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In order to prevent incidents due to uncontrolled gas leakage and explosion/fires were devastating look at the factors that determine the safety in operation of gas networks made of polyethylene. Sustainability and safety in operation, lines of distribution networks and installations for use in natural gas represents a complex issue with implications for economic, social and environmental. Underground natural gas pipes are subjected to a series of prompts both static and dynamic which could lead to. damage. The complexity of the problems stemming from the diversity of stress factors acting on the related pipelines supply natural gas. In this context, the authors analyse the behaviour of pipelines under the effect of the stresses to which they are subject by using finite element modelling.

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The major energy crisis, predictable for the global economy, requires attentive research & development in order to grow energy performance, heat transfer and energy storage. It is a known fact that in the energy balance, the biggest share is in thermal energy and that justifies the continuous effort in the optimization of fossil fuel saving solutions and intense promotion of renewable energies. Use of the latter in heating and cooling systems as well as “waste heat” from different processes is consistent with the concept of sustainable development and results in reduction of conventional fuel consumption and emissions. Optimizing such a system can be made by replacing the usual storage material with phase changing materials and by using nanofluids as a secondary agent with the beneficial effect on heat transfer. In this paper we have studied a simplified multitubular heat exchanger, buried in the ground, having as a primary working fluid plain water and nanofluid, using Ansys. The nanofluid is composed of particles of A12O3 dispersed in water at a concentration of 1%. The study indicates an increase in convective heat transfer coefficient of nanofluid compared to water.