Biman bangladesh airlines ltd. question & solution(13th july 2018)

This solution is done by
Engr. Md. Al-amin, ME, BUET.
(Obviously with the help of some talented people)
If any mistake/wrong solution is found please feel free to comment/discuss at alaminbuet2008@gmail.com
Biman Bangladesh Airlines
Ltd
Exam date: 13h
July 2018
Exam Time:
10.00 AM ~ 11.30 PM ( 1Hr 30 min)
Exam venue: MIST
Question pattern:
MCQ:
English+GK+Computer+Math = 50 marks
Dept. Written = 50 Marks
-------------------------------------------------------
Total = 100 Marks
Questions
MCQ:
1. CAAB- founder 1985
2. ICAO - International Civil Aviation Organization
3. Caan festivals 2018 award- Plame d’Or winner : Shoplifters
4. 2018 FIFA world cup football name- Telstar 2018
5. Writer of “ The Old man & The sea” Ernest Hemingway
6. Present UN president is from which country : Portugal
7. Many computers are connected to a common computer : Star technology
8. USB : Universal Serial Bus
9. What kind of device is scanner : Input Device
10. Primary function of BIOS : Save OS
11. 2, 3,5,7 are : prime numbers
12. product of two consecutive number can be written as: n2
+n
13. ∛5 can be also expressed as : 5
1
3
14. 4x+1
= 32, then find x ? x= 3/2
Departmental Question:
1. A 4 cylinder petrol engine has developed MEP=650 KPa, it's engine dia is 80 mm, stroke
length is 100 mm, speed 3000 rpm. Find engine power in KW ?
2. For counter flow heat exchanger Th1=160℃, Th2=125℃, Tc1=20℃, Tc2=80℃ , Draw
temperature distribution curve. Also Find arithmetic mean temperature difference &
logarithmic mean temperature difference.
3. A wire has got dia of 20 mm, if heat transfer co efficient is 20 W/m2
.K and thermal
Conductivity is 0.5W/m.k. then find the distance at which maximum heat dissipation will
occur.
4. A 1.5m×1.5m×2m tank is kept at 11m above from the ground. If a pump installed on ground
having efficiency of 60% can fill the tank in 30 min then , find the required pump power.
5. Show that , specific speed of pump is a dimensionless number.

6. Draw P-V & T-S diagram of otto & diesel cycle and write down the corresponding process
name.
7. Find the absolute pressure in Pa of 100mm mercury vacuum pressure
8. Engine power developed 40KW, solid shafts rpm 200 , if the shaft dia is 40 mm then find
maximum torsional stress developer in the shaft.
9. Find the deflection of a solid circular steel bar having load 500 kg, lenght 2.5 m, dia 60mm
& E=200 GPa
10. Draw block diagram & T-S diagram for gas- steam combine cycle power plant.
11. A 60 mm metal ball at 220℃ is being cooled by air jet of 20℃, heat transfer co-efficient
200 W/m.k & 100 W/m2
.K, if the specific heat of the metal ball 400 J/Kg.K, density
9000Kg/m3
, find the temperature of the ball after 90 sec.
12. An aeroplane makes a complete half circle of 50 metres radius, towards left,when flying at
200 km per hr. The rotary engine and the propeller of the plane has a mass of 400 kg and a
radius of gyration of 0.3 m. The engine rotates at 2400 r.p.m. clockwise when viewed from the
rear. Find the gyroscopic couple on the aircraft.
13. In a vapor compression refrigeration cycle inlet condenser enthalpy is 283 KJ/Kg, exit
condenser enthalpy is 116 KJ/Kg, exit evaporator enthalpy is 232 KJ/Kg, Find COP.
14. Draw all necessary orthrogrphic views of the following objects.
Solutions

