Thermal properties maximum operating temperature

On the other hand, following the development of hybrid combustor configurations that prevent operation of the catalyst module at temperatures above 900-1000 °C, the major drawback of metallic monoliths, namely the limited maximum operating temperature, has been overcome. Accordingly, honeycombs made of metal foils have been adopted in GT catalytic combustors in view of their excellent thermal shock resistance and thermal conductivity properties [9]. In addition, metallic substrates are a promising option for the fabrication of microcombustors. 

Metal monoliths have interesting properties, such as high tolerance for mechanical stress and vibrations and high thermal conductivity. Moreover, the cell walls may be thinner as compared to their ceramic counterparts. However, the maximum operating temperature of metal monoliths is not as high as for vanous ceramics. This is not a problem for certain combustor designs that limit the temperature in (part of) the catalyst... 

Desirable properties of the immobilized liquid phase in a gas-liquid chromatographic column include (1) low volatility (ideally, the boiling point of the liquid should be at least 100°C higher than the maximum operating temperature for the column) (2) thermal stability (3) chemical inertness and (4) solvent characteristics such that k and a (see Section 30E-4) values for the solutes to be resolved fall within a suitable range. 

Thermal properties include parameters such as expansion coefficient, maximum operating temperature and also involve the thermal stability of polymers when they are exposed to heat either during processing operations such as mouldings and also, during the service life of components. Polymers such as PEI, PSU, PI, PPS and PES all have exceptional thermal properties. 

The carbon-fiber/polymer composites reviewed in the previous section have excellent mechanical properties but limited temperature resistance. Maximum operating temperature is presently 370°C (Table 9.2). These composites cannot meet the increasingly exacting requirements of many aerospace applications which call for a material with low density, excellent thermal-shock resistance, high strength, and with temperature resistance as high or higher than that of refractory metals or ceramics. These requirements are met by the so-called carbon-carbon materials. 

DIBt media list 40, Table A.36, is a white list of liquids with proven minimum properties. The reduction factors R2B for chemical-thermal media influence are based on creep tests under the influence of water and are valid up to the stated maximum operating temperatures. Media labeled by permeation in Table A.36 exhibit pronounced permeation tendency at operating temperatures > 60 C. In general, a tendency for permeation has to be considered for all aqueous media at operating temperatures > 60 °C. 

The homopolymers, being long-chain high molecular weight molecules with a minimum of random orientation, have optimum thermal, chemical, and physical properties. For this reason homopolymer material is preferred for difficult chemical, thermal, and physical conditions. The maximum allowable operating temperature of polypropylene is 225°F/107 C, however this may have... 

A fermentation broth contained in a batch-operated stirred-tank fermentor, 2.4m in inside diameter D, is equipped with a paddle-type stirrer of diameter (L) of 0.8 m that rotates at a speed Af = 4s -. The broth temperature is maintained at 30 °C with cooling water at 15°C, which flows through a stainless steel helical coil that has a 50 mm outside diameter and is 5 mm thick. The maximum rate of heat evolution by biochemical reactions, plus dissipation of mechanical energy input by the stirrer, is 51000 kcal h , although the rate varies with time. The physical properties of the broth at 30 °C were density p = 1000 kg m " , viscosity p = 0.013 Pa s, specific heat Cp = 0.90 kcal kg °C , and thermal conductivity K = 0.49 kcal h m °C = 0.000136 kcals m °C . ... 

In order to select materials that will maintain acceptable mechanical characteristics and dimensional stability one must be aware of both the normal and extreme thermal operating environments to which a product will be subjected. TS plastics have specific thermal conditions when compared to TPs that have various factors to consider which influence the product s performance and processing capabilities. TPs properties and processes are influenced by their thermal characteristics such as melt temperature (Tm), glass-transition temperature (Tg), dimensional stability, thermal conductivity, specific heat, thermal diffusivity, heat capacity, coefficient of thermal expansion, and decomposition (Td) Table 1.2 also provides some of these data on different plastics. There is a maximum temperature or, to be more precise, a maximum time-to-temperature relationship for all materials preceding loss of performance or decomposition. Data presented for different plastics in Figure 1.5 show 50% retention of mechanical and physical properties obtainable at room temperature, with plastics exposure and testing at elevated temperatures. 

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