Question Set 114

1. What is LMTD method?

Answer: LMTD means logarithmic mean temperature difference. Generally, it is used to measure the heat transfer of the flow systems. In most cases, the lmtd method is used to measure the heat transfer in heat exchangers most commonly in double pipe heat exchangers. Here is the mathematical expression of lmtd method –

ΔTA is the temperature difference between the two fluids at the one end denoted by A. ΔTB is the temperature difference between the two streams of fluids at end B.

Amount of heat exchanged in a heat exchanger can be calculated from this equation –

2. What is Gear Train? Describe Gear Train formula.

Answer: Gear or cogwheel is a mechanical device which is used to transmit torque. A gear generally meshes with another gear by means of the tooth. In gear train, two or more gears are mounted on a frame for transmitting power. In the figure,  you can see the typical gear train arrangement.

3. What is Cam?

Answer: Cam is a mechanical linkage which transforms rotary motion to linear motion and vice versa. Cams can be very versatile. The most common use of cam is seen in automobile camshaft.

4. What is CAD?

Answer: CAD means Computer Aided Design. This is a system in which computer systems are used to create, modify analyse or optimize a design.  CAD files generally give an output which can be used for printing, machining and manufacturing processes.  CAD improves the productivity of a designer as well as improve the accuracy of machining. Documentation for drawing and design has become very easy by means of CAD as it helps to keep the database updated very easily. Before CAD it was very much arduous to keep the database up to date with drawings and designs. These CAD drawings can be used in CNC machine for manufacturing a product in very short time.

5. What is STUD, BOLT and NUT?

Answer:

Bolts are generally externally threaded fasteners which are inserted into a hole and tighten up by means of nuts.

Screws are generally externally threaded fasteners which are inserted into a hole which is internally threaded. No additional nuts are needed to tighten up the screws.

Studs are bolts which are threaded on both ends and tightened up by using nuts on the threaded ends to hold a part.

6. What is Shear Stress and Normal Stress?

Answer: There are two types of stress that can be developed inside a material. Normal stress and shear stress. The stress which is developed in a direction perpendicular to the face is known as normal stress. The stress which is developed in a direction parallel to the face is known as shear stress.

7. What is boiler draught?

Answer: It is a process of supplying continuous air to the boiler furnace for efficient burning of the fuel for producing steam.  It is actually the pressure difference between the grate level hot flue gases and the exit point gases. Draught can be natural or forced.

8. What are the different types of gearboxes?

Answer: There are 4 types of gearboxes used in the machines and mechanisms

· Sliding Mesh Gear Box

· Synchromesh Gear Box

· Constant Mesh Gear Box

· Planetary Gear Box