Quenching a steel plate by water-impinging jets and different simultaneous flow rates

Regarding the great importance of fast cooling in steel industry for the production processes, a deep understanding of heat transfer and fluid dynamics must be held. A steel plate is heated up until a maximum temperature of 700 ⁰C to be then cooled down seconds later by a configuration of multiple impinging water jets. Different flow rates are used simultaneously by different adjacent jets to perform quenching over the sample, so different hardness is obtained in the material over a small area. Temperature drop in time is measured and monitored by embedded thermocouples and LabVIEW program. To achieve greater understanding of the quenching performance with different flow rates, several parameters are selected to be varied in order to achieve the best working conditions. Jet diameter takes values between 4 and 10 mm, initial temperature of quenching varies from 400 to 700 ⁰C, subcooling temperature is tested for 65 and 75 K, and jet velocity varies between 1.9 and 3.9 m/s. The result of total number of 9 experiments shown that variation of jet diameter does not influence substantially on the cooling rate if flow rate is kept constant. High initial quenching temperature (600-700 ⁰C) led to slightly higher cooling rate in the stagnation region of water jets. The peak value of heat transfer rate in the upwash flow zone was more highlighted for initial quenching temperature 600⁰C and below it. Higher values of subcooling and jet velocity produce better cooling rates. The result shown higher jet velocity at one column of water jets changes position of upwash flow slightly toward the adjacent column of jets with lower jet velocity. In general, the result shown that all the studied parameters did not have negative effect on obtaining various cooling rates over the steel plate.<br /

Computational study of multiple impinging jets on heat transfer

This numerical study presents investigation of impinging jets cooling effect on a hot flat plate. Different configuration of single jet, 5-cross and 9-square setups have been studied computationally in order to understand about their behaviour and differences behind their physics. Moreover, a specific confined wall was designed to increase two crucial parameters of the cooling effect of impinging jets; average heat transfer coefficient of impingement wall and average air temperature difference of outlet the domain and jet inlet. The 2-D simulation has been performed to design the confined wall to optimise the domain geometry  to achieve project goals contains highest average heat transfer coefficient of hot plate in parallel to highest average air temperature difference of outlet. Different effective parameters were chosen after 2-D simulation study and literature review; Jet to wall distance H/D = 5, Radial distance from centre of plate R/D = 20, jet diameter D = 10 mm. The 3-D computational study was performed on single jet, 5-cross and 9-square configurations to investigate the differences of results and find best setup for the specific boundary condition in this project. Single jet geometry reveals high temperature level in the outlet, but very low average heat transfer coefficient due to performance of a single jet in a domain (Re= 17,232). In the other side, 5-cross setup has been studied for Reynolds number of 9,828, 11,466, 17,232 and 20,000 and it was found that range of 11,466 to 17,232 performs very well to achieve the purposes in this study. Moreover, turbulence models of ,  and  have been used to verify the models (Re=17,232) with available experimental data for fully developed profile of the jets inlets and wall jet velocity and Reynolds stress components near the wall boundary condition. All three turbulence models predict well   the velocity components for jets fully developed profile and for wall boundary condition of the target plate. But since  model has been validated with the Reynolds stress components by experimental data, therefore is more reliable to continue the study with verified simulation. Finally 9-square configuration was investigated (Re=17,232) and the result compared with other setups. It was concluded that 5-cross multiple jets is best design for this project while 9-square multiple impinging jets also fulfils the project purpose, but for extended application in industry each setup is suitable for specific conditions. 5-cross multiple jets is good choice for large cooling area which can be used in number of packages to cover the area, while 9-square jets setup performs well where very high local heat transfer is needed in a limited area

Quenching Hot Rotary Hollow Cylinder by 1-row and 2-row Water Impinging Jet Array

Experimental study has been carried out to investigate transient quenching of rotary hollow cylinder by subcooled water impinging jets (∆Tsub= 55-85K) in 1-row and 2-row inline array. The flow rate of water jets varied from 2.7 to 10.9 L/min, impinging on hot rotary cylinder (Ti =600℃) with rotation speed 10-50 rpm and different curvature ratio (Do/d = 12, 19 and 24). The local average and maximum boiling heat transfer at water jet’s stagnation point revealed effect of studied quenching parameters and multiple jet arrays in the boiling heat transfer. The result showed among the studied parameters, jet’s flow rate and curvature ratio influenced heat transfer in all the boiling regimes. Rotation speed was effective in film and transition boiling regime and strong effect of subcooling was captured in the transition boiling regime. The characteristics of maximum heat flux point in the boiling curve were found to be dependent on the studied quenching parameters as well as array of nozzles. Multiple jet arrays had effect on the spatial variation and rate of boiling heat transfer on quenching surface. The heat transfer enhancement by larger number of rows, i.e. 2-row array, was studied based on two approaches of constant single jet’s flow rate and array’s total flow rate. The result shown better heat transfer performance is achieved by increasing number of row in the array while the total flow rate is constant. It was found that by impinging constant water flow rate into the jets, 2-row array with twice the number of impinging jets enhanced heat transfer significantly in film and transition boiling regime in combination with other quenching parameters

