The performance of direct air-cooled steam condenser in power plant plays an important role in its safe and economical operation. It is important to establish the performance evaluation method by investigating the influences of various operating parameters on the direct air-cooled condenser performance. Based on the theoretical analysis of the heat transfer in direct air-cooled condenser, the correlation between the exhaust steam pressure and the saturated exhaust steam flow rate, cooling air flow rate, heat transfer coefficient and area of the condenser and the ambient temperature was presented. The influences of these parameters on the condenser performance were analyzed. The performance evaluations based on the saturated exhaust steam flow rate and exhaust steam pressure were compared and the shortcomings of these two methods were analyzed in which only the heat transfer capacity was examined thus the heat transfer area and the investment of condensers increased. Besides the heat transfer capacity, the heat transfer coefficient of direct air-cooled condenser should be taken into account. The heat transfer coefficient was suggested as another performance evaluation parameter.
Experimental studies on the film cooling effectiveness of turbulent flow over an adiabatic flat plate have been carried out. Schiieren photographs for different flow rates are given. Experimental studies of the heat transfer coefficient of an electrically heated flat plate are compared with theoretical results. The fluctuating velocity and turbulence intensity distributions at different sections of the nonisothermal film cooling flowfield were measured by a hot film anemometer. The film cooling effectiveness equations can be modified by the turbulence mixing coefficient.
Heat transfer characteristics of nanofluids in an acoustic cavitation field have been investigated experimentally. The effects of acoustical parameters, nanofluids concentration, and fluid subcooling on heat transfer are determined in detail. Results show that acoustic cavitation and nanometer particles have a profound influence on single-phase convection and boiling heat transfer of a horizontal circular copper tube. The former is mainly ascribed to the impingement and disturbance of cavitation bubbles and anticipatory activation of smaller vapor embryos within the cavities, while the latter is caused by roughness modification of the tube surface. The above mechanisms are given based on the Schlieren photographs and optical observation. Acoustic cavitation has been shown to be a good way to reduce or eliminate boiling hysteresis.
The aim of this study was to investigate the genetic parameters and genetic architectures of six milk production traits in the Shanghai Holstein population. The data used to estimate the genetic parameters consisted of 1,968,589 test-day records for 305,031 primiparous cows. Among the cows with phenotypes, 3,016 cows were genotyped with Illumina Bovine SNP50K BeadChip, GeneSeek Bovine 50K BeadChip, GeneSeek Bovine LD BeadChip v4, GeneSeek Bovine 150K BeadChip, or low-depth whole-genome sequencing. A genome-wide association study was performed to identify quantitative trait loci and genes associated with milk production traits in the Shanghai Holstein population using genotypes imputed to whole-genome sequences and both fixed and random model circulating probability unification and a mixed linear model with rMVP software. Estimated heritabilities (h2) varied from 0.04 to 0.14 for somatic cell score (SCS), 0.07 to 0.22 for fat percentage (FP), 0.09 to 0.27 for milk yield (MY), 0.06 to 0.23 for fat yield (FY), 0.09 to 0.26 for protein yield (PY), and 0.07 to 0.35 for protein percentage (PP), respectively. Within lactation, genetic correlations for SCS, FP, MY, FY, PY, and PP at different stages of lactation estimated in random regression model were ranged from -0.02 to 0.99, 0.18 to 0.99, 0.04 to 0.99, 0.04 to 0.99, 0.01 to 0.99, and 0.33 to 0.99, respectively. The genetic correlations were highest between adjacent DIM but decreased as DIM got further apart. Candidate genes included those related to production traits ( DGAT1 , MGST1 , PTK2 , and SCRIB ), disease-related ( LY6K , COL22A1 , TECPR2 , and PLCB1 ), heat stress–related ( ITGA9 , NDST4 , TECPR2 , and HSF1 ), and reproduction-related ( 7SK and DOCK2 ) genes. This study has shown that there are differences in the genetic mechanisms of milk production traits at different stages of lactation. Therefore, it is necessary to conduct research on milk production traits at different stages of lactation as different traits. Our results can also provide a theoretical basis for subsequent molecular breeding, especially for the novel genetic loci.
Because of its strong scattering effect in biological tissue, laser light (especially at near-infrared wavelength) can heat a comparatively large volume of tissue. This volume heating, coupled with other advantages (e.g. lasers can deliver high intensity light to small well-defined areas under precise control), makes the laser an excellent heat source. It can thus be used to achieve the thawing of frozen biological tissue. This may have great potentials in medicine (e.g. rewarming of cryopreserved biological tissue) and food industry.
Experiments were performed to investigate the heat transfer characteristics of coupled pulsating heat pipe and single pulsating heat pipe,with the main pulsating heat pipe filled with the same substance and a constant temperature water bath as heat source.The heat transfer characteristics and the wall temperature of the coupled pulsating heat pipe were analyzed and compared with the single pulsating heat pipe under the same conditions.The results showed that with the same heat source and cooling source temperature,the heat absorption and heat output of the coupled pulsating heat pipe were greater than those of the single heat pipe,and the heat transfer was also better in the case of small temperature difference.For the same water bath temperature,the oscillation amplitude of the wall temperature in the condenser section of the coupled pulsating heat pipe was significantly lower than that of the single heat pipe,while the oscillation frequency increased significantly.The coupled pulsating heat pipe improves the alternating phase transition between the liquid column evaporation and the steam plug condensation inside the main pulsating heat pipe,thus reinforcing the heat transfer between the gas-liquid medium and the wall.
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