Assessment of CHF and Post-CHF Heat Transfer Models for High-Pressure Condition

Supercritical heat transfer systems may undergo trans-critical procedures and work at subcritical conditions during startup, shutdown, or some accidents. However, well-validated heat transfer models for the high-pressure condition (P/Pc>0.7) are still missing. In the present work, with exhaustive literature review, extensive experimental databanks of CHF and post-dryout heat transfer under high-pressure condition are established, respectively. Existing prediction models for the high-pressure condition are also summarized from all over the world. Thereby, with the aid of the high-pressure experimental databank, prediction models get evaluated. It has been demonstrated that CHF correlation developed by Song et al. shows good predictive capability. Post-dryout heat transfer could get well predicted by the Song correlation. These recommended prediction models could be implemented to upgrade safety analysis codes for simulation of trans-critical transients.

Effect of Process Variables on Rice Flour Functional Properties, and Porous Structure Properties of Rice and Wheat-Based Leavened Food Products

Research background. Various processing techniques impart significant impacts on physicochemical and functional properties of rice flour and the quality of the final products. This study aims to modify rice flour from different treatment combinations and to select the best treatment combination in developing rice-wheat-based leavened food products. Experimental approach. Eight treatment combinations were applied on rice flour according to 23 factorial design considering three variables at two levels namely, pre-treatment for rice grain modification [heat-moisture treatment, dual modification treatment (soaking rice grains in a NaHCO3 solution followed by heat treatment)], grinding technique (dry grinding, wet grinding), and flour particle size (75-180 µm, <75 µm). Eight dough samples were prepared by mixing 50 g of rice flour from each treatment with 50 g wheat flour. Thereafter, the dough samples were subjected to fermentation and gelatinization under pressurized condition (externally applied 1.0 kg/cm2 initial air pressure condition) in a pressure adjustable chamber. Results and conclusions. Results rendered that rice flour sample that underwent heat-moisture treatment followed by wet grinding and particle size at 75-180 µm, impart to improve the leavened gas retention capacity and obtaining highly porous and better textured rice-wheat based leavened food products under 1.0 kg/cm2 externally applied initial air pressure condition. Novelty and scientific contribution. Rice flour can be modified according to the present method to improve functional flour properties and the textural and structural properties of rice-wheat based leavened food products. Also, conducting fermentation and gelatinization under pressurized condition is a novel food processing technique, which contributes in restricting the escape of leavened gas from rice-wheat composite dough mass.

Wear Analysis of a Low-Speed Diesel Engine Connecting Rod Based on Orthogonal Simulation Test

As con-rod is a critical component in an engine, its reliability overwhelmingly directly affects the performance of the whole diesel engine. The fretting wear of con-rod bushing mainly occurs on the contact surface with con-rod small end and con-rod small end cap. In the proposed study, the contact process of con-rod small end, con-rod small end cap and bushing under maximum combustion pressure condition was analyzed, and the distribution of contact pressure and friction stress was analyzed. Then the orthogonal simulation test was designed. According to the contact mechanics theory, the interference amount and friction coefficient of the contact surface were taken as the test factors, and the maximum contact pressure and friction stress under the maximum combustion pressure condition were taken as the objective functions. The influence of the test factors on the objective function was analyzed, and the most reasonable interference amount and friction coefficient were found, so as to slow down the fretting wear of the con-rod bushing.

High-Density Patterned Array Bonding through Void-Free Divinyl Siloxane Bis-Benzocyclobutene Bonding Process

Divinylsiloxane-bis-benzocyclobutene (DVS-BCB) has attracted significant attention as an intermediate bonding material, owing to its excellent properties. However, its applications are limited, due to damage to peripheral devices at high curing temperatures and unoptimized compressive pressure. Therefore, it is necessary to explore the compressive pressure condition for DVS-BCB bonding. This study demonstrates an optimization process for void-free DVS-BCB bonding. The process for obtaining void-free DVS-BCB bonding is a vacuum condition of 0.03 Torr, compressive pressure of 0.6 N/mm2, and curing temperature of 250 °C for 1 h. Herein, we define two factors affecting the DVS-BCB bonding quality through the DVS-BCB bonding mechanism. For strong DVS-BCB bonding, void-free and high-density chemical bonds are required. Therefore, we observed the DVS-BCB bonding under various compressive pressure conditions at a relatively low temperature (250 °C). The presence of voids and high-density crosslinking density was examined through near-infrared confocal laser microscopy and Fourier-transform infrared microscopy. We also evaluated the adhesion of the DVS-BCB bonding, using a universal testing machine. The results suggest that the good adhesion with no voids and high crosslinking density was obtained at the compressive pressure condition of 0.6 N/mm2. We believe that the proposed process will be of great significance for applications in semiconductor and device packaging technologies.