Absorber Research Articles

Analysis of Heat and Mass Transfer on Helical Absorber

The absorption of vapor involves simultaneous heat and mass transfer in the vapor/liquid system. In this paper, a numerical study for vapor absorption process into LIBr-HO solution film flowing over helical absorber has been carried out. Axisymmetric cylindrical coordinate system was adopted to model the helical tube and the transport equations were solved by the finite volume method. The effects of operating conditions, such as the cooling water temperature. the system pressure, the film Reynolds number and the solution inlet concentration have been investigated in view of the absorption mass flux and the total absorption mass flux and the total absorption rate. The results for the temperature and concentration profiles, as well as the local absorption mass flux at the helical absorber are presented. It is shown that solution inlet concentration affected other than operation conditions for a mass flux.

Heat Transfer Enhancement with Surfactants in Horizontal Bundle Tubes on Absorber

This research was concerned with the enhancement of heat transfer by surfactant added to the aqueous solution of LiBr. Different horizontal tubes were tested with and without an additive of normal octyl alcohol. The test tubes were a bare tube, floral tube and hydrophilic tube. The additive mass concentration was about 0.055.5%. The heat transfer coefficient was measured as a function of solution flow rate for the range of 0.010.034 kg/ms. The experimental results were compared with cases without surfactant. The enhancement of heat transfer by Marangoni convection effect generated by the addition of the surfactant is observed in each test tube. The increase of heat transfer coefficient by surfactant addition is about 3590% for bare tube, 4070% for the floral tube, 3050% for the hydrophilic tube and was higher for the cases with smaller a little solution flow rates.

Chemical Enhancement for CO2 Absorption into Dilute Aqueous Amine Solutions

Chemical enhancement factors for CO2 absorption into dilute aqueous MEN/DEA solutions in a batch stirred-cell absorber were experimentally determined over a wide range of CO2 loadings. The experimental data are used to examine the validity of two promotion mechanisms: the zwitterion mechanism, by which the carbamate formation is the sole main reaction occurring in the liquid, and the bulk-equilibrium mechanism, by which both the carbamate formation and the carbamate hydrolysis are two fast main reactions to enable the chemical equilibrium to prevail in the bulk-liquid. The results reveal that the zwitterion mechanism satisfactorily predicts the experimental data for CO2 loadings below 0.3, while the bulk-equilibrium mechanism is more competent in describing those for CO2 loadings larger than 0.5. A detailed rigorous thermcx1ynamic simulation shows that the equilibrium extent of the carbamate hydrolysis, which generates free amine in the bulk and hence promotes absorption, increases with the decrease of the initial amine concentration and with the proceeding of CO2 loadings. The experimental re-suits of absorption, therefore, indicate that the extent of the carbamate hydrolysis is insignificant in systems with low CO2 loadings however becoming significant in higher C2 loading systems. The difference between the promotion mechanisms for the absorption of CO2 by dilute aqueous NH3 solutions as previously reported by us and that by MENDEA solutions in this work is also discussed .

The Centrifugal Delayed Resonator as a Tunable Torsional Vibration Absorber for Multi-Degree-of-Freedom Systems

The centrifugal delayed resonator (CDR) is a novel active vibration absorption technique for elim inating undesired torsional oscillations in rotating mechanical structures. The key idea is to reconfigure the dynamics of a damped centrifugal pendulum arrangement so that it mimics an ideal real-time tunable ab sorber. This objective is achieved by applying a control torque based on proportional position feedback with variable gain and time delay. Theoretical fundamentals of the technique are explained, its implementation on a multi-degree-of-freedom primary structure is presented, stability of the controlled system is discussed, and real-time tuning ability is elaborated upon and demonstrated via simulations. The strengths of the CDR control consist of complete vibration elimination of the fundamental frequency component of torsional oscil lations at the location where the absorber is attached to the rotating structure, automatic tuning to time-varying frequencies, decoupling of the feedback control from the mechanical and dynamic properties of the rotating structure, relatively simple implementation of the control algorithm, and fault-tolerant performance in the case of control failure.

