發(fā)布時間：2018-03-25 08:21

  本文選題：平行流蒸發(fā)器　切入點：孔徑　出處：《天津商業(yè)大學》2014年碩士論文

【摘要】：平行流蒸發(fā)器由于具有很好的換熱物性，所以受到廣泛的關注。但目前用在低溫下的平行流蒸發(fā)器較少，且流場溫度均勻性較差。本文采用數(shù)值模擬的方法，研究了在相同R134a制冷劑充注量下，8根與10根管內徑為0.4cm的平行蒸發(fā)管內制冷劑溫度場均勻時的孔徑大小；同時研究了在孔徑大小不變時，調整進口制冷劑流量和平行蒸發(fā)管的管間距后溫度場的變化情況，調整平行蒸發(fā)管的管間距后溫度場的變化情況；同時與蒸發(fā)面積、管間距、制冷劑充注量相等的蛇形管蒸發(fā)器溫度場進行對比研究。在實驗方面，加工平行流蒸發(fā)器，對模擬得出的孔徑大小進行驗證。通過研究發(fā)現(xiàn)： 1.當平行流蒸發(fā)器進口速度為V=0.01m/s時，靠近平行流蒸發(fā)器進口越近的蒸發(fā)管制冷劑量越大；當蒸發(fā)器進口速度為V=0.1m/s時，靠近平行流蒸發(fā)器進口越近的蒸發(fā)管內制冷劑量越小。 2.當平行流蒸發(fā)器的管根數(shù)為8根、進口速度為V=0.04m/s時，在降溫階段，平行蒸發(fā)管的管間距在5cm時的降溫曲線較分散；平行蒸發(fā)管的管間距在3cm時的溫度變化較小，8根蒸發(fā)管間的降溫曲線較集中。 3.當進口速度V=0.04m/s時，蛇形管蒸發(fā)器和平行流蒸發(fā)器的降溫速率相近，當系統(tǒng)穩(wěn)定后，，由于壓降的作用，蛇形管蒸發(fā)器蒸發(fā)管之間的溫度相差較大，且蛇形管蒸發(fā)器的溫度隨著制冷劑的流向越來越低。 4.根據(jù)模擬孔徑大小，并根據(jù)實驗數(shù)據(jù)適當?shù)恼{整孔徑大小后，在三組實驗中均未發(fā)現(xiàn)10根蒸發(fā)管的平行流蒸發(fā)器具有較均勻的溫度場，根據(jù)10根蒸發(fā)管的測量數(shù)據(jù)分析并調整8根蒸發(fā)管的模擬孔徑大小，實驗結果測得8根蒸發(fā)管的溫度場較均勻。 5.平行流蒸發(fā)器集管與蒸發(fā)管處的孔徑較小，使得孔徑處制冷劑產生節(jié)流，并且制冷劑液體在平行蒸發(fā)管內的節(jié)流降溫與氣體吸熱升溫的差值相差不大，使得蒸發(fā)器的蒸發(fā)溫度維持在穩(wěn)定狀態(tài)，溫度場較好。 6.在相同的工況下，平行流蒸發(fā)器模擬值的降溫速率高于實驗值的降溫速率，在初始降溫階段，兩曲線降溫的吻合度較好，都呈現(xiàn)出豎直下降的趨勢，在下降到6℃左右時，實驗溫度曲線下降速度放緩，模擬溫度曲線的降溫速率不變，并且模擬溫度值在100s后達到穩(wěn)定狀態(tài)。由于制冷系統(tǒng)和外界因素的影響，實驗溫度值的整體下降趨勢較緩慢，在800s后穩(wěn)定并和模擬溫度值吻合。
[Abstract]:The parallel flow evaporator has attracted wide attention because of its good heat transfer properties. However, there are few parallel evaporators used at low temperature, and the temperature uniformity of the flow field is poor. In this paper, the numerical simulation method is used. The pore size of 8 parallel evaporative tubes with 0.4cm inner diameter of 10 tubes under the same charge of R134a refrigerant has been studied, and the pore size of the refrigerant in parallel evaporative tubes with constant pore size has been studied. The change of temperature field after adjusting the inlet refrigerant flow rate and the tube spacing of the parallel evaporator tube, and the change of the temperature field after adjusting the tube spacing of the parallel evaporative tube, at the same time, The temperature field of the serpentine tube evaporator with equal refrigerant charge was compared. In the experiment, the size of the pore diameter obtained by the simulation was verified by processing the parallel flow evaporator. 1. When the inlet velocity of parallel evaporator is V=0.01m/s, the quantity of refrigerant in the evaporator near the inlet of parallel evaporator is larger, and when the inlet velocity of evaporator is V=0.1m/s, the refrigerant quantity in the evaporator pipe which is closer to the inlet of parallel evaporator is smaller. 2. When the number of tubes in parallel evaporator is 8, and the inlet velocity is V=0.04m/s, the cooling curve of parallel evaporator in 5cm is scattered in the cooling stage. The temperature change of the parallel evaporator tube at 3cm is smaller than that between the eight evaporator tubes. 3. When the inlet velocity is V=0.04m/s, the cooling rate of the serpentine tube evaporator and the parallel flow evaporator is similar. When the system is stabilized, the temperature difference between the serpentine tube evaporator and the parallel flow evaporator is larger because of the effect of pressure drop. The temperature of serpentine tube evaporator is lower and lower with the flow of refrigerant. 4. According to the size of simulated aperture and the appropriate adjustment of aperture size according to experimental data, the temperature field of parallel flow evaporator of 10 evaporators has not been found in three groups of experiments. According to the measured data of 10 evaporative tubes, the simulated aperture of 8 evaporators is analyzed and adjusted. The experimental results show that the temperature field of 8 evaporators is uniform. 5. The aperture of the collector tube and the evaporation tube of parallel flow evaporator is small, which makes the refrigerant throttling at the aperture, and the difference between the throttling cooling of refrigerant liquid in parallel evaporator tube and gas endothermic heating is not obvious. The evaporation temperature of evaporator is maintained in a stable state, and the temperature field is better. 6. Under the same working condition, the cooling rate of the simulated value of parallel flow evaporator is higher than that of the experimental value. In the initial cooling stage, the coincidence between the two curves is good, and both curves show a vertical downward trend, and when the temperature drops to about 6 鈩

本文編號：1662294