本文選題：翅片管蒸發(fā)器 + 結霜工況　； 參考：《河南科技大學》2014年碩士論文

【摘要】：在低溫制冷系統(tǒng)中，翅片管蒸發(fā)器表面結霜現(xiàn)象很常見，霜的產(chǎn)生一方面增加了熱阻，另一方面減少了空氣流通面積，導致蒸發(fā)器的換熱性能惡化。尤其是在低溫高濕環(huán)境下，蒸發(fā)器的結霜將直接影響蒸發(fā)器乃至整個系統(tǒng)的安全與穩(wěn)定運行，所以對蒸發(fā)器結霜工況動態(tài)性能的實驗和模擬研究就顯得尤為重要。 本文利用包括一個封閉的帶加熱，加濕、風速控制的風道循環(huán)系統(tǒng)和蒸汽壓縮式制冷系統(tǒng)的換熱器低溫結霜工況性能實驗系統(tǒng)，測試在不同的的入口空氣溫度、濕度、流速等環(huán)境參數(shù)下，翅片管式蒸發(fā)器低溫結霜工況的結霜量，制冷量，COP、進出口空氣側壓降和能量傳遞系數(shù)的變化以及制冷量、COP、空氣側壓降等隨霜層增長的變化情況，分析環(huán)境參數(shù)對翅片管蒸發(fā)器性能的影響，，并對蒸發(fā)器試件不同工況下的融霜時機進行了定量分析。 建立了結霜工況下翅片管蒸發(fā)器空氣側流動和換熱的分布參數(shù)仿真模型，模型考慮了在氣流方向上蒸發(fā)器結構、霜層厚度以及濕空氣狀態(tài)等參數(shù)沿程變化的影響。編制了適用于不同空氣流態(tài)和蒸發(fā)器結構的翅片管蒸發(fā)器動態(tài)結霜過程模擬計算程序，對蒸發(fā)器的結霜量、制冷量、能量傳遞系數(shù)和進出口空氣側壓降等性能參數(shù)進行計算，并通過對比分析實驗結果和模擬計算結果發(fā)現(xiàn)，在6小時的結霜過程中，實驗值和模擬計算值的誤差最大值在14%以內(nèi)，兩者間吻合較好，證明了所建立的分布參數(shù)模型的準確性，并可用模型進行結霜工況下翅片管蒸發(fā)器性能的正確預測和優(yōu)化分析。在此基礎上，進一步分析蒸發(fā)器的結構參數(shù)對蒸發(fā)器性能的影響和霜層密度和厚度的變化規(guī)律，并對如何抑制結霜，提高蒸發(fā)器的綜合換熱性能進行了分析，提出了4點改進建議。 對翅片管蒸發(fā)器低溫結霜工況性能研究，為環(huán)境參數(shù)優(yōu)化、蒸發(fā)器結構設計改進和融霜周期的確定提供了重要的實驗依據(jù)和設計參考。
[Abstract]:Frosting on the surface of finned tube evaporator is very common in low temperature refrigeration system. On the one hand, the formation of frost increases the thermal resistance, on the other hand, it reduces the air circulation area, which leads to the deterioration of heat transfer performance of evaporator. Especially in the low temperature and high humidity environment, the frosting of evaporator will directly affect the safe and stable operation of evaporator and even the whole system, so the experimental and simulation study on the dynamic performance of evaporator frosting condition is particularly important. In this paper, an experimental system for the performance of heat exchangers under low temperature frosting conditions including a closed air channel circulation system with heating, humidification, wind speed control and steam compression refrigeration system is used to test the air temperature and humidity at different inlet. Under the environmental parameters such as flow rate, the frosting rate, the refrigerating capacity of the finned tube evaporator under the condition of low temperature frosting, the change of the inlet and outlet air pressure drop and the energy transfer coefficient, and the variation of the refrigerating capacity and the air side pressure drop with the increase of the frost layer, The influence of environmental parameters on the performance of finned tube evaporator was analyzed. The simulation model of air side flow and heat transfer parameters of finned tube evaporator under frosting condition is established. The influence of evaporator structure, frost thickness and wet air state along the flow direction is considered in the model. A simulation program for dynamic frosting process of finned tube evaporator with different air flow states and evaporator structures has been developed. The performance parameters of evaporator, such as frosting amount, refrigerating capacity, energy transfer coefficient and inlet and outlet air side pressure drop, have been calculated. By comparing and analyzing the experimental results and the simulation results, it is found that the maximum error between the experimental values and the simulated ones is within 14% during the frosting process of 6 hours, which is in good agreement with each other. The veracity of the established distributed parameter model is proved, and the model can be used to predict and optimize the performance of finned tube evaporator under frosting condition. On this basis, the influence of evaporator structure parameters on evaporator performance and the variation of frost density and thickness are further analyzed, and how to restrain frosting and improve the comprehensive heat transfer performance of evaporator is analyzed. Four suggestions for improvement are put forward. The research on the performance of finned tube evaporator under low temperature frosting condition provides an important experimental basis and design reference for the optimization of environmental parameters, the improvement of evaporator structure design and the determination of frost melting cycle.
【學位授予單位】：河南科技大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TB657

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