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Moment of Momentum Equation

Posted by: Engineers Zone Posted date: Sunday, November 28, 2010 / comment : 0 , ,

Moment of momentum equation is derived from moment of momentum principle, which states that the resulting torque acting on a rotating fluid is equal to the rate of change of moment of momentum.

Moment of momentum per second = rQ x V x r

Where r = density of fluid

Q = rate of flow of fluid

V = velocity of fluid

r = radius of curvature

Continuity Equation

Posted by: Engineers Zone Posted date: Sunday, November 28, 2010 / comment : 0 , ,

The equation based on the principle of conservation of mass is called continuity equation.

r1A1V1 = r2A2V2

Where V = Average velocity

r = Density

A = Area of pipe

If the fluid is incompressible, then r1=r2 and continuity equation reduces to A1V1 = A2V2

Types of fluid

Posted by: Engineers Zone Posted date: Sunday, November 28, 2010 / comment : 0 , ,


The fluids may be classified into the following five types:
a. Ideal fluid – A fluid, which is incompressible and is having no viscosity, is known as an ideal fluid. Ideal fluid is only an imaginary fluid as all the fluids, which exist, have some viscosity.
b. Real fluid – A fluid, which possesses viscosity, is known as real fluid. All the fluids, in actual practice, are real fluids.
c. Newtonian fluid – A real fluid, in which the shear stress is directly proportional to the rate of shear strain (or velocity gradient), is known as Newtonian fluid.
d. Non-Newtonian fluid – A real fluid, in which the shear stress is not proportional to the rate of shear strain, is known as non-newtonian fluid.
e. Ideal Plastic fluid – A fluid, in which shear stress is more than the yield value and shear stress is proportional to the rate of shear strain, is known as ideal plastic fluid.

Water Chiller

Posted by: Engineers Zone Posted date: Friday, November 26, 2010 / comment : 0 ,

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Water chillers are used in a variety of air conditioning and process cooling applications. They are used to make cold water that can be transported throughout a facility using pumps and pipes. This cold water can be passed through the tubes of coils in order to cool the air in an air conditioning application or it can provide cooling for a manufacturing or industrial process.
Systems that employ water chillers are commonly called chilled water
systems.

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There are several types of water chillers that are differentiated by the
refrigeration cycle they use or the type of compressor.

Absorption water chillers make use of the absorption refrigeration cycle and donot have a mechanical compressor involved in the refrigeration cycle. Absorption water chillers are the subject of a separate clinic.

Water chillers using the vapor-compression refrigeration cycle vary by the type of compressor used. Reciprocating and scroll compressors are typically used in smaller chillers. Helical-rotary (or screw) compressors are typically used in medium-sized chillers. Centrifugal compressors are typically used in larger chillers.

Source : Trane Guide

Classification Of Pumps

Posted by: Engineers Zone Posted date: Tuesday, November 23, 2010 / comment : 0 , ,

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Source : Alfa Laval Pump Handbook

What is a Pump?

Posted by: Engineers Zone Posted date: Tuesday, November 23, 2010 / comment : 0 , ,

There are many different definitions of this but it can be best described as:

‘A machine used for the purpose of transferring quantities of fluids and/or gases, from one place to another’.

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A TYPICAL PUMP INSTALLATION

This is illustrated below transferring fluid from tank A to spray nozzles B.

Pump types generally fall into two main categories – Rotodynamic and Positive Displacement, of which there are many forms.

The Rotodynamic pump transfers rotating mechanical energy into kinetic energy in the form of fluid velocity and pressure. The Centrifugal and Liquid Ring pumps are types of rotodynamic pump, which utilise centrifugal force to transfer the fluid being pumped.

The Rotary Lobe pump is a type of positive displacement pump, which directly displaces the pumped fluid from pump inlet to outlet in discrete volumes.

Bernoulli’s Theorem

Posted by: Engineers Zone Posted date: Thursday, November 18, 2010 / comment : 4 , ,

It states that in a steady state, ideal flow of an incompressible fluid, the total energy at any point of the fluid is constant.  The total energy consists of pressure energy, Kinematic energy and potential energy or datum energy.

