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S S Mohapatra - One of the best experts on this subject based on the ideXlab platform.
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enhancement of heat removal rate of high mass flux spray cooling by sea water
Experimental Thermal and Fluid Science, 2017Co-Authors: A R Pati, Basudeb Munshi, A P Behera, S S MohapatraAbstract:Abstract The main obligation in achieving high cooling rates in case of spray cooling at high surface temperature is the occurrence of film Boiling Phenomenon. Although the high mass flux spray reduces the film Boiling affect, still, the heat transfer rate is not significant and hence, this process needs to be enhanced. In the absence of any information on the heat transfer augmentation technique, the present work deals with the enhancement of high mass flux spray cooling at very high initial plate temperature by using sea water. The sea water spray cooling process increases the heat removal rate by creating high heat transfer area for the droplet evaporation and by reducing the vapour pressure of vapour film on the hot plate. The cooling ability of the sea water spray is compared with the coolants (salt added water, surfactant added water and surfactant and salt added water) which partially depict the properties of sea water. For the experimental investigation, spray cooling was conducted at 900 °C initial surface temperature on a 6 mm thick AISI 304 steel plate (100 × 100 mm) by using sea water and also aforesaid coolants at different concentrations. The surface heat flux and surface temperature have been predicted using the solution of the Inverse Heat Conduction Problem (IHCP). For the understanding of heat transfer mechanism, the properties of coolants (contact angle, thermal conductivity, density, specific heat and mass diffusivity) at different concentrations and spray behaviour (droplet diameter, spray pressure, droplet velocity and spray impingement density) at different flow rates were measured. The physical properties of the coolant reveal that the contact angle decreases with the increasing salt concentration up to 0.1 M and further increment in salt concentration enhances the contact angle. From the thermal properties of the coolant, it is observed that thermal diffusivity in sea water is higher than salt added water. The sea water spray cooling asserts that the heat removal rate increases with the increasing percentage of sea water in the mixture of seawater and pure water due to the salt deposition on the hot surface. However, the achieved heat removal rate is lower than that of salt added water due to the comparatively less amount of salt deposition in case of sea water spray. Furthermore, the combined effect of the salt deposition and lowering of vapour pressure in vapour film phenomena produce better heat removal rate than the pure water and surfactant and salt added water. In comparison between sea water and surfactant added water spray cooling, the former produces higher heat removal rate because of the dominance of salt deposition Phenomenon over the lowering of contact angle property. In case of sea water spray, the achieved critical heat flux (1.55 MW/m 2 ) is 1.3 times that of pure water (1.2 MW/m 2 ); moreover, the enhanced critical heat flux is obtained at 170 °C higher surface temperatures. In addition to the above, the enhancement by NaCl added water spray is almost 1.6 times that of pure water. Due to the above mentioned favourable conditions for the fast cooling, the maximum cooling rates of 115 °C/s and 135 °C/s are achieved with sea water and NaCl added water sprays, respectively.
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high mass flux spray cooling with additives of low specific heat and surface tension a novel process to enhance the heat removal rate
Applied Thermal Engineering, 2017Co-Authors: N H Bhatt, A R Pati, Aditya Kumar, Ajit Behera, Basudeb Munshi, S S MohapatraAbstract:Abstract High mass flux spray cooling is a good replacement of conventional cooling methods such as jet cooling and laminar cooling in metallurgical industries. However, the cooling rates obtained in spray cooling are still not sufficient for the production of high tensile strength and moderate hardenability steel. The challenging task in the conventional spray cooling is the elimination of film Boiling Phenomenon. The solution to such difficulties is the use of high mass flux spray which generates high momentum droplets that penetrates the vapour film and almost excludes the film Boiling affect. Along with the aforesaid advantage, the high mass flux spray also creates low residence time that leads to incomplete evaporation and as a consequence, the obtained heat transfer rate is not significant. Hence, the heat removal rate needs to be further enhanced. This can be achieved by increasing the heat transfer area and lowering the sensible heating time. So, in the current work, coolants of low specific heat and surface tension are prepared by separately mixing water with benzene, acetone and n -hexane in different combinations to see the effects of specific heat and surface tension on heat transfer rate. The substrate used was a square AISI 304 steel plate (100 × 100 × 6 mm). The surface temperatures and heat fluxes were calculated by using INTEMP software. Before experimentation, the mass flux and nozzle to plate distance were optimised. The result shows significant augmentation of heat removal rate with an increment in critical heat flux of 40, 30 and 20% with acetone, n -hexane and benzene, respectively. Moreover, mathematical correlations are developed using Design Expert software to determine the heat transfer coefficient at different properties of coolants.
