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Showing posts with label Academics. Show all posts
Showing posts with label Academics. Show all posts

What would happen if compressor is removed from the refrigerator?

Simply, refrigerator would STOP! but why? 

To answer this question, one need to know the Second law of thermodynamics (Clausius Statement) which states "It is impossible to construct a heat pump which continuously takes away the heat from low temperature region to high temperature region without taking any external work". 

Here, heat pump is our refrigerator which keep on throwing heat from low temperature environment to room temperature. As per the above statement, external work is must to run the refrigerator. That external work is represented by "Compressor".

Second thing, to have heat transfer from evaporator to condenser, you need to  change the phase of the substance. The change of phase absorb or liberate the heat depending on the phase change. Thus, heat of food can be transferred to condenser by changing the liquid phase refrigerant to vapor phase in evaporator and this heat is rejected at condenser at room temperature. This task is performed by compressor by changing the pressure of the refrigerant.

How to write an abstract for technical report or article or paper?

If you are an engineer and working in industry or academics, you need to submit technical report or research paper to express the findings and working of stuffs.

An Abstract is an important element of any technical report or any research paper/article. It is something which people normally prefer to read before taking a look at the whole article. The abstract must contain the enough information which highlights and give the complete essence of the article. 

Normally abstract should deliver objectives of the research, methods that one has used for research, key results obtained and a clear and concise conclusion. 

The abstract should contain minimum 100 to 200 words. The content of the abstract should be clear and concise. 

It should highlight the main objectives and motivation of the research. Do not write an equation and related stuff in it. 

Avoid putting references in an abstract. One should not use in this 'paper' or 'article' but use 'research' or 'investigation'. 

The abstract must have enough information which develops the interest to read the full paper or article.

Tips for GPSC Interview for lecturer and assistant professor

These are the tips which can be helpful to clear the GSPC personal interview for lecturer and assistant professor
  1. Have confidence in your answer while you are asked to speak about yourself. This is normally very first question asked by chairman of interview "Tell me about yourself". Make answer ready in advance. Speak your full name, age, qualification with college and university,current job.
  2. Now when you are asked about your job, give positive aspects of job.
  3. Why do you want to do teaching job? Why not current job? Do not say I am not enjoying the current job but say, "I love teaching and this changes lives of people. I want to impact the life of many by teaching job. This job is respectful job"
  4. Always ready with two or three favorite subjects. 
  5. Prepare DEMO lecture that will be most probably asked to deliver. 
  6. SAY "NO" IF YOU ARE NOT VERY SURE ABOUT QUESTION'S ANSWER. IF YOU GIVE WRONG ANSWER THEY WILL TRAP YOU AND ULTIMATELY TIME AND YOUR REPUTATION WILL BE WASTED. Just say 'No' and pass the question. New question might be familiar to you. This will have impact of honesty on interviewer. 
  7. DO NOT ARGUE. DO not hurt them by saying I AM right even though they are wrong. They just make sure about your character. 

Essential software to learn in Mechanical Engineering

The knowledge of different software in mechanical engineering is a great quality and can be helpful to get required things done easily. Because software is tool which can be used by an engineer to express the technical stuffs via calculations.

Below are the important and essential software which should be learned during bachelor course in mechanical engineering. It might possible that some well-known software might not be in the list but can be learned very easily if you know the following software which is basics.

1. AutoCAD ( A basic CAD software for design and drafting purpose)
2. Pro/Engineer ( A complete parametric 3D CAD/CAM/CAE software)
3. C Language (A programming language)
4. ANSYS ( An analysis or simulation software)

Why cooling capacity unit of domestic refrigerator and Air Conditioner (AC) is different?

Have you ever wondered, Why capacity units of the domestic refrigerator and Air Conditioner (AC) are different though both are refrigeration system? What is the basic difference between them with respect to the cooling capacity?

The capacity of the domestic refrigerator is normally rated in 'Litre'.

Litre is actually a unit of volume and it is applicable to the domestic refrigerator while dealing with space/volume to be cooled. Thus, liter capacity actually indicates the volume or space to be cooled by the domestic refrigerator.

