Abstract: Passive liquid water recovery from fuel cell effluent can be achieved by designing effective desiccant. Recovered water from desiccant is used for humidification of proton exchange membrane (PEM) to maintain at hydrated state. Proper membrane humidity is crucial to ensure optimal operation of a PEM to generate electricity. In this study a desiccant called water separator is designed, it works without consuming any external energy. The main aim of designing a component is to recover liquid water from hundred percent humidified air (vapour) which is coming out from cathode compartment of fuel stack and it is further used for humidifying the oxidant before entering the stack inlet. The self-sufficient water in vapour is investigated theoretically and experimentally. When the water separator temperature reached the critical point especially in large power applications or long time operation, recovered water was not sufficient for air humidification. On the contrary, it is sufficient while the temperature of water separator was below critical line. The temperature of separator is controlled by providing adequate heat transfer. The recovered amount of water by condensing the outlet gas or vapour to a proper temperature, easily satisfy required amount for humidification of oxidant at inlet of stack.
Keywords:cell stack, Proton exchange membrane, Humidification, Vapour, Liquid water recovery.
Simulation Studies Of Premixed N-Pentane/Air Liquid Micro CombustionIJERA Editor
With latest improvements in MEMS, combustion based Micro-Power generation devices are seen as alternatives for conventional batteries because of the high energy densities of Hydrogen and other hydrocarbon fuels. An important feature of micro-power system is to utilize the combustion of fuel or propellant in the micro-burner to produce the gas with high temperature and high pressure to drive turbines or other power units, which convert chemical into energy directly or indirectly other forms of energy, for example heat or power. We have concentrated on the usage of Micro combustion as a substitute for conventional batteries .In our study, a Micro Combustor of 1mm x 10mm is taken for Numerical Study. Combustion characteristics of N Pentane-Air mixture in a planar micro-channel is studied numerically. We have performed the liquid fuel combustion of n-Pentane and air to study the effects of liquid fuel combustion in a micro channel. The effect of axial velocity inlet, on exhaust gas temperature and Hydrogen Peroxide addition on exhaust gas concentration was analyzed respectively. We also investigated numerically the combustion characteristics under different conditions such as by varying the DPM, Number of Fuel Streams, and Spray Angle and so on. For this numerical analysis, an experimental model is considered as reference, and the geometry and the boundary conditions are taken from it for the purpose of simulation. In this study, n-Pentane is introduced as liquid droplets at the centerline and the liquid combustion is simulated numerically.
This document presents a mathematical model for predicting heat losses from a tar sand formation to adjacent formations during thermal recovery processes like steamflooding. The model is developed using conservation of energy principles and heat transfer equations. Sensitivity analyses are performed using the model to analyze how variations in properties of the tar sand formation and steam affect the rate of heat loss. The analyses reveal that increases or decreases in properties like steam and tar sand density can increase or decrease the rate of heat loss. However, some property variations have minimal effect on heat losses. The model can help optimize steam injection parameters to minimize heat losses and improve thermal recovery efficiency.
International Journal of Computational Engineering Research(IJCER)ijceronline
International Journal of Computational Engineering Research(IJCER) is an intentional online Journal in English monthly publishing journal. This Journal publish original research work that contributes significantly to further the scientific knowledge in engineering and Technology.
Experimental Study of Heat Transfer Enhancement by using ZnO and Al2O3 Water ...IRJET Journal
This study experimentally analyzed heat transfer enhancement using ZnO and Al2O3 water-based nanofluids in a car radiator. An experimental setup similar to a car's cooling system was developed. Different volume concentrations of nanoparticles (0.1-0.4%) were tested in water. Heat transfer of the nanofluids increased with rising volume concentration and flow rate. ZnO nanofluid provided the highest heat transfer, up to 70% more than water. The maximum heat transfer occurred at a 0.2% volume concentration and 8 L/min flow rate for both nanofluids. Overall, ZnO nanofluid showed the best thermal performance and is a promising coolant for improving heat dissipation in car radiators.
This document describes a study evaluating different steam cycle designs to provide heat and power for a CO2 capture system on an offshore oil and gas installation. Three steam cycle configurations were modeled - an extraction condensing turbine, backpressure turbine, and combination cycle. The backpressure cycle was found to provide all necessary steam and power for CO2 capture and compression with some excess capacity. Weight relationships for major equipment were developed to estimate how cycle components would scale with changes in gas turbine exhaust flow. The study aims to identify the best steam cycle design for offshore CO2 capture applications.
This document outlines a dissertation proposal to study the effect of geometric parameters on the performance of an annular gas turbine combustion chamber using computational fluid dynamics (CFD). The proposal includes a literature review summarizing previous research on combustion chamber design and CFD modeling. The proposed methodology describes collecting existing dimension data, modeling the combustion chamber geometry, mesh generation, and performing CFD analysis in ANSYS Fluent to optimize performance by varying parameters like swirl angle, nozzle location and size, and hole placement and size.
Performance prediction of a thermal system using Artificial Neural NetworksIJERD Editor
This document summarizes a study on using artificial neural networks (ANNs) to predict the performance of a condenser system and assess fouling over time. Experiments were conducted on an industrial condenser to collect temperature and flow rate data. An ANN model was developed and trained to predict the overall heat transfer coefficient of the clean condenser system based on the input parameters. The model was then used to calculate the fouling factor by comparing the predicted clean performance to the actual performance measured over time, indicating degradation due to fouling on the heat transfer surfaces. The developed system provides a method to monitor condenser performance and identify when cleaning is needed to improve efficiency.
Boiling and Condensation heat transfer -- EES Functions and Procedurestmuliya
This file contains notes on Engineering Equation Solver (EES) Functions and Procedures for Boiling and Condensation heat transfer. Some problems are also included.
These notes were prepared while teaching Heat Transfer course to the M.Tech. students in Mechanical Engineering Dept. of St. Joseph Engineering College, Vamanjoor, Mangalore, India.
Contents: Summary of formulas used -
EES Functions/Procedures for boiling: Nucleate boiling heat flux for any geometry - critical heat flux for large horizontal surface, horizontal cylinder and sphere - Film boiling for horizontal cylinder, sphere and horizontal surface – Problems.
EES Functions/Procedures for condensation of: steam on vertical surface – any fluid on a vertical surface – steam on vertical cylinder – any fluid on vertical cylinder – steam on horizontal cylinder – any fluid on horizontal cylinder – steam on a horizontal tube bank – any fluid on horizontal tube bank – any fluid on a sphere – any fluid inside a horizontal cylinder - Problems.
It is hoped that these notes will be useful to teachers, students, researchers and professionals working in this field.
Simulation Studies Of Premixed N-Pentane/Air Liquid Micro CombustionIJERA Editor
With latest improvements in MEMS, combustion based Micro-Power generation devices are seen as alternatives for conventional batteries because of the high energy densities of Hydrogen and other hydrocarbon fuels. An important feature of micro-power system is to utilize the combustion of fuel or propellant in the micro-burner to produce the gas with high temperature and high pressure to drive turbines or other power units, which convert chemical into energy directly or indirectly other forms of energy, for example heat or power. We have concentrated on the usage of Micro combustion as a substitute for conventional batteries .In our study, a Micro Combustor of 1mm x 10mm is taken for Numerical Study. Combustion characteristics of N Pentane-Air mixture in a planar micro-channel is studied numerically. We have performed the liquid fuel combustion of n-Pentane and air to study the effects of liquid fuel combustion in a micro channel. The effect of axial velocity inlet, on exhaust gas temperature and Hydrogen Peroxide addition on exhaust gas concentration was analyzed respectively. We also investigated numerically the combustion characteristics under different conditions such as by varying the DPM, Number of Fuel Streams, and Spray Angle and so on. For this numerical analysis, an experimental model is considered as reference, and the geometry and the boundary conditions are taken from it for the purpose of simulation. In this study, n-Pentane is introduced as liquid droplets at the centerline and the liquid combustion is simulated numerically.
This document presents a mathematical model for predicting heat losses from a tar sand formation to adjacent formations during thermal recovery processes like steamflooding. The model is developed using conservation of energy principles and heat transfer equations. Sensitivity analyses are performed using the model to analyze how variations in properties of the tar sand formation and steam affect the rate of heat loss. The analyses reveal that increases or decreases in properties like steam and tar sand density can increase or decrease the rate of heat loss. However, some property variations have minimal effect on heat losses. The model can help optimize steam injection parameters to minimize heat losses and improve thermal recovery efficiency.
International Journal of Computational Engineering Research(IJCER)ijceronline
International Journal of Computational Engineering Research(IJCER) is an intentional online Journal in English monthly publishing journal. This Journal publish original research work that contributes significantly to further the scientific knowledge in engineering and Technology.
