Mathematical simulation of heat transfer in nonaccessible channels of heat supply system network

High values of standard heat losses in the heating networks of central heat supply systems indicate an opportunity to increase their energy efficiency. Сurrently available mathematical models of heat networks are described in the scientific studies of Polovnikov V.Yu., Kuznetsov G.V., Tarasevich E.I. But they do not solve the problem of assessing changes of the thermal networks state when energy-saving measures are used. The purpose of the study is to determine the permissible heat perception of the device collector for utilization of heat losses in the heating main channel. The study is based on the development and research of mathematical models of heat exchange processes in the heat supply network. A mathematical modeling method is chosen to search for acceptable operating modes of this device. The method can help to determine properly changes in the operation of the heat network. A descriptive mathematical model with distributed parameters based on differential equations with partial derivatives is used in modeling heat transfer processes in the heat network. The model is implemented using the finite element method. The authors propose a device for the utilization of heat losses in the heating channel. The authors have developed mathematical models of heat transfer processes in heat networks of underground trench laying in nonaccessible channels in a traditional design with the use of a heat-reflecting screen and combined action of the network and the device for the utilization of heat losses in the heat channel. Based on the comparison of the calculation results, the permissible heat perception value of the device collector for the utilization of heat losses has been determined. It equals to 90 % of the initial thermal losses. Mathematical models have been verified by comparing the results obtained and the experimental data with an error of less than 6 %. The developed mathematical models allow us to study the influence of heat perception of the device collector and the heat-reflecting screen on the operating mode of the heat network. It can be used to determine the geometric parameters of the collector of the device.