【作者】 毛佳妮；

【导师】 陈焕新；

【作者基本信息】 华中科技大学 ， 供热、供燃气、通风与空调工程， 2013， 博士

【摘要】 随着大规模通信设备和和数据处理器的封装微型化及接触界面高热流密度发展趋势，以界面热量传递为主的热管理问题普遍存在。热电制冷作为一项全固态主动式界面冷却技术，噪音低、结构紧凑、无制冷工质、运行经济、环境友好，正好契合了部分特殊领域的发展需求而有了新的发展契机。然而，在目前还没有高优值系数热电材料或某些新型热电材料进入实际应用的背景下，如何对现有的热电材料进行优化应用已成为具有现实意义的重要研究课题。不仅如此，国外学者开始关注采用脉冲电源驱动热电制冷系统获得瞬态过冷强化作用，但研究人员主要侧重于瞬态实现热电过冷效应的最大化(即以获得最大瞬态温差，或者最低瞬态过冷温度为目标)，却忽略了量化各参数作用的影响权重，以及在实际应用中，强化制冷效应在特征时间区域的热稳定性相关的动态特性研究。课题来源于“国家自然科学基金委员会科学部主任基金”(No.51246005)、“2012年教育部博士点基金”(No.20120142110045)、中国科学院“低温工程学重点实验室开放课题基金”（No.CRYO201121）、和“湖北省自然科学基金”（No.2011CD13288）。论文的主要工作是结合已有介绍的热-电转换机理，分别从实验研究和数值模拟的角度出发，系统讨论分析了实际热电制冷系统中多参数耦合作用下的制冷特性及其热-电转换过程，并尝试对当前新型的脉冲驱动强化瞬态热电制冷技术进行了探索性研究。首先，系统讨论了热电模块在稳态工况下的综合影响因素及其热-电转换过程中的基本工作特性。分析结果表明：选择小截面的半导体制冷器件不仅不会对器件的整体制冷性能造成不利，且有利于节省材料。在工作条件和材料确定之后，制冷量只取决于“面积/长度”的比值（G因子），并且存在最佳推荐区间为0.06cm～0.15cm，使得热电制冷器件的理论制冷量达到最佳工况。另外，以两级为例，得到级间元件总数比值在推荐范围2≤r≤4时，相比单级模块更能突出多级热电堆的制冷效果优势。其次，从实验的角度，对实际热电系统在几组变工况参数影响下的动态制冷特性进行了分析。实验结果表明：通过强化热电模块冷端热沉与冷侧介质环境之间的热交换强度，可以明显提高基于瞬态界面效应的帕尔贴制冷量在较短时间内对目标热载荷作用的制冷效果。而当热端热沉换为两相热虹吸式双环路热管，系统的制冷效率COP达到0.48，相比传统散热器结构（风扇+翅片的热沉形式）的散热性能，制冷器COP提高了78%。再者，从理论分析的角度，针对实际热电制冷系统建立了非稳态热传递能量守恒方程，并采用本征函数法和有限差分法相结合，获得了关于时间项和空间项的数值求解表达式。同时，还通过改建的PWM性能测试台，实验验证了数学模型对于突变电压作用下的制冷性能趋势预测的可行性和准确性。最后，在已建立的非稳态数学模型基础上，自定义构造了脉冲波形函数作为模型中的电压输入信号，由此建立了描述脉冲驱动模式作用的热电制冷非稳态模型。同时，还引入了3个表征动态响应特性的特征时间，系统分析了脉冲特征参数对瞬态强化热电过冷效应的作用规律，并尝试揭示了脉冲驱动作用下的瞬态热-电转换过程以及热量分配机制。具体分析得到：从输入电功的高效转化目标出发，具有单调递增趋势的脉冲电压相比单调递减趋势的脉冲电压，更能保证实现更高效的热-电转化过程。而进一步权衡脉冲波形的经济性优势，以正弦波形最值得推荐，甚至超过了常用的方波形脉冲电压驱动实现的过冷强化作用效果。为了弥补冷侧热源削弱冷端界面制冷能力的不利影响，可以采取适当延长脉冲驱动时间或者增大脉冲突变幅度，以提供热源更多的额外帕尔贴制冷量。以上分析为脉冲模式驱动热电制冷器的运行过程控制、系统及其结构的优化设计和匹配，提供较为准确的理论预测和方案比较。更多还原

