Viscous freezing

HOCHj CHjOH. Colourless, odourless, rather viscous hygroscopic liquid having a sweet taste, b.p. 197 C. Manufactured from ethylene chlorohydrin and NaHC03 solution, or by the hydration of ethylene oxide with dilute sulphuric acid or water under pressure at 195°C. Used in anti-freezes and coolants for engines (50 %) and in manufacture of polyester fibres (e.g. Terylene) and in the manufacture of various esters used as plasticizers. U.S. production 1979 1 900 000 tonnes. 

The fluid is formulated from a premium mineral od-base stock that is blended with the required additive to provide antiwear, mst and corrosion resistance, oxidation stabdity, and resistance to bacteria or fungus. The formulated base stock is then emulsified with ca 40% water by volume to the desired viscosity. Unlike od-in-water emulsions the viscosity of this type of fluid is dependent on both the water content, the viscosity of the od, and the type of emulsifier utilized. If the water content of the invert emulsion decreases as a result of evaporation, the viscosity decreases likewise, an increase in water content causes an increase in the apparent viscosity of the invert emulsion at water contents near 50% by volume the fluid may become a viscous gel. A hydrauHc system using a water-in-od emulsion should be kept above the freezing point of water if the water phase does not contain an antifreeze. Even if freezing does not occur at low temperatures, the emulsion may thicken, or break apart with subsequent dysfunction of the hydrauHc system. 

Bubble-Tube Systems The commonly used bubble-tube system sharply reduces restrictions on the location of the measuring element. In order to ehminate or reduce variations in pressure drop due to the gas flow rate, a constant differential regulator is commonly employed to maintain a constant gas flow rate. Since the flow of gas through the bubble tube prevents entiy of the process liquid into the measuring system, this technique is particularly usefiil with corrosive or viscous liquids, liquids subjec t to freezing, and hquids containing entrained solids. 

Pure ethylene glycol freezes at —I2,7°C, Exact composition and temperature for eutectic point are unknown, since solutions in this region turn to viscous, glassy mass that makes it difficult to determine the true freezing point. For the concentrations lower than eutectic, ice forms on freezing, while on the concentrated, solid glycol separates from the solution. 

For VISCOUS liquid service it is advisable to allow 25% overpressure where per missable, to size conservatively, and to consider the use of the bellows and/or steam lacKeted bodies (see page 63) for ihe purpose of isolating the moving pans and to prevent freezing of the lading fluid... 

Freezing action Because of the heat exchange between the flowing TP melt and the mold walls, the flow may freeze (solidify) before the product is completely filled. Products that have alternate sections with thick and then thin walls can cause problems in flow and cooling that make them difficult to fill. In some cases the plastics that have been selected for the end use requirement are too viscous to flow properly in a mold cavity, and this makes the manufacture difficult. 

Methyl Dihydroabietate (Commercial product developed by Hercules Powder Co under name Hercolyn . Another product is Hercolyn-D , which is Hercolyn deodorized by steam-blowing), C19H31COOCH3,mw 318.48, colorl to faintly amber colored liq mp, does not freeze at —40°, but becomes very viscous bp 356—70° with si decompn d 1.020—1.030g/cc for Hercolyn flash p 183° and fire p 218° (Cleveland open... 

Nitroisobutylglycerol Trinitrate (NIBGTN). 02N.C(CH20N02)3, mw 286.12, N 19.58% (Nitrate N= 14.69%), OB to COj 0 thick, yellowish, odorless oil which is more viscous than NG mp, did not freeze at —50° bp, decomps or deflagrates in 5sec at 180—85° without deton, detonates when heated with flame in a sealed capillary tube d 1.64g/cc at 20°... 

The chamber-to-condenser pathway usually involves dimensions on the order of 10 cm or greater even for laboratory freeze dryers. Here, the ratio of radius to mean free path is on the order of 0.01 or less, and flow should be essentially viscous flow. Conductance should be linear in pressure, with a zero pressure intercept near zero. Qualitative agreement with theory is observed (data not shown). 

That part of the water which is not frozen due to high freezing rate, forms highly viscous occlusions in between the ice crystals. 

If the temperature of the hot liquid interface is low enough to cause freezing of the surface, or even to form a viscous slush, RPTs are then rare. 

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