Assumptions:
a.       The fluid is ideal, i.e. viscosity is zero
b.       The flow is steady
c.        The flow is incompressible
d.       The flow is irrotational

Bernoulli’s Equation for Real Fluid:
The Bernoulli’s equation was derived on the assumption that fluid is inviscid (non-viscous) and therefore frictionless.  But all the real fluids are viscous and hence offer resistance to flow.  Thus there are always some loses in fluid flows and hence in the application of Bernoulli’s equation, these loses have to be taken into consideration.  Thus the Bernoulli’s equation for real fluids between point 1 and 2 is given by
                p1  +  v1  +  z1  =  p2  +  v2  + z2  +  hL
                     rg        2g                    rg         2g
where hL is loss of energy between point 1 and 2.

Practical Applications of Bernoulli’s Equation:
Bernoulli’s equation is applied in all problems of incompressible fluid flow where energy considerations are involved.
  1. Venturimeter.
  2. Orifice meter
  3. Pitot-tube
Venturimeter and Orifice Meter:
Both the devices are used for measuring the rate of a flow of a fluid flowing through a pipe. 

Pitot Tube:
It is a device used for measuring the velocity of flow at any point in a pipe or a channel.

Types of Fluid Flow:

Posted by: Engineers Zone Posted date: Thursday, November 18, 2010 / comment : 11 , ,


  •       Steady and unsteady flow.
  •       Uniform and non-uniform flow.
  •       Laminar and turbulent flow.
  •       Compressible and incompressible flow.
  •       Rotational and irrotational flow.
  •       One, two and three-dimensional flows.


Steady and Unsteady flow:
Steady flow is defined as that type of flow in which the fluid characteristics like velocity, pressure, density, etc. at a point do not change with time.
Unsteady flow is that type of flow, in which the velocity, pressure or density at a point changes with respect to time.

Uniform and Non-uniform flow:
Uniform flow is defined as that type of flow in which the velocity at any given time does not change with respect to space (i.e., length of direction of the flow).
Non-uniform flow is that type of flow in which the velocity at any given time changes with respect to space.

Laminar and Turbulent flow:
Laminar flow is defined as that type of flow in which the fluid particles move along well-defined paths or streamline and all the streamlines are straight and parallel.  Thus the particles move in laminas or layers gliding smoothly over the adjacent layers.  This type of flow is also called as streamline flow or viscous flow.
Turbulent flow is that type of flow in which the fluid particles move in zigzag way.  Due to the movement of fluid particles in a zigzag way, the eddies formation takes place which are responsible for high-energy loss.  For a pipe flow, the type of flow is determined by a non-dimensional number called the Reynold number.
If the Reynold number is less than 2000, the flow is laminar.  If the Reynold number is more than 4000, it is called turbulent flow.  It the Reynold number lies between 2000 and 4000, the flow may be laminar or turbulent.

Compressible and Incompressible flows:
Compressible flow is that type of flow in which the density of the fluid changes from point to point or in other words the density is not constant for the fluid.
Incompressible flow is that type of flow in which the density is constant for the fluid flow.  Liquids are generally incompressible while gases are compressible.

Rotational and Irrotational flows:
Rotational flow is that type of flow in which the fluid particles while flowing along streamlines also rotate about their own axis.
And if the fluid particles while flowing along the streamlines, do not rotate about their own axis that type of flow is called irrotational flow.

One, Two and Three-Dimensional flows:
One-dimensional flow is that type of flow in which the flow parameter such as velocity is a function of time and one space co-ordinate only.  For a steady one-dimensional flow, the velocity is a function of one-space-co-ordinate only.  The variation of velocities in other two mutually perpendicular directions is assumed negligible.
Two-dimensional flow is that type of flow in which the velocity is a function of time and two rectangle space co-ordinates.  For a steady two-dimensional flow the velocity is a function of to space co-ordinates only.  The variation of velocity in the third direction is negligible.
Three-dimensional is that type of flow in which the velocity is a function of time and three mutually perpendicular directions.  But for a steady three-dimensional flow the fluid parameters are functions of three space co-ordinates.
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