An Experimental and Numerical Study on the Cleaning of Pleated Bag Filters Using Low-Pressure Pulsed-Jets

Pulsed-jet cleaning is recognized as the most efficient method to regenerate bag dust collectors traditionally used in industrial processes to control the emission of particulates.In this study,non-woven needle felt filter bags with and without a film coating material have been analyzed considering different geometries(different number N of pairs of pleated filter bag sides)in the frame of dedicated low-pressure pulsed-jet cleaning experiments.The flow structure inside the bag and the response characteristics of its wall have also been analyzed numerically through a computational fluid-dynamics/structural-dynamics(CFD-CSD)unidirectional fluid-solid coupling method.As shown by the experiments,the peak pressure(P_(0))on the wall of the filter bag with N=8 and 12 is higher,which indicates dust can be removed more effectively in these cases.The peak pressure on the wall increases first and then decreases along the direction of the bag length,while the peak pressure of the pleated filter bag with nonwoven needled felt film coating is greater than that without film coating.A comprehensive analysis of the time variation of acceleration,deformation,strain,stress and other factors,has led to the conclusion that the pleated filter bag with N=12 would be the optimal choice.

Two Phase Pressure Drop Performance of Refrigerant in a Small Horizontal Smooth Tube with 2.5 mm inside Diameter

Two-phase flow pressure drop measurements were made during the phase change heat transfer process of R22 in a small horizontal smooth tube with 2.5 mm inside diameter. Conclusions can be drawn that the quality corresponding to the pressure gradient peak value of small tubes became higher than that of large tubes. The effect of quality to pressure drop becomes weak as the mass flux increases. The experiment data were compared with the predicated values of the state-of-the-art correlations from the open literature. The comparisons between the data and the predictions indicate that most of the state-of-the-art correlations fails to predict the experimental data. Chisholm model shows a relatively better predictive ability than the other empirical correlations although it has a mean deviation of 26.7%. But the predicated values of Chisholm model are lower by 50% than the experimental data when the quality becomes larger.

Measurement and Prediction of Vapor Pressure for H20 ＋ CHaOH] C2HsOH ＋ [BMIM][DBP] Ternary Working Fluids

The ionic liquid, 1-butyl-3-methylimidazolium dibutylphosphate ([BMIM][DBP]) was prepared and the vapor pressures of three set of binary solutions H2O(1)/CH3OH(1)/C2H5OH(1) + [BMIM][DBP](2) were measured at different temperature and in the ILs mole fraction range from 0.1 to 0.6 with a static equilibrium apparatus. The measured vapor pressures were correlated with Non-Random Two Liquid (NRTL) activity coefficient model and the average relative deviations (ARD) between experimental and correlated vapor pressures for these binary solutions were 3.19%, 2.42% and 2.95%, respectively. Then, the vapor pressures of two set of ternary solutions H2O(1) + CH3OH(2)/C2H5OH(2) + [BMIM][DBP](3) were measured with an inclined boiling apparatus and further predicted with NRTL activity coefficient model based on the binary interaction parameters coming from fitting the vapor pressures of the binary solutions. The results indicated that the ternary solutions containing [BMIM][DBP] were shown a strong negative deviation from Raoult's Law when the mole fraction of [BMIM][DBP] was larger than 0.2, which meant that ternary solutions could absorb the refrigerant vapors at the same or below solution temperature. Meanwhile, the average relative deviations between experimental and predicted vapor pressures for ternary solutions were 2.92% and 3.06%, respectively. Consequently, the NRTL active coefficient model used for non-electrolyte solutions was still valid for predicting vapor-liquid equilibrium of binary or ternary solutions containing ILs.

