Question Set 13

Question No. 1

What is a Newtonian fluid?


A Newtonian fluid possesses a linear stress strain relationship curve and it passes through the origin. The fluid properties of a Newtonian fluid do not change when any force acts upon it.

Question No. 2

What are the causes of failure of superheater tubes?


Superheater tubes are subjected to the most severe combination of stress, temperature and corrosive environment. In addition to high temperature strength, resistance to corrosion is also important. For example, low alloy ferrite steel such as 1% Cr, 1% Mo would not be used at metal temperatures above 580°C because of inadequate resistance to corrosion and oxidation over a full service life of 100,000/150,000 hr.

Failures in superheater tubes may arise from:

(A) Prior fabrication history

(B) Faulty heat treatment

(C) Consequences of welding

(D) Overheating of the tube metal

(E) Gas-side corrosion

(F) Stress corrosion (austenitic steels).

Question No. 3

Why supercritical boilers use less amount of steel compared to non supercritical boilers?


Supercritical boilers do not head heavy drum for separation of steam from mixture of water and steam.

Question No. 4

What does a pump develops? Flow or Pressure?


A pump does not create pressure, it only creates flow. Pressure is a measurement of the resistance to flow.

Question No. 5

What is a Hydrostatic system?


Hydrostatics is the study of fluid bodies that are

(A) At rest

(B) Moving sufficiently slowly so there is no relative motion between adjacent parts of the body

For hydrostatic situations

(A) There are no shear stresses.

(B) There are only pressure forces that act perpendicular to any surface.

It’s a closed loop hydraulic systems. It comprises of motor and pump. Here pump supplies energy to motor and motor gives return energy to pump supply.

Question No. 6

What is the difference between Blower and Fan?


Fan is an air pushing device. Either Axial or Centrifugal type systems are used to move the air in low pressure. It is rotated by a motor separately.

When the fan is a housing of blades and motor, then it called as Blower. It directs the air in a single path with high pressure.

Question No. 7

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


Heat pump.

Question No. 8

What is Hydrodynamic Cavitation?


Hydrodynamic Cavitation describes the process of vaporization in a constrained channel at a specific velocity. Bubble generation and Bubble implosion which occurs in a flowing liquid as a result of a decrease and subsequent increase in pressure.

Question No. 9

Is gate valve used for Throttling?


Gate valves are not suitable for throttling because the control of flow is difficult for the valve’s design, and the flow of fluid slapping against a partially open gate can cause extensive damage to the valve.

Question No. 10

Where Multi-stage pump used?


Pressure washing of Aircraft, Trains, Boats and Road vehicles as well as Spray washing of industrial parts and Electronic components.

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