Of heat dissipation

Leads serve as the input—output interconnections between the component package and the mounting platform. Sometimes leads also aid in the dissipation of heat generated in the package. In the case of plastic packages, leads are formed from the leadframe, which also acts as a heat-dissipation path and a mechanical support for the die. 

As discussed later, the enclosure of an IPB may carry induced currents up to 95% of the current through the main conductors. Accordingly, the enclosure is designed to carry longitudinal parasitic currents up to 90-95% of the rated current of the main busbars. The cross-sectional area of the enclosure is therefore maintained almost equal to and even more than the main conductors to account for the dissipation of heat of the main conductors through the enclosure only, unless an additional forced cooling system is also adopted. The outdoors part of the enclosure exposed to atmospheric conditions is also subjected to solar radiation. Provision must be made to dissipate this additional heat, from the enclosure. 

This dissipation of heat will not be applicable when the circular section is made of circular extruded sections which have no surface openings. 

Gases and Liquids Tending to Gas Gases cannot lubricate the seal fltees. No dissipation of heat. Use a dual seal with forced convective flow. 

Tlie rates of gas-liquid reaetions are surfaee area dependent. Henee in tlie spontaneous eombustion of oil impregnating fibrous thermal insulation on hot equipment, oxidation is faeilitated by the large exposed surfaee area and, sinee the dissipation of heat is restrieted, the temperature ean rise until the oil ignites spontaneously. 

Forced lubrication is recommended for large-horsepower drives, heavily loaded drives, high-speed drives, or where splash and disk lubrication cannot be used. An oil pump—capacity about 1 gal/min—supplies a continuous spray of oil to the inside of the lower span of chain. The circulation of the lubricant aids in the dissipation of heat and results in a well-lubricated, cooler operating device. 

High pressure homogenization may also be used to form microemulsions but the process of emulsification is generally inefficient (due to the dissipation of heat) and extremely limited as the water-oil-surfactant mixture may be highly viscous prior to microemulsion formation. ... 

Fresh leaf is brought to the factory with a few hours of harvesting. Careful handling prevents bruising and allows for the dissipation of heat generated by continuing respiration. It is then subjected to a withering step to reduce leaf moisture from 75-80% to 55-65%. Withered leaf is flaccid and can be worked further without excessive fracture. 

A mixture of the sulfide, ethylene glycol and hexane in a mantle-heated flask spontaneously overheated and exploded at an internal temperature of around 180°C. It had been intended to maintain the reaction temperature at 60°C, but since alcoholysis of the sulfide is exothermic, presence of the heating mantle prevented the dissipation of heat, and the reaction accelerated continuously until explosive decomposition occurred [1], An incident in similar circumstances involving interaction of the sulfide with 4-methyl-2-pentanol also led to violent eruption of the flask contents. 

The high surface-to-volume ratio can also significantly improve both thermal and mass transfer conditions within micro-channels in two ways firstly, the convective heat and mass transfers, which take place at the multi-phase interface, are improved via a significant increase in heat and mass transfer area per unit volume. Secondly, heat and mass transfers within a small volume of fluid take a relatively short time to occur, enabling a thermally and diffusively homogeneous state to be reached quickly. The improvement in heat and mass transfer can certainly influence overall reaction rates and, in some cases, product selectivity. Perhaps one of the more profound effects of the efficient heat and mass transfer property of micro-reactors is the ability to carry potentially explosive or highly exothermic reactions in a safe way, due to the relatively small thermal mass and rapid dissipation of heat. 

Heat transfer may also play an important role in an adsorption system. The adsorption process is exothermic. Physical adsorption equilibria behave in a manner similar to vapor-liquid equilibria transfer out of the vapor phase is favored by decreasing temperature. Therefore, rapid dissipation of heat away from the adsorbing surface improves adsorption performance. Chemisorption rates, on the other hand, generally increase with increased temperature. 

Making assumptions regarding the dissipation of heat can also influence solid friction, although typically it is less of an issue. This can be explored most easily within the Prandtl-Tomlinson model however, the lessons to be learned... 

The term JT A Hi in equations 8.1 and 8.3 is frequently very small compared to the uncertainty in the determination of A/frcp and in many instances can safely be neglected. This should of course be tested by performing blank experiments under normal operating conditions. For example, the enthalpy associated with breaking an ampule (independently from the contribution from vaporization effects) can be determined by breaking ampules partially filled with the calorimetric solvent in the calorimetric solvent. For many systems this contribution is negligible, provided that a well-designed breaker mechanism and ampules ensure that the dissipation of heat is reduced to a minimum. The importance of vaporization effects can be evaluated as described by Vanderzee [129]. 

Electrophoresis in narrow bore tubes, as performed by Hjerten in 1967, provides a better heat dissipating system. He described an application using glass tubes with an internal diameter (I.D.) of +3 mm. The small volume of the narrow bore tube improves the dissipation of heat due to a lower ratio of the inner volume to the wall surface of a tube (Equation (1)). The better the heat dissipation the higher will be the separation efficiency ... 

A large quantity (700 kg) of the chlorophenol, left in contact with cone, sodium hydroxide solution for 3 days, decomposed, attaining red heat and evolving fumes which ignited explosively. Although this could not be reproduced under laboratory conditions, it is believed that exothermic hydrolysis to the hydroquinone (possibly with subsequent aerobic oxidation to the quinone) occurred, the high viscosity of the liquid preventing dissipation of heat. 

Small pieces of sodium in contact with water react vigorously but do not usually ignite the evolved hydrogen unless the water is above 40°C, or if rapid dissipation of heat is prevented by immobilising the sodium by use of a viscous aqueous solution (starch paste, etc.) or wet filter paper [1]. In contact with ice, sodium explodes violently [2]. Small, hot particles of sodium (remaining from dissolution of larger pieces) may finally explode as do large lumps of the metal in water [1]. Sodium residues from a Wurtz reaction were treated with alcohol to destroy sodium, but later accidental... 

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