www.jntuworld.com www.jwjobs.net Code No: 07A5EC06 Set No. 1 JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD III B.Tech. I Sem., I Mid-Term Examinations, September – 2010 HEAT TRANSFER Objective Exam Name: ______________________________ Hall Ticket No. A I 1. 2. Choose the correct alternative: The average thermal conductivities of water and air conform in the ratio (A) 15:1 (b) 5:1 (c) 50:1 (d) 25:1 [ Answer All Questions. All Questions Carry Equal Marks.Time: 20 Min. Marks: 20. ] Thermal conductivity ’K’ and electrical conductivity ‘C’ of metal at absolute temperature ’T’ are related as [ ] (a) K/CT=constant (b) KC/T=constant (c) KT/C=Constant (d) K/C= constant The temperature distribution(t-ta)/( to - ta) for a fin with insulated is given by (a) Coshm (l-x)/coshml (b) exp (mx) +exp (-mx)/2 (c) coshm (l-x) +coshml (d) exp (-mx) An increasing a conductive coefficient over a fin (a) Decreasing effectiveness (b) Increasing effectiveness (c) Does not influence effectiveness (d) influence only in efficiency 3. 4. 5. 6. Lumped parameter analysis for transient heat conduction is essentially valid for (a) 0.1< Bi <0.5 (b) Bi ∞ (c) Bi < 0.1 (d) 1 < Bi <10 The temperature distribution, at a certain instant of time, in a concrete slab during is given by T= 3x2 + 3x +16 where x is cm and T is in degree Kelvin The rate of change of temperature with time would then be (Assume thermal diffusivity to be 0.003 cm2/ s) in K/s [ ] (a) -0.0018 (b) -0.0012 (c) 0.0045 (d) 0.0009 A composite slab as two layers of different materials with thermal conductivities k1 and K2. If each layer has same thickness the equivalent thermal conductivity of slab will be [ ] (b) k1 +k2 (c) k1 +k2 / k1 k2 (d) 2 k1 k2 /( k1 +k2) (a) k1 k2 Nusselt number in natural transfer is function of fluid and (a) Prandtl number, Reynolds number (b) prandtl number, Grashof number (c) prandtl number, Stanton number (d) prandtl number Biot number The critical radius is the insulation radius at the resistance to heat flow is (a) Maximum (b) minimum (c) zero (d) Infinity [ ] 7. J T N W U R O D L [ ] [ ] [ ] 8. 9. 10. [ ] For a metallic wall at 100 C a metal rod protrudes to the ambient air. The temperature at at the tip is will be minimum when the rod is made of [ ] (a) Aluminum (b) copper (c) steel (d) silver Cont…..2 www.jntuworld.com 12.those for liquids Cork is good insulator because it is -------------------- Thermal conductivity of copper-----------. 14.www.1 The basic law of heat conduction is called ---------------Fins are usually provided to a heat exchangers in order to argument heat transfer by increasing the ----------Thermal conductivity of solid metal --------with rise in temperature In critical radious of insulation for sphere is equal to-----------Peclet number is ratio of ---------The units of heat transfer coefficient (h) in m.net Code No: 07A5EC06 II 11.with rise in in temperature The units of thermal diffusivity is------------- J T N W U -oOo- R O D L www. 15. 19.jntuworld. 16 17 18.k.com .jwjobs. is ----------------- The thermal diffusivity for gases is generally -----------------.s.jntuworld. 13. Fill in the blanks: :2: Set No.com www. 20. Thermal conductivity ’K’ and electrical conductivity ‘C’ of metal at absolute temperature ’T’ are related as [ ] (a) K/CT=constant (b) KC/T=constant (c) KT/C=Constant (d) K/C= constant The temperature distribution(t-ta)/( to . The temperature at at the tip is will be minimum when the rod is made of [ ] (a) Aluminum (b) copper (c) steel (d) silver The average thermal conductivities of water and air conform in the ratio (A) 15:1 (b) 5:1 (c) 50:1 (d) 25:1 [ ] J T N W U R O D L [ ] [ ] 8. A I 1.5 (b) Bi ∞ (c) Bi < 0. I Mid-Term Examinations.com www.jwjobs.0018 (b) -0. September – 2010 HEAT TRANSFER Objective Exam Name: ______________________________ Hall Ticket No. If each layer has same thickness the equivalent thermal conductivity of slab will be [ ] (a) k1 k2 (b) k1 +k2 (c) k1 +k2 / k1 k2 (d) 2 k1 k2 /( k1 +k2) Nusselt number in natural transfer is function of fluid and (a) Prandtl number.com .Tech. 6..ta) for a fin with insulated is given by (a) Coshm (l-x)/coshml (b) exp (mx) +exp (-mx)/2 (c) coshm (l-x) +coshml (d) exp (-mx) [ ] 10. ] 2. at a certain instant of time. Choose the correct alternative: An increasing a conductive coefficient over a fin (a) Decreasing effectiveness (b) Increasing effectiveness (c) Does not influence effectiveness (d) influence only in efficiency Lumped parameter analysis for transient heat conduction is essentially valid for (a) 0..2 www. For a metallic wall at 100 C a metal rod protrudes to the ambient air.net Code No: 07A5EC06 Set No. Cont…. I Sem.0012 (c) 0. Reynolds number (b) prandtl number. 