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The scaling laws that are useful in the design of IR ship experiments based on scaled models are reviewed. Such experiments require control of a set of dimensionless variables. Replication of ship IR contrast by scale models requires equality between the dimensionless variables of a full-scale ship and its scaled model. A particular scaling error c...
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... stated, the radiation contribution to the heat transfer coefficient, h r , is determined for given temperatures by the surface emissivity, e. Values of e are listed in Tables 7 and 8, for various metal and non-metal surfaces, respectively. Useful conversion factors are listed in Table 9. ...
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... Material properties are taken from [147]. The right end of the bar is ramped from ambient temperature (T 1 = 300K) to 600K. ...
The development of next generation aircraft is trending towards more interconnected and highly multidisciplinary systems. To better support the design of these systems, an alternative approach to design is needed beyond traditional methods. An automated design approach by means of multidisciplinary design, analysis, and optimization (MDAO) offers the potential to enable aircraft concepts traditional designers may not have considered. However, the selection of objective function for optimization remains an ambiguous choice by the designer. To remove ambiguity from the choice of objective function, a universal measure of performance in the form of exergy and its destruction can be used. Through the quantity of exergy, typically disparate systems such as the force-based approach of aerodynamics can be compared in a one-to-one fashion to the energetic-based approach of a thermal or propulsion system.
In this thesis, a high-fidelity approach for aerodynamic and thermo-mechanical exergy destruction evaluation and sensitivity analysis is provided to enable gradient-based design optimization. To arrive at the exergy destruction equations, a formal development of the entropy balance equation from the concavity property of entropy is presented. From the balance equations, the exergy destruction equations can be derived for arbitrary thermal and fluid processes. The aerodynamic exergy destruction functional is implemented in FUN3D and a rigorous verification effort is conducted demonstrating good functional agreement with test cases. Additionally, the discrete adjoint is implemented and demonstrates discrete agreement with complex-step derivatives. A series of trade studies are then conducted on the Generic Hypersonic Vehicle (GHV) to identify performance metrics of the vehicle. The thermal exergy destruction functional is implemented in MAST along with a series of verification cases for the functional and discrete adjoint demonstrating discrete agreement. A series of thermal exergy destruction trade studies are performed on the GHV and some modeling and design perspectives are discussed. Finally, a series of optimization cases are presented demonstrating the use of exergy destruction as an objective function. A series of inverse design problems are conducted as well as inviscid aerodynamic exergy destruction optimizations of the GHV. These contributions demonstrate the utility of the exergy quantity as a universal measure of performance and push the state of the art in the area of exergy-based analysis and optimization.
... In actuality, maintaining equality between all the non-dimensional characteristics of the fullscale object and the measured model can often present challenges. [7] We define dimensionless variables Substituted these values in equation (7), we get ...
In this paper, we will use analytical methods for solving the fundamental element of a reaction diffusion model in ecology. The model denotes an interaction between two species which describe ecological predations, and mathematically is defined as a system of partial differential equations with initial and boundary conditions. Symmetry Lie group methods are used to transform this model into a system of ordinary differential equations, then this system solved by generalized tanh function method when there exists a small parameter appear in one of the equation.
... This indicates the typical metallic feature of the MAX phases. In addition, MAX phases are thermally conductive, despite that their thermal conductivities (∼20 to 60 W/(m K)) are lower than most metals (∼20 to 400 W/(m K) [94]), as shown in Fig. 3 (c). Among all MAX phases, Ti 2 SC possesses the highest roomtemperature thermal conductivity of 60 W/(m K). ...
The MAX phases are a group of layered ternary, quaternary, or quinary compounds with characteristics of both metals and ceramics. Over recent decades, the synthesis of bulk MAX phase parts for wider engineering applications has gained increasing attention in aerospace, nuclear, and defence industries. The recent adoption of additive manufacturing (AM) technologies in MAX phase fabrication is a step forward in this field. This work overviews the recent progress in additive manufacturing (AM) of bulk MAX phases along with the achieved geometric features, microstructures, and properties after briefing the conventional powder sintering methods of fabricating MAX phase components. Critical challenges associated with these innovative AM-based methods, including , poor AM processability, low MAX phase purity, and insufficient geometric accuracy of the final parts, are also discussed. Accordingly, outlooks for the immediate future in this area are discussed based on the optimization of present fabrication routes and the potential of other AM technologies.
