Membrane-based Enthalpy Exchanger: material considerations and clarification of moisture resistance

The fundamental dimensionless groups for coupled heat and moisture transfer in a cross flow air-to-air enthalpy exchanger with hydrophilic membrane cores are derived and validated with experimental data. The thermal and moisture transfer mechanisms in membranes are studied. The finite difference numerical solutions of the model are used to study heat and moisture transfer in enthalpy exchangers. The variations of sensible, latent, and enthalpy effectiveness with various operating parameters are calculated for different types of material. Studies show that the sensible effectiveness is mainly determined by number of transfer units (NTU) of the exchanger, while the latent effectiveness is influenced by both the material and the operating conditions. Unlike thermal diffusive resistance, the moisture diffusive resistance in membrane is not a constant. It is co-determined by the slopes of sorption curves and the operating conditions. To account for these influences, a new dimensionless factor named the coefficient of moisture diffusive resistance (CMDR) is defined. With this coefficient, the performance of an enthalpy exchanger can be more easily predicted and clearly understood. By comparing the performances with different membrane materials, it is revealed that the membrane material with a linear sorption curve performs better than other materials under common conditions.     

Thermochemical kinetics of the formation of supramolecular compounds of amino acids with carboxylic cation exchangers

The kinetics of sorption of glycine and methionine from aqueous solutions with various acidities on the carboxylic cation exchangers KB-2 and KB-4 in protonated, deprotonated, and copper forms at 298 K was studied by microcalorimetry. In the sorption of the amino acids on the copper forms of the cation exchangers, the heat flux changes its sign. The character of the aliphatic amino acid-carboxylic cation exchanger interparticle interaction depends on the ionic form of the cation exchanger. As determined by the sorption method and IR spectroscopy, the nature of the glycine and methionine sorption sites in the ion exchanger phase changes on passing from the protonated to the copper form of the sorbent.     

Energetic analysis of an air handling unit combined with enthalpy air-to-air heat exchanger

The energetic analysis of an air handling unit (AHU) combined with an enthalpy air-to-air heat exchanger has been studied to improve the first law thermodynamic efficiency. The energy balance equations for enthalpy air-to-air heat exchanger, conditioned space, heating coil, cooling coil and mixing box have been performed and solved based on a program developed in Engineering Equation Solver. The results showed that using an enthalpy air-to-air heat exchanger leads to energy recovery which in turn decreased the total required AHU power. The effect of using an enthalpy air-to-air heat exchanger on recovered energy in hot and humid ambient is more than the cold and dry one. Using the enthalpy air-to-air heat exchanger, the cooling coil load decreases by 28.27%, which in turn increases the first law efficiency by 32.8%.

     

换热器与相变材料的兼容性研究进展

相变材料是一类以潜热实现能量存储释放的储能材料,由于其在相变温度附近具有很大的储热密度,相变材料可以被用于建筑控温、太阳能热发电和高温传热蓄热等应用中。 换热器是相变储能设备的重要组成部分,可以将热量在供需两端进行传递和转移,保障需求一方的使用,随着相变材料研究的不断深入及其工程应用的广泛普及,换热器已在众多相变储能项目中发挥了重要的枢纽作用。 为了保证换热器的使用性能,需要对换热器在相变材料中的防腐蚀性进行全面的分析。 本文总结了大量国内外的文献,分析不同成分的相变材料对换热器材料的腐蚀性,为换热器材料的选择提供了参考。     

Effective waste heat recovery from engine exhaust using fin prolonged heat exchanger with graphene oxide nanoparticles

Waste heat recovery is an important alternative to reduce the energy consumption in industrial processes. Heat Exchangers are used effectively for heat recovery. Thus, the role of heat exchangers for waste heat recovery system is crucial. The exclusive of heat transmission of a heat exchanger can be improved by many methods such as by modifying the geometries and using nano-additives of different concentration. In this continuation, a modified geometry of finned heat exchanger is developed with CFD analysis. Modified heat exchanger includes the fins in the internal pipe to improve heat transfer. Nanoparticles of graphene oxide with various concentrations are introduced in working fluid. A steady numerical study is performed by using ANSYS Fluent with k-omega turbulence model for exhaust flow. Variation at inlet velocities of exhaust gas and water, particles concentration and internal fin geometry are considered. The reduction in hot fluid temperature from 6 m/s to 2 m/s enhanced the effectiveness by approximately 33.3%. The decrease in hot fluid velocity to 2 m/s and 6 m/s can reduce its outlet temperature by 100 K and 14 K at 0.03 m/s cold fluid temperature. The inclusion of nanoparticles at 0.1% can enhance the effectiveness by maximum of 7%.     

