The standard volume to point heat conduction problem is used to determine the optimal topology that maximises the heat transfer. Unlike the constructed theory, the present investigation considers heat dissipation potential function as the objective function, whose gradient field is taken as the criterion for allocation of the limited amount of high conductivity material over the domain. The considered domain is rectangular in geometry, where all its sides are insulated except a centrally located patch on one of the sides, which is maintained at a constant temperature. FEM is used to compute the temperature and it is supplied to the topology optimization algorithm to determine the distribution of material with varied thermal conductivity over the domain. Grid independency is performed for five different grid sizes varying from 10x10 to 90x90. The variation of computation time and objective function with mesh refinement is reported.
Missile's which cruise in air are susceptible to gust loading which leads to fatigue failure, if the missile operates at its own natural frequency. Geometrical model of the typical missile is developed and computational modal analysis is performed. The geometrical model is fabricated and Experimental Modal analysis is performed on it with Free-Free boundary conditions. The obtained natural frequencies are compared with the computational results and the mode shapes are identified.General Terms -Computational Modal analysis, experimental modal analysis i.e. impact hammer test.
Steady state criteria for vanishing small values of Biot number (lumped case) is well known and is reported in every undergraduate text on heat transfer. The heat conduction time scale for pure thermal diffusion problems (extremely large values of Biot number) is also a very well established fact and common knowledge to all well-schooled thermal engineers. However, to the best of the authors’ knowledge no attempt has been made so far to develop a generalized criterion encompassing the entire Biot number range. Hence, the objective of this paper is to construct a simple, but accurate, correlation to predict the onset of steady state for the three basic configurations (plane layer, cylinder, and sphere) for the complete range of Biot number from the high (Bi → ∞) to the low (Bi →0) Bi value limits, while spanning all values in between. Correlations are developed and reported in this paper such that they predict the transient time duration very close to those obtained from the theoretical solution to the problem. Moreover these proposed correlations are extremely simple in form and, as such, are ideal to be used by practicing thermal engineers in need of a quick estimate for the required time period to achieve steady state for problems that can be modeled from these basic geometries. A more accurate correlation, for the case of slab has also been proposed (containing two additional terms) which can be used if higher accuracy in the intermediate Biot number range were to be desired.
In the present study, steady state heat transfer in a slab is analysed by applying the principle of variation calculus to the entropy generation minimization. The governing equation of the phenomena is obtained by minimizing the total entropy generation over the slab by considering the irreversibility and variation of thermal conductivity as a function of spatial co-ordinates. The governing equation is solved to obtain the temperature distribution, internal heat generation due to irreversibility, entropy generation number and entropy transport into system. The apparent heat sources that come into existence because of the irreversibility in heat diffusion have made the minimization of entropy generation feasible.
Solar thermal electricity generation is one of the encouraging technologies for reducing scarcity of electricity in the world in a renewable and sustainable manner. Solar Organic Rankine Cycles (SORC) are sustainable and an eco-friendly means of power production at low and medium heat source temperatures. The proposed system includes a Parabolic Trough Collector based solar system, which operates with Therminol VP-1 oil, a two-tank direct thermal energy storage unit and an Organic Rankine Cycle (ORC) operates with a working fluid Toluene. Improvements in efficiencies of components has cascading benefit in performance of SORC, operating costs and payback period. A comparative energy and exergy analysis study is performed to assess thermodynamic performance of sub critical non-recuperative solar organic Rankine cycle (NR-SORC) on the basis of heat source temperatures and ORC operating parameters. Iterative procedure is adapted in the analysis to find optimal operating parameters to maximize efficiency. Maximum energetic and exergetic efficiencies of SORC are calculated at various optimal T5 and pevp. Variation of optimal mass flow rate values w.r.t time and ηI, ηII w.r.t heat source temperatures are plotted. All in all, the energy efficiency of overall system remained almost the same, when proposed system is operated at exergy based optimal operating conditions as against the energy based. But significant enhancement of 6.61% and 12.42% in exergetic efficiency of ORC and overall system respectively are observed when SORC operates at exergy based optimal operating conditions.
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