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

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Biman Bangladesh airlines ltd 's recruitment exam was held on 13th July 2018. Here is the solution of mechanical engineering question. Exam was held in MIST.
Hope this will be a great help to those who wants to do better in engineering job field of Bangladesh.

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

  1. 1. 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.
  2. 2. 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 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
  3. 3. 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 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. 4. 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 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.
  5. 5. 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 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.
  6. 6. 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 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 = ?
  7. 7. 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 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.
  8. 8. Md. Iqbal Hussain B. Sc in Mechanical Engineer, RUET Email: iqbal092067@gmail.com Emran Hossain B. Sc in Mechanical Engineer, RUET 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 B. Sc in Mechanical Engineer, RUET Email: swadip87@gmail.com Rashedur Rahman B. Sc in Mechanical Engineer, RUET Email: rashed.ruet09@gmail.com Arnab Das B. Sc in Mechanical Engineer, KUET Email: arnabs2009@gmail.com Wasek Ahmed Atul B. Sc in Mechanical Engineer, RUET Email: wasekahmed07@gmail.com

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