The Experts below are selected from a list of 56511 Experts worldwide ranked by ideXlab platform

Mohammad Alhuyi Nazari - One of the best experts on this subject based on the ideXlab platform.

  • A review on geothermal Organic Rankine cycles: modeling and optimization
    Journal of Thermal Analysis and Calorimetry, 2020
    Co-Authors: Arman Haghighi, Mohammad Reza Pakatchian, Mamdouh El Haj Assad, Vinh Nguyen Duy, Mohammad Alhuyi Nazari
    Abstract:

    Employing renewable energy sources for power generation have been developed in recent years due to their several benefits including low emission of greenhouse gases and their inexhaustible nature. Among the applicable renewable energy sources for electricity generation, geothermal energy is one of the most appropriate ones owing to its independent availability from the weather condition. Due to the acceptable performance of Organic Rankine cycles (ORCs) in generating power from low- or medium-temperature heat sources, these cycles are appropriate choices for utilization in geothermal power plants. There are several parameters that influence the rate of power production and the efficiency of geothermal-based ORCs. The impacts of influential parameters have been investigated in several studies by modeling and optimization of these cycles. This article provides a comprehensive review of the previous studies focused on modeling and optimization of the ORCs with different configurations and Operating conditions, which would be useful for the researchers working in this field of science. Conclusions of the reviewed studies reveal that geothermal-based ORCs performance is significantly influenced by the applied Operating Fluid in the cycle, working condition in addition to configuration and architecture of the applied cycle. Moreover, studies that concentrated on the optimization of geothermal-based ORCs are also reviewed and their key conclusions are reflected as well. In the majority of the studies in this field, technical and economic objectives have been considered for optimization of the cycles. Depending on the characteristics of the case studies, the efficiency and cost of the generated power in optimized geothermal-based ORCs vary greatly. Finally, several recommendations are proposed for future studies in this field.

  • A review on using nanoFluids in heat pipes
    Journal of Thermal Analysis and Calorimetry, 2019
    Co-Authors: Mohammad Alhuyi Nazari, Roghayeh Ghasempour, Mohammad H. Ahmadi
    Abstract:

    The thermophysical specifications of working Fluid play a key role in thermal performance of various types of heat pipes. Fluids with high thermal conductivity, low viscosity and surface tension are more favorable to be applied in heat pipes. In order to have Fluids with higher thermal conductivity, adding nanoparticles can be an acceptable idea. In the present study, the effects of using nanoFluids in several types of heat pipes are reviewed. The nanoFluids are categorized based on the types of particles (as carbonic, metallic, etc.). Based on the results of the literature review, applying nanostructures in the base Fluid can significantly reduce the thermal resistance of heat pipes compared with utilizing pure as Operating Fluid. For instance, it is observed that using graphene oxide/water nanoFluid in pulsating heat pipe reduces the thermal resistance up to 42% in comparison with the water-filled heat pipe. In addition, reviewed studies revealed that the type of nanoparticle, concentration and their stability are among the most important parameters affecting thermal performance. The enhancement in thermal performance of heat pipes by using nanoFluid is mainly attributed to higher thermal conductivity of the nanoFluids and increase in nucleation sites.

Peter A. Jacobs - One of the best experts on this subject based on the ideXlab platform.

  • Development of a Computational Tool to Simulate Foil Bearings for Supercritical CO2 Cycles
    Journal of Engineering for Gas Turbines and Power, 2016
    Co-Authors: Kan Qin, Ingo Jahn, Rowan J. Gollan, Peter A. Jacobs
    Abstract:

