IKA C 7000 Operating Instructions Manual page 23

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The gross calorific value Ho is obtained by dividing the heat energy released by
YDOXH +R
burning a solid or liquid fuel by the weight of the sample. When determining the heat
energy released, water-containing components of the fuel must be present in liquid
form after combustion.
1HW FDORULILF
The net calorific value Hu is the gross calorific value less the condensation energy
YDOXH +X
of water contained in the sample and formed by combustion. The net calorific value
is of great technical importance, because in all major applications, only the net calo-
rific value can be exploited as energy.
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The reproducibility of the results depends to a great degree on the energy input
(temperature increase) being similar to the energy input during calibration. In the
same way, the oxygen pressure should be the same for measurement and calibra-
tion. Under optimum settings and conditions, the C 7000 calorimeter can achieve a
measurement reproducibility of ± 0.2 percent to DIN 51900. This accuracy is guar-
anteed under the following conditions (they apply to both calibration and measure-
ment):
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Calibration substance
Sample mass
Ambient temperature
Temperature of decomposition vessel
before determination
Oxygen pressure
Measurement period max. (pre- and
main test)
The C 7000 calorimeter is designed for an energy input of up to 30 000 J, and oper-
ates reliably in ambient temperatures between 18 ° C and 30 ° C. For good meas-
urement results, temperature variations must be avoided.
The achievable reproducibility can be estimated with the aid of the curves below. It
is very dependent on the amount of energy released in the decomposition vessel,
and on the duration selected for the pre-test. Apart from those factors, the results
are affected by qualitative parameters such as the homogeneity and combustibility
of the sample.
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9DOXH
Benzoic acid
1 g ± 0.05 g
25° C ± 1 K
25 ° C ± 1 K
30 bar
7.2 min.
®
IKA -WERKE C 7000 Ver. 07 09.07