Properties of Fluids in Fluid Mechanics

Properties of Fluids in Fluid Mechanics

The various properties of fluids in fluid mechanics are mass density, weight density, specific volume, specific gravity, viscosity. Lets understand these properties of fluids one by one in detail. The knowledge of these properties is very essential to make the study of fluid mechanics comprehensive.

Properties of fluids in fluid mechanics


The properties of fluids are as follows

1. Density or mass density
2. Specific weight or Weight density
3. Specific volume
4. Specific Gravity
5. Viscosity

1. Density or Mass Density:

It is defined as the ratio of the mass of the fluid to its volume.

  • It is represented by the symbol  ρ (rho).
  • The unit of density is Kg per cubic metre (Kg/m3)
  • The density of liquid is taken as constant while the density of the gases changes with the change in the pressure and temperature

.In mathematical form the density is given as

Properties of Fluids in Fluid Mechanics



  • The value of the mass density for the water is 1000 Kg/m3.

2. Specific Weight or Weight Density

When the ratio of weight of the fluid to the volume of the fluid is taken out and the quantity that obtained after that is called specific weight or weight density.

  • In other words the weight per unit volume is called weight density.
  • It is denoted by the symbol w


Mathematically it is written as

Properties of Fluids in Fluid Mechanics

  • The value for the specific weight or weight density of water is 9.81 x 1000 N/m3



3. Specific gravity:

It is the ratio of weight density of a fluid to the weight density of a standard fluid .

  • Water is taken as the standard fluid for liquids and for gases it is air.
  • Specific gravity is also known as relative density.
  • The specific gravity is represented by the symbol ‘S’.


Mathematically

Properties of Fluids in Fluid Mechanics


From this
Weight density of a liquid = S X Weight density of water

  • The specific gravity of mercury is 13.6


4. Specific Volume:

The volume occupied by a unit mass is called specific volume. In other words it is the volume per unit mass.

Mathematically

Properties of Fluids in Fluid Mechanics

5. Viscosity

It is the property of the fluid which offers resistance to the movement of a fluid over another adjacent layer of fluid.

  • It is denoted by the symbol μ.


Mathematically

Properties of Fluids in Fluid Mechanics


Where
τ = shear stress
du/dy = shear strain or rate of shear deformation or velocity gradient


In this article I have tried to explain you about the various properties of fluids in fluid mechanics. I hope that you have got an idea about these properties. If you find anything incorrect or missing than don't forget to comment us.



Difference Between Renewable and Non-renewable Resources

Renewable energy resources: The energy resources which cannot be exhausted and can be used again and again are called renewable energy resources. For example solar energy, wind energy, tidal energy and hydroelectric etc.

Non-renewable energy resources: The energy resources which can be exhausted one day and cannot be used repeatedly are called non-renewable energy resources. The example of non-renewable energy resources are coal, petroleum, natural gases etc.



Difference between Renewable and Non-renewable Resources

The comparison between renewable and non-renewable resources are given below in tabular form


S.No
Renewable energy 
resources
Non-renewable energy resources
1.
It can be used again and again throughout its life.
It cannot be used again and again but one day it will be exhausted.
2.
These are the energy resources which cannot be exhausted.
They are the energy resources which can be exhausted one day.
3.
 It has low carbon emission and hence environment friendly.
It has high carbon emission and hence not environment friendly.
4.
It is present in unlimited quantity.
It is present in limited quantity and vanishes one day
5.
Cost is low
Cost is high.
6.
Renewable energy resources are pollution free.
The non-renewable energy resources are not pollution free.
7.
Life of resources is infinite.
Life of resources is finite and vanishes one day.
8.
It has high maintenance cost.
It has low maintenance cost as compared with the renewable energy resources.
9.
Large land area is required for the installation of its power plant.
Less land area is required for its power plant installation.
10.
Solar energy, wind energy, tidal energy etc are the examples of renewable resources.
Coal, petroleum, natural gases are the examples of non-renewable resources