5.003 cm2/ s) in K/s [ ] (a) -0. [ ] The temperature distribution. Stanton number (d) prandtl number Biot number The critical radius is the insulation radius at the resistance to heat flow is (a) Maximum (b) minimum (c) zero (d) Infinity 4. Grashof number (c) prandtl number. All Questions Carry Equal Marks. 3. 9. in a concrete slab during is given by T= 3x2 + 3x +16 where x is cm and T is in degree Kelvin The rate of change of temperature with time would then be (Assume thermal diffusivity to be 0.0009 A composite slab as two layers of different materials with thermal conductivities k1 and K2.www.0045 (d) 0. Marks: 20.1< Bi <0.Time: 20 Min.jntuworld.jntuworld. 7.1 (d) 1 < Bi <10 [ Answer All Questions. 2 JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD III B. 17. Fill in the blanks: :2: Set No. 18.with rise in in temperature The units of thermal diffusivity is------------The basic law of heat conduction is called ---------------- Fins are usually provided to a heat exchangers in order to argument heat transfer by increasing the ----------Thermal conductivity of solid metal --------with rise in temperature J T N W U -oOo- R O D L www.net Code No: 07A5EC06 II 11. 19.www. is -------------------The thermal diffusivity for gases is generally -----------------. 13 14 15.jntuworld. 12. 20.com www.k.s.com .jntuworld.jwjobs.2 In critical radious of insulation for sphere is equal to-----------Peclet number is ratio of ---------The units of heat transfer coefficient (h) in m.those for liquids Cork is good insulator because it is -------------------Thermal conductivity of copper-----------. 16. 5. Grashof number (c) prandtl number. The temperature distribution. at a certain instant of time. in a concrete slab during is given by T= 3x2 + 3x +16 where x is cm and T is in degree Kelvin The rate of change of temperature with time would then be (Assume thermal diffusivity to be 0.1 (d) 1 < Bi <10 (a) 0. All Questions Carry Equal Marks.www. Reynolds number (b) prandtl number.5 [ ] J T N W U R O D L [ ] [ ] [ ] 8. Stanton number (d) prandtl number Biot number The critical radius is the insulation radius at the resistance to heat flow is (a) Maximum (b) minimum (c) zero (d) Infinity 2. Choose the correct alternative: Answer All Questions.net Code No: 07A5EC06 Set No.0009 A composite slab as two layers of different materials with thermal conductivities k1 and K2. 7.Tech..com . For a metallic wall at 100 C a metal rod protrudes to the ambient air.jntuworld. 4.0045 (d) 0. [ ] 10. 9. 3 JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD III B.2 www. Thermal conductivity ’K’ and electrical conductivity ‘C’ of metal at absolute temperature ’T’ are related as [ ] (a) K/CT=constant (b) KC/T=constant (c) KT/C=Constant (d) K/C= constant The temperature distribution(t-ta)/( to . [ ] Cont….jwjobs. A I 1.0012 (c) 0. I Mid-Term Examinations. If each layer has same thickness the equivalent thermal conductivity of slab will be [ ] (a) k1 k2 (b) k1 +k2 (c) k1 +k2 / k1 k2 (d) 2 k1 k2 /( k1 +k2) Nusselt number in natural transfer is function of fluid and (a) Prandtl number.Time: 20 Min.ta) for a fin with insulated is given by (a) Coshm (l-x)/coshml (b) exp (mx) +exp (-mx)/2 (c) coshm (l-x) +coshml (d) exp (-mx) An increasing a conductive coefficient over a fin (a) Decreasing effectiveness (b) Increasing effectiveness (c) Does not influence effectiveness (d) influence only in efficiency Lumped parameter analysis for transient heat conduction is essentially valid for (b) Bi ∞ (c) Bi < 0. The temperature at at the tip is will be minimum when the rod is made of [ ] (a) Aluminum (b) copper (c) steel (d) silver The average thermal conductivities of water and air conform in the ratio (A) 15:1 (b) 