Diffusion coefficients in strong aqueous amine solutions

We demonstrate an optimized two-step procedure for measuring the full complex coherence function. The measurement relies on a wavefront shearing interferometer that permits characterizing nonstationary fields over an extended angular domain. The accuracy of the coherence measurement was demonstrated by excellent agreement with theoretical predictions.

A method of measuring the second-order degree of coherence in an arbitrary plane by means of a compact wavefront shearing interferometer is described. The prism interferometer previously described by Saunders produces two sheared images that interfere, allowing measurement of the degree of spatial coherence. If the degree of coherence is a function of coordinate differences only, the visibility is constant; otherwise it varies over the field. Experimental results are given.

The values of the second dissociation constant, K2, and related thermodynamic quantities of the ampholyte bis[(2-hydroxyethyl)amino]acetic acid (BICINE) have been determined at temperatures from 5 to 55 ∘C. The pH values of six equimolal buffer solutions, and four buffer solutions having ionic strengths (I = 0.16 mol⋅kg−1) similar to those in blood plasma, have been evaluated at 12 temperatures from 5 to 55 ∘C using the Bates–Guggenheim convention. The liquid junction potentials (Ej) between the buffer solutions of BICINE and saturated KCl solution of the calomel electrode at 25 and 37 ∘C have been estimated by measurement with a flowing junction cell. These values of Ej have been used to ascertain the operational pH values at 25 and 37 ∘C. The pK2 values at 25 and 37 ∘C are 8.333 and 8.156, respectively. The thermodynamic quantities associated with the second acid dissociation have been calculated from the values of pK2 as a function of temperature. The zwitterionic buffer BICINE was shown to be useful as a pH standard in the region close to that of blood serum.

Predicting the performance of internally cooled/heated liquid desiccant dehumidification system is complicated, which requires a large number of iterative calculations. This article numerically developed a quick prediction method for falling film dehumidifiers and regenerators in internally cooled/heated liquid desiccant dehumidification system by non-linear regressions, to predict the mass transfer performance directly with design variables, including inlet parameters of fluids (air, desiccant, and heating/cooling fluid) and system configuration (size, air channel thickness wetting factor, and flow pattern). The LiCl and water were chosen as the solution and cooling/heating fluid. Comparison shows that differences between our results and those by existing mathematical models are acceptable, with an average absolute error of 8.0% for dehumidifiers and 5.2% for regenerators. The prediction results also appear similar with previous experiment data, showing errors of less than 10%. The solution temperature has the greatest impact on moisture effectiveness and removal rate of internally cooled/heated liquid desiccant dehumidification system. Air humidity, air flow rate, solution concentration, and solution flow rate also significantly influence the system performance. Considering the limitations of practical projects, two more simplified equations with lower but acceptable accuracy were developed. This prediction method is very useful for researches and practical applications concerning the dynamic system performance.

A general analysis and experimental validation of transmission wavefront shearing interferometry for photoelastic materials are presented. These interferometers applied to optically isotropic materials produce a single interference pattern related to one phase term, but when applied to photoelastic materials, they produce the sum of two different interference patterns with phase terms that are the sum and difference, respectively, of two stress-related phase terms. The two stress-related phase terms may be separated using phase shifting and polarization optics. These concepts are experimentally demonstrated using coherent gradient sensing in full field for a compressed polycarbonate plate with a V-shaped notch with good agreement with theoretical data. The analysis may be applied to any wavefront shearing interferometer by modifying parameters describing the wavefront shearing distance.

Experimental study and prediction model of a liquid desiccant unit for humidification during the heating season

Simulation and experiment on direct contact membrane distillation regenerator in the liquid dehumidification air-conditioning system

Electrodialysis is regarded as a novel liquid regeneration method, and the regenerated solution can satisfy the dehumidification requirements even in a hot and humid environment. LiBr solution is an important choice for a liquid desiccant air conditioning system due to its great dehumidifying ability, so it is necessary to conduct experimental exploration of the regeneration characteristics of ED regeneration for LiBr solution. In this paper, the effects of solution concentration, circulation flow rate, current and electrode solution on the performance of the electrodialysis regeneration system were studied by constructing an experimental electrodialysis regeneration system. The results show that growing the starting concentration of the LiBr solution adversely affects the regeneration characteristics of the electrodialyzer and of the air conditioning system dehumidified by the solution. Under test conditions, as the initial concentration of LiBr solution increased from 45% to 55%, the performance coefficient (COP) of the system decreased from 2.12 to 1.05. When the dehumidification requirement is met, the initial concentration of the LiBr solution should be reduced. Increasing the circulating flow rate can improve the regeneration performance of the electrodialyzer and the capability of the air conditioning system dehumidified by the solution, but excessively increasing the circulating flow rate will decrease the regeneration performance of the electrodialyzer and the performance of the air conditioning system dehumidified by the solution. Increasing the current can increase the concentration of the LiBr solution in the regeneration cells in a short time, but it will reduce the regeneration performance of the electrodialyzer and the characteristic of the air conditioning system dehumidified by the solution. The current needs to be minimized when meeting regeneration requirements. With the growth in the flow rate of the electrode solution, the regeneration performance of the electrodialyser decreases continuously.

