基于蒸汽压缩技术的热泵蒸汽系统热力性能分析

热泵蒸汽技术相比电锅炉及燃煤、燃气锅炉制取蒸汽,具有更高的一次能源利用效率,并且不产生CO₂和NO_x,符合我国节能环保发展战略。本文提出一种基于蒸汽压缩技术的热泵蒸汽系统,采用两级冷凝直接制取低压蒸汽,再通过蒸汽压缩升压至0.7MPa。并基于EES软件建立数值模型,分析冷凝温度T_cond、蒸发温度T_evap、经济器温度T_econ、喷气率β_g对冷媒压缩机功耗W_refri、蒸汽压缩机功耗W_vapor和系统能效系数COP的影响。结果如下：基于蒸汽压缩的热泵蒸汽系统,制取165℃的饱和蒸汽,在T_evap为50℃、T_cond为93℃时,系统COP为2.996,制取1t蒸汽消耗功率仅为247kW·h;系统COP随T_evap的升高逐渐增大,但是T_evap的升高需要更高的热源温度;蒸发温度不变时,系统存在最佳的T_cond、中间冷却温度T_econ和喷气率β_g,当蒸发温度T_evap为50℃,最佳冷凝温度T_cond为93℃时,最佳经济器温度T_econ为65℃,最佳喷气率β_g为0.13。     

喷气增焓型单级MVR蒸发结晶系统性能分析

针对工业废水蒸发结晶过程中含盐浓度增大、从而导致沸点升和增压比偏高等问题,提出了喷气增焓型单级机械式蒸汽再压缩（MVR）蒸发结晶系统。基于EES软件建立了喷气增焓型单级MVR蒸发结晶系统数值模型,并研究了闪蒸压力P_flash、物料入口浓度c₀、物料循环倍率CR、换热温差△T_preh和△T_mhex以及补气压比指数n和补气率β_v对系统热效率COP、单位闪蒸量的压缩机耗功w_comp、压缩机出口蒸汽过热度△t_suph和换热器UA值等参数的影响。结论如下：喷气增焓型MVR系统相比无喷气过程的单级MVR蒸发结晶系统具有更高的COP、更低的w_comp以及更小的△t_suph;随CR增大,压缩机增压比降低了32.8%,COP提高了54.8%;随P_flash增大,COP呈先降后升趋势,在30~35kPa时存在最低值;换热系统中,主换热器温差△T_mhex对MVR系统性能影响更为显著,△T_mhex每增大1K,COP平均降低4.0%、w_comp平均升高4.9%、UA_mhex平均增加8.9%。     

数据中心冷却系统多级传热温差分析

数据中心冷却系统将IT器件的产热散发到室外环境中去要经过多级传热,本文采用与温差的方法对多级传热进行分析,结论如下：数据中心冷却为在一定温差ΔT驱动下利用载体将芯片散发的热量搬运到室外的过程,过程中存在着热量采集/传热温差ΔT₁损失以及冷源系统排热温差ΔT₂损失;通过减小芯片散热损失,降低气流掺混损失与换热器损失,降低总传热温差ΔT,实现空调系统充分利用自然冷源,运行在完全自然冷却区;当空调系统在完全自然冷却区域运行热管模式时,重力热管COP最高,液泵热管次之,一般高达40～80,甚至超过400,气泵热管最低,并且气泵是现有制冷压缩机COP最高点,可达15～30;当室内外温差小于ΔT₂时,利用补偿温差原理使得制冷循环更加接近热管循环,实现制冷系统最低能耗运行,为数据中心冷却系统节能减排优化提供新的方法。     

高低双螺旋片强化套管换热器壳侧换热

采用实验和数值模拟相结合的方法,研究了高低双螺旋片对套管换热器壳侧的强化换热效果.以仅带有高螺旋片的换热器结构为基础,研究了曲率ε分别为0.44、0.321和0.131时,Reynolds数在4000~20000范围内,低、高螺旋片高度之比l/W对壳侧换热平均Nusselt数Nu_m和流动阻力系数f的影响,考察了等泵功条件下换热器的综合传热性能.对ε=0.44的换热器研究结果表明:当l/W>1/2时双螺旋片强化传热效果显著,且研究工况中l/W=3/4时最优,此时与单一高螺旋片相比,Nu_m值平均提高了10.8%;研究范围内,综合强化传热因子PEC数在1.044~1.204.对不同曲率换热器的研究结果表明,同一l/W值下,PEC数随着曲率ε值的增大而增大,说明双螺旋片结构更适合强化曲率较大的套管换热器壳侧换热.     

