Oronzio Manca

Università della Campania Luigi Vanvitelli, Ingegneria Industriale e dell'Informazione, Faculty Member

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Papers by Oronzio Manca

One-Dimensional Approximate Analytical Solutions of Heat Conduction in Semi-Infinite Solids with Temperature-Dependent Properties

by Gaetano Barbaro and Oronzio Manca

Hybrid Methods in Engineering, 2001

Demonstration dual source solar assisted heat pump system: experimental results

Numerical Investigation of Thermal and Fluid Dynamic Behavior of Solar Chimney Building Systems

In this paper a numerical investigation on a prototypal solar chimney system integrated in a sout... more In this paper a numerical investigation on a prototypal solar chimney system integrated in a south facade of a building is presented. The analysis is carried out on a three-dimensional model in air flow and the governing equations are given in terms of k-ε turbulence model. Two geometrical configurations are investigated: 1) a channel with principal walls one vertical and the other inclined and 2) a channel with vertical parallel walls. The chimney is 4.0 m high, 1.5 m wide whereas the thickness is 0,20 m for the vertical parallel walls configuration and at the inlet 0,34 m and at the outlet 0,20 m for the inclined ones. The problem is solved by means of the commercial code Ansys-Fluent and the results are performed for an uniform wall heat flux on the vertical wall equal to 300 and 600 W.m -2 . Results are given in terms of wall temperature distributions, air velocity and temperature fields and transversal profiles in order to evaluate the differences between the two base configurations and thermal and fluid dynamic behaviors. Further, the ground effect on thermal performances is examined and discussed.

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Natural Convection in Open Channels in Computational Analysis of Convection Heat Transfer

Laminar confined impinging slot jets with nanofluids on heated surfaces

2011 17th International Workshop on Thermal Investigations of Ics and Systems, Sep 1, 2011

Abstract In this paper a numerical investigation is carried out on confined impinging slot-jets w... more Abstract In this paper a numerical investigation is carried out on confined impinging slot-jets with nanofluids on a horizontal heated surface at uniform temperature. The cooling fluid is a nanofluid water/Al 2 O 3 and it is assumed with constant thermo-physical proprieties. The single-phase model is employed and the flow regime is laminar. Different values of the channel height and diameter of nanoparticles are investigated. Results show the increase of Nusselt number together with pumping power.

Linear Regression Models to Forecast Electricity Consumption in Italy

Energy Sources Part B Economics Planning and Policy, Oct 1, 2012

Abstract The influence of economic and demographic variables on the annual electricity consumptio... more Abstract The influence of economic and demographic variables on the annual electricity consumption in Italy has been investigated in order to develop a simple and data light electricity consumption forecasting model, to be used as part of more complex planning tools. The time period considered for the historical data is from 1970–2007. Multiple and single regression models are developed using historical electricity consumption, gross domestic product (GDP), GDP per capita, and population. Annual electricity consumption ...

Numerical Investigation of the Natural Convection Flows for Low-Prandtl Fluids in Vertical Parallel-Plates Channels

Journal of Applied Mechanics, 2006

ABSTRACT In open cavity receivers employed in solar paraboloidal dish applications, natural conve... more ABSTRACT In open cavity receivers employed in solar paraboloidal dish applications, natural convection occurs and contributes a significant fraction of energy loss. Its characteristics hence need to be clarified so that it can be effectively minimized in order to improve the system efficiency. The investigation of natural convection loss from cavity receivers was undertaken numerically and was validated using the published experimental results for four different receiver geometries. A good agreement between experimental and numerical results was obtained. Furthermore, the numerical results of all receivers were qualitatively comparable to the predictions by other available correlations hitherto, although it was found that each correlation has a limited range of applicability arising from the particular cavity geometry and experimental conditions used to derive it. To address this shortcoming, a new correlation based on the numerical results for three of the above four receivers has been proposed. The correlation employs a new concept of an ensemble cavity length scale, to take into account the combined effects of cavity geometry and inclination. Despite a wide variety of cavity geometries and operating conditions, the proposed correlation predicts approximately 50% of the data within +/- 20% and 90% of the data within +50%. This is better than any of the other correlations published to date. The new correlation is also simpler to use than the most accurate of those previously published. [DOI: 10.1115/1.4003582]