Experimental Analysis of the Performances of Unit Refrigeration Systems Based on Parallel Compressors with Consideration of the Volumetric and Isentropic Efficiency

The performances of a refrigeration unit relying on compressors working in parallel have been investigated considering the influence of the compressor volumetric efficiency and isentropic efficiency on the compression ratio.Moreover,the following influential factors have been taken into account:evaporation temperature,condensation temperature and compressor suction-exhaust pressure ratio for different opening conditions of the compressor.The following quantities have been selected as the unit performance measurement indicators:refrigeration capacity,energy efficiency ratio(COP),compressor power consumption,and refrigerant flow rate.The experimental results indicate that the system refrigeration capacity and COP decrease with a decrease in evaporation temperature,increase of condensation temperature,and increase in pressure ratio.The refrigerant flow rate increases with the increase in evaporation temperature,decrease in condensing temperature and increase in pressure ratio.The compressor power consumption increases with the increase in condensing temperature and increase in pressure ratio,but is not significantly affected by the evaporation temperature.

Characteristics of Abnormal Pressure Systems and Their Responses of Fluid in Huatugou Oil Field,Qaidam Basin

Based on the comprehensive study of core samples, well testing data, and reservoir fluid properties, the construction and the distribution of the abnormal pressure systems of the Huatugou oil field in Qaidam Basin are discussed. The correlation between the pressure systems and hydrocarbon accumulation is addressed by analyzing the corresponding fluid characteristics. The results show that the Huatugou oil field as a whole has low formation pressure and low fluid energy; therefore, the hydrocarbons are hard to migrate, which facilitates the forming of primary reservoirs. The study reservoirs, located at the Xiayoushashan Formation （N1/2） and the Shangganchaigou Formation （N1） are relatively shallow and have medium porosity and low permeability. They are abnormal low-pressure reservoirs with an average formation pressure coefficient of 0.61 and 0.72 respectively. According to the pressure coefficient and geothermal anomaly, the N1 and N1/2 Formations belong to two independent temperature-pressure systems, and the former has slightly higher energy. The low-pressure compartments consist of a distal bar as the main body, prodelta mud as the top boundary, and shore and shallow lake mud or algal mound as the bottom boundary. They are vertically overlapped and horizontally paralleled. The formation water is abundant in the Cl^- ion and can be categorized as CaCl2 type with high safinity, which indicates that the abnormal low-pressure compartments are in good sealing condition and beneficial for oil and gas accumulation and preservation.

Effect of Refrigerant on the Performance of a C3/MRC Liquefaction Process

The Mixed Refrigerant(MR)component is an important factor influencing the performances of natural gas lique-faction processes.However,there is a lack of systematic research about the utilization of propane pre-cooled(C3/MRC).In this paper,this mixed refrigerant cycle liquefaction process is simulated using the HYSYS software and the main influential parameters involved in the process are varied to analyze their influence on the liquefaction rate and power consumption.The results show that an effective way for lowering the power consumption of the compressor consists of reducing the flow through the compressor through optimization of the percentage of mixed refrigerant.The power consumption of the compressor in the hybrid refrigeration process is affected by both flow and pressure ratios.Its specific power consumption can be reduced by increasing the flow and decreasing the pressure ratio at the same time.The increase in refrigerant pressure at the high-pressure end can significantly mitigate the energy loss of the heat exchanger and compressor.

中压补气对R404A冷冻系统性能特性研究

针对纯电动冷藏车冷冻系统在低温工况下出现的排气温度过高、制冷效能较低等问题,研发并搭建了一套采用变频换热风机的微通道换热器新型冷冻系统,研究车厢外环境温度持续增长时,中压补气技术对冷冻系统性能的影响。结果表明:当压缩机转速为4200r/min,库外温度为32℃,库内温度为-15℃,车内换热器风量为80%时,通过试验数据对比分析发现主阀的过热度和补阀的开度分别为5K和25%时冷冻系统制冷性能最佳;当冷冻系统主补阀开度为最佳时,变化库外环境温度发现,与不补气系统对比,系统采用中压补气时,排气温度降低了12.53%~33.80%,制冷量提高了8.38%~16.73%,压缩机功率增加了5.71%~13.07%,COP值上升了2.94%~4.17%。