Experimental Study of Heat Transfer Enhancement by using ZnO and Al2O3 Water ...IRJET Journal
This study experimentally analyzed heat transfer enhancement using ZnO and Al2O3 water-based nanofluids in a car radiator. An experimental setup similar to a car's cooling system was developed. Different volume concentrations of nanoparticles (0.1-0.4%) were tested in water. Heat transfer of the nanofluids increased with rising volume concentration and flow rate. ZnO nanofluid provided the highest heat transfer, up to 70% more than water. The maximum heat transfer occurred at a 0.2% volume concentration and 8 L/min flow rate for both nanofluids. Overall, ZnO nanofluid showed the best thermal performance and is a promising coolant for improving heat dissipation in car radiators.
This document describes a study evaluating different steam cycle designs to provide heat and power for a CO2 capture system on an offshore oil and gas installation. Three steam cycle configurations were modeled - an extraction condensing turbine, backpressure turbine, and combination cycle. The backpressure cycle was found to provide all necessary steam and power for CO2 capture and compression with some excess capacity. Weight relationships for major equipment were developed to estimate how cycle components would scale with changes in gas turbine exhaust flow. The study aims to identify the best steam cycle design for offshore CO2 capture applications.
This document outlines a dissertation proposal to study the effect of geometric parameters on the performance of an annular gas turbine combustion chamber using computational fluid dynamics (CFD). The proposal includes a literature review summarizing previous research on combustion chamber design and CFD modeling. The proposed methodology describes collecting existing dimension data, modeling the combustion chamber geometry, mesh generation, and performing CFD analysis in ANSYS Fluent to optimize performance by varying parameters like swirl angle, nozzle location and size, and hole placement and size.
Performance prediction of a thermal system using Artificial Neural NetworksIJERD Editor
This document summarizes a study on using artificial neural networks (ANNs) to predict the performance of a condenser system and assess fouling over time. Experiments were conducted on an industrial condenser to collect temperature and flow rate data. An ANN model was developed and trained to predict the overall heat transfer coefficient of the clean condenser system based on the input parameters. The model was then used to calculate the fouling factor by comparing the predicted clean performance to the actual performance measured over time, indicating degradation due to fouling on the heat transfer surfaces. The developed system provides a method to monitor condenser performance and identify when cleaning is needed to improve efficiency.
Boiling and Condensation heat transfer -- EES Functions and Procedurestmuliya
This file contains notes on Engineering Equation Solver (EES) Functions and Procedures for Boiling and Condensation heat transfer. Some problems are also included.
These notes were prepared while teaching Heat Transfer course to the M.Tech. students in Mechanical Engineering Dept. of St. Joseph Engineering College, Vamanjoor, Mangalore, India.
Contents: Summary of formulas used -
EES Functions/Procedures for boiling: Nucleate boiling heat flux for any geometry - critical heat flux for large horizontal surface, horizontal cylinder and sphere - Film boiling for horizontal cylinder, sphere and horizontal surface – Problems.
EES Functions/Procedures for condensation of: steam on vertical surface – any fluid on a vertical surface – steam on vertical cylinder – any fluid on vertical cylinder – steam on horizontal cylinder – any fluid on horizontal cylinder – steam on a horizontal tube bank – any fluid on horizontal tube bank – any fluid on a sphere – any fluid inside a horizontal cylinder - Problems.
It is hoped that these notes will be useful to teachers, students, researchers and professionals working in this field.
Improved processes of light hydrocarbon separation from lngHasan Gumus
This document proposes two novel processes for separating light hydrocarbons like ethane from liquefied natural gas (LNG) using the cryogenic energy released during LNG regasification. The first process, called the "high pressure process", uses a demethanizer operating at 4.5 MPa to recover over 99.99% methane, then compresses the methane-rich natural gas. The second process, called the "low pressure process", uses a lower pressure demethanizer at 2.4 MPa and re-liquefies the methane-rich stream, pressurizing it with pumps instead of compressors. Both processes produce liquefied ethane and LPG at atmospheric pressure with acceptable power
This document presents research on developing an emissions prediction capability for use in conceptual aircraft engine design. A physics-based modeling approach was used consisting of 1D flow models of different combustor types, chemical reactor networks representing the combustor flowfields, and regression models. Models were developed for a single annular combustor, rich-quench-lean combustor, and lean-burn combustor. The models were implemented in NPSS and validated against test data. Regression models were also created to rapidly predict emissions for parametric studies of a CFM56-sized engine application. The new capability allows emissions predictions during early engine conceptual design when cycle parameters and architectures are varied.
This paper addresses the numerical simulation of
helically coiled closed loop pulsating heat pipe which is carried
in ANSYS Fluent. The values of thermal resistance for
constant heat fluxes vs. transient heat fluxes are analyzed.
Phase change visualization after the end of simulation is
carried out to observe the phenomenon in liquid at its
saturation temperature and pressure. Finally, helical heat
pipes are found to have thermal resistance less by 2.7K/W,
0.56 K/W, and 0.227 K/W for 8W, 40W and 80W heat inputs
than circular pipes. Helical heat pipes are found more efficient
than circular heat pipes.
The document analyzes heat transfer in the hot gas path of a gas turbine for a semi-closed oxy-combustion combined cycle (SCOC-CC) power plant under different operating conditions. It evaluates the convective and radiative heat transfer to the first row turbine vane using empirical correlations. The analysis shows that SCOC-CC with flue gas recirculation before condensation results in 20-30% higher heat transfer compared to recirculation after condensation. Increasing the pressure ratio from 17 to 40 at constant thermal power and turbine inlet temperature increases both convective and radiative heat transfer by about 10%. Chemiluminescence is found to have a negligible effect on heat transfer as the
This document presents a theoretical analysis of the performance of a vapor compression refrigeration system using different refrigerants: R-12, R134a, and R1234yf. The analysis uses a computational model based on the first law of thermodynamics to investigate the effects of evaporating temperature, subcooling, condenser temperature, and liquid-vapor heat exchanger effectiveness on the system's coefficient of performance and refrigerating capacity. The results show that R1234yf has the highest relative capacity increase with increased subcooling and the highest percentage increase in COP. R134a requires the most compressor work. R1234yf is identified as a promising alternative to R134a due to its low global warming potential
This document summarizes a study on the thermal performance of a shell and tube heat exchanger using nanofluids. Finite volume modeling was used to analyze heat transfer and flow characteristics. Various nanofluids including Ag, Al2O3, CuO, SiO2, and TiO2 suspensions in water were tested and compared to pure water. The objectives were to analyze temperature profiles, heat transfer coefficients, pressure drops, and effectiveness. Results showed nanofluids had higher overall temperatures indicating more heat transfer compared to water alone. This study analyzed the potential for nanofluids to enhance heat exchanger performance.
The student researchers measured the stack velocity at the University of Utah's High Temperature Water Plant and found it was higher than expected based on the reported firing rate. They determined the plant's method of calculating firing rate based only on hot water output underestimated the true rate by neglecting electric power generation and heat losses. The researchers concluded future stack velocity calculations should use the natural gas firing rate and that negative static pressure measurements are invalid. Improved measurement equipment and procedures were also recommended.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
This document describes a CFD analysis of fluid flow through tube banks in heat recovery steam generators (HRSGs). The authors developed a new procedure to define porous medium parameters like loss coefficients starting from 3D simulations of flow through tube banks. Both finned and bare tube banks were considered. The analysis was performed using the commercial CFD code Fluent to simulate flow through a single tube row and investigate the effects of Reynolds number, inlet yaw angle, and inlet pitch angle on pressure drop and outlet flow angles. Results were compared to experimental data for a real fired HRSG to validate the proposed porous media modeling approach.
Thermodynamic analysis of vapour compression refrigeration system using alte...IOSR Journals
This document discusses thermodynamic analysis of alternative refrigerants for vapor compression refrigeration systems. It aims to analyze the environmental and energy consumption impacts of various refrigerants. The document defines key terms like ozone depletion potential and global warming potential. It then analyzes several potential refrigerant alternatives to R22 and R134a like propane, isobutane, R410a, R407c, and a mixture called MO9. The thermodynamic properties of these refrigerants are obtained from software and their coefficients of performance are compared. The analysis found that MO9 shows potential as a suitable substitute for R134a in new and retrofit systems due to its performance and lower environmental impact.
This document discusses the thermal design of a simple boiler. It presents the calculation procedures for boiler design, focusing on heat transfer modes, heat and mass balances, and a worked example. The key points are:
- Heat transfer in boilers occurs via conduction, convection, and radiation. Conduction is not considered in simple calculations.
- Heat and mass balance equations relate the heat input from fuel to the heat output via steam as well as accounting for air and flue gas flows.
