Papers by Mohsen Nasr Esfahany
Journal of Applied Polymer Science, 2010
The effects of the condenser operation on properties of polyvinyl chloride (PVC) particles produc... more The effects of the condenser operation on properties of polyvinyl chloride (PVC) particles produced by suspension polymerization process were investigated in a pilot scale reactor. It was observed that delaying reflux operation increased the cold plasticizer absorption of the final resin. Both bulk density and K-value of the PVC powder decreased by increasing time delay in the reflux operation. It was also found that commencement of refluxing before 20% conversion resulted in bimodal particle size distribution (PSD), while monomodal PSD was obtained for longer delays in refluxing. SEM micrographs showed that surface of produced particles were rough and smooth when reflux started before and after 20% conversion, respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
International Communications in Heat and Mass Transfer, 2009
Effects of applying EHD and non-condensable (NC) gas contents have been experimentally studied on... more Effects of applying EHD and non-condensable (NC) gas contents have been experimentally studied on intertubular condensation of refrigerant R-134a flow. Applying of electrical field enhances condensing heat transfer coefficient (CHTC), but presence of NC gas in condensing vapour reduces this coefficient. In competition of these two effective parameters on condensation, it can be observed that at higher concentration of NC gas, the effect of electrical field on enhancement of CHTC is greatly reduced. But at lower concentration of NC gas, the effect of electrical field is more considerable, due to thickness of heat transfer boundary layer.
Marangoni convection experiments have been conducted with 5 cSt silicone oil liquid bridges to in... more Marangoni convection experiments have been conducted with 5 cSt silicone oil liquid bridges to investigate the effect of random g-jitter on the transition from steady to oscillatory convection at various aspect ratios in a half floating zone. A liquid bridge of 5 cSt silicone oil was suspended between two circular-coaxial disks both 7 mm in diameter and placed on a moving table which produced random g-jitter in all three directions. The g-jitter produced by the table was less than 12 mg simulating the g-jitter in the spacecraft enviroment. The effect of g-jitter was studied on critical temperature difference for different aspect ratios. It was concluded that g-jitter does not change the critical temperature difference in a half floating zone.
Industrial & Engineering Chemistry Research, 2010
The particle morphological properties of poly(vinyl chloride) produced by suspension polymerizati... more The particle morphological properties of poly(vinyl chloride) produced by suspension polymerization in a pilot-scale reactor under different reflux rates have been investigated. It was found that the monomer conversion decreased with increasing reflux rate. It was also observed that the cold plasticizer absorption (CPA) increased with reflux rate, whereas the bulk density (BD) and K value of the resin decreased. SEM micrographs showed that PVC resin with a rougher particle surface, more separate aggregates, and smaller primary particles was prepared at higher reflux rates. The particle size distribution determined by laser size analysis showed that the standard deviation of the particle size distribution and the mean particle size did not change significantly with reflux rate. Figure 9. K value of PVC resins produced at different reflux rates in series A and B.
Numerical Heat Transfer Part A-applications, 2007
Laminar-flow convective heat transfer of nanofluid in a circular tube with constant wall temperat... more Laminar-flow convective heat transfer of nanofluid in a circular tube with constant wall temperature boundary condition is investigated numerically. A dispersion model is used to account for the presence of nanoparticles. Numerical predictions are in agreement with experimental ...
Experimental Heat Transfer, 2009
... Etemad a & MN Esfahany a pages 217-227. ... Int. J. Thermophys. , 23: 571... more ... Etemad a & MN Esfahany a pages 217-227. ... Int. J. Thermophys. , 23: 571580. [CrossRef], [Web of Science ®], [CSA] View all references], the theoretical models, such as Maxwell and Hamilton-Crosser [1717. Hamilton, RL and Crosser, OK 1962. ...
International Communications in Heat and Mass Transfer, 2010
Laminar convective heat transfer of nanofluids in a circular tube under constant wall temperature... more Laminar convective heat transfer of nanofluids in a circular tube under constant wall temperature condition is studied numerically using a CFD 1 approach. Single-phase and two-phase models have been used for prediction of temperature, flow field, and calculation of heat transfer coefficient. Effects of some important parameters such as nanoparticle sources, nanoparticle volume fraction and nanofluid Peclet number on heat transfer rate have been investigated. The results of CFD simulation based on two-phase model were used for comparison with single-phase model, theoretical models and experimental data. Results have shown that heat transfer coefficient clearly increases with an increase in particle concentration. Also the heat transfer enhancement increases with Peclet number. Two-phase model shows better agreement with experimental measurements. For Cu/Water nanofluid with 0.2% concentration, the average relative error between experimental data and CFD results based on single-phase model was 16% while for two-phase model was 8%. Based on the results of the simulation it was concluded that the two-phase approach gives better predictions for heat transfer rate compared to the single-phase model.
Experimental Heat Transfer, 2009
... Etemad a & MN Esfahany a pages 217-227. ... Int. J. Thermophys. , 23: 571... more ... Etemad a & MN Esfahany a pages 217-227. ... Int. J. Thermophys. , 23: 571580. [CrossRef], [Web of Science ®], [CSA] View all references], the theoretical models, such as Maxwell and Hamilton-Crosser [1717. Hamilton, RL and Crosser, OK 1962. ...