... [12][13][14]. Normally, PV coolers are made of copper, aluminum, stainless steel, or other metals that has suitable thermal properties like thermal conductivity to enhance the heat transfer so that the PV performance can be improved [15,16]. These materials have different lifespans which may be affected by weather conditions [17]. ...
Many coolers are available to improve the photovoltaic module (PV) efficiency. Although the lifespan of the PV cooler is an important parameter that should be taken into account to justify manufacturing such products, there is no evidence found in the literature considering this parameter in the PV cooler performance evaluation, making the comparison between the different types of PV coolers becomes difficult. Hence, this short communication is intended to correlate the lifespan of PV with its cooler. It proposes a new technique by introducing a new terminology called the PV cooler lifespan effectiveness factor whose value is depending on the lifespan of both PV and the cooling technique being utilized. This factor is defined as the ratio of the lifespan of the PV cooler to the lifespan of the PV. From results of the current study, it is shown that there is a proportional relationship between the lifespan of the PV cooler and the new factor. On the other hand, there is an inverse proportional correlation between the PV lifespan and the new factor. The values of the new factor are classified. The PV cooler is considered to be a lifespan effective, if the lifespan effectiveness factor is greater than zero and lesser than or equals to unity. Because the lifespan of the material depends on weather conditions which are different from one place to another. Hence, the value of the PV cooler lifespan effectiveness factor will be different. This could be a limitation of the proposed method. It is concluded that the new technique is helpful in categorizing the performance of PV cooler in terms of lifespan effectiveness which may have a potential to be utilized by PV cooler researcher, designer and/or manufacturer.
... An area of temperature measurement was coated with a thin layer of black graphite spray to achieve a large emissivity coefficient (0.8, an experimentally measured value). This is critical for accurate temperature measurement using an IR technology-based sensor considering the poor emissivity (0.03-0.04) of copper [33,34]. The results in Fig. 5b shows the temperature increase in time under 0, 10, and 20 A/mm 2 . ...
The deformation behavior of Ti-6Al-4V (at.%) wires under direct electric current was investigated. To minimize thermal effects due to Joule heating on plastic deformation, fine Ti-6Al-4V wires with 100 μm diameter were tested by developing and utilizing an innovative electro-thermo-mechanical tensile tester. The force-controlled tensile tester consists of an electronic balance, piezo actuator, optical camera, infrared thermometer, and electric power supply. To characterize the state of Joule heating in the fine wire, the temperatures at the wire and load frame junction were measured with a non-contact infrared thermometer and then a finite element analysis was conducted using the measured temperatures as boundary conditions. For validation of our experimental approach, we have carried out uniaxial tensile testing of Ti-6Al-4V wires under 0, 10, and 20 A/mm² current densities, respectively, and the results were compared with previous reported values. In our specimen, the change of mechanical properties including the reduction of elastic modulus and strength and the increase of ductility and failure strain was observed with increasing the applied current. However, the level of change was not severe compared to other research. It could therefore be concluded that the thermal effect was minimized by using the fine Ti-6Al-4V wire due to the large surface-to-volume ratio. In the analysis of fracture surface, the transition from brittle to ductile fracture mode was clearly observed with increasing the current density.
... A few investigations on the IR signature simulation measurement method have been reported in the previous literature. Massa and Cervenka [8][9][10][11] derived the scaling laws for simulating the IR radiation of a ship with a subscale model. Their derivation is based on one dimensional unsteady heat conduction equation with internal heat source, convective heat transfer boundary conditions and initial conditions. ...
Experimentally simulating the infrared signature of an aircraft with subscale models can significantly reduce the difficulties and costs. The governing equations of fluid flow, heat transfer, and radiation transfer were rendered in only length dimensionless form so that the relationship between infrared signature and scale factor was revealed. Based on the relationship, a method using subscale models to simulate the infrared signature of aircraft was studied. The infrared integrated radiation intensities of four geometrically similar turbofan engine exhaust systems were calculated to validate the simulation measurement method. The results indicate that the parameters of flow field such as velocity, pressure, temperature and mass fraction, as well as the temperatures of walls, are equivalent in the same dimensionless locations in case that the boundary conditions of the geometrically similar models are the same. The relationship between integrated radiation intensity and scale factor is not constant and varies with the aircraft structure and boundary conditions.
Additive Manufacturing in the watch industry