    The foil bearing is an enabling technology for turbomachinery systems, which has the potential to enable cost efficient supercritical CO cycles. The direct use of the cycle's working Fluid within the bearings results in an oil-free and compact turbomachinery system; however, these bearings will significantly influence the performance of the whole cycle and must be carefully studied. Moreover, using CO as the Operating Fluid for a foil bearing creates new modeling challenges. These include highly turbulent flow within the film, non-negligible inertia forces, high windage losses, and nonideal gas behavior. Since the flow phenomena within foil bearings is complex, involving coupled Fluid flow and structural deformation, use of the conventional Reynolds equation to predict the performance of foil bearings might not be adequate. To address these modeling issues, a threedimensional flow and structure simulation tool has been developed to better predict the performance of foil bearings for the supercritical CO cycle. In this study, the gas dynamics code, EILMER, has been extended for multiphysics simulation by implementing a moving grid framework, in order to study the elastohydrodynamic performance of foil bearings. The code was then validated for representative laminar and turbulent flow cases, and good agreement was found between the new code and analytical solutions or experiment results. A separate finite difference code based on the Kirchoff plate equation for the circular thin plate was developed in Python to solve the structural deformation within foil thrust bearings, and verified with the finite element analysis from ANSYS. The Fluidstructure coupling algorithm was then proposed and validated against experimental results of a foil thrust bearing that used air as Operating Fluid. Finally, the new computational tool set is applied to the modeling of foil thrust bearings with CO as the Operating Fluid.

  • Validation of a three-dimensional CFD analysis of foil bearings with supercritical CO2
    2014
    Co-Authors: Kan Qin, Ingo Jahn, Peter A. Jacobs
    Abstract:

    Foil bearings are an integral part of oil-free turbomachines which have been selected as a potential technology to enable cost efficient Supercritical Carbon Dioxide Brayton cycle for solar power application. Using high pressure CO2 as the Operating Fluid means that within the film Reynolds numbers in the highly turbulent regime are observed, therefore, using traditional simulation tools, such as two-dimensional Reynolds equation, derived for simulating bearing Operating with laminar flow is not appropriate. The resulting turbulence enhances hydrodynamic load capacity and increases frictional losses. In this study, some improvements such as moving wall and periodic boundary conditions to the UQ in-house CFD code Eilmer are presented. These are verified using Taylor-Couette flow, and axisymmetric and wavy Taylor vortices are simulated under different Taylor number. A hydrostatic air thrust bearing with steady-state behaviour is also studied, which shows good agreement with the results from modified Reynolds equation. Finally, a preliminary Three-Dimensional Computational Fluid Dynamic simulation of a foil bearings is presented. A rigid foil bearing is studied with ambient air and high pressure CO2 as Operating Fluid, respectively and the lift force and power loss are compared with the results from Reynolds equation.

Mohammad H. Ahmadi - One of the best experts on this subject based on the ideXlab platform.

  • A review on using nanoFluids in heat pipes
    Journal of Thermal Analysis and Calorimetry, 2019
    Co-Authors: Mohammad Alhuyi Nazari, Roghayeh Ghasempour, Mohammad H. Ahmadi
    Abstract:

    The thermophysical specifications of working Fluid play a key role in thermal performance of various types of heat pipes. Fluids with high thermal conductivity, low viscosity and surface tension are more favorable to be applied in heat pipes. In order to have Fluids with higher thermal conductivity, adding nanoparticles can be an acceptable idea. In the present study, the effects of using nanoFluids in several types of heat pipes are reviewed. The nanoFluids are categorized based on the types of particles (as carbonic, metallic, etc.). Based on the results of the literature review, applying nanostructures in the base Fluid can significantly reduce the thermal resistance of heat pipes compared with utilizing pure as Operating Fluid. For instance, it is observed that using graphene oxide/water nanoFluid in pulsating heat pipe reduces the thermal resistance up to 42% in comparison with the water-filled heat pipe. In addition, reviewed studies revealed that the type of nanoparticle, concentration and their stability are among the most important parameters affecting thermal performance. The enhancement in thermal performance of heat pipes by using nanoFluid is mainly attributed to higher thermal conductivity of the nanoFluids and increase in nucleation sites.

Valentino Cucit - One of the best experts on this subject based on the ideXlab platform.