Effects of Non-Absorbable Gases on the Absorption Process of Aqueous LiBr Solution Film in a Vertical Tube (II)

Among the heat/mass exchange units composing an absorption system, the absorber, where the refrigerant vapor is absorbed into the liquid solution is the one least understood. In the present study, the effects of non-absorbable gas on the absorption process of aqueous lithium bromide solution falling film inside a vertical tube were experimentally investigated. In the range of film Reynolds number of 30 ~ 195, heat and mass transfer characteristics were investigated as a function of non-absorbable gas volumetric concentration, 0.2 ~ 20%. An increase of non-absorbable gas volumetric concentration degraded the mass transfer rate dramatically in the absorption process. The reduction of mass transfer rate was significant for the addition of small amount of non-absorbable gas to the pure vapor. At film Reynolds number of 130, an increase of non-absorbable gas concentration from 0.2 to 6.0% resulted in the decrease of mass transfer rate by 36% and 20% of non-absorbable gas by 59%. However the decrease of film Nusselt number with the increase of volumetric concentration of non absorbable gas was relatively smaller than the decrease of Sherwood number. Critical film Reynolds number was identified to exist for the maximum heat and mass transfer regardless of the volumetric concentration of non-absorbable gases.

Dynamic analysis and control of a robot leg with a shock absorber

Human beings usually absorb a shock from terrain during walking through the damping effects of joints, muscles and skin. With this analogy, a robot-leg with a shock absorber is built to absorb the impact forces at its foot during high-speed walking on irregular terrain. To control the hip position while walking, the dynamic controller suitable for high speed walking is designed and implemented based on a dynamic model by Kane's equation. The hip position tracking performances of various controllers (PID controller, computed torque controller and feedforward torque controller) are compared through the experiments of the real robot-leg.

An application of the electrostatic spray technology to increase scrubbing efficiency of SO$_{2}$ emitted from thermal systems

Emission control of acid exhaust gases from coal-fired power plants and waste incinerators has become an increasing concern of both industries and regulators. Among those gaseous emissions, SO has been eliminated by a Spray Drying Absorber (SDA) system, where the exhaust gas is mixed with atomized limestone-water slurry droplets and then the chemical reaction of SO with alkaline components of the liquid feed forms sulfates. Liquid atomization is necessary because it maximizes the reaction efficiency by increasing the total surface area of the alkaline components. An experimental study was performed with a laboratory scale SDA to investigate whether the scrubbing efficiency for SO reduction increased or not with the application of a DC electric field to the limestone-water slurry. For a selected experimental condition SO concentrations exited from the reactor were measured with various applied voltages and liquid flow rates. The applied voltage varied from -10 to 10 kV by 1 kV, and the volume flow rate of slurry was set to 15, 25, 35 ml/min which were within the range of emission mode. Consequently, the SO scrubbing efficiency increased with increasing the applied voltage but was independent of the polarity of the applied voltage. For the electrical and flow conditions considered a theoretical study of estimating average size and charge of the atomized droplets was carried out based on the measured current-voltage characteristics. The droplet charge to mass ratio increased and the droplet diameter decreased as the strength of the applied voltage increased.

J08109365 Heat-resistant near-inframed absorber

J08109365 Heat-resistant near-inframed absorber

Testing Unified X-Ray/Ultraviolet Absorber Models with NGC 5548

Testing Unified X-Ray/Ultraviolet Absorber Models with NGC 5548

OPTIMUM VIBRATION ABSORBER WITH ACTIVE CONTROL

In this paper, the dynamic characteristics of a vibration absorber with passive and active devices are examined by means of an optimization technique. The optimum design parameters for the following cases of absorbers are reviews: active control for the natural frequency of absorbers; active/passive control for damping ratio of absorbers and active control for the control force between absorbers and main systems. A multiple objective fuzzy optimization technique based on Bellman and Zadeh's decision criteria is used to find a design with the best compromise of dynamic response between the main system and the absorber.

Multimodal Passive Vibration Suppression with Piezoelectric Materials and Resonant Shunts

Passive piezoelectric damping devices are studied. These devices, consisting of a piezoelectric element and a resonant shunt, are analogous to mechanical damped vibration ab sorbers. In the past, a single piezoelectric device has been used to suppress a single structural mode. In this paper, the theory is expanded so that a single piezoelectric element can be used to suppress multiple modes. The multimode damper is demonstrated experimentally as a two-mode device ap plied to a cantilevered beam.