压力振荡管内波系运动行为的可视化实验研究

气波制冷机具有制冷效率高、可带液工作等优点。为深入研究气波制冷机核心部件压力振荡管内部波系运动,设计了一套双开口压力振荡管可视化流场测量平台,利用视场拼接和纹影技术获得压力振荡管内密度梯度场的定量表达,并将实验结果与二维欧拉方程理论计算结果进行了交叉对比验证,误差为3.2%,证明基于纹影技术追踪管内复杂波系运动的方法不仅直观可视且准确可靠。基于上述方法,对不同压比和转速下的压力振荡管内波系开展了实验研究。实验结果表明,增大压比或转速均会提升激波马赫数。压比由1.5增大至3.0时,激波强度和膨胀波强度均显著增大,强化了对近管口区间气体的膨胀作用。转速由800 r/min提高至2400 r/min时,膨胀波波系运动路径逐渐向管口方向弯曲,降低了膨胀波在管口运动的速度,增加了膨胀波对近管口区间气体的作用时间。

带气液调配蒸发器空气源热泵热水器的实验研究

气液调配蒸发器通过调整干度和质量流速实现传热性能提升。分别将两个管程布置为4-2-4-6-4(蒸发器1)和5-4-3-4-4(蒸发器2)的气液调配蒸发器用于热泵热水器中(分别为系统A和系统B)进行实验,并进行了对比研究。结果表明:相比于蒸发器1,蒸发器2制冷剂分布更均匀,且蒸发器侧压降减小了10.91%。在名义工况下,相比于系统A,系统B制热量减少1.69%,功率也减少1.45%,两个系统COP基本相同。系统B的排气压力比系统A小26.35~84.78 kPa,更有利于压缩机的安全运行;在不同的环境温度下,系统B的压缩机功耗均小于系统A,当环境温度为30℃时,系统B的性能比系统A提高了2.1%。

双螺杆制冷压缩机排气压力脉动特性的实验研究

为研究一台冷水机组用双螺杆制冷压缩机的压力脉动特性,本文测录了压缩机压缩及排气过程的瞬态压力变化,解析其压力脉动频域特性,研究了运行转速和冷凝温度对压力脉动特性的影响,对比了压缩机采用变频与变滑阀两种容量调节方式在相同制冷量下的压力脉动、噪声和热力性能。研究结果表明:压缩腔压力脉动来源于转子工作容积内压力周期性升高,并受齿间多通道泄漏过程的影响;排气腔压力脉动来源于工作容积与排气腔的周期性连通与脱开,受排气压力及气体质量流量等因素影响。随着转速的升高,排气腔压力脉动从转速为1380 r/min时的58.6 kPa升至4200 r/min时的141.0 kPa。随着冷凝温度的升高,压力脉动幅值从34℃时的132.0 kPa升至57℃时的314.0 kPa。在相同制冷量下与容调滑阀相比,双螺杆制冷压缩机采用变频的容量调节方式在压力脉动、噪声和热力性能方面均具有显著优势,压力脉动降低54.6%以上,噪声值下降2.9 dB(A)以上,COP提升5.5%以上。

板壳式热交换器内制冷剂R410A蒸发传热性能研究

通过实验研究了板壳式热交换器内制冷剂R410A的蒸发传热特性,分析了饱和温度、质量流率和平均干度对蒸发传热系数及两相摩擦压降的影响。将实验数据与现有的蒸发传热预测模型进行比较,拟合得到了板壳式热交换器内R410A蒸发传热努塞尔数和摩擦因数的关联式。研究结果表明,R410A的蒸发传热系数随平均干度的增大先增大后减小,随质量流率的增大而增大,随饱和温度的升高而减小。两相摩擦压降随平均干度、质量流率的增大而增大,随饱和温度的升高而减小。R410A努塞尔数、摩擦因数的关联式计算值与实验值的平均误差绝对值分别为3.78%、4.08%。

