![]() ![]() Fluids with molecular weights of less than 43 are generally gases, which include gas condensates, wet gases, and dry gases. Oils with molecular weights greater than 210 usually are classified as heavy oils. In contrast, volatile oils are lower in molecular weight than black oils and typically range from 43 to 70. Black oils typically range from 70 to 150 in molecular weight but may range as high as 190 to 210. Despite this lack of precision and the occasional confusion it brings, classification is quite useful and popular. There is no strict definition of volatile and black oils there are only general guidelines and characteristics. The petroleum fluid spectrum is gradational. Volatile and black oil fluid characteristics 1 Volatile and black oil fluid characteristics.Water being a fluid, specifically liquid, is vicious. What are the Types of Viscosity?Įngineering fluid mechanics provides two types of viscosity Dynamic Viscosity and Kinematic Viscosity. So, the resistance force against the flow by water will be less as compared to honey. Among, the two fluids, water, and honey, honey has high viscosity as compared to water. Let’s describe the term high-viscosity with an example. The fluid with high viscosity offers greater flow resistance. High viscosity usually means the liquid is thicker. Blood circulation inside our body depends on the viscosity of blood.Gums, coolants, petrol as a cleaner, brake fluid, cosmetics, food products, etc all require viscosity data during production to work smoothly.Cooking oils, fats, butter, etc are manufactured to provide a specific viscosity.For preparing various medicines like syrups viscosity data is required.For example, light machines use low viscous liquids whereas highly viscous oils are used in heavy machines. In lubrication engineering viscosity data and its variation with temperature is an absolute necessity to decide suitable lubrication for specific equipment.The molecular weight of organic liquids is determined using the knowledge of viscosity.The following examples can easily substantiate the applications of viscosity: ![]() The concept of Viscosity is used widely in science and technology. Equation 1 mentioned above is basically a mathematical representation of Newton’s law of viscosity. Dynamic viscosity is the coefficient of viscosity as defined in Newton’s law of viscosity. Non-Newtonian fluids do not follow Newton’s law of viscosity and hence their viscosity varies and is dependent on the shear rate. Newtonian fluids obey Newton’s law of viscosity. In another way, it can be stated that the ratio of shear stress to shear rate in a fluid is a constant, and is defined as the coefficient of viscosity. For a given temperature and pressure, Newton’s viscosity law states that the shear stress between two adjacent layers in a fluid is proportional to the velocity gradients between those layers. The relationship between the shear stress and the shear rate of fluid under mechanical stress is established by Newton’s law of viscosity. The following table states the viscosity of some popular substances. Temperature (☌) Kinematic Viscosity (m 2/s X 10 -6) 10 1.3059 20 1.004 30 0.801 50 0.553 70 0.413 90 0.326 100 0.294 Table 2: Kinematic Viscosity of water with respect to temperature Viscosity of Some Common Substances Table 2 below provides the kinematic viscosity of water. The kinematic viscosity of water can easily be obtained by dividing the above dynamic viscosity values by the water density. The following table provides the dynamic viscosity of water with respect to various temperatures. As for liquids, the viscosity decreases with an increase in temperature, the same is true for water. The viscosity of water at 20 0 C is 1 centipoise or 1 cP. Suspended Particles: Suspended materials increases viscosity.Multiphase flow: The viscosity of multiphase flow is affected by the volume of each phase.Liquids being incompressible does not have much impact. Pressure: With an increase in pressure, the viscosity of gases usually increases.Flow Conditions: For laminar flow, the viscosity of liquid remains constant while for turbulent flow viscosity changes.On the contrary, the viscosity of gases increases with an increase in temperature. Fluid Temperature: Usually the viscosity of liquids decreases with an increase in temperature. ![]()
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