- A worked example calculates furnace conditions like flue gas temperature for a methane-fueled boiler, assuming radiation is the only heat transfer mode in the furnace. Tube bank calculations then determine the exit gas
This document summarizes an experiment investigating the behavior of a single fuel cell under different membrane electrode assemblies (MEAs) and fuels. Three MEAs using different catalysts were tested with hydrogen and formic acid as anode fuels and hydrogen, air, or water as cathode reactants. Constant base current with 10A pulses were applied to alleviate carbon monoxide poisoning on the anode. Results including polarization curves and potential/current oscillations are presented. The document also provides background on fuel cells and mechanisms of carbon monoxide poisoning.
The document summarizes an experimental investigation on the performance of an air conditioner using R32 refrigerant. It begins with an abstract describing the refrigerant comparison experiment conducted on a 1.5 ton capacity air conditioning system using R22, R134a, and R32. Performance parameters like coefficient of performance, mass flow rate, and power to the compressor were calculated. The results and simulations showed R32 to be the most efficient refrigerant for retrofitting air conditioning systems due to its lower global warming potential and atmospheric lifetime compared to R22.
The document summarizes a study analyzing the effect of heat transfer on the spring characteristics of hydro-pneumatic struts used in vehicle suspensions. A thermal time constant model was developed using real gas equations of state to model the irreversible heat transfer during compression and expansion cycles. The analysis defines a non-dimensional frequency parameter and shows through numerical simulation that this single parameter fully characterizes the energy dissipation and spring behavior of hydro-pneumatic springs regardless of other variables. The existence of this parameter is also determined analytically by modeling the hydro-pneumatic spring as an anelastic model.
The understanding of gas geochemical model to reduce the exploration uncertaintyRizal Abiyudo
The various fumaroles areas in the prospect are can be modelled by boiling depletion model and the relation between each of fumaroles. Geothermal waters would boil to create a first set of fumaroles and then the boiled, gas-depleted water outflows to the site of a second set of fumaroles where it boils again, creating fumaroles with gas-depleted chemistry.
Penga Ž, Tolj I, Barbir F, Computational fluid dynamics study of PEM fuel cel...Željko Penga
This computational fluid dynamics study examines PEM fuel cell performance under isothermal and non-uniform temperature boundary conditions. The study finds that implementing a non-uniform temperature profile along the cathode channel, as calculated from a Mollier h-u chart, results in close to 100% relative humidity without external humidification and improves fuel cell performance. The model polarization curve and relative humidity distribution agree well with experimental results. Different current collector materials and membrane thickness influence temperature and relative humidity distributions through their effects on thermal conductivity and water transport.
Exploring LPG Cylinders for Medical Oxygen - A Preliminary StudyVijay Sarathy
This document studies using LPG cylinders to supply medical oxygen in emergencies. It analyzes how long oxygen can be supplied from an LPG cylinder at flow rates of 0.5 and 2 liters per minute. The study finds the cylinder can supply oxygen at 0.5 liters/min for about 3 hours and at 2 liters/min for about 45 minutes before the pressure drops to 1 atmosphere. Governing equations for transient blowdown of the cylinder are derived in the appendices.
This document describes using Excel to optimize the thermal design of systems. It provides an example of optimizing the insulation thickness and pipe diameter of an insulated pipe to minimize costs. Excel is able to calculate the total cost as a function of diameter and use its Solver tool to iteratively find the optimal diameter that minimizes cost. This provides an effective way for students to learn thermal design optimization compared to analytical optimization, as it can handle multiple design factors and parameters. The document then presents another example of using this approach to optimize the diameters and insulation thicknesses of two sections of an air conditioning duct to minimize owning costs.
An experimental and kinetic study of syngas-air combustion at elevated temper...Saad Tanvir
This document describes an experimental study of syngas combustion at elevated temperatures and the effect of adding water. Laminar flame speeds of syngas/air mixtures were measured over a range of fuel compositions, equivalence ratios, and preheat temperatures. The measured flame speeds were compared to simulations from existing chemical kinetic models, showing reasonable agreement at room temperature but large discrepancies at higher temperatures. Water was added to two syngas fuels up to 40% by volume, and different effects on flame speed were observed depending on the fuel composition and water concentration, related to competing chemical and physical impacts of water addition.
Option C Nernst Equation, Voltaic Cell and Concentration CellLawrence kok
This document provides a tutorial on voltaic cells, the Nernst equation, and concentration cells. It discusses the basic components and workings of voltaic cells, including the conversion of chemical energy to electrical energy through redox reactions. Equations for cell potential (Ecell), standard electrode potential (E°), and the Nernst equation are presented. Examples of specific voltaic cells like Daniell cells and their cell potentials are provided. The relationships between Gibbs free energy (ΔG), equilibrium constant (Kc), and cell potential are also summarized.
The document discusses the second law of thermodynamics. It states that heat always flows spontaneously from hotter to colder bodies and not vice versa. This is because processes proceed in a certain direction and not the reverse direction. The second law is needed to determine the direction of spontaneous processes since the first law does not restrict direction. Two common statements of the second law are then presented: 1) It is impossible for a heat engine to receive heat from a single reservoir and produce work without rejecting some heat. 2) It is impossible to transfer heat from a cold to a hot body without external work. Examples of heat engines, refrigerators, and heat pumps are provided to illustrate these principles.
Combustion takes place when fuel, most commonly a fossil fuel, reacts with the oxygen in air to produce heat. The heat created by the burning of a fossil fuel is used in the operation of equipment such as boilers, furnaces, kilns, and engines.
Improved processes of light hydrocarbon separation from lngHasan Gumus
This document proposes two novel processes for separating light hydrocarbons like ethane from liquefied natural gas (LNG) using the cryogenic energy released during LNG regasification. The first process, called the "high pressure process", uses a demethanizer operating at 4.5 MPa to recover over 99.99% methane, then compresses the methane-rich natural gas. The second process, called the "low pressure process", uses a lower pressure demethanizer at 2.4 MPa and re-liquefies the methane-rich stream, pressurizing it with pumps instead of compressors. Both processes produce liquefied ethane and LPG at atmospheric pressure with acceptable power
This document presents research on developing an emissions prediction capability for use in conceptual aircraft engine design. A physics-based modeling approach was used consisting of 1D flow models of different combustor types, chemical reactor networks representing the combustor flowfields, and regression models. Models were developed for a single annular combustor, rich-quench-lean combustor, and lean-burn combustor. The models were implemented in NPSS and validated against test data. Regression models were also created to rapidly predict emissions for parametric studies of a CFM56-sized engine application. The new capability allows emissions predictions during early engine conceptual design when cycle parameters and architectures are varied.
This paper addresses the numerical simulation of
helically coiled closed loop pulsating heat pipe which is carried
in ANSYS Fluent. The values of thermal resistance for
constant heat fluxes vs. transient heat fluxes are analyzed.
Phase change visualization after the end of simulation is
carried out to observe the phenomenon in liquid at its
saturation temperature and pressure. Finally, helical heat
pipes are found to have thermal resistance less by 2.7K/W,
0.56 K/W, and 0.227 K/W for 8W, 40W and 80W heat inputs
than circular pipes. Helical heat pipes are found more efficient
than circular heat pipes.
The document analyzes heat transfer in the hot gas path of a gas turbine for a semi-closed oxy-combustion combined cycle (SCOC-CC) power plant under different operating conditions. It evaluates the convective and radiative heat transfer to the first row turbine vane using empirical correlations. The analysis shows that SCOC-CC with flue gas recirculation before condensation results in 20-30% higher heat transfer compared to recirculation after condensation. Increasing the pressure ratio from 17 to 40 at constant thermal power and turbine inlet temperature increases both convective and radiative heat transfer by about 10%. Chemiluminescence is found to have a negligible effect on heat transfer as the
This document presents a theoretical analysis of the performance of a vapor compression refrigeration system using different refrigerants: R-12, R134a, and R1234yf. The analysis uses a computational model based on the first law of thermodynamics to investigate the effects of evaporating temperature, subcooling, condenser temperature, and liquid-vapor heat exchanger effectiveness on the system's coefficient of performance and refrigerating capacity. The results show that R1234yf has the highest relative capacity increase with increased subcooling and the highest percentage increase in COP. R134a requires the most compressor work. R1234yf is identified as a promising alternative to R134a due to its low global warming potential
This document summarizes a study on the thermal performance of a shell and tube heat exchanger using nanofluids. Finite volume modeling was used to analyze heat transfer and flow characteristics. Various nanofluids including Ag, Al2O3, CuO, SiO2, and TiO2 suspensions in water were tested and compared to pure water. The objectives were to analyze temperature profiles, heat transfer coefficients, pressure drops, and effectiveness. Results showed nanofluids had higher overall temperatures indicating more heat transfer compared to water alone. This study analyzed the potential for nanofluids to enhance heat exchanger performance.
