空气与水逆流直接接触热质交换过程模型计算及分析

Based on reasonable model hypotheses and the energy analysis of heat and mass transfer of air and water in a direct contact counter flow, a set of general equations that can describe the internal relationship between the state parameters of air and water and dimensionless parameters of transfer process are given. A method utilizing MATLAB to solve these general equations is also proposed. Calculations and analysis with the model of a cooling- dehumidifying process give a consistent result with that of previous experiment. A new method for designing equipment such as evaporating cooler and cooling tower, and for analyzing experiment data of heat and mass transfer of air and water in a direct contact counter flow can be derived from this study.     

反式-1,2-环基二醇+乙酸丁酯+水三元体系固液相平衡(英文)

Using a laser observation technique,the solubilities of trans-1,2-cyclohexanediol in butyl acetate+wa- ter were measured at the temperature range from 298.15K to 323.15K by a synthetic method at atmospheric pres- sure.It is shown that the solubilities of trans-1,2-cyclohexanediol in butyl acetate+water were affected greatly by the proportion of butyl acetate and water,and presented maximum value at given temperature.The UNIFAC model was used to correlate the experimental data.The average relative deviation(ARD)between experimental and calculated values is 3.03%.     

Solid-Liquid Equilibria of trans-1,2-Cyclohexanediol＋Butyl Acetate＋ Water Ternary System

Using a laser observation technique,the solubilities of trans-1,2-cyclohexanediol in butyl acetate＋wa- ter were measured at the temperature range from 298.15K to 323.15K by a synthetic method at atmospheric pres- sure.It is shown that the solubilities of trans-1,2-cyclohexanediol in butyl acetate＋water were affected greatly by the proportion of butyl acetate and water,and presented maximum value at given temperature.The UNIFAC model was used to correlate the experimental data.The average relative deviation（ARD）between experimental and calculated values is 3.03%.     

带增湿区的质子交换膜燃料电池

Water management is of great importance to maintain performance and durability of proton exchange membrane fuel cells. This paper presents a novel proton exchange membrane (PEM) fuel cell with a humidification zone in the membrane electrode assembly (MEA) of each cell, in which the moisture of the cathode exhaust gas could transfer through the membrane to humidify anode or cathode dry gas. With a simple model, the relative humidity (RH) of the dry air exhaust from a membrane humidifier with 100% RH stream as a counter flow is calculated to be 60.0%, which is very close to the experimental result (62.2%). Fuel cell performances with hydrogen humidifying, air humidifying and no humidifying are compared at 50, 60 and 70˚C and the results indicate that humidifying is necessary and the novel design with humidifying zone in MEA is effective to humidify dry reactants. The hydrogen humidifying shows better performance in short term, while water recovered is limited and the stability is not as good as air hu-midifying. It is recommended that both air and hydrogen should be humidified with proper design of the humidifying zones in MEA and plates.     

丙烯在仲丁醇-水溶液中溶解度的测定与关联

In order to obtain solubility data of propylene in 2-butanol water solutions, gas-liquid equilibrium(GLE) experiment was carried out at 303.15--333.15 K, 0.3-1.2 MPa with static equilibrium still. Original mass ratios of 2-butanol to water are 1:0，9:1,8:2 and 7:3, respectively. The equilibrium data are correlated with an empirical correlation. The average relative deviation (ARD) between experimental and calculated values is 2.15%,and the maximum relative deviation (MRD) is less than 5%.     

Heat transfer model of two-phase flow across tube bundle in submerged combustion vaporizer

In order to optimize the design of the submerged combustion vaporizer(SCV), an experimental apparatus was set up to investigate the heat transfer character outside the tube bundle in SCV. Several experiments were conducted using water and CO_2 as the heat transfer media in the tubes, respectively. The results indicated that hot air flux, the initial liquid level height and the tube pitch ratio had great influence on the heat transfer coefficient outside the tube bundle(ho). Finally, the air flux associated factor β and height associated factor γ were introduced to propose a new hocorrelation. After verified by experiments using cold water, high pressure CO_2 and liquid N_2 as heat transfer media, respectively, it was found that the biggest deviation between the predicted and the experimental values was less than 25%.     

