散热器矩形肋片的散热量数值计算与结构优化

本文利用matlab对一种形状的矩形肋片进行了散热数值计算以金属热强度为结构优化的目标函数,得出了此种肋片的最佳肋高尺寸本文中当金属热强度最大时肋的高度。通过对计算结果的分析,得到了辐射换热量在肋片散热量中所占的比例,从而验证了在肋片散热计算中要考虑辐射换热的结论。     

散热器肋片的数值计算和结构优化

本文以金属热强度为结构优化的目标函数，利用Matlab对一种矩形肋片进行了散热数值计算；通过对计算结果的分析得出了该肋片的最件肋高尺寸。作者认为利用Matlab来解决这类肋片优化问题非常方便。     

变频空调器电子元器件板肋式散热器仿真与优化

电子元器件散热困难导致变频空调机组运行异常,为解决此问题,采用Fluent对电子元器件板肋式散热器及其周围空气流场的流动和传热特性进行了模拟研究。建立了仿真计算模型,并与实验参数进行了对比,仿真计算误差不超过10.8%。对原型散热器肋片进行了结构模拟研究,结果显示,在低风速散热环境下,单向长肋片板肋式散热器尾端的空气流量小、温度高,散热效果较差。提出了一种新型板肋式散热器形式,采用多段肋片、错向肋片结构,散热效果得到较大提升。原型散热器经优化后,各元器件温度降低2.8~4.6℃,优化率约为3.2%~5.5%。     

风道尺寸对设备强迫风冷散热性能的影响分析

对于大功率设备来说，强迫风冷是其电子元器件的主要散热方式，而影响强迫风冷的因素包括设备内部结构、外部工作环境及风扇效率等。为了使设备的散热效果达到最佳，通过控制变量法，对设备内部风道进行优化设计。以计算流体力学为基础，运用FloTHERM软件，对设备在不同进风口宽度以及不同风道宽度工况下的散热情况进行仿真。通过对比分析，总结在风扇规格选定的情况下，如何合理地设计进风口宽度与风道宽度。     

相变蓄热构件传热强化及其对轻质墙体蓄热性能提升研究

本文提出一种与轻质墙体内侧结合、增强其蓄热性能的相变蓄热构件。利用多物理场耦合的有限元软件COMSOL建立复合墙体的数值计算模型并验证其准确性,以相变蓄热构件内相变材料的完全熔化时间和构件表面温差作为评价依据,分析构件内部不同参数肋片的强化传热机理并优选出最佳肋片参数;以深圳地区为例,从相变材料的用量和相变温度对相变蓄热构件的使用效果进行优化,比较了肋片在相变蓄热构件提升2种轻质墙体蓄热性能上的差异。结果表明,长而薄的肋片在适宜的肋片间距下能够提升石蜡温度场和流场变化的协同性,增强传热速率;在不影响复合墙体对室外热扰延迟时间的前提下,肋片的添加使加气混凝土复合墙体的显热蓄热和放热时长分别缩短了44.8%和26.3%,聚苯板复合墙体的显热蓄热和放热时长分别缩短了20.8%和52.9%,肋片对聚苯板复合墙体的有效蓄热量和蓄热能力的提升效果较好。本文的研究结果能够为相变蓄热构件的设计和应用提供参考依据。     

肋片长度对相变材料熔化过程影响的数值模拟

通过数值模拟研究了三套管式相变蓄热器的纵向肋片长度对熔化速率的影响.为得出更精确的结论,以对蓄热器结构优化有更实际的指导意义,将肋片长度在一个较小范围内进行了划分,设置了7种肋片长度的蓄热器,同时将模拟结果与光管蓄热器进行对比.结果表明,相较于光管蓄热器,增加纵向直肋可以有效提高熔化速率,且肋片长度越大熔化时间越短,但存在一临界肋片长度.临界肋片长度可作为优化套管式蓄热器结构的重要参考方向.     

光伏电池板强制循环冷却技术的数值研究

为了降低温度对光伏电池板发电效率的影响,提出了利用强制循环通风冷却技术,通过添加铝制肋片加强背板散热,改善光伏电池板的温度分布情况,提升光电转化效率.利用CFD模拟仿真技术对肋片间距、肋片高度进行模拟优化,模拟结果表明,在太阳辐射强度为500W/m~2的条件下,肋片间距L=5mm、肋片高度H=70mm时,该型号光伏电池板的发电功率达到最大,为110.8 W.同无肋片强制通风冷却相比,光伏电池板温度降低了19.3℃,发电功率提高了8.7%.     

