Warm greetings to all in the 6th post on #Day5 ! Today we are going to talk about Fluid of flow🤹🏻, our main focus will be an introduction to flows, transport of fluid, ideal, non ideal gas, compressibility factors. Here we go 🚀,
Introduction🔎
Chemical engineers are interested in many aspects of the problems involved in the flow of fluids. In the first place, in common with many other engineers, they are concerned with the transport of fluids from one location to another through pipes or open ducts, which requires the determination of the pressure drops in the system, and hence of the power required for pumping, selection of the most suitable type of pump, and measurement of the flow rates. In many cases, the fluid contains solid particles in suspension and it is necessary to determine the effect of these particles on the flow characteristics of the fluid or, alternatively, the drag force exerted by the fluid on the particles. In some cases, such as filtration, the particles are in the form of a fairly stable bed and the fluid has to pass through the tortuous channels formed by the pore spaces.
Further, in those processes where heat transfer or mass transfer to a flowing fluid occurs, the nature of the flow may have a profound effect on the transfer coefficient for the process. It is necessary to be able to calculate the energy and momentum of a fluid at various positions in a flow system. It will be seen that energy occurs in a number of forms and that some of these are influenced by the motion of the fluid. In the first part of this post the thermodynamic properties of fluids
will be discussed. It will then be seen how the thermodynamic relations are modified if the fluid is in motion. In later posts, the effects of frictional forces will be considered, and the principal methods of measuring flow will be described.
Types of Fluid 🌬💦
Fluids may be classified in two different ways; either according to their
behavior under the action of externally applied pressure, or
according to the effects produced by the action of a shear stress.
If the volume of an element of fluid is independent of its pressure and temperature, the fluid is said to be incompressible;
if its volume changes it is said to be compressible.
🔗No real fluid is completely incompressible though💦 liquids may generally be regarded as such when their flow is considered.
🌬Gases have a very much higher compressibility than liquids, and appreciable changes in volume may occur if the pressure or temperature is altered.
In this graph, you can see compressibility factor vs pressure:
⚡️However, if the percentage change in the pressure or in the absolute temperature is small, for practical purposes a gas may also be regarded as incompressible. Thus, in practice, volume changes are likely to be important only when the pressure or temperature of a gas changes by a large proportion.
☀️The relation between pressure, temperature, and volume of a real gas is generally complex though, except at very high pressures the behavior of gases approximates to that of the ideal gas for which the volume of a given mass is inversely proportional to the pressure and directly proportional to the absolute temperature.
Flow of Fluids 🌊
The behavior of a fluid under the action of a shear stress is important in that it determines the way in which it will flow. The most important physical property affecting the stress distribution within the fluid is its viscosity. (📌In the future, we will talk about it with details*)
For a gas, the viscosity is low and even at high rates of shear, the viscous stresses are small. Under such conditions the gas approximates in its behavior to an inviscid fluid. In many problems involving the flow of a gas or a liquid, the viscous stresses are important and give rise to appreciable velocity gradients within the fluid, and dissipation of energy occurs as a result of the frictional forces set up.
🖇In gases and in most pure liquids the ratio of the shear stress to the rate of shear is constant and equal to the viscosity of the fluid. These fluids are said to be Newtonian in their behavior.
However, in some liquids, particularly those containing a second phase in suspension, the ratio is not constant and the apparent viscosity of the fluid is a function of the rate of shear. The fluid is then said to be non-Newtonian and to exhibit rheological properties. The importance of the viscosity of the fluid in determining
velocity profiles and
friction losses
will be discussed in future's posts. The effect of pressure on the properties of an incompressible fluid, an ideal gas, and a non-ideal gas is now considered.
The incompressible fluid, ideal and non-ideal gas
By definition, v is independent of P, so that (dv/dP)T = 0. The internal energy will be a function of temperature but not a function of pressure.
The ideal gas: An ideal gas is defined as a gas whose properties obey the law:
💡where V is the volume occupied by n molar units of the gas, R the universal gas constant, and T the absolute temperature. Here n is expressed in kmol when using the SI system. This law is closely obeyed by real gases under conditions where the actual volume of the molecules is small compared with the total volume, and where the molecules exert only a very small attractive force on one another.
🎾These conditions are met at very low pressures when the distance apart of the individual molecules is large. The value of R is then the same for all gases and in SI units has the value of 8314 J/kmol* K.
Non-ideal gas: Compressibility factor Z which is a function of both temperature and pressure will be included in ideal gas equation:
✅PV = Z*nRT
At very low pressures, deviations from the ideal gas law are caused mainly by the attractive forces between the molecules and the compressibility factor has a value less than unity. At higher pressures, deviations are caused mainly by the fact that the volume of the molecules themselves, which can be regarded as incompressible, becomes significant compared with the total volume of the gas. Many equations have been given to denote the approximate relation between the properties of a non-ideal gas. Of these the simplest, and probably the most commonly used, van der Waals' equation:
References 📖
Coulson&Richardson, Chemical Engineering Design Volume 1
DODGE, B. F.: Chemical Engineering Thermodynamics (McGraw-Hill, New York, 1944).
DE NEVERS, N.: Fluid Mechanics for Chemical Engineers, 2nd edn (McGraw-Hill, New York, 1970).
DOUGLAS, J. F.: Solution of Problems in Fluid Mechanics (Pitman, London, 1971).
MASSEY, B. S.: Mechanics of Fluids, 6th edn (Chapman and Hall, London, 1989).
MILNE-THOMSON, L. M.: Theoretical Hydromechanics (Macmillan, London, 1968). SCHLJCHTING, H.
Boundary Layer Theory, 5th ed (McGraw-Hill, New York, 1968).
SMITH, J. M. and VAN NESS, H. C.: Introduction to Chemical Engineering Thermodynamics, 5th ed (McGrawHill, New York, 1995).
Additional Resources 🧪
🔑You can get deep insight about Process/Chemical Engineering from these sources😉:
https://t.me/chemicalengineeringworld_cew- Everything related to Chemical Engineering
https://t.me/ebookgate- Chemical Engineering E-books (Telegram Channel)
https://www.youtube.com/channel/UCqioh32NOJc8P7cPo3jHrbg- Piping Analysis
https://www.youtube.com/channel/UCQfMyugsjrVUWU0v_ZxQs2Q -Mechanics of engineered devices
http://chemicalengineeringguy.com/- suggests a wide range of courses in Chemical engineering (you can find free courses on topic of Aspen HYSYS, Aspen Plus)
https://www.youtube.com/user/LearnEngineeringTeam- suggests working principles of every engineered devices, equipment and etch.
https://www.youtube.com/channel/UCR0EfsRZIwA5TVDaQbTqwEQ- suggests great information about pumps, compressors with animation.
🔌Today we have already learned about whole Flow of Fluid part 1, Types of Fluid, Compressibility factor, tomorrow‘s post we will continue flow in motion, now time to say goodbye👋🏻 until tomorrow and Stay tuned for more content 😉🌝✨!
✏️Note: If you need one of those books or links, you can contact me via my email or LinkedIn profile.
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