Nonfoaming

Molding. The reaction mixtuie can be discharged iato a mold to flow out and fill the cavity. High density (about 320 kg/m or 20 lbs/fT) mol dings can be used for decorative furniture items such as drawer fronts or clock frames. The formulation can be adjusted to produce articles with a nonfoam skia layer and a cellular core which are known as stmctural foams. 

Pressure drop due to hydrostatic head can be calculated from hquid holdup B.]. For nonfoaming dilute aqueous solutions, R] can be estimated from f i = 1/[1 + 2.5(V/E)(pi/pJ ]. Liquid holdup, which represents the ratio of liqmd-only velocity to actual hquid velocity, also appears to be the principal determinant of the convective coefficient in the boiling zone (Dengler, Sc.D. thesis, MIT, 1952). In other words, the convective coefficient is that calciilated from Eq. (5-50) by using the liquid-only velocity divided by in the Reynolds number. Nucleate boiling augments conveclive heat transfer, primarily when AT s are high and the convective coefficient is low [Chen, Ind Eng. Chem. Process Des. Dev., 5, 322 (1966)]. 

Selection of Solvent When choice is possible, preference is given to liquids with high solubilities for the solute a high solubility reduces the amount of solvent to be circulated. The solvent should be relatively nonvolatile, inexpensive, noncorrosive, stable, nonviscous, nonfoaming, and preferably nonflammable. Since the exit gas normally leaves saturated with solvent, solvent loss can be costly and may present environmental contamination problems. Thus, low-cost solvents may be chosen over more expensive ones of higher solubility or lower volatility. 

One useful method of aqueous defoaming is to add a nonfoam sta-bihzing surfac tant which is more surface-active than the stabilizing substance in the foam. Thus a foam stabilized with an ionic surfactant can be broken by the addition of a very surface-active but nonstabihzing sihcone oil. The sihcone displaces the foam stabilizer from the interface by virtue of its insolubility. However, it does not stabilize the foam because its foam films have poor elasticity and rupture easily. 

Allow at least 3 sec residence time in the downcomer for disengagement of vapor for a nonfoaming system, and 6 sec for a foaming system [238]. ... 

De-oiling, typically using a blend of chemical materials such as caustic and alkaline phosphates together with nonfoaming surfactants the phosphates employed are generally either trisodium phosphate (TSP) or tetrapotassium pyrophosphate (TKPP)... 

Where the acid is left in the boiler for this length of time, it must be particularly well inhibited. HC1 is essentially nonfoaming, although some low-cost by-product acids, which may have a tendency to foam, are sometimes used. Where concentrated acid and water are mixed together in the boiler vessel (acid blend-fill arrangement), this work should be completed within 2 hours. 

Inhibitor required for hydrochloric acid (cleaning grade, nonfoaming) Rodine 52 or Armohib 28 at 1 to 3 gallons per 1,000 gallons of dilute acid... 

Nonfoaming surfactants Nonhydrolyzable tannin polymer functional 123 ... 

Polyester polyols account for only ca. 10% of the total polyol market, which is dominated by polyether polyols such as hydroxy-terminated polyoxyethylene or polyoxypropylene. Polyester polyols are preferred for applications where better mechanical properties, wear resistance, and UV stability are required. The largest application of polyester polyols is flexible specialty polyurethane foam in the furniture, packaging, and automotive industries. Polyester polyols are also used for nonfoam applications such as coatings, paints, sealants, and adhesives 47... 

An integrally monlded composite article comprised of (I) a nonfoam layer formed from a thermoplastic elastomer powder composition (A) and (II) a foam layer formed from a foamable composition comprised of (i) (B) a thermoplastic synthetic resin powder, and (C) a heat decomposable foaming agent and (D) a liquid coating agent, wherein the thermoplastic elastomer powder (A) is comprised of a composition of an ethylene-alpha-olefm copolymer mbber and a polyolefin resin or thermoplastic elastomer powder comprised of a partially crosslinked composition of an ethylene-alpha-olefm copolymer mbber and a polyolefin resin, the thermoplastic elastomer powder having a complex dynamic viscosity at 250 deg C and a freqnency of 1 radian/sec of not more than 1.5x1,000,000 poise and having a Newtonian viscosity index n, calculated by a specific formula. 

Figure 13.34. Chart for finding the diameters of valve trays. Basis of 24 in. tray spacing and 80% of flood for nonfoaming services. Use Figure 13.32(b) for approximate adjustment to other tray spacings, and divide the Vload= V-J——— by the...

Foaming or nonfoaming fluids (foaming occurs with low surface tension liquids) ... 

Figure 6.12a shows the structure of the fluid mixture in a downcomer operated at low liquid rates with a nonfoaming mixture. At the upper (froth) zone of the downcomer, the vapor fraction is high and of the same order as in the tray froth. As the mixture travels downward, much of the vapor is disengaged. The froth zone transforms into an aerated liquid zone where vapor bubbles rise through a liquid pooL Upon further vapor disengagement, the aerated liquid zone transforms into a clear liquid zone. 

Liquid flow rate At low liquid flow rates, with nonfoaming systems, the line of demarcation between zones in Fig. 6.12a is fairly sharp (42). As liquid rate increases, so does the fractional gas holdup in the downcomer liquid. Lockett and Gharani (43) found... 

If liquid flows are extremely small, and the system is nonfoaming, circular or envelope downcomers may be installed within the area subtended by a segmental weir (1,10). These should have twice the area calculated using the normal design procedure. 

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