scholarly journals Theoretical Investigation of the Deactivation of Ni Supported Catalysts for the Catalytic Deoxygenation of Palm Oil for Green Diesel Production

Catalysts ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 747
Author(s):  
Sanaa Hafeez ◽  
Sultan M Al-Salem ◽  
Kyriakos N Papageridis ◽  
Nikolaos D Charisiou ◽  
Maria A Goula ◽  
...  
Keyword(s):  
Palm Oil ◽  
Catalyst Deactivation ◽  
Supported Catalysts ◽  
Fluid Dynamic ◽  
Catalyst Activity ◽  
Cfd Model ◽  
Green Diesel ◽  
Zro2 Catalyst ◽  
Catalytic Deoxygenation ◽  
First Time

For the first time, a fully comprehensive heterogeneous computational fluid dynamic (CFD) model has been developed to predict the selective catalytic deoxygenation of palm oil to produce green diesel over an Ni/ZrO2 catalyst. The modelling results were compared to experimental data, and a very good validation was obtained. It was found that for the Ni/ZrO2 catalyst, the paraffin conversion increased with temperature, reaching a maximum value (>95%) at 300 °C. However, temperatures greater than 300 °C resulted in a loss of conversion due to the fact of catalyst deactivation. In addition, at longer times, the model predicted that the catalyst activity would decline faster at temperatures higher than 250 °C. The CFD model was able to predict this deactivation by relating the catalytic activity with the reaction temperature.

scholarly journals Decomposition of Additive-Free Formic Acid Using a Pd/C Catalyst in Flow: Experimental and CFD Modelling Studies

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 341
Author(s):  
Sanaa Hafeez ◽  
Felipe Sanchez ◽  
Sultan M. Al-Salem ◽  
Alberto Villa ◽  
George Manos ◽  
...  
Keyword(s):  
Experimental Data ◽  
Formic Acid ◽  
Catalyst Deactivation ◽  
Fluid Dynamic ◽  
Fixed Bed ◽  
Reaction System ◽  
Cfd Model ◽  
Cfd Modelling ◽  
Fresh Sample ◽  
Modelling Studies

The use of hydrogen as a renewable fuel has gained increasing attention in recent years due to its abundance and efficiency. The decomposition of formic acid for hydrogen production under mild conditions of 30 °C has been investigated using a 5 wt.% Pd/C catalyst and a fixed bed microreactor. Furthermore, a comprehensive heterogeneous computational fluid dynamic (CFD) model has been developed to validate the experimental data. The results showed a very good agreement between the CFD studies and experimental work. Catalyst reusability studies have shown that after 10 reactivation processes, the activity of the catalyst can be restored to offer the same level of activity as the fresh sample of the catalyst. The CFD model was able to simulate the catalyst deactivation based on the production of the poisoning species CO, and a sound validation was obtained with the experimental data. Further studies demonstrated that the conversion of formic acid enhances with increasing temperature and decreasing liquid flow rate. Moreover, the CFD model established that the reaction system was devoid of any internal and external mass transfer limitations. The model developed can be used to successfully predict the decomposition of formic acid in microreactors for potential fuel cell applications.

CFD Analysis of the Coolant Mixing within the Upper Plenum of a Pressurized Water Reactor (PWR)

2013 ◽  
Vol 444-445 ◽  
pp. 411-415 ◽  
Author(s):  
Fu Cheng Zhang ◽  
Shen Gen Tan ◽  
Xun Hao Zheng ◽  
Jun Chen
Keyword(s):  
Temperature Distribution ◽  
Fluid Dynamic ◽  
Characteristic Temperature ◽  
Reactor Core ◽  
Flow Distribution ◽  
Sensitivity Study ◽  
Cfd Model ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Water Reactor

In this study, a Computational Fluid Dynamic (CFD) model is established to obtain the 3-D flow characteristic, temperature distribution of the pressurized water reactor (PWR) upper plenum and hot-legs. In the CFD model, the flow domain includes the upper plenum, the 61 control rod guide tubes, the 40 support columns, the three hot-legs. The inlet boundary located at the exit of the reactor core and the outlet boundary is set at the hot-leg pipes several meters away from upper plenum. The temperature and flow distribution at the inlet boundary are given by sub-channel codes. The computational mesh used in the present work is polyhedron element and a mesh sensitivity study is performed. The RANS equations for incompressible flow is solved with a Realizable k-ε turbulence model using the commercial CFD code STAR-CCM+. The analysis results show that the flow field of the upper plenum is very complex and the temperature distribution at inlet boundary have significant impact to the coolant mixing in the upper plenum as well as the hot-legs. The detailed coolant mixing patterns are important references to design the reactor core fuel management and the internal structure in upper plenum.

Application of CFD Model for Inlet Flow Region of 17×17 Fuel Assembly

2006 ◽  
Author(s):  
Milorad B. Dzodzo ◽  
Bin Liu ◽  
Pablo R. Rubiolo ◽  
Zeses E. Karoutas ◽  
Michael Y. Young
Keyword(s):  
Fuel Assembly ◽  
Fluid Dynamic ◽  
Flow Distribution ◽  
Flow Region ◽  
Fretting Wear ◽  
Jet Flows ◽  
Cfd Model ◽  
Lateral Velocity ◽  
Fuel Assemblies ◽  
Inlet Conditions