Experimental study of quenching process on a rotating hollow cylinder by one row of impinging jets

Quenching cooling rate of rotary hollow cylinder by one row of water impinging jets has been experimentallystudied. Water jets (d = 8 mm) with sub-cooling 55 to 85°C and Reynolds number 8,006 to 36,738 impinged over rotaryhot hollow cylinder (rotation speed 10 to 70 rpm) with initial temperature 250 to 600°C. Impingement impact angle of row of jets varied between 0 to 135° and jet-to-jet spacing in row patten was 2 to 8d. The results revealed more uniformityon cooling rate of quenching in smaller jet-to-jet spacing (2 and 4d) where wetting front regions are located closer toneighbor jet’s region. By increasing spacing, footprint of annular transition region was highlighted in quenching coolingrate contour. A distinct quenching characteristic was obtained for impingement impact angle of 0° compare to otherangles. With initial temperature above the Leidenfrost temperature, low cooling rate was achieved in film and transitionboiling compare to a steep increase of cooling rate at start of quenching with higher maximum heat transfer for experimentswith initial temperatures less than Leidenfrost temperature. The effect of other parameters on quenching coolingrate was highlighted in film and transition boiling while no significant differences were observed in nucleate boiling.Digital conference proceedings distributed to participants.</p

Effect of Multiple Water Impinging Jet Array on Quenching Hot Rotary Hollow Cylinders

Experimental study has been carried out to investigate transient quenching of a rotary hollow cylinder by water impinging jets in multiple jet arrays. Subcooled water jets (Δ= 55-85K) were placed into two types of nozzle arrays: 1-row and 2-row in-line array. The flow rate of water jets varied from 2.7 to 10.9 L/min, impinging on hot rotary cylinder ( =600℃) with rotation speed 10-50 rpm and different curvature ratio (/d = 12, 19 and 24). The local average and maximum boiling heat transfer at water jet’s stagnation point revealed effect of studied quenching parameters and multiple jet arrays in the boiling heat transfer. The result showed among the studied parameters, jet’s flow rate and curvature ratio influenced heat transfer in all the boiling regimes. Rotation speed was effective in film and transition boiling regime and strong effect of subcooling was captured in the transition boiling regime. The characteristics of maximum heat flux point in the boiling curve were found to be dependent on the studied quenching parameters as well as array of nozzles. Multiple jet arrays had effect on the spatial variation and rate of boiling heat transfer on quenching surface. Higher area-averaged and maximum surface heat flux was obtained by 2-row array while array’s total flow rate was kept constant. It was found that by impinging constant water flow rate into the jets, 2-row array with twice the number of impinging jets enhanced heat transfer significantly in film and transition boiling regime in combination with other quenching parameters

Tourism Market Segmentation of Kish Free Zone: A New Approach to Brand Concept Map

The success of tourism destinations depends on a proper understanding of the brand image of individuals, but individuals have different mental images which are potentially the basis for segmentation in the tourism market. The present study is primarily an attempt to develop a brand concept map method that is done by refining it with an inventive algorithm, so the research is developmental in terms of purpose. Secondly, to apply the refined Brand Concept Map method in practice this method is used for the tourism brand of Kish Free Zone. The statistical population of the study is people in Tehran city in two groups of people who have visited and those who haven’t visited the Kish Free Zone. The available sampling method is used. The four-step of extraction, segmentation, mapping, and interpretation of mental maps will ultimately lead to the identification of seven segments for the Kish Free Zone Tourism Market. According to the results, there are four categories of luxury tourists, price-sensitive tourists, non-loyal tourists, and Eco-tourists among people who have visited Kish and there are three categories of shoppers, entertainers, and immigrant among people who haven’t visited Kis

Mapping Associations Networks of Kish Free Zone’s Tourist Branding Using Brand Conceptual Mapping Method

Competition and the speed of change in the tourism industry have made organizations to understand audience feedback to plan for attracting more tourists. This research is an applied research, with a combination of elements. It attempts to use the brand conceptual mapping method to create insight from the understanding of internal audience to the tourism brand of Kish Free Zone. For data collection, 200 people in Tehran in two groups of people with/without a history of visiting the Kish Free Zone were selected by simple sampling. After two interviews using Brand Conceptual Mapping Method, their mental maps were drawn up. Although the Kish Free Zone includes the Kish Island, Hendurabi, and greater and little Faror Island, except Kish, there was no association related to the other islands in the maps. According to the results, people with a history of visits had more associations and more positive associations. More than half of the associations of people without a history of visits were similar to those with a history of visits. The inclusion of an advertising media as a negative association on the map of people without a history of visits was a notable poin

Effect of spatial-temporal behavior of a newly developed cooling system on carbon and stainless steel bar properties

