Determination of the calorific value of natural gas using predictive modelling

The analysis of the measured data on the calorific value of natural gas in different regions of Ukraine for 2014–2019, which are in the public domain, has been carried out. Since 2020, such data has not been published. This predetermines the need to use calculation methods for determining this physical quantity for subsequent years in different regions of Ukraine. It is proved that during 2018–2019 there was a trend for the stability of calorific value of natural gas, and fluctuations of calorific value had a smaller amplitude (within the range of 9.31–9.80 kW·h/m3), the spread in the values of the calorific value almost halved: from 0.88 to 0.49 kW·h/m3 compared to 2014–2017. Therefore, the measured data for the calorific value of natural gas for the period 2018–2019 were taken as a basis for predictive modeling of this physical quantity. It has been established that for most regions of Ukraine it is possible to use a single average value of the calorific value of natural gas for the subsequent determination of the energy of this energy carrier. The exceptions are Donetsk, Ivano-Frankovsk, Lugansk and Chernivtsi regions, in which the measurement data of the calorific value of natural gas are described with sufficient accuracy by the trigonometric cosine function. By the method of predictive modeling, a mathematical model has been developed to determine the calorific value of natural gas for a specific month of the year in Ukraine. The adequacy of the developed model has been verified by the example of measuring data on the calorific value of natural gas along route 406 (Ivano-Frankivsk region). It was found that the relative error in calculating the combustion heat of natural gas on this route does not exceed plus 1, minus 3%, which is comparable with the accuracy of measuring the volume of natural gas with household gas meters (the volume of gas and its heat of combustion are parameters for determining the energy of natural gas). Thus, a predictive mathematical model has been developed with sufficient accuracy to describe the change in the calorific value of natural gas and can serve as a basis for calculating this gas parameter in the absence of measurement data.