Topology Optimization of Two Fluid Heat Transfer Problems for Heat Exchanger Design

Topology optimization of thermal-fluid coupling problems has received widespread attention.This article proposes a novel topology optimization method for laminar two-fluid heat exchanger design.The proposed method utilizes an artificial density field to create two permeability interpolation functions that exhibit opposing trends,ensuring separation between the two fluid domains.Additionally,a Gaussian function is employed to construct an interpolation function for the thermal conductivity coefficient.Furthermore,a computational program has been developed on the OpenFOAM platform for the topology optimization of two-fluid heat exchangers.This program leverages parallel computing,significantly reducing the time required for the topology optimization process.To enhance computational speed and reduce the number of constraint conditions,we replaced the conventional pressure drop constraint condition in the optimization problem with a pressure inlet/outlet boundary condition.The 3D optimization results demonstrate the characteristic features of a surface structure,providing valuable guidance for designing heat exchangers that achieve high heat exchange efficiency while minimizing excessive pressure loss.At the same time,a new structure appears in large-scale topology optimization,which proves the effectiveness and stability of the topology optimization program written in this paper in large-scale calculation.

Design strategy and relevant flow mechanisms of highly loaded 3D compressor tandem cascades

To investigate the design strategy of highly loaded tandem cascades at both the midspan and endwall,the overall performance and flow mechanisms of four typical tandem cascades based on the optimization were analyzed from multiple perspectives numerically.The results show that the interference effects on the Front Blade(FB)and Rear Blade(RB)should not be overlooked during the design phase,and the design strategies at the midspan and endwall are completely different.At the midspan,the optimization aims to increase the interference effects and the strength of the gap jet while maintaining the same load on the FB and RB.However,the endwall optimal airfoil exhibits weakening interference effects,advancement of the gap jet location,and load transfer from the FB to RB.Through further analysis of flow characteristics,the midspan optimal airfoil is beneficial for inhibiting the low-energy fluid from interacting with the suction surface of RB under the design condition,but results in earlier occurrence of corner stall.The endwall optimal airfoil helps suppress the development of the secondary flow and delay the onset of corner stall.Furthermore,by combining the benefits of these two design approaches,additional forward sweep effects are achieved,further enhancing the performance of the tandem cascade.

DNA barcoding reveals commercial fraud related to yak jerky sold in China

Dear Editor, Instances of food mislabeling and adulteration scandals fo- cus public attention on food safety and market fraud. Such scandals force the authorities to enforce stringent regula- tions on food adulteration. The Chinese government and consumers are paying more attention to food resource qual- ity and safety regulation than ever before. The growing food market requires food authenticity at all stages of product processing, while species identification of raw materials is fundamental for food safety. Species substitution causes economical loss to consumers and may negatively affect public sanitation because of possible presence of toxic and parasite-infected species （Galimberti et al., 2013）.

Preparation and pharmacokinetics in vivo of linarin solid dispersion and liposome

Objective:The current investigation aimed to determine the appropriate dosage form by comparing solid dispersion and liposome to achieve the purpose of improving the solubility and bioavailability of linarin.Methods:Linarin solid dispersion(LSD)and linarin liposome(LL)were developed via the solvent method and the thin film hydration method respectively.The Transwell chamber model of Caco-2 cells was established to evaluate the absorption of drug.The pharmacokinetics of linarin,LSD and LL in rats after ig administration were carried out by high performance liquid chromatography(HPLC)method.Results:The solubility of LSD and LL was severally 3.29 times and 3.09 times than that of linarin.The permeation coefficients of LSD and LL were greater than 10^(-6),indicating that the absorption of LSD and LL were both better than linarin.The bioavailability of the LSD was 3.363 times higher than that of linarin,and the bioavailability of LL was 0.9886 times higher than that of linarin.Conclusion:The linarin was more suitable for making solid dispersion to enhance its solubility and bioavailability.

Meta-Transcriptome Profiling of Novel Invasive Pest Spodoptera frugiperda in Yunnan,China

Dear Editor,The fall army worm,Spodoptera frugiperda(Lepidoptera:Noctuidae),a highly agricultural destructive pest of cereals,is originally rampant in tropical and subtropical America(Kenis et al.2019).The caterpillars of this moth feed on more than 350 plant species(Harrison et al.2019),including several economically important cultivated grasses such as maize,rice,sorghum and sugarcane,severely threatening the food security(Cock et al.2017).Spodoptera frugiperda is recognized to comprise two morphologically identical but genetically distinct strains with different host range.The"rice strain^R strain,RS)is thought to preferentially feed on rice and various pasture grasses,while the‘com strain,(C strain,CS)on maize,cotton and sorghum(Juarez et al.2012).Unable to tolerate freezing temperature,S.frugiperda is seldom reported outside of America.However,since its first detection in Nigeria in 2016,several congruent reports from African countries about sudden and severe upsurges of S.frugiperda raised the alarm that S.frugiperda is continuously expanding their range to become truly threat(Goergen et al.2016).