超高压处理对石斑鱼冷藏期间品质的影响

为探讨超高压处理对石斑鱼冷藏期间品质的影响,该试验以石斑鱼为原料,研究不同超高压(100、200、300、400、500 MPa,常温保压5 min)处理对石斑鱼在4℃冷藏期间(0~18 d)菌落总数、挥发性盐基氮(total volatile base‐nitrogen,TVB‐N)值、总巯基含量、pH值、硫代巴比妥酸(thiobarbituric acid,TBA)值、质构和色泽的影响。结果表明:300 MPa及以上处理能显著降低鱼样在整个冷藏过程中的菌落总数(P<0.05);当处理压力达到400、500 MPa时,可有效延缓鱼样在冷藏中后期(8~18 d)TVB‐N值和pH值的上升,同时降低总巯基含量的下降速率,而在100、200 MPa处理中,上述指标与对照组相比变化不明显;各超高压处理对鱼样在冷藏期间的TBA值变化影响不显著(P>0.05)。结合质构与色泽分析,与对照组相比,400、500 MPa处理能显著提高鱼样在冷藏期间的硬度、弹性和咀嚼性(P<0.05),但对内聚性的变化影响不明显;色泽方面,300 MPa及以上处理可显著提升鱼样在冷藏期间的L值(P<0.05),同时a值显著下降(P<0.05),但对b值变化影响不明显,总色差ΔE值有效降低。综合各数据分析及能耗考量,认为400 MPa处理5 min可作为石斑鱼最适加工条件,既能有效降低鱼肉的菌落总数,同时也能较好地保持鱼肉在冷藏期间的品质特性。

回热对跨临界CO_(2)喷射制冷系统的影响

目的:研究回热对跨临界CO_(2)双级压缩/喷射制冷系统性能的影响。方法:采用仿真模拟软件建模,分析在不同气体冷却器出口温度(25~45℃)、高压侧排气压力(7.4~9.5 MPa)、蒸发温度(-40~-15℃)和中间压力(3~5 MPa)的情况下,回热对低压压缩机吸气温度、排气温度、比功率增量以及系统性能系数的影响。结果:在特定的回热度下,随着中间压力的增加,低压压缩机排气温度和比功率增量升高;但随着蒸发温度升高,低压压缩机排气温度和比功率增量逐渐降低。在标准工况下,回热系统的性能系数低于不带回热系统的,同时随着回热度的增加,回热系统的能效降低。结论:随着回热度的增加,低压压缩机吸气温度、排气温度和比功率增量显著升高。但回热改善跨临界CO_(2)双级压缩/喷射制冷系统性能效果不佳。

某系列直升机蒸发循环制冷系统压力故障排查及处理

结合某系列直升机蒸发循环制冷系统的构造和工作原理,分析了其使用过程中的常见故障,对与制冷剂压力相关的故障给出了相应的排查方法,并给出了制冷剂渗漏检测和加注等后续处理措施和方法,提出了制冷系统维护及设计建议。

直升机核生化防护体系集成设计与仿真

直升机作为国家战略层次的飞行器,其快速进出战场的能力必将在核生化威胁中起到关键作用。为了保障舱内人员的安全,必须对直升机的核生化防护系统进行研究。从系统顶层架构设计出发,基于系统集成手段,设计了一种直升机核生化防护体系。针对各子系统开展了详细构型设计,包括:基于小型高转速电动压气机的气源增压子系统;基于变压吸附原理,可实现机载实时再生的滤毒通风子系统;基于热泵型蒸发制冷循环,利用滑油废热及双蒸发器并联驱动的温度控制子系统;综合座舱超压防护及增压需求的压力调节子系统。基于系统构型,建立了仿真模型,对系统动态性能开展了仿真验证研究。仿真结果表明:在各种极端条件下,舱内压力、温度均满足设计要求。当进入核生化威胁区域时,滤毒通风子系统能够有效吸附有毒物质,吸附床通过机载实时再生,延长了在核生化威胁区域的作业时间,为直升机核生化防护系统设计提供了新的思路。