Determination and correlation solubility of m-phenylenediamine in (methanol,ethanol, acetonitrile and water) and their binary solvents from 278.15 K to 313.15 K

In this study, the solubility of m-phenylenediamine in four pure solvents(methanol, ethanol, acetonitrile and water) and three binary solvent(methanol + water),(ethanol + water) and(acetonitrile + water) systems were determined in the temperature ranging from 278.15 K to 313.15 K by using the gravimetric method under atmospheric pressure. In the temperature range of 278.15 K to 313.15 K, the mole fraction solubility values of m-phenylenediamine in water, methanol, ethanol, and acetonitrile are 0.0093–0.1533, 0.1668–0.5589,0.1072–0.5356, and 0.1717–0.6438, respectively. At constant temperature and solvent composition, the mole fraction solubility of o-phenylenediamine in four pure solvents was increased as the following order:water b ethanol b methanol b acetonitrile; and in the three binary solvent mixtures could be ranked as follows:(ethanol + water) b(methanol + water) b(acetonitrile + water). The relationship between the experimental temperature and the solubility of m-phenylenediamine was revealed as follows: the solubility of mphenylenediamine in pure and binary solvents could be increased with the increase of temperature. The experimental values were correlated with the Jouyban–Acree model, van't Hoff–Jouyban–Acree model, modified Apelblat–Jouyban–Acree model, Sun model and Ma model. The standard dissolution enthalpy, standard dissolution entropy and the Gibbs energy were calculated based on the experimental solubility data. In the binary solvent mixtures, the dissolution of m-phenylenediamine could be an endothermic process. The solubility data,correlation equations and thermodynamic property obtained from this study would be invoked as basic data and models regarding the purification and crystallization process of m-phenylenediamine.     

An experimental study on the choked flow characteristics of CO2 pipelines in various phases

High pressure pipeline transportation has been an established technology for economically transporting large amounts of CO_2. However, there are still issues and associated risks that have to be effectively addressed and adequately understood. It is well known that a strong Joule-Thomson Cooling effect can occur when pressurized CO_2 flows through a choke valve. Thus, to investigate the choking characteristics especially the temperature drop of high pressure CO_2, a new laboratory scale experimental setup(total length of 14.85 m and the inner diameter of 15 mm) was constructed. Steady choked flow and transient choked flow tests were carried out respectively for pressurized CO_2 in various initial phases. The phase transitions and temperature drop characteristics were then studied following the choked flow and the results show that the phase transitions in steady choked flow differs significantly from that in transient choked flow. For transient choked flow of various initial phases, all the flows downstream would transfer from single phase to gas–liquid two-phase flow. Furthermore, the effect of water on transient choked flow of supercritical CO_2 pipeline was investigated, and the phenomena of solid particles deposition was captured which was paramount importance of ensuring the safety operation of CO_2 pipelines when throttling by the choke valves.     

轴向流固定床内流场的数值模拟与实验验证

The computational fluid dynamics model with porosity and drag coefficient was used to describe fluid flow in an axial flow fixed bed according to the characteristics of fluid flow in the fixed-bed of the reactor. The commercial computational fluid dynamics (CFD) code CFX was used to simulate the flow field in the axial flow fixed bed. The simulation predictions are in good agreement with experimental results of a large cold model. The influence of gas distributor on the flow field in the axial flow fixed bed was studied. A suitable gas distributor was used to attain less than 0.06 kPa radial pressure difference and less than 5.2% radial velocity difference in fixed bed.     

273.15-303.15K下尼扎替丁在甲醇-水、乙醇-水和异丙醇-水中的溶解度(英文)

The solubilities of nizatidine in methanol + water, ethanol + water and i-propanol + water mixtures were determined in the temperature range from 273.15 K to 303.15 K at atmospheric pressure by a static analytical method. The general single model was used to correlate the experimental data, which fits the data very well.     