A detailed insight into the optimization of plate and frame heat exchanger design by comparing old and new generation metaheuristics algorithms

The voluminous utilization and application of plate and frame heat exchangers (PFHE) in many industries has accelerated the consumer and designer both to optimize exchanger total cost. Over the last few years, several old and new generation algorithms were employed and exploited to optimize PFHE cost. This study explores the application and performance of three new-generation algorithms Big Bang-Big Crunch (BBBC), Grey Wolf Optimizer (GWO), and Water Evaporation Optimization (WEO) in designing optimally PFHE. Besides, this study also compares the performance of three well-established old generations algorithms namely genetic algorithm (genetics and natural selection), particle swarm optimization (animals behaviour), and differential evolution (population-based) with the above three new algorithms in the optimization of PFHE.Seven design factors are chosen for PFHE optimization: exchanger length on hot and cold sides, height and thickness of fin, length of the fin-strip, fin frequency, and the number of hot side layers. The applicability of the suggested algorithms is assessed using a case study based on published research. Though DE performs the best in this study of design optimization concerning total cost and computational time, the three new-generation meta-heuristic algorithms BBBC, GWO, and WEO also provide the novel scope of application in heat exchanger design optimization and successfully finding the cost of the heat exchanger. According to this study, capital costs increase by 19.5% for BBBC, 24% for GWO, and 7.6% for GWO, but operational costs fall by 9.5% for BBBC and GWO when compared to the best performing algorithm (DE). On the other hand, WEO shows an increase of 32.6% in operational costs. Aside from that, a full analysis of the computing time for each algorithm is also provided. The DE has the quickest run time of 0.09 ?s, while the PSO takes the longest at 33.97 ?s. The rest of the algorithms have nearly identical values. As a result, a good comparison is established in this study, offering an excellent platform for designers and customers to make selections. Additionally, the three new generations algorithms mentioned here were not used earlier for optimization of PFHE and the comparative study illustrates that each of them possesses eat potential for cost optimization and also solving other complex problems.     

Sorption of Sc(III) on phosphorus-containing cation exchangers

Kinetics of Sc(III) sorption from hydrochloric acid solutions on KRF-20t-60 cation exchanger is studied. The experimental data are analyzed in terms of the gel and film kinetic models. The Sc(III) diffusion coefficient in the resin phase is estimated. Static and dynamic sorption data are obtained on Sc(III) sorption from various process solutions on KRF-20t-60, PA-1, AFI-22 ion exchangers, and also on ion exchangers supported on polyacrylonitrile-based fibrous material. Desorption of Sc(III) from KRF-20t-60 is also studied.     

Some thermodynamic peculiarities of the nonexchange sorption of phenylalanine on dissimilar anion exchangers

It is shown that the nonexchange sorption of phenylalanine on dissimilar anion exchangers occurs by the same mechanism, determined by the structure of the amino acid, while the absorbed amount of substance depends on the sorbent structure. It is established that the micelle formation and the phenylalanineanion exchanger sorption equilibrium depend on the amount and nature of functional groups in anion exchangers. It is shown that, in the systems under investigation, the nonexchange sorption constant is determined by the constant of phenylalanine micelle formation.     

Mechanism of metal-ion sorption on hydrous metal oxides

A model for treating the sorption of metal ions on hydrous metal oxides was established based on the assumptions that these materials are weakly acidic cation exchangers and have a discrete exchanger phase. The experimental results of the sorption of metal ions on the hydrous niobium(V) and tin(IV) oxides are found to be consistent with the formulas derived from the model by considering that the charge balance and the mass action law hold in the exchanger phase and cations are sorbed by the distribution between this phase and the bulk aqueous phase.     

