Comparison of Control Mass & Control Volume System | Closed System Vs Open System

Are you looking for a comparison or technical/conceptual difference between control mass system and control volume system? then you are at the right article. This can be also interpreted as the difference between an open system and closed system in classical thermodynamics.

As we all know a system in classical thermodynamics can be classified into a control mass system, control volume system and isolated system. The comparison between control mass system and control volume system are as follows.

Control Mass System (Closed System)

• There should not be any mass interaction. However, there can be energy interactions. Control mass system interacts with the surroundings in the form of work and heat.

• Mass inside the system is constant as well as its identity is fixed. For example, from a system containing water of 100 kg, 10 kg of water is taken out and is replaced with 10 kg of oil. Here even though initial and final mass is the same (constant), that is 100 kg but the identity of mass is changed, it is like 90kg of water and 10 kg of oil instead of 100 kg water. So this cannot be treated as a control mass system.

• In control mass system, the volume of the system may change.

• Example of a closed system or control mass system is piston-cylinder arrangement without a valve.

Control Volume System (Open System)

• In this type of system, there are both mass and energy interactions between system and surroundings. Control volume system interacts with the surroundings in the form of work, heat as well as mass.

• Here identity of mass may not be fixed.

• In an open system, the volume of the system is fixed and is known as control volume.

• The boundary of the control volume is known as the control surface.

Interesting concept: In steady state, control volume system will look similar to control mass system but will differ in terms of identity.  That is, in steady state, mass into the control volume = mass out of control volume and for control mass system, mass is always constant. But in both cases, the identity of mass is different.  

Comparison between Rankine & Reverse Rankine Cycle

This page will give you the basic differences and thermodynamical comparison between Rankine cycle and reverse Rankine cycle. The comparison of the two is easy as one is the reverse of the other. Both are identical cycles but their process diagrams are in opposite direction. The basic idea of Temperature-Entropy (TS) diagram of Rankine and reverse Rankine cycle is a prerequisite for reading this article. The following are the basic comparison between both the cycles.

Rankine Cycle

• It is a work producing cycle and is the basic vapor standard thermodynamic cycle for the steam power plant.

• This concept is centered around Kelvin-Plank statement of the 2nd law of Thermodynamics. This statement gives rise to the idea of work producing devices.

• Steam is the working fluid in this cycle.

• The direction of the various thermodynamic processes in Rankine cycle is in the clockwise direction.

• In Rankine cycle, expansion process in the turbine is considered as isentropic.

• In Rankine cycle, we are interested in finding out the cycle efficiency and net work output and it is desirable to increase both.

• An increase in boiler pressure in Rankine cycle results in the reduction of heat rejection or increment in mean temperature of heat addition which ultimately results in an increase in efficiency. However, dryness fraction decreases and requires a higher capacity feed water pump.

• A decrease in condenser pressure reduces the heat rejection and increases the turbine work output and thus increasing the efficiency. But here also dryness fraction decreases.

• Superheating in Rankine cycle improves the efficiency as well as the dryness fraction of steam.

• Regeneration in Rankine cycle also improves the efficiency.

Reverse Rankine Cycle or Vapour Compression Refrigeration

• It is a work consuming cycle and is the basic vapor standard thermodynamic cycle for the vapour compression refrigeration system.

• This concept is centered around Clausius statement of the 2nd law of Thermodynamics. This statement gives rise to the idea of work consuming devices.

• Working fluid is usually referred to as a refrigerant.

• The direction of the various thermodynamic processes in reverse Rankine cycle is in the counterclockwise direction.

• In reverse Rankine cycle, expansion process in the throttling device is considered as isenthalpic.

• In reverse Rankine cycle, we are interested in finding out the coefficient of performance (COP) and it is desirable to increase it.

• COP decreases with increase in condenser pressure and a decrease in evaporator pressure.

• The variation of COP is unpredicted in the case of superheating. This is because of the increment in refrigeration effect with the same work consumed by the compressor.

• Subcooling increases COP of reverse Rankine cycle.