A R Pati - One of the best experts on this subject based on the ideXlab platform.
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enhancement of heat removal rate of high mass flux spray cooling by sea water
Experimental Thermal and Fluid Science, 2017Co-Authors: A R Pati, Basudeb Munshi, A P Behera, S S MohapatraAbstract:Abstract The main obligation in achieving high cooling rates in case of spray cooling at high surface temperature is the occurrence of film Boiling Phenomenon. Although the high mass flux spray reduces the film Boiling affect, still, the heat transfer rate is not significant and hence, this process needs to be enhanced. In the absence of any information on the heat transfer augmentation technique, the present work deals with the enhancement of high mass flux spray cooling at very high initial plate temperature by using sea water. The sea water spray cooling process increases the heat removal rate by creating high heat transfer area for the droplet evaporation and by reducing the vapour pressure of vapour film on the hot plate. The cooling ability of the sea water spray is compared with the coolants (salt added water, surfactant added water and surfactant and salt added water) which partially depict the properties of sea water. For the experimental investigation, spray cooling was conducted at 900 °C initial surface temperature on a 6 mm thick AISI 304 steel plate (100 × 100 mm) by using sea water and also aforesaid coolants at different concentrations. The surface heat flux and surface temperature have been predicted using the solution of the Inverse Heat Conduction Problem (IHCP). For the understanding of heat transfer mechanism, the properties of coolants (contact angle, thermal conductivity, density, specific heat and mass diffusivity) at different concentrations and spray behaviour (droplet diameter, spray pressure, droplet velocity and spray impingement density) at different flow rates were measured. The physical properties of the coolant reveal that the contact angle decreases with the increasing salt concentration up to 0.1 M and further increment in salt concentration enhances the contact angle. From the thermal properties of the coolant, it is observed that thermal diffusivity in sea water is higher than salt added water. The sea water spray cooling asserts that the heat removal rate increases with the increasing percentage of sea water in the mixture of seawater and pure water due to the salt deposition on the hot surface. However, the achieved heat removal rate is lower than that of salt added water due to the comparatively less amount of salt deposition in case of sea water spray. Furthermore, the combined effect of the salt deposition and lowering of vapour pressure in vapour film phenomena produce better heat removal rate than the pure water and surfactant and salt added water. In comparison between sea water and surfactant added water spray cooling, the former produces higher heat removal rate because of the dominance of salt deposition Phenomenon over the lowering of contact angle property. In case of sea water spray, the achieved critical heat flux (1.55 MW/m 2 ) is 1.3 times that of pure water (1.2 MW/m 2 ); moreover, the enhanced critical heat flux is obtained at 170 °C higher surface temperatures. In addition to the above, the enhancement by NaCl added water spray is almost 1.6 times that of pure water. Due to the above mentioned favourable conditions for the fast cooling, the maximum cooling rates of 115 °C/s and 135 °C/s are achieved with sea water and NaCl added water sprays, respectively.
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high mass flux spray cooling with additives of low specific heat and surface tension a novel process to enhance the heat removal rate
Applied Thermal Engineering, 2017Co-Authors: N H Bhatt, A R Pati, Aditya Kumar, Ajit Behera, Basudeb Munshi, S S MohapatraAbstract:Abstract High mass flux spray cooling is a good replacement of conventional cooling methods such as jet cooling and laminar cooling in metallurgical industries. However, the cooling rates obtained in spray cooling are still not sufficient for the production of high tensile strength and moderate hardenability steel. The challenging task in the conventional spray cooling is the elimination of film Boiling Phenomenon. The solution to such difficulties is the use of high mass flux spray which generates high momentum droplets that penetrates the vapour film and almost excludes the film Boiling affect. Along with the aforesaid advantage, the high mass flux spray also creates low residence time that leads to incomplete evaporation and as a consequence, the obtained heat transfer rate is not significant. Hence, the heat removal rate needs to be further enhanced. This can be achieved by increasing the heat transfer area and lowering the sensible heating time. So, in the current work, coolants of low specific heat and surface tension are prepared by separately mixing water with benzene, acetone and n -hexane in different combinations to see the effects of specific heat and surface tension on heat transfer rate. The substrate used was a square AISI 304 steel plate (100 × 100 × 6 mm). The surface temperatures and heat fluxes were calculated by using INTEMP software. Before experimentation, the mass flux and nozzle to plate distance were optimised. The result shows significant augmentation of heat removal rate with an increment in critical heat flux of 40, 30 and 20% with acetone, n -hexane and benzene, respectively. Moreover, mathematical correlations are developed using Design Expert software to determine the heat transfer coefficient at different properties of coolants.