A numerical investigation was performed to study the variation in axial and lateral velocity profiles occurring downstream of the inlet nozzle of a typical Westinghouse 17×17 PWR fuel assembly. A Computational Fluid Dynamic (CFD) model was developed with commercial CFD software. The model comprised the lower region of the fuel assembly, including: the Debris Filter Bottom Nozzle (DFBN), P-grid, Bottom Inconel grid, one and half grid span, as well as the lower core plate hole. The purpose of the study was to obtain insight into the flow redistribution resulting from the interaction of the jet arising from the lower core plate hole and the fuel assembly structure. In particular the axial and lateral velocities before and after the nozzle were studied. The results, axial and lateral velocity contours, streamlines and maximum axial and lateral velocity distributions at various elevations are presented and discussed in relation to the potential risk of high turbulent excitation over the rod and the resulting rod-to-grid fretting-wear damage. The CFD model results indicated that the large jet flows from the lower core plate are effectively dissipated by DFBN nozzle and the grids components of the fuel assembly. The breakup of the large jets in the DFBN and the lower grids helps to reduce the steep velocity gradients and thus the rod vibration and fretting-wear risk in the lower part of the fuel assembly. The presented CFD model is one step towards developing advanced tools that can be used to confirm and evaluate the effect of complex PWR structures on flow distribution. In the future the presented model could be integrated in a larger CFD model involving several fuel assemblies for evaluating the lateral velocities generated due to the non-uniform inlet conditions into the various fuel assemblies.

scholarly journals The Effect of Catalyst Support on the Decomposition of Methane to Hydrogen and Carbon

1970 ◽  
Vol 5 (1) ◽  
Author(s):  
Sharif Hussein Sharif Zein Abdul Rahman Mohamed
Keyword(s):  
Supported Catalysts ◽  
Catalyst Activity ◽  
Catalyst Support ◽  
Methane Decomposition ◽  
Filamentous Carbon ◽  
Transmission Electron ◽  
Decomposition Of Methane ◽  
Long Lifetime ◽  
The Relationship ◽  
Ni Supported Catalysts

Decomposition of methane into carbon and hydrogen over Cu/Ni supported catalysts was investigated. The catalytic activities and the lifetimes of the catalysts were studied. Cu/Ni supported on TiO2 showed high activity and long lifetime for the reaction. Transmission electron microscopy (TEM) studies revealed the relationship between the catalyst activity and the formation of the filamentous carbon over the catalyst after methane decomposition. While different types of filamentous carbon formed on the various Cu/Ni supported catalysts, an attractive carbon nanotubes was observed in the Cu/Ni supported on TiO2. Key Words:  Methane decomposition, carbon nanotube, Cu/Ni supported catalysts.

Raised Floor Computer Data Center: Effect on Rack Inlet Temperatures When Adjacent Racks Are Removed

2003 ◽  
Author(s):  
Roger Schmidt ◽  
Ethan Cruz
Keyword(s):  
Data Center ◽  
Control Volume ◽  
Fluid Dynamic ◽  
Computer Code ◽  
Cfd Model ◽  
Computer Data ◽  
Center Effect ◽  
Air Temperatures ◽  
Baseline Case ◽  
Finite Control

This paper focuses on the effect on inlet rack air temperatures when adjacent racks are removed. Only the above floor (raised floor) flow and temperature distributions were analyzed for various air flowrates exhausting from the perforated tiles and the rack. A Computational Fluid Dynamic (CFD) model was generated for the room with electronic equipment installed on a raised floor with particular focus on the effects on rack inlet temperatures of these high powered racks. The baseline case was with forty racks of data processing (DP) equipment arranged in rows in a data center cooled by chilled air exhausting from perforated floor tiles. The chilled air was provided by four A/C units placed inside a room 12.1 m wide × 13.4 m long. Since the arrangement of the racks in the data center was symmetric only one-half of the data center was modeled. To see the effect of missing racks adjacent to high powered racks various configurations were analyzed. The numerical modeling was performed using a commercially available finite control volume computer code called Flotherm (Trademark of Flomerics, Inc.). The flow was modeled using the k-e turbulence model. Results are displayed to provide some guidance on the design and layout of a data center.

Experimental and Numerical Characterization of an Orifice Type Cryogenic Pulse Tube Refrigerator

2011 ◽  
Author(s):  
Dion Savio Antao ◽  
Bakhtier Farouk
Keyword(s):  
Porous Media ◽  
Heat Exchanger ◽  
Fluid Dynamic ◽  
Travelling Wave ◽  
Cryogenic Cooling ◽  
Energy Separation ◽  
Pulse Tube ◽  
Cfd Model ◽  
Pulse Tube Refrigerator ◽  
Energy Equations

An orifice type pulse tube refrigerator (OPTR) was designed, built and operated to provide cryogenic cooling. The OTPR is a travelling wave thermoacoustic refrigerator that operates on a modified reverse Stirling cycle. We consider a system that is comprised of a pressure wave generator (a linear motor), an aftercooler heat-exchanger, a regenerator (comprising of a porous structure for energy separation), a pulse tube (in lieu of a displacer piston as found in Stirling refrigerators) with a cold and a warm heat-exchanger at its two ends, a needle-type orifice valve, an inertance tube and a buffer volume. The experimental characterization is done at various values of mean pressure of helium (∼ 0.35 MPa–2.2 MPa), amplitude of pressure oscillations, frequency of operation and size of orifice opening. A detailed time-dependent axisymmetric computational fluid dynamic (CFD) model of the OPTR is simulated to predict the performance of the OPTR. In the CFD model, the continuity, momentum and energy equations are solved for both the refrigerant gas (helium) and the porous media regions (the regenerator and the three heat-exchangers) in the OPTR. An accurate representation of heat transfer in the porous media is achieved by employing a thermal non-equilibrium model to couple the gas and solid (porous media) energy equations. In the future, a validated computational model can be used for system improvement and optimization.

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