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Platinum heat conductance

The flammability of solid substances is determined by burning rate tests [10,134,135]. From a mold, a pile of the substance under investigation is placed on a noncombustible, nonporous, and low heat-conducting base plate. One end of the pile is ignited by a hot gas flame or a hot platinum wire (temperatures above 1000°C). The burning rate is established and measured. [Pg.88]

When used as monolithic, porous catalytic membranes, the platinum group metals provide higher mechanical stability and heat conductivity than conventional supported metal catalysts. The cost, however, can be an issue. An economically feasible solution to... [Pg.390]

The sample and reference thermometers and heaters are platinum resistance thermometers (see Sect. 4.1). Instead of relying on heat conduction from a single furnace, governed by temperature difference, reference and sample are heated separately as required by their temperature and the temperature difference between the two furnaces. The two calorimeters are each less than one centimeter in diameter and are mounted in a constant temperature block. This instrument is, thus, a scanning, isoperibol twin-calorimeter (see Sect. 4.2). [Pg.336]

Spots with surface concentrations favoring higher reaction rates cause a rise in local temperature due to the exothermicity of the reaction. Heat conduction across the catalyst surface then provides the coupling. For a very thin (about 200 nm) platinum (110) single-crystal foil, the periodic variation of the reaction rate and hence of the temperature causes a thermal expansion. This leads, in turn, to a periodic deformation of the foil dubbed the heartbeats of a catalyst ... [Pg.226]

A full-elliptic, 2-D steady laminarl CFD code [4-6] was employed to simulate the flow domain in a plane channel configuration having a total length L— 0 mm, channel heights of either 7h = 0.3 or 1 mm, and wall thickness of = 0.1 mm (Fig. 7.1). The first 1 mm was catalyticaUy inert and the remaining La — 9 mm was coated with platinum. Due to symmetry, only half of the flow domain was solved. The flow solver was coupled to a 2-D heat conduction solver for the solid substrate (wall thermal conductivity k ). External heat losses were applied to the outer channel surface as heat flux h(J — T ) using an effective heat transfer coeflicient h, with Ty, the outer surface temperature and set to 298 K. Propane and methane fuels... [Pg.67]

A metal is an electropositive element. There are over 70 metals in the earth s crust. Examples include copper, gold, iron, platinum, silver and tungsten. Chemically, in solution, a metal atom releases an electron to become a positive ion. In bulk metals are solids and tend to have high melting and boiling points (an exception is mercury). They are lustrous, relatively dense, malleable, ductile, cohesive and highly conductive to both electricity and heat. [Pg.29]

Gustafsson et al. measured the thermal conductivity and thermal diffusivity of molten NaNOs KNO3. The approximate dimension of the foil used for NaNO, was platinum measuring 0.010 X 40 X 86 mm The foil was heated by a constant electric current and the measurements were completed within 10 s. Errors due to radiation were considered to be negligible. The accuracy was claimed to be +2.6% for thermal conductivity and 3% for thermal diffusivity, but the effect of current leak from the metallic foil to the molten salts was neglected. [Pg.191]

GP 1[ [R 1[ A change from aluminum to platinum as construction material results in reduced micro-reactor performance concerning oxidation of ammonia, decreasing N2O selectivity by 20% [28]. This is explained by the lower thermal conductivity of platinum, which causes larger temperature differences (hot spots) within the micro channels, i.e. at the catalyst site, e.g. due to insufficient heat removal from the channels or also by non-uniform temperature spread of the furnace heating. [Pg.294]

We used polycrystalline films of ZnO and Sn02 as adsorbents. The films were deposited from the water suspension of respective oxides on quartz substrates. These substrates contained initially sintered contacts made of platinum paste. The gap between contacts was of about lO" cm. All samples were initially heated in air during one hour at T 500 C. We used purified molecular oxygen an acceptor particle gas. H and Zn atoms as well as molecules of CO were used as donor particles. We monitored both the kinetics of the change of ohmic electric conductivity and the tangent of inclination angle of pre-relaxation VAC caused by adsorption of above gases and the dependence of stationary values of characteristics in question as functions of concentrations of active particles. [Pg.74]

The experiments were conducted on similar experimental set-up as shown in Fig. 6.1. Substrate 5 had an internal heater - platinum film deposited on the back side of the substrate. The substrate was heated... [Pg.362]


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See also in sourсe #XX -- [ Pg.248 ]




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