Centipoises

The viscosity is expressed in Pa s. The commonly used unit is mPa-s, formerly called centipoise, cP. 

Viscosity is measured in poise. If a force of one dyne, acting on one cm, maintains a velocity of 1 cm/s over a distance of 1 cm, then the fluid viscosity is one poise. For practical purposes, the centipoise (cP) is commonly used. The typical range of gas viscosity in the reservoir is 0.01 - 0.05 cP. By comparison, a typical water viscosity is 0.5 -I.OcP. Lower viscosities imply higher velocity for a given pressure drop, meaning that gas in the reservoir moves fast relative to oils and water, and is said to have a high mobility. This is further discussed in Section 7. 

Poise = cgs unit of absolute viscosity Centipoise = 0.01 poise Stoke = cgs unit of kinematic viscosity Centistoke = 0.01 stoke Centipoises = centistokes X density (at temperature under consideration)... 

The SI unit of viscosity is pascal-second (Pa s) or newton-second per meter squared (N s m ). Values tabulated are mN s (= centipoise, cP). The temperature in degrees Celsius at which the viscosity of a... 

Viscosity is equal to the slope of the flow curve, Tf = dr/dj. The quantity r/y is the viscosity Tj for a Newtonian Hquid and the apparent viscosity Tj for a non-Newtonian Hquid. The kinematic viscosity is the viscosity coefficient divided by the density, ly = tj/p. The fluidity is the reciprocal of the viscosity, (j) = 1/rj. The common units for viscosity, dyne seconds per square centimeter ((dyn-s)/cm ) or grams per centimeter second ((g/(cm-s)), called poise, which is usually expressed as centipoise (cP), have been replaced by the SI units of pascal seconds, ie, Pa-s and mPa-s, where 1 mPa-s = 1 cP. In the same manner the shear stress units of dynes per square centimeter, dyn/cmhave been replaced by Pascals, where 10 dyn/cm = 1 Pa, and newtons per square meter, where 1 N/m = 1 Pa. Shear rate is AH/AX, or length /time/length, so that values are given as per second (s ) in both systems. The SI units for kinematic viscosity are square centimeters per second, cm /s, ie, Stokes (St), and square millimeters per second, mm /s, ie, centistokes (cSt). Information is available for the official Society of Rheology nomenclature and units for a wide range of rheological parameters (11). 

Thermal conductivity to convert watts per meter-kelvin to British thermal unit-feet per hour-square foot-degree Fahrenheit, multiply by 0.57779 and to convert British thermal unit-feet per hour-square foot-degree Fahrenheit to watts per meter-kelvin, multiply by 1.7307. Viscosity to convert pascal-seconds to centipoises, multiply by 1000. 

The resultant viscosity is in centipoise (mPa-sec) if 7 and 7 are given in K and Pa, respectively. This method can also be used for hght nonhydrocarbon gases except for hydrogen where, special N s are required. For hydrocarbons below ten carbon atoms, average errors of about 3 percent can be expected, with errors increasing to 5-10 percent for heavier hydrocarbons. 

If critical pressure and critical temperature are given in Pa and K, respectively, viscosities in centipoise result. The variable Io is either the low pressure pure component or mixture viscosity according to whether a pure component or mixture is being considered. For mixtures, simple molar average pseiidocritical temperature (Kay s rule), pressure, and density, and molar average molecular weight are used. The vapor density can be predicted by the methods previously discussed. Errors of above 5 percent are common for hydrocarbons and their mixtures. Experimental densities will reduce the errors slightly. 

F — 32)/1.8 to convert British thermal units per hoiir-sqiiare foot-degrees Fahrenheit to joules per square meter-second-kelvins, multiply by 5.6783 to convert centipoises to pascal-seconds, multiply hy 10 . ... 

D-limonene (Florida Chemicals). A compound of optically active terpene (CioHie) derived as an extract from orange and lemon oils limited data shows veiy low viscosity at low temperatures—only one centipoise at —50°C natural substance having questionable stabihty, Theiminol D-12 (Mon.santo). A synthetic hydrocarbon clear liquid ... 

FIG. 14-7 O Connell correlation for overall column efficiency for absorption. To convert ffP/ i in pound-moles per cubic foot-centipoise to Idlogram-moles per cubic meter-pascal-second, multiply by 1.60 X 10 . [O Connell, Trans. Am. Inst. Chem. Eng., 42, 741 (1946).]... 

The second, additive term carrying the viscosity impact in Eq. (14-199) is small at viscosities around 1 centipoise but can become controlling as viscosity increases. For example, for air at atmospheric pressure atomizing water, with nozzle conditions. 

As in die case of die diffusion properties, die viscous properties of die molten salts and slags, which play an important role in die movement of bulk phases, are also very stiiicture-seiisitive, and will be refeiTed to in specific examples. For example, die viscosity of liquid silicates are in die range 1-100 poise. The viscosities of molten metals are very similar from one metal to anodier, but die numerical value is usually in die range 1-10 centipoise. This range should be compared widi die familiar case of water at room temperature, which has a viscosity of one centipoise. An empirical relationship which has been proposed for die temperature dependence of die viscosity of liquids as an AiTlienius expression is... 

The bearing health can be best described by plotting a ZNjP versus coefficient of friction curve. Figure 13-10 shows such a curve where Z is the lubricant viscosity in centipoise, N the rpm of the journal, and P is the projected area unit loading. 

Re = Modified Reynold s number Do = Outside tube diameter, ft p = Viscosity, Ib/ft sec centipoises x 0.000672... 

Viscosity Centipoises Gunness and Other Data Plotted Versus Reciprocal Viscosity in Maxweli. (Average viscosity of iiquid on the piates) Drickamer and Bradford Correlation Plotted in Ludwig. (Molal average viscosity of the feed)... 

V = Kinematic liquid viscosity, centistokes (cen-tistokes = centipoises/sp.gr.)... 

Fluid viscosity—For Newtonian fluids (a constant viscosity at all impeller speeds) approximate viscosities up to 5,000 centipoises are satisfactory. Above 5,000 centipoises. estimating errors of 20 to 50% can mean undersizing or oversizing the agitator. 

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