The student researchers measured the stack velocity at the University of Utah's High Temperature Water Plant and found it was higher than expected based on the reported firing rate. They determined the plant's method of calculating firing rate based only on hot water output underestimated the true rate by neglecting electric power generation and heat losses. The researchers concluded future stack velocity calculations should use the natural gas firing rate and that negative static pressure measurements are invalid. Improved measurement equipment and procedures were also recommended.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
This document describes a CFD analysis of fluid flow through tube banks in heat recovery steam generators (HRSGs). The authors developed a new procedure to define porous medium parameters like loss coefficients starting from 3D simulations of flow through tube banks. Both finned and bare tube banks were considered. The analysis was performed using the commercial CFD code Fluent to simulate flow through a single tube row and investigate the effects of Reynolds number, inlet yaw angle, and inlet pitch angle on pressure drop and outlet flow angles. Results were compared to experimental data for a real fired HRSG to validate the proposed porous media modeling approach.
Thermodynamic analysis of vapour compression refrigeration system using alte...IOSR Journals
This document discusses thermodynamic analysis of alternative refrigerants for vapor compression refrigeration systems. It aims to analyze the environmental and energy consumption impacts of various refrigerants. The document defines key terms like ozone depletion potential and global warming potential. It then analyzes several potential refrigerant alternatives to R22 and R134a like propane, isobutane, R410a, R407c, and a mixture called MO9. The thermodynamic properties of these refrigerants are obtained from software and their coefficients of performance are compared. The analysis found that MO9 shows potential as a suitable substitute for R134a in new and retrofit systems due to its performance and lower environmental impact.
This document discusses the thermal design of a simple boiler. It presents the calculation procedures for boiler design, focusing on heat transfer modes, heat and mass balances, and a worked example. The key points are:
- Heat transfer in boilers occurs via conduction, convection, and radiation. Conduction is not considered in simple calculations.
- Heat and mass balance equations relate the heat input from fuel to the heat output via steam as well as accounting for air and flue gas flows.
- A worked example calculates furnace conditions like flue gas temperature for a methane-fueled boiler, assuming radiation is the only heat transfer mode in the furnace. Tube bank calculations then determine the exit gas
This document summarizes an experiment investigating the behavior of a single fuel cell under different membrane electrode assemblies (MEAs) and fuels. Three MEAs using different catalysts were tested with hydrogen and formic acid as anode fuels and hydrogen, air, or water as cathode reactants. Constant base current with 10A pulses were applied to alleviate carbon monoxide poisoning on the anode. Results including polarization curves and potential/current oscillations are presented. The document also provides background on fuel cells and mechanisms of carbon monoxide poisoning.
The document summarizes an experimental investigation on the performance of an air conditioner using R32 refrigerant. It begins with an abstract describing the refrigerant comparison experiment conducted on a 1.5 ton capacity air conditioning system using R22, R134a, and R32. Performance parameters like coefficient of performance, mass flow rate, and power to the compressor were calculated. The results and simulations showed R32 to be the most efficient refrigerant for retrofitting air conditioning systems due to its lower global warming potential and atmospheric lifetime compared to R22.
The document summarizes a study analyzing the effect of heat transfer on the spring characteristics of hydro-pneumatic struts used in vehicle suspensions. A thermal time constant model was developed using real gas equations of state to model the irreversible heat transfer during compression and expansion cycles. The analysis defines a non-dimensional frequency parameter and shows through numerical simulation that this single parameter fully characterizes the energy dissipation and spring behavior of hydro-pneumatic springs regardless of other variables. The existence of this parameter is also determined analytically by modeling the hydro-pneumatic spring as an anelastic model.
The understanding of gas geochemical model to reduce the exploration uncertaintyRizal Abiyudo
The various fumaroles areas in the prospect are can be modelled by boiling depletion model and the relation between each of fumaroles. Geothermal waters would boil to create a first set of fumaroles and then the boiled, gas-depleted water outflows to the site of a second set of fumaroles where it boils again, creating fumaroles with gas-depleted chemistry.
Penga Ž, Tolj I, Barbir F, Computational fluid dynamics study of PEM fuel cel...Željko Penga
This computational fluid dynamics study examines PEM fuel cell performance under isothermal and non-uniform temperature boundary conditions. The study finds that implementing a non-uniform temperature profile along the cathode channel, as calculated from a Mollier h-u chart, results in close to 100% relative humidity without external humidification and improves fuel cell performance. The model polarization curve and relative humidity distribution agree well with experimental results. Different current collector materials and membrane thickness influence temperature and relative humidity distributions through their effects on thermal conductivity and water transport.
Exploring LPG Cylinders for Medical Oxygen - A Preliminary StudyVijay Sarathy
This document studies using LPG cylinders to supply medical oxygen in emergencies. It analyzes how long oxygen can be supplied from an LPG cylinder at flow rates of 0.5 and 2 liters per minute. The study finds the cylinder can supply oxygen at 0.5 liters/min for about 3 hours and at 2 liters/min for about 45 minutes before the pressure drops to 1 atmosphere. Governing equations for transient blowdown of the cylinder are derived in the appendices.
This document describes using Excel to optimize the thermal design of systems. It provides an example of optimizing the insulation thickness and pipe diameter of an insulated pipe to minimize costs. Excel is able to calculate the total cost as a function of diameter and use its Solver tool to iteratively find the optimal diameter that minimizes cost. This provides an effective way for students to learn thermal design optimization compared to analytical optimization, as it can handle multiple design factors and parameters. The document then presents another example of using this approach to optimize the diameters and insulation thicknesses of two sections of an air conditioning duct to minimize owning costs.
An experimental and kinetic study of syngas-air combustion at elevated temper...Saad Tanvir
This document describes an experimental study of syngas combustion at elevated temperatures and the effect of adding water. Laminar flame speeds of syngas/air mixtures were measured over a range of fuel compositions, equivalence ratios, and preheat temperatures. The measured flame speeds were compared to simulations from existing chemical kinetic models, showing reasonable agreement at room temperature but large discrepancies at higher temperatures. Water was added to two syngas fuels up to 40% by volume, and different effects on flame speed were observed depending on the fuel composition and water concentration, related to competing chemical and physical impacts of water addition.
Option C Nernst Equation, Voltaic Cell and Concentration CellLawrence kok
This document provides a tutorial on voltaic cells, the Nernst equation, and concentration cells. It discusses the basic components and workings of voltaic cells, including the conversion of chemical energy to electrical energy through redox reactions. Equations for cell potential (Ecell), standard electrode potential (E°), and the Nernst equation are presented. Examples of specific voltaic cells like Daniell cells and their cell potentials are provided. The relationships between Gibbs free energy (ΔG), equilibrium constant (Kc), and cell potential are also summarized.
The document discusses the second law of thermodynamics. It states that heat always flows spontaneously from hotter to colder bodies and not vice versa. This is because processes proceed in a certain direction and not the reverse direction. The second law is needed to determine the direction of spontaneous processes since the first law does not restrict direction. Two common statements of the second law are then presented: 1) It is impossible for a heat engine to receive heat from a single reservoir and produce work without rejecting some heat. 2) It is impossible to transfer heat from a cold to a hot body without external work. Examples of heat engines, refrigerators, and heat pumps are provided to illustrate these principles.
Combustion takes place when fuel, most commonly a fossil fuel, reacts with the oxygen in air to produce heat. The heat created by the burning of a fossil fuel is used in the operation of equipment such as boilers, furnaces, kilns, and engines.
1. The document provides a historical overview of water electrolysis from its discovery in 1789 to modern developments. Nicholson and Carlisle were the first to develop the technique in 1800, and by 1902 there were over 400 industrial units in operation.
2. It explains the theory behind water electrolysis, including the chemical reactions that produce hydrogen and oxygen, factors that determine minimum voltage requirements, and sources of inefficiency.
3. Various methods for producing hydrogen through water electrolysis are briefly described, including alkaline electrolysis, proton exchange membrane electrolysis, and producing hydrogen as a byproduct of chloralkali production. Advanced alkaline systems and high-pressure designs are highlighted.
The document summarizes key concepts from the second law of thermodynamics:
1) The first law has limitations in predicting whether an energy conversion is possible. The second law addresses this through statements by Kelvin-Planck and Clausius.
2) Kelvin-Planck's statement says a device cannot produce work without transferring heat from a hot reservoir and into a cold one. Clausius' statement says heat cannot spontaneously flow from cold to hot.
3) A reversible process can be reversed without leaving traces. Irreversible processes like friction cause a loss of useful energy.
4) The Carnot cycle uses reversible, isothermal and adiabatic processes between two reservoirs to produce work
There are three key types of fuel cells:
1) Solid oxide fuel cells (SOFCs) which have solid ceramic electrolytes and operate at high temperatures of 500-1000°C.
2) Proton exchange membrane fuel cells (PEMFCs) which use a polymer membrane and operate at lower temperatures of 60-100°C.
3) Phosphoric acid fuel cells (PAFCs) which use liquid phosphoric acid as the electrolyte and operate at 150-200°C.
SOFCs have the advantages of fuel flexibility, high efficiency, and no need for precious metal catalysts. However, challenges remain around durability at high operating temperatures.