MVR耙式干燥系统设计及蒸发性能研究

设计的MVR耙式干燥系统采用罗茨蒸汽压缩机替换耙式干燥系统中的真空泵,将干燥过程脱出的二次蒸汽压缩以提高压力和温度后作为热源使用。节省了大量热能,节能效果显著。该系统干燥物料可以是粉粒状、膏状、浆状,也可以是溶液(此时包含蒸发、结晶和干燥过程)。为了探索MVR耙式干燥系统干燥溶液的规律,首先以水为对象进行了实验研究。结果表明,适当减小压缩比、控制过热度、降低干燥压力均有利于提高系统的运行效率。在实验范围内,MVR耙式干燥系统的能效比(COP)为4.4~8.8,单位能耗除湿量(SMER)为2.0~3.4 kg/k Wh。按照目前的蒸汽电价比及能源状况,该工艺在干燥中仍有很大的应用前景。     

Lightnin静态混合器内气泡分散流体动力学特性实验研究

以Lightnin静态混合器（LSM）内水-空气气液两相体系为研究对象,在连续相水表观速度U_L=0.071~0.127 m/s和离散相空气表观速度U_G=0.007~0.042 m/s的条件下,研究内径100 mm的LSM内气液两相湍流流动阻力与气泡分散水动力学行为。使用分辨率为1920×1080的高速相机Revealer-2F04M采集混合器内不同轴向窗口的气泡群演化过程。结果表明：当U_L<0.085 m/s和U_G=0.025~0.042 m/s时,LSM内的流型为泡状流。随着气泡群流经混合元件数的增加,气泡群的Sauter平均直径d₃₂逐渐减小。当液体表观速度U_L≤0.085 m/s时,Sauter平均直径d₃₂随气体表观速度的增加先减小后增大;U_G =0.028 m/s时d₃₂达到局部最小值,53%的气泡直径d_B/D₀在0.02~0.05范围内。Sauter平均直径、内径与无量纲停留时间τ之间的关系满足d₃₂/D₀=0.031τ^-0.14We^-0.41。平均气含率α的增大显著增加了单位体积内气泡数量密度,加剧气泡与元件表面碰撞频率,增大旋涡二次流强度,导致摩擦系数显著降低;采用Lockhart-Martinelli方法对实验数据回归,得到气液两相流压降预测常数C的关联式：C=5.26×10⁵U_G^-0.91/Re^0.74。     

Lightnin静态混合器内气泡分散流体动力学特性实验研究

以Lightnin静态混合器（LSM）内水-空气气液两相体系为研究对象,在连续相水表观速度U_L=0.071~0.127 m/s和离散相空气表观速度U_G=0.007~0.042 m/s的条件下,研究内径100 mm的LSM内气液两相湍流流动阻力与气泡分散水动力学行为。使用分辨率为1920×1080的高速相机Revealer-2F04M采集混合器内不同轴向窗口的气泡群演化过程。结果表明：当U_L<0.085 m/s和U_G=0.025~0.042 m/s时,LSM内的流型为泡状流。随着气泡群流经混合元件数的增加,气泡群的Sauter平均直径d₃₂逐渐减小。当液体表观速度U_L≤0.085 m/s时,Sauter平均直径d₃₂随气体表观速度的增加先减小后增大;U_G =0.028 m/s时d₃₂达到局部最小值,53%的气泡直径d_B/D₀在0.02~0.05范围内。Sauter平均直径、内径与无量纲停留时间τ之间的关系满足d₃₂/D₀=0.031τ^-0.14We^-0.41。平均气含率α的增大显著增加了单位体积内气泡数量密度,加剧气泡与元件表面碰撞频率,增大旋涡二次流强度,导致摩擦系数显著降低;采用Lockhart-Martinelli方法对实验数据回归,得到气液两相流压降预测常数C的关联式：C=5.26×10⁵U_G^-0.91/Re^0.74。     

回热器对双级压缩和复叠式压缩制冷系统影响的分析

为了研究回热器对双级压缩制冷系统和复叠式压缩制冷系统的影响,以R404A双级压缩制冷系统和R404A/R23复叠式压缩制冷系统为例,通过建立两种制冷系统的热力学模型和(火用)分析法,分析了回热器效率对压缩机排气温度、单位质量制冷量、制冷剂质量流量、系统制热能效比(COP)、系统总(火用)损、系统各部件(火用)损和系统(火用)效率的影响。结果表明,在双级压缩制冷系统中,当回热器效率ε 取0.1～0.9时,系统COP增大4.0%,系统的总(火用)损减少9.6%,而系统(火用)效率增大7.1%;在复叠式压缩制冷系统中,系统COP和系统(火用)效率随高温级回热器效率ε 增大而增大,随低温级回热器效率ε增大而减小,而系统总的(火用)损随高温级回热器效率ε 增大而减小,随低温级回热器效率ε 增大而增大。     

