Abstract:The principle of heat transfer enhancement in the core flow of a tube has been proposed, in this paper, to make fluid temperature uniform in the core region of a tube and decrease flow resistance, which is different from heat transfer enhancement in the boundary flow of a tube. Two new models, representing heat transfer enhancement in the laminar and turbulent tube flow, have been established and numerically analyzed. Theoretical and numerical results indicate that heat transfer enhanced components designed according to the principle proposed in this paper will be benefit for increasing convective heat transfer coefficient, reducing flow resistance and raising the PEC value of a heat transfer enhanced tube. The presented principle, therefore, may help developing new type of heat transfer unit and designing heat exchanger with high heat transfer coefficient and low flow resistance.
Proton exchange membrane fuel cell (PEMFC) has the advantages of high energy efficiency, clean, pollution-free, fast start-up and noise-free, but its thermal management problems still restrict the development and practical application of PEMFC. This paper analyzes the important influence of heat management on the working performance of proton exchange membrane fuel cell, and summarizes the structure principle and effect evaluation of thermal management system using heat pipe under the premise of simply summarizing the shortcomings of the thermal management system using conventional cooling method. By expounding the working principle and characteristics of pulsating heat pipe, and from the perspective of PEMFC internal structure and technology, the feasibility of applying pulsating heat pipe to PEMFC thermal management system is analyzed, with a view to developing pulsating heat pipe-type PEMFC thermal management technology with compact structure and excellent performance.
At present, LED lighting is gradually replacing the traditional lighting and becoming the fourth generation of light source. In the process of LED lighting, a large part of electric energy is converted into heat energy. If it can not dissipate heat in time, the device efficiency will be reduced or even damaged. Therefore, the heat dissipation problem of LED needs to be solved. By testing and recording the working temperature of the existing LED lighting radiator in different positions, the performance of the radiator was compared and tested. The experiment shows that the radiator works best when the light source is downward, and the temperature difference between the top and the bottom of the radiator is the smallest in this case, and the temperature at the top of the radiator is higher than that at the bottom in the working process. When the position of the LED lighting radiator changes, the heat dissipation performance of the top and bottom of the radiator changes.
Proton exchange membrane fuel cell (PEMFC) has the advantages of high energy efficiency, clean, pollution-free, fast start-up and noise-free, but its thermal management problems still restrict the development and practical application of PEMFC. This paper analyzes the important influence of heat management on the working performance of proton exchange membrane fuel cell, and summarizes the structure principle and effect evaluation of thermal management system using heat pipe under the premise of simply summarizing the shortcomings of the thermal management system using conventional cooling method. By expounding the working principle and characteristics of pulsating heat pipe, and from the perspective of PEMFC internal structure and technology, the feasibility of applying pulsating heat pipe to PEMFC thermal management system is analyzed, with a view to developing pulsating heat pipe-type PEMFC thermal management technology with compact structure and excellent performance.
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