Summary of Renewable vs Non-renewable Resources

  • The renewable energy resources can be depleted and used again and again. But the non-renewable resources are limited in number and can be depleted one day.
  • The carbon emission in renewable energy resources are very low and prevent global warming. In non-renewable resources the carbon emission is large and contributes in global warming.
  • The renewable resources are cheaper and present in unlimited quantity but the non- renewable resources are costlier and present in limited quantity.
  • The life of renewable resources is infinite. In case of non-renewable resources the life is finite.
  • The maintenance cost for the power plant of renewable energy resources is low but it is high in the case of non-renewable energy resources.
  • Solar energy, wind energy, tidal energy and geothermal energy are called as renewable resources. Coal petroleum, natural gas, are called non-renewable resources.


This is all about the difference between renewable and non-renewable resources. If you find anything missing or incorrect then please let me know it through your commenting.


Difference Between Fire Tube Boiler and Water Tube Boiler

The difference between fire tube boiler and water tube boiler can be done on various points. These points includes types of fluid flows within the tubes, steam generation rate, floor area required for the steam generation, transportation, efficiency, fluctuating loads, operating cost etc. the knowledge of the difference about these two boiler is very crucial.

Difference Between Fire Tube Boiler and Water Tube Boiler

Difference Between Fire Tube Boiler and Water Tube Boiler 

S.no
Fire tube boiler
Water tube boiler
1.
In this boiler the hot flue gases is present inside the tubes and water surrounds them
The water is present inside the tubes and the hot flue gases surrounds them
2.
They are low pressure boilers. The operating pressure is about 25 bar.
They are high pressure boilers and the operating pressure is about 165 bar.
3.
The steam generation rate in fire tube boiler is low, i.e.9 tonne per hour.
Steam generation rate in water tube boiler is high i.e. 450 tonne per hour.
4.
For a given power the floor area required for steam generation is more i.e. 8 m2 per tonne per hour.
The floor area required for the steam generation is less, i.e. 5 m2 per tonne per hour.
5.
The transportation and erection in this type of boiler is difficult.
The transportation and erection is easy as its parts can be separated.
6.
The overall efficiency of this boiler is upto 75%.
The overall efficiency is upto 90% with the economizer.
7.
It can works on fluctuating loads for shorter period of time.
It works on fluctuating loads all the times.
8.
The direction of water circulation in fire tube boiler is not well defined.
The direction of water circulation in water tube boiler is well defined i.e. a definite path is provided for the circulation of water.
9.
Operating cost is low.
Operating cost is high.
10.
Bursting chance is less in firetube boiler.
Bursting chance in water tube boiler is more.
11.
Due to bursting, there is a greater risk to the damage to the boiler.
The bursting in this boiler does not produce any major destruction to the whole boiler.
12.
It can be operated with less skilled person.
A skilled person is required to operate this boiler.
13.
Low maintenance cost.
High maintenance cost.
14.
They are light in weight.
They are heavy in weight.
15.
It is suitable for small power plant.
It is suitable for large power plant.
  

Fire tube boiler vs water tube boiler

Fire tube boiler

  • It is a boiler in which the hot flue gases is present inside the tubes and the water surrounds these tubes. As fire is present insides the tubes, hence it is called as fire tube boiler.
  • The steam produced by these boilers have pressure of about 25 bar and that’s why they fall under the category of low pressure boilers.
  • The steam generation rate in these boilers are low i.e. 9 tonnes per hour.
  • For a given power the floor area required for steam generation is more and it is about 8 m2 per tonne per hour.
  • The erection and transportation of these boilers are not easy. And this is because their parts cannot be separated.
  • If we talk about the efficiency then the overall efficiency of fire tube boilers is about 75%.
  • The direction of the water circulation is not well defined i.e. a definite path is not provided for the circulation of water.
  • The operating cost of this boiler is low.
  • The bursting chance is less. The bursting produces greater risk to the damage of the boiler.
  • It is not suitable for large power plants but used in small power plants.
Also Read: Lancashire Boiler Construction, Working with Diagram

