Analysis of internal helically finned tubes for parabolic trough design by CFD tools

This paper has analysed the effect of the utilization of internal finned tubes for the design of parabolic trough collectors with computational fluid dynamics tools. Our numerical approach has been qualified with the computational estimation of reported experimental data regarding phenomena involved in finned tube applications and solar irradiation of parabolic trough collector. The application of finned tubes to the design of parabolic trough collectors must take into account features as the pressure losses, thermal losses and thermo-mechanical stress and thermal fatigue. Our analysis shows an improvement potential in parabolic trough solar plants efficiency by the application of internal finned tubes

The Modelica thermal model generation tool for automated creation of a coupled airflow: Radiation model and wall model in Modelica

This paper presents the Modelica Thermal Model Generation Tool. The aim of this tool is to enable the user to set up a geometrically correct thermal model for complex geometries that allows predicting the impact of heated/heating devices and their location both in terms of airflow pattern and radiation distribution. Using a geometry file exported from CAD software, the tool distributes wall facets, air nodes and computes the long-wave radiant view factor matrix for obstructed and unobstructed surfaces. This information is exported as ready to use Modelica code. The zonal model VEPZO is used to model airflow within a domain (enclosed space). This model allows predicting airflow and air temperature distribution in space on a coarse mesh and thus computes faster than classical CFD computations. Walls are subdivided on the same grid as the zonal model is set upon. For each wall facet, the Modelica Thermal Model Generation Tool computes the view factors to the other facets in the domain. Comparison of simulated results with test data and application of the Modelica Thermal Model Generation Tool for a room with radiant heating and for the cooling of an aircraft cockpit are presented in this paper

Unlocking the power of walnut shells: enhanced methylene blue adsorption revealed through innovative experimental insights and predictive modeling

\ua9 Springer Nature Switzerland AG 2024. This study explores the efficacy of walnut shells as an adsorbent for removing methylene blue (MB) from aqueous solutions. Characterization of walnut shells revealed a high presence of micropores and mesopores, with microporosity being predominant. Fourier-transform infrared (FTIR) analysis confirmed the presence of functional groups conducive to interacting with MB molecules. Various operating parameters were investigated, identifying optimal conditions at 0.1 g of adsorbent mass, achieving over 92% removal efficiency within 10 min for an initial MB concentration of 15 mg/L, at a pH lower than the pHPZC of 5 and at 20 \ub0C. Langmuir isotherm modeling effectively described MB adsorption onto walnut shells, with a maximum capacity of 96.763 mg/g at 20 \ub0C. Kinetic studies supported a pseudo-second-order adsorption mechanism, indicating diffusion control. Thermodynamic analysis revealed that the adsorption of MB onto walnut shells is spontaneous and exothermic. Additionally, Gaussian process regression (GPR) accurately predicted adsorption capacities under varying conditions, providing insights into adsorption behavior and optimization possibilities. Overall, walnut shells offer a promising, cost-effective, and eco-friendly solution for effluent treatment in the textile industry. The combined experimental and modeling approach provides valuable insights for further research in wastewater treatment and environmental remediation

Modelling and multi-objective optimisation of the convective heat transfer characteristics and pressure drop of low concentration TiO2–water nanofluids in the turbulent flow regime

In the research for this paper, a GA–PNN hybrid system was used for modelling the convective heat transfer characteristics and pressure drop of TiO2–water a nanofluid in a fully developed turbulent flow based on an experimentally obtained train and test data set. Models were developed for the Nusselt number and the pressure drop of the nanofluid as a function of Reynolds and Prandtl numbers, nanofluid volume concentration and average nanoparticle diameter. The results of the proposed models were compared with experimental data and with existing correlations. The validity of the proposed models was benchmarked by using statistical criteria and NSGA-II was used for multi-objective optimisation for the convective heat transfer. In the optimisation procedure model, the Nusselt number and pressure drop were considered as the objective functions. However, when the set of decision variables was selected based on the Pareto set, it ensures the best possible combination of objectives. The Pareto front of multi-objective optimisation of the Nusselt number and pressure drop proposed models were also shown and discussed. It was found that application of the multi-objective optimisation method for the turbulent convective heat transfer characteristics and pressure drop of TiO2–water nanofluid could lead to finding the best design points based on the importance of the objective function in the design procedure.The NRF, Stellenbosch University/University of Pretoria Solar Hub, CSIR, EEDSM Hub, RDP and NAC.http://www.elsevier.com/locate/ijhmthb2013ai201