Experimental Investigation of Natural Convection in an Asymmetrically Heated Vertical Channel with an Asymmetric Chimney

Journal of Heat Transfer, Aug 1, 2005

Composite Correlations for Air Natural Convection in Tilted Channels

Design and thermal control of tilted channels in air natural convection requires knowledge of rel... more Design and thermal control of tilted channels in air natural convection requires knowledge of relations between process parameters. Composite correlations of average Nusselt number in terms of channel Rayleigh number (10 Ra 9.0 104) are proposed for inclined channels with uniform symmetric or asymmetric heat flux. The thermal radiative effects are taken into account in modified Nusselt and Rayleigh numbers. The surface emissivities considered are 0.05 and 0.8. Experimental data employed to obtain the proposed correlations are in good ...

Numerical Study of Air Forced Convection in a Rectangular Channel Provided With Ribs

2010 14th International Heat Transfer Conference, Volume 2, 2010

Heat transfer enhancement technology has the aim to develop more efficient systems as demanded in... more Heat transfer enhancement technology has the aim to develop more efficient systems as demanded in many applications, like heat exchangers for refrigeration, automotives, process industry, solar heater etc.. Convective heat transfer may be enhanced passively by adopting different solutions. A possibility for increasing the heat transfer is to employ rough surfaces. When a fluid flows in a channel, ribs break the laminar sub-layer and create local turbulence, due to flow separation and reattachment between consecutive ribs, which ...

Experiments on natural convection and radiation in asymmetrically heated vertical channels with discrete heat sources

Thermal and fluid dynamic analysis of solar chimney building systems

International Journal of Heat and Technology, Dec 1, 2013

Numerical simulation of free convection heat transfer from localized discrete heat sources in vertical channel

This paper addresses the problem of natural convection cooled channels heated with flush-mounted ... more

Approximate Analytic Estimate of Axial Fluid Conduction in Laminar Forced Convection Tube Flows with Zero-to-Uniform Step Wall Heat Fluxes

Http Dx Doi Org 10 1080 01457630304027, Nov 30, 2010

The influence of axial fluid conduction on low Péclet number flows in the thermal entrance region... more The influence of axial fluid conduction on low Péclet number flows in the thermal entrance region of long circular tubes is investigated in this theoretical study. The convective heat transport of viscous fluids relates to a specific condition under which the first part of the tube ( x h 0) is insulated and the second part of the tube ( x > 0) receives a heat flux of uniform intensity. A conjugate one-dimensional lumped model produces a solution of compressed algebraic form that is able to deliver dependable mean bulk temperatures that are in perfect agreement with those obtained numerically by the formal conjugate two-dimensional distributed model. As a by-product of the succession of algebraic calculations within the platform of the lumped model, the critical Péclet number Pe cr has been easily quantified. This number is a figure-of-merit of remarkable importance in the modeling of forced heat convection in tubes because it establishes the threshold between two contrasting situations: one embracing axial fluid conduction (finite Pe) and the other implicating negligible axial fluid conduction (Pe M X ). In addition, the local wall temperatures were calculated with an approximate engineering procedure, showing good agreement with those determined numerically by the formal conjugate two-dimensional distributed model.

Numerical Analysis on the Effects of Transversal Ribs on Forced Convection in Channels

Volume 2: Theory and Fundamental Research; Aerospace Heat Transfer; Gas Turbine Heat Transfer; Computational Heat Transfer, 2009

Heat transfer in fluids is very important in many industrial heating and cooling equipments. Conv... more Heat transfer in fluids is very important in many industrial heating and cooling equipments. Convective heat transfer can be enhanced passively by changing flow geometry, boundary conditions or by increasing thermal conductivity of the fluid. Another possibility for increasing heat transfer with gas is to employ extended surfaces. When a fluid flows in a channel, transversal ribs can be used as fins and break the laminar sublayer creating local wall turbulence. However, as a consequence the presence of the ribs can significantly ...