空调机热交换器的表面处理

一、热交换器存在的问题空调机的心脏——热交换器的散热板由铝肋片构成,由于夏季空调机的室内部分的铝肋片和冬季空调机的室外部分的铝肋片表面温度都在露点温度以下,因此,空气中的水份形成冷凝水,附着在肋片表面。该冷凝水形成水滴,在肋片之间形成水桥,减小了空气的通路,加大了通风阻力,从而产生电力损耗、噪音、水滴飞溅等不良情况。另外,在冬季寒冷地区,空调机的室外部分易     

自然冷却下太阳能PV板发电效率的影响研究

基于一维稳态传热模型,通过数值模拟与计算,进行了自然冷却条件下散热肋片对PV板发电效率的影响研究,对不同因素包括PV板水平倾角、空气温度、风速和肋片高度等对PV板发电效率的影响进行了研究,研究结果对于PV板被动式冷却设计具有一定的实际意义和参考价值。     

新二郎山隧道通风系统局部结构优化研究

新二郎山隧道长13.4 km,采用四斜井三区段分段纵向式通风。为了降低隧道运营期间的通风能耗,通过数值模拟对隧道通风系统中的渐缩风道长度以及渐缩角度、渐扩风道长度以及渐扩角度、弯曲风道弯曲角度进行了优化;借鉴泥巴山隧道竖井自然风通道经验,增设自然风通道排水设施与风道控制风门,设计了新二郎山隧道的自然风通道;利用CFJZ6通风机综合测试仪对隧道通风系统渐扩段建成后的局部阻力损失系数进行了现场实测。根据优化结果推荐其渐缩段风道渐缩角度为10°,风道长度为6.8 m;渐扩段风道渐扩角度为10°,风道长度为24.1 m;弯曲风道弯曲角度80°。优化后渐扩段局部阻力系数为0.100 7远小于优化前的0.380 2。     

含翅片矩形腔体内相变材料传热特性研究

相变材料低导热特性影响相变传热进程,添加金属翅片可有效提高相变材料传热速率.本文通过使用有限元软件模拟相变材料的熔化过程.通过改变翅片高度、翅片厚度、翅片个数、加热壁面的温度以及将铝片换为导热性能更好的铜片来研究相变材料熔化过程.研究结果表明:增加翅片高度、翅片个数和提高热源壁面温度对强化换热效果具有显著的作用,增加翅...     

Performance improvement of D-sorbitol PCM-based energy storage system with different fins

This paper is aimed at enhancing the heat exchange rate in the thermal energy storage system with dissimilar fins and encapsulation materials. Experimentation is done with d-sorbitol as phase change material with different encapsulating materials, copper, stainless steel (SS) and brass, in pin fin, annular fin and rectangular fin. The results are analysed for their thermal performance characteristics during both the charging and discharging processes. During charging, copper encapsulation showed a higher heat energy transfer rate around 2340?kJ. During discharging, a loss of 22% in heat extraction is seen in copper encapsulations, 6% and 19% in brass and SS encapsulations, respectively. These results show that the usage of annular fins is a valuable practice to increase the heat stored and recovered, in a latent heat storage system. The most cost-effective encapsulation is SS balls with annular fins as compared with copper and brass encapsulations.     

高温相变蓄热电暖器蓄放热性能试验研究

对研制的高温相变蓄热电暖器的蓄放热性能进行了试验研究,结果表明该电暖器蓄热密度大,蓄放热性能稳定,蓄热时隔热性能好,放热时放热速率可满足普通供暖要求。     

Heat transfer enhancement of the latent heat storage system using different encapsulating materials with and without fins

This study is aimed at analysing the heat transfer characteristics of different encapsulating materials and the fins on the overall heat transfer in the latent heat storage system (LHSS). Experimentation is done with different phase change materials (PCMs) (d-mannitol, d-sorbitol and paraffin wax) using different encapsulating materials, i.e. copper, aluminium and brass, with and without fins. During the charging process, there is an average 15% heat loss of copper encapsulations without using fins as compared with using fins. The heat losses in aluminium and brass encapsulations are 10% and 15%, respectively. In the discharging process, 23% of heat extraction loss is seen in copper encapsulations, 5% and 18% in aluminium and brass encapsulations, respectively. The results showed that the usage of fins is an effective technique to increase the heat stored and recovered in a LHSS. The most cost-effective encapsulation is aluminium balls with fins as it has the lowest cost/kJ as compared with other two.     