1. A 4 cylinder petrol engine has developed MEP=650 KPa, it's engine dia is 80 mm, stroke
length is 100 mm, speed 3000 rpm. Find engine power in KW ?
Ans:
We know,
Indicated power, P =
𝑃𝐿𝐴𝑛𝐾
60
P =
650𝑥 0.1𝑥5.0265 x 10−3x1500𝑥4
60
P = 32.672 KW
Given data:
K= no of cylinder=4
P=MEP=Mean Effective Pressure = 650 KPa
d=dia=80 mm = .08 m
A = area =
𝜋
4
d2
=
𝜋
4
0.082
= cm2
L = stroke length = 100 mm = 0.1 m
N= speed = 3000 rpm
n = N/2 , for four stroke engine = 3000/2 = 1500
P = engine power (KW) = ?
2. For counter flow heat exchanger Th1=160℃, Th2=125℃, Tc1=20℃, Tc2=80℃ , Draw
temperature distribution curve. Also Find arithmetic mean temperature difference &
logarithmic mean temperature difference.
Ans:
We know,
AMTD= avg. hot temp. – avg. cold temp.
=
𝑇ℎ1+𝑇ℎ2
2
-
𝑇𝑐1+𝑇𝑐2
2
=
160+125
2
-
20+80
2
= 142.5-50 = 92.5℃
Again for LMTD,
∆T1 = Th1- Tc2 =160-80 = 80
∆T2 = Th2- Tc1 =125-20 = 105
we know,
LMTD =
∆T2−∆T1
ln
∆T2
∆T1
=
105−80
ln
105
80
=
25
ln
105
80
=
25
0.2719
= 91.93℃
Counter flow temperature
distribution:
Given data:
Th1=160℃
Th2=125℃
Tc1=20℃
Tc2=80℃
AMTD = ?
LMTD = ?
3. A wire has got dia of 20 mm, if heat transfer co efficient is 20 W/m2
.K and thermal
Conductivity is 0.5W/m.k. then find the distance at which maximum heat dissipation will
occur.
Ans: we know that at critical insulation of
thickness maximum heat dissipation will
occur.
distance = critical insulation of thickness =
𝑘
ℎ
=
0.5
20
= 0.025 m = 25 mm
Given data:
h= heat transfer co efficient= 20 W/m2
.K
K= thermal Conductivity = 0.5W/m.k
distance = ?

4. A 1.5m×1.5m×2m tank is kept at 11m above from the ground. If a pump installed on ground
having efficiency of 60% can fill the tank in 30 min then , find the required pump power.
Ans: Flow rate, Q=
4.5𝑚3
30𝑥60𝑠𝑒𝑐
= 2.5x10-3
m3
/s
we know, pump power , P =
𝛾𝐻𝑄
𝜂
=
9.81𝑥1000𝑥13𝑥2.5𝑥10^−3
0.6
=531.375 W
Alternate solution:
Pump power = mgh/ηt = 4500x9.81x13 / 0.6 30x60 = 531.375 W
Given Data:
v= Volume of tank = 1.5m×1.5m×2m = 4.5m3
m=mass= ⍴v = 1000 x 4.5 = 4500 Kg
elevation, h = 11+2 = 13 m [taking that pump has to lift
water from the ground to top of the tank]
η = efficiency = 60% = 0.6
time, t = 30 min = 30x60 sec
Required pump power, p = ?
5. Show that , specific speed of pump is a dimensionless number.
We know, H =
𝑉2
2𝑔
⇒ H ∝ V2
⇒ H =
𝑚2
𝑆2
specific speed,
Ns =
𝑁√𝑄
𝐻3/4
=
1
𝑠
𝑥 √(
𝑚3
𝑠
)
(
𝑚2
𝑠2 )^(
3
4
)
=
1
𝑠
𝑥 (
𝑚3/2
𝑠1/2 )
(
𝑚3/2
𝑠3/2 )
=
𝑠3/2
𝑠3/2 = 1
Thus, specific speed of pump is
dimensionless number.
6. Draw P-V & T-S diagram of otto & diesel cycle and write down the corresponding process
name.

7. Find the absolute pressure in Pa of 100mm mercury vacuum pressure.
Ans:
Abs. pressure = atm. pressure – vacuum pressue = 760 – 100 = 660 mm of mercury
P = h⍴g = 0.660 x 13.6 x 1000 x 9.81= 88054.56 Pa
8. Engine power developed 40KW, solid shafts rpm 200 , if the shaft dia is 40 mm then find
maximum torsional stress developer in the shaft.
Ans:
We know , power P = Tω = T . 2πN/60
T = 60P/2πN = 60x 40x 1000/ 2π . 200 =
1909.85 Nm
Again, Maximum stress, τmax =
16𝑇
π d3
=
16𝑥 1909.85
π (0.04)3
= 151.98 MPa
Given data:
P = power= 40 KW
N = speed = 200 rpm
d= dia = 40 mm = 0.04 m
τmax = ?
9. Find the deflection of a solid circular steel bar having load 500 kg, lenght 2.5 m, dia 60mm
& E=200 GPa
Ans:
We know, deflection , δ =
𝑃𝐿
𝐴𝐸
=
4905𝑥 2.5
2.82x 10^−3x 200 x 10^9
= 0.0217 mm
Given data:
P= load = 500x9.81 N = 4905 N
L = length = 2.5 m
d= 60 mm = 0.06 m
A= cross sectional area =
𝜋
4
d2
=
𝜋
4
(.06)2
=
2.82x 10-3
m2
E = 200 Gpa = 200 x 109
Pa
10. Draw block diagram & T-S diagram for gas- steam combine cycle power plant.