Hydration and sorption characteristics of a polyfunctional weak-base anion exchanger after the sorption of vanillin and ethylvanillin

Features of the sorption of substituted aromatic aldehydes by a weak-base anion exchanger under equilibrium conditions are investigated using vanillin and ethylvanillin as examples. Analysis of the sorption isotherms of carbonyl compounds at different temperatures allows us to calculate the equilibrium characteristics of their sorption and assess the entropy and enthalpy contributions to the energy of the process. Hydration characteristics of the macroporous weak-base anion exchanger before and after the sorption of aromatic aldehydes are compared.     

Simulation of temperature and moisture fields around a single borehole ground heat exchanger: effects of moisture migration and groundwater seepage

This paper aims to investigate the effects of moisture migration and groundwater seepage on the heat transfer capacity of ground heat exchangers in stratified soils. A three-dimensional unsteady groundwater flow and heat transport model was established using finite volume method. Sixteen cases with different model considerations and initial soil conditions were simulated based on the proposed model. A group of 8 cases considering only transverse moisture migration and another group considering both transverse and longitudinal moisture migration were compared. The heat and moisture fields after 30 days of operation reveal that considering the change of saturation caused by vertical moisture transfer, the soil temperature field will be affected, but borehole outlet temperature was less influenced. The absolute value of outlet temperature difference between corresponding cases in the two groups is only about 0.2 °C. The position of groundwater seepage and arrangement of unsaturated soil layers with different degrees of saturation on heat transfer capacity of vertical ground heat exchanger were further explored. The results show that the longitudinal moisture migration would be made more influential by the existence of seepage layer, because the average relative deviation of inlet and outlet temperature difference between the corresponding cases of Group 1 and Group 2 was 1.34% when setting seepage layer and was 0.44% when without seepage layer. Heat transfer performance of borehole heat exchanger is also affected by the location of seepage layer. The average relative deviation of inlet and outlet temperature difference between the reference case and cases with seepage in the top, middle and bottom layers is 34.18%, 25.08% and 16.82%, respectively. The arrangement of unsaturated soil layers also has a certain effect. When the soil layer with low degree of saturation is located in the upper layer of soil, heat transfer capacity is better.

     

Simultaneous purification of sewage from Cd(II) and nonionic surfactant with cation exchanger

The sorption of nonionic surfactant (alkylmonoethers ALM-10), taking place simultaneously with the sorption of Cd(II) in H-form of polyacrylic cation exchangers KB-2 and KB-2-12P was investigated. Increasing the sorption of surfactant the decrease in both the stability of Cd(II) complex with cation exchanger and the equilibrium sorption of Cd(II) was observed. The isotherms of the sorption were measured; the coefficients of intraparticle diffusion (D) were calculated. The integration of the filter filled with polyacrylic cation exchanger into the system of sewage purification is suggested.     

Preparation of Anion Exchanger for High-Efficiency Purification of Halogen-substituted Hydrocarbon Solvents Used To Clean Metal Optics

Phenomenon of rising sorption capacity of AV-17-8 anion exchanger upon an increase in its humidity due to the superequivalent absorption of Cl^– ions was revealed and substantiated. The purification of halogensubstituted hydrocarbon solvents to remove acids under dynamic conditions by the ion-exchange method and the dynamics of sorption by anion exchangers of halogen-substituted solvents from model solutions were studied. It was shown that AV-17-8 anion exchanger is stable in halogen-substituted solvents and, when present in the OH–form, raises their stability against destruction, and the equilibrium sorption capacity of the anion exchanger is 2–3 times its exchange capacity.     

Ion exchange extraction of platinum(IV) and palladium(II) from hydrochloric acid solutions

Sorption concentration of platinum(II, IV) and palladium(II) from freshly prepared and aged two-yearold hydrochloric acid solutions by a series of anion exchangers with different functional groups and of different physical structure of Purolite and CYBBER grades was studied. The high sorption ability of the ion exchangers in relation to the extracted chlorocomplexes of noble metals is shown. It was demonstrated that palladium(II) from all tested ion exchangers can be completely desorbed with thiourea solutions acidified with hydrochloric acid, while complete desorption of platinum is achieved only from Purolite S 985 anion exchanger of the complexforming type and Purolite A 111 weak base anion exchanger.     

