Energy-efficient forming

Carbon Composites. Cermet friction materials tend to be heavy, thus making the brake system less energy-efficient. Compared with cermets, carbon (or graphite) is a thermally stable material of low density and reasonably high specific heat. A combination of these properties makes carbon attractive as a brake material and several companies are manufacturing carbon fiber—reinforced carbon-matrix composites, which ate used primarily for aircraft brakes and race cats (16). Carbon composites usually consist of three types of carbon carbon in the fibrous form (see Carbon fibers), carbon resulting from the controlled pyrolysis of the resin (usually phenoHc-based), and carbon from chemical vapor deposition (CVD) filling the pores (16). 

The carbons are broadly comparable in terms of their maximum concentration and implied energy efficiency but the two monolithic forms offer the advantage of smaller pressure vessel sizes and improved heat transfer. 

Flue gas recirculation (FGR) is the rerouting of some of the flue gases back to the furnace. By using the flue gas from the economizer outlet, both the furnace air temperature and the furnace oxygen concentration can be reduced. However, in retrofits FGR can be very expensive. Flue gas recirculation is typically applied to oil- and gas-fired boilers and reduces NO, emissions by 20 to 50%. Modifications to the boiler in the form of ducting and an energy efficiency loss due to the power requirements of the recirculation fans can make the cost of this option higher. 

The bicycle s energy efficiency superiority extends beyond hninali loconiotion and beyond all other forms of transportation. By com ertmg food into the energy equivalent of gasoline, the kilocalories of food energy needed by a human to pedal a bicycle is only a fraction of that needed to propel planes, trains, and automobiles (see Table 1). 

The control of energy in its various forms was always a necessity that became more relevant with the increasing performance requirements of the twentieth centui y. The control of energy conversion contributes to the optimization in performance and energy efficiency for all processes, machines, and devices. 

The improvement of human control over inanimate forms of energy, put to use to military ends, has improved the logistics and coordination aspects of armies and navies, and increased the overall destructive capacity of humanity. Energy-efficient propulsion systems have reduced the costs and increased the ranges of various forms of transportation, both militai y and civilian. For the militai y, energy is both a blessing and a vulnerability, requiring ever-more-specialized soldiers and more expensive equipment to remain effective in the face of competition from other modern military forces. 

In providing an overall picture of the Griffith theory applied to the comminution process, it must be pointed out that the theory requires that a tensile stress should exist across a crack to open it further. While a uniform compressive force can close a crack, a nonuniform one can lead to the occurrence of localized tensile stresses. In a comminution process the particles are subjected to nonuniform loading, and therefore it can be surmised that they normally break in tension and not in compression. However, the tensile component of loading in comminution does not form the major loading component and this contributes towards a lowering of the overall energy efficiency of comminution. 

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