No abstract

No abstract

A one-equation variant of a previously developed two-equation, renormalization group based, hybrid RANS/LES model is presented. The model consists of a transport equation for the mean dissipation rate and an algebraically prescribed length scale. The length scale is proportional to the wall-distance in RANS regions of the flow and to the filter width in LES regions. A very simple, but efficient, near-wall model is also presented, in the manner of Yakhot and Orszag's RNG modeling. The only free parameter entering the low-Reynolds formulation has been calibrated against channel flow, and the value corresponds well with experimental values for the same parameter obtained for homogeneous isotropic turbulence. The model is then validated for a turbulent impinging jet heat transfer problem. Results are satisfactory and compare very favorably against DES and dynamic LES for the same computation.

No abstract

Domestic coal and waste resources, which are valuable sources of carbon, can support efforts to transform a linear economy into a circular carbon economy. Their use, as an alternative to conventional, imported fossil resources (crude oil, natural gas) for chemical production, provides an opportunity for Poland to solve problems related to competitiveness, security of supply, and sustainable development in various industries. This is important for Poland because it can provide it with a long-term perspective of economic growth and development, taking into account global trends (e.g., the Paris Agreement) and EU legislation. The article presents a concept to support the transformation from linear toward a circular carbon economy under Polish conditions. The carried-out analyses showed that coal, RDF, and plastic waste fuels can be a valuable source of raw material for the development of the chemical industry in Poland. Due to the assumed availability of plastic waste and the loss of carbon in the production process, coal consumption is estimated at 10 million t/yr, both in the medium- and long-term. In case where coal consumption is reduced and an additional source of ‘green hydrogen’ is used, CO2 emissions could be reduced even by 98% by 2050. The presented results show the technical and economic feasibility of the proposed solution and could be the basis for development of the roadmap for transition of the linear to circular economy under Polish condition.