基于热开关控制下的的室温电卡制冷模型的研究
发布时间：2018-11-02 08:48
【摘要】：制冷技术的应用已经渗透到人类社会生产生活的方方面面,目前占据传统制冷模式主流的仍然是以压缩机、冷凝器、膨胀阀和蒸发器为主要结构的压缩气体工质制冷模式。该模式存在制冷效率低下和制冷工质对环境有害两个明显缺陷,不符合现代科技社会的节能和环保趋势。电卡效应制冷是一种利用铁电材料的电卡效应的新型制冷方式,其原理为对电卡材料施加电场,材料温度上升;撤去电场,则材料温度下降。电卡效应制冷具有制冷效率高、无环境污染、易于小型化、稳定可靠等特点,具备取代蒸汽压缩式制冷的潜力。由于早期电卡材料的绝热温变数值较低,严重制约了电卡制冷技术的应用发展。随着近年来宾夕法尼亚大学的章启明教授领导的课题组发现高聚物聚(偏氟乙烯-三氟乙烯)材料的电场热效应温变接近20K,引发了对电卡材料研究的新一轮热潮。此重大突破为电卡效应的研究开启了新的篇章,为电卡效应制冷的实际应用奠定了基础。与电卡材料的研究形成对比的是,学术界对电卡效应制冷系统结构的研究仍处于起始阶段,因而对新型电卡制冷模型的研究以跟进电卡材料的研究进展,促进电卡制冷的实际应用是非常有必要的。本文中作者基于章启明教授发现的高温变电卡材料,设计了一种基于热开关传热的新型电卡效应制冷模型,该模型由电卡材料与热开关交替平行排列构成。热开关要求通状态的热导远大于断状态的热导,由外部控制热开关的通断以实现热量的单向传递,热开关的应用可以有效加强传热效率及速度。相邻的电卡材料在制冷半周期内处于相反的电场状态-极化/非极化,以产生温度差进行传热,每半周期状态交换,实现热量由冷端向热端的传递。作者通过数值模拟计算了该模型的制冷性能表现,计算结果在制冷效率和制冷功率方面均表现出对蒸汽压缩式制冷的巨大优势。同时,作者还计算了该电卡制冷模型的制冷性能表现对系统设定参数的响应情况,得出了相应的结果并进行了理论分析。涉及到的参数包括制冷系统的温跨、电卡材料的温变性能及数量、热开关的热导,计算结果表明系统的制冷性能与上述参数均有密切关系并呈现规律性变化,相关结论可应用于实际应用中的设计优化。最后,作者提出了一种可应用于文中制冷模型的机械式热开关结构,热开关使用液态金属作为传热媒介,利用液态金属的表面张力维持接触,初步实验证明了其可行性。
[Abstract]:The application of refrigeration technology has penetrated into all aspects of human society production and life. At present, the compression gas refrigerant refrigeration mode with compressor, condenser, expansion valve and evaporator as the main structure still occupies the mainstream of traditional refrigeration mode. This model has two obvious defects, that is, low refrigeration efficiency and harmful refrigerant to the environment, which does not accord with the trend of energy saving and environmental protection in modern science and technology society. The electric card effect refrigeration is a new type of refrigeration method which utilizes the electric card effect of ferroelectric material. Its principle is that the electric field is applied to the electric card material, the material temperature rises, and the material temperature drops when the electric field is removed. Electric card effect refrigeration has the characteristics of high refrigeration efficiency, no environmental pollution, easy miniaturization, stability and reliability, and has the potential to replace steam compression refrigeration. Due to the low adiabatic temperature variable of early electric card materials, the application of card refrigeration technology is seriously restricted. In recent years, the research group led by Professor Zhang Qiming of the University of Pennsylvania found that the temperature change of electric field thermal effect of polymer (vinylidene fluoride trifluoroethylene) was close to 20K, which triggered a new wave of research on electric card materials. This breakthrough opens a new chapter for the study of the electric card effect and lays a foundation for the practical application of the electric card effect refrigeration. In contrast to the study of electric card materials, the academic research on the structure of electric card effect refrigeration system is still in the initial stage, so the study of new electric card refrigeration model is to follow up the research progress of electric card material. It is necessary to promote the practical application of electric card refrigeration. Based on the high temperature transformer card material discovered by Professor Zhang Qiming, this paper designs a new type of electric card effect refrigeration model based on heat transfer of heat switch, which is composed of alternating parallel arrangement of electric card material and hot switch. The thermal switch requires that the thermal conductivity of the on-state is far greater than that of the off-state. The external control of the on-off of the thermal switch is used to realize the one-way heat transfer. The application of the thermal switch can effectively enhance the heat transfer efficiency and speed. The adjacent electric-card materials are in the opposite electric field state-polarization / non-polarization in the refrigeration half-cycle to generate temperature difference to conduct heat transfer. Each half-cycle state is exchanged to realize the transfer of heat from the cold end to the hot end. The performance of the model is calculated by numerical simulation. The results show a great advantage to the steam compression refrigeration in terms of refrigeration efficiency and refrigeration power. At the same time, the response of the refrigeration performance of the electric card refrigeration model to the set parameters of the system is calculated, and the corresponding results are obtained and the theoretical analysis is carried out. The parameters involved include the temperature span of the refrigeration system, the temperature variation performance and quantity of the electric card material, the thermal conductivity of the thermal switch. The calculation results show that the refrigeration performance of the system is closely related to the above parameters and presents regular changes. The relevant conclusions can be applied to design optimization in practical application. Finally, the author proposes a mechanical heat switch structure which can be applied to the refrigeration model in this paper. The hot switch uses liquid metal as heat transfer medium and maintains contact with surface tension of liquid metal. The preliminary experiment proves its feasibility.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB61
