Question Set 29

Question No. 1

Explain the difference between AFBC, BFBC, PFBC and CFBC in regard to fluidized bed technologies.


AFBC (Atmospheric fluidized bed combustion) process consists of forming a bed of inert materials like finely sized ash or ash mixed with sand, limestone (for sulfur removal), and solid fuel particles in a combustor and fluidising it by forcing combustion air up through the bed mixture. The gas flows through bed without disturbing particles significantly but gas velocity is high enough to support the total weight of bed (fluidisation). At slightly higher velocity excess gas passes through the bed as bubbles (fluidized bed) and gives the bed the appearance of a boiling liquid.

BFBC (Bubbling fluidized bed combustion) has a defined height of bed material and operates at or near atmospheric pressure in the furnace.

PFBC (Pressurized fluidized bed combustion) system operates the bed at elevated pressure. Exhaust gases have sufficient energy to power a gas turbine, of course, gases need to be cleaned.

In fluidized combustion, as ash is removed some unburned carbon is also removed resulting in lower efficiency.

CFBC (circulating fluidized bed combustion) system, bed is operated at higher pressure leading to high heat transfer, higher combustion efficiency, and better fuel feed.Circulating fluidized beds operate with relatively high gas velocities and fine particle sizes. The maintenance of steady state conditions in a fastfluidized bed requires the continuous recycle of particles removed by the gas stream (circulating bed). The term circulating bed is often used toinclude fluidized bed systems containing multiple conventional bubbling beds between which bed material is exchanged.

Question No. 2

What is the difference between nuclear fission and fission chain reaction?


The process of splitting of nucleus into two almost equal fragments accompanied by release of heat is nuclear fission. Self sustained, continuing, sequence of fission reactions in a controlled manner is fission chain reaction.

Question No. 3

What is BHP?


Brake horsepower is the amount of work generated by a motor under ideal conditions. This work is calculated without the consideration of effects of any auxiliary component that may slow down the actual speed of the motor. Brake horsepower is measured within the engines output shaft and was originally designed to calculate and compare the output of steam engines.

As per the conventions, 1 BHP equals to:

(1) 745.5 watts

(2) 1.01389 ps

(3) 33,000 ft lbf/min

(4) 42.2 BTU/min

Question No. 4

Which parameter remains constant in a throttling process?



Question No. 5

What is the difference between isentropic process and throttling process?


In isentropic process, heat transfer takes place and in throttling process, enthalpy before and after the process is same.

Question No.6

What is D-4D Technology used in Toyota Vigo?


D-4D is widely recognized as one of the most advanced diesel technologies on the market today. Diesel engines relied on relatively simple technology with a low-pressure mechanical injector delivering fuel to a pre-combustion chamber in the cylinder head where a single ignition fired by the intense heat of high compression takes place.

Question No. 7

What for Schmidt plot for is used in heat transfer problems?


Schmidt plot is a graphical method for determining the temperature at any point in a body at a specified time during the transient heating or cooling period.

Question No. 8

What is ATFT Technology used in Honda Hunk?


ATFT means Advance Tumble Flow Induction Technology, Tumble flow means swirling. In this technology, fuel air mixture from the carburettor into the engine cylinder with a swirl action. The advantage being one gets a more efficient burning of fuel hence more power and better fuel economy with lesser emissions.

Question No. 9

What is big advantage of fast breeder reactor?


It has rapid self breeding of fissile fuel during the operation of the reactor, and thus, it offers about sixty times the output with same natural uranium resources through ordinary non breeder nuclear reactor.

Question No. 10

What is the purpose of biological shield in nuclear plants?


Biological shield of heavy concrete prevents exposure to neutrons, beta rays and gamma rays which kill living things.

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