FACT Management Trainee Mechanical Online Exam Questions, Syllabus & Expected Cut Off

If you are looking for FACT management trainee exam previous year question papers, online exam questions, syllabus, answer keys and expected cut off marks 2017, frankly speaking you will not find the same in any of the websites. However this blog post updates the exam pattern, some of the questions asked and expected cut off based on the reviews and opinions from the candidates who appeared for FACT management trainee exam. FACT previous papers are not available outside the exam hall because the examination is online and FACT do not publish these questions in their website. Previously the examination was offline and even after the offline exam candidate was supposed to return the question paper. So,the only way you can get the questions and model of examination is from the opinion of candidates who are already appeared for the exam. Some of the asked questions and expected cut off of 2017 FACT management trainee mechanical paper will be posted in this page latest by 11.04.17 for the online examination conducting on 09.04.2017. Bookmark this page for the updates.

The Fertilisers and Chemicals Travancore Limited (FACT) conducted the latest test for management trainee mechanical on 09.10.2016, however the test was cancelled due to some reasons. The retest is scheduled on 09.04.2017. Based on the candidates opinion who appeared for the test, the following is the pattern of examination.

Pattern of FACT Management Trainee Online Exam conducted on 09.10.2016

Duration of test - 120 mins

No. of questions - 200

Type of questions - Mechanical Engineering, Quantitative Aptitude, English, GK & Current Affairs

Maximum weightage among questions - Mechanical Engineering 

Note:  This may not guarantee the pattern for the upcoming exams, as FACT used to change the exam pattern. 

Syllabus for FACT Management Trainee Exam

1. Mechanical Engineering - Numerical + Theory Questions

2. Quantitative Aptitude - Try to solve questions from Quantitative Aptitude by R S Agarwal

3. General English - Try to solve questions from General English by R S Agarwal

4. GK & Current Affairs

FACT Management Trainee Selection Procedure

1. Written Test

2. Group Discussion

3. Interview

How to Pass Kerala PSC Assistant Engineer Exam - Tips & Guidelines

This post will be helpful for the aspirants who are keen to get a job as Assistant Engineer through Kerala PSC examinations. Kerala PSC Assistant Engineer is relatively a simple examination if you are thorough with the basics of your engineering course. Along with that, you should have some good knowledge about Kerala renaissance, Indian polity, Indian history and general awareness. This examination is conducted by Kerala PSC for recruitment in various Kerala government departments like irrigation, PWD, metrology, harbor engineering, KSEB, agro industries, ground water department etc. All these recruitment will offer you an attractive salary package according to the 7th pay commission.

Pattern of Kerala PSC Assistant Engineer Exam

The examination will be a 75 minutes objective test (online or offline). The question paper can be divided into 2 sections. 80 questions will be from technical side (which is related to your branch of engineering) and 20 questions will be from general knowledge (which mainly includes questions from Kerala renaissance, Indian polity, social welfare schemes and general awareness). For offline exams, it will be OMR type exams and for online exam, it will be a computer based test.

How to Start Preparing for Kerala PSC Assistant Engineer Exam?

If you are an engineering graduate or pursuing graduation, the best time to start is now itself. As you want to complete your entire 4-year syllabus, an early preparation before the examination is recommended. Moreover, the time which Kerala PSC call for a certain post will be so uncertain and you have to complete the syllabus in stipulated time. The best way to start is to download the syllabus for the target examination from Kerala PSC website and start preparing each and every topic. The syllabus for the upcoming examination will be available in Kerala PSC official website. While preparing technical subject make sure that you noted all conceptual points and very important numerical data. Say, for example, remembering the stoichiometric A/F ratio of petrol engine can fetch you 1 mark easily.

Along with technical subject preparation, study non-technical part (GK) also. Divide your study hours in such a way that you are giving 3/4th of your time for technical subject preparation and 1/4th of the time for GK. While studying GK section, give most preference to Kerala renaissance, literary figures, struggles and social revolts (including all the main leaders participated). Studying this part thoroughly can certainly bring you at least 5 marks guaranteed out of 20 marks. After completing this part, go for studying Indian Polity and some general Indian history topics (especially starting from 1857 revolt till India got independence in 1947). Studying this can fetch you around 4 marks out of 20. Then study about social welfare schemes prevailing in India and Kerala. Rest of the marks will be current affairs. Some important dates on the above-mentioned topics also must be remembered. If you want useful study material for non-technical part, then check this link - Kerala PSC Study Materials

What are the important topics to be studied in Kerala PSC Assistant Engineer Exam?

