DE-4 HEAT AND MASS TRANSFER
1. Heat conduction in gases occur by
2. Two dimension unsteady-state temperature field is
3. Which of the following is not the property of ‘Isothermal surface’?
4. Temperature gradient is a
5. The relationship q= -? (?t/??) is called
6. The unit for thermal resistance is:
7. Design formula for conduction in a plane wall is given by:
8. Thermal conductivity of liquids range from:
9. Thermal conductivity of steel is 45 kcal/m-hr-°C for carbon content
10. 70 W/m2 of heat flows through a plane wall of thickness 50 mm, having = 70 W/m°C thermal conductivity. The temperature gradient is
11. Temperature curve in a plane homogenous wall is:
12. The relationship between thermal conductivity and temperature in most materials is:
13. Equivalent thermal resistance depend only on:
14. Hourly loss of heat through a brick wall 4 m long, 2 m high and 250 mm thick, having surface temperatures 20°C and -30°C, ? = 0.6 kcal/m-hr-°C is
15. If q = 1000 kcal/m2-hr, ? = 30 mm and t = 30°C, then ? in kcal/m-hr-°C is
16. Surfaces of a flat wall are maintained at 1000°C and 0°C and ? = 1.0 (1 + 0.001 t). Mean thermal conductivity is:
17. Thermal conductivity of the material of a wall 40 mm thick, maintaining t = 20°C, with heat flow 145 W/m2 is
18. Temperature distribution curve inside a homogenous cylindrical wall varies along a
19. Heat flow through a cylindrical wall is inversely proportional to
20. The concept of heat flowing through a unit of inner or outer surface area is applicable for
21. Temperature distribution curve of a composite cylindrical wall can be established only if
22. Which is not true for convection heat transfer?
23. The kind and physical properties of fluid play dominating role in:
24. Which is not true of critical velocity?
25. Friction force per unit contact area between two layers of fluid sliding past one another, is called
26. What is not true?
27. The unit of heat transfer co-efficient is:
28. The concept of overall heat transfer co-efficient is based on
29. Heat transfer co-efficient is a function of
30. Which differential equation describes heating and cooling at the boundaries of the substance
31. Temperature distribution in the field can be obtained form
32. Differential equation of conduction is based on
33. Which is not true for convection heat transfer?
34. The kind and physical properties of fluid play dominating role in:
35. Which is not true of critical velocity?
36. Frictional force per unit contact area between two layers of fluid sliding past one another, is called
37. Which is not the condition of unambiguity?
38. Factor of similarity transformation depends on
39. Hydromechanical similarity involves
40. Grashoff number is identical to
41. Criteria equation for steady state forced flow is
43. Reference temperature in a heat transfer process is
44. Which is not true of empirical formulas?
45. If A = 1, R = 0, D = 0, then body is defined as
46. Solids and liquids which are practically non transparent to heat rays, in such cases:
47. Emission of the body proper depends on:
48.
49. Energy emitted by a body in all directions is determined by:
50. The relationship between emissivity and absorptivity of a body is given by
51. Steam boiler is a heat exchange of the type
52. Heat exchange in which one and the same heating surface is alternately exposed to the hot and cold fluids is:
53. Water-cooling towers are heat exchangers of the type
54. Water equivalent of heat carrier is given by:
55. Heat exchanges in which two liquids are directed at right angles to each other are called
56. 250 litres of hot fluid of gravity 100 kg/m3 and heat capacity 0.727 kcal/kg-oC, will have its water equivalent
57. Which is not true for fins?
58. An extended surface attached circumferentially to a cylindrical surface is an example of
59. The circumferential fins used on the engine cylinder of scooters and motorcycles are of
is based on