The present paper proposes a technique for determining duration of heating coiled polyethylene pipes with hot air for laying and installation operations in construction of gas pipelines in conditions of low temperatures.A mathematical model of the thermal process of heating polyethylene pipes with hot air is considered.Herewith,it is assumed that a turbulent flow of heated air courses inside the pipe along its entire length.A laminar sublayer is formed in the pipe wall through which heat is transferred by means of molecular thermal conductivity.The rest of the pipe section is filled with turbulent flowing air(turbulent core).Heat is transferred in a turbulent flow not only by thermal conductivity,but also by turbulent pulsations.The coefficient of turbulent thermal conductivity is determined on the basis of the temperature data of the full-scale experiment at a certain ambient air temperature.The thickness of the laminar sublayer,which is the thermal resistance,is regulated by the known formula.The results of a calculation study of duration of the heating of polyethylene pipe in the temperature range of the ambient air at a known air flow rate fed into the pipe are presented.The effectiveness of the proposed method for determining the duration of heating polyethylene pipes in coils is confirmed experimentally.
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