Thapar University 2006 B.E Mechanical Engineering Heat & Mass Transfer - Question Paper
Thapar Institute of Engineering & Technology
BE (4th Year)
Final Term exam
ME009 (Heat & Mass Transfer)
THAPAR INSTITUTE OF ENGINEERING AND TECHNOLOGY PATIALA DEPARTMENT OF MECHANICAL ENGINEERING End Semester Examination, December-2006 B.E, 4Ih Year (Backlog)
Course: ME 009 (Heat and Mass Transfer) Instructor: Satish Kumar
Max Marks-36 Time-3 hours
Note: Section A is compulsory. Attempt any four questions from Section B.
_Assume suitable data wherever necessary. See your answer sheets on 12/12/06_
Scction-A
1 (a) A hollow sphere of inside radius 2.5cm and outside radius 7.5cm has corresponding surface temp of 300C and 25C.caculate the heat loss by conduction if thermal conductivity of sphere material is 15 kcl/m-hr-deg-k (4)
(b) Define the following (i) Critical radius (ii) Fins (iii) solid angle (v) Diffuse Surface (4)
Scction-B
Q.2 (a) A thin shield of emissivity s (on both sides) is placed between two infinite parallel plates of emissivities 1 and 2, and temperature T1 and T2 respectively. If l=2=3. show that temperature of the shield is given by:
[(Tl 4 + T1 4)/2] Va (5)
(b) A stainless steel plate =0.6 at I00C faces a brick wall (=0.75) 500C. Estimate the heat flux and the radiant heat transfer coefficient. (2)
Q.3 (a) A metal (k=45w/m-deg)stcam pipe 5cm internal dia and 6.5cm external dia is lagged with a2.75cm radial thickness of high temp insulation having thermal conductivity of l.lw/m-deg.the surface heat transfer coefficient for inside and outside arc 4650 and 11.Sw/m-deg.if the steam temp is 200c and the ambient temp is 25c then calculate.
(i) heat loss per meter length of the pipe
(ii) temp of the interfaces
(iii)overall coefficient of heat transfer referred to inside and outside surfaces (5)
(b) Define thermal diffusity and explain its physical significance. (2)
Q.4 Heat transfer coefficient depends upon the following parameters: fluid viscosity, density, thermal Conductivity, specific he#, (pgAt) length. By using dimensional analysis establish the correlation. (7)
Q.5 (a) A Steam pipe50 mm dia and 2.5 m long has been placed horizontally and exposed to still air at 25C. If the pipe wall temp is 295C, determine the rate of heat loss. At the mean temp the properties of air are: v =30.9 * 10"6 m2/sec, K=3.64* 10'2W/m-deg, Pr=0.682.
Use the correlation Nu=0.53(GrPr)I/4 (4)
(b) Define Nusselt Number, Grashoff Number, Prandtl Number and explain it physical significance. (3)
Q. 6 (a) Derive an expression for the effectiveness of a counter flow heat exchanger (4)
(b) Differentiate between nucleate and film boiling with neat sketch. (3)
|
Attachment: |
| Earning: Approval pending. |
