Various methods for achieving dropwise condensation were reviewed from the point of view of surface science. A new method for obtaining drop-wise condensation was presented. The concept of this new method was further confirmed through systematically experimental studies. The surfaces of stainless steel and copper tubes employed for dropwise condensation studies were treated with various surface techniques. Steam condensation under atmospheric pressure was carried out on these surfaces and steady duopwise condensation was observed. Experimental results and photographs of dropwise condensation were presented. The characteristics of dropwise condensation formed on specially treated surfaces was investigated and discussed.

Ion-plating and ion-beam mixing combination technology was employed to prepare surface alloys on copper tubes. Elements chosen for the purpose include Cr, Fe, Al, N, Bi, Sb, Sn, Se, and In. Experimental results of steam condensation on the external surface of the vertical copper tubes were obtained. The surface characteristics of the Cu-Cr and Cu-Fe alloy surfaces were analysed by using XPS, AES and AES-PRO of PHI-550 Multiple Function Electronic Spectroscopy. The mechanism for dropwise condensation formed on the new surfaces was presented.

Heat transfer characteristics of the new surfaces were determined through temperature measurement, and the results obtained were compared with dropwise condensation studies from various sources. The differences in heat transfer between Cu-Cr and mechanical polishing surfaces were discussed. Life-time experiments were conducted on both Cu-Cr surface and mechanical polishing surface. Perfact dropwise condensation gave a life-time of over 8500 hours.

A mathematical model for evaluating the separation performances of hollow fiber membrane N2-H2 permeators has been established. The effects of operating parameters and membrane characteristics on the concentration of hydrogen in the permannte gas and the percentage recovery of hydrogen have been studied with the help of a digital computer using this mathematical model. Results computed are compared with data obtained from field tests of three φ100 × 3000mm full-scale permeators, confirming the adaptability of the mathematical model.

Vertical thermosyphon reboilers sufferd seriously from being unstable. The problem can be solved by a newly developed internal thermosyphon re-boiler. Experiments were carried out in both quartz and copper tubes of similar geometrical dimensions. The former allowed better visual observation and the latter gave more quantitative informations. Water, sulfuric acid, tri-ethanolamine, heavy oil, ethanol-water, methanol-ethanol, ethanol-propanoland other mixtures were used as working media. Particles of polypropene, with densities approaching that of water were used as tracer in the water system for the investigation of the flow characteristics. Rate of circularion, flow patterns, rate of heat transfer and fouling were studied. A flow model and a design approach were proposed. Calculated results could be used to predict the characteristics of a two-phase flow and its heat transfer within the reboiler.

Bubble formation frequencies in a single-orifice two-dimensional gas-solid fluidized bed(292mm × 16mm) were measured by means of a high sensitivity capacitance probe. A spectrum analyzer was used to analyze the bubble frequency distribution. The effects of various parameters on the bubble frequency power spectrum density were investigated. The following parameters were included: particle size(0.105-0.590mm), particle density (590-2990kg/m3), minimum fluidization velocity of particles (0.0072-0.481m/s), initial bed height (205-565mm), distance of probe above orifice, flow rate at orifice (0.5-35 × 10-4m3/s) and background fluidizing gas flowrate (0-3 times of minimun fluidization velocity). For a fluidized bed with small particles of low densities, the bubble formation frequency conformed very well with the Davidson and Harrison model. A regular deviation from the model was observed with increases in particle sizes and densities. A modified model taken into account, for the gas leakage from forming bubbles into the surrounding emulsion phase, when dealing with larger particles, was presented. The modified leakage model proved to agree with the experimental results obtained.

Continuous and dense Mg-MOF-74 membranes were prepared through a combined layer-by-layer seeding assembling and secondary growth method based on 2, 5-dihydroxybenzoic acid and magnesium acetate solution. The adhesion between Mg-MOF-74 crystals and a-Al₂O₃ support could be considerably improved by the alternate immersion assembling of 2, 5-dihydroxybenzoic acid and magnesium acetate solution. Compared with the in-situ crystallization technique, Mg-MOF-74 membranes synthesized by four-cycle layer-by-layer method exhibited improved molecule-sieving properties due to optimized membrane continuity and density. Single gas test indicated that the best Mg-MOF-74 membrane had H₂/CO₂ ideal selectivity as high as 8.96, higher than its Knudsen diffusion selectivity. XRD measurement proved that the XRD patterns of Mg-MOF-74 membranes were consistent with those of powdered Mg-MOF-74 from published papers, which implied that our membranes were composed of randomly oriented MOF-74 crystals. SEM characterization showed that the MOF-74 crystals possessed wheat-shaped morphology and specific BET surface area as high as 1182 m²·g^-1.