Thermal performance of latent heat storage for free cooling of buildings in a dry and hot climate: An experimental study

Experimental studies on the Phase Change Material (PCM) storage unit for building ventilation in dry and hot climates were conducted to determine its thermal performance. The PCM unit stored the night time coolness and used it for cooling the hot ambient air during day time. The influence of air flow rate and the inlet air temperature on cold accumulation in PCM during charging process and cold extraction from the PCM during discharging process were analyzed. The air temperatures used for charging of PCM were 20^oC, 22^oC and 24^oC, while during the discharging process, it was at 36^oC, 38^oC and 40^oC. The air flow rates considered for charging of PCM were 4 and 5 m³/hr/kg of PCM. Experimental observations showed that solidification of PCM was more sensitive to the charging air temperature compared to the air flow rate. When the charging air temperature was reduced from 22^oC to 20^oC, ∼33% less time was needed to completely solidify the PCM. Moreover, when the charging temperature was increased from 22^oC to 24^oC, ∼52% more time was required by the PCM to complete the solidification process. Changing the air flow rate from 4 m³/hr to 5 m³/hr reduced the solidification time period up to ∼16%.     

冷凝蓄热器蓄放热过程模拟研究

为解决传统单级压缩空气源热泵在严寒地区制热性能差、极低环境温度下无法运行的问题,提出了一种基于相变蓄热的空气源热泵联合低温热水地板辐射供暖系统。通过构建系统模型,对关键部件冷凝蓄热器的蓄放热过程进行了研究,分析了冷凝蓄热器的动态运行特性。研究结果表明:冷凝蓄热器连续蓄热14 h后,平均蓄热功率为7.19 kW,COP为1.97,蓄热量达到100.59 kW·h;冷凝蓄热器在放热过程中可持续放热10 h,供水温度不低于40℃,平均放热功率为10.06 kW,实现了基于相变蓄热的空气源热泵联合低温热水地板辐射系统的全天候连续供暖。     

Experimental study and analysis of air heating system using a parabolic trough solar collector

An experimental study of air heating system was carried out using a parabolic trough collector with a U-tube aluminium heat exchanger. An evacuated tube placed at the focal length of the parabolic trough collected the solar radiations reflected from the surface of parabolic trough. The air was used as a working fluid, which was heated by passing it through a U-shaped aluminium heat exchanger placed inside the evacuated tube. It was found that efficiency of the parabolic trough collector depends on the mass flow rate, solar intensity and use of fins. It was observed that by using fins at a high mass flow rate of 4.557?kg/h, the maximum temperature of 126°C was achieved which is 13.27% more than the maximum temperature obtained without fins. Furthermore, for a low-mass-flow rate of 1.69?kg/h, the maximum temperature obtained was 149°C.     

风冷热泵机组的结霜特性研究

对风冷热泵在制热运行时结霜的影响因素如冷却面、气流、时间等进行了分析,并就结霜对机组蒸发温度、风量的影响进行了研究,发现结霜后肋片间通道堵塞、蒸发器传热热阻增加、蒸发温度下降,运行工况变差。     

用于回收空调冷凝热的复合相变蓄热器

本文主要介绍一种复合相变蓄热器的工作原理和结构形式,提出了应用中所存在的问题。利用相变材料放出潜热提高供水温度,在不需用热水时,压缩机不必停机从而加热融化相变材料以储存热量。采用相变材料回收空调冷凝热,既具有节能又具有环保的特点。     

相变通风屋顶的供热节能优化设计研究

提出太阳能相变屋顶系统(主要由太阳能空气集热系统、相变通风屋顶组成),将两种相变材料(PCM1、PCM2,PCM1用于供冷期蓄冷,相变温度在35℃左右。PCM2用于供暖期蓄热,相变温度在18℃左右)及风道(预制在钢筋混凝土板内,供冷期利用夜间低温空气冷却屋顶与PCM1,供暖期利用太阳能空气集热器出口热空气加热屋顶与PCM2)预制在屋顶内,形成相变通风屋顶(由上至下的基本结构为保护层、防水层、找坡层、保温层、找平层、PCM1、钢筋混凝土板),实现供冷期夜间蓄冷日间吸热、供暖期日间蓄热夜间放热。针对供暖工况,采用模拟方法,结合评价指标,对相变通风屋顶中相变材料(由于供暖工况PCM1不发生相变,因此研究对象为相变材料PCM2)的相变温度、结构(即相变材料位置)、相变材料厚度进行优化选取。A型相变通风屋顶将PCM2设置在PCM1与钢筋混凝土板之间,B型相变通风屋顶将PCM2设置在钢筋混凝土板下面,C型相变通风屋顶将PCM2设置在预制风道外圈。PCM2的最佳相变温度为18~20℃,最优结构为B型相变通风屋顶,PCM2最佳厚度为30 mm。与无相变通风屋顶(将B型相变通风屋顶中的30 mm厚PCM2相变材料替换成相同厚度的水泥砂浆,保留预制风道,其他各层材料及厚度均保持不变)相比,最佳相变通风屋顶(PCM2相变温度为18~20℃、厚度为30 mm的B型相变通风屋顶)的各项评价指标均更优。