HYDROGEN & HEAT PIPES
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A heat pipe is a heat-transfer device that combines the principles of both thermal A heat pipe is a heat-transfer device that combines the principles of both thermal conductivity and phase transition to effectively transfer heat between two solid interfaces.[1]
At the hot interface of a heat pipe a liquid in contact with a thermally conductive solid surface turns into a vapor by absorbing heat from that surface. The vapor then travels along the heat pipe to the cold interface and condenses back into a liquid – releasing the latent heat. The liquid then returns to the hot interface through either capillary action, centrifugal force, or gravity, and the cycle repeats. Due to the very high heat transfer coefficients for boiling and condensation, heat pipes are highly effective thermal conductors. The effective thermal conductivity varies with heat pipe length, and can approach 100 kW/(m⋅K) for long heat pipes, in comparison with approximately 0.4 kW/(m⋅K) for coppe and phase transition to effectively transfer heat between two solid interfaces.[1]
At the hot interface of a heat pipe a liquid in contact with a thermally conductive solid surface turns into a vapor by absorbing heat from that surface. The vapor then travels along the heat pipe to the cold interface and condenses back into a liquid – releasing the latent heat. The liquid then returns to the hot interface through either capillary action, centrifugal force, or gravity, and the cycle repeats. Due to the very high heat transfer coefficients for boiling and condensation, heat pipes are highly effective thermal conductors. The effective thermal conductivity varies with heat pipe length, and can approach 100 kW/(m⋅K) for long heat pipes, in comparison with approximately 0.4 kW/(m⋅K) for coppeheat pipe is a heat-transfer device that combines the principles of both thermal conductivity and phase transition to effectively transfer heat between two solid interfaces.[1]
At the hot interface of a heat pipe a liquid in contact with a thermally conductive solid surface turns into a vapor by absorbing heat from that surface. The vapor then travels along the heat pipe to the cold interface and condenses back into a liquid – releasing the latent heat. The liquid then returns to the hot interface through either capillary action, centrifugal force, or gravity, and the cycle repeats. Due to the very high heat transfer coefficients for boiling and condensation, heat pipes are highly effective thermal conductors. The effective thermal conductivity varies with heat pipe length, and can approach 100 kW/(m⋅K) for long heat pipes, in comparison with approximately 0.4 kW/(m⋅K) for coppe
HYDROGEN METAL HYDRIDES - EDEN PROJECT
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;feature=youtu.be" target="_self" title="Hydrogen Metal Hydride">Hydrogen
Absortion & Desorbtion of Hydrogen in Metal Hydrides Tanks with the cooling and heating support of a thermoelectric Device & heat pipe system, made with stain steel and liquid sodium as a heat exchanger fluid.
Hydrogen storage is basically focused in methods for storing H2 for subsequent use. The methods span many approaches, including high pressures, cryogenics, and chemical compounds that reversibly release H2 upon heating. Hydrogen storage is a topical goal in the development of a hydrogen economy.
Hydrogen will be playing an important role with electricity in the 21st Century as the primary energy carriers in the nation's sustainable energy future. Both energy carriers will ultimately come from renewable energy sources, although fossil fuels will provide a long-term transitional resource. Future hydrogen suppliers will deliver a significant portion of Europe's energy for transportation and other applications. For these applications, hydrogen offers a non-polluting, inexhaustible, efficient and potentially cost-effective energy system derived entirely from domestic energy resources
SOLID-H™ hydrogen storage containers are filled with metal powders that absorb and release hydrogen (metal hydrides). You may already be using metal hydrides in your laptop computer (nickel-metal hydride batteries).
The most popular SOLID-H containers supply a few atmospheres of hydrogen gas pressure at room temperature. This is the safest method known for storing flammable hydrogen gas. If your hydrogen system develops a leak, SOLID-H immediately releases a small fraction of its stored hydrogen. The remainder will be released over a period of hours.
Typical uses for SOLID-H include hydrogen supplies for gas chromatographs and fuel storage for hydrogen engines or fuel cells. A typical SOLID-H container is shown below.
Metal hydrides are chemical compounds formed when hydrogen gas reacts with metals. The most useful metal hydrides react near room temperature at hydrogen pressures a few times greater than the earth's atmosphere (e.g., 5 bar, 73 psia). Metal hydrides are certainly the safest way to store flammable hydrogen gas.
Typical metal hydrides are powders whose particles are only a few millionths of a meter (microns) across. When these metal powders absorb hydrogen to form hydrides, heat is released. Conversely, when hydrogen is released from a hydride, heat is absorbed.
The process is illustrated below:
Hydrogen gas molecules (H2) stick to the metal surface and break down into hydrogen atoms (H). The hydrogen atoms* then penetrate into the interior of the metal crystal to form a new solid substance called a "metal hydride". The metal atoms are usually stretched apart to accommodate the hydrogen atoms. The physical arrangement (structure) of the metal atoms may also change to form a hydride. The lower portion of the illustration shows the desorption process. Hydrogen atoms* (H1 ) migrate to the surface of the metal hydride, combine into hydrogen molecules H2 ) and flow away as hydrogen gas. The metal atoms contract to form the original metal crystal structure.
*Note: It is not exactly correct to say "hydrogen atoms migrate". A hydrogen atom consists of a proton and an electron. As metals bind hydrogen metallically, protons move among the metal atoms through a "sea of electrons" that include electrons from the metal and from hydrogen. If the proton is not closely associated with any particular electron it is not, strictly speaking, a "hydrogen atom".
Rechargeable Metal Hydride Containers
Storing and recovering hydrogen from a metal hydride container at specific rates requires a delicate balance of pressure and temperature management. Experimental studies of absorption and desorption rates of hydrogen in cylinders containing metal hydrides at controlled pressures and external temperatures. The data from these studies resulted in an analysis tool called HAWK (Hydride Analysis With Kinetics) in the early1980s.
HAWK is a nodal finite analysis heat transfer model with chemical kinetics within each finite node. For large containers, HAWK is purely a heat transfer model. Chemical kinetics are very fast, relative to heat transfer, in large containers (several cm).
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