When water flows through a pipe, pressure drop occurs due to energy losses from friction along the pipe walls. The pressure drop can be determined using equations that account for factors like flow rate, pipe diameter and roughness, fluid properties, and pipe length. Common methods for calculating pressure losses include using the Darcy-Weisbach equation with the Moody chart or Colebrook-White equation to find the friction factor, or using the Hazen-Williams equation which relates head loss to flow rate, pipe diameter, and a roughness coefficient. Minor losses from components like valves and fittings are also considered.
1) The document compares the performance of hydrogen fuel cells and direct methanol fuel cells through experimental testing.
2) Open circuit voltages for hydrogen, 3% methanol, 2% methanol, and 1% methanol fuel cells were measured as 0.635 V, 0.157 V, 0.102 V, and 0.092 V respectively.
3) Characteristic curves were generated for the different fuel cell types, and the coefficients determined provided a relationship between voltage and current.
The properties of a gas mixture depend on the properties of its individual components and their relative amounts. There are two ways to describe the composition of a mixture: molar analysis specifies the moles of each component, and gravimetric analysis specifies the mass of each component. For ideal gas mixtures, Dalton's law and Amagat's law can be used to determine pressure and volume behavior. For real gas mixtures, these laws are approximate and equations of state must be used. The properties of gas mixtures can be determined by weighted averages of the component properties.
1. Copper electrodeposition is commonly used in electronics manufacturing to plate wires, semiconductors, and printed circuit boards due to copper's thermal conductivity and corrosion resistance. Copper electrodeposition with organic additives allows bottom-up filling of high aspect ratio through-silicon vias.
2. The deposition rate is controlled through the use of levelers, suppressors, and accelerants. Levelers increase deposition in recessed areas, suppressors inhibit growth where adsorbed, and accelerants promote bottom-up filling by selectively removing suppressors from recessed areas.
3. An experiment deposited copper for 3,000 seconds from an acid copper plating solution onto a copper wire cathode, with and
IB Chemistry on Redox Design and Nernst EquationLawrence kok
The document describes experiments to investigate the effects of various factors on the emf and current of voltaic cells. It outlines procedures to study how the emf and current are affected by changing the metal pairs, concentrations of metal salts, surface areas of electrodes, temperature, and cation or anion sizes in the salt bridge. The goal is to better understand voltaic cells and the Nernst equation by systematically changing one factor at a time while keeping others constant.
Combustion second Erdi Karaçal Mechanical EngineerErdi Karaçal
This document contains a question from a midterm exam in mechanical engineering about determining the adiabatic flame temperature of a furnace operating with preheated air. The question provides the mass air-fuel ratio, temperatures of the entering air and fuel, and simplified thermodynamic properties. To solve it, the student sets up an energy balance equation accounting for the enthalpies of the products, fuel, and air. They plug in the known values and solve for the adiabatic flame temperature, determining it to be 2543 K. The student also notes they could solve similar problems in Excel by changing variables like the air-fuel ratio or heat capacities.
This document summarizes an article about electrocoagulation as a novel wastewater treatment method. Electrocoagulation uses sacrificial metal anodes that corrode when electric current is applied, producing metal cations that neutralize pollutants in water. It has advantages over other methods in providing coagulants without increasing water salinity. The document discusses the mechanisms of electrocoagulation including coagulant production, pollutant destabilization, and aggregation. Key factors like electrode material, current density, and operating conditions affect the process's performance in removing various pollutants from water.
This document discusses innovative techniques for teaching English in the digital age. It covers several techniques including blogs, social networking, wikis, massively multiplayer online games, and mobile phone assisted language learning. The key techniques allow for collaboration outside the classroom, interaction and communication in English, project-based learning, and accessibility of language lessons through mobile devices. Overall, the document advocates for English teachers to adopt these new digital techniques to engage students and meet the demands of a changing era.
The document defines combustion as a chemical process where a substance reacts with oxygen in air to produce heat and light. There are several types of combustion described, including spontaneous, rapid, complete, and incomplete combustion as well as explosions. Rapid combustion occurs when a substance burns quickly, producing heat and flame, often with the introduction of external heat. Incomplete combustion results in only partial burning of a fuel due to a lack of oxygen or low temperature, producing carbon monoxide. For combustion to occur, there must be a combustible substance, a supply of oxygen (air), and enough heat to raise the substance to its ignition temperature.
This document discusses key thermodynamic concepts related to combustion processes, including:
1) Heat of combustion, flame temperature, enthalpy of combustion systems, and equilibrium constants of combustion reactions are the major thermodynamic functions that influence fuel utilization.
2) Heat of combustion represents the potential heat of a fuel and can be used to calculate calorific value. Enthalpy is the heat content of a system at constant pressure.
3) Flame temperature depends on the fuel-oxidant mixture and ranges from theoretical to actual temperatures. The maximum adiabatic flame temperature occurs at slightly excess stoichiometry.
The document discusses gas mixtures and their properties. It defines mole fraction as the ratio of moles of a component to total moles of the mixture. Mass fraction is defined as the ratio of mass of a component to total mass of the mixture. Relations are derived to convert between mass fractions and mole fractions. Examples are provided to calculate mole fractions, average molar mass, and gas constant of mixtures given the masses or moles of individual components.
The document provides information on various aircraft engine cooling and exhaust systems. It discusses:
1. Air cooling systems which use fins and baffles to direct air flow over hot engine parts to absorb heat. Liquid cooling systems circulate coolant through engine jackets.
2. Exhaust systems include piping, mufflers and shrouds. Straight and short stack systems direct exhaust straight from cylinders. Collector systems combine exhaust from each cylinder.
3. Superchargers compress air to increase engine power and allow operation at high altitudes where air is less dense.
This document discusses reversible chemical reactions and chemical equilibrium. It defines key terms like activation energy, exothermic and endothermic reactions, and how factors like temperature, concentration, and catalysts affect the rate and direction of reversible reactions. Specifically, it explains that at chemical equilibrium, the rates of the forward and reverse reactions are equal and application of Le Chatelier's principle describes how the system responds to changes to relieve stress.
Abstract: Passive liquid water recovery from fuel cell effluent can be achieved by designing effective desiccant. Recovered water from desiccant is used for humidification of proton exchange membrane (PEM) to maintain at hydrated state. Proper membrane humidity is crucial to ensure optimal operation of a PEM to generate electricity. In this study a desiccant called water separator is designed, it works without consuming any external energy. The main aim of designing a component is to recover liquid water from hundred percent humidified air (vapour) which is coming out from cathode compartment of fuel stack and it is further used for humidifying the oxidant before entering the stack inlet. The self-sufficient water in vapour is investigated theoretically and experimentally. When the water separator temperature reached the critical point especially in large power applications or long time operation, recovered water was not sufficient for air humidification. On the contrary, it is sufficient while the temperature of water separator was below critical line. The temperature of separator is controlled by providing adequate heat transfer. The recovered amount of water by condensing the outlet gas or vapour to a proper temperature, easily satisfy required amount for humidification of oxidant at inlet of stack.
IRJET- Thermal Analysis of Corrugated Plate Heat Exchanger by using Ansys...IRJET Journal
This document discusses thermal analysis of a corrugated plate heat exchanger using ANSYS software through finite element analysis. It summarizes previous research on using nanofluids like Al2O3 in water to improve heat transfer in these types of heat exchangers. The document then outlines the methodology that will be used, which involves studying the corrugated plate heat exchanger with counterflow configuration and varying parameters like volume flow rate and corrugation angle to determine the optimal heat transfer results.
ENHANCEMENT OF THERMAL EFFICIENCY OF NANOFLUID FLOWS IN A FLAT SOLAR COLLECTO...Barhm Mohamad
Flat plate solar collector (FPSC) is popular for their low cost, simplicity, and ease of installation and operation. In this work, FPSC thermal performance was analyzed. It's compared to diamond/H2O nanofluids. The volume percentage and kind of nanoparticles are analyzed numerically that validation with experimental data available in the literature. The hot climate of Iraq is employed to approximate the model. The numerical study is performed by using ANSYS/FLUENT software to simulate the case study of problem. Due to less solar intensity after midday, temperatures reduction. The greatest collector thermal efficiency is 68.90% with 1% ND/water nanofluid, a 12.2% increase over pure water. The efficiency of 1% nanofluid is better than other concentrations because of a change in physical properties and an increase in thermal conductivity. Since the intensity of radiation affects the outlet temperature from the solar collector and there is a direct link between them, this increases the efficiency of the solar collector, especially around 12:30 pm at the optimum efficiency.
