## ISRO Mechanical engineering placement paper

1. Working temperature of an evaporator and condenser of a dedicated refrigerator are from a minimum of -300 C to a maximum of 320. If the actual refrigerator contains a C.O.P of 0.75 of maximum value, the required power input for a refrigerating effect worth 5 KW comes out to be?

A. 4.0 KW

B. 3.92 KW

C. 2.94 KW

D. 1.7 KW

2. The below figure shows a temperature entropy diagram for a steam turbine power plant, it operates on Rankine cycle with reheat and regenerative feed heating as mentioned. If m shows a fraction of steam bled for feed heating system, what is the work developed in turbine per kg steam entering the turbine at state 5?

A. (h5-h4) + (1-m)(h3-h1)

B. (h5-h4) + (1-m)(h3 – h2)

C. 2h5 - h4 – h2 +(1-m)(h2 – h1)

D. (h5-h4) + (h3 – h2) + (1-m)(h2 – h1)

3. From transition from laminar to turbulent boundary layer in external flows, critical value of Reynolds number is taken as

A. 5 X 10∧5

B. 4000

C. 2300

D. 4600

4. For a single coil bypass factor in an air conditioner is considered as 0.7. If that is known what is the bypass factor if 3 such cooling coils with same dew point are kept one behind the other?

A. 0.343

B. 0.292

C. 0.210

D. 0.461

5. Which one of the following statements will you consider true for an air conditioning design (duct)?

A. Equal friction method is preferred when duct work is considered extensive, total pressure drop is taken as low and the flow is unbalanced.

B. Static regain method is considered, where duct work is fully extensive, total pressure drop is high and flow is balanced.

C. Static regain method is considered, where duct work is fully extensive, total pressure drop is low and flow is balanced.

D. Static regain method is considered, where duct work is fully extensive, total pressure drop is low and flow is balanced.

6. Consider the following facts for an air conditioning system, RTH = 100 KW, RSHF = 0.75, volume flow rate becomes equal to 100 m

^{3}/ minute and the indoor specific humidity can be 0.01 kg. What is the specific humidity of supply air?

A. 0.005

B. 0.0075

C. 0.010

D. 0.0025

7. For an air conditioning system, 45 degree celcius and 25 degree celcius are outdoor and indoor dry bulb temperature. Air conditioned space is 20m x 30m x 5m and the infiltration is taken as one air change. If density and specific heat of air are 1.2 kg of dry air per metre

^{3 }and 1.02 KJ °C then what is then what is the sensible heat load due to infiltration?

A. 20.4 KW

B. 12.24 KW

C. 61.2 KW

D. 122.4 KW

8. Match List I and List II with correct answers using the codes mentioned below in the lists:

H

_{m} = mass transfer coefficient

D = molecular diffusion coefficient

L = characteristic length of dimension

k = thermal conductivity

p = density

Cp = specific heat at constant pressure

u = dynamic viscosity

---A----B----C----D

A. 4----3----2----1

B. 4----3----1----2

C. 3----4----2----1

D. 3----4----1----2

9. Following are some statements regarding the advantages of fuel injection in dedicated S.I. engines:

1. Simple and inexpensive injection equipment

2. Longer life of the injection equipment

3. Less knocking and reduction propensity of back firing

4. High power output and more volumetric efficiency

Which of the following statements are true?

A. 1, 2 and 4

B. 1, 3 and 4

C. 3 and 4

D. 1 and 4

10. In regard to a 4 stroke diesel engine what does the term “squish” mean?

A. Stripping off fuel from the core of system

B. Entry of air inside the combustion chamber

C. Precombustion chamber discharging gases

D. Injection of fuel inside the precombustion chamber

11. List 1 contains performance parameter Y

List contains the curves which are labelled as 1, 2, 3, 4 and 5 (BHP vs Y)

CI engine is running at a constant speed. Choose the correct option:

