Reverse Osmosis

Reverse osmosis (RO) is a water purification method that uses a semipermeable membrane to remove ions, molecules, and sediments from water to make it drinkable. In reverse osmosis process, pressure applied with pump to overcome osmotic pressure. Reverse osmosis can remove many types of dissolved and suspended particles or species from water, including bacteria, sediments etc. and is used in both industrial processes and the production of potable water. The result is that the solute is retained on the pressurised side of the membrane and the pure solvent is allowed to pass to the other side of the membrane. To be selective, this membrane should not allow large molecules or ions through the pores or holes, but should allow smaller components of the solution such as solvent molecules to pass freely.

In the normal osmosis process, the solvent naturally moves from an area of low solute concentration or high water potential through a membrane, to an area of high solute concentration or low water potential. The driving force for the movement of the solvent is the reduction in the free energy of the system when the difference in solvent concentration on either side of a membrane is reduced, generating osmotic pressure due to the solvent moving into the more concentrated solution. Applying an external pressure to reverse the natural flow of pure solvent, thus, is reverse osmosis. The process is similar to other membrane technology applications. However, key differences are found between reverse osmosis and filtration. Reverse osmosis also involves diffusion, making the process dependent on pressure, flow rate, and other conditions. Reverse osmosis is most commonly known for its use in drinking water purification from seawater, removing the salt and other effluent materials from the water molecules.

Steam Turbine

Steam Turbine

A Steam Turbine is a rotary mechanical device (turbo machine) that extracts energy from fluid flow and converts it into useful work. Turbine has a moving part called rotor assembly, which is a shaft or drum with blades attached on it. High velocity moving fluid acts on blades so that they impart rotational energy to the rotor. Turbines have a casing around the blades that contains and controls the working fluid.A working fluid contains potential energy (pressure head) and kinetic energy (velocity head). The fluid may be compressible or incompressible.

Steam turbines are used for the generation of electricity in thermal power plants, such as plants using coal, fuel oil or nuclear fuel.

Classification of Steam Turbine:

According to the working principle:

Impulse Turbine

Reaction Turbine

According to the number of Cylinder:

Single Cylinder Turbine

Double Cylinder Turbine

According to the method of Governing:

Throttle Governing Turbine

Nozzle Control Governing Turbine

Bypass Governing Turbine

According to Steam Pressure:

Low Pressure Turbine (1.2 to 2 kg/cm²)

Medium Pressure Turbine (up to 40 kg/cm²)

High Pressure Turbine (40 to 170 kg/cm²)

Very High Pressure Turbine (170 to kg/cm²or higher and temperature of 550 ºC)

Supercritical Turbine (225 kg/cm²)

According to shaft Arrangement:

Cross Compound Turbine

Tandem Compound Turbine

According to Direction of Flow:

Single Flow Turbine

Double flow Turbine

Reverse Flow Turbine

According to the Direction of Steam Flow:

Axial Turbine

Radial Turbine

Power Plant Engineering

Basic Definition of Power Plant Engineering

Load Curve: A consumer of electrical power will use the power as and when required, and hence the load always be changing with time.

Cavitation

Cavitation is the formation of vapour cavities in liquid to form bubbles or voids that are consequence of forces acting upon the liquid.

Basic Effects of Fluid Properties

The effects of temperature and pressure on hydraulic system fluid properties and flow characteristics are listed below:

Density - Effects orifice and valve volume flow rates. As density increases, orifice and valve flow rates will decrease (see orifice flow equations).

a)     Increasing pressure increases density

b)     Increasing temperature decreases density

Kinematic Viscosity – Effects pipe (tube) volumetric flow rate. As viscosity increases, pipe flow rate will decrease (see orifice flow equations). Kinematic viscosity increases with increased pressure and decreasing temperature.

a)     Increasing pressure increases kinematic viscosity

b)     Increasing temperature decreases kinematic viscosity

Bulk Modulus - Effects compressibility of fluid and system response time (see pressure derivative equation). As bulk modulus decreases, the pressure derivative will decrease leading to slower response times. Compressibility will affect the performance of actuators, motors and pumps because the stiffness of the fluid is less as bulk modulus is reduced.

a)     Increasing pressure increases bulk modulus

b)     Increasing temperature decreases bulk modulus

HOW PUMPS WORK

HOW PUMPS WORK

In dynamic machines there is no closed volume, instead rotating blades supply or extract energy to or from the fluid. For pumps, these rotating blades are called impeller. For incompressible flow it is more common to use volume flow rate rather than mass flow rate. Volume flow rate is called capacity and is simply mass flow rate divided by fluid density.

PRINCIPLES OF SUPERCHARGING AND TURBOCHARGING

To better understand the technique of turbo charging, it is useful to be familiar with the internal combustion engine's principles of operation. Today, most passenger car and commercial diesel engines are four-stroke piston engines controlled by intake and exhaust valves. One operating cycle consists of four strokes during two complete revolutions of the crankshaft.