基于内融冰的蓄冰槽蓄冰和融冰模型

分析了内融冰顺排盘管式蓄冰槽蓄冰过程中的相变传热，提出简化假设，并在此基础上建立了管束模型。利用热阻网络法，对模型进行计算分析。在改变蓄冷槽换热管的材料，管径，管间距及不同进口参数的情况下，分析了蓄冷槽结构和工况对蓄冰，融冰性能的影响。     

内融冰式蓄冰管传热特性数值分析

对内融冰式蓄冰管的蓄冰和融冰过程进行了数值模拟,运用焓法建立了蓄冰管蓄冰和融冰时的动态数学模型并进行求解,分析了管内流体的流速、入口温度、管径、管外水或冰的初始温度等各种因素对蓄冰管蓄冰和融冰传热性能的影响。     

外融式冰盘管取冷特性实验研究

对原有的不完全冻结式内融冰蓄冰槽进行了外融冰改造及外融取冷实验。结果表明,鼓气扰动对外融冰取冷特性起着关键作用。具体分析了初始蓄冷量、取冷水流量、鼓气量对外融冰取冷性能的影响。     

基于Fluent的蓄冰槽气体取冷特性研究

为了探讨不同进气状态下的蓄冰槽释冷特性,通过对蓄冰槽与进风气体的耦合传热过程分析,建立了矩形蓄冰槽内外两侧的二维传热模型,基于CFD软件Fluent对不同进风温度、进风速度的工况进行了数值模拟,得到出风温度和冰的融化率在不同工况下随时间的变化特性。结果表明:进风温度越高,出风温度越高,同时出风温度的降幅越大,进风温度对融冰速率的影响越明显;进风速度越大,出风温度减少量越小,进风速度对融化速率的影响越弱。     

外融式冰盘管取冷特性的实验研究

介绍了在外融冰式冰盘管实验台上所作的外融冰槽取冷特性实验研究，揭示了影响外融冰槽热工特性的流量，进口水温，负荷强度，初始蓄冷量，取冷水流进出口方式等主要因素及其作用规律，评论了冰盘管蓄冷技术的发展和应用前景。     

并联冰盘管蓄冷装置设计方法探讨

在研究并联冰盘管蓄冷装置制冰、融冰特性的基础上，讨论了包括确定蓄冰槽容积、蓄冰量，盘管长度，盘管排列方式等内容的设计方法。认为这一探讨有益于冰蓄冷装置的系列化设计及系统的控制运行。     

冰蓄冷系统校核与优化

亚洲基础设施投资银行冰蓄冷系统采用部分负荷冰蓄冷系统,主机采用双工况机组、上游串联的内融冰形式。日间空调工况运行与蓄冰槽联合供冷;蓄冰时段制冰工况运行向蓄冰槽制冰。施工前通过对冰蓄冷系统的校核与优化,向业主提出建议并得到采纳,修改了施工图,圆满地完成了冰蓄冷系统建设。     

蓄冰空调系统设计中冷水机组与蓄冰桶的选择

对蓄冰桶融冰放冷性能进行计算机模拟，在全负荷蓄冰和部分负荷蓄冰这两种运行模式下，分析了蓄冰空调系统设计中冷水机组的选择和冷负荷变化对蓄冰桶选择的影响。     

内融冰式蓄冰管融冰性能的数值模拟

在考虑自然对流和不考虑自然对流两种情况下,建立了内融冰式蓄冰管融冰时的二维传热数学模型,分析了出口温度、换热量、融冰厚度等参数的变化趋势,并分析了融冰时自然对流的影响,为正确的进行系统优化、参数匹配等提供了理论指导。     

直膨式冰蓄冷空调蓄冰过程的传热研究

对直膨式蓄冰空调系统的蓄冰槽进行了蓄冰过程的传热实验,得到了蓄冰过程中水温下降规律和水温分层情况。通过本实验研究可以为直膨式冰蓄冷空调产品的设计开发提供实验基础,具有一定的工程运用价值。     

