effect of pressure on the viscosity of liquids and especially oils.

  • 4.71 MB
  • English
British Hydromechanics Research Association , [s.l.]
SeriesBHRA technical note -- 16
ID Numbers
Open LibraryOL20904545M

On increasing pressure viscosity of liquid molecules increases due to the effect of pressure on the viscosity of liquids and especially oils.

book in the resistance to the flow of liquid. On increasing pressure, the viscosity of gas molecules decreases due to the increase in glow of molecules. Under most conditions, viscosity is independent of pressure. Viscosity has a pressure dependence for gases when the ideal gas model breaks down (e.g.

at low temperatures. XXXVIII. Viscosity of liquids at high hydrostatic pressures. The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science28 (), DOI: / R.

Dow. Inhibition of Crystallization of Rubber by High by: 8. effect of pressure on the viscosity of pure liquids, and these over only - a comparatively small range of pressure.1 The effect of pressure on the viscosity of a number of lubricating oils has been recently deter mined over a range sufficient to change the viscosity many fold,2 but oils are not simple substances, and the results obtained with.

The viscosities of three lubricating oils have been investigated at °, °, °F at pressures ranging from atmospheric to atmospheres (57, lb./in. 2).While the oils were from fields widely separated geographically, their initial viscosities were matched at poise at °F.

At a pressure of 26, lb./in. 2 at °, however, the viscosities were strikingly different; the Cited by:   The results are interpreted in terms of the liquid structure and the mechanism of viscous flow.

The results of applying our theory to the liquids for which the necessary data is available show that the effect of pressure on viscosity can be calculated a priori, with thermodynamic data only, with reasonable by:   Viscosity of Liquids: For most liquids, viscosity increases with increasing pressure because the amount of free volume in the internal structure decreases due to compression.

Consequently, the molecules can move less freely and the internal friction forces increase. The higher the viscosity of a liquid, the more pressure will be required to push the same volume of liquid in the same amount of time. This is a common problem that you might see in both the Food and petrochemical industry.

In the food industry, e.g., more pressure is required to push cold molasses than hot, lower viscosity, molasses. Bair, R. Casalini, A scaling parameter and function for the accurate correlation of viscosity with temperature and pressure across eight orders-of-magnitude of viscosity.

ASME J. Tribol.() CrossRef Google Scholar. The pressure–viscosity relationship The choice of the pressure–viscosity relationship is vital in film thickness calculations. However, it should be emphasized that the aim of the current study is to determine a value for the pressure–viscosity coefficient appropriate for numerical calculations, where presently only two models prevail.

Are synthetic oils (PAO - Polyalpha olefin and PAG - Polyalkylene glycol) better gear and bearing lubricants than mineral oils. At the heart of the issue is a property we refer to as pressure-viscosity coefficient of the various types of lubricant base oils.

The pressure-viscosity coefficient refers to the relationship between the load placed on the oil film (pressure) at the dynamic load. The absolute viscosity of many fluids relatively doesn't change with the pressure but very sensitive to temperature.

For isothermal flow, the viscosity can be considered constant in many cases. The variations of air and water as a function of the temperature at atmospheric pressure are plotted in Figures and The gear oil shown in Fig. would reach this viscosity at pressure of GPa using the third Roelands model, Eq.

(), with parameters from classical EHL shown in the figure.

Download effect of pressure on the viscosity of liquids and especially oils. EPUB

A more reasonable glass viscosity for organic liquids might be 10 8 Pa s. The popular pressure–viscosity model would still not reach this value until a pressure of. Pressure  Pressure also affects viscosity of most liquids.

 Compressing liquids at medium or low pressures is almost impossible.  This makes pressure not a intense factor to viscosity of liquids.  Changing pressure from about to 30MPa can cause a similar viscosity change.  This is with a change in temperature of approximately 1 degree centigrade.

 The resistance to such flow is called the viscosity. Liquids which flow very slowly, like glycerin or honey, have high viscosities. Those like ether or gasoline which flow very readily have low viscosities.

Viscosity is governed by the strength of intermolecular forces and especially by the shapes of the molecules of a liquid. Viscosities at high pressures for 16 base oils (six polyolesters, three polyglycols, six ionic liquids and squalane) were used to analyze the influence of their chemical structure on the pressure‐viscosity coefficient, α.

Comparisons with literature α values for vegetable bases (canola, soybean and jojoba oils) are also performed. For the. The effect isnegligible in crude oils at temperatures below degrees C and becomes verypronounced (more than 60% mole fraction) as the temperature riser, above degrees C.

The effect of dissolved water on the oleic phase viscosity has never beenreported. DISCUSSION AND CONCLUSIONS It is well known that the viscosity of liquids at high pressure increases considerably.