润滑油在内插同轴交叉翼型涡产生器管内流动与传热特性分析

以润滑油为工质,采用数值方法对圆管内插同轴交叉等腰梯形涡产生器的管内流动与传热进行了数值模拟,分析了不同结构参数如扭率（T_r=3,4,5,6）、间距比（S_s/W=0.8,0.9,1.1,1.2）和基带宽度比（W_b/W=0.30,0.45,0.60,0.75）对圆管内插同轴交叉等腰梯形涡产生器的管内流动与传热特性的影响。结果表明：在相同Re下,平均Nusselt数Nu_m、二次流强度Se、强化传热因子JF均随扭率和间距比的减小而增大,而其与基带宽度比的变化没有明显规律,阻力系数f随着扭率的减小和基带宽度比的增大而增大,间距比对f的影响甚微。在相同结构参数下,JF和Se均随Re的增大而增大。在Re=50~1000范围内,相比于光滑圆管,内插不同结构参数的同轴交叉涡产生器的Nu_m增加了32.8%~208.6%,f增加了3.38~8.92倍,JF最大可达1.434。Nu_m与Se呈幂函数相关,内插同轴交叉翼型涡产生器管内的二次流强度决定了其对流换热强度。     

Cu-3-trz-PMo12的合成、结构及催化氧化碘离子性能

采用水热法合成了一例新的多酸基有机-无机杂化物,通过X射线单晶衍射、傅里叶变换红外光谱（IR）、热分析测试（TG）、X射线衍射分析（XRD）、扫描电子显微镜（SEM）、元素分析对化合物进行了表征。X射线单晶衍射分析结果表明,化合物的结构式为（PMo₁₂O₄₀） ［Cu₆（C₂H₄N₄）₆］（PMo₁₂O₄₀）?H₂O（简称为Cu-3-trz-PMo₁₂）,属于三方晶系,R-3空间群,晶胞参数a=1.756 66（3） nm、b=1.756 66（3） nm、c=2.303 24（6） nm、α=β=90°、γ=120°、V=6.155 2（3） nm³、Z=3、R₁=0.023 8、wR₂=0.059 2。化合物是由6个3-氨基-1,2,4-三氮唑、6个Cu⁺、两个经典的Keggin型［PMo₁₂O₄₀］^3-及一个间隙水分子组成的二聚体,两个这样的二聚体通过氢键交替相连形成次级单元,每个次级单元之间又通过氢键作用进而形成一个三维超分子结构。催化研究表明,该非均相催化剂在催化过氧化氢氧化碘离子中表现出较为优异的催化活性且具有较稳定的可重复性。     

The glass temperature of polymer blends

The entropy theory of glasses is used to derive the glass temperature, T_g, of a binary polymer blend in terms of the glass temperatures of the two substituents. The formula is T_g = B₁T_g1 + B₂T_g2, where B_i is the fraction of flexible bonds of substituent i. A bond is flexible if rotation about it changes the shape of the molecule. Bonds in side groups as well as in the backbone are to be counted. This formula assumes that the free volume, taken here to be the volume fraction of empty lattice sites, is the same for each of the three materials. It has no parameters. The above equation expressed in weight fractions, W_i, is (T_g − T_g1)W₁(γ₁/ω₁) + (T_g − T_g2)W₂(γ₂/ω₂) = 0, where ω_i is the weight of a monomer unit and gg_i is the number of flexible bonds per monomer unit. A more general treatment is given. One variation of the more general treatment which expresses the properties of the blend in purely additive terms gives T_g = B₁T_g1 + B₂T_g2 + KB₁B₂(T_g1 − T_g2)(V₀₁ − V₀₂), where V_0i are the free volume fractions of the homopolymers at their glass temperatures and K is a constant. The added term is usually small. The most general form of the equation requires the energy of interaction between the two unlike molecules, which can be estimated by volume measurements on the blend.     

