1070-4272/01/7409-1529$25.00C2001 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 74, No. 9, 2001, pp. 1529!1533. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 9,
2001, pp. 1485!1488.
Original Russian Text Copyright + 2001 by Aleksandrov, Varganov.
PROCESSES AND EQUIPMENT
OF CHEMICAL INDUSTRY
Absolute Measurements of the Combustion Heat of Natural Gas
Yu. I. Aleksandrov and V. P. Varganov
Mendeleev Russian Research Institute of Metrology, State Unitary Enterprise, St. Petersburg, Russia
Received April 28, 2000; in final form, July 2001
Abstract-A new isothermal calorimetric method for measuring the combustion heat of gas, relying upon the
operation principle of the heat pipe, is considered together with the sequence of thermal processes occurring
when this method is used. The functional diagram of the calorimeter is analyzed. Two procedures for meas-
uring the heat effects are presented.
The increasing cost of natural gas has always
resulted, and does so now, in that the requirements to
the accuracy of measurement of its calorific value tend
to become increasingly stringent.
At present, only
four studies concerned with precision measurement of
the combustion heat of methane are known .
Three of these  served as a basis for recommen-
dations concerning calculations of the combustion
heat of natural gas with an error of 0.12%  from
results of gas-chromatographic analysis of natural gas
Lowering the error in determining the combustion
heat of methane requires that a set of investigations
should be carried out, comprising three independent
stages: (i) developing a method for absolute measure-
ments of the combustion heat of fuels,
a gas calorimeter to be used in this method, and
(iii) developing a procedure for measuring the com-
bustion heat of natural gas.
Despite significant differences in design, all the
known types of calorimeters possess a common fea-
ture: necessity for calibration, either electrically or
with the use of appropriate pure gases and gas mix-
tures. This procedure makes an additional contribution
to the total error of determining the combustion heat.
In the US, the combustion energy of natural gas is to be estab-
lished in conformity with the [Gas Act] adopted by the
Congress of the United States in 1978 with an error of no
more than 0.1% .
As far back as 1968, specialists pointed to the necessity for
performing new investigations in order to reduce the error in
question , which is only possible with fundamentally new
method and equipment.
To absolute measurement techniques are referred methods
in which the property being measured is related to basic units
by a known theoretical dependence .
Therefore, developing a combustion heat measure-
ment technique requiring no calorimeter calibration
will favor, all other conditions being the same, higher
The following requirements to the method of com-
bustion heat measurement and the gas calorimeter to
be used in the process were formulated: the combus-
tion heat is to be measured in strict conformity with
the regulations, with an error of no more than 0.1%,
and absolute measurements (i.e., those without any
kind of calibration) are to be done at combustion heats
of gaseous fuels in the range 20350 MJ m
measurement technique operating in the isothermal
mode was chosen. As shown by Weber , it is pre-
ferable to perform in this case direct measurements by
the compensation method. Such measurements can be,
under certain conditions, rather accurate and well re-
producible, especially when the Peltier effect is
employed to compensate heat released in exothermic
The main difficulty encountered in developing an
isothermal gas calorimeter is the nonuniform distribu-
tion of temperature in the combustion chamber. This
problem has been solved by fast and loss-free conver-
sion of the combustion heat into the phase transition
heat compensated by means of the Peltier effect .
For this purpose, the calorimeter design is based
on the principle of operation of the heat pipe charac-
terized, on the one hand, by high heat conductivity
and, on the other, by the possibility of collecting heat
scattered over a large area and concentrating it in a
rather limited prescribed surface [11, 12].
Three zones can be distinguished in the heat pipe:
those of evaporation and condensation, and the inter-