节点文献
机房空调中不同型式下不同夹角对翅片管蒸发器性能影响的研究
【作者】 王晓萍；
【导师】 黄虎；
【作者基本信息】 南京师范大学 ， 供热、供燃气、通风及空调工程， 2017， 硕士
【摘要】 随着IT行业在全球的迅速发展,数据中心的高能耗已经成为一个不可忽视的问题。对机房空调而言,换热器作为热量交换的一个非常重要的组件,其效率的高低直接影响到制冷系统的性能。因此,节省能源的有效途径之一就是加强换热器的合理设计和运行管理。本文主要采用商业软件FLUENT对机房空调中不同角度的正、反V型翅片管蒸发器进行数值模拟,得到了两种型式的翅片管蒸发器三种角度下(32.5° ,39° ,45.5° )外部空间的温度场、速度场和迎面风速云图,以及空气侧换热量、努塞尔数和空气侧的压降,而且从迎面风速不均匀度等方面分析了造成这种差异的原因。本文采用了焓差试验台对模拟结果进行验证。此外,本文还对不同风量和不同相对湿度的反V型翅片管蒸发器空气侧的特性进行比较,比较了三种角度在风量百分比为100%、90%、80%、70%四种工况下的换热性能,以及不同相对湿度对换热性能的影响,包括相对湿度分别为45%、50%、55%和60%的四类情况。对比分析了各种工况下的制冷量和能效比,并且从蒸发温度、压缩机的吸、排气温度和吸、排气压力以及冷凝温度等方面分析造成这种差异的原因。就所进行的各项研究,得到了如下的结论:(1)随着翅片管换热器夹角的增大,换热器空间内部的流场越来越均匀,换热面的速度分层现象也有一定的减少,高温区和低温区的区域都有所减小。空气侧努塞尔数和压降均呈现上升的趋势,且正V型式下的努塞尔数普遍低于反V型式,压降普遍高于反V型式。(2)换热器迎面速度分布呈现出相似的变化趋势,位于风机垂直正下方位置迎面风速都是最大,并以此为中心逐渐向外递减,在换热器边缘位置达到最小。反V型蒸发器夹角为32.5°、39°和45.5°对应的迎面风速不均匀度分别为0.86、0.62 和 0.56。(3)随着风量百分比的降低,三种夹角蒸发器系统的制冷量都会减小,而能效比都呈上升趋势。且不论风量百分比如何变化,夹角为39°和45.5°时,其制冷量和能效比都远高于夹角为32.5°的蒸发器,并且在风量百分比为80%和70%时,这种差异更加明显,与制冷量最高的角度相比,制冷量分别下降了5.7%和6%,能效比分别下降了 3.5%和6.7%。当风量百分比为70%时,夹角为45.5°的蒸发器系统的制冷量比夹角为39°的蒸发器系统的制冷量提高了 3.4%,能效比增加了 3%。(4)随着相对湿度的增加,三种角度蒸发器的制冷量和能效比整体上呈增加趋势。当风量百分比为80%时,夹角为32.5°的蒸发器在相对湿度从55%增加到60%时,制冷量和能效比增长速度较其他各类情况都很大。本文对机房空调中不同型式不同角度的正、反V型翅片管蒸发器进行数值模拟和实验研究,得到了上面的一些结论,具有一定的工程实用价值以及学术意义,为机房空调中的蒸发器设计与优化提供一定理论依据。
【Abstract】 With the rapid development of IT industry in the world, the high energy consumption of data center has become a problem that can not be ignored. As for the air conditioner of the engine room, the heat exchanger is a very important component of the heat exchange. The efficiency of the heat exchanger is directly related to the performance of the refrigeration system. Therefore, one of the effective ways to save energy is to strengthen the reasonable design and operation management of heat exchangers.This paper mainly uses the software FLUENT for different angles of positive and negative V type finned tube evaporator in room air conditioning for numerical simulation, obtained all kinds of cases (32.5 degrees, 39 degrees, 45.5 degrees)external space temperature field, velocity field and wind speed contour, pressure drop and heat, air side Nusselt number and air side, and from the face velocity uniformity was analyzed and the cause of the difference.In this paper, the enthalpy difference test bench is used to verify the simulation results. In addition, this paper also compares the characteristics of different volume and different relative humidity of the negative V type finned tube evaporator,compares three kinds of angle in the air flow as a percentage of the heat transfer performance of 100%, 90%, 80%, 70% and four operating conditions, and the influence of relative humidity on the heat transfer performance, including relative humidity respectively. Four class 45%, 50%, 55% and 60%.The refrigeration capacity and energy efficiency ratio under different operating conditions are compared and analyzed. The causes of this difference are analyzed from the aspects of evaporation temperature, suction and exhaust temperature, suction and exhaust pressure,condensing temperature, etc.. As far as the research is carried out, the following conclusions are obtained:(1) with the increase of the angle of the fin tube heat exchanger, the flow field in the space of the heat exchanger is more and more uniform, and the velocity stratification phenomenon of the heat transfer surface is also reduced, and the areas in the high temperature zone and the low temperature zone are decreased. Air side Nusselt number and pressure drop both showed an upward trend, and the Nusselt number under the positive V type is generally lower than the inverse V type, and the pressure drop is generally higher than the negative V type.(2) the face velocity distribution showed a similar trend of heat exchanger,located just below the vertical position of the fan wind speed is the largest, and as a center to decline gradually, in the heat exchanger reaches the minimum edge position.The negative V type evaporator has an angle of 32.5 degrees, 39 degrees and 45.5 degrees, and the corresponding non-uniformity of the face velocity is 0.86, 0.62 and 0.56 respectively.(3) as the percentage of air drops,the refrigerating capacity of the evaporator with three different angles will be reduced,while the energy efficiency ratio is on the rise. Regardless of how to change the volume percentage, angle of 39 degrees and 45.5 degrees, the cooling capacity and energy efficiency ratio is far higher than the 32.5 degree angle of the evaporator. The difference is more obvious when the air volume percentage is 80% and 70%. Compared with the highest refrigerating capacity,the cooling capacity is decreased by 5.7% and 6% respectively, and the energy efficiency ratio is decreased by 3.5% and 6.7% respectively. When the air volume percentage is 70%, the refrigerating capacity of the evaporator system with an angle of 45.5 degrees is increased by 3.4% compared with the evaporator with an angle of 39 degrees, and the energy efficiency ratio is increased by 3%.(4) as the relative humidity increases, the cooling capacity and energy efficiency ratio of the three angle evaporators increase as a whole. When the air volume percentage is 80%, the evaporator with an angle of 32.5 degrees increases when the relative humidity increases from 55% to 60%, and the refrigerating capacity and energy efficiency ratio are much higher than other kinds of conditions.In this paper,depending on different angles of positive and negative V type finned tube evaporator in room air conditioning for numerical simulation and experimental research, some conclusions obtained above. It has some practical value and academic significance, provide a theoretical basis for the design and optimization of evaporator in air conditioning room.