What fluid has the highest viscosity?
If high temperature is allowed, the viscosity of molten steel, magma, etc. is very high, and if it is at room temperature, the viscosity of various oils is relatively high, especially crude oil. Such as food industry products, chocolate sauce, honey, etc. have a large viscosity. In addition, the viscosity of the liquid changes greatly with the temperature. Under the premise of no solidification, the lower the temperature, the greater the viscosity. The change can be several times to ten times as large as below 200 degrees.
The so-called high-viscosity liquid means that the liquid is viscous and thick, which is different from ordinary liquids and non-Newtonian fluids (mud, pulp). It moves slowly and is very difficult to filter by simple methods. What’s more, in addition to some dust, the liquid also contains incompletely dissolved colloidal particles. For example solutions of rubber, paraffin, cellulose acetate, viscose, polyacrylonitrile, paint, and animal glue.
What is the dynamic viscosity of fluid?
Dynamic viscosity (dynamic viscosity), also known as dynamic viscosity, absolute viscosity, or simple viscosity, is defined as the ratio of stress to strain rate. During relative motion, the internal friction force is generated by the fluid interaction between them. The unit is N·s/㎡ (Newton second per meter square), that is, Pa·s (Pascal second), and its dimension is M/(L·T).
The coefficient of internal friction that characterizes the viscosity of a liquid, expressed in μ. The viscosity of common liquids decreases with increasing temperature, and the viscosity of common gases increases with increasing temperature.
Effects of viscosity in fluids
1. Type of fluid
There is no doubt that the viscosity of different types of fluids must be different. The type of fluid can be regarded as the molecular force generated by the size of different fluid molecules so that we can better understand the influence of fluid type on viscosity.
Temperature is the biggest factor affecting fluid viscosity itself. The viscosity of a fluid is mainly derived from the friction between molecules, which can also be regarded as an attractive force between molecules. When the temperature rises, the distance between the molecules will increase, and the attractive force between them will decrease, so that the force between the molecules will decrease, and the viscosity of the fluid will decrease. Conversely, when the temperature decreases, the viscosity of the fluid increases. Temperature is the largest and most obvious factor affecting the viscosity of a fluid. Therefore, when measuring fluid viscosity, it is often required to keep the temperature of the fluid at plus or minus 0.1°C of the temperature to be measured. During the measurement process, a water bath or a heating temperature control device is used to assist the viscometer in temperature control.
Pressure has a very small, but not constant, effect on the viscosity of a fluid. Because pressure has little effect on the distance between molecules, the energy consumed to compress the distance between molecules closer by pressure is higher than the effect energy produced by temperature.
In many cases, in order to increase a certain performance of the fluid, or to reduce the negative effect of the fluid, some additives are often added, which we have also mentioned in the previous article. Adding a thickener or thinner to a fluid can greatly increase or decrease the viscosity of the fluid.
5. The category of the fluid itself
Generally speaking, the viscosity of non-Newtonian fluids is higher than that of Newtonian fluids. For example, viscosity cups are usually used to measure the viscosity of Newtonian and quasi-Newtonian fluids, and their viscosity ranges are relatively small. Of course, this is not absolute.
When we measure the viscosity of a fluid, it is often the viscosity of the pure fluid and does not involve the concentration of the fluid. Because if the concentration of the fluid is involved, it is difficult to express the viscosity of a fluid substance. Of course, the higher the concentration of the same fluid, the higher the viscosity. For example, the thicker the syrup, the greater its viscosity; the thinner the syrup, the lower its viscosity.
The viscosity of the gas is produced by the mixing and collision of molecules caused by the internal movement of gas molecules. As the temperature rises, the speed of molecular motion increases, and the chances of molecular mixing and collision between layers increase, so that the mass of gas layers with different speeds Exchange with momentum intensifies. Therefore, the viscous force increases, and the viscosity increases.
Therefore, the factors that affect the viscosity of the fluid include the type, category, temperature, pressure, and additives of the fluid, which will affect the viscosity of the fluid. And if strictly speaking, the factor that affects fluid viscosity is only temperature. Therefore, we can improve the viscosity of the fluid by adjusting the temperature in production and life according to the characteristics corresponding to the temperature and the viscosity of the fluid to meet our needs.
How to transfer high-viscosity liquid?
In the petrochemical industry, the transportation of high-viscosity liquids (such as synthetic rubber, resin, fiber polymerization liquid, etc.) is one of the main consumption processes, and the machinery used to complete the liquid transportation is various pumps. The viscosity is high, and the suction resistance of the pump is relatively large. In order to ensure that the pump has a certain self-priming ability, positive displacement pumps are usually used to transport high-viscosity liquids.
A screw pump is a typical positive displacement pump, which has the good self-priming ability and wear resistance and can operate under high pressure and high temperature. It can effectively handle high-viscosity materials, such as paste, jelly, asphalt, paint, glue, etc. Choosing the right pump model and material can ensure the safe and efficient delivery of high-viscosity materials.
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