Question Set 21

Q21. What is ductile-brittle transition temperature?

Answer – It is the temperature below which the tendency of a material to fracture increases rather than forming. Below this temperature, the material loses its ductility. It is also called Nil Ductility Temperature.

Q22. On which analysis is based the Dulong’s formula for the heating value of fuel?

Answer – On ultimate analysis.

Q23. Which element causes a difference in higher and lower heating values of fuel?

Answer – Hydrogen.

Q24. What is a uniformly distributed load?

Answer – A UDL or uniformly distributed load is a load, which is spread over a beam in such a way that each unit length is loaded to the same extent.

Q25. How is martensite structure formed in steel?

Answer – Martensite transformation begins when austenite is cooled below a certain critical temperature, called the martensite start temperature. As we go below the martensite start temperature, more and more martensite forms and complete transformation occurs only at a temperature called martensite finish temperature. Formation of martensite requires that the austenite phase must be cooled rapidly.

Q26. Which two elements have the same percentage in the proximate and ultimate analysis of coal?

Answer – Moisture and ash.

Q27. What is an orthographic drawing?

Answer – Orthographic projections are views of a 3D object, showing 3 faces of it. The 3 drawings are aligned so that if the page were folded, it would create part of the shape. It is also called multiview projections.
The 3 faces of an object consist of its plan view, front view and side view. There are 2 types of orthographic projection, which are 1st angle projection and 3rd angle projection.

Q28. Which reactor has no moderator? Ans: Fast breeder reactor

Answer – Fast breeder reactor

Q29. What is representative elementary volume?

Answer – Smallest volume over which measurements can be made that will yield a representative of the whole.

Q30. Ultimate analysis of coal is elementary analysis. What is it concerned with?

Answer – Carbon, hydrogen, nitrogen, and sulphur in coal on a weight percentage basis.

Q31. Why are LNG pipes curved?

Answer – LNG pipes are curved because LNG is condensed gas (-164 deg cel) so it can expand the pipes that are what engineers designed the LNG pipes are the curved type.

Q32. Quantities like pressure, temperature, density, viscosity, etc. are independent of mass. What are these called?

Answer – Intensive properties.

Q33. What does angular momentum mean?

Answer – Angular momentum is an expression of an object’s mass and rotational speed. Momentum is the velocity of an object times it is mass, or how fast something is moving how much it weigh. Therefore, angular momentum is the object’s mass times the angular velocity where the angular velocity is how fast something is rotating expressed in terms like revolutions per minute or radians per second or degrees per second.

Q34. What is the effect of inter cooling in gas turbines? 

Answer – It decreases thermal efficiency but increases net output

Q35. Can you use motor oil in a hydraulic system?

Answer – Hydraulic fluid has to pass a different set of standards than motor oil. Motor oil has tackifiers, lower sulfur content, and other ingredients that could prove harmful to the seals and other components in a hydraulic system. If it is an emergency only should do it.

Q37. What is the effect of friction on the flow of steam through a nozzle?

Answer – To decrease both mass flow rate and wetness of steam

Q38. What causes white smoke in two-stroke locomotive engines?

Answer – That is the engine running too lean (lack of fuel). This condition will lead to overheating and failure of the engine.

Q39. Out of electric heater and heat pump, which is economical in operation ?

Answer – Heat pump.

Q40. What is the role of nitrogen in welding?

Answer – Nitrogen is used to prevent porosity in the welding member by preventing oxygen and air from entering the molten metal during the welding process. Other gasses are also used for this purpose such as Argon, Helium, Carbon Dioxide, and the gasses are given off when the flux burns away during SMAW (stick) welding.

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