Browsing by Author "Xu, Kun"

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Systematic study of packaging designs on the performance of CMOS thermoresistive micro calorimetric flow sensors
(2017-08-01)
Xu, Wei
;
Pan, Liang
;
Gao, Bo
;
Chiu, Yi
;
Xu, Kun
We systematically study the effect of two packaging configurations for the CMOS thermoresistive micro calorimetric flow (TMCF) sensors: S-type with the sensor chip protrusion-mounted on the flow channel wall and E-type with the sensor chip flush-mounted on the flow channel wall. Although the experimental results indicated that the sensitivity of the S-type was increased by more than 30%; the corresponding flow range as compared to the E-type was dramatically reduced by 60% from 0-11 m s(-1) to 0-4.5 m s(-1). Comprehensive 2D CFD simulation and in-house developed 3D numerical simulations based on the gaskinetic scheme were applied to study the flow separation of these two packaging designs with the major parameters. Indeed, the S-type design with the large protrusion would change the local convective heat transfer of the TMCF sensor and dramatically decrease the sensors' performance. In addition, parametric CFD simulations of the packaging designs provide inspiration to propose a novel general flow regime map (FRM), i.e. normalized protrusion d* versus reduced chip Reynolds number Re*, where the critical boundary curve for the flow separation of TMCF sensors was determined at different channel aspect ratios. The proposed FRM can be a useful guideline for the packaging design and manufacturing of different micro thermal flow sensors.
Thermal Decomposition of Ethanol. 4. Ab Initio Chemical Kinetics for Reactions of H Atoms with CH(3)CH(2)O and CH(3)CHOH Radicals
(2011-04-21)
Xu, Z. F.
;
Xu, Kun
;
Lin, M. C.
;
應用化學系
;
Department of Applied Chemistry
The potential energy surfaces of H-atom reactions with CH(3)CH(2)O and CH(3)CHOH, two major radicals in the decomposition and oxidation of ethanol, have been studied at the CCSD-(T)/6-311+G(3df,2p) level of theory with geometric optimization carried out at the BH&HLYP/6-311+G(3df,2p) level. The direct hydrogen abstraction channels and the indirect association/decomposition channels from the chemically activated ethanol molecule have been considered for both reactions. The rate constants for both reactions have been calculated at 100-3000 K and 10(-4) Torr to 10(3) atm Ar pressure by microcanonical VTST/RRKM theory with master equation solution for, all accessible product channels. The results show that the major product channel of the CH(3)CH(2)O + H reaction is CH(3) + CH(2)OH under atmospheric pressure conditions. Only at high pressure and low temperature, the rate constant for CH(3)CH(2)OH formation by collisonal deactivation becomes dominant. For CH(3)CHOH + H, there are three major product channels; at high temperatures, CH(3)+CH(2)OH production predominates at low pressures (P < 100 Torr), while the formation of CH(3)CH(2)OH by collisional deactivation becomes competitive at high pressures and low temperatures (T < 500 K). At high temperatures, the direct hydrogen abstraction reaction producing CH(2)CHOH + H(2) becomes dominant. Rate constants for all accessible product channels in both systems have been predicted and tabulated for modeling applications. The predicted value for CH(3)CHOH H at 295 K and 1 Torr pressure agrees;closely with available experimental data. For practical modeling applications, the rate constants for the thermal unimolecular decomposition of ethanol giving key accessible products have been predicted; those for the two major product channels taking place by dehydration and C-C breaking agree closely with available literature data.
Thermal Decomposition of Ethanol. 4. Ab Initio Chemical Kinetics for Reactions of H Atoms with CH3CH2O and CH3CHOH Radicals
(2011-04-21)
Xu, Z. F.
;
Xu, Kun
;
Lin, M. C.
;
應用化學系
;
Department of Applied Chemistry
The potential energy surfaces of H-atom reactions with CH3CH2O and CH3CHOH, two major radicals in the decomposition and oxidation of ethanol, have been studied at the CCSD-(T)/6-311+G(3df,2p) level of theory with geometric optimization carried out at the BH&HLYP/6-311+G(3df,2p) level. The direct hydrogen abstraction channels and the indirect association/decomposition channels from the chemically activated ethanol molecule have been considered for both reactions. The rate constants for both reactions have been calculated at 100-3000 K and 10(-4) Torr to 10(3) atm Ar pressure by microcanonical VTST/RRKM theory with master equation solution for, all accessible product channels. The results show that the major product channel of the CH3CH2O + H reaction is CH3 + CH2OH under atmospheric pressure conditions. Only at high pressure and low temperature, the rate constant for CH3CH2OH formation by collisonal deactivation becomes dominant. For CH3CHOH + H, there are three major product channels; at high temperatures, CH3+CH2OH production predominates at low pressures (P < 100 Torr), while the formation of CH3CH2OH by collisional deactivation becomes competitive at high pressures and low temperatures (T < 500 K). At high temperatures, the direct hydrogen abstraction reaction producing CH2CHOH + H-2 becomes dominant. Rate constants for all accessible product channels in both systems have been predicted and tabulated for modeling applications. The predicted value for CH3CHOH H at 295 K and 1 Torr pressure agrees;closely with available experimental data. For practical modeling applications, the rate constants for the thermal unimolecular decomposition of ethanol giving key accessible products have been predicted; those for the two major product channels taking place by dehydration and C-C breaking agree closely with available literature data.