Description: 1 online resource xiii, 205 pages : illustrations some color. The analysis parameters typical of a Constructal description such as conductance or Overall Performance Coefficient show that significantly improved performances may be achieved when using water, even if an unavoidable increase in pressure losses affects the liquid-refrigerated case. Unlike in counterflows formed by two parallel streams, in which the longitudinal temperature gradient is constant, in the counterflow formed by two trees the longitudinal temperature gradient is steeper as one approaches the periphery of the tree canopy. The book contains research results obtained by applying Bejan's Constructal Theory to the study and therefore the optimization of fins, focusing on T-shaped and Y-shaped ones. Therefore, some conclusions necessary to undertake an adequate adjustment of thermal stress deformation have also been formulated, and online monitoring of the clearance of radial seals is proposed. This validation allowed to apply the method to new configurations, so to develop systems further on optimised, able to remove higher thermal fluxes in the same processes. The future use of dendritic heat exchangers in devices with maximal heat transport density is proposed.
The sum of the two penalties is minimum when the component size is finite, at the intersection between the two penalties. The effective signal processing and information extraction are the key to state monitoring and fault diagnosis of the hydraulic turbine unit. The results indicated that, the tree-shaped network configured with length dimension of two is able to maximum flow access; the path length plays a significant role in the determination of flow boiling in tree-shaped minichannel networks. In this category, the paper includes such topics as: heat transfer augmentation techniques, heat exchanger design, and thermal insulation systems. The emergence and development of constructal theory, which has been a new discipline branch to research sorts of structures in nature and engineering, are reviewed. The system-based optimization has more advantages over the component-based optimization in the coordination and cooperation of main heat exchanger with other parts in a whole system.
And in tree-shaped flow structures, the local pressure loss due to confluence flow is found to be larger than that due to diffluence flow. On the hot side, fluid is pumped from the center to the periphery. Emphasis is placed on the development of simple strategies for decreasing the computational cost required by the development of such structures. The system-based optimization which takes the net work output as the objective function, sometimes weakens the performance of heat exchanger as an individual, but improves the performance of the Brayton cycle system significantly. The thermal efficiency showed a significant increase of this parameter, especially for values of α smaller than 100°. They are used in the energy conversion and utilization for liquid to liquid, gas to gas and liquid to gas heat exchange, respectively. The hydraulic results show a relation between the appearance of volumetric flow rate asymmetries and the bifurcation angles throughout the dendritic structure.
In this paper, we review the main advances made by our research group on the heat transfer performance of complex flow architectures embedded in a conducting solid. The useful energy dissipated because of the imperfection of the component decreases as the component size increases. The immediate applications of this work include the design of ground-coupled heat pumps, seasonal thermal energy storage systems, and district heating and cooling systems. Fin's heat exchange is rather complex, because of variation of both temperature along the fin and convective heat transfer coefficient. The performance of the parallel flow configurations is compared with the performance of counterflow configurations. This phenomenon is summarized by the constructal law: the occurrence and evolution of designs in nature, its time direction. The semicircular body that serves as a basement for the T-shaped construct generates heat uniformly and it is perfectly insulated on the outer perimeter.
Changes in configuration are dynamic, thus a time arrow is then associated to the evolution in system's configuration. The fins are bathed by a steady stream with constant ambient temperature and convective heat transfer. However, it was shown that this approach cannot be used because of the effects of two-dimensional heat transfer, especially in the presence of short fins. General Introduction General Overview on Heat Transfer Conservation Equations Dimensionless group Units and conversion factors Overview of heat transfer on extended surfaces State of the art in the T-Shaped Fins Thermal exchange basis T-Shaped fins Y-Shaped fins Modular systems of Y-Shaped fins Heat removal vs Pressure drops Conclusions. Moreover, the fin models gradually tended to be practical and complex. Invoking this law in the engineering field, one should bear in mind that this law is about the direction of evolution in time, and the design phenomenon is dynamic.
This paper faces the problem of geometric optimisation for exchanger profiles with innovative shapes. In this developed method, the effect of dimensionless parameters on the temperature distribution of rotary air preheater was investigated and compared with the results of modified heat transfer coefficient method. This review presents the state of this fast growing field, and draws attention to newly opened directions for original research. However, it was shown that this approach cannot be used because of the effects of two-dimensional heat transfer, especially in the presence of short fins. The results indicate that the constructal tree-shaped minichannel heat sinks have considerable advantages over the traditional serpentine flow patterns in both heat transfer and pressure drop. Heat transfer from finned surfaces is an example of combined heat transfer natural or forced convection on the external parts of the fin, and conducting along the fin. The effect of heat-setting in both media was more significant at 200 °C.
The second part of the paper is devoted to a limited review of second law analysis applied to classic engineering components for heat exchange. The study is applied to a case study of a real biomass boiler. Fin's heat exchange is rather complex, because of variation of both temperature along the fin and convective heat transfer coefficient. The elemental channel pairs are assembled into sequentially larger flow structures first construct, second construct, etc. The hydrodynamic and thermal behavior of the heat sinks are then compared. The core of the constructal theory is that various shapes and structures of the matters in nature are generated from the tendency to obtain optimal performance. The thermal exchange systems therefore have to guarantee better performances in correspondence to ever more severe dimensional constraints.
But the necessity of compact auxiliary systems doesn't regard only the semiconducting industry. Y-shaped profiles were consequently examined, obtained by varying the angle between the two arms of the original T. Configurations i and ii are trees with minimal resistance to fluid flow. This approach represents a departure from the usual approach, where a flow component is optimized in isolation. Starting from the optimal results T-shape optimized fins , we show the trend of the assessment parameter the dimensionless conductance in function of the angle α between the two horizontal arms of the fin.
Results show that the new shape proposed for the fins, together with the assessment of the horizontal width, leads to a novel performance evaluation criterion. The study analyses basic case and a series of alternative scenarios optimized with Constructal Law, guaranteeing the same thermal energy production. This book is based on a design course developed by the two authors for upper-level undergraduates and graduate students at Duke University and other universities all over the world. Abstract The book contains research results obtained by applying Bejan's Constructal Theory to the study and therefore the optimization of fins, focusing on T-shaped and Y-shaped ones. Large organs belong on large vehicles and animals. Maximum thermal efficiency and total tube volume are taken as the optimization objective and constraint, respectively. Design course on the universal principle of configurations in nature and engineering-the constructal law.