Carlos Antonio Santos

Integral transforms solution for flow development in wavy wall ducts

Purpose – The purpose of this paper is to provide an analysis of two‐dimensional laminar flow in the entrance region of wavy wall ducts as obtained from the solution of the steady Navier‐Stokes equations for incompressible flow.Design/methodology/approach – The study is undertaken by application of the generalized integral transform technique in the solution of the steady Navier‐Stokes equations for incompressible flow. The streamfunction‐only formulation is adopted, and a general filtering solution that adapts to the irregular contour is proposed to enhance the convergence behavior of the eigenfunction expansion.Findings – A few representative cases are considered more closely in order to report some numerical results illustrating the eigenfunction expansions convergence behavior. The product friction factor‐Reynolds number is also computed and compared against results from discrete methods available in the literature for different Reynolds numbers and amplitudes of the wavy channel.Research limitations/...

Unified Hybrid Theoretical Analysis of Nonlinear Convective Heat Transfer

The Generalized Integral Transform Technique (GITT) is extended and unified to handle a wide class of nonlinear convective heat and mass transfer formulations that involve nonlinearities in every each equation and boundary condition coefficients and source terms. The proposed hybrid numerical-analytical approach is applicable to both steady and transient situations, and the integral transformation process is promoted so as to yield an explicit transformed system, which can be more efficiently handled by the well-known numerical algorithms for initial value problems. An application of laminar forced convection in duct flow with temperature dependent thermophysical properties is considered more closely to illustrate the formal solution.Copyright

Hybrid Solution for Developing Laminar Flow in Wavy-Wall Channels via Integral Transforms

The analysis of two-dimensional laminar flow in the entrance region of arbitrarily shaped ducts is undertaken by application of the Generalized Integral Transform Technique (GITT) in the solution of the steady Navier-Stokes equations for incompressible flow. The streamfunction-only formulation is adopted, and a general filtering solution that adapts to the irregular contour is proposed to enhance the convergence behavior of the eigenfunction expansion. The case of a wavy-wall channel is then considered more closely in order to report some numerical results illustrating the expansions convergence behavior. In addition to reporting results of streamfunction, the product of friction factor-Reynolds number is also calculated and compared against results from discrete methods available in the literature for different Reynolds numbers and amplitudes of the wavy channel.Copyright

Analysis of steady forced convection in thermally developing turbulent duct flows

Presents a novel theoretical approach, based on extension of ideas associated with the generalized integral transform technique, for obtaining accurate analytic solutions for fully developed steady forced convection inside circular ducts with turbulent flow and constant wall surface temperature conditions. Within the temperature field, reports the thermal response of the fluid in terms of hybrid solutions for bulk fluid temperature and Nusselt number distributions along the thermal entrance region of the duct. Further, in assessing the accuracy and validity of the theoretical work, critically examines predicated analytical solutions of thermally developed Nusselt numbers and compares them with results from reliable empirical correlations of the open literature. For the investigated cases, satisfactory agreement prevailed between the theoretically and empirically derived heat transfer parameters, exhibiting a maximum difference of 9.58 per cent for the range of system variables analysed.

Thermodynamic Analysis Of An Energy High Performance Systems

The energy sector worldwide, every day comes with new challenges, whether it find renewable energy source, or when this energy source can degrade the environment and/or when its efficiency does not satisfy its implementation. In this work, an energy recycling system of two and three levels will be covered. In the tests performed, the primary source is an internal combustion engine 100 KVA powered by natural gas and generates electric power by a synchronous generator coupled to the motor shaft. Energy loss by the exhaust gas is reused in a absorption refrigeration system of 5TR. This first system is restructured to reuse the gases rejected by the absorption refrigeration system generator, in order to preheat the fluid oil used in biodiesel plant as a source of drive. The unit of high performance generation can be classified as cogeneration and / or trigeneration, depending on the type of arrangement which was tested and will meet the physical facilities, such as; the Control and Instrumentation Laboratory for Energy and the Environment, to Mechanical Workshop, to the Institute of sustainable energy of the UFPB, and also the building of RECOGAS. In this study, it was evaluated the constituent energy power of each term of the polygeneration system considering the generator engine group as a main driven source and the results shown in a Sankey diagram, allowed to check the whole process since of the beginning of the burning fuel to end of the electricity production.

Flow Control for Absorption Chillers Using the Par H2O / LiBr Driven in Recirculation Pumps of Low Power

This paper proposes an effective method of variation of speed in the recirculation pump and consequently ensure optimum range of flow for absorption chillers when it uses the pair LiBr/H2O. These systems operate at subatmospheric pressures, merely for this reason the use of non-invasive flow measurement methods. The need for low power recirculation systems in such devices makes it impossible to adopt three-phase loads on the driven of the pumps. These implications prevented the achievement of advances in these systems, limiting the success of important contributions in the literature. Due this, it was designed an experimental apparatus reproducing the flow conditions which are submitted to absorption chillers with LiBr and developed a device that could changing the low power load speeds. It was implemented in LabVIEW language, a PID controller action system, which allowed tested to the flow control, initially for water and then to the saline LiBr/H2O.

Dynamic Model of a Membrane Pump Powered by a Scroll Pump in an Absorption Refrigeration Cycle

This paper presents the dynamic modelling of a pumping system used in an absorption refrigeration cycle using water-ammonia as cooling fluid. This system consists in a membrane pump (with a membrane made of PTFE - Polytetrafluoroethylene), powered by a scroll pump, in which two spring-loaded check valves control the flow direction. By having a system of nonlinear differential equations, using numerical methods, it was possible to find solutions and obtain time dependent functions of flow rate (making possible the analysis of the flow pulsation and its behaviors), valves openings, membrane position, in order to better understand the system. In addition, it was possible to generate functions and graphics that shown the relations between changes in variables such as membrane radius and thickness and excitation frequency and amplitude. It was also possible to generate double variable prediction graphics, that could lead to a user-friendly software on future works, which can help on faster and precise design optimization techniques.Copyright

Experimental Theoretical Study based on mathematical correlations used in the determination of volume flows of non-intrusive character for lithium bromide solution

This work has as proposed the development of experimental theoretical study based on mathematical correlations able to estimate volume flows of non-intrusive character as functions of diameter and pressure for lithium bromide solution linked to an ultrasonic meter, type transit time, model UFM 170. The experimental bench that gave support to this work has been developed on the premises of the Federal University of Paraíba-UFPB in lab-IES Sustainable Energy Institute and RECOGÁS, Cooperative Research Network North/Northeast Natural Gas. This study was developed in LabVIEW platform, with the help of EES - software (Engineering Equation Solver). This study aims to describe all the positive and negative aspects experienced in the subject of this work in order to contribute with flow measurement techniques non-intrusive that would be applied in absorption refrigeration systems.