Journal of Nanoparticle Research, 2010
In this investigation, laminar flow heat transfer enhancement in circular tube utilizing differen... more In this investigation, laminar flow heat transfer enhancement in circular tube utilizing different nanofluids including Al2O3 (20 nm), CuO (50 nm), and Cu (25 nm) nanoparticles in water was studied. Constant wall temperature was used as thermal boundary condition. The results indicate enhancement of heat transfer with increasing nanoparticle concentrations, but an optimum concentration for each nanofluid suspension can be found. Based on the experimental results, metallic nanoparticles show better enhancement of heat transfer coefficient in comparison with oxide particles. The promotions of heat transfer due to utilizing nanoparticles are higher than the theoretical correlation prediction.
International Communications in Heat and Mass Transfer, 2006
In the present investigation nanofluids containing CuO and Al2O3 oxide nanoparticles in water as ... more In the present investigation nanofluids containing CuO and Al2O3 oxide nanoparticles in water as base fluid in different concentrations produced and the laminar flow convective heat transfer through circular tube with constant wall temperature boundary condition were examined. ...
Journal of Applied Polymer Science, 2008
The effects of the dispersed phase to continuous phase ratio (weight of VCM (gr)/weight of water ... more The effects of the dispersed phase to continuous phase ratio (weight of VCM (gr)/weight of water (gr) (φ = gVCM/gwater)) on the particle properties of a poly(vinyl chloride) (PVC) suspension were investigated experimentally. A series of experiments were performed with different φ values in a pilot-scale reactor. The cold plasticizer absorption of the resin decreased with φ. Scanning electron micrographs showed that by the reduction of φ, many of the produced particles had a regular shape, a smooth surface, and greater porosity. An increase in φ caused a wider and multimodal particle size distribution of the produced PVC particles. The mean particle size and bulk density also increased with φ, whereas the molecular weight and polydispersity index did not change. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
International Journal of Thermal Sciences
Nucleate boiling and critical heat flux (CHF) of Fe 3 O 4 /ethylene glycolewater nanofluid at atm... more Nucleate boiling and critical heat flux (CHF) of Fe 3 O 4 /ethylene glycolewater nanofluid at atmospheric pressure on a horizontal thin NieCr wire were investigated. Fe 3 O 4 nanoparticles were dispersed in 50% (by volume) ethylene glycol/de-ionized water as base liquid in different concentrations (0.01e0.1% (by volume)). Experiments showed that boiling heat transfer coefficients deteriorate by increasing nanoparticle concentration in nanofluid. Addition of nanoparticles delays nucleate boiling incipience and increases CHF. Scanning Electron Microscope (SEM) graphs showed that porous layer of deposited nanoparticles formed on the heating surface boiled in nanofluid. The maximum CHF enhancement was obtained for 0.1% (by volume) nanofluid to be about 100%. Enhanced CHF was measured when previously boiled wire in nanofluid was used to boil the base fluid. Two different electrodes were used for applying electric field in the boiling nanofluids. Electric field applied in both configurations augmented boiling heat transfer coefficients while CHF remained almost unchanged.
Journal of Enhanced Heat Transfer, 2006
In this study, laminar convective heat transfer for CuO/water nanofluid, which is a suspension of... more In this study, laminar convective heat transfer for CuO/water nanofluid, which is a suspension of CuO nanoparticles in water, in a circular tube with the constant wall-temperature boundary condition was investigated experimentally. The heat-transfer coefficients for different ...
International Journal of Heat and Fluid Flow, 2007
In this study, the effect of a synthetic jet on the heat transfer of flow over a flat plate is in... more In this study, the effect of a synthetic jet on the heat transfer of flow over a flat plate is investigated experimentally. The experimental study is consist of a heater made of copper plate having constant heat flux located in the wind tunnel, and including a synthetic jet actuator injected into the stream by the entrance of plate. The synthetic jet is created by a piston-cylinder mechanism. In the investigations, the Reynolds number in the main stream, the frequency and amplitude of the actuator are changed while the geometry and Prandtl number remain constant for all cases and the effect of these parameters on the convective heat transfer is analyzed. The experiments are carried out at six different frequencies and four different amplitudes. To explain the heat transfer mechanism, the flow visualization is performed by using the smoke-wire method, and the instantaneous flow images are obtained. The experimental results reveal that there is a disruptive effect on the hydrodynamic boundary layer of the synthetic jet actuator. The obtained results are given as dimensionless parameters. It is observed that, the cycle-averaged Nusselt number increases with the increase of both Womersley number (Wo) and dimensionless amplitude (A o ).
Numerical Heat Transfer Part A-applications, 2007
Laminar-flow convective heat transfer of nanofluid in a circular tube with constant wall temperat... more Laminar-flow convective heat transfer of nanofluid in a circular tube with constant wall temperature boundary condition is investigated numerically. A dispersion model is used to account for the presence of nanoparticles. Numerical predictions are in agreement with experimental ...
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Papers by Mohsen Nasr Esfahany