The chemical precipitation of nickel on ion exchangers and active carbons

The chemical precipitation of nickel in the form of poorly soluble precipitates in ion exchanger matrices and on active carbons from solutions of nickel chloride and chemical nickel plating electrolytes was studied. The sorption of nickel ions from a solution of nickel chloride occurs most effectively on Purolite D24002 macroporous chelate forming ion exchanger, KU-23-15/100 sulfo cation exchanger, and KU-2-8 gel sulfo cation exchanger. Nickel enters sulfo cation exchangers in the form of counterions, and is adsorbed on Purolite D24002 largely because of complex formation. The subsequent precipitation of nickel in the solid state in matrix pores liberates ionogenic centers, which allows repeated sorption cycles to be performed. After three chemical precipitation cycles under static conditions, the amount of nickel is higher by 170–250% than the ion exchange capacity of the sorbents. The electrolyte of chemical nickel plating contains nickel predominantly in the form of negatively charged and neutral complexes with glycine, which cannot form bonds with the matrices under study. It is therefore reasonable to perform sorption at decreased solution pH values.     

Physicochemical basis of the ion-exchange separation of gold cyanide complexes

The mechanism of the separation of gold cyanide complexes is discussed, along with ion exchanger selection, selectivity, elution, and industrial applications. The ion-exchange mechanism for the sorption of gold cyanide complexes is established, and a criterion is suggested for selecting the anion exchanger for their extraction (specifically, the pK _a of the anion exchanger). The selectivity of the sorption of gold cyanide complexes by anion exchangers with rarely distributed ionogenic groups is demonstrated. A procedure for the elution of gold cyanide complexes using alkaline solutions is developed.     

Sorption of Some Metal Ions on Inorganic Electron and Ion Exchangers Based on Zirconium(IV)

Conditions of sorption of nonferrous metal ions on inorganic electron and ion exchangers based on zirconium(IV) were analyzed. The sorption capacity was evaluated as influenced by pH, concentration, and temperature of the contacting solutions and nature and chemical composition of the ion exchanger.     

Leak detection in a high-pressure heat exchanger system in a refinery using radiotracer technique

A radiotracer investigation was carried out in a diesel hydrotreater (DHDT) unit in a refinery for leak detection in a breech-lock heat exchanger system. The main objectives of the study were to identify the leaking heat exchanger in a system with six heat exchangers and estimate the leak rate. Bromine-82 as dibromobiphenyl was selected and used as radiotracer for the investigation. The radiotracer was instantaneously injected into the suction end of the feed pump line to the heat exchanger of the DHDT unit. The movement of the tracer was measured at strategically selected locations using NaI(Tl) scintillation detectors. Based upon the results of the radiotracer investigation, it was found that out of six heat exchangers, exchanger E-1F was leaking.     

Potentialities of fibrous ion-exchange materials in the determination of sulfate ions by color reactions of barium with organic reagents on a solid phase

The possibility of the determination of sulfate ions with the use of fibrous materials filled with ion exchangers on the basis of color reactions of barium with the organic reagents Arsenazo III, Orthanilic B, and Orthanilic K on a solid phase was examined. A polyacrylonitrile fiber filled the cation exchanger KU-2; anion exchangers AB-17, A-5, ANKF-211, and EDE-10p; and polyampholyte ANKB-50 (PANV-ANKB-50) was used as the support. The study of the different techniques of the sorption of the reaction components demonstrated the efficiency of the two systems involving PANV-ANKB-50. The determination of sulfates is possible because of the sorption of the excess barium remaining after the reaction with sulfate ions in the solution and its detection on the solid phase with a solution of Arsenazo III or the detection of the excess barium remaining after the interaction with the solution of sulfate ions on the solid phase with a solution of Orthanilic K. The calibration plots are linear in the concentration range of sulfate ions 10^?4–10^?5 M.     

The nonexchange sorption of histidine by low-basicity anion exchangers

The experimental data showed that the nonexchange absorption of histidine by AN-221, AN-251, AN-31, and EDE-10P anion exchangers in the HCl form depended on the structure of the anion exchanger. The activity coefficients of the components of the sorbent phase, thermodynamic equilibrium constants, and standard Gibbs energies of nonexchange sorption of histidine by the low-basicity anion exchangers were calculated and discussed.