生物载体与曝气方式对氧化池氧转移特性的影响

对比研究了不同曝气量条件下,分别采用穿孔曝气和微孔曝气时,装填不同载体的接触氧化池的氧转移特性。结果表明,在试验范围内,各接触氧化池的氧总传质系数均随曝气量的增加而增大,但增加速度逐渐变缓。当曝气量为3.5 m3/h时,网格载体池的氧转移效率和动力效率达到最大值,分别为5.25%和3.22 kgO2/(kW.h),是竖管载体池和悬浮球载体池的1.14倍,是无载体池的1.22倍。当处理对象为生活污水时,接触氧化池内可采用微孔曝气+竖管(或悬浮球)载体;而当处理对象为高浓度有机废水时,可采用穿孔曝气+网格载体+悬浮球载体。     

Effects of aeration patterns on the flow field in wastewater aeration tanks

Due to the high energy input of aeration, the spatial distribution of air diffusers largely determines the flow field in aeration tanks. This has consequences on the efficiency of the aeration system, the performance of the aeration tank and on tank operation and control. This paper deals with these effects applying both Computational Fluid Dynamics (CFD) enhanced with a biokinetic model and full scale validation using velocity and reactive tracer measurements with high temporal and spatial resolution. It is shown that small changes in the diffuser arrangement drastically change the overall flow field. Using different aeration patterns in the same tank may lead to large scale instabilities in the flow field that lower plant performance and produce strong variations in concentration signals impeding their use for plant control. CFD is a valuable tool to analyze the interaction of flow field and aeration and their effects on plant performance and operation. But, in complex flow situations experimental validation is needed and strongly suggested.     

太阳能辅助地源热泵供热运行特性研究

介绍了太阳能辅助地源热泵,对其各装置性能进行了研究。分析了地下埋管换热器进出口水温及有、无蓄热水箱对太阳能辅助地源热泵性能的影响。太阳能辅助地源热泵制热性能系数随地下埋管换热器进口水温的升高呈下降趋势,随其出口水温的升高呈上升趋势。随地下埋管换热器出口水温升高,蒸发器传热量增大。当太阳能辅助地源热泵中无蓄热水箱时太阳能集热器的瞬时集热效率高于有蓄热水箱时的瞬时集热效率。就总体效果而言,有蓄热水箱要优于无蓄热水箱,这样可使地源热泵运行更加稳定。     

A study of optimum aeration efficiency of a lab‐scale air‐diffused system

Up to now, tremendous efforts have been devoted to modelling the oxygen transfer coefficient (k_La) for diffused aeration systems, while not considering the corresponding energy consumption. Enhancing k_La is favorable for an exemplary oxygenation process, but may come at the cost of greater energy withdrawal, an unwelcome tradeoff. Assessing the aeration efficiency (the rate of oxygen delivered per unit energy) reflects the overall effectiveness of an aeration process and guarantees a superior system performance. Presented here is a lab‐scale study that investigates the effect of the orifice diameter, the airflow rate and the water column on the aeration efficiency. Various combinations of the studied parameters were tested using a cylindrical tank with a single orifice for air injection. An optimal performance of the aeration efficiency was observed at an orifice diameter of 0.3 mm when tested under 0.91 m water column and an airflow rate of 0.05 SLPM. Furthermore, a new empirical formula of aeration efficiency was established with a high correlation index (R² = 0.97) to allow preliminary prediction of aeration efficiency.     

Mathematical models of biological waste treatment processes for the design of aeration tanks

The paper discusses the application of formal mathematical models of biological treatment in designing aeration tanks. It deals with a complete mixing aeration tank, an ideal plug-flow tank, and a many-step aeration tank.Selection is substantiated of the simplest non-linear Monod's model for biochemical oxidation. A new model is advanced taking into consideration, among others the effect of pollutant sorption by activated sludge. The model permits calculating the optimal volumes of the aeration tank and stabilization tank in the contact stabilization system.     

Surfactant effects on alpha-factors in aeration systems

Aeration in wastewater treatment processes accounts for the largest fraction of plant energy costs. Aeration systems function by shearing the surface (surface aerators) or releasing bubbles at the bottom of the tank (coarse- or fine-bubble aerators). Surfactant accumulation on gas-liquid interfaces reduces mass transfer rates, and this reduction in general is larger for fine-bubble aerators. This study evaluates mass transfer effects on the characterization and specification of aeration systems in clean and process water conditions. Tests at different interfacial turbulence regimes show higher gas transfer depression for lower turbulence regimes. Contamination effects can be offset at the expense of operating efficiency, which is characteristic of surface aerators and coarse-bubble diffusers. Results describe the variability of alpha-factors measured at small scale, due to uncontrolled energy density. Results are also reported in dimensionless empirical correlations describing mass transfer as a function of physiochemical and geometrical characteristics of the aeration process.     