Technical Subject - 80% 

Kerala renaissance and associated topics - 10%  (Click here to get complete study material)

Indian polity - 5%

Social welfare schemes - 3%

Current affairs - 2%

Where do you get the study material for Kerala PSC Assistant Engineer Exam?

While preparing, it is important that you follow standard study materials. Always refer good textbooks with good concepts which are not misleading and confusing as most of the questions asked in Kerala PSC assistant engineer exams will be conceptual (theory based). If you are seriously preparing for GATE/IES examinations, then the content will be well and sufficient. 

For getting sample question papers offline, it is best to solve previous year IES question papers and GATE questions (except lengthy numerical problems). There are many solved question paper books available for purchase. Try to purchase error free books as much as you can. Previous year IES/GATE solved question papers of made easy publication is comparatively better. You can also get the material by post by contacting the concerned institutes.

If you want exact past year question papers of Kerala PSC assistant engineer examination, then there are very less choices available in Kerala. You can purchase books from electron publications for the same. Practice those questions and then you will get an idea about the pattern of questions asked in the examination.

Check this link- Kerala PSC AE study material. 

Where to download previous year question papers for Kerala PSC Assistant Engineer Exam?

You can visit the official website of Kerala PSC for recent year question papers. This will be include questions for the last 2 to 3 years. Some of the specific previous year question papers will be updated on yet another blog www.keralapscanswerkeys.blogspot.in. You can visit this blog for mechanical engineering related question papers.

Check this link for - Kerala PSC Assistant Engineer Mechanical - previous year question papers and answer key

How many marks should be scored (Cut off Marks) in Kerala PSC Assistant Engineer Exam for getting into final merit list?

This depends on the toughness level of each examinations. However if you score 65-70 marks, you will be in safe zone for most of the exams. This will not include marks of personal interview.

Is there any coaching for Kerala PSC Assistant Engineer Exam?

If you are interested to attend coaching classes, it is better to join Made-Easy institute or ACE institute which are the leading institutions in the country for engineering subject coaching but they are not available in Kerala. If you want to do coaching in Kerala, then Gate forum institute will be a good option.

If you are looking for career guidance - check this page - Career guidance in Mechanical Engineering

For any quires feel free to post in the comment section of this blog. If you like this post, please share the links to your friends through the share buttons below. Your "thumps up" will encourage us to post more for you. 

Solved Question Paper & Answer Key of Vocational Instructor in Maintenance & Operation of Marine Engines 490/15 - Kerala PSC

Date of exam: 03.03.2017

Exam Code 032/2017

Question Booklet Alpha Code A

1. In a diesel engine, fuel is ignited by:

a) Injecting Fuel

b) Spark plug

c) Heat resulting from compressing air that is supplied for combustion

d) Igniter

Ans: C - Heat resulting from compressing air that is supplied for combustion.

Explanation: In diesel engine, fuel is sprayed by the fuel injector at the end of compression stroke and heat resulting from the compressed air is supplied for combustion. In petrol engine. In petrol engine, fuel is ignited with the help of spark plug.

2. If the intake air temperature of  IC engine increases, its efficiency will :

a) decreases

b) increases

c) remain same

d) unpredictable

Ans: A - decreases

Explanation: When temperature increases, the ratio Cp/Cv (ie γ) decreases, so efficiency of IC engine decreases according to the efficiency expression of IC engine (say Otto Cycle). More over, practically, higher the intake temperature, then higher will  be the pressure during compression stroke (as PV=mRT and V is constant, P∝T), but pressure during power stroke is not so. So this will create mechanical friction and will decrease the efficiency.

3. Air fuel ratio of petrol engine is controlled by:

a) Governor

b) Injector

c) Fuel Pump

d) Carburettor

Ans: Carburettor

Explanation: Carburettor mixes air and fuel in case of SI engine

4. Which of the following is the lightest and most volatile liquid fuel

a) gasoline

b) fuel oil

c) diesel

d) kerosene

Ans: gasoline

Explanation: Gasoline is the lightest and most volatile fuel among the option. Diesel is least volatile fuel. However auto ignition temperature of diesel < auto ignition temperature of Kerosene < auto ignition temperature of petrol. This is the reason why diesel is used in CI engines and so only we use spark plug for igniting petrol engine

5. Ignition timing of multi cylinder engine can be adjusted by

a) rotating the crank

b) rotating the distributor

c) adjusting the spark plug gap

d) adjusting ignition coil position

Ans: B - rotating the distributor 

6. Breeder reactor has a conversion ratio of

a) zero

b) more than unity

c) less than unity

d) infinity

Ans: B, more than  unity

Explanation: Breeder reactor is a nuclear reactor with high neutron economy. It can generate more fissile materials than it consumes. So its conversion ratio is more than 1. Conversion ratio is defined as the ratio of average number of new fissile atoms created per fission. Conversion ratio is a measure of performance of the nuclear reactor.

