Jyh-tong Teng

Evaluation of the Combustion Efficiency and Emission of Pollutants by Coal Particles in a Vortexing Fluidized Bed

Abstract Experiments were carried out in a pilot-scale (a0.45 m i.d.) vortexing fluidized bed combustor (VFBC), with coal particles as the fuel, limestone as sorbent, and river sand as the fluidizing medium. The effects of various operating parameters on the combustion efficiency and the pollutants emitted were investigated. Different formulae for the combustion efficiency are compared. A combustion efficiency of 96% can be easily obtained in a VFBC. Both the NO x and SO x emissions, based on an oxygen content of 6 vol.% in the flue gas, are found to be below 100 ppm. The retention of sulfur by limestone displays a maximum temperature in the bed at 850–880°C.

A Study on the Simulations of a Trapezoidal Shaped Micro Heat Exchanger

Micro heat exchangers are employed to heat or cool in cooling electronic devices, automobiles, chemical engineering and commercial and residential heating/cooling. A trapezoidal shaped micro heat exchanger was simulated to carry out fluid flow and heat transfer characteristics. These approaches are compared with the traditional method which the results are the same. For this study, the Reynolds numbers get from 0 to 165.7 which is laminar flow. The minimal Reynolds number is zero that occurs at the edge of channels where the velocity is zero, the maximal Reynolds number occurs at the inlet manifold where the temperature and velocity term are maximum. A total heat flux of 13.6 W/cm^2 could be achieved from this heat exchanger for water with the inlet temperature of 80℃ and flow rate of 0.1158 g/s.

Investigation of the Flow Mal-Distribution in Microchannels

This study examines the mal-distribution problem in microchannel manifolds. The tubes are of triangular shape with hydraulic diameter of 25 and 50 μm. Ranges of the Reynolds number are from 0.1 to 9. The test results indicate that the mal-distribution decreases with the rise of flow rate. For an inlet flow rate of 0.1 mL/min at the distributor inlet, the maximum difference of the translational velocity among manifolds is about 45%. The difference is reduced to 33% if the flow rate is increased to 0.153 mL/min. The maximum translational velocity inside the manifolds is located at the edge of the manifolds and the center portion has the smallest translational velocity. This is because of the spread and turn around water that helps to contribute the increase of flow rate nearby the edge.Copyright

Single-Phase Heat Transfer and Fluid Flow Phenomena of Microchannel Heat Exchangers

Thanhtrung Dang1, Jyh-tong Teng2, Jiann-cherng Chu2, Tingting Xu3, Suyi Huang3, Shiping Jin3 and Jieqing Zheng4 1Department of Heat and Refrigeration Technology, Hochiminh City University of Technical Education,Hochiminh City, 2Department of Mechanical Engineering, Chung Yuan Christian University, Chung-Li, 3School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan, 4College of Mechanical Engineering, Jimei University, Xiamen, Fujian, 1Vietnam 2Taiwan 3,4P. R. China

Numerical Simulation of a Microchannel Heat Exchanger Using Steady-State and Time-Dependent Solvers

Microchannel heat exchangers are employed for thermal management of electronic devices, IC circuits, etc. Simulation of microchannel heat exchangers using solver with the capability of dealing with steady-state and time-dependent conditions is carried out. The solver — COMSOL — was developed by COMSOL Multiphysics, Inc. using the finite element method. The pressure drop and heat transfer are two of the most important parameters in these devices. In this study, the results obtained from the numerical analyses were in good agreement with those obtained from the papers. In addition, using the same heat exchanger configuration, results obtained from numerical simulations of pressure drop and overall thermal resistance using the COMSOL indicated that those parameters are lower for the cases with parallel-flow than those with the counter-flow.Copyright