In this work the transformation induced fatigue of Ni-rich NiTi shape memory alloys (SMAs) was investigated. The aerospace industry is currently considering implementing SMA actuators into new applications. However, before any new applications can be put into production they must first be certified by the FAA. Part of this certification process includes the actuator fatigue life. In this study, as-received and polished at dogbone SMA specimens underwent transformation induced fatigue testing at constant loading. The constant applied loading ranged from 100 MPa to 200 MPa. Specimens were thermally cycled through complete actuation (above Af to below Mf ) by Joule heating and environmental cooling. There were three cooling environments studied: liquid, gaseous nitrogen and vortex cooled air. It was shown that polished specimens had fatigue lives that were two to four times longer than those of as-received specimens. Test environment was also found to have an effect on fatigue life. Liquid cooling was observed to be corrosive, while the gaseous nitrogen and vortex air cooling were observed to be non-corrosive. The two non-corrosive cooling environments performed similarly with specimen fatigue lives that were twice that of specimens fatigue tested in the corrosive cooling environment. Transformation induced fatigue testing of polished specimens in a non-corrosive environment at 200 MPa had an average fatigue life of 14400 actuation cycles; at 150 MPa the average fatigue life was 20800 cycles and at 100 MPa it was 111000 cycles. For all specimens constant actuation from the beginning of testing until failure was observed, without the need for training. Finally, a microstructural study showed that the Ni3Ti precipitates in the material were one of the causes of crack initiation and propagation in the actuators.

The hot carrier dynamics of Zn0.91Cd0.09Se/ZnSe multi-quantum wells were studied using the femtosecond time-resolved photoluminescence upconversion technique. The carrier cooling behavior was investigated for different compositions at various lattice temperatures. The hot carriers generated photoexcitation by 405nm Ti:sapphire laser pulses release their excess energy primarily through carrier-LO-phonon interaction. As the excess energy reduce to the amount that lower than the energy of LO phonon, the excess energy was released by carrier-TA-phonon scattering before radiative recombination occurs. We have determined the scattering times of carrier-LO-phonon scattering at different lattice temperatures. No hot phonon effects was found at low photoexcited carrier density. The dependence of photoluminescence lifetime on wavelength was also discussed.

Abstract We have extended the spectral range of the current PL-upconversion apparatus to be operated in infrared. Using the IRPL-upconversion¡Awe study the behavior of carrier cooling of InN film and the relationship between the spacer and lifetime in InAs/GaAs stacked QDs . We excited InN film of the band gap of 0.74eV with ultrafast Ti:sapphire laser of the wavelength 404nm. We found the phonon emission time by hot carriers of InN is 14fs. The hot carriers release their excess energy to the lattice of 35K with a timescale of 100ps. We observed in InAs/GaAs QDs that the shorter life time for samples with thin spacer is due to tunneling effect.

A numerical study was carried out for enhanced heat transfer from two heated blocks in a pulsating channel flow by porous heat sink. The flow over the fluid region is governed by the Navier-Stokes equation, and the flow through the porous medium is governed by the Darcy-Brinkman-Forchheimer equation. These two flows are coupled through the interface boundary conditions at the porous/fluid and porous/solid interfaces. After a stream function-vorticity transformation, solution of the coupled governing equations for fluid/porous/solid composite system is obtained using the control-volume-based procedure and hybrid scheme. Comprehensive time-dependent flow and temperature data obtained and averaged over a cycle of pulsation in a periodic steady state. In addition, this study details the effects of variation in the governing parameters, such as inertia parameter, Dracy number, Reynolds number, Strouhal number, pulsation amplitude and geometric parameters, to illustrate important fundamental and practical results. The results show that the periodic change of shape of interblock recirculation flow caused by porous-covering blocks has significant enhanced effect on flow pattern and heat transfer characteristics. This enhanced effect is found to increase with Reynolds number, Strouhal number and pulsation amplitude but decrease with Dracy number. In comparison with the non-porous heat sink case for a steady non-pulsating flow, significant increases in the average Nusselt number are predicted and the instantaneous maximum temperatures within the heated block array are reduced. Moreover, it is shown that specific choices in certain geometric parameters, such as interblock space, can make pronounded change in the cooling of heated block.