SIMULATION OF PLUM DRYING IN DEEP BED

Thin layer air drying of plum was studied. The drying conditions in this study are : dry bulb temperature ranging from 60 to 100 °C, air moisture content ranging from 0.008 to 0.089 kg water/kg dry air and air velocity ranging from 0.5 to 2 1x11s. An exponential model was used to describe the drying curve. The heat and moisture balances on the air were used to calculate the outlet air temperature and its moisture content. The heat balance on the product was used to calculate the product temperature. These equations were used to predict the drying of plum in deep bed. A good agreement between the experimental and calculated product moisture content, the product temperature and the outlet air temperature were obtained     

SIMULATION OF PLUM DRYING IN DEEP BED

Thin layer air drying of plum was studied. The drying conditions in this study are : dry bulb temperature ranging from 60 to 100 °C, air moisture content ranging from 0.008 to 0.089 kg water/kg dry air and air velocity ranging from 0.5 to 2 1x11s. An exponential model was used to describe the drying curve. The heat and moisture balances on the air were used to calculate the outlet air temperature and its moisture content. The heat balance on the product was used to calculate the product temperature. These equations were used to predict the drying of plum in deep bed. A good agreement between the experimental and calculated product moisture content, the product temperature and the outlet air temperature were obtained     

SPRAY DRYING DYNAMIC MODELING WITH A MECHANISTIC MODEL

In this work we suggest the dynamic modeling of a spray dryer considered as a series of well-stirred dryers. That is, a series of dryers in which the output variables are equal to the state variables. The state equations were obtained from the heat and water mass balances in product and air. Additionally, heat and water mass balances in interface jointly with water equilibrium relation between product and air were considered. A pilot spray dryer was modeled assuming one, two, five and 20 well stirred steps. Low-fat milk with 10-20% of solids was dried at different inlet air temperatures (120-160°C), air flow rate of 0.19 kg dry air s^-1 and different feed rates (1.4 - 4.2 × 10^-4 kg dry solids s^-1). Stationary result showed that the model predicts the experimental air outlet temperature, at different inlet conditions with a maximum deviation of 6°C. The dynamic simulation reproduce the experimental one with moderate accuracy. Experimental dynamic showed that the pilot plant spray dryer has a well-stirred process behavior. The model represents a method for estimate outlet product moisture as function of the outlet air temperature. This has application for automatic control because there is not an easy way to measure on-line measure the outlet product moisture content.     

SPRAY DRYING DYNAMIC MODELING WITH A MECHANISTIC MODEL

ABSTRACT

In this work we suggest the dynamic modeling of a spray dryer considered as a series of well-stirred dryers. That is, a series of dryers in which the output variables are equal to the state variables. The state equations were obtained from the heat and water mass balances in product and air. Additionally, heat and water mass balances in interface jointly with water equilibrium relation between product and air were considered. A pilot spray dryer was modeled assuming one, two, five and 20 well stirred steps. Low-fat milk with 10–20% of solids was dried at different inlet air temperatures (120–160°C), air flow rate of 0.19 kg dry air s^?1 and different feed rates (1.4 ? 4.2 × 10^?4 kg dry solids s^?1). Stationary result showed that the model predicts the experimental air outlet temperature, at different inlet conditions with a maximum deviation of 6°C. The dynamic simulation reproduce the experimental one with moderate accuracy. Experimental dynamic showed that the pilot plant spray dryer has a well-stirred process behavior. The model represents a method for estimate outlet product moisture as function of the outlet air temperature. This has application for automatic control because there is not an easy way to measure on-line measure the outlet product moisture content.     

新型闭式冷却塔传热传质的实验研究

建立了椭圆管式闭式冷却塔的实验测试平台,通过改变管内水进口温度和流量、空气质量流量、空气干湿球温度、喷淋水流量等以测试其传热性能,采用Poppe和Dreybal的假设处理数据,得到了管外水膜对流传热系数和水膜与空气传质系数,实验结果表明:水膜传热系数是空气质量流量和喷淋水温度的函数,与已知文献中Mizushina,Ni...     