IRJET- A Review on Improvement of Heat Transfer Rate by Passive MethodsIRJET Journal
This document reviews research on improving heat transfer rates through passive methods. It discusses how adding nanoparticles to fluids to create nanofluids can improve heat transfer efficiency in heat exchangers. Several studies are summarized that found adding metal oxide nanoparticles like CuO and Al2O3 to water and ethylene glycol increased heat transfer rates compared to the base fluids alone. Corrugated plate heat exchangers in particular saw higher effectiveness with nanofluid use. However, more research is still needed to determine optimum nanoparticle concentrations for different nanofluids and applications. The aim of this review is to analyze how lower concentrations of Al2O3/water nanofluid could impact performance in plate heat exchangers.
This document provides a survey and analysis of fuel cell technology. It begins with an introduction to fuel cells and their benefits over traditional power sources. It then presents a mathematical model of a hydrogen fuel cell, including an equivalent circuit diagram and polarization curve. The model is expanded to account for varying parameters such as temperature, pressures, and gas flow rates. The model equations calculate values like open circuit voltage and exchange current based on these parameters. Finally, the document demonstrates how to extract specific fuel cell stack parameters, such as number of cells and nominal air flow rate, from a manufacturer's datasheet.
Comparative Study of ECONOMISER Using the CFD Analysis IJMER
This paper presents a simulation of the economizer zone, which allowsstudying the flow
patterns developed in the fluid, while it flows along the length of the economizer. The past failure
details revelsthat erosion is more in U-bend areas of Economizer Unit because of increase in flue gas
velocity near these bends. But it isobserved that the velocity of flue gases surprisingly increases near
the lower bends as compared to upper ones. The model issolved using conventional CFD techniques by
FLUENT software. In which the individual tubes are treated as sub-gridfeatures. A geometrical model
is used to describe the multiplicity of heat-exchanging structures and the interconnectionsamong them.
The Computational Fluid Dynamics (CFD) approach is utilised for the creation of a three-dimensional
modelof the economizer coil of single column tube. With equilibrium assumption applied for
description of the system chemistry. The flue gastemperature, pressure and velocity field of fluid flow
within an economizer tube using the actual bounda
applications in energy and combustion sciencegaticavaz25
Mejora de la hidratación del agua en una celda de combustible de membrana de intercambio de protones
enfriada por aire mediante un campo de flujo ranurado cónico escalonado. La pila de combustible de membrana de intercambio de protones refrigerada por aire (AC-PEMFC) se considera ampliamente como una fuente de
energía prometedora para vehículos aéreos no tripulados (UAV) debido a sus ventajas como la alta densidad de energía, el corto tiempo de
reabastecimiento de combustible y el sistema auxiliar simple. Sin embargo, el rendimiento de AC-PEMFC no es satisfactorio debido a la pobre
hidratación de la membrana causada por el gran suministro de aire para la demanda de disipación de calor. Este estudio propone una configuración
de campo de flujo ranurado cónico escalonado (STSF) para abordar este problema, que tiene un área de contacto más alta entre el flujo de aire y la
placa bipolar mediante la disposición de secciones cónicas y ranuradas en los canales a lo largo de la dirección del flujo de aire, con el objetivo de
mejorar el efecto de enfriamiento. y mejorar la hidratación del agua de la membrana. Utilizando un modelo no isotérmico multifásico tridimensional
(3D) verificado con datos experimentales, se encontró que la configuración STSF reduce la temperatura interna de la celda en aproximadamente
14,2 a 28,3 K y aumenta el contenido de agua en la membrana en aproximadamente 14,2 a 28,3 K. 35,1–85,7 % en comparación con los canales
directos tradicionales. Además, la configuración STSF puede mejorar la transferencia de masa al inducir el flujo cruzado, reduciendo las pérdidas
de concentración, lo que tiene más efecto para los UAV que trabajan a gran altitud. Además, las secciones ranuradas redujeron el volumen y el peso
de las placas bipolares, contribuyendo a una mejora adicional de la densidad de potencia. Finalmente, se comparó la caída de presión dentro de los
canales de flujo y la potencia neta. Debido al aumento del área de contacto entre el flujo de aire de refrigeración y las placas bipolares, la configuración
STSF inevitablemente da como resultado una mayor caída de presión dentro de los canales, pero la potencia neta de PEMFC con STSF aún aumentó
en condiciones severas en 0,080 W.
Application of Parabolic Trough Collectorfor Reduction of Pressure Drop in Oi...IJMER
Pipelines are the least expensive and most effective method for the oil transportation.
Due to high viscosity of crude oil, the pressure drop and pumping power requirements are very high.
So it is necessary to bring down the viscosity of crude oil. Heated pipelines are used reduce the oil
viscosity by increasing the oil temperature. Electrical heating and direct flame heating are the common
method used for heating the oil pipeline. In this work, a new application of Parabolic Trough Collector
in the field of oil pipeline transport is introduced for reducing pressure drop in oil pipelines. Oil
pipeline is heated by applying concentrated solar radiation on the pipe surface using a Parabolic
Trough Collector in which the oil pipeline acts as the absorber pipe. 3-D steady state analysis is
carried out on a heated oil pipeline using commercial CFD software package ANSYS Fluent 14.5. In
this work an effort is made to investigate the effect of concentrated solar radiation for reducing
pressure drop in the oil pipeline. The results from the numerical analysis shows that the pressure drop
in oil pipeline is get reduced by heating the pipe line using concentrated solar radiation. From this
work, the application of PTC in oil pipeline transportation is justified.
Characterization of a flat plate solar water heating system using different n...Barhm Mohamad
Flat-plate solar collectors (FPSCs) are the most effective and environmentally friendly heating systems available. They are frequently used to convert solar radiation into usable heat for a variety of thermal applications. Because of their superior thermo-physical features, the use of Nano-fluids in FPSCs is a useful technique to improve FPSC performance. Nano-fluids are advanced colloidal suspensions containing Nano-sized particles that have been researched over the last two decades and identified a fluid composed of strong nanoparticles with a diameter of smaller than (100 nm). These micro-particles aid in improving the thermal conductivity and convective heat transfer of liquids when mixed with the base fluid. The current study provides an in-depth review of the scientific advances in the field of Nano-fluids on flat-plate solar collectors. Previous research on the usage of Nano-fluids in FPSCs shows that Nano-fluids can be used successfully to improve the efficiency of flat-plate collectors. Though several Nano-fluids have been reviewed as solar collector operatin fluids. Nano-fluids have greater pressure drops than liquids, and their pressure drops andhence pumping power rise as the volume flow rate increases. Additionally, the article discusses the concept of Nano-fluids, the different forms of nanoparticles, the methods for preparing Nano-fluids, and their thermos-physical properties. The article concludes with a few observations and suggestions on the usage of Nano-fluids in flat-plate solar collectors. This article summarizes the numerous research studies conducted in this region, which may prove useful for future experimental studies.
tf.ugm.ac.id_astechnova_proceeding_Vol3No2_Astechnova_2014_2_04Totok R Biyanto
1. The document describes optimizing the cleaning schedule of heat exchanger networks (HEN) using particle swarm optimization (PSO).
2. It involves simulating the HEN using mass and energy balance equations, modeling fouling behavior empirically, and using PSO to optimize the interval of cleaning schedules.
3. The optimization achieved $1.236 million in savings, or 23% of the maximum potential savings, by cleaning the HEN optimally over a 44-month period.
For the tropical surface ocean waters being the largest thermal
solar collectors and reservoirs in the planet, a solution is
proposed for inexhaustible supply of freshwater by combining
two renewable energy routes through a hybrid offshore
energy farm, ocean thermal energy conversion, and
offshore wind power.
Heat Transfer Enhancement Using Aluminium Oxide Nanofluid: Effect of the Base...CSCJournals
The flow and heat transfer is an important phenomenon in engineering systems due to its wide application in electronic cooling, heat exchangers, double pane windows etc.. The enhancement of heat transfer in these systems is an essential topic from an energy saving perspective. The lower heat transfer performance when conventional fluids, such as water, engine oil and ethylene glycol are used hinders improvements in performance and a consequent reduction in the size of such systems. The use of solid particles as an additive suspended into the base fluid is a technique for heat transfer enhancement. Therefore, the heat transfer enhancement in a horizontal circular tube that is maintained at a constant temperature under laminar regime has been investigated numerically. A computational code applied to the problem by use of the finite volume method was developed. Nanofluid was made by dispersion of Al2O3 nanoparticles in pur water and ethylene glycol. Results illustrate that the suspended nanoparticles increase the heat transfer with an increase in the nanoparticles volume fraction and for a considered range of Reynolds numbers. And in other hand, the heat transfer is very sensitive to the base fluid.
