【摘要】：制冷技術(shù)的應(yīng)用已經(jīng)滲透到人類社會生產(chǎn)生活的方方面面,目前占據(jù)傳統(tǒng)制冷模式主流的仍然是以壓縮機、冷凝器、膨脹閥和蒸發(fā)器為主要結(jié)構(gòu)的壓縮氣體工質(zhì)制冷模式。該模式存在制冷效率低下和制冷工質(zhì)對環(huán)境有害兩個明顯缺陷,不符合現(xiàn)代科技社會的節(jié)能和環(huán)保趨勢。電卡效應(yīng)制冷是一種利用鐵電材料的電卡效應(yīng)的新型制冷方式,其原理為對電卡材料施加電場,材料溫度上升;撤去電場,則材料溫度下降。電卡效應(yīng)制冷具有制冷效率高、無環(huán)境污染、易于小型化、穩(wěn)定可靠等特點,具備取代蒸汽壓縮式制冷的潛力。由于早期電卡材料的絕熱溫變數(shù)值較低,嚴重制約了電卡制冷技術(shù)的應(yīng)用發(fā)展。隨著近年來賓夕法尼亞大學(xué)的章啟明教授領(lǐng)導(dǎo)的課題組發(fā)現(xiàn)高聚物聚(偏氟乙烯-三氟乙烯)材料的電場熱效應(yīng)溫變接近20K,引發(fā)了對電卡材料研究的新一輪熱潮。此重大突破為電卡效應(yīng)的研究開啟了新的篇章,為電卡效應(yīng)制冷的實際應(yīng)用奠定了基礎(chǔ)。與電卡材料的研究形成對比的是,學(xué)術(shù)界對電卡效應(yīng)制冷系統(tǒng)結(jié)構(gòu)的研究仍處于起始階段,因而對新型電卡制冷模型的研究以跟進電卡材料的研究進展,促進電卡制冷的實際應(yīng)用是非常有必要的。本文中作者基于章啟明教授發(fā)現(xiàn)的高溫變電卡材料,設(shè)計了一種基于熱開關(guān)傳熱的新型電卡效應(yīng)制冷模型,該模型由電卡材料與熱開關(guān)交替平行排列構(gòu)成。熱開關(guān)要求通狀態(tài)的熱導(dǎo)遠大于斷狀態(tài)的熱導(dǎo),由外部控制熱開關(guān)的通斷以實現(xiàn)熱量的單向傳遞,熱開關(guān)的應(yīng)用可以有效加強傳熱效率及速度。相鄰的電卡材料在制冷半周期內(nèi)處于相反的電場狀態(tài)-極化/非極化,以產(chǎn)生溫度差進行傳熱,每半周期狀態(tài)交換,實現(xiàn)熱量由冷端向熱端的傳遞。作者通過數(shù)值模擬計算了該模型的制冷性能表現(xiàn),計算結(jié)果在制冷效率和制冷功率方面均表現(xiàn)出對蒸汽壓縮式制冷的巨大優(yōu)勢。同時,作者還計算了該電卡制冷模型的制冷性能表現(xiàn)對系統(tǒng)設(shè)定參數(shù)的響應(yīng)情況,得出了相應(yīng)的結(jié)果并進行了理論分析。涉及到的參數(shù)包括制冷系統(tǒng)的溫跨、電卡材料的溫變性能及數(shù)量、熱開關(guān)的熱導(dǎo),計算結(jié)果表明系統(tǒng)的制冷性能與上述參數(shù)均有密切關(guān)系并呈現(xiàn)規(guī)律性變化,相關(guān)結(jié)論可應(yīng)用于實際應(yīng)用中的設(shè)計優(yōu)化。最后,作者提出了一種可應(yīng)用于文中制冷模型的機械式熱開關(guān)結(jié)構(gòu),熱開關(guān)使用液態(tài)金屬作為傳熱媒介,利用液態(tài)金屬的表面張力維持接觸,初步實驗證明了其可行性。
[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.
【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TB61
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本文編號：2305529