RESEARCHES OF A THERMAL AND MECHANICAL CONDITION OF COOLED POLYMERIC PIPES

• Main Authors: Інна Олександрівна КРУТАСЬ, Ігор Олегович МІКУЛЬОНОК, Аркадій Дем’янович ПЄТУХОВ, Олександр Леонідович СОКОЛЬСЬКИЙ
• Format: Article
• Language: English
• Published: Igor Sikorsky Kyiv Polytechnic Institute 2013-10-01
• Series: Вісник Національного технічного університету України «Київський політехнічний інститут імені Ігоря Сікорського»: Серія «Хімічна інженерія, екологія та ресурсозбереження»
• Subjects: полімерна труба; охолодження; термомеханічний стан; ефективність.
• Online Access: http://chemengine.kpi.ua/article/view/55778

It is known, what even at the same process of processing of polymer the packaging density of its macromolecules can change depending on parameters of processing, in particular from speed of a melt cooling. Thus depending on parameters of technological process, in particular from temperature of processing and speed of cooling operational properties of a product can change essentially. Especially it is characteristic for crystal or partially crystal polymer, in particular for polyethylene, during its melt cooling when the polymer temperature changes in a wide range: from temperature above temperature of melting (hardening) to temperature surrounding environments. In this article results of numerical modeling of temperature fields and fields of pressure in a wall of polymeric pipes of two standard sizes (D=90 mm, SDR 6 and D=63 mm, SDR 9) are considered under different refrigerating conditions. Cooling processes at unilateral external cooling of a pipe by water, bilateral external and internal cooling of a pipe by water, and also the bilateral combined cooling (outside by water, inside by air) are investigated. It is shown that bilateral cooling of pipes (especially by water as a coolant), not only intensifies cooling process, but also can lead to occurrence in walls of pipes of considerable mechanical stresses which will negatively influence quality of received pipes. Thus, if during cooling a formed polymeric product residual stresses exceed admissible stress, in polymer arise an external and internal defect (macro and micro cracks, bowls, leakages, etc.) that worsens indicators of quality of a received product. The least stress arise under condition of unilateral cooling which at the same time provides considerable duration of process of cooling, and, hence, and considerable floor spaces under cooling baths. Therefore the most effective from the point of view «intensity of cooling and residual pressure» is the bilateral combined cooling (water and air cooling). It is necessary to notice that the resulted researches concern a case when polymer before the cooling beginning already has cooled down more low from the hardening temperature. In a case when cooling of the formed product occurs from temperature which exceeds the hardening temperature of polymer, it is necessary to consider processes, characteristic for a mode of polymer hardening.