---A----B----C----D

A. 1----3----4----2

B. 5----3----4----2

C. 1----4----2----3

D. 5----4----2----3

12. Match List I and List II and select the correct answer accordingly

List I-----------------------------List II

a. Supercharging-------------------1. Multicylinder Engine

b. Morse Test----------------------2. CI Engine

c. Ignition Quality of Petrol------3. Calorific Value

d. Heterogeneous Combustion--------4. Aircraft Engine

5. Octane Number

6. Single Cylinder SI Engine

---A----B----C----D

A. 6----3----4----2

B. 5----3----4----2

C. 4----1----2----5

D. 5----4----2----6

13. Consider the following statements w.r.t Turbojet and Rocker engines:

1. Rocket engines are air engines

2. Stagnation conditions are present in combustion chamber in the Rocket engines

3. Efficiency of Rocket Engines is larger than that of Jet Engines

4. Exit velocities of exhaust gases in case of Rocker engines is much more than in Jet engines

Which of the following statements is/are considered correct?

A. 3 and 4

B. 2, 3 and 4

C. 1 and 3

D. 1 and 2

14. Consider the following statements w.r.t I.C. engine emission

1. There exist no suspended particulates in exhaust

2. Exhaust emissions have 100% CO, 100% NOx and 50 – 55% of hydrocarbons

3. Blow by emissions have CO and suspended particulate matter

4. Evaporative emissions do not have CO and nitrogen oxides

A. 1, 2 and 3 are correct

B. No option is correct

C. 2 and 3 are correct

D. 1 and 4 are correct

15. Orsat analysis of dry products of combustion of a hydrocarbon fuel gave way to the following data:

What is the % by volume of CO

_{2} in the dry product?

A. 5%

B. 11%

C. 2%

D. 18%

16. Match List I with its use in List 2 and select the correct answer accordingly:

---A----B----C----D

A. 1----3----4----2

B. 1----2----4----3

C. 1----4----2----3

D. 2----1----4----3

17. The table below represents a Carnot cycle where:

Q1 = Heat received in KJ per minute

Q2 = Heat rejected in KJ per second

W = Work output

If the heat received by engine is given as 2,000 KJ per minute then what is the work output?

A. 10.95

B. 11.54

C. 10.39

D. 9.98

18. A system is undergoing a cycle

A_B_C_D_A is a process which has dedicated values of heat and work transfers mentioned in the table:

The power developed in terms of KW is approximately:

A. 4.9

B. 49

C. 24.5

D. 98

19. Let us say there is a new temperature scale °p, in this scale the boiling and freezing points of water at 1 atm pressure are 100°p and 300°p. Correlate this with Celsius scale. What is the reading of 0°p on Celsius scale?

A. 0

B. 150

C. 50

D. 100

20. Match List I and List II and accordingly select the correct answer making use of the codes in the list:

---A----B----C----D

A. 4----3----2----1

B. 1----3----4----2

C. 1----4----2----3

D. 1----4----2----3

21. Consider the following phase diagram of a substance as shown in the figure. Match List I(Process) and II(Curves/Lines) and accordingly select the correct answer making use of codes mentioned below:

---A----B----C

A. 1----2----3

B. 3----2----1

C. 2----3----1

D. 1----3----2

22. If Pu and Pv signify partial pressure of dry air and water in moist air, what is the specific humidity of air given by?

A. Pv/(Pu + Pv)

B. Pv/Pu

C. 0.622 Pv/Pu

D. 0.622 Pv/(Pv + Pu)

23. Three factors:

No. of components (C)

Degree of freedom (F)

Phase (P)

Are given by Gibbs phase rule as:

A. F__C__P = 2

B. C + F – P = 2

C. C__P__F = 2

D. P + F – C = 2

24. Consider these statements:

1. Availability can be said as maximum theoretical work obtained

2. A gas at a given pressure can obtain any temperature unlike vapour which can only obtain a fixed temperature at a given pressure.

3. Clapeyton’s equation for dry saturated steam:

4. Joule Thomson coefficient:

Which of these statements is true?

A. 1. 2 and 4 are marked correct

B. 2 and 3 are marked correct

C. 1, 2 and 3 are marked correct

D. 1 and 4 are marked correct

25. Match List I and List II and accordingly select the correct answer using codes given:

---A----B----C----D

A. 3----4----2----1

B. 1----3----4----2

C. 3----4----1----2

D. 1----4----2----3