中文摘要：

为探究结构表面（如凹穴）对换热设备螺旋和直细通道内流体流动和传热影响的差异,在这2种通道的两侧面加入扇形凹穴,并采用数值方法研究其在不同雷诺数下流动、传热、熵产以及综合性能的影响。结果表明：凹穴对螺旋细通道内流体的流动影响明显,摩阻系数最大提高23%,而对传热和综合性能几乎没有影响;低雷诺数时凹穴对直细通道内流体的流动、传热和综合性能的影响不明显,而高雷诺数时影响显著,摩阻系数和努塞尔数最大分别提高50%和45%,最大传热强化因子达1.27;凹穴可减少螺旋和直细通道内流体流动和传热过程的熵产,但在高雷诺数时才比较明显地减少,且对直细通道的影响大于螺旋细通道,熵产增大数的最小值分别为0.34和0.73。研究结果可为微细通道换热设备的性能改善提供参考。

英文摘要：

With the rapid development of microminiaturization technology and the urgent requirements of industrial field,the sizes of many devices are reduced continually.This causes the thermal load to increase sharply when the device is working,and further leads to the decreasing of the working stability gradually.So the conventional heat exchanger can＇t meet the heat transfer requirement for these micro-devices.Thus,the micro/mini-channel heat exchanger emerges as the times require.This exchanger has many advantages,such as compact structure,high efficiency for heat dissipation,low power consumption and few coolant requirements.These advantages motivate many researchers to conduct numerous studies on the micro/mini-channel heat exchanger continuously to further enhance heat transfer performance.Adding cavities,fins or ribs on the wall of the channel is a solution for enhancing heat transfer performance in the micro/mini-channel heat exchanger.As we know,the helical and straight channels are widely applied to the heat exchanger.The difference between both channels is the existence of secondary flow in former,inducing heat transfer enhancement.Therefore,it is important to understand the effects of cavities or fins on the fluid flow and heat transfer enhancement in the helical and straight micro/mini-channel heat exchangers.As a consequence,the cavities are added on the both sidewalls of helical and straight mini-channels in this work,and the effects of the cavities on the fluid flow and heat transfer in the helical and straight mini-channels are studied using numerical simulation method.Specifically,the comparative analysis in the effects of cavities on the flow,heat transfer,entropy generation and overall performance in the helical and straight mini-channels is performed based on the first and second thermodynamics law.This aims to analyze the different effects of cavities on both mini-channels.The cross-sections for both mini-channels are the same,and the width and height of this cross-section are 3 and 3 mm,respective