A rather general rule is that the more complex the molecular structure of the liquid, the larger is the effect of pressure (Reid, ). Pressure effects on a liquid’s viscosity are typically very small and in most cases can be ignored.

Viscosity & Specific Gravity. Viscosity is frequently mistaken for specific gravity (SG). They are two different things. Common vernacular expressions confuse us, as viscosity is more often than not erroneously referred to as a thickness or weight.

(b) Properties of Liquids Employed. The program of testing contemplated originally the use of water and of two oils as experimental liquids. For the latter the range of viscosities was defined by the range of tcmperatures seasonably obtainable, i.e., from almost normal outside temperature upward to a maximum produced by dissipating the power input.


Viscosity depends on the size and shape of the particles that make the liquid, as well as the attraction between the particles. Liquids that have a LOW viscosity flow quickly (ie.

water, rubbing alcohol, and vegetable oil). Liquids that have a HIGH viscosity flow slowly (ie. honey, corn syrup, and molasses).

Liquids that exhibit reduced viscosity with rising temperature are referred to as Newtonian. Motor oils would be a great example of Newtonian fluids.

Description effect of pressure on the viscosity of liquids and especially oils. FB2

Shear Thinning or Thixotropic. Liquids that exhibit reduced viscosity when energy is applied are referred to as shear thinning or thixotropic. Paint would be an example of a shear thinning liquid. Many flow behaviors will be affected by the liquid viscosity, including droplet formation, surface waves, bubble entrainment, slug mixing zones, and even three-phase stratified flow.

Furthermore, the impact of low-Reynolds-number oil flows in combination with high-Reynolds-number gas and water flows may yield new flow patterns and concomitant pressure-drop behaviors. Viscosity affects heat generation in bearings, cylinders and gear sets related to an oil's internal friction.

It governs the sealing effect of oils and the rate of oil consumption, as well as determines the ease with which machines may be started or operated under varying temperature conditions, particularly in cold climates.

Viscosity is a measure of an oil's resistance to flow. The down side of lower viscosity is the protective film of oil cannot support as much weight and pressure in critical areas such as crankshaft bearings. Multi-Grade Motor Oils. Regardless of viscosity level, motor oil also thins out as it gets hotter - something that poses a challenge to engineers.

Motor Oils - Dynamic Viscosity - Dynamic viscosities for motor oils SAE 10 to 50 - temperature range 0 - deg C Pressure Loss in Steel Pipes Schedule 40 - Water flow and pressure loss in schedule 40 steel pipes - Imperial and SI units - gallons per minute, liters per second and cubic meters per hour.

17 When: f=gdh ∴ η1 η2 t1d1 t2d2 η1 is viscosity of liquid 1. η2 is viscosity of liquid 2. t1 flow time of liquid 1. 2 𝑤 𝑖 𝑖𝑞 𝑖 2. d1 density of liquid 1. 2 𝑖 𝑦 𝑖𝑞 𝑖 2. The factors effect on the viscosity: 1. Effect of Temperature: the temperature of the liquid fluid increases its.

Details effect of pressure on the viscosity of liquids and especially oils. FB2

The eleven viscosity grades are: 60, 50, 40, 30, 20, 25W. 20W, 15W, 10W, 5W, and 0W. These numbers are usually defined as oil weights.

Single viscosity oils are normally referred to straight weight oils. The dynamic viscosity of single viscosity winter oils is determined at a various cold temperature as established by SAE J   Introduction.

Viscosity can be not only a fluid’s resistance to flow but also a gas’ resistance to flow, change shape or movement.

The opposite of viscosity is fluidity which measures the ease of flow while liquids such as motor oil or honey which are “sluggish” and high in viscosity are known as may ask the question of what is actually going on in the liquids to make one. The viscosity of liquids almost always increases with pressure, with water being the sole exception.

Its dependence is such that at the normal pressures found in heat and mass transfer operations, it can usually be neglected. The most important variation of viscosity for non-Newtonian liquids is.

Increasing °API or line average temperature reduces the crude oil viscosity (see Figure 4). The reduction of viscosity results in higher a Reynolds number, lower friction factor and in effect lowers pumping power requirements. For the cases studied in this TOTM, the effect of crude oil viscosity on the performance of pump was considered.Viscosity, resistance of a fluid (liquid or gas) to a change in shape, or movement of neighbouring portions relative to one another.

Viscosity denotes opposition to flow. The reciprocal of the viscosity is called the fluidity, a measure of the ease of flow. Molasses, for example, has a greater viscosity. Viscosity is the resistance to flow, so higher viscosity fluids flow more slowly at a given level of force pushing them along.

Viscosity has internal friction of fluids, which causes the fluids to appear thicker when flowing. Knowing a fluid's viscosity .