Combined thermal and optical analysis of laser back-scribing for amorphous-silicon photovoltaic cells processing

International Journal of Heat and Mass Transfer, Feb 1, 1999

The numerical and experimental analysis of laser back!scribing fabrication of a!Si photovoltaic c... more The numerical and experimental analysis of laser back!scribing fabrication of a!Si photovoltaic cells\ made out of a multilayer thin _lm on a glass substrate\ is carried out[ The numerical study is performed by means of a rather simple combined optical and thermal model[ Experiments are carried out throughout the three phases of the manufacturing process[ The successive targets of the selective cut are a transparent conductive oxide thin _lm "TCO#\ a TCO:a!Si double layer and a TCO:a!Si:Al multilayer[ Experimental results and predictions from the numerical model are compared in terms of the cut energy~ux values[ In the numerical study the cut energy~ux is assumed to be the one which determines the melting of the material[ The predicted cut energy~uxes are in good agreement with experimental results[ Þ 0887 Elsevier Science Ltd[ All rights reserved[ Key words] Thermal and optical analysis^Multilayer thin _lm^Laser back!scribing^Amorphous silicon^Photovoltaic module fabrication

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Heat Transfer Enhancement with Nanofluids

A critical synthesis of the variants within the thermophysical properties of nanofluids is presen... more A critical synthesis of the variants within the thermophysical properties of nanofluids is presented in this work. The experimental results for the effective thermal conductivity and viscosity reported by several authors are in disagreement. Theoretical and experimental studies are essential to clarify the discrepancies in the results and in proper understanding of heat transfer enhancement characteristics of nanofluids. At room temperature, it is illustrated that the results of the effective thermal conductivity and viscosity of nanofluids can be estimated using the classical equations at low volume fractions. However, the classical models fail to estimate the effective thermal conductivity and viscosity of nanofluids at various temperatures. This study shows that it is not clear which analytical model should be used to describe the thermal conductivity of nanofluids. Additional theoretical and experimental research studies are required to clarify the mechanisms responsible for heat transfer enhancement in nanofluids. Correlations for effective thermal conductivity and viscosity are synthesized and developed in this study in terms of pertinent physical parameters based on the reported experimental data.

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Parametric Analysis for Thermal and Fluid Dynamic Management of Natural Convection in a Channel-Chimney System

by Assunta Andreozzi and Oronzio Manca

Volume 4: Fatigue and Fracture, Heat Transfer, Internal Combustion Engines, Manufacturing, and Technology and Society, 2006

ABSTRACT In this paper a parametric analysis of natural convection in air in a channel-chimney sy... more ABSTRACT In this paper a parametric analysis of natural convection in air in a channel-chimney system symmetrically heated at uniform heat flux, obtained by means of a numerical simulation, is carried out. The analysed regime is two-dimensional, laminar and steady-state. The numerical procedure employs the full Navier-Stokes and energy equations in terms of the stream function-vorticity approach. Results are presented in terms of wall temperature profiles in order to show the more thermally convenient configurations which correspond to the channel-chimney system with the lowest maximum wall temperature. The analysis is obtained for a Rayleigh number in the range between 102 and 105 , for a channel aspect ratio equal to 5, 10 and 20 and the extension and expansion ratios between 1.0 and 4.0. Correlations for dimensionless mass flow rate, maximum wall temperature and average Nusselt number in terms of Rayleigh number, aspect ratio, extension and expansion ratios are presented. Geometric optimal configurations, for assigned Rayleigh number and aspect ratio, are estimated as a function of the extension ratio. For considered Rayleigh number the difference between the highest and the lowest maximum wall temperatures increases increasing the channel aspect ratio. This behaviour is as greater as the extension ratio is. These differences decrease significantly for the highest Rayleigh number value. The optimal expansion ratio values depend strongly on Rayleigh number and extension ratio values and slightly on the aspect ratio.

A numerical study of natural convection between symmetrically heated vertical parallel plates

Thermocirculation heat transfer in a solar chimney

This paper is a report on an experimental investigation on a solar chimney that follows previous ... more This paper is a report on an experimental investigation on a solar chimney that follows previous studies of the same authors. The system herein tested is a simple natural circulation solar air loop without storage. System measured performances are shown including most significant system parameters and climatic variables. First results of a flow visualization study evidence turbulent flow characters. Empirical