MCE & Thermodynamic cycles for MR
The presence of magnetic moments caused by unpaired spins in a material enables its use as a magnetocaloric material. The size of the magnetocaloric effect (MCE) depends on a number of different conditions which are discussed below. The second section discusses how the magnetocaloric effect may be implemented in a refrigerator through the use of a thermodynamic cycle.
Effects that determine the MCE
The magnetic moments have a certain entropy or disorder. When an external magnetic field is applied to a paramagnetic material, the magnetic moments will try to align with the field. As the moments are more aligned with the field, the magnetic entropy of the material decreases. The total entropy of a magnetic material consists of contributions by the magnetic entropy, the lattice entropy and the electronic entropy. A decrease of the total entropy by decrease of the
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It is depicted in a T(S)-diagram in figure 5. The cycle consists of an adiabatic magnetization followed by isothermal magnetization, after which the material is returned to the original state through adiabatic and isothermal demagnetization. Adiabatic processes are depicted as vertical lines (of constant entropy) and isothermal processes as horizontal lines (of constant temperature). The first isothermal process removes heat from the magnetocaloric material and the final isothermal process removes heat from the load. The Carnot cycle is not particularly useful for room-temperature magnetic refrigeration as four different magnetic fields are needed. First the field must quickly increase for the adiabatic process to take place. Then the magnetic field must slowly increase further to its maximum value for heat to be able to flow into the system. Finally these steps must be carried out in reverse order to return to the initial
The ills that McMillan is satirizing are the most common PowerPoint mistakes. He focuses on the incorrect uses of various PowerPoint techniques. For example, he used satire to explain that using excessive bullet points can cause your key messages not to stand out. He also mentioned that putting every word you are going to say in a slide can result in losing your audience’s attention. Additionally, McMillian explained that using too many graphs just to impress your audience is not necessary.
"Refrigerators." Canada Science and Technology Museum. Canada Science and Technology Museum, 2014. Web. 15 Feb. 2014. .
Whereby, instead of using a separate material as a regenerator to recuperate the heat from the magnetic material, the AMR concept made use of the refrigerant itself as the regenerator [6], thus, making it an active part of the refrigeration cycle. This is possible due to the high heat capacities of common magnetocaloric materials near their Curie temperatures [25].
...gnetic. This new magnetic state stems from the fact that the spins are interacting by the double exchange interaction. Subsequently the insulating state changes to semiconductor. Furthermore, the general concept is that ferromagnetic materials favours metalicity.
One of the greatest accomplishments and innovations of human history thus far is the invention of the electric refrigerator. Such a simple concept has literally changed how the entire world stores food and has saved millions of lives in the process. Refrigeration as we know it has only been around since the 1930’s, and in less then a hundred years has been greatly taken for granted. Since the influence of electrical engineering in the modern refrigerator, refrigeration has gone from storing food in an ice cellar to being able to have two dedicating refrigeration units with controllable temperatures and even an ice machine attached. Without electricity modern refrigeration would be drastically different, using instead previous refrigeration
Magnetism is very useful in our daily life. A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. In addition, magnetic field is a region which a magnetic material experiences a force as the result of the presence of a magnet or a current carrying conductor. Current carrying conductors also known as wire. As we know there have north pole and south pole of a magnet. If same pole of magnet approaches each other, there will repel each other. In contrast, if different pole of magnet approaches each other, they will attract. These are same with the electric charge, if same charge it will repel, different charge it will attract. Although magnets and magnetism were known much earlier, the study of magnetic fields began in 1269 when French scholar Petrus Peregrinus de Maricourt mapped out the magnetic field on the surface of a spherical magnet using iron needles [search from Wikipedia]. Noting that the resulting field lines crossed at two points he named those points 'poles' in analogy to Earth's poles. Each magnet has its own magnetic field which experiences a force as the result of the presence of a magnet and magnetic field has made up of magnetic field lines. The properties of magnetic field lines is it begin at the north pole and end at the south pole. The north pole always flow out while south pole always flow in. The closer the magnetic field lines, the strength of magnetic field increases. Furthermore, these line cannot cross each other. Ferromagnetism is the basic mechanism by which certain materials (such as iron) form permanent magnets, or are attracted to magnets. Ferromagnetic materials...
...owaves actually reflect off of the metal. This can be especially bad if you have a metal container, with that the food won't be able to heat up because the metal is reflecting all the microwaves and leaving the food cold. The bigger issue with this is that there is a possibility that the microwaves can be knocked back to the magnetron which can lead to permanent damage to it.
Finally, the liquid moves to the evaporator, where heat from the inside air is absorbed and changes it from a liquid to a gas. After that, it goes again to the compressor, where the entire cycle is repeated.
... temperature of 112 0C also and a pressure 2.5 bar. Cooling water is used to condense the vapor exiting column. Remaining methane and hydrogen are separated in reflux drum where the vapor stream is combined with other gases streams. The overhead of first and second separator are combined to form fuel gas. The liquid stream exiting in the bottoms of the reflux drum is pumped at pressure of 3.3 bar for discharging pressure. The pump stream is separated in two streams. One stream is to feed to tray one of the column and the other one stream is cooled down to 38 0C in heat exchanger. Then, the cooled product stream is sent to storage.
The topic of magnetic disks is one that involves many physics related phenomenon. The intricate structure and design of “Magnetic Disks” (or hard disks) in computers include the principles of Fluid Flow, Rotational Motion, Electromagnetism, and more. This paper will focus mainly on the previously listed physics occurrences, and the design that goes into engineering the magnetic disk to include them. These physics principles are utilized in such a way that makes the hard disk a very common and useful tool, in this day and age. To most people, the magnetic disk is the most important, yet most mysterious, part of a computer system. A hard disk is a seal unit that holds computer data in the form of magnetic patterns.
In thermodynamics Refrigeration is the major application area, in which the heat is transferred from a lower temperature region to a higher temperature region. The devices which produce refrigeration are known as Refrigerators and the cycle on which it operates are called refrigeration cycles. Vapour compression refrigeration cycle is the most regularly used refrigeration cycle in which the refrigerant is alternately vaporized and condensed and in the vapor phase it is compressed. Gas refrigeration cycle is the well-known refrigeration cycle in which cycle refrigerant remains in the gaseous phase throughout the cycle. Cascade refrigeration are the other refrigeration cycles discussed in this chapter; absorption refrigeration is the one more refrigeration cycle which is used where the refrigerant is dissolved in liquid before it is compressed. One more refrigeration in which refrigeration is produced by passing the electric current through two dissimilar materials is called as the thermoelectric refrigeration.
Temperature has a large effect on particles. Heat makes particles energized causing them to spread out and bounce around. Inversely the cold causes particles to clump together and become denser. These changes greatly F magnetic the state of substances and can also influence the strength of magnetic fields. This is because it can alter the flow of electrons through the magnet.
The mechanical energy (torque) is produced when opposing magnetic fields try to lineup. Therefore, the center line of the north pole of a magnetic field is directly opposite to the centerline of the south pole of another magnetic field (Fitzgerald et al., 1981). The opposing magnetic fields in a motor are generated by two separate concentrically oriented components, the stator and a rotor (Figure 2-5). Figure 2 5 Rotor and stator schematics of a three-phase DC motor. The stator is the stationary component, while the rotor is the rotational component of the motor.
The various types of magnets are used in countless facets in everyday life. Thousands of industries, including automotive, electronics, aerospace, craft, manufacturing, printing, therapeutic and mining utilise magnets so that their machineries, tools and equipment can properly function.