Engineering Chemistry S Datta

382 ENGINEERING CHEMISTRY
Sol. HCV = net calorific value + (0.09 H + 587) kcal/kg
= (8490.5 + 0.09 H + 587) kcal/kg [Q H = % of hydrogen]
= (8490.5 + 52.8 H) kcal/kg.
L
NM
1
HCV =
100 8080 90 34500 3I × + H − 2240 0 5
HG
8 K J + × . kcal/kg.
= 7754.8 + 345 H = kcal/kg.
= 7754.8 + 345 H = 8490.5 + 52.8 H.
∴ 7754.8 + 345 H = 8490.5 + 52.8 H.
or 292.2 H = 1335%
∴ H = 4.575%
∴
HCV = (8490.5 + 52.8 × 4.575) = 8731.8 kcal/kg.
Example 2. On burning 0.83 g of a solid fuel in a bomb calorimeter, the temperature of
3500 g of water was increased from 26.5°C to 29.2°C; water equivalent of calorimeter and latent
heat of steam are 385 and 587 cal/g, respectively. If the fuel contains 0.7% H, calculate HCV
and NCV.
(W + w)( t2 − t1)
(385 + 3500) (29.2 − 26.3)
Sol. HCV = =
m
0.83
= 12,638 cal/g.
NCV = (HCV – 0.9 H × L) cal/g
= (12,638 – 0.9 × 0.7 × 587) cal/g
= 12,601 cal/g.
Boy’s Gas Calorimeter. It is used for measuring the calorific value of gaseous and
liquid fuels (Fig. 18.2).
In the apparatus (Fig. 18.2) known volume of gas is burnt at a uniform rate by a burner.
Around the burner there is a chimney containing coils wherein water at a constant rate is
passed. Separate thermometers measure the incoming and outgoing water temperatures
(t 1
and t 2
) .
F
O
QP
Exhaust
gases
Rubber
tubing
Inner
Cu coil
Water
inlet
Insulated
container
Outer
Cu coil
Air
Condensed
steam
Air
Meter
Gaseous
or liquid
fuel
Fig. 18.2 Boy’s gas calorimeter.