The ultrasonic degradation reactions of methyl cellulose (MC) in its aqueous solution under different conditions were studied. It was found that the degradation reactions are of a mechanochemical nature and the degradation rate is not an increasing function of irradiating time. The ultrasonic irradiation of MC and acrylonitrile (AN) in H2O/HCOOH resulted in a copolymer of MC and AN. A method for preparing the water-soluble copolymer was suggested. The copolymer is both block and graft with joints mainly located on methoxy groups of MC. This was elucidated by the character of the copolymerization reaction and by analysing the copolymer structure with the help of DTA, IR, PGC and MS.The state of molecular aggregation of the copolymer was identified by XRD and SEM. The surface activety, thermostability, and resistance to salt in the aqueous solution of the copolymerization product were examined. They were found to be better than those of MCs.

A binary mixture of N, N-dimethylaniline(DMA) and benzyl chloride(BzCl), or ammonium salts of such compounds, are capable of initiating free radical polymerization reactions of vinyl monomers. Such initiating techniques had been employed for modifying cellulose through graft copoly-merization reactions. Further investigation was conducted on the initiative charactertics of such a system. A dilatometric method was used to measure the polymerization rate(Rp) of methyl methacrylate(MMA) (degassed under high vacuum) in benzene solvent at 60℃. Results obtained were as follows: and Rp∞[I], (when [DMA] = [BzCl] =[I]) Also, RP∞[BzCl]1/2, (when [DMA] = constant). The kinetic rate equation has been obtained: The effects of substituted groups at the benzene ring of DMA on the polymerization rate were also studied.It is found that when the electron-withdrawing groups were attached on the benzene ring of DMA, then the Rp of MM A initiated by them would drop down. The effects of such electron-withdrawing groups could be described by the Hammett equation.

An analysis of separation costs supported the arguments of the claim that the separation sequence and heat-exchanger network could be determined separately. Based on this understanding of the problem, a new synthesis method was presented in this paper. First the optimal and near-optimal unintegrated sequences was found by means of the branch and bound strategy, and then the heat exchanger network was established by using 0-1 programming for each sequence. The sequence with minimal total separation cost defined the optimal energy-integrated distillation flowsheet. Computation efforts were considerably reduced, and the whole synthesis procedure could be accomplished on a microcomputer.

Forced convective heat transfer under steady flow in a helical recuperator is being studied, employing similanity principles. Water, glycerin-water solution and air are used separately as medium for heat transfer, and Convective heat-transfer coefficients are determined over a rather wide range of Dean number and Prandtl number. The correlations among Nusselt number, Dean number and Prandtl number are found by the least squares method: Nu = 1.2Dn0.53Pr0.29; Dn = 2250-16500, Pr=2.5-8.5 Nu = 0.23Dn0.64Pr1/3; Dn = 2900-9000, Pr=0.7 At the same time, the modified graphical method of wilson is used to determine the individual convective heat-transfer coefficients in the recuperator, and it is found results that they agree satisfactorily with experimental.

Experiments are conducted to reveal and compare the effects of surface tension gradients on the mass transfer performance of columns packed re -spectively with three types of packing materials. The results obtained show that surface tension gradients have evident influence on the three types of packings, though in different extents. Theoretical studies of the effect of surface tension gradients on the wetted area of packing, leads to a new Ma-rangoni number, i. e. which may serve to explain the influence of surface tension gradients. The relationship between the wetted area and St has also been determined quantitatively.

The characteristics of a 60 mm I. D. fluidized bed with baffles are studied using particles belonging to group B in Geldarts classifcation. Experimental results of pressure drop, pressure drop fluctuation bed expansion and RTD of gas show that the behavior of fluidization varies with changing gas velocity. Apparently it can be devided into two regions, i. e. bubbling and turbulent regions. It is suggested that a critical point exists between the bubbling and the turbulent regions, this point may be referred to as the critical turbulent fluidized point. The critical turbulent fluidization velocity un corresponding to this point can be expressed by the following equation: Ren = 0.1358p?6576GaP0.5120 inwhich, Ren=undppf/μ;Gap=dp3Pf2g/μ2; ρ=ρs/ρf This equation can be used as a criterion for the static turbulent fluidization region in fluidized beds with baffles. Its error is less than 10%.

By employing the equation relating the viscosity of a binary mixture to its excess Gibbs free energy as proposed in part ( I ) of this series of papers, and by correlating viscosity data with McAillisters multi-bodg interaction model, calculation of vapor-liquid equilibrium data has been made for 9 binary systems, among which 3 are alcoholic organic ones and 1 is alcoholic aqueous. Calculated values are compared with corresponding experimental data. Except for one system showing relatively high deviation, the root mean square deviations of the bubble points and the vapor phase compositions of all systems are 0.09-0.80℃ and 0.003-0.038respectively.

A method is presented for the estimation of parameters in non-linear reaction systems by using the shifted Legendre polynomial procedure. The method is simple and straightforward. Illustrative examples are presented.

Lead-calcium intermediate alloy was prepared by fused salt electrolysis and further smelled into commercial alloys suitable for positive and negative grids of maintenance-free lead-acid batteries. Necessary protective measures were taken to ensure the Ca-contents in the alloys. The mechanical properties and corrosion resistance of various alloys of different compositions were determined. Electron-beam microprobe analysis and metallographical analysis were carried out to obtain suitable recipes and to explain the effect of Ca-content on the alloy performance.