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Effects of coolant temperature on particulate deposition and cooling efficiency of EGR coolers
Xun Zhang,Wei Tian,Jinhui Li,Zhiqiang Han,Xueshun Wu 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.7
Porous fouling layers formed by particulate deposition in the EGR cooler tubes degrade the cooling efficiency of the EGR coolers. This research has investigated the changes of the particulate concentration under varied coolant temperature conditions and the effects of the coolant temperature on the cooling efficiency of the cooler tubes by measuring the particulate concentration and size distribution at the cooler inlet and outlet. The experiment results indicate that for the particulates of different sizes, the thermophoretic force acting on them and the regeneration vary under the same experiment conditions, presenting distinctive effects on the particulate concentration distribution in the exhaust gas and causing concentrations of nuclear particulates and aggregated particulates to change, respectively. The mass of fouling layers inside the cooler tubes increases as the coolant temperature decreases. Decreasing the coolant temperature not only increases the quantity of fouling particulates but also forms more particulates of big sizes, causing cooling efficiency of the cooler tube per unit length to decrease with the decrease of coolant temperature and the increase of the tube length.
Effects of gas flow on particulate deposition in EGR coolers
Xun Zhang,Jihui Li,Zhiqiang Han,Xunshun Wu,Wei Tian 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.1
This paper presents the test approach to investigate the effects of gas flow rate on particulate deposition inside the exhaust gas recirculation (EGR) coolers. The tests were carried out on a diesel engine equipped with the EGR cooler that a given total gas flow rate passed through and that contained pluggable exchanger tubes to adjust the flow rate in the tubes. Test results show that under the given coolant temperature and EGR gas temperature, the lower flow rate in the exchanger tube is and the longer tubes are, the more particulate with D p > 50 nm deposit in the cooler. With the given total gas flow rate passing through the cooler, the lower flow rate in the exchanger tube is and the longer tubes are, the larger deposit mass is inside the cooler. In the cases of longer tubes, the effects of gas flow rate on the deposit mass are depends on the effects of gas velocity on the particulate deposition, rather than the effects of flow rate on the particulate number passing through the heat exchanger tube per minute.
Production of Recombinant Humanized Anti-HBsAg Fab Fragment from Pichia pastoris by Fermentation
Deng, Ning,Xiang, Junjian,Zhang, Qing,Xiong, Sheng,Chen, Wenyin,Rao, Guirong,Wang, Xunzhang Korean Society for Biochemistry and Molecular Biol 2005 Journal of biochemistry and molecular biology Vol.38 No.3
In this report, we describe the high-yield secretory expression of the recombinant human anti-HBsAg Fab fragment from Pichia pastoris that was achieved by co-integration of the genes encoding the heavy and light chains (both under the control of alcohol oxidase promoter) into the genome of the yeast cells. The fed-batch fermentations were carried out in a 5 L scale. Both chains of the Fab were successfully expressed upon methanol induction. The absorbance ($OD_{600}$) of the broth can reach 350~500 at the end of fed-batch phase. After the induction, the expression level of the recombinant Fab (soluble) reached 420~458 mg/L. The recombinant Fab fragment was purified from the crude culture supernatant by ion exchange chromatography and the purity of the recombinant Fab fragment was over 95%. The affinity activities of the crude fermentation supernatant and the purified Fab were analyzed by indirect ELISA, which showed that the purified recombinant Fab fragment had high affinity activity with hepatitis B surface antigen.