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Heat Input (heat + input)
Selected AbstractsCONSTRAINING HEAT INPUT BY TRAJECTORY OPTIMIZATION FOR MINIMUM-FUEL HYPERSONIC CRUISEASIAN JOURNAL OF CONTROL, Issue 4 2006M. Wächter ABSTRACT Unsteady heat input effects are considered for the range cruise of a future hypersonic vehicle equipped with a turbo/ram jet engines combination. A realistic mathematical model for describing the unsteady heat effects has been developed. It is coupled to the model for the dynamics of the vehicle. To compute the heat load in hypersonic flight, several points on the vehicle surface are treated simultaneously. A two-step technique consisting of an efficient optimization algorithm and an ordinary differential equations (ODE) solver is applied to generate a solution. The results show that the heat load can be significantly reduced, with only a small increase in fuel consumption. [source] A thermal nonlinear dynamic model for water tube drum boilersINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 1 2010M. A. Habib Abstract A thermal model for the prediction of possible tube overheating was developed. The model incorporates a nonlinear state space dynamic model that captures the important physical interactions of the main variables of steam generation in naturally circulated water tube drum boilers. This paper provides an investigation of the dynamic effects of rapid rise in fuel flow rate (heat input) on the thermal and flow characteristics of the riser tubes in natural circulation water tube boilers. The system under consideration includes the drum, riser and downcomer as its major components. The dynamic response of the system's state variables due to rapid rises in fuel flow rates was investigated. The results show that the sudden rise in the firing rate is followed by an increase in the steam quality, which is accompanied by a decrease in the circulation rate as a result of increase in the pressure. The riser temperature increases slightly above the saturation temperature due to the increase in the steam temperature and due to the dynamic influence resulting from sudden increase in the heat flux. The present calculations of the water level in the drum provide good comparison with those in the literature. Copyright © 2009 John Wiley & Sons, Ltd. [source] The effect of inlet subcooling on two-phase flow instabilities in a horizontal pipe system with augmented surfacesINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 2 2002lmaz Abstract This research has been conducted to investigate the effect of inlet subcooling on two-phase flow instabilities in a horizontal pipe system with augmented surfaces. Five different inlet temperatures are used to study the effect of inlet subcooling for five different heat transfer surface configurations. All experiments are carried out at constant heat input, system pressure and exit restriction. The effect of inlet subcooling on the steady-state characteristics and two-phase flow instabilities are studied for each configuration. The bound aries for the appearance of pressure-drop-type and density-wave-type instabilities are found and the effect of the inlet subcooling on these oscillations is studied for each configuration. Copyright © 2002 John Wiley & Sons, Ltd. [source] EFFECT OF OSMOTIC TREATMENT WITH CONCENTRATED SUGAR AND SALT SOLUTIONS ON KINETICS AND COLOR IN VACUUM CONTACT DRYINGJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 6 2007S.M.A. RAHMAN ABSTRACT An experimental study of osmotic dehydration (OD) of selected heat-sensitive products was carried out in a laboratory-scale vacuum contact dryer. Cubes of potato and apple were examined as model heat-sensitive objects. Experiments were conducted at different conduction heat input levels with wall temperatures in the range 35,45C under vacuum and also in pure vacuum without any external heat input. Detailed investigations were carried out of OD on drying performance, product temperature and color of the dried product. PRACTICAL APPLICATIONS Osmotic treatment of potato and apple samples using concentrated sugar solution shows better osmotic dehydration as well as drying rate in a vacuum contact drying system. This information may help to select the osmotic agent in any industrial application for faster drying rate in vacuum contact drying specially for food products. Moreover this work shows the analysis to find out the starting point of precipitation of osmotic agent inside the products in terms of drying time, temperature and moisture content. This information will be helpful for critical analysis in osmotic dehydration technique which in turns may help for optimum design. [source] Intergranular corrosion on Nd:YAG laser-welded A653 steel for automotive applicationMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 11 2004Y. M. Looi Abstract Laser welding techniques produce a narrower heat-affected zone than other conventional welding methods. However, laser welding is not exempt from high heat input during the welding process. This high heat input results in changes of the material properties including its corrosion behaviour; the formation of the heat affected zone increases the susceptibility of the material to intergranular attack. The residue of zinc at the weld due to condensation and splashing during the welding process may also influence adversely the corrosion behaviour of the material. The degree of susceptibility to corrosion strongly depends on the welding parameters. Electrochemical and microstructure characterisation were employed to study the influence of Nd:YAG (neodymium yttrium aluminium garnet) laser-welding on an A653 galvanized steel at different welding parameters. [source] A phenomenon of waiting time in phase change problems driven by radiative heat transferMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 9 2009A. Fasano Abstract In the paper (J. Food Process Eng. 2008; in press) we emphasized that during a phase change process in which the heat input is driven by a radiation transfer mechanism, a peculiar phenomenon may occur, characterized by a temporary stop of the increase of the boundary temperature due to a sudden change of the heat transfer coefficient upon phase transition. This time interval is needed to allow the thermal properties of the surface to evolve toward a state that is compatible with the heat intake rate corresponding to the new phase. The occurrence of the waiting time is motivated and studied for a general one-dimensional Stefan problem. Then an application is presented to the much complicated problem considered in (J. Food Process Eng. 2008; in press), namely, the model for frying process. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||