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Sarit Kumar Das
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Sarit Kumar Das
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Sarit Kumar Das
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Das, Sarit
Das, S. K.
Das, Sarit Kumar
Kumar Das, Sarit
Das, Sarit K.
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3 results
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- PublicationA composite heat transfer model for pool boiling on a horizontal tube at moderate pressure(01-01-2004)
; Roetzel, WilfriedThe present work is aimed at building a comprehensive heat transfer model for pool boiling on horizontal tubes combining sliding bubble mechanism with natural convection, microlayer evaporation and transient conduction during boundary layer reformation, to predict the boiling heat flux for a given wall superheat. The model has been compared to experimental results from literature for R134a and also to independent experiments conducted by the authors for water. Even with a number of simplified assumptions a reasonably good agreement has been observed between model and experiments in the low and medium heat flux region and moderate pressure. - PublicationPool boiling characteristics of nano-fluids(01-02-2003)
; ;Putra, NandyRoetzel, WilfriedCommon fluids with particles of the order of nanometers in size are termed as 'nano-fluids' which have created considerable interest in recent times for their improved heat transfer capabilities. With very small volume fraction of such particles the thermal conductivity and convective heat transfer capability of these suspensions are significantly enhanced without the problems encountered in common slurries such as clogging, erosion, sedimentation and increase in pressure drop. This naturally brings out the question whether such fluids can be used for two phase applications or in other words phase change in such suspensions will be assistant or detrimental to the process of heat transfer. The present paper investigates into this question through experimental study of pool boiling in water-Al2O3 nano-fluids. The results indicate that the nano-particles have pronounced and significant influence on the boiling process deteriorating the boiling characteristics of the fluid. It has been observed that with increasing particle concentration, the degradation in boiling performance takes place which increases the heating surface temperature. This indicates that the role of transient conduction in pool boiling is overshadowed by some other effect. Since the particles under consideration are one to two orders of magnitude smaller than the surface roughness it was concluded that the change of surface characteristics during boiling due to trapped particles on the surface is the cause for the shift of the boiling characteristics in the negative direction. The results serve as a guidance for the design of cooling systems with nano-fluids where an overheating may occur if saturation temperature is attained. It also indicates the possibility of such engineered fluids to be used in material processing or heat treatment applications where a higher pre-assigned surface temperature is required to be maintained without changing the fluid temperature. © 2002 Elsevier Science Ltd. All rights reserved. - PublicationTemperature dependence of thermal conductivity enhancement for nanofluids(01-08-2003)
; ;Putra, Nandy ;Thiesen, PeterRoetzel, WilfriedUsual heat transfer fluids with suspended ultra fine particles of nanometer size are named as nanofluids, which have opened a new dimension in heat transfer processes. The recent investigations confirm the potential of nanofluids in enhancing heat transfer required for present age technology. The present investigation goes detailed into investigating the increase of thermal conductivity with temperature for nano fluids with water as base fluid and particles of Al2O3 or CuO as suspension material. A temperature oscillation technique is utilized for the measurement of thermal diffusivity and thermal conductivity is calculated from it. The results indicate an increase of enhancement characteristics with temperature, which makes the nanofluids even more attractive for applications with high energy density than usual room temperature measurements reported earlier.