Applied Mechanics and Materials Vols. 789-790

Abstract: This paper explicitly highlights the failure analysis and study of thin walled composite beams (multi-cell and multi-tapered) in cantilever configurations when subjected to constrained torsional load, using MSC Patran / Nastran finite element package. Initially, the verification of the model was done with the analytical results in order to ensure the model accuracy. All the multi-tapered beams under examination are composed of closed section and three cell configuration with twisting moment applied at the free end. There is a vivid description of all the effects of different composite material and various stacking sequences on the margin of safety and failure loads. This paper also verifies the influence of various geometrical configurations (Beam lengths, tapered angles and point of variation of tapered angles) of beams on the failure loads. This paper would help in the wing design phase of modern agile and high speed aircraft in which multi-cell closed cross section beams are integral part.

Abstract: The paper presents a study of a thermal assessment of an Organic Rankine Cycle (ORC) energized by heat absorbed from a parabolic trough collector (PTC) located in Derna, Libya. Both the ORC and PTC are modeled using the IPSEpro software. The simulation results are used to evaluate the system performance using energy and exergy analysis. The study showed the PTC collector was the main contributor of the energy and exergy losses within the PTC system and the evaporator within in the ORC. At this specific weather conditions, the ORC was able to produce about 3 MW electrical powers from the powered PTC heat. Moreover, exergy efficiency of the PTC was 47.7 %, the heat engine was 23.3 % and for the overall system (PTC and ORC) was 11.1 %.

Abstract: In this work, a contribution to the modeling and numerical simulation of mixed convection in a horizontal channel heated from below is presented. The lattice Boltzmann model with double thermal populations (TLBM) is used with the D2Q9 model for the dynamic field and D2Q5 for the thermal field. A comparison of the results obtained by the lattice Boltzmann model with those of the literature is presented for an area stretching ratio B = H / L = 20, a Reynolds number Re = 10, Rayleigh Ra = 10⁴ and Peclet number Pe = 20/3. The streamlines and isotherms are presented for different periods of flow.

Abstract: This work presents a numerical investigation of the natural convection in a saturated porous medium bounded by two horizontal concentric cylinders, modeled taking into account the Brinkman term. The governing equations (in the stream function and temperature formulation) were solved using the ADI (Alternating Direction Implicit) method. The results obtained for the bifurcation point are in a good agreement with the available published data for Da≈0. A study of the effect of Darcy number on the bifurcation point is conducted.

Abstract: We suggest method of calculation of one-dimensional temperature field in multilayer nanostructures. Our method allows obtaining non-stationary temperature distribution in the periodical and non-periodical spatial structures with a different degree of periodicity. Comparison temperature distributions in the multilayer nanostructures and equivalent continuous samples are performed in this study. In addition we suggest experimental application of our method for estimation an average value of thermal Kapitza resistance.

Abstract: In recent years, complex district heating systems will become the main style in most of big cities of china. How to simulate the hydraulic and thermal operation becomes more and more import. In this paper, the simulation mathematical model and method on the hydraulic and thermal operation for complex district heating system is proposed. By using the optimal of economical operation efficiency of the heating networks as the objective function and thermal balance as boundary conditions, the mathematical model is established. Meanwhile, the simulation software of hydraulic and thermal operation for complex district heating system has been developed. Functions of software involve information compilation, hydraulic calculation analysis, source thermal operation calculation, etc.

Abstract: The intermittent drawbacks due to fluctuating temperature factor inside photovoltaic (PV) cells have clearly affected the overall energy performance especially in stochastic weather conditions. Temperature element in the tropical regions is a crucial factor to be determined based on Standard Testing Condition (STC) and Nominal Operating Cell Temperature (NOCT) correlations. Based on the crucial implication of heat dissipation, this study shares some insights of five level heat contour covering the surrounding temperature, PV surface temperature, PV bottom temperature and 2-level of two feet height located under PV array. The field data in real-time approach has been brought up in line to support the energy balance modelling for PV applications with localized heat contour analysis using statistical evaluations. The regression analysis of the 3471 data sampling for the period of 5 days (7AM till 7 PM) produces very good results with correlation coefficient, R² = 0.97.

Abstract: Micro heat pipe is a two-phase heat transfer device offering effective high heat-flux removal in electronics cooling. Essentially, micro heat pipe relies on the phase change processes, namely evaporation and condensation, and the circulation of working fluid to function as heat transfer equipment. The vast applications of micro heat pipe in portable appliances necessitate its functionality under different orientations with respect to gravity. Therefore, its thermal performance is strongly related to its orientation. By incorporating solid wall conduction, together with the continuity, momentum, and energy equations of the working fluid, a mathematical model is developed to investigate the heat and fluid flow characteristics of inclined micro heat pipes. We investigate both the favorable and adverse effects of gravity on the circulation rate which is intimately related to the thermal performance of micro heat pipes. The effects of gravity, through the angle of inclination, on the circulation strength and heat transport capacity are analysed. This study serves as a useful analytical tool in the micro heat pipe design and performance analysis, associated with different inclinations and operating conditions.

Abstract: This paper outlines the application of a numerical procedure to compute the LMTD correction factor for one tube pass and one shell pass, namely 1-1, shell-and-tube heat exchangers. Although the procedure was applied for this specific arrangement, it can easily be applied to different heat exchanger arrangements. The numerical methodology is based on an association of ε-NTU and LMTD approaches introduced by Kays and London (1998). Unlike other shell-and-tube heat exchanger arrangements, such as one tube pass and two shell pass, no available analytical expression in closed form is available in the literature. Hence, the presented numerical procedure is applied to determine the LMTD correction factor for 1-1 shell-and-tube heat exchangers and numerical results were obtained by increasing the number of baffles (1, 3, 7, 9, 19 and 49), in order to analyze the obtained results. Finally, charts for the LMTD correction factor is presented as a function of two dimensionless parameters, namely P and R.

Abstract: The failure of brake performance, which is caused by thermal recession under the emergency brake, results in traffic accident frequently. Based on excellent wear-resisting properties of locust’s non-smooth surface structure, bionic brake disc with special surface micro-structure was designed. According to the thermal analysis theory, transient temperature field analysis of the bionic brake disc during the braking process under different initial velocity was analyzed. The results showed that bionic brake disc has excellent heat dissipation ability, which is beneficial to improve the brake performance. The non-smooth surface can store air and dissipate heat, thus reducing the thermal fatigue and thermal wear caused by temperature rise. This research provides a theoretical basis for designing bionic brake discs with excellent heat dissipation performance.