Heat Transfer Characteristics of Gaseous Flows in Micro-Channel with Negative Heat Flux

Two-dimensional compressible momentum and energy equations are solved to obtain the heat transfer characteristics of gaseous flows in micro-channels with constant heat flux for which the value is negative for no-slip flow. The numerical methodology is based on the Arbitrary-Lagrangian-Eulerian method. The computations are performed for channels with constant heat flux ranging from ?10⁴ to ?10² W/m². The channel height ranges from 10 to 100 μ m and the aspect ratio of the channel height and length is 200. The stagnation pressure is chosen such that the exit Mach number ranges from 0.1 to 0.7. The outlet pressure is fixed at the atmosphere. The wall and bulk temperatures in micro-channels with negative heat flux are compared with those of positive heat flux cases obtained in our previous work and also those of the incompressible flow in a conventional sized channel. In the case of fast flow, temperatures normalized by heat flux have different trends whether heat flux value is positive or negative. A correlation for the prediction of the wall temperature of the gaseous flow in the micro-channel is proposed. The rarefaction effect is investigated for the cases of channel height of 10 μ m with slip boundary conditions. The magnitudes of viscous dissipation term and compressibility term are also investigated. The effect of each term on heat transfer characteristics is discussed.     

Characterization of Spaghetti Prepared Under Different Drying Conditions

Spaghetti dried at low (max. 50 °C), high (max. 70 °C), and very high (max. 85 °C) temperatures were characterized by their color, surface structure, rupture strength, texture analysis, and sauce retention capacity. The texture and sauce retention capacity were estimated for cooked spaghetti. The color of the spaghetti's methanol extracts, as evaluated through absorbance at 440 and 466 nm, did not depend on the drying temperature. A trend was observed in the surface texture of spaghetti, as estimated by atomic force microscopy and mercury intrusion porosimetry, where the surface was rougher when dried at higher temperatures than at low temperatures. Furthermore, the rupture strength was also higher for the spaghetti dried at higher temperatures. This result can be ascribed to the formation of stronger gluten networks, promoted by denaturation of gluten at the higher temperatures. However, the hardness of cooked spaghetti was not affected by the drying temperature, a result attributable to the action of water sorption to offset any differences in hardness among the spaghettis dried at the 3 different temperatures. The sauce retention capacity of cooked spaghetti was evaluated using a dextran solution as a simulated sauce, and by this method, the capacity of the spaghetti dried at a low temperature was shown to be significantly lower than that of the spaghetti dried at higher temperatures. This can be ascribed to the smoother surface of cooked spaghetti dried at the lower temperature and also to the leakage of amylose onto the surface during cooking.     

Effect of compressibility on gaseous flows in micro-channels

Two-dimensional compressible momentum and energy equations are solved in a parallel plate channel to obtain the effect of compressibility on gaseous flow characteristics in micro-channels. The numerical methodology is based on arbitrary-Lagrangian-Eulerian method. The computations were performed for a wide range of Reynolds number and Mach number and for both ‘no heat conduction’ and isothermal flow conditions. The results are presented in form of the product of friction factor and Reynolds number (f·Re) expressed as a function of both Reynolds number and Mach number and was compared with available experimental results. It was found that f·Re is mainly a function of Mach number and is different from the incompressible value of 96 for parallel-plate channels.     

Experimental study of two-phase pump performance using a full size nuclear reactor pump

The performance of a full-size nuclear reactor primary heat transport pump was investigated experimentally under high pressure, steam–water two-phase flow conditions. A new set of two-phase pump performance test data was obtained with local void fraction and mass flux measurements at the pump suction. The effects of suction temperature and initial flow conditions on the two-phase pump performance characteristics were described.     

