Analiza problemów pomiarów ciepła z wykorzystaniem hydrodynamicznego przepływomierza z wbudowanym rezystancyjnym czujnikiem temperatury

Autorzy na podstawie analizy typowego układu pomiaru ilości ciepła wykazali, że ma on kilka wad, m.in. nieuwzględnienie możliwej zmiany przepływu masowego z powodu straty technologicznej cieczy lub jej nieuprawnionego odbioru oraz wpływu zmiany charakterystyk cieplnych cieczy ze zmianą temperatury. W udoskonalonym układzie pomiaru ilości ciepła wykorzystuje się dwa przepływomierze (na wejściu i wyjściu), co pozwala uwzględnić stratę masowego przypływu cieczy.

The authors consider typical systems for heat energy measurements (Fig. 1). It is assumed that the liquid mass flow input and output are the same in a typical system. If there are technological losses of heat liquid or its stealing in a heating system, the output amount of liquid is less than the input amount. Then the methodical measurement error of the heat energy (formula (2)) appears. Another component of the measurement error is due to the influence of temperature on the heat capacity of liquid which is different at the input and output of the heating system (formula (3)). To eliminate the above-mentioned methodological errors, the heat energy must be measured at the input and output of the heating system (formula (5)). For this purpose there was proposed an improved system for measuring the amount of heat (Fig. 3). In this system there are used two flow-meters (input and output), which allows taking into account possible losses in the heating liquid. Hence, the relationship between the temperature of the liquid heat capacity (also at the input and output) (Fig. 3) is taken into consideration, too. In order to increase the accuracy of determining the heat by measuring the amount of the liquid movement and its temperature at the same point (which eliminates the appropriate component of the systematic measurement error), the authors developed a hydrodynamic flow-meter with a built-in resistance temperature sensor (Fig. 4). The instrumental component of the error of measuring the heat quantity (which is caused by use of two flow meters instead of one) was examined (formulas (6, 7)).