  • Influence of Polymer Solution on Pump Performances
    Energy Procedia, 2017
    Co-Authors: Fabio Burlon, Diego Micheli, Riccardo Furlanetto, Michele Simonato, Valentino Cucit
    Abstract:

    Abstract In professional warewashing machines, as for example the model of Electrolux Rack Type, the working conditions of the pump are affected by the Operating Fluid properties, which are different from those of pure water. In fact, the actual trend in this kind of professional appliances is to reduce both energy consumption and time needed for cleaning process: this involves short washing cycles conducted at low temperatures with a solution of water and highly concentrated chemistry. Detergents contain different components and additives, as polymers and surfactants, which can affect the performance of the pump, including cavitation inception conditions. Cavitation leads to flow instabilities, affecting pump performances and inducing an increment in the level of vibrations and noise. While cavitation phenomena in Newtonian Fluids is well known, particularly as far as pure water is concerned, in literature there are also various studies on cavitating flows in presence of diluted solutions of polymers additives in water, but only few studies are available regarding the effect of detergent components on pumps cavitation and, in general, on pumps performances. The wide range of variables affecting the phenomenon has led to the development of a laboratory rig for testing centrifugal pumps with aqueous solutions representative of those used in the warewashing sector [1]. This paper presents the results of tests performed with various solutions of a polymer (Polyox WSR301) in water. A rheometric analysis has been previously performed on samples of some of the tested solutions, for characterizing their behavior in terms of both viscosity in laminar conditions and their classification as “diluted” or “concentrated”. For each solution, the resulting performance curves of the pump are then compared with those obtained with pure water.

Kan Qin - One of the best experts on this subject based on the ideXlab platform.

  • Development of a Computational Tool to Simulate Foil Bearings for Supercritical CO2 Cycles
    Journal of Engineering for Gas Turbines and Power, 2016
    Co-Authors: Kan Qin, Ingo Jahn, Rowan J. Gollan, Peter A. Jacobs
    Abstract:

    The foil bearing is an enabling technology for turbomachinery systems, which has the potential to enable cost efficient supercritical CO cycles. The direct use of the cycle's working Fluid within the bearings results in an oil-free and compact turbomachinery system; however, these bearings will significantly influence the performance of the whole cycle and must be carefully studied. Moreover, using CO as the Operating Fluid for a foil bearing creates new modeling challenges. These include highly turbulent flow within the film, non-negligible inertia forces, high windage losses, and nonideal gas behavior. Since the flow phenomena within foil bearings is complex, involving coupled Fluid flow and structural deformation, use of the conventional Reynolds equation to predict the performance of foil bearings might not be adequate. To address these modeling issues, a threedimensional flow and structure simulation tool has been developed to better predict the performance of foil bearings for the supercritical CO cycle. In this study, the gas dynamics code, EILMER, has been extended for multiphysics simulation by implementing a moving grid framework, in order to study the elastohydrodynamic performance of foil bearings. The code was then validated for representative laminar and turbulent flow cases, and good agreement was found between the new code and analytical solutions or experiment results. A separate finite difference code based on the Kirchoff plate equation for the circular thin plate was developed in Python to solve the structural deformation within foil thrust bearings, and verified with the finite element analysis from ANSYS. The Fluidstructure coupling algorithm was then proposed and validated against experimental results of a foil thrust bearing that used air as Operating Fluid. Finally, the new computational tool set is applied to the modeling of foil thrust bearings with CO as the Operating Fluid.

  • Validation of a three-dimensional CFD analysis of foil bearings with supercritical CO2
    2014
    Co-Authors: Kan Qin, Ingo Jahn, Peter A. Jacobs
    Abstract:

    Foil bearings are an integral part of oil-free turbomachines which have been selected as a potential technology to enable cost efficient Supercritical Carbon Dioxide Brayton cycle for solar power application. Using high pressure CO2 as the Operating Fluid means that within the film Reynolds numbers in the highly turbulent regime are observed, therefore, using traditional simulation tools, such as two-dimensional Reynolds equation, derived for simulating bearing Operating with laminar flow is not appropriate. The resulting turbulence enhances hydrodynamic load capacity and increases frictional losses. In this study, some improvements such as moving wall and periodic boundary conditions to the UQ in-house CFD code Eilmer are presented. These are verified using Taylor-Couette flow, and axisymmetric and wavy Taylor vortices are simulated under different Taylor number. A hydrostatic air thrust bearing with steady-state behaviour is also studied, which shows good agreement with the results from modified Reynolds equation. Finally, a preliminary Three-Dimensional Computational Fluid Dynamic simulation of a foil bearings is presented. A rigid foil bearing is studied with ambient air and high pressure CO2 as Operating Fluid, respectively and the lift force and power loss are compared with the results from Reynolds equation.