Computational model for a ground coupled space cooling system with an underground energy storage tank

A computational model for determining annual periodic performance of a cooling system utilizing a ground coupled chiller and a spherical underground thermal energy storage tank is developed. An analytical solution for the transient heat transfer problem outside the storage tank is obtained by the application of complex finite Fourier transform (CFFT) technique. Analytical expressions for heat gain to the space and energy consumption of the chiller are acquired, and these expressions are coupled with the transient temperature field problem to obtain computational model. Variation of water temperature in the storage tank is calculated using the transient solution of the problem over an entire year for different soil, chiller, and storage tank characteristics. Temperature profile of earth surrounding the storage tank and the COP of the cooling unit are also investigated under various assumptions and varying system design and operating conditions. The results show that water temperature in the storage tank remains under ambient air temperature during summer months, and thus the proposed ground coupled cooling system should yield higher COP values compared to a corresponding air source system.     

中空纤维膜无泡曝气氧传质性能试验研究

为探究中空纤维膜无泡曝气技术水体充氧性能,使用聚四氟乙烯(PTFE)和聚丙烯(PP)两种材质的中空纤维膜组件,分别在曝气压强为2、4、6 kPa,曝气流量为18、36、54 L/h条件下进行清水曝气测试,并对两种中空纤维膜的氧传质系数、氧传质速率以及曝气效率等进行分析。结果表明,PTFE和PP两种中空纤维膜组件均能实现无泡曝气,且PP中空纤维膜组件的充氧效果相比PTFE组件要好;当曝气压强为4 kPa、曝气流量为36 L/h时,PTFE和PP膜组件的氧传质速率分别为0.326、0.550 g/(m^2·h)。中空纤维膜无泡曝气技术具有操作压力小、氧传质速率高等特点,充氧效果优于传统曝气。     

Predicting oxygen transfer of fine bubble diffused aeration systems--model issued from dimensional analysis

The standard oxygenation performances of fine bubble diffused aeration systems in clean water, measured in 12 cylindrical tanks (water depth from 2.4 to 6.1m), were analysed using dimensional analysis. A relationship was established to estimate the scale-up factor for oxygen transfer, the transfer number (N(T)) The transfer number, which is written as a function of the oxygen transfer coefficient (k(L)a(20)), the gas superficial velocity (U(G)), the kinematic viscosity of water (nu) and the acceleration due to gravity (g), has the same physical meaning as the specific oxygen transfer efficiency. N(T) only depends on the geometry of the tank/aeration system [the total surface of the perforated membrane (S(p)), the surface of the tank (S) or its diameter (D), the total surface of the zones covered by the diffusers ("aerated area", S(a)) and the submergence of the diffusers (h)]. This analysis allowed to better describe the mass transfer in cylindrical tanks. Within the range of the parameters considered, the oxygen transfer coefficient (k(L)a(20)) is an increasing linear function of the air flow rate. For a given air flow rate and a given tank surface area, k(L)a(20) decreases with the water depth (submergence of the diffusers). For a given water depth, k(L)a(20) increases with the number of diffusers, and, for an equal number of diffusers, with the total area of the zones covered by the diffusers. The latter result evidences the superiority of the total floor coverage over an arrangement whereby the diffusers are placed on separate grids. The specific standard oxygen transfer efficiency is independent of the air flow rate and the water depth, the drop in the k(L)a(20) being offset by the increase of the saturation concentration. For a given tank area, the impact of the total surface of the perforated membrane (S(p)) and of the aerated area (S(a)) is the same as on the oxygen transfer coefficient.     

Feedforward control of a wastewater plant

A feedforward control strategy to compensate for disturbances in the applied biological load to the activated sludge plant was designed. This strategy was generated from Laplace-domain transfer function models predicting the dissolved oxygen concentration at the end of the aeration tank from the applied biological load and the air flowrate. In producing these models, the Luggage Point Wastewater Treatment Plant was used to obtain plant data. After conducting a series of computer simulation tests, the improvement in performance using the new control scheme compared to the existing dissolved oxygen feedback controller resulted in a 20% reduction in air flowrate. It is estimated the new strategy would give a payback period of less than 15 months.