Theoretical analysis of contributions of self-phase modulation and group-velocity dispersion to femtosecond pulse generation in passive mode-locked dye lasers

The influence of self-phase modulation (SPM) and group-velocity dispersion (GVD) on pulse development in a passive mode-locked dye laser is investigated numerically by using fast Fourier transformations. The situation of positive SPM is considered. Four regions of laser performance may be distinguished: (i) In the positive GVD region pulse broadening by GVD must be balanced by the pulse-shortening effect of the saturable absorber. (ii) In a region around zero GVD the laser is periodically self-quenching and the temporal and spectral pulse shapes change periodically similar to higher-order solitons. (iii) It follows a negative GVD region where stable pulses of smooth temporal and spectral shapes are generated similar to fundamental solitons. In this region the pulse duration is practically independent of the saturable absorber concentration, and the saturable absorber is needed mainly for background suppression. (iv) Further increasing the negative GVD, pulse broadening must be balanced by the saturable absor ber pulse shortening.

FORMATION AND STRUCTURE OF ADDUCT OF PHYCOCYANOBILIN DIMETHYLESTER WITH WATER

Phycobiliproteins, part of the photosynthetic apparatus in algae, are a group of important absorbers of light, in which the functional groups for light absorption are linear tetrapyrrole chromophores. In order to interpret the photobiological phenomenon of the phycobiliproteins, it is important to investigate the chemical properties and the formation of the derivatives of the chromophores.

REBREATHING DUE TO INCOMPETENT UNIDIRECTIONAL VALVES IN THE CIRCLE ABSORBER SYSTEM

REBREATHING DUE TO INCOMPETENT UNIDIRECTIONAL VALVES IN THE CIRCLE ABSORBER SYSTEM

Theoretical analysis of pulse development in a colliding pulse mode-locked dye laser

The pulse development in colliding pulse mode-locked dye lasers is analysed theoretically. The chosen parameters belong to a c.w. argon laser pumped linear resonator arrangement with rhodamine 6G in ethylene glycol as gain medium and DODCI (3,3′-diethyloxadicarbocyanine iodide) in ethylene glycol as saturable absorber. The pulse shortening and pulse broadening effects in the laser oscillator are investigated. The steady-state pulse duration is determined by equal pulse broadening and pulse shortening within a single resonator round-trip. The detuning of the absorber jet out of the middle position of the resonator is considered. Multiple transits through the resonator are simulated to study the influence of various resonator and dye parameters on the pulse development and the background signal suppression. Fast relaxations within theS 1 andS 0-state of DODCI are necessary for sufficient background suppression to obtain femtosecond pulse trains.

Evaluating UV Absorbers and Antioxidants for Topical Treatment of Upholstery Fabrics

UV absorbers and antioxidants topically applied to upholstery fabrics to reduce fading, separately and in conjunction with soil repellent finish formulations containing UV absorbers, were evaluated in this study. Over fifty upholstery fabrics were initially evaluated and fourteen were selected for further study. The fabrics were then topically treated with commercially available soil repellent finishes (a fluorocarbon and a silicone finish) containing UV absorbers or immersion-treated with one of thirteen UV ab sorbers or antioxidants. Following light exposure, color changes were evaluated visually and instrumentally. The results showed that neither the fluorocarbon nor silicone- based soil repellent finishes containing UV absorbers significantly reduced fading in the upholstery fabrics. Furthermore none of the UV absorbers and antioxidants applied to the upholstery fabrics improved lightfastness properties substantially, so they cannot be recommended as additives to soil repellent finish formulations.

Rotating body sympathetic vibration absorber

First Page

Ideal concentrators with polygonal absorbers

Discussion des proprietes et des avantages d'une famille de concentrateurs ideaux a absorbeurs polygonaux

Unloading additional absorbers from the RBMK-1000 core

Unloading additional absorbers from the RBMK-1000 core

Mechanical shock absorber

A shock absorber for attenuating a shock effect between a fixed point and a movable element which comprises a casing, a threaded element mounted for axial movement within the casing, and a first engagement member and a second engagement member mounted for rotary and axial movement within the casing in response to a shock effect, the first engagement member being in normal contact engagement with the threads of the threaded element for converting the axial movement of the threaded member into a rotary movement of the second engagement member and the second engagement member being adapted to engage the threads of the threaded element, whereby upon the application of the shocking effect above a predetermined amount, the second engagement member abuts against the threads of the threaded element to block further rotational movement of the second engagement member by becoming lockingly engaged with the threads of the threaded element while the shocking force is applied thereto.