CAJ | 학술논문

为了研究蒸发式冷凝器喷嘴工作时性能变化情况，该文建立了喷嘴喷淋二维模型，利用计算流体力学计算软件对2种不同喷嘴出水口的喷淋效果进行了模拟，在测试平台上对喷嘴实际喷水效果进行了现场测试，并对其喷嘴结构和布置方式提出改进方案。试验及模拟结果显示：在满足蒸发式冷凝器最小喷淋量的前提下，喷嘴喷水出口处，由于流体运动轨迹发生变化，出口处动压存在不规则分布，喷嘴2局部动压明显高于喷嘴1，动压的不规则分布会直接影响出口处的速度分布情况。在2m/s进水速度下，冷凝器内腔2种类型喷嘴喷水出口处动压分别为6000和13000 Pa，出口处局部最大速度达到3和5 m/s。在模拟中发现，与喷嘴1相比，喷嘴2外部流场静压更加均匀合理，拥有更大的流体出口动压，喷淋面积较大，流体迹线也简单明了，喷嘴2分流槽设计能够提高喷嘴的喷淋效果。在今后设计中，喷嘴1可以通过增设第二层分流平台，来提高内部喷淋水流场均匀性；喷嘴2在原来底座上增加分流槽，增大底座直径，可使喷淋水花更加均匀，增强了盘管液体薄膜传热特性，提高了换热效果。
위료연구증발식냉응기분취공작시성능변화정황，해문건립료분취분림이유모형，이용계산류체역학계산연건대2충불동분취출수구적분림효과진행료모의，재측시평태상대분취실제분수효과진행료현장측시，병대기분취결구화포치방식제출개진방안。시험급모의결과현시：재만족증발식냉응기최소분림량적전제하，분취분수출구처，유우류체운동궤적발생변화，출구처동압존재불규칙분포，분취2국부동압명현고우분취1，동압적불규칙분포회직접영향출구처적속도분포정황。재2m/s진수속도하，냉응기내강2충류형분취분수출구처동압분별위6000화13000 Pa，출구처국부최대속도체도3화5 m/s。재모의중발현，여분취1상비，분취2외부류장정압경가균균합리，옹유경대적류체출구동압，분림면적교대，류체적선야간단명료，분취2분류조설계능구제고분취적분림효과。재금후설계중，분취1가이통과증설제이층분류평태，래제고내부분림수류장균균성；분취2재원래저좌상증가분류조，증대저좌직경，가사분림수화경가균균，증강료반관액체박막전열특성，제고료환열효과。
In the evaporative condenser, the heat transfer performance was directly influenced by the spraying effect. When the evaporative condenser is in its working state, the cooling water passed through the top spray nozzle, and sprayed uniformly on the outside surface of condenser tubes, and formed a layer of water film. The low temperature water film took away a large amount of heat, the high temperature refrigerant vapor inside the tubes was cooled, and the purpose of the cooling fluid was achieved. In this paper, the spraying effects of two types of nozzles were simulated by CFD numerical calculation software, the real spraying effect was tested on a test platform, and the structure and layout of nozzles were improved at last. In order to get the spraying effect difference of the two types of spray nozzles, the pressure field and velocity field changes were analyzed when the spray nozzles were in different working states. The experimental and simulation results showed that the outer dynamic pressure field of each spray nozzle was irregularly distributed, which was caused by the change of the fluid motion trajectory under the minimum spraying amount. The local dynamic pressure of nozzle two was significantly higher than that of nozzle one. The outer velocity field distribution was directly influenced by the irregular distribution of the dynamic pressure field. The outer dynamic pressure of the two types of spray nozzles were 6000Pa and 13000Pa, and the outer local maximum velocity had reached 3m/s and 5m/s with the water inlet at the velocity of 2m/s. In the simulation, the outer dynamic pressure of nozzle two was always greater than that of nozzle one. The ratio of local dynamic pressure between the two types of spray nozzles was 2.33 when the velocity of water inlet was set to be 3m/s. Compared with spray nozzle one, the condenser cavity static pressure distribution of spray nozzle two was more uniform and reasonable, the local dynamic pressure and spray area were much bigger, and the fluid motion trajectory was simple and clear. The spraying effect could be improved by the design of a shunt channel. At last, the real spraying effect of the two types of spray nozzles was tested on a evaporative condenser test platform. 15 spray nozzles of every type were installed on the water inlet pipeline, and the spraying effect was caught by a high pixel camera when the evaporative condenser was under stable operation state. The water spraying effect showed that spray nozzle two had a much bigger spraying angle and spraying area, and it was better to enhance the spraying effect. In the future study, the internal flow field uniformity of nozzle one can be improved by adding a two-tier shunt platform. Furthermore, the diameter of the shunt base can be increased and more shunt channels can be added on the original base of nozzle two to optimize the spraying water effect and the heat transfer efficiency of the condenser.