APPLICATION OF MODERN PRE-INSULATED PIPES TO INCREASE THE ENERGY EFFICIENCY OF CENTRALIZED HEAT SUPPLY SYSTEMS

The article is devoted to a review of manufacturing technologies and methods for counteracting the effects of aging and destruction of a ball of thermal insulation in previously insulated pipes (PIP) of heating networks. The thermophysical characteristics of various blowing agents are compared; the superiority of cyclopentane in both thermophysical and environmental parameters is shown. The basic technologies for the production of pre-insulated pipe wires are considered. The advantages of «conti» technology using a diffusion barrier are highlighted. It is shown that for polyurethane foam, the main factor that suppresses heat transfer through PUR type thermal insulation is the low thermal conductivity of the gas mixture, which is "sealed" in the foam cells. The analysis of the influence of “aging” of the heat-insulating shell, namely, the diffusion of oxygen molecules into the structure of polyurethane foam, is carried out, and its negative effect on the thermal characteristics of the heat-insulating material is shown. Oxygen diffusion leads to a gradual increase in the value of the coefficient of thermal conductivity of the heat-insulating shell, and as a result, increases heat loss by the pipeline. The results of predictive calculations confirmed the effectiveness of the use of diffusion barriers in the manufacture of PIP. It is shown that when using PIP with a diffusion barrier, unproductive heat energy losses decrease on average by 20–21%, which, in turn, leads to a decrease in the amount of payments to end consumers and an increase in the quality and efficiency of district heating systems. It is also noted that polymer pre-insulated pipelines are practically not inferior in strength and reliability to steel PIP and at the same time, they have several advantages over steel PIP. It is recommended to increase the use of polymer PIP in the reconstruction of heating networks of the district heating system.