Water tube boiler

  • It is a boiler in which the water is present inside the tubes and the hot flue gases surrounds the tubes. Since the water is present insides the tubes hence these boilers are called water tube boiler.
  • High pressure steam is produced by these boilers. The pressure of the steam is about 165 bar. These boiler falls under the category of high pressure boiler.
  • The steam generation rate in water tube boiler is high i.e. 450 tonnes per hour.
  • For a given power the floor area required for the generation of steam in this boiler is less i.e. 5 m2 per tonne per hour.
  • The erection and transportation is easy as its parts can be separated.
  • The overall efficiency of water tube boiler with economizer is upto 90%.
  • The direction of the water circulation is well defined i.e. a definite path is provided for the circulation of water.
  • The operating cost is high.
  • The bursting chance is high because of its high steam pressure. The bursting does not cause any destruction to the whole boiler.
  • It is suitable for the large power plant.

Difference Between Intensive and Extensive Properties

The properties are mainly divided into intensive and extensive properties. Any property may be either intensive or extensive. Before discussing these properties let’s come to know about what is property. Any characteristic of a system is called property. For example: pressure, temperature, volume and mass are some familiar properties of a system. Viscosity, thermal conductivity, modulus of elasticity thermal expansion coefficient, electrical resistivity etc are less familiar properties.

Difference Between Intensive and Extensive Properties


Properties are considered to be either intensive or extensive. Let’s discuss about intensive and extensive properties one by one


Intensive properties: The properties which are independent of the mass of the system. Temperature, pressure and density are the intensive properties.

Extensive properties: The properties which depend on the size or extent of the system are called extensive properties. For example: total mass, total volume and total momentum.

For better explanation of the intensive and extensive properties considered a system in which the properties like mass, volume temperature, pressure and density are denoted by ‘m’, ‘V’, ‘T’, ‘P’, ‘ρ’.If the system is divided into two parts then what changes takes place is shown in the diagram below.

Difference Between Intensive and Extensive Properties

Here the mass and volume becomes half but the pressure temperature and density remains unchanged as the system is divided into two halves. This indicates that mass and volume depends upon the size or extent of the system and hence they are extensive properties. And the pressure, temperature and density remains unchanged that is they are independent of the mass and that’s why are called intensive property.

Difference between intensive and extensive properties


S.no
Intensive property
Extensive property
1.
They are independent of the quantity of the system.
They depend upon the quantity of the system
2.
They are independent of the size or extent of the system.
They depend upon the size and extent of the system.
3.
Pressure, temperature and density are intensive properties etc
Total Mass, total volume, total momentum etc.

How to Identify Whether a Property is Intensive or Extensive


Considered a system and measure some of its properties like mass, volume, temperature density etc. Note down the value of each property on a paper. Now make the quantity of the system double. Now again measure all the properties of the system that we have measured earlier. And compare the values

  • If the value any property exchanges than it is an extensive property
  • And if it remains unchanged than it is an intensive property.



Thermodynamic System - Types of Thermodynamic System

Thermodynamic system


A thermodynamic system is defined as a quantity of matter or a region in space which is selected for the study. The mass or region outside the system is called surroundings. The real or imaginary surfaces which separates the system and surroundings is called boundary. The boundary of a system can be fixed or movable.

Thermodynamic System - Types of Thermodynamic System



To understand the system, surroundings and the boundary in far better way let’s take an example. Considered a closed vessel on which we are going to do our study. Since we are doing our study on the vessel so it is the system and the region excluding the closed vessel is called as surroundings. The surface of the closed vessel that separates the vessel and surroundings is called boundary. Finally anything on which we pay our attention for the study or analysis is called system.

Types of thermodynamic system


On the basis of mass and energy transfer the thermodynamic system is divided into three types.

1.Closed system
2.Open system
3.Isolated system


Closed system: A system in which the transfer of energy but not mass can takes place across the boundary is called closed system. The mass inside the closed system remains constant.
Thermodynamic System - Types of Thermodynamic System

For example: Boiling of water in a closed vessel. Since the water is boiled in closed vessel so the mass of water cannot escapes out of the boundary of the system but heat energy continuously entering and leaving the boundary of the vessel. It is an example of closed system.


