Opaque surface

It promotes adhesion of intaglio inks to the polypropylene surface. An acrylic based primer is a good choice because of its ability to effectively bond water-based inks. Dry powder form of acrylic primer is diluted with methyl ethyl ketone and xylene (each component is mixed in equal parts by weight). To create the opaque surface, 5wt% titanium dioxide pigment is added to the solution. 

Another alternative to using multiple beam interferomtery for surface separation determination was offered by Stewart [76] who coupled a capacitance sensor to the SFA Mark IV to measure the deflection of the double cantilever force measuring spring. The capacitance dilatometry method enables the study of opaque surfaces at the same time as the distance and force normalised to the radius resolution remain equal to that of the regular SFA, or even better [77], However, using this method, the absolute separation cannot be determined. 

For an opaque surface, the relationship between the spectral hemispherical reflectivity and the spectral hemispherical absorptivity is... 

Consider, for example, the arrangement in Fig. 8-61. The two diffuse opaque surfaces are separated by a specular-diffuse transmitting and reflecting plane. For this example all planes are assumed to be infinite in extent. The specular-transmitted exchange between surfaces 1 and 3 may be calculated immediately with... 

The network method which we have used to analyze radiation problems is an effective artifice for visualizing radiant exchange between surfaces. For simple problems which do not involve too many surfaces the network method affords a solution that can be obtained quite easily. When many heat-transfer surfaces are involved, it is to our advantage to formalize the procedure for writing the nodal equations. For this procedure we consider only opaque, gray, diffuse surfaces. The reader should consult Ref. 10 for information on transmitting and specular surfaces. The radiant-energy balance on a particular opaque surface can be written... 

After heat treatment the amber is polished again. This must be done carefiilly as too much polishing will remove the darkened or opaque surface. 

The absorption of radiation incident on an opaque surface of absorptivity a. 

I his is an importaui property relation since it.enables us to determine both the absorptivity and reflectivity of an opaque surface by measuring cither of these properties. 

It is very tempting to use Kirchhoff s law in radiation analysis since the relation c - a together with p = 1 - a enables us to determine all three properties of an opaque surface from a knowledge of only one property. Although Eq. 12-47 gives acceptable results in most cases, in practice, carp should be exercised when there is considerable dilference between the surface temperature and the temperature of the source of incident radiation. 

Tile spectral absorptivity of an opaque surface is as shown on the graph. Determine the absorptivity of the surface for radiation emitted by a source at (o) 1000 K and b) 3000 K. 

Solar radiations is incident on an opaque surface at a rate o17400 W/m . The emissivity of the surface is 0.65 and the... 

Consider two diffuse, gray, and opaque surfaces of arbitrary shape maintained at uniform temperatures, as shown in I ig. ] 3-22. Recognizing that the radios-ity J represents the rate of radiation leaving a surface per unit surface area and dial the view factor, y represents the fraction of radiation leaving surface i that strikes surface j, the net rate of radiation heat transfer from surface i to surface j can be expressed as... 

Consider an enclosure consisting of two opaque surfaces at specified temperatures r, and T2, as shown in Fig. 13-24, and try to determine llie net rate of radiation heat transfer between the two surfaces with the network method. Surfaces 1 and 2 have emissivities c, and and surface areas /1 and A2 and are maintained at uniform temperatures T, and T, respectively. There are only two surfaces in the enclosure, and thus we can write... 

This important result is applicable to any two gray, diffuse, and opaque surfaces that-fqrm an enclosure. The view factor f 2 depends on the geometry and must hj "determined first. Simplified forms ofRq. 13-36 for some familiar arrangements that fonn a two-surface enclosure are given in Table 13-3. Note that f, 2 = I for of these special cases. 

The net rate of radiation transfer between any two gray, diffuse, opaque surfaces that form an enclosure is given by... 

The photocell might be adjusted to trigger the relay when a str t light is turned on it could be hidden behind a small hole in an opaque surface so that it would trigger at a... 

When radiation strikes an opaque surface, only a fraction is absorbed. The remainder is reflected. The fraction absorbed is indicated by the emissivity e of the surface. The emissivity depends upon surface composition. As stated above, the emissivity... 

The radiation exitent from an opaque surface can include emitted and reflected components. The radiosity is the sum of the emissive power and the portion of irradiation that is reflected by the... 

Consider an enclosure of N diffuse-gray, opaque surfaces, each surface being isothermal and having a uniform radiosity and irradiation. The radiative energy balance for the ith surface gives = A J - G,), where J = + p G = + (1- j)Gj. Combining these two equations to... 

Noting for opaque surfaces that a(= e) + p — 1, we can express p and pi in terms of ci and and rearrange this equation, after dividing numerator and denominator by i< 2, as... 

The method is demonstrated here in terms of an enclosure made of N opaque surfaces, some being fiat, some convex, and some concave (Fig. 9.36). First, complete an enclosure by replacing any hole with a black surface at the ambient temperature as we have done before for solutions by electrical analogy. 

In furnaces and other high-temperature equipment, where radiation is particularly important, the usual objective is to obtain a controlled rate of net heat exchange between one or more hot surfaces, called sources, and one or more cold surfaces, called sinks. In many cases the hot surface is a flame, but exchange of energy between surfaces is common, and a flame can be considered to be a special form of translucent surface. The following treatment is limited to the radiant-energy transfer between opaque surfaces in the absence of any absorbing medium between them. 

Relations among Surface Properties. Because incident energy onto an opaque surface is either reflected or absorbed by the surface, it follows that one unit of radiant energy incident on an opaque surface at a given wavelength and from a given direction will have a fraction absorbed and the remainder reflected, or... 

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