Driving force for fluid flow

Driving forceforfluid flow

Driving forcefor fluid flow is Energy per unit mass or total head available at the point of location.

Justification:

If you observe the flow in venturi meter, it will become more clear. consider 3 points as shown in the below figure.

Assume P1, P2, P3 are pressures at 1, 2 and 3 points. Here according to cross section area variation we can say P1 > P2 < P3. It shows that P3 > P2 but fluid is moving from 2 point to 3 point, so we can say pressure is not thedriving force. Similarly we can say velocity is also not thedriving force.Why distillation? Why not adsorbption or leaching ?

Indistillationthenew phasegenerated is different from the original by phase, or heat content only. This heat can be removed or added by easy operations. But in case of adsorption or leaching the a foreignsubstanceis introduced to separate the phases. Thenew phasegenerated using these processes is a new solution which in turn may be separated using other separation methods unless the new solution is directly useful. This makes thedistillationprocess to more economical.

Distillationprocess depends on the relative volatilities of the components. If the difference is too low separation is difficult and it makes the process as more expensive.When reflux ratio to the column is minimum and zero, what are the requirements in columnWhenreflux ratio is minimum, column requiresmaximumnumber of trays and minimum reboiler load fora requiredseparation. To avoid this problem of infinite trays we use optimum reflux ratio.Define Intensive and extensive properties, give examples for themIntensive and Extensive properties:

Extensive property:Is defined as one which depends onquantityof matter specified in the system.

Examples: Total mass, volume, Energy, enthalpy,

Intensive property:

It is defined as one which depends on thequantityof matter present in the sysytem.

Examples: Temperature, pressure,Molar enthalpy, molar vWhat is jigging and where it is used ?Jigging:

Jigging isa separationmethod in which the particle are separated by using the density difference between them.

Jiggingis a method of gravitational preparation of natural resources, based onseparationof mineral mixture on density in verticallyoscillatingwater stream.

Usually it is used to separate metal slag form metals.What is Differential Distillation, Simple Distillation, Rayleigh distillation,Rayleigh equation, material Balance equation

DifferentialDistillation:

Simpledistillation, also known asRayleighdistillationordifferentialdistillation, is the most elementary example of batchdistillation. In thisdistillationsystem, the vapor is removed from thestill during a particular time interval and is condensed in the condenser. The more volatile component is richer in the vapor than in the liquid remaining in the still. Over time, the liquid remaining in the still begins to experience a decline in the concentration of the more volatile component, while the distillate collected in the condenser becomes progressively more enriched in the more volatile component.

Schematic representation ofdifferentialdistillationis as shown in in fig.1

Fig:1Differentialdistillation

No reflux is returned to the still, and no stages or packing materials are provided inside the column; therefore, the various operating approaches are not applicable to this distillation system. The early analysis of this process for abinary system, proposed byRayleighis given below. Let F be the initial binary feed to the still (mol) and xFbe the mole fraction of the more volatile component (A) in the feed. Let B be the amount of compound remaining in the still, xBbe the mole fraction of component A in the still, and xDbe the mole fraction of component A in the vapor phase. Thedifferentialmaterialbalancefor component A can then be written as:

xDdB = d ( B xB) = B dxB+ xBdB

Upon integration:

or

In this simpledistillationprocess, it is assumed that the vapor formed within a short period is in thermodynamic equilibrium with the liquid; hence, the vapor composition (xD) is related to the liquid composition (xB) by an equilibrium relation ofthe formxD= F(xB). The exact relationship for a particular mixture may be obtained from a thermodynamic analysis depending on temperature and pressure. For a system following the ideal behavior given by Raoults law, the equilibrium relationship between the vapor composition y (or xD) and liquid composition X (or xB) of the more volatile component in a binary mixture can be approximated using the concept ofconstantrelativevolatility(), which is given by:

Substitution of the above equation in Equation (2)

Although the analysis of simpledistillationhistorically represents the theoretical start of batchdistillationresearch, a complete separation using this process is impossible unless the relativevolatilityof the mixture is infinite. Therefore,the applicationof simpledistillationis restricted to laboratory-scaledistillation, where high purities are not required, or when the mixture is easily separable.what is a first order system and what physical phenomena give rise to first order system(It's transfer function)?WHAT IS A FIRST-ORDER SYSTEM?