Open system: A system in which the transfer of both mass and energy takes place is called an open system. This system is also known as control volume.
Thermodynamic System - Types of Thermodynamic System

For example: Boiling of water in an open vessel is an example of open system because the water and heat energy both enters and leaves the boundary of the vessel.


Isolated system: A system in which the transfer of mass and energy cannot takes place is called an isolated system.
Thermodynamic System - Types of Thermodynamic System

For example: Tea present in a thermos flask. In this the heat and the mass of the tea cannot cross the boundary of the thermos flask. Hence the thermos flak is an isolated system. 

Here we have studied about what is thermodynamic system and different types of thermodynamic system. whatever we have discussed above keeps an important role in the study of subject thermodynamic. If anyone does not know about these topics then it becomes very difficult to understand the thermodynamic subject. if you find anything missing in that then don't forget to comment.



Difference Between Metals and Nonmetals

In this article we will go to learn about difference between metals and nonmetals.There are so many metals and non-metals present in our environment. And these have a wide variety of application. They are used in various industries throughout the world. The knowledge of these metals and non-metals is very crucial to everyone. Here I am going to discuss the difference among them. I hope that you will like it.

Difference between Metals and Nonmetals

Difference Between Metals and Nonmetals

  • The metals are generally present in the solid form at room temperature except mercury which is liquid at room temperature. Whereas non-metals may be solid, liquid and gaseous at room temperature.
  • Metals are good conductors of heat and electricity but non-metals are poor conductors of heat and electricity.
  • Metals are ductile in nature i.e. it can be drawn into thin wires. But non-metals are not ductile.
  • Metals are malleable but non-metals are not malleable. Malleable means the property through which metals can be hammered into thin sheets.
  • Metals are lustrous i.e. having shinning appearance but non-metals are dull in appearance.
  • Metals contain 1 to 3 electrons in their outermost shell whereas non-metals contain 4 to 8 electrons in their outermost shell.
  • Metal loses electrons to form electropositive ions but non-metals accept electrons to form electronegative ions.
  • Metals have low ionization enthalpy and non-metals have high ionization enthalpy.
  • Metals react with oxygen to form basic oxides whereas non-metals usually react with oxygen to form acidic oxides.
  • Metals are good reducing agent as it loses electrons easily from its valance shell. But non-metals are good oxidizing agent as it accepts electrons in its outermost shell.
  • Metals are sonorous in nature i.e. produces sound when hit by an object. but non-metals does not produces any sound.

Table for the difference between metals and nonmetals

S.no
Metals
Non-metals
1
They are solid at room temperature except mercury which is liquid at room temperature.
They may be solid, liquid and gaseous at room temperature.
2
Good conductors of heat and electricity.
Poor conductors of heat and electricity.
3.
They have shining appearance i.e. lustrous
They are non-lustrous i.e. having dull appearance.
4.
They have ductility i.e. they can be drawn into thin wires.
They are non-ductile.
5
Metals are malleable. It means that it can be hammered into thin sheets.
Non-metals not malleable.
6.
They are the elements whose atoms possess 1-3 electrons in their outer most shell (valence shell).
They are the elements whose atoms possess 4-8 electrons in their outer most shell.
7
They have the tendency to lose electrons from their valence shell
They have the tendency to gain electrons in their outermost shell
8
Metals are sonorous i.e. produces sound when bitten.
They are non-sonorous in nature.
9
They form basic oxides.
They form oxides which are acidic in nature.
10
They are having low electronegativity.
They have high electronegativity.
11
They are good reducing agent.
They are good oxidizing agent.


Lancashire Boiler Construction, Working with Diagram



Lancashire Boiler

Lancashire boiler is a horizontal drum axis, natural circulation, natural draft, two-tubular, low pressure, stationary, fire tube boiler with furnace located internally.


Construction

Lancashire Boiler

The various mounting of the Lancashire boiler are as follows



Lancashire Boiler


Safety valve: it is used to blow off the steam when the pressure of the steam inside the boiler exceeds the working pressure.