Surface temperature of acoustically levitated water microdroplets measured using infra-red thermography

A 58 kHz acoustic levitator was fitted with an infra-red thermography camera to examine the drying behaviour of water microdroplets at various drying-air temperatures. The evaporation rate was greater with larger initial droplet size at otherwise identical drying-air temperature (T_da). Measurement of droplet aspect ratio indicate that this is caused by differing acoustic field strengths. The measured droplet surface temperature in dry air showed no dependence on initial droplet size, but deviated from the wet bulb and also from the droplet temperature predicted by acoustic levitation theory. The degree of deviation of drying rate from that predicted by the d²-law using the wet bulb was dependent on T_da. Use of measured droplet surface temperature instead of the wet bulb gave, however, good agreement with the d²-law in dry air. No substantial effects of acoustic field streaming on drying rate could therefore be seen, even at the sound pressure levels of 106-165 dB used. Interpretation of evaporation rates of acoustically-levitated droplets requires therefore the measured droplet surface temperature.     

Characterization of a Spray Drying System for Soymilk

ABSTRACT

Soymilk slurries were spray dried at various combinations of inlet air temperature (1255. 265, and 275°C), feed rate (0.38 and 0.57 Lpm), and atomizer speed (119,300 and 26,800 rpm). Monitored dryer parameters included dry and wet bulb temperaturea of ambient and exhaust air, drying chamber's inlet and outlet air temperatures, product and feed temperatures, velocity pressure at exhaust pipe, atomizer speed, and feed rate. Weather data was included in the analysis.

Collected data was used to estimate the state of the outlet air using psychrometrics and assuming adiabatic saturation. Equations to predict outlet and product temperatures were developed. Average thermal and eveporative efficiencies were 65.9 and 78.4%. respectively.     

Ni载体整体煤气化链式燃烧联合循环性能

本文将具有分离CO₂的链式燃烧技术与整体煤气化联合循环(IGCC)技术结合，构成整体煤气化链式燃烧联合循环系统，对系统性能进行了模拟研究。结果表明，采用德士古气化工艺、空气反应器出口温度1200℃，NiO/NiAl₂O₄作载氧体，压气机压比17、补燃后透平初温(TIT)1350℃、冷却空气量12％时，系统净效率39.61% HHV（41.55%LHV），CO₂排放量126 g·kW^-1·h^-1。补燃温度1350℃，空气反应器温度由1000℃升高到1200℃，CO₂的回收率提高约23％，系统效率由40.3%降低到39.61％；补燃温度由1200℃提高到1500℃，系统净效率由37.4%增加到40.8%，CO₂的排放量从3g·kW^-1·h^-1增加到202 g·kW^-1·h^-1；补燃温度一定，压比增大，系统比功减小，CO₂排放量增加，效率先增大后减小，存在最佳压比.     

Characterization of a Spray Drying System for Soymilk

Soymilk slurries were spray dried at various combinations of inlet air temperature (1255. 265, and 275°C), feed rate (0.38 and 0.57 Lpm), and atomizer speed (119,300 and 26,800 rpm). Monitored dryer parameters included dry and wet bulb temperaturea of ambient and exhaust air, drying chamber's inlet and outlet air temperatures, product and feed temperatures, velocity pressure at exhaust pipe, atomizer speed, and feed rate. Weather data was included in the analysis.

Collected data was used to estimate the state of the outlet air using psychrometrics and assuming adiabatic saturation. Equations to predict outlet and product temperatures were developed. Average thermal and eveporative efficiencies were 65.9 and 78.4%. respectively.     

闭式冷却塔的计算模拟

分析了闭式冷却塔的传热传质机理,建立了其数学计算模型,求解沿塔高度方向的温度分布,采用一维和二维模型对比分析,一维模型每排管为一个单元,二维模型每排管分别划分4个、10个单元,利用Matlab编写圆管型闭式冷却塔程序,与Hasan的结果对比,管内冷却水沿塔高度的温度分布采用二维模型每排管划分4个单元和10个单元相比相差较小,二维模型比一维模型的管内冷却水温度分布更接近Hasan的结果;按二维模型每排管划分10个单元,采用Matlab编写圆管模拟程序,采用分段计算的方法预测冷却水出口水温,与实验结果相比,一致性较好。该模型可用来预测不同流速和不同室外空气状态下闭式冷却塔的出口水温和喷淋水水温。