运用粒子图像测速仪研究双层桨搅拌槽内流体流动

The flow fields in a dual Rushton impeller stirred tank with diameter of 0.48 m （T） were measured by using Particle Image Velocimetry （PIV）. Three different size impellers were used in the experiments with diameters of D = 0.33T, 0.40T and 0.50T, respectively. The multi-block and 360° ensemble-averaged approaches were used to measure the radial and axial angle-resolved velocity distributions. Three typical flow patterns, named, merging flow, parallel flow and diverging flow, were obtained by changing the clearance of the bottom impeller above the tank base （C1） and the spacing between the two impellers （C2）. The results show that while C1 is equal to D, the parallel flow occurs as C2≥0.40T, C2≥0.38T and C2≥0.32T and the merging flow occurs as C2≤0.38T, C2≤0.36T and C2≤0.27T for the impellers with diameter of D=0.33T, 0.40T and 0.50T, respectively. When C2 is equal to D, the diverging flow occurs in the value of C1≤0.15T for all three impellers. The flow numbers of these impellers were calculated for the parallel flow. Trailing vortices generated by the lower impeller for the diverging flow were shown by the 10° angle-resolved velocity measurements. The peak value of turbulence kinetic energy （ k/V^2tip = 0.12-0.15 or above） appears along the center of the impeller discharging stream.     

微肋结构对纳米流体绕流圆柱热性能的影响

为了改善传统换热器和换热介质的传热效率,通过两步法制备了不同质量分数（0.1%,0.2%,0.3%,0.4%,0.5%）的TiO₂-水纳米流体,发展了不同微肋结构（竖直肋片和环形肋片）的绕流圆柱换热系统,通过实验研究了圆柱表面微肋结构的类型（竖直肋片和环形肋片）及数量（N₁₍₂₎=4,6,8）、纳米颗粒的质量分数（ω=0, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%）、Reynolds数（Re=514~1205）对绕流圆柱换热系统的影响。结果表明,纳米颗粒的添加和微肋结构能有效提高传热效率,圆柱表面温度明显降低,其中质量分数为0.4%的纳米流体在竖直肋片数量为6时表现出更好的换热性能。     

The anodic dissolution of iron—V. Some observations regarding the influence of cold working and of annealing on the two anodic reactions of the metal

Under conditions, where two anodic current regions, I₂ and I₂, were distinct in the Tafel plots of the iron electrode, the reaction orders with respect to pH were determined. In solutions containing chloride or bromid, pH ca 3–5, the reaction order for I₁(p_1,pH) was close to 1, while that for I₂(p_2,pH) assumed positive or negative values or even values changing from positive to negative over the pH-range. The numerical values were small, 0·2–0·3. Only lightly cold-worked iron was used in this group of experiments.

In another group of experiments only involving acetate containing solutions both cold-worked and annealed electrodes were employed. Until the influence of acetate became negligible at low pH, the effect of the treatment was largely limited to dissolution rates. The characteristic parameters at pH ca 4 were: for the I₁ reaction: b₁ = 30 mV, p_1,pH = 1·7 and p_1,Ac¹ (the reaction order for Ac) = −0·7; for the p₂ reaction: b₂ = 110 to 130 mV, p_2,pH = 0·2 and p_2,Ac = −0·2 to −0·3.

At lower pH the influence of acetate gradually disappeared, and higher values of b₁ and lower values of p_1,pH were then noted for the annealed metal. The I₂ reaction could not be followed here.

The transition between the I₁ and the I₂ reaction was studied at pH ca 4, and some deviation from earlier experience was noted for strongly cold-worked iron.     

Correlation between equation of state and temperature and pressure dependence of self-diffusion coefficient of polymers and simple liquids

Correlation between the equation of state and the temperature dependence of the self-diffusion coefficient D for polymers such as polystyrene (PS) and polydimethyl siloxane (PDMS) and simple liquids such as argon, methane and benzene and the pressure dependence of D for oligomers such as dimethyl siloxane (DMS) and simple liquids such as cyclohexane and methanol has been examined based on the equation of state derived previously. The experimental data used were published by Antonietti et al. and McCall et al. for polymers, by McCall for linear dimethylsiloxanes and by Jonas et al. and Woolf et al. for simple liquids. The expression for D in this work is given by

where A₁(M) is a function of molecular weight M_w, C₁(T) and P₁(T) are functions of temperature and B₁, n₁ and m₁ are constants determined experimentally. For simple liquids, the values of n₁ obtained range from 0.3 to 1.2, with an average , and m₁ is in the range 0.5–1.2, with . For polymers, values of n₁ are in the range 2.5–7.0 for PS and 0.5–1.3 for PDMS and m₁ for DMS is in the range 0.8–1.0. The relation Dη/T = f(M) is found to be useful for simple liquids over a wide range of temperature including the critical region and for pressures up to ≈5 kbar

1 kbar = 100 MPa There is a close correlation between ln(D/T) and _p and β_T through ln(D/T)ln D_c−⁻¹_p−β⁻¹_T, where D_c is D at the critical temperature and _p and β_T are the thermal expansion coefficient and compressibility, respectively. The molecular weight dependence of D for polymers and simple liquids is discussed based on the experimental data and recent theory of Doi and Edwards. A new model for the mechanism of self-diffusion in the liquid state is proposed.