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Modeling and validation of a parabolic solar collector with a heat pipe absorber
Ismail, Kamal A.R.,Zanardi, Mauricio A.,Lino, Fatima A.M. Techno-Press 2016 Advances in energy research Vol.4 No.4
Cylindrical parabolic solar concentrators of small concentration ratio are attractive options for working temperatures around $120^{\circ}C$. The heat gained can be utilized in many applications such as air conditioning, space heating, heating water and many others. These collectors can be easily manufactured and do not need to track the sun continuously. Using a heat pipe as a solar absorber makes the system more compact and easy to install. This study is devoted to modeling a system of cylindrical parabolic solar concentrators of small concentration ratio (around 5) fitted with a heat pipe absorber with a porous wick. The heat pipe is surrounded by evacuated glass tube to reduce thermal losses from the heat pipe. The liquid and vapor flow equations, energy equation, the internal and external boundary conditions were taken into consideration. The system of equations was solved and the numerical results were validated against available experimental and numerical results. The validated heat pipe model was inserted in an evacuated transparent glass tube as the absorber of the cylindrical parabolic collector. A calculation procedure was developed for the system, a computer program was developed and tested and numerical simulations were realized for the whole system. An experimental solar collector of small concentration, fitted with evacuated tube heat pipe absorber was constructed and instrumented. Experiments were realized with the concentrator axis along the E-W direction. Results of the instantaneous efficiency and heat gain were compared with numerical simulations realized under the same conditions and reasonably good agreement was found.
Riccardo Donnini,Alberto Fabrizi,Franco Bonollo,Franco Zanardi,Giuliano Angella 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.5
The aim of this investigation was to determine a procedure based on tensile testing to assess the critical range ofaustempering times for having the best ausferrite produced through austempering. The austempered ductile iron(ADI) 1050 was quenched at different times during austempering and the quenched samples were tested in tension. The dislocation-density-related constitutive equation proposed by Estrin for materials having high density ofgeometrical obstacles to dislocation motion, was used to model the flow curves of the tensile tested samples. Onthe basis of strain hardening theory, the equation parameters were related to the microstructure of the quenchedsamples and were used to assess the ADI microstructure evolution during austempering. The microstructure evolutionwas also analysed through conventional optical microscopy, electron back-scattered diffraction techniqueand transmission electron microscopy. The microstructure observations resulted to be consistent with the assessmentbased on tensile testing, so the dislocation-density-related constitutive equation was found to be a powerfultool to characterise the evolution of the solid state transformations of austempering.
Mattioli, Stefano,Curti, Stefania,De Fazio, Rocco,Mt Cooke, Robin,Zanardi, Francesca,Bonfiglioli, Roberta,Farioli, Andrea,Violante, Francesco S. Occupational Safety and Health Research Institute 2012 Safety and health at work Vol.3 No.1
Objectives: Lifting heavy weights involves the Valsalva manoeuvre, which leads to intraocular pressure spikes. We used data from a case-control study to further investigate the hypothesis that occupational lifting is a risk factor for retinal detachment. Methods: The study population included 48 cases (patients operated for retinal detachment) and 84 controls (outpatients attending an eye clinic). The odds ratios (OR) of idiopathic retinal detachment were estimated with a logistic regression model (adjusted for age, sex and body mass index). Three indexes were used to examine exposure to lifting; 1) maximum load lifted, 2) average weekly lifting, 3) lifelong cumulative lifting. Results: For all indexes, the most exposed subjects showed an increased risk of retinal detachment compared with the unexposed (index 1: OR 3.57, 95% confidence interval [CI] 1.21-10.48; index 2: OR 3.24, 95% CI 1.32-7.97; index 3: OR 2.23, 95% CI 1.27-8.74) and dose-response relationships were apparent. Conclusion: These results reinforce the hypothesis that heavy occupational lifting may be a relevant risk factor for retinal detachment.