each nozzle; measuring temperature of the surface to be cooled by attaching thermocouple; creating a fully-developed flow via the nozzle module by using a pump such that the aqueous surfactant solution is impinged on the coolable surface at a flow- rate covering from laminar to turbulent.

Documents:

00498-kol-2007-abstract.pdf

00498-kol-2007-claims.pdf

00498-kol-2007-correspondence others 1.1.pdf

00498-kol-2007-correspondence others 1.2.pdf

00498-kol-2007-correspondence others.pdf

00498-kol-2007-description complete.pdf

00498-kol-2007-drawings 1.1.pdf

00498-kol-2007-drawings.pdf

00498-kol-2007-form 1.pdf

00498-kol-2007-form 18.pdf

00498-kol-2007-form 2.pdf

00498-kol-2007-form 3.pdf

00498-kol-2007-gpa.pdf

498-KOL-2007-(03-08-2012)-ABSTRACT.pdf

498-KOL-2007-(03-08-2012)-AMANDED CLAIMS.pdf

498-KOL-2007-(03-08-2012)-DESCRIPTION (COMPLETE).pdf

498-KOL-2007-(03-08-2012)-DRAWINGS.pdf

498-KOL-2007-(03-08-2012)-EXAMINATION REPORT REPLY RECEIVED.pdf

498-KOL-2007-(03-08-2012)-FORM-1.pdf

498-KOL-2007-(03-08-2012)-FORM-2.pdf

498-KOL-2007-(03-08-2012)-OTHERS.pdf

498-KOL-2007-CORRESPONDENCE.pdf

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