On the other hand, the capacity of Air Conditioner (AC) is given by term 'Ton of refrigeration'.

What is one Ton refrigeration?

Automobile project topics for final year mechanical engineering

Normally final year project aims at developing something new and which might serve the society with betterment. One can also choose automobile as one of the option in mechanical engineering. One can do the theoretical analysis, innovative design and changes in existing system of automobile. 

Following list of topics can be useful to them.

  • Innovative Six stroke I C Engine
  • Performance evaluation of existing four stroke bike or scooter
  • Thermal performance evaluation of radiator of an automobile

All you need to know about Thermodynamics Properties

Thermodynamic Property is a measurable characteristic of the system.
To get the status of any process of the system, one should have at least two properties at hand. Thus to define the state of a system, we must know the information about different thermodynamics properties. 

One can classify the general properties in following ways.

1. Primitive Properties (which are taken from other branches of the science)
  • Pressure, P
  • Velocity, v
  • Volume, V

2. Basic Thermodynamic Properties (which are defined by the laws of the thermodynamics)
  • Temperature, T (defined by the zeroth law of the Thermodynamics)
  • Internal Energy, U (defined by the first law of the Thermodynamics)
  • Entropy, S (defined by the second law of the Thermodynamics)
3. Derived Thermodynamics Properties (Combination of various other properties defined earlier)
  • Enthalpy ( U + P.V)
  • Gibbs Energy (U + PV-TS)
  • Specific Heat at Constant Pressure, Cp
  • Specific Heat at Constant Volume, Cv

Refrigeration system-Construction and working of 'Ice plant'

We all are aware of domestic refrigerator and its usage. We get ice cubes from freezer compartment to meet daily requirements but to get ice in huge quantity we normally approaches the ice plant or factory. Here, I am going to share overview of construction and working of ice making process and its layout. 

Normally, any refrigeration system consists of four main equipments:

1. Compressor
2. Condenser
3. Throttle valve/flow control valve
4. Evaporator

Construction of Ice plant
But in Ice plant or factory, two additional circuits help us to create ice in huge quantity. Refer to the figure and Video.

Difference between 'Thermodynamics' and 'Heat Transfer'

Thermodynamics and Heat Transfer both are part of thermal engineering and each has its own meaning and importance. Both deals with heat and energy then, one might ask, what is the real difference between the two subjects ? i.e. Thermodynamics and Heat Transfer

"Thermodynamics" deals with the amount of energy in form of heat or work during a process and only considers the end states in equilibrium. It will not give information about how long it will take to reach to the final state in equilibrium. While,

"Heat Transfer" deals with the rate of energy transfer thus, it gives idea of how long a heat transfer will occur? Heat transfer deals with time and non equilibrium phenomena. Heat can only transfer when there is a temperature gradient exists in a body and which is indication of non equilibrium phenomena.

In short, Thermodynamics gives "Why"  a process will occur and Heat Transfer will tell, "How" a process will occur when there is a concern about transfer of heat.

To support all these arguments, Thermodynamics uses following laws,

  • Zeroth Law of Thermodynamics
  • First law of Thermodynamics
  • Second Law of Thermodynamics
  • Third Law of Thermodynamics

While, Heat Transfer uses,

  • Fourier's Law (Heat conduction)
  • Newtons Law of Cooling (Heat convection)
  • Planck's Law (Thermal Radiation)
  • Stephan Boltzman's Law (Thermal Radiation)
  • Wein's Law (Thermal Radiation)
  • Kirchoff's Law (Thermal Radiation)
  • Lambart's Law (Thermal Radiation)
Learn more about such important questions to be asked in Mechanical Engineering Interview

Tips to avoid common errors or mistakes in technical papers or writing

In current technological era, everything get done by machine and related technology. Each needs research and development. So, to convey the information or findings one need to write technical report, paper or writings. Most of the times, technical reports are full of quality but they contain common errors which might change the meaning or may cause rejection of technical papers also.  So, read the following tips to know what are the common errors and its solutions.

Numeric numbers:
Technical writings are full of numbers and data. Normally integers or numbers less than ten are written in words. Say to convey '2 components, one should write 'two components'. Numbers greater than ten and fractional numbers can be written in digits like 11, 12.4 etc.