11. A 60 mm metal ball at 220℃ is being cooled by air jet of 20℃, heat transfer co-efficient
200 W/m.k & 100 W/m2
.K, if the specific heat of the metal ball 400 J/Kg.K, density
9000Kg/m3, find the temperature of the ball after 90 sec.
Ans:
We know ,
T90s - Tα
= e
-(
ℎ𝐴
⍴𝐶𝑉
) 𝑡
Ti - Tα
T90s - 20
= e
-(
100𝑥4πr2
9000𝑥400𝑥
4
3
𝜋𝑟3
) 𝑥 90
220- 20
T90s - 20
= e
-(
100𝑥3
9000𝑥400𝑥 0.03
) 𝑥 90
200
T90s - 20
= e
-0.25
200
T90s = 200x0.7788 +20 = 155.76+20
= 175.76℃
Given Data:
d= 60 mm = .06 m
r = d/2 = .03 m
A= surface area of metal ball = 4πr2
V = volume of metal ball =
4
3
πr3
Ti = initial temp. = 220℃
Tα = 20℃
K= 200 W/m.K
h= 100 W/m2
.K
C = 400 J/Kg.K
⍴ = 9000 Kg/m3
t = 90 sec
temp. after 90 sec, T90s = ?
12. An aeroplane makes a complete half circle of 50 metres radius, towards left,when flying at
200 km per hr. The rotary engine and the propeller of the plane has a mass of 400 kg and a
radius of gyration of 0.3 m. The engine rotates at 2400 r.p.m. clockwise when viewed from the
rear. Find the gyroscopic couple on the aircraft.
Ans:
we know, ω = 2πN/60 = 2π x 2400 /60
= 251 rad /s
Moment of inertia,
I = mK2
= 400 x 0.32
= 36 Kg-m2
Angular velocity of precession,
ωp = V/R = 55.556 / 50 = 1.11 rad/sec
Gyroscopic couple , C = I.ω.ωp
= 36 x 251 x 1.11 = 10.046 KN-m
Given Data:
R = 50 m
V= 200 Km / hr = 55.556 m/s
m= 400 Kg
K = 0.3 m
N = 2400 rpm
gyroscopic couple, C = ?

13. In a vapor compression refrigeration cycle inlet condenser enthalpy is 283 KJ/Kg, exit
condenser enthalpy is 116 KJ/Kg, exit evaporator enthalpy is 232 KJ/Kg, Find COP.
Ans:
We have,
COP =
𝐶𝑜𝑜𝑙𝑖𝑛𝑔 𝑒𝑓𝑓𝑒𝑐𝑡
𝑐𝑜𝑚𝑝𝑟𝑒𝑠𝑠𝑜𝑟 𝑤𝑜𝑟𝑘
=
ℎ1−ℎ4
ℎ2−ℎ1
=
232−116
283−232
=
116
51
= 2.2745
Given Data:
According to the P-h figures,
h2= enthalpy at inlet of condenser = 283 KJ/Kg
h3= h4= enthalpy at exit of condenser = 116 KJ/Kg
h1= enthalpy at the inlet of compressor = 232 KJ/Kg
14. Draw all necessary orthrogrphic views of the following objects.

Md. Iqbal Hussain
B. Sc in Mechanical Engineer, RUET
Email: iqbal092067@gmail.com
Emran Hossain
Email:emran.ruet@gmail.com
Tafhimul Hossain Siddiqi
B. Sc in Mechanical Engineer, CUET
Email: tafhim.hossain@gmail.com
Abdul Aziz
B. Sc in Mechanical Engineer, IUT
Email: azizfuad111439@gmail.com
Swadip Chandra Shil
Email: swadip87@gmail.com
Rashedur Rahman
Email: rashed.ruet09@gmail.com
Arnab Das
B. Sc in Mechanical Engineer, KUET
Email: arnabs2009@gmail.com
Wasek Ahmed Atul
Email: wasekahmed07@gmail.com

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