Abstract The present investigation is performed by repeated experiments to simulate the impingement cooling heat transfer in leading-edge region of gas turbine with thermochromic liquid crystals. The experiments was studied on a rotating square duct without crossflow effect from three different rotational speeds of 0, 30 and 60 rpm. The study covered jet Reynolds number 7000 to 9000 and the rotational speeds from 0 to 60 rpm. Results are presented and focused on the effect of three different rotational speeds. Nusselt number values increased (up to 14%) with Reynolds number. However, Rotation induced coriolis and centrifuged forces and decreased the Nusselt number values about 9% which is quite coincided with those of previous studies.

Taiwan is the major country of importing LNG. In this paper discussed LNG cold energy recovery used in cold storage warehouse and other energy conservation systems. In the cold storage warehouse systems that showed the less temperature of cold storage warehouse the more exergy efficiency and the best exergy efficiency is 30%. Base on thermoeconomic analysis there was the optimal operation temperature at -70¢J. In the purifier nitrogen system (PNS), the investigation indicated the best efficient operating temperature at -150¢J. But with economic analysis the optimal design temperature of this PNS was -130¢J. And the last energy conservation system was the running power plane. In this research studied the power planes used LNG cold energy as inlet air-cooling systems. According to the investigation that showed the systems increased power output up to 14.4¢H in the 4.5¢J of inlet air cooling temperature. And these systems also improved the heat rate of power planes about 0.98%. The conclusions presented that the potentialities of LNG cold energy are huge, and with proper engineering and economic analysis could make these energy conservation systems more feasible.

This experimental study contains two points; part1 – turbine blade heat transfer under low Reynolds number flow conditions, and part 2 – trailing edge cooling and heat transfer. The effect of unsteady wake and free stream turbulence on heat transfer and pressure coefficients of a turbine blade was investigated in low Reynolds number flows. The experiments were performed on a five blade linear cascade in a low speed wind tunnel. A spoked wheel type wake generator and two different turbulence grids were employed to generate different levels of the Strouhal number and turbulence intensity, respectively. The cascade inlet Reynolds number based on blade chord length was varied from 15,700 to 105,000, and the Strouhal number was varied from 0 to 2.96 by changing the rotating wake passing frequency (rod speed) and cascade inlet velocity. A thin foil thermocouple instrumented blade was used to determine the surface heat transfer coefficient. A liquid crystal technique based on hue value detection was used to measure the heat transfer coefficient on a trailing edge film cooling model and internal model of a gas turbine blade. It was also used to determine the film effectiveness on the trailing edge. For the internal model, Reynolds numbers based on the hydraulic diameter of the exit slot and exit velocity were 5,000, 10,000, 20,000, and 30,000 and corresponding coolant – to – mainstream velocity ratios were 0.3, 0.6, 1.2, and 1.8 for the external models, respectively. The experiments were performed at two different designs and each design has several different models such as staggered / inline exit, straight / tapered entrance, and smooth / rib entrance. The compressed air was used in coolant air. A circular turbulence grid was employed to upstream in the wind tunnel and square ribs were employed in the inlet chamber to generate turbulence intensity externally and internally, respectively.