Performance study of a heat pump driven and hollow fiber membrane-based two-stage liquid desiccant air dehumidification system

In polymer films, electrical conduction by ion transport is a significant process which is potentially capable of revealing various aspects of the film's morphology. In this report, further details and consequences of conduction experiments with ion‐doped cellulose 2.5 acetate will be discussed along with some corroborating evidence for a large number of organic liquids. The most important conclusions are: (1) sorbed moisture provides charge carriers by dissociation to H+ and OH−, and (2) the effective dielectric constant ϵ′ is increased by sorbed moisture to a value above that of the pure polymer, or organic liquid, so that barriers to the dissociation of ionic species are greatly reduced. Furthermore, the theory of weak electrolytes may be applied to “strong electrolytes” within solid polymeric and/or liquid organic systems.

This study represents the development of a mathematical model for a newly proposed Absorption-based Liquid Desiccant Regeneration (ALDR) system operating in vacuum condition. The dynamic model is developed based on the internal and external enthalpy balances and mass balances in generator and condenser in the ALDR system. The relevant governing equations are developed and the dynamic operation is then simulated to study the dynamic performance of the system. The model is able to predict the relevant parameters such as the internal and external temperature in each component, solution concentration, vacuum pressure and thermal power throughout the regeneration process. The approach used is simpler as detailed enthalpy at each state point can be avoided. The rate of evaporation and condensation in the regeneration system is also being focused here. This information will be useful for the elaboration of control system in the future.

Air-conditioning (AC) systems, which operate on traditional vapor compression refrigeration (VCR) systems, consume a substantial proportion of the world’s electricity consumed by the building industry. In the scope of decreasing greenhouse gas emissions, energy consumption, heating, ventilation, and air conditioning industries have focused on finding alternatives to electrically operated VCR systems. A combination of a liquid desiccant dehumidification system (LDDS) with a VCR system has been recommended as a superior substitute in warm and moist climates. The focus of this research article is to design and fabricate a small-scale 5 kW hybrid LDDS system by integrating the distinct technologies mentioned above. Additionally, data collected on the vapor pressure of potassium formate (KCOOH) at various solution concentrations and temperatures is being collected to assist in encouraging research and determine the optimal concentration range. In this study, experimental analysis and comparison of dehumidification performance was conducted between two desiccants by analyzing the effects of input variables ( m a , T d , and ω s ) on the output response ( Δ ω , Q d e h , and C O P h ). The results showed that the solution with a 69.92% KCOOH concentration had nearly the same vapor pressure as a solution with a 35% LiCl concentration. Moreover, it was revealed that the lowest values of m a and T d and the highest value of ω s yield maximum values of the output responses. At the same combination of input variables, the KCOOH desiccant has a much higher hybrid system coefficient of performance than the LiCl desiccant.

Liquid desiccant systems have been paid attention because of its advantages in energy saving and an environmental friendliness. The use of liquid desiccant systems offers design and performance advantages over the solid desiccant systems, especially when solar energy is used for regeneration. The objective of this paper is to analyze the simultaneous heat and mass transfer characteristics of lithium chloride aqueous solution for the plate type dehumidification system. The effects of process air and solution inlet conditions on the dehumidification performance are studied in this study. It is found that the heat transfer coefficient of the air side gives much more significant effect on the absorption rate and dehumidification effectiveness than those of the solution and the coolant sides while the mass transfer coefficient of the solution side gives more significant effect than that of the air side. It is also found that the solution concentration is the most important factor for absorption performance improvement during the dehumidification process.

Several desiccant cooling systems have been developed in terms of cost and performance. In this study a fin-tube exchanger has been used for liquid desiccant dehumidification system. This dehumidifier has been designed to study the absorption characteristic of the aqueous triethylene glycol(TEG) solution which has the flow range from 20 to 50 LPM. The dehumidifier performance characteristics of working factor variables such as inlet solution flow rate, air flow rate, solution concentration and brine temperature have been analyzed. This dehumidifier has the ability to provide running while saving the latent heat load of total energy. The result of this experiment can provide useful data for hybrid air conditioning system.

Thermodynamic modeling of ternary and quaternary (liquid + liquid) systems containing water, FeCl3, HCl and diisopropyl ether