Basudeb Munshi - One of the best experts on this subject based on the ideXlab platform.
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enhancement of heat removal rate of high mass flux spray cooling by sea water
Experimental Thermal and Fluid Science, 2017Co-Authors: A R Pati, Basudeb Munshi, A P Behera, S S MohapatraAbstract:Abstract The main obligation in achieving high cooling rates in case of spray cooling at high surface temperature is the occurrence of film Boiling Phenomenon. Although the high mass flux spray reduces the film Boiling affect, still, the heat transfer rate is not significant and hence, this process needs to be enhanced. In the absence of any information on the heat transfer augmentation technique, the present work deals with the enhancement of high mass flux spray cooling at very high initial plate temperature by using sea water. The sea water spray cooling process increases the heat removal rate by creating high heat transfer area for the droplet evaporation and by reducing the vapour pressure of vapour film on the hot plate. The cooling ability of the sea water spray is compared with the coolants (salt added water, surfactant added water and surfactant and salt added water) which partially depict the properties of sea water. For the experimental investigation, spray cooling was conducted at 900 °C initial surface temperature on a 6 mm thick AISI 304 steel plate (100 × 100 mm) by using sea water and also aforesaid coolants at different concentrations. The surface heat flux and surface temperature have been predicted using the solution of the Inverse Heat Conduction Problem (IHCP). For the understanding of heat transfer mechanism, the properties of coolants (contact angle, thermal conductivity, density, specific heat and mass diffusivity) at different concentrations and spray behaviour (droplet diameter, spray pressure, droplet velocity and spray impingement density) at different flow rates were measured. The physical properties of the coolant reveal that the contact angle decreases with the increasing salt concentration up to 0.1 M and further increment in salt concentration enhances the contact angle. From the thermal properties of the coolant, it is observed that thermal diffusivity in sea water is higher than salt added water. The sea water spray cooling asserts that the heat removal rate increases with the increasing percentage of sea water in the mixture of seawater and pure water due to the salt deposition on the hot surface. However, the achieved heat removal rate is lower than that of salt added water due to the comparatively less amount of salt deposition in case of sea water spray. Furthermore, the combined effect of the salt deposition and lowering of vapour pressure in vapour film phenomena produce better heat removal rate than the pure water and surfactant and salt added water. In comparison between sea water and surfactant added water spray cooling, the former produces higher heat removal rate because of the dominance of salt deposition Phenomenon over the lowering of contact angle property. In case of sea water spray, the achieved critical heat flux (1.55 MW/m 2 ) is 1.3 times that of pure water (1.2 MW/m 2 ); moreover, the enhanced critical heat flux is obtained at 170 °C higher surface temperatures. In addition to the above, the enhancement by NaCl added water spray is almost 1.6 times that of pure water. Due to the above mentioned favourable conditions for the fast cooling, the maximum cooling rates of 115 °C/s and 135 °C/s are achieved with sea water and NaCl added water sprays, respectively.