【Abstract】 For the continuous miniaturization and high packaging density of large-scale telecommunications and datacenter embedded processors, the interfacial thermal management is universal. Thus, there has been a considerable resurgence of interest for the all-solid-state thermoelectric cooling technology in cooling the active regions of high heat flux. However, there has no practical application with high thermoelectric figure of merit or new thermoelectric materials at present. So, how to optimize the cooling performance with the available material is still an important task with practical significance. More than that, the pulsed thermoelectric super-cooling behavior, namely a phenomenon of a large decrease in temperature instantaneously available for the interfacial heat dissipation, gradually reveals more advantages. But, most previous work on the transient super-cooling mainly focused on the minimum supercooling temperature achievable, and ignored to clarify quantitatively the extent of the interactional effects on the enhancement of the transient supercooling performance, as well as the dynamics analysis on the characteristic time related to the system thermostability.The research was supported by National Natural Science Fund, DDSF (Grant No.51246005), the Doctoral Scientific Fund Project of the Ministry of Education of China (Grant No.20120142110045), Chinese Academy of Sciences (CAS) through Open Project Fund on the Key Laboratory of Cryogenic Engineering (Grant No. CRYO201121), and Natural Science Foundation of Hubei Province (Grant No.2011CD13288). In this work, based on the existing thermoelectric conversion mechanism, we investigated a synthetic approach on analyzing the coupling effects under various boundary and initial conditions, as well as an exploratory work for the pulsed thermoelectric supercooling technology.Firstly, after systematically analyzed the comprehensive influence factors and the essential cooling characteristics during the steady-state thermo-electric conversion process, it can be found that TE module with a small cross section will not make the deterioration of cooling performance, but save money on materials. For a fixed working condition, the cooling capacity depends only on G factor, along with the best ratio interval of0.06cm-0.15cm. Besides, TE module of2-4stages can make a satisfactory cooling capacity.Secondly, the dynamic characteristics of an actual thermoelectric cooling system were investigated experimentally. When coupled with an additional thermal load attached to Peltier junctions, the Petier cooling effect can be enhanced remarkably in a short time scale, if raising the heat transfer rate of the cold-junction heat sink. Similarly, instead of fan and fin heat sink on the hot side of TEC, there is an increase of78%in COP (namely the value of0.48) for the TEC system, due to the development of a thermosyphon with two phases to dissipate heat from the hot side.Thirdly, an unsteady heat transfer model for the actual TEC system was established. Then, combined with eigenfunction method and finite difference method, a numerical solution expression was derived with time-term and space-term. Certainly, the experiments by the PWM based performance test also verified the feasibility of this numerical method.Lastly, with the input of user-defined pulse mode function, a revised unsteady model was established, involving time-dependent imposed voltage pulse and time-dependent thermal boundary conditions on the transient supercooling behavior as well as the response of characteristic time and the pulse operation parameters during the periods of pulse start-up, pulse-on time and pulse-off time. Then, the coupling interaction of the thermoelectric effects on the amount of the availably electrical conversion was described. With the monotonically increasing pulse shape, it is more appropriate to achieve the maximum supercooling capacity. Especially for the economic evaluation, sine voltage pulse shows a greater advantage over other pulse shapes. To make up the interfacial cooling losses when coupled with an additional thermal load, the appropriate increase of pulse time or pulse amplitude can contribute to the full use of the electrical conversion. From this work, it can be served as a theoretical basis to guide the process control and system optimization for a thermoelectric cooling system driven by pulse modes in future.更多还原