Hair Pin Heat Exchanger Layered with Graphene in Tube Side Using Al2O3 as Nan...IRJET Journal
This document discusses a computational fluid dynamics (CFD) analysis of a hairpin heat exchanger layered with graphene. The study aims to evaluate heat transfer performance of a hairpin heat exchanger with a graphene layer compared to one without a graphene layer. Aluminum oxide nanofluid is used as the cold fluid in the shell side. CFD simulations are performed using ANSYS Fluent to analyze heat flux, convective heat transfer coefficients, and pressure drop for both designs under varying hot fluid flow rates. Results show that the heat exchanger with graphene has higher heat flux and convective heat transfer coefficients compared to the design without graphene. Specifically, the convective heat transfer coefficient for the hot fluid reaches 1117 W
A REVIEW PAPER ON ANALYSIS OF AUTOMOBILE RADIATORijsrd.com
An Automotive engine cooling system takes out of excess heat produced during engine operation. An automobile cooling system regulates engine surface temperature for engine optimum efficiency. Recent advancement and development in engine for power forced engine cooling system to develop new strategies to improve its performance efficiency. Also to reduce fuel consumption along with controlling engine emission to mitigate environmental pollution norms. This paper throws light on parameters which influence radiator performance along with reviews some of the conventional and modern approaches to enhance radiator performance. This review paper Focus on the various research papers regarding experimental, CFD and Numerical analysis to improving automobile radiator efficiency.
The document describes a process design for a proton exchange membrane (PEM) fuel cell power plant that produces hydrogen from heptane to deliver electricity to a 300 office building. Simulations were run using ASPEN software to model and optimize the plant design, which includes an auto-reformer, water-gas shift reactors, a preferential oxidation reactor, and heat exchangers. An economic analysis was conducted to determine the total capital costs and profitability of the plant over 25 years. The current plant design is not able to fully power the processing needs and falls short of the electrical demand, requiring further optimization to improve efficiency and meet all power requirements.
Thermal Performance of Diffusion Bonded Compact Heat Exchangers using Al2O3 W...ijtsrd
The value of compact heat exchangers CHEs has been recognised in aerospace, automotive, gas turbine power station, and other industries for the last 50 years or more. This is attributed to many reasons, for example manufacturing restrictions, often high efficiency requirements, low cost, and the use of air or gas as one of the fluids in the exchanger. Together with new and improved forms of CHEs, these advances are an excellent opportunity to bring compact heat exchangers into the process industry, particularly where saving energy is an essential target. High energy prices are also encouraging companies to use energy saving strategies at their plants as much as possible. During decades, attempts to increase heat transfer, decrease heat transfer times and eventually improve energy efficiency have been made. Recent advancements in nanotechnology have facilitated the creation of a new type of liquids called nanofluids. Most theoretical and computational experiments have shown that nanofluids demonstrate an improved coefficient of heat transfer relative to their base fluid. This CFD research explores the impact on the performance of straight square compact heat exchangers from Al2O3 water nanofluid flow. The Al2O3 water nanofluids with three weight fractions of nanoparticles i.e. 0.4, 0.8, and 1.2 percent were used. The effect of nanofluid were measured and observed to influence the heat transfer and flow of fluids in a straight square compact heat exchanger. The following conclusions can be drawn based on the provided results, the thermal conductance are approximately 29 higher and the heat transfer are approximately 35 higher in comparison with the conventional fluid i.e. water. Vishal Deshmukh | Prof. Animesh Singhai "Thermal Performance of Diffusion-Bonded Compact Heat Exchangers using Al2O3/Water Nanofluid" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-6 , October 2020, URL: https://www.ijtsrd.com/papers/ijtsrd33508.pdf Paper Url: https://www.ijtsrd.com/engineering/mechanical-engineering/33508/thermal-performance-of-diffusionbonded-compact-heat-exchangers-using-al2o3water-nanofluid/vishal-deshmukh
iaetsd Nanofluid heat transfer a reviewIaetsd Iaetsd
This document summarizes research on using nanofluids to enhance heat transfer. Nanofluids are fluids containing nanosized particles that can increase the thermal conductivity of the base fluid. Several studies have found that nanofluids can increase heat transfer rates compared to the base fluid alone. The amount of heat transfer enhancement depends on factors like the nanoparticle material, size, concentration, and whether the fluid flow is laminar or turbulent. Nanofluids show potential for applications like cooling engines, electronics, and nuclear systems. However, issues like long-term stability, increased pumping power needs, and high production costs still need to be addressed for more widespread use of nanofluids in industries.
Improving the Cooling Performance of Automobile Radiator with Ethylene Glycol...IRJET Journal
This document summarizes research on improving the cooling performance of an automobile radiator using ethylene glycol-water based ZrO2 and Al2O3 nanofluids. Key findings include:
1) Experiments were conducted using different volume concentrations of ZrO2 and Al2O3 nanofluids at varying flow rates and a constant inlet temperature of 90°C.
2) Results showed that heat transfer coefficients and Nusselt numbers increased with higher nanoparticle concentrations and flow rates for both nanofluids. ZrO2 nanofluid performed better than Al2O3 nanofluid.
3) Outlet temperatures of the radiator decreased more when using nanofluids compared to the
IRJET- Experimental Research of Heat Transfer using Nano – Fluid in RadiatorIRJET Journal
This document presents an experimental study on using nanofluids to enhance heat transfer in a car radiator. Aluminum oxide nanoparticles were added to water at concentrations from 0.025% to 0.1% by volume to create nanofluids. The nanofluids and water were circulated through a test radiator at flow rates from 50 to 60 liters per minute. Results showed that heat transfer performance of the radiator increased with both higher nanoparticle concentrations and higher flow rates. The maximum 36% increase in heat transfer occurred with the highest 0.1% nanoparticle concentration nanofluid. Nusselt number, a measure of heat transfer, increased with heat transfer coefficient but did not significantly change with nanoparticle concentration
Study on Coupling Model of Methanol Steam Reforming and Simultaneous Hydrogen...IOSR Journals
1) A simplified mechanistic model was developed for coupling methanol steam reforming and hydrogen combustion in microchannels of a parallel plate reactor. The reforming reaction is endothermic and requires heat, which is provided by the exothermic hydrogen combustion reaction in an adjacent channel.
2) Kinetic expressions were used to model the reforming and combustion reactions. MATLAB simulations were performed to analyze parameters like temperature, velocity and conversion. Operative diagrams showed the temperature and velocities required for complete methanol conversion.
3) Efficiency curves were generated based on hydrogen produced versus consumed. With a molar ratio of 0.9664, the maximum efficiency was 86.8%, indicating over 80% efficiency is achievable via coupling of
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PASSIVE LIQUID WATER RECOVERY FROM FUEL CELL EXHAUST
1. International Journal of Recent Research in Civil and Mechanical Engineering (IJRRCME)
Vol. 1, Issue 1, pp: (18-23), Month: April 2014 - September 2014, Available at: www.paperpublications.org
Page | 18
Paper Publications
PASSIVE LIQUID WATER RECOVERY FROM FUEL CELL EXHAUST
Anand N N1, Dr.M.Raja2, Dr.T.Rangaswamy3
1Dept. of Mechanical Engineering, Govt. Engineering College Hassan, VTU, India
2General Manager, TATA MOTORS Research and Development Centre Bangalore, India,
3Professor and HOD, Dept. of Mechanical Engineering, Govt. Engineering College Hassan, VTU, India
Abstract: Passive liquid water recovery from fuel cell effluent can be achieved by designing effective desiccant. Recovered water from desiccant is used for humidification of proton exchange membrane (PEM) to maintain at hydrated state. Proper membrane humidity is crucial to ensure optimal operation of a PEM to generate electricity. In this study a desiccant called water separator is designed, it works without consuming any external energy. The main aim of designing a component is to recover liquid water from hundred percent humidified air (vapour) which is coming out from cathode compartment of fuel stack and it is further used for humidifying the oxidant before entering the stack inlet. The self-sufficient water in vapour is investigated theoretically and experimentally. When the water separator temperature reached the critical point especially in large power applications or long time operation, recovered water was not sufficient for air humidification. On the contrary, it is sufficient while the temperature of water separator was below critical line. The temperature of separator is controlled by providing adequate heat transfer. The recovered amount of water by condensing the outlet gas or vapour to a proper temperature, easily satisfy required amount for humidification of oxidant at inlet of stack.
Keywords: cell stack, Proton exchange membrane, Humidification, Vapour, Liquid water recovery.
I. INTRODUCTION
In hybrid vehicles the proton exchange membrane fuel cell (PEMFC) is used to convert hydrogen and oxygen to electricity from an electrochemical reaction, in which fuels combines to form water as a by-product. The fuel supplies to PEMFC should be humidified to get efficient performance
In this work an attempt have made for Water recovery and, in particular, to Water recovery for use in high temperature fuel cell systems. Reactant gases supplied to the fuel cell, and in particular, the reactant fuel gas supplied to the anode, must be sufficiently humidified to maintain a desired steam to carbon ratio in the fuel for proper and efficient fuel cell operation and to prevent carbon deposition in the fuel cell. The amount of Water consumed by fuel cell system for humidifying reactant gases is usually significant and requires a continuous supply of Water to the fuel cell system.
