Byts O. Computer-Aided Designing of Thermal Energy Metering Systems based on Differential Pressure Flowmeters

The object of research is the process of computer-aided designing the thermal energy metering systems based on differential pressure flowmeters Research methods. Methods for mathematical modeling were used based on the laws of hydrodynamics, thermodynamics and similarity theory. Developing the equations for evaluating the uncertainty of indicators of physical properties and uncertainty of thermal energy amount was carried out using theory of errors and theory of uncertainties. Elements of optimization theory were used for the flowmeters designing. Methods of linear programming were used to automate the metering systems designing and methods of object-oriented programming were used to develop the interface of a software package and a subsystem for outputting design results. Scientific novelty of the obtained results. The mathematical model of the thermal energy metering system was developed on the basis of a complete mathematical model of differential pressure flowmeters, equations for determining the thermal energy volume and equations for determining the properties of a heat carrier. This model provides the possibility to study the influence of the design characteristics of the flowmeter and the parameters of the heat carrier on the result of thermal energy volume measurement. New equation for calculating the uncertainty of the enthalpy of water (water steam) was developed on the basis of the uncertainty evaluation theory and equations for calculating the enthalpy of water (water steam). The equation of uncertainty of the measured value of thermal energy volume was developed. New equations for calculating the isentropic exponent of superheated steam based on dependences and equations from IAPWS-IF97 (International Association for the Properties of Water and Steam) were developed. These equations in combination with known equations for calculating the density makes it possible to calculate the state parameters of the water steam during measurement of its flow rate by means of the differential pressure method. Based on processing of this equation, a simplified equation and algorithm for calculating the isentropic exponent of superheated steam for pressure from the saturation line to 100 MPa and temperature from 97 °C to 800 °C was developed. The method of designing a thermal energy metering system was improved. The improvement consists in finding the parameters of the flowmeter that provide the minimum uncertainty in the measured value of the flow rate taking into account the pressure losses limit, which makes it possible to reduce pressure losses in thermal energy supply systems. New approaches to computer-aided designing of a thermal energy metering system were proposed. These approaches make it possible to calculate the constructional and metrological characteristics of a thermal energy metering system taking into account the technological and normative constraints. The practical significance of the thesis is that on the basis of reference isentropic exponent values, obtained by new equation, a simplified relation and algorithm for calculating the isentropic exponent was developed for its application in the calculators of thermal energy volume; the algorithms for calculation of thermal energy volume were developed with implementation of the mathematical model of the thermal energy metering system. These algorithms make it possible to calculate the thermal energy volume for different configurations of metering systems; the algorithm for designing the thermal energy metering system was improved, which provides minimal uncertainty of the measured value of the flow rate taking into account the pressure losses limit. Thanks to this algorithm the pressure losses can be reduced and, consequently, the efficiency of a thermal energy supplying system can be increased. "Thermal Energy" CAD software was developed for computer-aided design of thermal energy metering systems. The algorithms that implement a mathematical model of the thermal energy metering system, an equation for calculating the physical properties of the heat carrier, an equation for calculating the uncertainty of the thermal energy volume were applied in this software.