Water level indicator: it indicates the level of water in the boiler. It is placed in front of the boiler. Two water level indicators are used in the boiler.

Pressure gauge: The function of the pressure gauge is to indicate the pressure of the steam inside the boiler.

Steam stop valve: Its function is to stop and allows the flow of steam from the boiler to the steam pipe.

Feed check valve: It stops and allows the flow of water inside the boiler.

Blow off cock: Its function is to remove the sediments or mud periodically that is collected at the bottom of the boiler.

Man hole: it is a hole provided on the boiler so that a man can easily enters inside the boiler for the cleaning and repairing purpose.

Fusible plug: it is used to extinguish the fire inside the boiler when the water level inside the boiler falls to an unsafe level and prevent explosion. It also prevents the damage that may happen due to the explosion.

Grate: it is a platform which is used to burn the solid fuel.

Fire door: it is used to ignite the fuel present inside or outside the boiler.

Ash pit: it is used to collect the ash of the fuel after the fuel is burnt.


The various accessories that are used in Lancashire boiler are:


Economizer:  It is a mechanical device which is used as a heat exchanger in steam power plant. It is used to pre-heat the fluid or water by taking the residual heat from the combustion products i.e. flue gases. it is just installed to increase the efficiency of the boiler in the power plant.

Air pre-heaters:  It is a mechanical device which abstracts the heat from the flue gases and transfers it to the air. In boilers the pre-heaters are installed in between the economizer and the chimney.

Super heater: It is used in super heating of steam produced in the boiler. Its main purpose is to increase the temperature of the saturated steam without any change in the pressure.

Feed pump: It pumps the water from storage to the boiler during the boiler operation.



Lancashire Boiler Working

Now I am going to explain the working of this boiler step by step


Lancashire Boiler

Lancashire Boiler




  • Lancashire boiler consists of a horizontal cylindrical shell filled with water surrounding two large fire tubes.
  • The cylindrical shell is placed over a brick work which creates several channels for the flow of hot flue gases. 
  • Solid fuel is provided by the fire door which then burnt over grate at the front end of each fire tube.
  • A small arc shape brick work is provided at the end of the grate to deflect the flue gases upward and prevent the entry of burning coal and ashes into the interior part of the fire tubes. 
  • The fire tubes are slightly conical at rear end to increase the velocity of hot flue gases. 
  • When hot flue gases are allowed to pass through the downward channel at the front end of the fire tubes. Now these gases pass through the side channel towards the rear end of the fire tube and finally escape out through the chimney. 
  • There are dampers at each side channel to regulate the air flow. 
  • Feed check valve is used to feed the water uniformly to boiler shell. 
  • Once the boiler is at quickly, water converts into steam by absorbing the heat from the flue gases. This steam is stored at the upper portion of the boiler where anti priming pipe separates the water from steam. Thus the steam stop valve receives the dry steam for various purposes.
  • A man hole is provided at the top and bottom of the shell to allow a man to enter into the boiler and clean it. 
  • A blow off valve is provided to remove the mud that has settled down. It is also used to clean the boiler.

For better understanding watch the video given below:




Advantages



  • It has high thermal efficiency; the thermal efficiency is about 80 to 90%.
  • It is easy to operate.
  • It can easily meet the load requirement.
  • Easy to maintain.
  • Generate large amount of steam and hence more reliable.
  • Low consumption of electricity due to natural circulation.


Disadvantages



  • It is a low pressure type boiler, so high pressure steam is not produced.
  • Tedious maintenance of brick work.
  • It has limited grate area due to small diameter of the flue tubes.
  • Steam production rate is low. It is about 9000 kg/hr
  • Corrosion occurs in the water legs.


Area of application

The Lancashire boiler is used to drive steam turbines, locomotives, marines etc. it is used in the industries like paper industries, textile industries, sugar industries, tire industries and Etc.

Now this is all about the Lancashire boiler. If you find anything missing in this then let me know through your commenting.