With rising prices of Hydrocarbon Fuels and the increasing costs of the environmental impact due to emissions it has become imperative to identify alternative energy sources. At present there are multiple competing sources of energy for automotive applications and Hydrogen is one of the most promising sources. In this regard there are two competing technologies as well.
Internal Combustion
Fuel Cell
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Using Hydrogen in a regular Internal Combustion Engine is not easy, for instance, the flame velocity of Hydrogen is 300 m/s as opposed to 29 m/s of Petrol (Gasoline). In addition an enormous amount of work has already gone in to Fuel Cell technology development since the 1960s. If Hydrogen is indeed going to be the future fuel, Fuel Cells are the quickest way of creating the impetus for the creation of a Hydrogen infrastructure. With this in view, TATA Motors Limited (TML) decided to indigenously develop a Fuel Cell Bus. In order to complement the wide ranging experience of TATA Motors in Buses, for design of systems with Hydrogen and for overall consulting on Hydrogen Handling.
The energy conversion used in fuel cell technology provides several advantages over the combustion of fossil fuels. First, the only emission that arises directly from the fuel cell is pure water. Second, most fuel cells have higher design and off- design efficiencies than conventional energy conversion processes, which rely on combustion. Finally, the technology can be easily Additional emissions may arise from the production of hydrogen if the primary energy source is a fossil fuel. However, even with these considerations, fuel cells typically have lower emissions than traditional energy systems.
At the date of writing of this document it is envisaged that the Fuel Cell Stack will be procured from Ballard™, Inc of Canada. This Fuel Cell Stack has specifications supplied by Ballard and this specifications document (MK902 Fuel Cell Module Assembly – Product Assembly”) is provided as an addendum to this document. The Balance of Plant exists to take care of the Fuel Cell Stack. This is the focus of the Design Work being undertaken by TML.
II. THEORETICAL SCHEME
According to thermodynamics when the temperature of liquid at a specified pressure is raised to saturation temperature Tsat at that pressure, boiling occurs. Vice versa, when the temperature of a vapour is lowered to Tsat, condensation occurs. In this study the rates of heat transfer at the time of vapour-to-liquid phase transformations has been studied. Although condensation contests some unique features, like convection heat transfer since they involve fluid motion. condensation differ from other forms of convection in that they depend on the latent heat of vaporization hfg of the fluid and the surface tension at the liquid–vapour interface, in addition to the properties of the fluid in each phase. Noting that under equilibrium conditions the temperature remains constant during a phase-change process at a fixed pressure, large amounts of heat (due to the large latent heat of vaporization released or absorbed) can be transferred during condensation essentially at constant temperature. In practice, however, it is necessary to maintain some difference between the surface temperature Ts and Tsat for effective heat transfer. Heat transfer coefficients h associated with condensation are typically much higher than those encountered in other forms of convection processes that involve a single phase. Here the physical mechanism of film condensation and discuss condensation heat transfer in geometrical arrangement and orientation. Finally, we introduce drop wise condensation and discuss ways of maintaining it. The theoretical calculations are carried out by assuming, process of condensation is occurring over number of components inside the water separator and heat transfer rate is increased by providing water jacket.
Fig. 1 Schematic of water Separator Fixed to Stack
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Fig.2 Model of Water Separator
Before the condensation the mass of liquid particles as to be find out in the air coming out of stack
III. THEORETICAL SEPARATION METHOD
This is a constant volume process. Since the work is zero, the first law reduces to
Q=u2-u1=mo2cvo2 (T2-T1) +mn2cvn2 (T2-T1) +(m2u2) v+ (m2u2) L-(m1u1) v (1)
Where “m” and “u” are mass and internal energy of oxygen, nitrogen and water vapour in the system, oxygen and nitrogen are highest compositions in air. The mass of nitrogen can be calculated using ideal gas equation of state. The mass flow rate of air and water in the inlet could be expressed as.
m. a= (2)
m. w, add,air = * (3)
Where and m. a were the molecular weight and mass flow rate of the air, respectively, was the stoichiometry, n was the cell number, I was the working current, and F was the Faraday constant. Pin and PinH2o were the inlet total pressure and inlet water vapour Partial pressure, respectively, was the saturated water vapour pressure with respect to the inlet temperature , RH was the relative humidity, was the water molecular weight. The mass of nitrogen can be calculated using ideal gas equation of state
m. n = (4)
m. n is mass flow rate of nitrogen in vapour ,„Ps‟ is saturation pressure of water vapour, „v‟ is velocity, „R „is real gas constant and‟ T‟ is temperature of vapour.
ps= 610.78**17.2694 (5)
„t‟ is the vapour temperature at inlet.
The flow of vapour inside the tube is turbulent, because of some disturbance inside the tube At a Reynolds number of about 1800, the condensate flow becomes turbulent. Several empirical relations of varying degrees of complexity are proposed for the heat transfer coefficient for turbulent flow. Again assuming v<<l for simplicity, Labuntsov proposed the following relation for the turbulent flow of condensate on vertical plates.
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hvertical,turbulent= (6)
Where,
Rvertical,turbulent = (7)
Then the heat transfer rate in the vertical components can be calculated by knowing heat transfer surface area
Q = hA(Tsat-Ts) (8)
Totally the mass of condensed or separated water can be calculated by
m.condensation= nfg/Q (9)
Where m.condensation is mass of water is condensed or separated, hfg is latent heat of vaporization and Q is the total rate of heat transfer by separator.
IV. EXPERIMENTATION
Experiment setup used as per below shown process and instrumentation diagram to carry out the practical testing. Fig 3 is the Process and Instrumentation Diagram with water separator system, the operating conditions are varies according to the various components, two partitions are made A and B, and same operating conditions are mentioned below.
A. Conditions
1. Air inlet Temp- 20 to 40 deg c
2. Air Humidity – depends on atmosphere
B. Conditions
1. Air inlet Temp- 40 to 180 deg c
2. Air Humidity – 100% humidified
3. Air mass flow rate- 0 to 120 gm/sec
Fig. 3 P&ID of water separator
A - Boundary conditions are atmospheric operating conditions
B – Once Air compressor sucks air from atmosphere air need to be compressed up to 2 bar pressure under the flow rate of 120 gm/sec and Temperature of compressed air Maximum up to 180 oc.
The existing design for the fuel cell test stand was designed to control the operation of fuel cell stacks. All components in the system were selected based on mass flow rates corresponding to power, pressure ratings of at least 400 kPa, and operating temperatures of at least 100oC. The test stand consisted of the following systems; air and hydrogen flow controllers, air and hydrogen heaters, liquid water injection humidifiers for air and hydrogen, water separator, coolant
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water circulating loops with pump, and measurement and control devices. The design and configuration of this system did provide adequate humidification to operate a fuel cell stack by collecting water with the help of water separator.
In order to investigate the liquid water recovery amount, four cases are studied by experiment, As shown in Table 1, the investigation of water recovery amount from the stack by separator as done in four different cases . The fuel cell stack was reactivated with increasing current on the stack with fully humidified H2/air for about 8 h before the polarization curves were recorded. After the activation process, polarization curve was recorded to evaluate the initial performance of the fuel cell stack. The detailed experimental conditions of the fuel cell stack are shown in Table 1.
Fig. 4 Schematic diagram of the test system for PEM fuel cell stack.
Table 1: Experimental readings Fig. 5. Water recovery amount
The Fig. 5 displayed time evolutions of liquid water recovered from the outlet vapour at exit of stack. It can be seen, that amount of water increased almost linearly with the time for all cases. Where the maximum running condition of stack is at 440amps, It will be maximum when it is working at a condition of peak load. Moreover, the generation of water was about 4.4gm/sec is achieved by this separator experimentally and 3.9 gm/sec analytically. Consequently, most of liquid water could be separated from the higher temperature gas in the condenser when the gas was cooled by providing water jacket for efficient separation of liquid water from the outlet gases. On the other hand, as can be seen in Fig 6, water separation rate decreased with the drop in the gas temperature and mass flow rate in the condenser. At the end of the condensing process, there was almost no water could be separated from the gas.
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. Fig. 6 Comparisons of the Analytical and experimental data
V. CONCLUSION
The fuel cell system requires humid air to facilitate the chemical reaction. The reactants in the fuel cell are humidified to keep polymer membrane wet and saturated with the Water for sustained ionic conductivity. At Present Fuel Cell Power system is not implemented with water separator, the exhaust water vapour is vented directly to the atmosphere. In this work liquid water is separated from the exhaust water vapour and it is used for humidification in the fuel cell power system. Sufficient water can be recovered by condensing the high temperature exhaust of the stack, and the amount of recovered water can satisfy the humidification demand in the cathode easily by applying a high heat removal ability separator. In this work an economic and convenient way to a realize the water balance in the fuel cell, water in vapour can be separated for humidifying the inlet gas sufficiently. As a consequence, this method can be easily used for the air self humidification in large power and long time operating fuel cell stacks.
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