Higher Critical Power Research Articles

Experimental investigation on a 0.5-metre-long aluminum flat heat pipe for thermal management in electronic devices

In this work, an aluminum flat heat pipe with 500 mm in length and 3 mm in thickness is proposed for efficient long-distance heat transfer and utilization for waste heat recovery. The experiments of aluminum flat heat pipes with different filling ratios are carried out under different inclination angles. The surface temperature distribution, critical power, thermal resistance, and thermal conductivity of aluminum flat heat pipes are experimentally investigated, respectively. The results indicate that the optimized liquid filling ratio of the aluminum flat heat pipe is 30 %, and the recommended working angle is 90° (with gravity assistance). The optimized aluminum flat heat pipe has good temperature distribution, a high critical power (110 W), a low thermal resistance (0.25 ℃/W@90 W), and excellent thermal conductivity (13880 W/(m·K) @90 W). In addition, the aluminum flat heat pipe has a low density of 1.8 g/cm3, which is suitable for lightweight and efficient heat dissipation applications, especially for the aerospace field. Furthermore, the application of long aluminum flat heat pipe for waste heat recovery is also demonstrated, showing great potential advantages in wide industrial fields.

Self-Guiding of Long-Wave Infrared Laser Pulses Mediated by Avalanche Ionization.

Nonlinear self-guided propagation of intense long-wave infrared (LWIR) laser pulses is of significant recent interest, as it promises high power transmission without beam breakup and multifilamentation. Central to self-guiding is the mechanism for the arrest of self-focusing collapse. Here, we show that discrete avalanche sites centered on submicron aerosols can arrest self-focusing, providing a new mechanism for self-guided propagation of moderate intensity LWIR pulses in outdoor environments. Our conclusions are supported by simulations of LWIR pulse propagation using an effective index approach that incorporates the time-resolved plasma dynamics of discrete avalanche breakdown sites.

FROM MODERATISM TO FUNDAMENTALISM; Portrait of Shifting the Religious Understanding of Makassar Islamic Students

Students have been asked as intellectuals who have high critical power. Therefore students are not only a driver of a social change, but at the same time are not easily influenced or participate in certain currents of thought and understanding, especially if it is related to religious understanding. Students' critical attitude becomes a kind of filter to sort and filter out various religious ideas and ideas. But the view that sees students, especially Muslim students as a critical group, seems to be faltering lately. Instead of being a critical community group with a variety of new religious understandings, Muslim students actually became the target of the new Islamic doctrine of religious understanding. The doctrine of religious understanding is precisely textualism and fundamentals. This qualitative research shows that several large campuses in Makassar were exposed to the Islamic understanding and changed them from moderate Muslim students to Muslim fundamentalist students.

The effect of oxygen starvation on ignition phenomena in a reactive solid containing a hot-spot

In this paper, we explore the effect of oxygen supply on the conditions necessary to sustain a self-propagating front from a spherical source of heat embedded in a much larger volume of solid. The ignition characteristics for a spherical hot-spot are investigated, where the reaction is limited by oxygen, that is, reactant + oxygen → product. It is found that over a wide range of realistic oxygen supply levels, constant heating of the solid by the hot-spot results in a self-propagating combustion front above a certain critical hot-spot power; this is clearly an important issue for industries in which hazard prevention is important. The ignition event leading to the formation of this combustion wave involves an extremely sensitive balance between the heat generated by the chemical reaction and the depletion of the reactant. As a result, for small hot-spot radii and infinite oxygen supply, not only is there a critical power above which a self-sustained combustion front is initiated there also exists a power beyond which no front is formed, before a second higher critical power is found. The plot of critical power against hot-spot radius thus takes on a Z-shape appearance. The corresponding shape for the oxygen-limited reaction is qualitatively the same when the ratio of solid thermal diffusion to oxygen mass diffusion (N) is small and we establish critical conditions for the initiation of a self-sustained combustion front in that case. As N gets larger, while still below unity, we show that the Z-shape flattens out. At still larger values of N, the supercritical behaviour becomes increasingly difficult to define and is supplanted by burning that depends more uniformly on power. In other words, the transition from slow burning to complete combustion seen at small values of N for some critical power disappears. Even higher values of N lead to less solid burning at fixed values of power.

高性能ＢＷＲ燃料集合体の開発 サイクロンスペーサの熱水力性能

The purpose of this study is to develop a new BWR fuel with high critical power and low pressure drop performance. In this report, the spacer which has a significant effect on thermal hydraulic performance, has been improved and the performance has been measured. The improved high performance spacer is a ferrule type spacer with twisted tape and improved flow tab. This spacer is called CYCLONE spacer. The test bundle consists of electrically heated rods in a 4×4 array configuration. The axial power shape is cosine. Two test assemblies with different radial power distribution have been used. One test assembly has the maximum power rods at the center of the test assembly and the other has the maximum power rods near the channel wall. The results show that the critical power performance of the bundle with CYCLONE spacers is 10 to 22% higher than that of the current bundle with ferrule spacers at BWR rated flow rate, while the pressure drop is about 3% higher at BWR rated conditions (quality 15%).

Thermal Focusing of Elliptically Shaped Optical Beams in Dielectrics

The authors report a study on thermal lensing of an elliptically shaped optical beam in an absorbing dielectric media. It is found in the case of lead glass (with dn/dT, the rate of change of refractive index with temperature, positive) that the beam gets focused at different focal points in different directions, exhibiting the effect of astigmatism. There are several critical points, below the lowest of which there is no self-focusing, but at higher powers one dimension focuses while the other defocuses. Above the higher critical power, both dimensions self-focus, and the dimensionless beam-width parameters f1 and f2 for x and y focusing reach different minima corresponding to different self-focusing distances, beyond which both dimensions continue to diverge. In the case of crystal NaCl (where dn/dT is ne gative), both dimensions of the beam defocus, whatsoever the power of the incident beam.