5:1 (c) 50:1 (d) 25:1 6.jntuworld.1< Bi <0.003 cm2/ s) in K/s [ ] (a) -0.0018 (b) -0. Marks: 20. I Sem.com www. September – 2010 HEAT TRANSFER Objective Exam Name: ______________________________ Hall Ticket No. 3.. with rise in in temperature The units of thermal diffusivity is------------The basic law of heat conduction is called ---------------Fins are usually provided to a heat exchangers in order to argument heat transfer by increasing the ----------Thermal conductivity of solid metal --------with rise in temperature In critical radious of insulation for sphere is equal to-----------Peclet number is ratio of ---------- J T N W U -oOo- R O D L www.www.k.com .jwjobs. 17.jntuworld. 15. 20. is ----------------The thermal diffusivity for gases is generally -----------------.net Code No: 07A5EC06 II 11 12 13.3 The units of heat transfer coefficient (h) in m.those for liquids Cork is good insulator because it is -------------------Thermal conductivity of copper-----------. 16. Fill in the blanks: :2: Set No. 19. 14.jntuworld.s.com www. 18. I Mid-Term Examinations.jwjobs.0012 (c) 0.. www. Reynolds number (b) prandtl number.com www.www.003 cm2/ s) in K/s [ ] (a) -0. 9.Tech.ta) for a fin with insulated is given by (a) Coshm (l-x)/coshml (b) exp (mx) +exp (-mx)/2 (c) coshm (l-x) +coshml (d) exp (-mx) An increasing a conductive coefficient over a fin (a) Decreasing effectiveness (b) Increasing effectiveness (c) Does not influence effectiveness (d) influence only in efficiency Lumped parameter analysis for transient heat conduction is essentially valid for (a) 0. 8.jntuworld. September – 2010 HEAT TRANSFER Objective Exam Name: ______________________________ Hall Ticket No. 4 JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD III B. Choose the correct alternative: Nusselt number in natural transfer is function of fluid and (a) Prandtl number. Stanton number (d) prandtl number Biot number The critical radius is the insulation radius at the resistance to heat flow is (a) Maximum (b) minimum (c) zero (d) Infinity [ Answer All Questions. I Sem. If each layer has same thickness the equivalent thermal conductivity of slab will be [ ] (b) k1 +k2 (c) k1 +k2 / k1 k2 (d) 2 k1 k2 /( k1 +k2) (a) k1 k2 Cont…. ] 2.0009 A composite slab as two layers of different materials with thermal conductivities k1 and K2. in a concrete slab during is given by T= 3x2 + 3x +16 where x is cm and T is in degree Kelvin The rate of change of temperature with time would then be (Assume thermal diffusivity to be 0.5 (b) Bi ∞ (c) Bi < 0. J T N W U R O D L [ ] [ ] [ ] [ ] The temperature distribution. at a certain instant of time.0018 (b) -0. All Questions Carry Equal Marks. 7. Thermal conductivity ’K’ and electrical conductivity ‘C’ of metal at absolute temperature ’T’ are related as [ ] (a) K/CT=constant (b) KC/T=constant (c) KT/C=Constant (d) K/C= constant The temperature distribution(t-ta)/( to .net Code No: 07A5EC06 Set No.com .1 (d) 1 < Bi <10 6. [ ] For a metallic wall at 100 C a metal rod protrudes to the ambient air.. A I 1.Time: 20 Min. Grashof number (c) prandtl number. 5.jntuworld. The temperature at at the tip is will be minimum when the rod is made of [ ] (a) Aluminum (b) copper (c) steel (d) silver The average thermal conductivities of water and air conform in the ratio (A) 15:1 (b) 5:1 (c) 50:1 (d) 25:1 4.2 10. 3.1< Bi <0. Marks: 20.0045 (d) 0. 15.jwjobs. 16.com .jntuworld.www.jntuworld. 13. 17. Fill in the blanks: :2: Set No. is -------------------- The thermal diffusivity for gases is generally -----------------.4 Cork is good insulator because it is -------------------Thermal conductivity of copper-----------. 14.with rise in in temperature The units of thermal diffusivity is------------The basic law of heat conduction is called ---------------Fins are usually provided to a heat exchangers in order to argument heat transfer by increasing the ----------Thermal conductivity of solid metal --------with rise in temperature In critical radious of insulation for sphere is equal to-----------Peclet number is ratio of ---------- The units of heat transfer coefficient (h) in m.those for liquids J T N W U -oOo- R O D L www. 18. 12. 19 20.com www.s.net Code No: 07A5EC06 II 11.k.