Key Laboratory of Railway Vehicle Thermal Engineering

Lanzhou, China

Key Laboratory of Railway Vehicle Thermal Engineering

Lanzhou, China

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Zhou W.-H.,Lanzhou Jiaotong University | Zhou W.-H.,Key Laboratory of Railway Vehicle Thermal Engineering | Wang L.-C.,Key Laboratory of Railway Vehicle Thermal Engineering | Wang L.-C.,Lanzhou Jiaotong University | And 2 more authors.
IEEE Transactions on Instrumentation and Measurement | Year: 2014

The method of measuring the dynamic characteristics of microhumidity sensors is becoming a bottleneck in developing fast-response humidity sensors. This paper introduces a method for measuring the dynamic characteristics of microhumidity sensors. In this method, two environments with different relative humidity (RH1 and RH2) are established using different saturated aqueous solutions of salt. There is independent air circulation for each environment. These loops of air circulation are connected to the test cell, where the tested sensor is located. Air coming from the RH1 environment always flows over the tested sensor until the valves controlling the air circulation of the RH2 environment operate. Then, the air humidity of the test cell is quickly changed from RH1 to RH2. By decreasing the time needed to change the humidity of the air in the test cell, the response time of the tested sensor can be obtained more precisely. A prototype based on this method is built, and it is tested by measuring the dynamic behavior of a parallel plate capacitance humidity sensor based on polyimide. The analytical results show that the response time of the prototype is less than 250 ms. The response time of the prototype can be improved greatly by enhancing the response time of the subassemblies used in the prototype. © 2014 IEEE.


Zhang Q.,Lanzhou Jiaotong University | Zhang Q.,Key Laboratory of Railway Vehicle Thermal Engineering | Wang L.-B.,Lanzhou Jiaotong University | Wang L.-B.,Key Laboratory of Railway Vehicle Thermal Engineering
Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics | Year: 2016

With air as the medium in this paper, a numerical method is used to study the convective heat transfer in a channel mounted with rectangular winglet pair (RWP) and delta winglet pair (DWP) on the bottom wall. Reynolds number is 200. When the convection of heat flux equation is used, conducted a detailed analysis of the combination of heat flux with velocity gradient and velocity with heat flux gradient contribute the heat transfer enhancement. The results show that Vortex of mounted with RWP is more intense than mounted DWP. Mounted RWP have a better enhanced heat transfer than mounted DWP. But the compression of resistance coefficient and enhance heat transfer, DWP performance better heat flux with velocity gradient and velocity with heat flux gradient contribute the heat transfer enhancement are also significant differences. © 2016, Science Press. All right reserved.


Wang Y.,Lanzhou Jiaotong University | Wang Y.,Key Laboratory of Railway Vehicle Thermal Engineering | Wang L.,Key Laboratory of Railway Vehicle Thermal Engineering
Yingyong Lixue Xuebao/Chinese Journal of Applied Mechanics | Year: 2014

For the shortcomings existing in the present κ-ε turbulent models for resolving the turbulent natural convection heat transfer, connecting the characteristics of high Reynolds number κ-ε turbulent model (needs wall function) and low Reynolds number κ-ε turbulent model (sufficient grids are employed near the walls to enable integration up to the walls), the turbulent Prandtl number is redefined and a revised κ-ε turbulent model is put forward in this paper. And the revised κ-ε turbulent model is adopted to analyze the turbulent natural convection heat transfer in an enclosure. The results indicate that the average Nusselt numbers on the vertical walls obtained by the revised κ-ε model at 108≤Ra≤1014 are in better agreement with the experimental results than the numerical results of other references, the relative error from the revised κ-ε model is within 8% comparing with the experimental results. The local Nusselt numbers on the vertical walls obtained by the revised κ-ε model are in good agreement with the experimental results. The above analysis means that the revised κ-ε model is suitable to resolve the turbulent natural convection heat transfer in enclosure. Comparing with other turbulent models, the revised κ-ε model of this paper can more accurately describe the relationship between the boundary development and wall heat transfer characteristics in enclosure.


Zhou W.,Lanzhou Jiaotong University | Wang L.,Key Laboratory of Railway Vehicle Thermal Engineering
Proceedings - International Conference on Computer Distributed Control and Intelligent Environmental Monitoring, CDCIEM 2011 | Year: 2011

Water mass balance is the necessary requirement of a numerical model of PEM fuel cell. Available model cannot enforce the water mass balance at the condition that one component is consumed in fully humidified gas such as in catalyst layer of PEMFC. The reason is that the couple between the equations solved is too weak. To enforce the water mass balance at the condition above mentioned, this paper provides a new model to describe the water transfer between two phases in catalyst layer of PEM fuel cell. © 2011 IEEE.

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