Mass Transfer Devices Research Articles

Performance analysis of brush dampeners

Brush-dampening systems are used in offset printing presses to deposit a fine layer of water on top of a lithographic plate. The interaction between a pick-up roll and a brush is an interesting and complex mechanical problem indicative of some devices that are, or may become, useful in novel mass transfer devices. A kinematic analysis is used to identify the contributions of three independent mechanisms: (1) a splitting action at the nip formed between the roller and the brush, (2) a wiping action identical to the movement of a brush on top of a solid surface, and (3) the absence of contact between roller and brush on some sectors of the roller. Existing related theories are modified to describe mechanisms (1) and (2). The resulting theory depends on two adjustable parameters inaccessible to experimental determination but with a very well defined physical meaning. Experimental results were performed in an actual printing unit. Agreement between experiments and theory provide a sound explanation to handle what would otherwise be a hopelessly complex physical problem.

Performance of a hydro‐filter — Mass transfer coefficient and gas‐liquid interfacial area

AbstractAn experimental study of the effect of operating conditions on the performance of a hydro‐filter (marble‐bed scrubber) has been conducted. The overall volumetric mass transfer coefficient, KGa, remains constant while the gas flow rate changes in the stable operating regions but increases sharply in the region above the loading point, corresponding to a sharp increase in the total pressure drop of the hydro‐filter. Since the gas flow is turbulent and the liquid flow is laminar under the present experimental conditions, the value of KGa is strongly dependent on the flow conditions of the liquid and its properties, while those of the gas have less effect.The performance of a hydro‐filter as a mass transfer device is shown to be superior to other types of scrubbers although its main drawback is large pressure drop.

The thermodynamic design of heat and mass transfer processes and devices

This review article places in perspective the new work devoted both to the analysis of the thermodynamic irreversibility of heat and mass transfer components and systems and to the design of these devices on the basis of entropy generation minimization. The review focuses on the fundamental mechanisms responsible for the generation of entropy in heat and fluid flow and on the design tradeoff of balancing the heat transfer irreversibility against the fluid flow irreversibility. Applications are selected from the fields of heat exchanger design, thermal energy storage, and mass exchanger design. This article provides a comprehensive, up-to-date review of second-daw analyses published in the heat and mass transfer literature during the last decade.

LIQUID-LIQUID EXTRACTION IN A HOLLOW-FIBER DEVICE

Liquid-liquid extraction operations were conducted in a hollow fiber mass transfer device using two systems: phenol/water vs. n-octanol and phenol/hexane vs. water. Individual mass transfer resistances due to the tube-side fluid, the hollow fiber wall (membrane), and the shell-side fluid were determined for runs in which the solvent was held stagnant on the shell-side. Countercurrent flow runs with moving solvent were conducted to show that the degree of extraction rises steadily as the solvent-to-raffinate ratio increases. Factors affecting the mass transfer resistances in this type of device are discussed, and the advantages of hollow fiber units over conventional mixer-settler units are pointed out.

A case study of chaotic mixing in deterministic flows: The partitioned-pipe mixer

We exploit the connection between the kinematics of mixing and the theory of dynamical systems. The presentation takes the form of a case study of a novel continuous flow mixer—the partitioned-pipe mixer—to exemplify the application of theoretical concepts relating fluid mixing in deterministic chaotic systems. Two general points are stressed: firstly, the complexities that are invariably encountered during the course of analysis limit the detail to which it may be carried out, and secondly, naive analysis based on direct use of the theory may result in misleading conclusions. Starting with an approximate Stokes flow velocity field in the partitioned-pipe mixer, we study the mixing in terms of the flow patterns in the cross-section (Poincaré sections) and their relation to the conventionally used continuous mixing diagnostic, the residence time distribution, as well as to the local specific rate of stretching of material lines and the mixing efficiency. Some of the limitations of each of these methods of characterizing the mixing are exposed; however, together they provide a broad description of the mixing in the partitioned-pipe mixer, and indicate the utility of the theory. The applications of the ideas, within and outside chemical engineering, are many. The most obvious are the mixing of viscous liquids (such as molten polymers), the design of mixing devices for shear sensitive molecules and cells under non-turbulent conditions, prototype models of porous media, enhanced mass transfer devices, etc. Other applications can be expected in geophysics, environmental fluid mechanics, and condensed matter and plasma physics.

Counter-current mass transfer

A simple model for a counter-current mass transfer device is analysed asymptotically in certain parameter regimes. By using some recent results about eigenfunction expansions, explicit formulae are found for the efficiency of the device in terms of numbers of theoretical plates.

Systems analysis of effectiveness of mass transfer devices

Systems analysis of effectiveness of mass transfer devices

A Simple Evaporative System for Space-Environmental Thermal Control of Electronic Components

A passive mass transfer thermodynamic device employing the latent heat of vaporization of an enclosed liquid is described as a method of precise thermal control for single, low-mass, high-energy electronic components. This device has particular application for electronic components having high power density which are incorporated in spacecraft electronic systems relying otherwise on radiant exchange with the environment as a means of space-environmental thermal control. Specific areas of interest growing out of the design requirements for such a mass transfer device are 1) liquid ullage control under zero-g conditions, precluding loss of liquid due to blow-out, and 2) favorable exploitation of liquid adsorption and surface phenomena in maintaining a continuous heat-sinking effect. The latter effect is demonstrated by data obtained in operating appropriately instrumented thermal control test articles under one-g conditions in vacuum and non-vacuum environments. Satisfactory heat-sinking is demonstrated over a range of energy inputs. Application of the system methodology and capabilities to the problem of space-environmental thermal control is evaluated and summarized.