1,721,018 research outputs found
Experimental, theoretical, and numerical modal analysis of a damped portable-grinder disk
No full textAn experimental investigation was conducted to determine the elasto-dynamic properties of a new type of damped disk and to evaluate its behavior in terms of noise reduction. The new disk was introduced to control the vibration and noise of portable grinder disks, which are used in a variety of metal manufacturing processes. A reduction in the high-frequency modes of the damped disk was found which was not evident in the undamped disk
Oenological properties of Saccharomyces bayanus and S. cerevisiae intraspecies hybrids
No full textEnological properties of Saccharomyces bayanus and S. cerevisiae intraspecies hybrid
Space Heating Load Estimation Procedure for CHP Systems sizing
No full textDue to its environmental and energy benefits, the Combined Heat and Power (CHP) represents certainly an important measure to improve energy efficiency of buildings. Since the energy performance of the CHP systems strongly depends on the fraction of the useful cogenerated heat (i.e. the cogenerated heat that is actually used to meet building thermal demand), in building applications of CHP, it is necessary to know the space heating and cooling loads profile to optimise the system efficiency. When the heating load profile is unknown or difficult to calculate with a sufficient accuracy, as may occur for existing buildings, it can be estimated from the cumulated energy uses by adopting the loads estimation procedure (h-LEP). With the aim to evaluate the useful fraction of the cogenerated heat for different operating conditions in terms of buildings characteristics, weather data and system capacity, the h-LEP is here implemented with a single climate variable: the hourly average dry- bulb temperature. The proposed procedure have been validated resorting to the TRNSYS simulation tool. The results, obtained by considering a building for hospital use, reveal that the useful fraction of the cogenerated heat can be estimated with an average accuracy of ± 3%, within the range of operative conditions considered in the present study
Cross-helix corrugation: The optimal geometry for effective food thermal processing
No full textIn the present paper, an innovative and effective heat transfer enhancement technique for food processing, cross-helix profile wall corrugation, is proposed and tested. In the food industry, the two most promising corrugation profiles are the transversal and single-helix ones because they both satisfy hygienic design principles. Among the available wall corrugation techniques, transversal corrugation allows for the highest heat transfer performance, and the spirally corrugated tubes guarantee the easiest manufacturing. For this reason, single-helix corrugated tubes are the most commonly employed in heat exchangers for food processing. The cross-helix profile presented in this work represents an intermediate solution between transversal and single-helix corrugation aimed at combining their positive aspects. One of the main goals of the current research is to identify an optimal geometry that maximises the heat transfer performance by limiting the pressure drop augmentation for this specific engineering application (i.e., food thermal processing). For this purpose, the effect of the geometrical parameters of the corrugation profile is investigated by varying two of the most influent quantities in terms of heat transfer performance and pressure drop: corrugation depth and corrugation pitch. Six pipes characterised by different cross-helix corrugations are tested. Their performance is evaluated by studying the forced convective heat transfer in the Reynolds and Prandtl numbers ranges (50–14,000 and 5–150, respectively), using ethylene glycol, water and a mixture of the two as the working fluids. The outcomes show that corrugation depth plays a crucial role in enhancing the heat transfer performance of the tested pipes. An optimal geometry is established, and correlations to describe its thermal and fluid flow behaviours are proposed. This optimal geometry shows superior performance to that of the most widely adopted types of corrugation. For the low/intermediate Reynolds number range (i.e., 200–2000), the efficiency of the proposed cross-helix profile is up to three times greater than that of the single helix and is also greater than that of transversally corrugated tubes. These outcomes make cross-helix a recommended option to be used in the design of optimised heat exchangers. Because the studied geometry is expressly developed for food industry application, a set of measurements is also performed in which apricot juice is adopted as the working fluid. The findings confirm the efficiency of the proposed correlations with non-Newtonian fluid foods and enable them to be extended to a wide range of real food industrial applications
Experimental, Theoretical, and Numerical Modal Analysis of a Damped Portable--Grinder Disk
No full textInverse heat transfer modeling applied to the estimation of the apparent thermal conductivity of an intumescent fire retardant paint
Full text linkIntumescent paints are widely used as passive fire protective materials in the building sector, primarily with regard to steel framed structures. The fire resistance of commercial intumescent coatings is typically tested experimentally using expensive and time consuming large-scale tests; conversely, the increasingly common performance-based fire safety engineering approach requires the development of techniques to generalize and predict the behavior of these protective materials. Recently, an experimental and data processing technique based on temperature measurements of the growing char layer and on the formulation of the inverse heat conduction problem within the system, has been proposed. This investigation indicated that an accurate and complete modeling approach is required to make robust predictions in the processing of the experimental data. In this paper, an enhanced procedure for estimating the apparent thermal conductivity of the intumescent paint is proposed and validated. The analysis presented in this study, performed with a physical and chemical characterization of the intumescent paint, allows estimation of the apparent thermal conductivity of the char layer with good approximation, thereby providing important information for assessing the fire protective capability of the coating under the fire safety engineering approach
Direct numerical simulation applied to the analysis of the convective heat transfer enhancement in an arc-shaped wall corrugated tube
No full textThe direct numerical simulation (DNS) approach is adopted here to study the forced convection problem in an arcshaped wall corrugated tube. This kind of geometry is representative of a widely used passive heat transfer enhancement technique (i.e., wall corrugation) mainly adopted for improving the efficiency of heat transfer equipment. The augmentation mechanism is mainly due to the onset of instabilities in the flow that lead to an early departure from the laminar flow regime. The present work deals with the numerical description of the influence of the flow instabilities on the heat transfer mechanism. The numerical simulations point out that in the unsteady flow regime, due to the formation and disruption of the vortices, the flow loses the symmetry property about the tube axis by developing a time-dependent velocity component in all the directions. This effect, registered for Re > 54, encourages a fluid mixing that greatly enhances the heat transfer mechanism. The augmentation effect is discussed also by adopting the field synergy principle approach, which confirms that in the stable regime the convective contribution to the heat transfer mechanism is almost ineffective in a wide region of the domain while the instability reduces the extent of the domain that does not positively contribute to the convective heat transfer
Analysis of convective heat transfer in non-Newtonian fluids by applying the field synergy principle approach
No full textThe present paper is intended to evaluate the local convective heat transfer of power-law fluids through a circular channel, accounting for the asymmetric heating that may occur in some practical applications. The temperature distribution within the fluid is analytically determined by assuming that the wall of the channel could be partially heated by a constant heat flux. The effects of asymmetric heating and the flow behavior index on the average performance of the heat transfer device are evaluated in terms of average Nusselt number, while the local phenomena are investigated by adopting the field sinergy principle approach. The results in terms of average Nusselt number highlight that the convective heat transfer coefficient decreases as the portion of the heated wall increases, while it increases as the flow behavior index decreases. This trend is motivated by analyzing the heat transfer phenomenon by means of the field sinergy principle approach; indeed, this analysis reveals that synergy between the velocity vector and the temperature gradient is better when the wall is heated only for a small portion and for shear thinning fluid
Model Development of a Thermosyphon Heat Pipe for the Temperature Management in a Wine Fermenter Tank
No full textThe oenological traits of thermotollerant Saccharomvces strain
No full textThe oenological traits of thermotollerant Saccharomvces strai
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