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Experimental research on heat transfer of water in tubes with conical ring inserts in transient regime
, Article International Communications in Heat and Mass Transfer ; Volume 38, Issue 5 , 2011 , Pages 668-671 ; 07351933 (ISSN) ; Lotfi, R ; Rashidi, A. M ; Sattari, S ; Sharif University of Technology
2011
Abstract
Forced convective of water in horizontal tubes with conical tube inserts has been studied experimentally. The transient flow regime has been used for the tests. Experimental results are validated with existing well established correlation. The turbulators were placed in two different arrangements: converging conical ring, referred to as CR array and diverging conical ring, DR array. Two correlations for the Nusselt number based on the experiment are introduced for practical use. It is found that the insertion of turbulators has enhanced the Nusselt number for the DR arrangement up to 521%, and for the CR arrangement up to 355%, although using the turbulators cause a significant increase in...
An experimental study on the proper criterion to judge the thermal performance of the nanofluids
, Article International Communications in Heat and Mass Transfer ; Volume 82 , 2017 , Pages 20-28 ; 07351933 (ISSN) ; Jafari, M ; Nasirivatan, S ; Osanloo, B ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
This work is dedicated to finding a suitable measure to judge thermal performance of nanofluids. The importance of this issue arises from misleading claim of excess heat transfer of nanofluids compared to the base fluid, neglecting the hydraulic effects such as increase in pressure drop. To clarify the issue, the experimental setup with capability to create constant Reynolds number and constant pumping power is constructed. Thermal behavior of nanofluids of silicon oxide/water and aluminum oxide/water and distilled water in developing region of laminar flow regime is investigated. In this regard, the convective heat transfer coefficient within the finned tube heat exchanger is evaluated....
Simulation of compressible and incompressible flows through planar and axisymmetric abrupt expansions
, Article Journal of Fluids Engineering, Transactions of the ASME ; Volume 141, Issue 11 , 2019 ; 00982202 (ISSN) ; Shafiei Ghazani, A ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2019
Abstract
In this paper, compressible and incompressible flows through planar and axisymmetric sudden expansion channels are investigated numerically. Both laminar and turbulent flows are taken into consideration. Proper preconditioning in conjunction with a second-order accurate advection upstream splitting method (AUSM+-up) is employed. General equations for the loss coefficient and pressure ratio as a function of expansion ratio, Reynolds number, and the inlet Mach number are obtained. It is found that the reattachment length increases by increasing the Reynolds number. Changing the flow regime to turbulent results in a decreased reattachment length. Reattachment length increases slightly with a...
Investigation of counterflow microchannel heat exchanger with hybrid nanoparticles and pcm suspension as a coolant
, Article Mathematical Problems in Engineering ; Volume 2021 , 2021 ; 1024123X (ISSN) ; Khafeef, M. J ; Mohammadi, O ; Bhattacharyya, S ; Issakhov, A ; Sharif University of Technology
Hindawi Limited
2021
Abstract
The effect of the hybrid suspension on the intrinsic characteristics of microencapsulated phase change material (MEPCM) slurry used as a coolant in counterflow microchannel heat exchanger (CFMCHE) with different velocities is investigated numerically. The working fluid used in this paper is a hybrid suspension consisting of nanoparticles and MEPCM particles, in which the particles are suspended in pure water as a base fluid. Two types of hybrid suspension are used (Al2O3 +MEPCM and Cu + MEPCM), and the hydrodynamic and thermal characteristics of these suspensions flowing in a CFMCHE are numerically investigated. The results indicated that using hybrid suspension with high flow velocities...