，
本文编号：2305529
[Abstract]:The application of refrigeration technology has penetrated into all aspects of human society production and life. At present, the compression gas refrigerant refrigeration mode with compressor, condenser, expansion valve and evaporator as the main structure still occupies the mainstream of traditional refrigeration mode. This model has two obvious defects, that is, low refrigeration efficiency and harmful refrigerant to the environment, which does not accord with the trend of energy saving and environmental protection in modern science and technology society. The electric card effect refrigeration is a new type of refrigeration method which utilizes the electric card effect of ferroelectric material. Its principle is that the electric field is applied to the electric card material, the material temperature rises, and the material temperature drops when the electric field is removed. Electric card effect refrigeration has the characteristics of high refrigeration efficiency, no environmental pollution, easy miniaturization, stability and reliability, and has the potential to replace steam compression refrigeration. Due to the low adiabatic temperature variable of early electric card materials, the application of card refrigeration technology is seriously restricted. In recent years, the research group led by Professor Zhang Qiming of the University of Pennsylvania found that the temperature change of electric field thermal effect of polymer (vinylidene fluoride trifluoroethylene) was close to 20K, which triggered a new wave of research on electric card materials. This breakthrough opens a new chapter for the study of the electric card effect and lays a foundation for the practical application of the electric card effect refrigeration. In contrast to the study of electric card materials, the academic research on the structure of electric card effect refrigeration system is still in the initial stage, so the study of new electric card refrigeration model is to follow up the research progress of electric card material. It is necessary to promote the practical application of electric card refrigeration. Based on the high temperature transformer card material discovered by Professor Zhang Qiming, this paper designs a new type of electric card effect refrigeration model based on heat transfer of heat switch, which is composed of alternating parallel arrangement of electric card material and hot switch. The thermal switch requires that the thermal conductivity of the on-state is far greater than that of the off-state. The external control of the on-off of the thermal switch is used to realize the one-way heat transfer. The application of the thermal switch can effectively enhance the heat transfer efficiency and speed. The adjacent electric-card materials are in the opposite electric field state-polarization / non-polarization in the refrigeration half-cycle to generate temperature difference to conduct heat transfer. Each half-cycle state is exchanged to realize the transfer of heat from the cold end to the hot end. The performance of the model is calculated by numerical simulation. The results show a great advantage to the steam compression refrigeration in terms of refrigeration efficiency and refrigeration power. At the same time, the response of the refrigeration performance of the electric card refrigeration model to the set parameters of the system is calculated, and the corresponding results are obtained and the theoretical analysis is carried out. The parameters involved include the temperature span of the refrigeration system, the temperature variation performance and quantity of the electric card material, the thermal conductivity of the thermal switch. The calculation results show that the refrigeration performance of the system is closely related to the above parameters and presents regular changes. The relevant conclusions can be applied to design optimization in practical application. Finally, the author proposes a mechanical heat switch structure which can be applied to the refrigeration model in this paper. The hot switch uses liquid metal as heat transfer medium and maintains contact with surface tension of liquid metal. The preliminary experiment proves its feasibility.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB61
，
本文编号：2305529
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