Hydrogen owing to its abundance in universe is replacing the fossil energy sources like coal, petroleum etc that are being depleted speedily. Hydrogen is energetic per unit mass of fuel burned i.e. 120.7 kJ/g compared to any type of fuel (Haryanto et al., 2005). Moreover, fossil sources produce pollutants like COx, NOx, SOx, CxHx, soot, ash and other organic compounds to the atmosphere on burning that adds to the global warming. Hydrogen was discovered by Henry Cavendish in 1766 and named in 1783 by Antoine Lavoisier with origin of name from words "hydro" and "genes" meaning "water" and "generator" because it burns to produce water only (Song, 2003). It is present in combination to the other elements like with oxygen in water, with carbon in hydrocarbons and need to be extracted. Other sources can be a variety of fossil and non-fossil resources like coal, natural gas, liquefied petroleum gas, diesel, biomass and its derived fuels such as methanol, ethanol, and biodiesel (Haryanto et al., 2005).
Hydrogen fuel cells are used to provide energy for transport and mobile applications in form of electricity directly from chemical energy to power laptops, vehicles or other applications where cost is not a big issue like space technology, submarines etc. They are energy efficient, clean, fuel flexible, not noisy, vibrations are not there and they have smooth operation resulting in comfort of the users (Silveira et al., 2009). Moreover, fuel used in fuel cells has greater energy density than batteries (Park et al., 2007) which is required for portable applications like laptops, medical and telecommunication devices and for military applications like remote sensors (<20W), silent power generation and battery recharging (200W- 2kW) and mobil...
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...ry method of removal or addition of convective heat). So, the final "success" of this technology will depend largely on modeling, understanding and control of temperature excursions.
In this work, ethanol is steam reformed in a non-isothermal tubular reactor which is coupled with ethanol combustion in recuperative way where heat is transferred from the exothermic reaction zone through the walls of channel. A full three-dimensional geometry is modeled consisting of co-flow and counter-flow configurations. The authors have studied the design configurations based on ethanol steam reforming through one dimensional models and experiments (Table 2) but a 3-D model was required in order to fully explore the various transport processes in the configurations and study the variations in the reactor performance due to hydrodynamics and heat and mass transfer characteristics.
In conclusion, hydrogen is one of the many important elements on the periodic table. Hydrogen makes up 2/3 of water, 1/4 of the air, 0.15% of the earth's crust, metal hydrides found in some batteries, and in many carbohydrates we eat. Hydrogen serves as many sources of fuel, such as fuel for most starts to produce energy or for rockets. Due to how useful this element is, hydrogen has received a lot of acknowledgement throughout history.
Fuel Cells” the author states, “ Sir William Grove discovered that it may be possible to generate electricity by reversing the electrolysis of water.” But it wasn’t until 1889 when two researchers looked further into Sir William Grove’s studies. In the article “History of Fuel Cells” the author says, “Charles Langer and Ludwig Mond, coined the term ‘fuel cell’ as they were trying to engineer the first practical fuel cell using air and coal gas.” After Langer and Mond’s discovery Frances Bacon developed what was close to being the first fuel cell in 1959. In the article “History of Fuel Cells” the author declares, “It was not until 1959 that Bacon and company first demonstrated a practical five-kilowatt fuel cell system.” In the late 1950’s NASA began experimenting with fuel cells by using them for compact electricity generators. Fuel cells have now supplied electricity for many space missions. In the article “History of Fuel Cells” the author states, “In more recent decades, a number of manufacturers - including major auto makers - and various federal agencies have supported ongoing research into the development of fuel cell technology for use in fuel cell vehicles (FCV) and other applications. Fuel cell energy is now expected to replace traditional power sources in coming years - from micro fuel cells to be used in cell phones to high-powered fuel cells for stock car racing.”
Hydrogen is a diatomic element that is in a gaseous form at room temperature. Its most identifying characteristic is the fact that it is highly explosive. It is the lightest element in the world, and has a lifting power of 8% more than that of helium. Hydrogen was used in airships and zeppelins for more than 20 years during the beginning of the 20th century. This practice stopped abruptly after the German airship Hindenburg disaster over New Jersey. It is used in fuel cells to create electricity, and to power cars and planes. Liquid hydrogen is mixed with liquid oxygen to form a cryogenic liquid that is burnt in Solid Rocket Boosters to power the space shuttle. Hydrogen is used to fill weather balloons because of its superb lifting power.
With alternate energy sources becoming more and more necessary and desirable, not only does the future hold promise for a cleaner environment, but many companies and entrepreneurs have the potential to make billions of dollars should hydrogen, nuclear, or some other alternative source of energy become implemented worldwide.