Determination of an extender protocol which will enhance the viability of frozenthawed bovine spermatozoa will allow producers to obtain higher conception rates due to the increased survival rate of the spermatozoa. Ejaculates of six Brangus bulls (age=18 months) were evaluated for spermatozoal motility, acrosomal integrity, and morphological characteristics (collectively called spermatozoal viability) in two experiments to test our hypotheses that (1) the treatment combination of a 4 hr cooling duration and a 2 hr equilibration with glycerol will result in optimum spermatozoal characteristics after freezing and thawing and (2) rank of three selected extenders relative to their effects on spermatozoal viability after freezing and thawing will be egg yolk-citrate (EC), egg yolk-tris (IMV), and skim milk (milk). In experiment 1, an ejaculate from each bull was partially extended and cooled to 4 ºC for either 2 or 4 hr and then allowed to equilibrate with the glycerolated extender for 2, 4, or 6 hr. Spermatozoal viability was assessed at 0, 3, 6, and 9 hr after thawing. In experiment 1, 4 hr of cooling resulted in a higher percentage of motile spermatozoa than did 2 hr of cooling. The 2 hr equilibration with glycerol yielded lower percentages of motile spermatozoa, acrosomal integrity, and morphologically normal spermatozoa than 4 and 6 hr equilibration durations with glycerol. In experiment 2, we observed a decrease in spermatozoal viability for all three extenders upon freezing and thawing. Viability of frozen-thawed spermatozoa extended in the milk was reduced for all incubation durations, and the IMV extender had a higher percentage of motile spermatozoa than the EC extender at 6 hr of incubation. A higher percentage of intact acrosomes was observed with the IMV extender; however, the EC extender had a higher percentage of morphologically normal spermatozoa than the IMV extender. Our results indicate that at cooling duration of 4 hr and a 4 hr equilibration with glycerol provide the highest level of spermatozoal viability post-thaw of the treatments evaluated and that the IMV extender enhances the percentage of spermatozoa with an intact acrosome for frozenthawed spermatozoa over the EC and skim milk extenders.

Research is performed to assess the potential of surface moisture evaporative cooling from composite plates as a means of reducing the external temperature of military aircraft. To assess the feasibility of evaporative cooling for this application, a simplified theoretical model of the phenomenon is formulated. The model consists of a flat composite plate at an initial uniform temperature, T0. The plate also possesses an initial moisture (molecular water) content, M0. The plate is oriented vertically and at t=0 s, one surface is exposed to a free stream of air at an elevated temperature. The other surface is exposed to stagnant air at the same temperature as the plate’s initial temperature. The equations associated with energy and mass transport for the model are developed from the conservation laws per the continuum mechanics hypothesis. Constitutive equations and assumptions are introduced to express the two nonlinear partial differential equations in terms of the temperature, T, and the partial density of molecular water, ρw. These equations are approximated using a weak form Galerkin finite element formulation and the α–family of time approximation. An algorithm and accompanying computer program written in the Matlab programming language are presented for solving the nonlinear algebraic equations at successive time steps. The Matlab program is used to generate results for plates possessing a variety of initial moisture concentrations, M0, and diffusion coefficients, D. Surface temperature profiles, over time, of moisture bearing specimens are compared with the temperature profiles of dry composite plates. It is evident from the results that M0 and D affect the surface temperature of a moist plate. Surface temperature profiles are shown to decrease with increasing M0 and/or D. In particular, dry and moist specimens are shown to differ in final temperatures by as much as 30°C over a 900 s interval when M0 = 30% and D is on the order of 10–8m2/s (T0 = 25°C, h = 60 W/m2°C, T∞ = 90°C).

This work addresses the problem of using seawater for cooling and the associated environmental problems caused by the usage and discharge of biocides. The discharged biocide and its byproducts are toxic to aquatic lives and must be decreased below certain discharge limits on load prior to discharge. The conventional approach has been to add biocide removal units as an end-of-pipe treatment. This work introduces an integrated approach to reducing biocide discharge throughout a set of coordinated strategies for inplant modifications and biocide removal. In particular, process integration tools are used to reduce heating and cooling requirements through the synthesis of a heat-exchange network. Heat integration among process of hot and cold streams is pursued to an economic extent by reconciling cost reduction in utilities versus any additional capital investment of the heat exchangers. Other strategies include maximization of the temperature range for seawater through the process and optimization of biocide dosage. This new approach has the advantage of providing cost savings while reducing the usage and discharge of biocides. A case study is used to illustrate the usefulness of this new approach and the accompanying design techniques.