7. In nuclear fission, each neutron that causes fission releases

a) no new neutron

b) at least one new neutron

c) many fold neutrons

d) more than one neutron

Ans: D - more than one neutron

8. Super heated steam is generated in the following reactor

a) boiling water

b) pressurized water

c) gas cooled

d) none of the above

Ans: A - boiling water

Explanation: Super heated steam will be generated in boiling water reactor (BWR)

9. First nuclear power plant in India is located at

a) Kota

b) Kerala

c) Tarapur

d) Kalpakkam

Ans: C- Tarapur (Maharashtra)

10. In boiling water reactor, moderator is 

a) coolant itself

b) graphite rod

c) ferrite rod

d) blanket of thorium

Ans: A - coolant itself

Explanation: In a boiling water reactor (BWR), both coolant and moderator are the same. De-mineralised water is used for both the purpose.

11. Basic tool in work study is

a) Graph paper

b) Process chart

c) Planning chart

d) Stop watch

Ans: D - Stop watch

Explanation: Stop watch is used in time study. Time study is a part of work study

12. Job evaluation is the method of determining the

a) relative worth of job

b) skills required by a worker

c) contribution of a worker

d) contribution of a job

Ans: A - relative worth of a job

13. Father of time study was

a) F W Taylor

b) H L Gantt

c) F B Gilberth

d) R M Barnes

Ans: F W Taylor

14. CPM is the

a) time oriented technique

b) event oriented technique

c) activity oriented technique

d) target oriented technique

Ans: C - activity oriented technique

Note: PERT - event oriented technique

15. Unit of energy in SI unit is

a) Watt

b) Joule

c) Joule/s

d) Joule/m

Ans: B - Joule

Note: SI unit of power is Watt

16. Super heated vapour behaves

a) exactly as gas

b) as steam

c) as ordinary vapour

d) approximately as gas

Ans: D - approximately as gas

17. Heat and Work are

a) Point functions

b) System properties

c) Path Function

d) Intensive property

Ans: C - Path Function

Explanation: Amount of Heat and work depends on the path of the process. Both heat and work are inexact differentials. However, properties are point functions. 

18. For reversible adiabatic process, change in entropy is

a) maximum

b) minimum

c) zero

d) negative

Ans: C - zero

Explanation: Reversible adiabatic process is an isentropic process. So change in entropy is constant.

Answer keys of the rest of the questions are given below. For further doubts in any questions, feel free to post in the comment section.

19. D  20. B  21. B  22. B  23. C  24. A  25. B  26. A  27. B  28. B  29. D  30. C  31. C  32.D  33.B  34. A 35. A 36. D  37. C  38. C  39. B  40. D  41. C  42. B 43. 44. D  45. A  46. B  47. B  48. C 49. D 50. A 51. C 52. B  53. B  54. A  55. C  56. A  57.B  58. A  59. A  60. C  61. B  62. D  63. C  64. B   65. D 66. A  67. A  68. A  69. B  70. A  71. D  72. 73. B  74. B  75. A  76. C  77. B  78. B 79. D  80.C  81. B 82. A  83. D  84. C  85. A  86. D  87. 88. D  89. C  90. D  91. A  92. B 93. A 94. D 95. B 96. D  97. C 98. A  99. C 100. B

Other useful link - 
1. Tips to prepare for Kerala PSC Assistant Engineer Mechanical Exam
2. Tips to prepare for Kerala PSC Assistant Director Exam - Industries & Commerce

3. Study materials useful for engineers in Kerala PSC exams. 
4. Previous year question papers for practice.

Disclaimer - The explanation given here is purely based on personal expertise. The final may or may not vary according to the PSC answer key.