This report summaries the work within the project ”Effect of spatial-temporal behavior of a newly developed cooling system on carbon and stainless-steel bar properties”. The project was conducted from 2020-01-01 to 2022-12-31 and was co-produced by SSAB, Outokumpu and University of Gävle (UoG). The Knowledge Foundation, SSAB, Outokumpu and UoG financed the project. For the Swedish steel companies SSAB and Outokumpu producing special steels, it is very important to be able to control the cooling process in order to produce steel bars with excellent properties. Both steel companies also want to be able to control the cooling process so that the excellent steel properties become even over the bars’ spatial configuration. The aim of the present project is to reveal the spatial-temporal behavior of a newly developed cooling technology in order to produce steel bars with excellent properties and to control the phase transformation to achieve optimal performance of the steel bars. By using the special test rig at the UoG, detail temperature measurement mapping, invers solution and direct numerical simulation, the present project has identified and quantified several important aspects related to the quenching process, operating conditions, and temperature field development within the investigated products. The result from the proposed cooling process provides an outstanding cooling rate that is very crucial to obtain the required steel phase and thus the correct properties of the bar with different sizes. Results from this study have also shown that the cost per kg product can be reduced by tunning the process parameters such as soaking time and bar temperature before starting the cooling process. In addition, both experimental and numerical results of the material investigation show that the cooling technology has resulted in the desired phase transformation and subsequently the desired steel phases and material properties. The results show that the cooling technology and the control of the cooling parameters can be used to optimize the material properties of the bar materials. These good results and conclusions have been obtained via the deep collaboration between the SSAB, Outokumpu and UoG. The co-production, starting in the steering group planning the work along with the combination of research conducted at UoG and at the companies, have led to a successful project with great knowledge transfer in all direction during the duration of the project.Funding: The Knowledge Foundation, SSAB, Outokumpu and University of GävleEffect of spatial-temporal behavior of a newly developed cooling system on carbon and stainless steel bar propertie

Quenching of Carbon Steel Plates with Water Impinging Jets : Differential Properties and Fractography

The demand for steel components with tailored properties is constantly growing. To obtain a specific variation of microstructures and mechanical properties along the component it must undergo a controllable cooling. One way to control the cooling rates along the component is by using different simultaneous water jet impingements on a hot austenitized surface. This can be done by a newly developed test rig for water Impinging Jet Quenching Technique (IJQT). This work discusses the effect of IJQT on mechanical properties and fracture behavior of 15 mm steel plates containing 0.27 and 0.38 mass-% carbon. The samples were cooled in a specifically designed setup of the technique to obtain simultaneous water and air cooling resulting in diverse microstructures. The mechanical property gradients of both steels were analyzed through hardness measurements and tensile tests. The fracture surfaces and the near fracture regions were observed using scanning electron microscope and light optical microscope respectively. The results from tensile tests showed that the larger part of the sample with higher carbon content was fully hardened, however smoothly transitioning to a more ductile region. The sample with lower carbon content combined various degrees of hardening and transitioned from higher to lower ultimate tensile strength values. Fracture behavior of higher carbon steel was predominantly brittle transitioning to a ductile, while the lower carbon steel had a small region showing brittle fracture transitioning to a larger region of predominant ductile fracture behavior

The frequency of Klebsiella pneumonia encoding genes for CTX-M, TEM-1 and SHV-1 extended-spectrum beta lactamases enzymes isolated from urinary tract infection

Abstract Background The extended- spectrum β-lactamase producing bacteria are widely spread worldwide. The productions of these enzymes cause bacterial resistance to a wide range of antibiotics. The aim of this study was to investigated the frequency of K. pneumonia encoding genes for CTX-M, TEM-1 and SHV-1 extended-spectrum beta lactamases enzymes isolated from urinary tract infection. Methods This study is cross-sectional study. All K. pneumonia isolates from urine samples, which had grown on media culture more than 105 were delivered to the medical microbiology laboratory. K. pneumonia susceptibility of 198 samples were confirmed by disk diffusion. The gene frequency of genes was determined using PCR, and analyzed using SPSS version 21 software. Finding Most of the K. pneumonia isolated from urine producing β-lactamase were resistant to cotrimoxazole (53.2%) followed by cefotaxime (50%), ceftazidime, ceftriaxone (40.3%), nalidixic acid (17.8%), amikacin and imipenem (1.6%) and meropenem (0%) respectively. Out of the 198 confirmed isolates of K. pneumonia, 62 cases (31.3%) have the gene phenotype of broad spectrum β-lactamase enzymes and highest frequency of gene phenotype was related to the SHV-1 gene (85.5%). Then in the terms of abundance from highest to lowest CTXM-3 (56.5%), CTXM-1 (27.4%), TEM-1 (16.1%) and CTXM-2 (8.1%), were respectively. Conclusion This study showed that K. pneumonia isolated from urine producing β-lactamase were resistance to a wide range of antibiotics. Due to the increasing resistance of most antibiotics, control and supervision in the use of antibiotics and identification of broad spectrum β-lactamase enzymes by phenotypic methods appears to be essential