Take care of 'a, an, the':
Always remember than 'a' & 'an' can be used when we talk about indefinite things while 'the' can be used while talking about 'definite' things. 

Quiz-2 Objective questions in mechanical engineering: Heat transfer

Get ready for the quiz on 'Heat Transfer' subject and check your knowledge by appearing for the test given below. By the end of the quiz, you will get your score out of 10 as well as answer keys. So, get ready to check your knowledge in basics of thermodynamics.

You need to enter Your Name & Passcode which is mechanicalduniya to enter into the quiz interface.

The quiz is based on following topics of Heat transfer

Quiz-1 Objective questions in mechanical engineering: Basic of thermodynamics-1

This is a multiple choice question quiz. To appear for the test, you need to enter following details at the quiz interface. 1. Your name and passcode i.e. thermotest

By the end of quiz, you will get your score out of 10 as well as answer keys. So, get ready to check your knowledge in basics of thermodynamics.

Cone penetration test on Lubricating Grease - Grease Penetrometer

Aim: To find out the consistency of given sample of grease.

What is Consistency of Grease?
- Measure of relative hardness of grease is referred as consistency number as per N.L.G.I (National Lubricating Grease Institute) which is a trade association that governs lubrication and related industry research.

 What is Grease?

A Semi-fluid lubricant made of base oil and thickener.

Most important subjects for GATE Mechanical Engineering

Mostly student preparing for the higher studies or job ask one common question. Which subjects are most important in mechanical engineering? Mechanical curriculum contains many subjects but some of them are basic subjects on which other subjects are based and rely upon it.

Undergraduate syllabus or curriculum normally contains subjects like
Machine Design mainly requires knowledge of Strength of Materials because to design of any machine component, we need to look for types of loading, calculation of equivalent forces and stresses. So, before studying Machine Design, we need to have sound knowledge of strength of materials. So, in curriculum of any mechanical engineering, Strength of Materials/Mechanics of Solids are covered (in first or second semester) before Machine Design.

Thermodynamic Tutorial: Laws of thermodynamics and properties of pure substances

Thermodynamics Tutorial: Second law of Thermodynamics

What is the minimum amount of work input necessary to a refrigerator which will convert 1 kg of water at 20 oC into ice at -5oC?  (Ans: 40 kJ)
A heat engine receives heat from a solar collector plate. Solar radiation of amount 1880 kJ/m2 falls on the solar collector and raises its temperature to 95 oC. The engine rejects heat to the atmosphere having 20oC. Calculate the minimum solar collector area required for a plant producing 1 kW of useful shaft power. (Ans: 9.394 square meter)

Calorific value and its types (Higher calorific value and lower calorific value)

Any fuel that is to be used in any combustion process first, be checked by its calorific values. The cost of fuel is also affected by the calorific value of the fuel. Here you can find the basic information about the calorific value and its type. 

What is combustion?

'Bomb Calorimeter' for determination of Calorific Value of solid and liquid fuel

Calorific value (CV) of a fuel is a characteristic of fuel which is defined as the energy liberated per kg of fuel burnt. Fuels are found in three phase viz. solid, liquid and gaseous. Junker's calorimeter is used to measure the CV of gaseous fuels.

Bomb Calorimeter experiment to measure calorific value of fuel:
  • It is used to measure the calorific value (CV) of solid as well as liquid fuel. But to determine the CV of gas, one need to choose Junker's calorimeter.
  • A calorimeter contains thick walled cylindrical vessel and it consists of the lid which supports two electrodes which are in contact with fuse and fuel sample of known weight. 
  • The lid also contains oxygen inlet valve through which high-pressure oxygen gas (at about 25 to 30 atm) is supplied.
  • Entire lid with fuel sample is now held in a copper calorimeter containing known weight of water. A mechanical stirrer is provided to stirred well for uniform heating of water. 
  • A thermometer is also provided to measure the change in temperature of water due to combustion of fuel in Lid. 

Free e-books for mechanical engineering subjects

This article aims at sharing free e-books for mechanical engineering subjects. You can ask for any book that is listed below.