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high mass flux spray cooling with additives of low specific heat and surface tension a novel process to enhance the heat removal rate
Applied Thermal Engineering, 2017Co-Authors: N H Bhatt, A R Pati, Aditya Kumar, Ajit Behera, Basudeb Munshi, S S MohapatraAbstract:Abstract High mass flux spray cooling is a good replacement of conventional cooling methods such as jet cooling and laminar cooling in metallurgical industries. However, the cooling rates obtained in spray cooling are still not sufficient for the production of high tensile strength and moderate hardenability steel. The challenging task in the conventional spray cooling is the elimination of film Boiling Phenomenon. The solution to such difficulties is the use of high mass flux spray which generates high momentum droplets that penetrates the vapour film and almost excludes the film Boiling affect. Along with the aforesaid advantage, the high mass flux spray also creates low residence time that leads to incomplete evaporation and as a consequence, the obtained heat transfer rate is not significant. Hence, the heat removal rate needs to be further enhanced. This can be achieved by increasing the heat transfer area and lowering the sensible heating time. So, in the current work, coolants of low specific heat and surface tension are prepared by separately mixing water with benzene, acetone and n -hexane in different combinations to see the effects of specific heat and surface tension on heat transfer rate. The substrate used was a square AISI 304 steel plate (100 × 100 × 6 mm). The surface temperatures and heat fluxes were calculated by using INTEMP software. Before experimentation, the mass flux and nozzle to plate distance were optimised. The result shows significant augmentation of heat removal rate with an increment in critical heat flux of 40, 30 and 20% with acetone, n -hexane and benzene, respectively. Moreover, mathematical correlations are developed using Design Expert software to determine the heat transfer coefficient at different properties of coolants.
A Mukhopadhyay - One of the best experts on this subject based on the ideXlab platform.
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numerical determination of heat transfer coefficient for Boiling Phenomenon at runout table of hot strip mill
Ironmaking & Steelmaking, 2004Co-Authors: S Sikdar, A MukhopadhyayAbstract:The heat transfer coefficient during film Boiling at the runout table of the hot strip mill is usually determined by experimental methods. Described in the present paper is a finite difference based model for analysis of the thermal behaviour of the strip during cooling at the runout table of the hot strip mill at Tata Steel, India. The model, developed for the prediction of strip temperature, is used to determine the heat transfer coefficient at the water/strip interface while water cooling occurs. A simple form of polynomial as a function of the strip surface temperature is proposed to describe the heat transfer coefficient at the water/strip interface. Good correlation has been found between model predicted temperatures considering the polynomial type heat transfer coefficient and the actual coiling temperature.
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numerical simulation to determine the heat transfer coefficient in the Boiling Phenomenon of run out table of a hot strip mill
ASME JSME 2003 4th Joint Fluids Summer Engineering Conference, 2003Co-Authors: S Sikdar, A MukhopadhyayAbstract:A Mathematical model has been developed to predict the temperature profile of the strip in the Run-out Table (ROT) of the Hot Strip Mill (HSM) at Tata Steel, India. The prediction of temperature profile across the thickness of the strip shows good results. A simple correlation for heat transfer coefficient has emerged from this study. A polynomial as a function of strip surface temperature has been found to represent the heat transfer coefficient at water-strip interface accurately. The salient features of this paper are described as follows: 1) An off-line model has been developed to predict the through thickness temperature of the strip in the Run-out Table of a Hot Strip Mill. 2) The heat transfer coefficient at water-strip interface on the water-cooled zone over the bed of Run-out Table can be considered as a polynomial of strip surface temperature. Tests have been performed to validate the correlation of heat transfer coefficient against several thousand coils.© 2003 ASME
H R Chamani - One of the best experts on this subject based on the ideXlab platform.
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numerical investigation of heat transfers in the water jacket of heavy duty diesel engine by considering Boiling Phenomenon
Case Studies in Thermal Engineering, 2018Co-Authors: M Gholinia, Mohsen Pourfallah, H R ChamaniAbstract:Abstract The flow of the coolant fluid and its heat transfer directly affect the cooling performance, heat load of the hot parts and also the thermal efficiency of the diesel engine. The proper estimation of heat transfer and temperature distribution in a diesel engine is essential for investigating the thermal stresses and calculating its performance, which requires a precise simulation of the cooling water jacket. An efficient approach to study the cooling system is to simulate using Computational Fluid Dynamics (CFD) as a three-dimensional model by simultaneously solving the structure and fluid, which leads to accurate prediction of wall temperature and heat flux. In the present paper, the distribution of heat transfer coefficients (HTC) in the cooling jacket of a 16-cylinder heavy-duty diesel engine has been calculated using ANSYS/Fluent based on 3D-CFD method. Also, equations of subcooled Boiling Phenomenon have been solved based on methods of Chen and BDL, and the effects of fluid pressure, velocity, and temperature (At the time of the Phenomenon of Boiling) on the heat transfer of cooling jacket wall have been studied. The results show that the sensitive thermal region that is at risk is the region between the exhaust valve and around the glow-plug. This region if not properly cooled, will result in gas leakage from the combustion chamber, which will result in a decrease in engine power and torque.