1. Which of the following statements is correct?
a) 1k.Cal=2B.Th.U
b) 1B.Th.U=252Cal
c) 1k.Cal=100Cal
d) 1k.Cal=4C.H.U
Explanation: 1B.Th.U=252Cal is the correct one. 1k.Cal=2B.Th.U is wrong because 1k.Cal=3.968B.Th.U=2.2 C.H.U. So 1k.Cal=4C.H.U is also wrong. Kilo means 1000. So, 1k.Cal=1000Cal.
2. To calculate HCV of the fuel, the products of combustion are cooled down to __________
a) 600F
b) 700F
c) 400F
d) 200F
Explanation: The products of combustion are cooled down to 600F or 150C that is room temperature. The hydrogen gas gets converted into steam.
3. When the coal is completely burnt in air, then the maximum temperature reached is called _________
a) calorific value of coal
b) gross calorific value
c) calorific intensity of coal
d) net calorific value
Explanation: Calorific value of coal is defined as the amount of heat liberated during combustion of fuel completely. Gross calorific value or HCV means the total heat liberated after combustion of fuel and products must be cooled. Net calorific value is the total heat liberated after combustion of fuel and products are allowed to escape. So, the maximum temperature reached is calorific intensity of coal.
4. To calculate the net calorific value, the products are _________
a) cooled
b) allowed to escape
c) heated
d) collected
Explanation: The products in finding NCV are allowed to escape as the hot gases has no chance of condensation. Cooled in HCV.
5. The Bomb calorimeter is used to determine the calorific value of _________
a) solids and liquid fuels
b) solid and gaseous fuels
c) liquid fuels that can be easily vaporized
d) solid fuels only
Explanation: In Bomb calorimeter, we can find the calorific value of both solid and gas fuels. In Boy’s calorimeter we can fin calorific value for gaseous and easily vaporized liquid fuels.
6. The calorific value of LPG is generally _______ than that of coal.
a) higher
b) lower
c) half
d) very lesser
Explanation: Generally, the calorific values of liquid fuels are more than that of solid fuels. They produce more heat than liquid. So, the calorific value of LPG is more than that of coal.
7. If there is more oxygen content in fuel, then the calorific value of the fuel is _________
a) high
b) low
c) moderate
d) very high
Explanation: The oxygen content in fuel will reduce its ability to burn and so that it cannot produce more amount of heat. So, the calorific value will be low.
8. Which of the following fuel gas will have the highest calorific value?
a) Water gas
b) Bio gas
c) Producer gas
d) Natural gas
Explanation: Natural gas produces a high amount of heat when compared to the other three gases. Water gas and producer gas are synthetic fuels and natural gas natural fuel.
9. Calculate the net calorific value of a coal sample having the following composition:
C=80%, H=5%, O=4%, N=3%, S=3.5% and ash=5%.
a) 7251.8cal/g
b) 7780.5cal/g
c) 7621.5cal/g
d) 7830.75cal/g
Explanation: Apply the dulong’s formula that is: HCV = 1/100[8080C + 34500(H-O/8) + 22400S], here the C, S, O, H are the percentages of carbon, sulphur, oxygen and hydrogen. So, substitute all the given values in the formula and calculate so that you will get HCV (or) GCV as 8094.9cal/g and then apply the formula NCV=(GCV-0.09H*587), her 587cal/g is the latent heat of steam then you will get NCV=7830.75cal/g.
10. A coal has the following composition by weight:
C=90%, O=4%, N=1%, S=0.5% and ash=5%.The NCV of the fuel was found to be 8480cal/g. Calculate the percentage of hydrogen and HCV of the fuel.
a) H=4.21%, HCV=8621.80cal/g
b) H=4.521%, HCV=8221.80cal/g
c) H=4.686%, HCV=8727.37cal/g
d) H=4.1%, HCV=8221.37cal/g
Explanation: Apply the dulong’s formula that is: HCV = 1/100[8080C + 34500(H-O/8) + 22400S], here the C, S, O, H are the percentages of carbon, sulphur, oxygen and hydrogen. So, substitute all the given values in the formula and calculate so that you will get HCV. As we don’t know the value of H, you will get HCV = [7110.7+345H]Cal/g. Let it be equation -1 and then we know that NCV = (GCV-0.09H*587), here 587cal/g is the latent heat of steam. NCV is given then you will get GCV = [8480+52.83H] Cal/g and let it be equation-2. So equate both the equations to get the value of H. you will get H=4.686 and substitute in equation-1 to get the value of HCV=8727.37cal/g.