The thermal performance of a heat exchanger depends upon various parameters like inlet temperature of a hot fluid, type of hot fluid, type of cold fluid, shape of baffles, material of baffles, baffles angle and property of ribs. Basically fluid flow and heat transfer characteristics are largely depends upon the Reynolds number (Re). Reynolds number is basically the ratio of inertia force to viscous force. Re is only the factor by which we can decide whether the fluid is laminar or turbulent in shell and tube type of heat exchanger. Heat exchanger is an adiabatic device in which heat is transferred from one fluid to another fluid across a plate surface. In this paper we have introduced some special type of triangular baffles with rectangular channels. The purpose
Double pipe heat exchanger is used in chemical industry. When to construct this type of heat exchanger, the size of material that is considered since it affected the overall heat transfer. Basically the heat exchanger has two types that are parallel flow heat exchanger, counter flow heat exchanger and efficiency of counter flow heat exchanger is high than the parallel flow heat exchanger. So it is widely used. After few years of research the fins has introduce in heat exchangers for improve performance.
The economics of industrial production, limitation of global energy supply, and the realities of environmental conservation are an enduring concern for all industries. Wherever you turn, there’s another entreaty to save energy, reduce carbon emissions and protect the environment for posterity. Pinch analysis is a tools used to design a heat exchanger networks (HEN) that reduce the energy usage. This paper will be about brief introduction for the pinch analysis, application of the second law of thermodynamics in design heat exchanger network
A fuel Cell is an Electrochemical Device which generates electrical power continuously as a gaseous fuel is electrochemically burnt in a continuous manner.
Hydrogen is one of the most abundant elements on the earth. It can be found in the oceans as well as the atmosphere. Over the last few years, talk about the future of hydrogen power has grown from a whisper to a roar. The use of hydrogen is not just the burning of the gas, but of its use in a fuel cell. Fuel cells might be the device that causes the extinction of the internal combustion engine. A fuel cell is a device that produces electricity from a fuel and an oxidizer, a substance that combines with the fuel. The fuel and oxidizer react chemically at two separate electrodes to produce the direct electric current; These cells use hydrogen as the fuel and oxygen as the oxidizer. Hydrogen power could be the silver bullet to the current and future energy situation.
The swirl of flow helps decrease the boundary layer thickness of the hot air flow and increase residence time of hot air in the inner tube. The enhancement efficiency and Nusselt number increase with decrease in pitch of wire. The most common type of heat exchanger in industrial applications is the shell-and-tube heat exchanger, shown in Figure. Shell-and-tube heat exchangers contain a large number of tubes (sometimes several hundred) packed in a shell with their axes parallel to that of the shell. Heat transfer takes place as one fluid flows inside the tubes while the other fluid flows outside the tubes through the shell. As the turbulence is increase rate of heat transfer between system to surrounding is increases. Often
Enclosures are frequently encountered in practice, and heat transfer through them is of practical interest. Heat transfer in enclosed spaces is complicated by the fact that fluid in the enclosure, in general, does not remain stationary. The fluid adjacent to the hotter surface rises and the fluid adjacent to the cooler one falls, setting off a rotationary motion within the enclosure that enhances heat transfer through the
When gases flow alongside both sides, the total heat-transfer coefficient is very deficient, and the finest solution is to make use of heat-pipes as intermediate heat-transfer devices among the gas streams; or else, finned split up surfaces, or, better, direct contact through a solid regain, are used.
In this present work the CFD simulation of heat sink is carried out for two different velocity magnitudes. The heat sink is modelled as a combination of Copper and Aluminium materials. The base of the heat sink is taken as Copper and the fins are modelled as Aluminium. A conjugate heat transfer analysis is carried out for this fluid – structure case. Two cases are simulated with a velocity of flow as 4 m/s and 10 m/s. The base of the heat sink is given with heat flux boundary. The results of both the scenarios are showing good coherence with the physical phenomenon. As velocity increases the temperature of the heat sink decreases, so the heat generated in the heat sink will become less. The rate of heat transfer will be
Boiling is the most efficient forms of heat transfer since large values of heat flux can be realized at small value of temperature difference between a heated surface and working fluid. For conventional engineering applications the temperature difference is in the range of 5 ~ 15 K, which can cause heat flux values typically exceeding 10 W/cm2 (and in some reports reaching values as high as 1 kW/cm2). This is 100 ~ 1000 times higher than other forms of heat transfer (such as natural convection). These high values of boiling heat flux are achieved by leveraging the large values of enthalpy change associated with liquid-vapor phase change. These enthalpy differentials are in turn combined with significant mass transport fluxes as well as a combination