Chitranjan Agrawal | Maharan Pratap Unversity of Agriculture and Technolgy,Udaipur,India (original) (raw)

Uploads

Papers by Chitranjan Agrawal

Hot S tainless Steel (S S-304) horizontal surface of different initial temperatures are cooled by... more Hot S tainless Steel (S S-304) horizontal surface of different initial temperatures are cooled by water jet of 33 ºC temperature and 3 mm diameter. The surface cooling performance is investigated with flow rate of 1.2 and 5.10 lpm. The test surface is of 150 mm long, 150 mm wide and 2 mm thickness. S urface is initially heated up to certain temperature in furnace and cooled by downward impinging jet. The process of surface cooling is recorded by a camera and the wetting speed over the hot surface is determined. The wetting speed on the hot surface is observed in the range of 2-35 mm/s for 10 mm-40 mm spatial locations. It has been observed that the wetting speed increases with rise in flow rate and reduces for higher downstream spatial locations and surface initial temperature. Index Terms-Jet Impingement, Wetting speed, S tagnation point, S urface quenching.

An experimental investigation has been carried out to study the cooling of a hot horizontal Stain... more An experimental investigation has been carried out to study the cooling of a hot horizontal Stainless Steel surface of 3 mm thickness, which has 800±10 °C initial temperature. A round water jet of 22 ± 1 °C temperature was injected over the hot surface through straight tube type nozzles of 2.5-4.8 mm diameter and 250 mm length. The experiments were performed for the jet exit to target surface spacing of 4 times of jet diameter and jet Reynolds number of 5000-24000. The effect of change in jet Reynolds number on the surface quenching has been investigated form the stagnation point to 16 mm spatial location.

Lecture Notes in Mechanical Engineering, 2022

International Journal of Scientific Research in Science and Technology, 2017

Flow dynamics of round and slot air jet impinging on convex surface is reviewed by considering fr... more Flow dynamics of round and slot air jet impinging on convex surface is reviewed by considering free jet flow visualization images. Phenomena of air entrainment, large vortex structure generation, vortex merging, pairing, break up in the flow are responsible for different heat transfer behavior from the hot surface. In this paper an attempt is made to review flow dynamics and flow behavior by round air jet over convex heated surface along with discussion for jet structure under free condition.

Study of surface quenching is of interest particular in the context of emergency core cooling of ... more Study of surface quenching is of interest particular in the context of emergency core cooling of a nuclear reactor under LOCA conditions. Rewetting is a phenomenon which occurs during the quenching of hot surfaces of high temperature. Rewetting of surface occurs at minimum film boiling point where liquid established direct contact with a hot dry surface. The present investigation deals with experimental investigations on the quenching behavior of a hot horizontal stainless steel surface of 0.25 mm thickness with water jet of 22oC temperature. Initially, test surface is heated up to 800oC and water jet is injected through a straight tubes nozzle of 2.5 mm diameter. The observations are made up to 16 mm downstream locations away from the stagnation point. The nozzle exit to surface spacing is kept in the range of 4-16 times of nozzle diameter and Reynolds number in the range of 5000-24000. Rewetting temperature, rewetting velocity and wetting delay are some of the parameters over whic...

International Journal of Heat and Mass Transfer, 2013

An experimental investigation has been carried out to study the rewetting behaviour of a hot hori... more An experimental investigation has been carried out to study the rewetting behaviour of a hot horizontal stainless steel surface during the mist jet impingement cooling. The experiments have been performed to study the rewetting behaviour for three different initial surface temperatures viz. 255, 355, 565°C. An axis-symmetric nozzle has been used to develop the mist jet of constant flow rate. The variation in surface temperature has been acquired up to 20 mm downstream spatial locations away from the stagnation point. It has been observed that unlike liquid jet impingement cooling the rise in surface initial temperature increases the rewetting temperature and the wetting delay increase with rise in the initial surface temperature but the rewetting velocity reduces. Further, the maximum surface heat flux is the highest at 20 mm spatial location for 565°C initial surface temperature. Whereas, at the stagnation point, the maximum surface heat flux is not affected by the change in surface initial temperature.

International Journal of Heat and Mass Transfer, 2012

The transient cooling of hot stainless steel surface of 0.25 mm thickness is done with round wate... more The transient cooling of hot stainless steel surface of 0.25 mm thickness is done with round water jet impingement. Initially, the surface was heated up to the temperature of 800°C before the water was injected through straight tube type nozzle of 2.5 mm diameter and 250 mm length. During impingement cooling, the surface temperature was measured up to 12 mm radial distance away from the stagnation point. The jet exit to surface spacing, z/d, and jet Reynolds number, Re, varied in the range of 4-16 and 5000-24,000 respectively. The surface rewetting and transient heat flux of the test-surface was studied for these operating parameters. During impingement cooling process the initial rewetting occurred at stagnation region with the lowest wetting delay period. In fact, the rewetting temperature, rewetting velocity and the maximum heat flux reduced for extreme spatial location. However, the wetting delay increased significantly for the locations away from the stagnation point. The surface rewetting and transient heat flux were increased with the rise in jet Reynolds number, resulting in the enhancement in rewetting temperature, rewetting velocity and reduced wetting delay. The maximum heat flux was obtained for 4-6 mm radial location. The effect of jet exit to surface spacing on the rewetting parameters is found to be marginal. A correlation has been developed which predicted the maximum heat flux within an error band of ±10%.

The jet impingement cooling technique is used for rapid surface quenching that takes place after ... more The jet impingement cooling technique is used for rapid surface quenching that takes place after a certain surface temperature called as the rewetting temperature. In this manuscript a theoretical model to determine the surface rewetting temperature is proposed. The rewetting temperature obtained with this model is compared with the experimental results for hot horizontal flat surface quenching. The proposed model accurately predicts the surface rewetting temperature for the stagnation point. However, for the spatial location up to 12 mm. the rewetting temperature falls within the error band of ± 15 percent. This variation for the downstream locations is due to retardation of jet flow over hot surface. Since, jet velocity has been considered as one of the depending variables in determining the heat transfer, however, its retarding effect for the downstream location has not been incorporated in the model.

Experimental Thermal and Fluid Science, 2012

ABSTRACT A horizontal stainless steel surface of 0.25 mm thickness and at 800 ± 10 °C initial tem... more ABSTRACT A horizontal stainless steel surface of 0.25 mm thickness and at 800 ± 10 °C initial temperature was cooled by a round water jet. The water jet at 22 ± 1 °C temperature impinged onto the hot surface through tube type nozzles of 250 mm length. The experiments were performed for the jet diameters in the range of 2.5–4.8 mm and the jet Reynolds number remained within 5000–24,000.The transient cooling performance of the test surface was determined on the basis of rewetting temperature, wetting delay and the rewetting velocity. A rise in the rewetting temperature and the rewetting velocity has been observed with the increase in jet diameter and jet Reynolds number, leading to decline in the wetting delay.The results of the steady state cooling are in agreement with the findings of other investigators. The correlations have also been developed to evaluate the stagnation and the local Nusselt number for the steady state cooling condition. These correlations predict 80% experimental data within an error band of ±10%.

Lecture Notes in Mechanical Engineering

steel research international

Heat Transfer Engineering, 2016

Heat and Mass Transfer, 2016

Journal of Enhanced Heat Transfer, 2015

Journal of Thermal Analysis and Calorimetry, 2015

Heat and Mass Transfer, 2015