Summary of ROSA-IV LSTF first-phase test program — Integral simulation of PWR small-break LOCAs and transients -

Significant experimental results obtained at the ROSA-IV Large-Scale Test Facility (LSTF) during the first phase of the test program (1985–1988) are summarized. The LSTF is a volumetrically scaled, full-height, full-pressure simulator of a Westinghouse-type four-loop (3423 MW thermal power) pressurized water reactor (PWR). The LSTF first-phase program investigated the fundamental PWR thermal-hydraulic responses during small-break loss-of-coolant accidents (SBLOCAs) and transients. The test matrix included twenty-nine SBLOCA tests, three abnormal transient tests and ten steady-state natural circulation tests.     

A 10% cold leg break test at ROSA-IV large scale test facility

The Large Scale Test Facility (LSTF) in the ROSA-IV Program is an integral test facility for investigation of pressurized water reactor (PWR) thermal-hydraulic behavior during small break loss-of-coolant accidents (SBLOCAs) and operational transients.A 10% cold leg break test was conducted in the facility shakedown phase to assess and confirm the facility capability and to collect code assessment data. The test conditions, test procedures and test results are described. The test results are compared with a pretest analysis obtained using RELAP5/MOD1 Cy18.     

Coated optical fibers for high-strength fusion splices

Suitable fiber-coated structures and a practical splice technique which are superior in both long-term reliability and splice operation efficiency in the field are required. A splice technique without using any dangerous chemical acids to remove the primary coat and coated fiber structures are proposed in this paper. With these techniques, an average strength of 0.88 GPa for bare fusion spliced fibers is obtained in the field, which is more than double the value compared with the average strength of 0.4 GPa obtained by the conventional splicing technique, which is used practically in the field. In addition, the splice time decreases to about one-third of the conventional splice time. The splice operation efficiency improvement is recognized for not only coated mono-fibers but for fiber ribbons.     

SSCP analysis of long DNA fragments in low pH gel

AIM: Antigen retrieval (AR) procedures are based on the effect of heating (by either microwave or pressure cooking treatments) on routinely fixed and paraffin embedded tissues. We observed that AR procedures restore the reactivity of endogenous biotin (EB) and report on the distribution of EB following AR in a series of routinely fixed and embedded tissues. METHODS AND RESULTS: Following pressure cooking or microwave treatments, a simple streptavidin-peroxidase staining revealed retrieved endogenous biotin (REB) in normal tissues (such as liver, kidney and adrenal cortex), in oxyphylic cells and in some tumours, especially in carcinomas of the kidney and of the adrenal cortex. In formalin-fixed (but not in alcohol-fixed) tissue sections, the heating procedures caused an intense and finely granular cytoplasmic reaction, following a routine streptavidin-conjugated peroxidase treatment. The staining was prevented by blocking of EB by a sequential avidin-biotin treatment. CONCLUSIONS: Retrieval of EB reactivity can cause pitfalls in diagnostic immunohistochemistry but, alternatively, it might also constitute a useful and novel diagnostic marker.     

NUMERICAL SOLUTION OF MELTING PROCESSES FOR FIXED AND UNFIXED PHASE CHANGE MATERIAL IN THE PRESENCE OF MAGNETIC FIELD--SIMULATION OF LOW-GRAVITY ENVIRONMENT

Transport processes associated with melting of an electrically conducting phase change material (PCM), placed inside a rectangular enclosure, under a low-gravity environment, and in the presence of a magnetic field, is simulated numerically. Electromagnetic forces damp the natural convection as well as the flow induced by sedimentation and/or floatation, and thereby simulate the low-gravity environment of outer space. Computational experiments are conducted for both side-wall heating and top-wall heating under a horizontal magnetic field. The governing equations are discretized using a control-volume-based finite difference scheme. Numerical solutions are obtained for a true low-gravity environment as well as for the simulated low-gravity conditions that are a result of the presence of a horizontal magnetic field. The effects of magnetic field on the natural convection, solid phase floatation/sedimentation, liquid/solid interface location, solid melting rate, and the flow patterns are investigated. It is found that the melting under a low-gravity environment reasonably can be simulated on earth via applying a strong horizontal magnetic field. However, the flow patterns obtained for the true low-gravity environment are not similar to the corresponding cases solved for the simulated low gravity.