A first-order system is one whose output, y(t), is modeled by a first order,linear differential equation

Define,

pis known as thetimeconstantof the processand KP is called thesteady state gainorstatic gainor simply thegainof the process.From eqn, it is easily found that thetransfer functionof a firstorder process is given by;

A first-order process with atransfer functiongiven by above eqn. is also known as:first-order lag, linear lag, exponentialtransferlag.

If on the other hand, a0 = 0, then from eqn.we take

which gives atransfer function

In such case the process is calledpurely capacitive or pure integrator

where f(t) is the input (forcingfunction). If a0 # 0, then above eqation yields,

Dew Point:

It is the temperature at which the partial pressure of the water vapour in the mixtureis equalto the vapour pressure of water. It can also be defines as, the temperature where condensate formation will start upon constant cooling of vapour mixture .

Dew pointis a saturation temperature

Dew pointis always lower than or equal to the dry bulb temperature.

Dew pointis always lower than or equal to the wet-bulb temperature.

At 100% saturation :

Dry bulb temperature = wet bulb temperature =Dew point.What is volute in centrifugal pump, uses of volute in centrifugal pump

Centrifugal pumpis as shown in thefigure.

In thisfigureobserve the vanes shape and impeller direction.

Volute:It is the gap between the casing and the impeller. There are two uses with volute of thecentrifugal pump.1. In this volute kinetic energy is converted into pressure energy. As the cross section area increases, the volute reduces the velocity of the liquid and increases the pressure of the liquid.2. One of the main purposes of a volute casing is to help balance the hydraulic pressure on the shaft ofthe pump. However, this occurs best at the manufacturer's recommended capacity. Running volute-style pumps at a lower capacity than the manufacturer recommends can put lateral stress on the shaft ofthe pump, increasing wear-and-tear on the seals and bearings, and on the shaft itself.

Centrifugal pumps are used for large discharge through smaller heads.What are differences between pipe and tube,Birmingham wire gauge,schedule numberPipes and tubesare specified in terms of their diameter and wall thickness.Pipes: Heavy walled Relatively large in diameter comes in moderate lengths (20 to 40 ft) Threading is not possible Pipe walls are rough Lengths of pipes are joined by screwed, flanged and welded fittings Made by welding , casting, or piercing abilletin a piercing mill The wall thickness ofthe pipeis indicated usingschedulenumber Size ofthe pipeis indicated as nominal diameterTubes: Thin walled Less diameter available in the form of coils also, several hundred meters Can be threaded Tube walls are smooth These are joined by compression fittings, flare fittings, or soldered fittings These can be cold drawn Tube thickness is indicated usingBWG (Birminghamwire gauge) Size of the tube is indicated as outside diameter NPSHis an acronym forNet PositiveSuctionHead. In any cross-section of a generichydraulic circuit, the NPSH parameter shows the difference between the actual pressure of a liquid in a pipeline and the liquid's vapor pressure at a given temperature.

NPSH is an important parameter to take into account when designing a circuit: whenever the liquid pressure drops below the vapor pressure, liquid boiling occurs, and the final effect will be cavitation: vapor bubbles may reduce or stop the liquid flow, as well as damage the system.

Considering the circuit shown in the picture

wherehLis the head loss between 0 and 1p0is the pressure at thewater surfacepvis thevapour pressure(saturation pressure) for the fluid at the temperatureT1at 1zis the difference in heightz1z0(shown as H on the diagram) from thewater surfaceto the location 1is the fluid densitygis gravitational acceleration