制冷工质压力对红外用波纹管J-T制冷器制冷性能的影响研究

通过具体实验研究了制冷工质压力对波纹管自调式J-T制冷器制冷性能的影响。实验工况内的结论如下:在一定的压力范围内(11 MPa≤P≤23 MPa),随着工质压力的增大,应用该款制冷器的红外系统的启动时间逐步缩短,但启动加快的速率会随工质压力的增大而减小。当工质压力增大到一定程度(23 MPa≤P≤27 MPa)时,启动时间将趋于稳定。在一定的压力范围内(11 MPa≤P≤15 MPa),随着工质压力的增大,应用该款制冷器的红外系统的蓄冷时间逐步加长;但工质压力增大到一定程度(15 MPa≤P≤27 MPa)时,蓄冷时间将趋于稳定。在一定的压力范围内(11 MPa≤P≤27 MPa),随着工质压力的增大,制冷器启动时的最大流量呈线性增大趋势,运行时的稳定流量呈逐步增大趋势。本文实验研究的过程方法和研究结果具有工程借鉴意义。

伴生气液化处理工艺能耗分析与优化

为降低伴生气液化处理工艺的能耗,减少冷剂组分和工艺参数之间的相互影响程度。针对双循环混合冷剂(DMR)液化工艺建立了对应的模拟流程,以比功耗为目标函数,换热器温差、压缩机等熵效率等为约束条件,结合KBO法和SQP法完成了工艺流程的能耗优化与调整。结果表明:比功耗的变化趋势与制冷剂中最小碳数组分的变化趋势相同;制冷剂中N_(2)含量越高,比功耗越大;对于预冷剂,应降低C_(2)H_(6)和C_(3)H_(8)的组分含量,升高nC_(5)H_(12)的组分含量;对于深冷剂,应降低CH_(4)、C_(2)H_(6)和N_(2)的组分含量,升高C3H8的组分含量。通过优化制冷剂的流量、配比、压力等参数,总能耗从6236 kW降至4895.1 kW,降幅21.50%;比功耗从0.3746 kWh/kg降至0.3215 kWh/kg,降幅14.17%,节能减排效果显著。

大型低温常压液氨储罐及配套冰机的设计选型

简述了当前大型低温常压液氨储罐的技术方案,比较了不同低温常压液氨储存方式的技术特点,同时对液氨储罐在不同的操作工况下配套冰机制冷能力给出了详细的计算方法,分析了影响冰机制冷量的各种因素,采用理论计算结合工程经验角度分析了影响冰机设计选型的各种要素,为大型液氨储存工艺方案选择及优化,各种氨储存系统操作工况下的冰机的配置、设计选型提供了借鉴和参考。

冰箱内外压差变化对冰箱性能影响研究

冰箱制冷运行过程中存在“呼吸效应”,箱内外气体会随“呼吸效应”产生热质交换。通过压差实验的方法,研究单循环风冷冰箱制冷过程中箱内风机、风门、压缩机开停切换,冰箱状态变化等对箱内外压差形成机制影响。经验证:通过封闭化霜排水管,可改变外界高温高湿气体进入箱体内的途径,增大冷藏室进气量,延长外界气体进入箱内的路径,从而提升冷藏室的相对湿度,对蔬菜水果保鲜有利,同时节能减排。

基于压降模型的多联机配管长度评估方法及试验验证

多联机的配管长度决定了制冷剂输配、回油方案,掌握多联机配管长度识别的精确算法,可以针对性改进制冷剂输配、回油,使得系统更加节能。提出了一种基于阻力模型的多联机配管长度识别方法,包括利用基于等熵效率的压缩机广义热平衡法迭代计算系统制冷剂的循环量;建立基于内机开机台数的阻力加权系数的联机主支管和末端支管压降模型,以精确的评估不同负荷率下的主管和支管压降;建立以末端支管长度和阻力为引导的包含不确定度的多联机配管长度模型,客观评估预测的联机管长度。试验验证表明所述方法,对于短配管(L为15m),通过模型计算得到的长度均值16 m,各工况下计算误差不超过10%;对于长配管(L为150m),通过模型计算得到的长度均值141 m,各工况下计算误差不超过20%。该算法可以克服直接采用压降难以识别配管长度的难题。