Absorption Coefficient Of Liquids Research Articles

A solar-heated antibacterial sodium alginate aerogel for highly efficient cleanup of viscous oil spills

Hypothesis. Major oil spills highlight the need for environmentally responsible and cost-effective recovery technologies. However, challenges remain for heavy oil spill recovery because of its high viscosity and low fluidity. To achieve this goal, an ecofriendly bio-based aerogel with efficient photothermal conversion ability was developed as a novel absorbent to achieve the fast removal of heavy oil spill by reducing the oil viscosity.Experiments. From the renewable and abundant raw material sodium alginate (SA), hydrophobic and antibacterial SA/graphene oxide/ZIF-8 aerogel (SAGZM) was successfully fabricated via freezing-drying and chemical vapor deposition (CVD) technique. A series of characterization and tests, including aerogel structure, selective wettability, photothermal conversion ability, crude oil removal capability, and antibacterial ability, have been investigated in detail. SAGZM aerogels have rich pore structure, high porosity, excellent mechanical properties, and better photothermal conversion efficiency.Findings. Under sunlight illumination, the recovery ability of SAGZM for heavy crude oil was investigated through infrared thermal imaging, oil permeability behavior analysis, and the continuous absorption for crude oil. In addition, these results are well supported by the theoretical liquid absorption coefficient. This study indicates that SAGZM is highly efficient in in situ regulating oil viscosity through its remarkably photothermal conversion capability. Importantly, SAGZM possesses an excellent antibacterial ability that is often neglected in the design of environmentally friendly materials in extending its service life. The findings of this work not only provide an eco-friendly bio-based aerogel material but also demonstrate that the photo-responsive SAGZM is efficient in heavy crude oil absorption. The proposed solar-heated SA-based aerogel provides a sustainable approach and material to solve the recovery problem of viscous crude oil spills.

Calculation of radiation transmittance through n-heptane in a pool fire

The radiative transfer mechanisms in a volatile hydrocarbon pool fire were investigated by solving the transmittance of infrared radiation through fuel (n-heptane) layers of different depths. The incoming radiation was assumed to have the same relative amounts of different wavelengths as a spectrum obtained experimentally for a 2 meter pool fire, and the transmittances were calculated by integrating either the single-ray Lambert-Beer formula, the two-flux (Schuster-Schwarzschild) method solution or the analytical plane-parallel monochromatic/gray solution of the radiative transfer equation over wavelength, using the liquid absorption coefficients from several sources. The obtained transmittances were compared to earlier heat flux measurements, and the possibility of calculating them with significantly less computation time by using a k-distribution method was investigated. The results managed to replicate the measured heat flux values at depths over 1 mm in the liquid with reasonable accuracy, and the use of the k-distribution, more known and used in gas phase thermal radiation calculations, significantly speeds up the calculations.

Optical properties of high temperature molten salt mixtures for volumetrically absorbing solar thermal receiver applications

Molten salts are promising candidates for liquid volumetric absorbers in concentrated solar power systems. To characterize absorption and heat transfer performance in high temperature applications, their optical properties are required. Thus a method for experimentally determining the absorption coefficient of non-scattering high temperature semi-transparent liquids for large (∼1m-deep) direct absorption solar receiver applications was developed. It was used to measure the absorption coefficient in liquids over a broad spectral range and temperatures up to 800°C in a 40wt.% KNO3:60wt.% NaNO3 binary nitrate molten salt mixture (solar salt) and a 50wt.% KCl:50wt.% NaCl binary chloride molten salt mixture. The binary nitrate and binary chloride both demonstrated well distributed solar absorption (>95% absorption through 1m and 2m, respectively). At 400°C, the binary nitrate is optically thick in its re-emission spectrum and behaves as a blackbody radiator. The effects of thermal decomposition were also shown to have significant consequences on the overall performance of the binary nitrate mixture, transforming it into an opaque surface absorber following thermal degradation (>95% in <0.25m). The implications of these results for solar receiver design are discussed in terms of volumetric absorption, total effective emissivity, and capture efficiency. The measurement technique developed and results are relevant in a variety of high temperature applications including heat transfer systems, materials processing, pharmaceuticals, and food processing facilities.

Nonscanning Moiré deflectometry for measurement of nonlinear refractive index and absorption coefficient of liquids.

In this work, a nonscanning measurement technique is presented for determining the nonlinear refractive index and absorption coefficient of liquid media based on Moiré deflectometry. In the proposed method two lasers are used: a low power, wide beam as probe and a high power with specific wavelength as a pump. Interaction of the pump laser beam with the nonlinear sample changes the refractive index, which leads to change in convergence/divergence of the collimated incident probe laser beam. The induced deflection is monitored by Moiré deflectometry. If the pump laser has a Gaussian intensity profile, the refractive index profile of the sample is Gaussian, too. Measuring the deflection angle of the probe beam by Moiré fringes deflection, and by using the inverse Abel transform integral, the refractive index profile and nonlinear refractive index can be determined. This method is fast, easy, and insensitive to environmental noise and allows real-time measurement. Also, the refractive index profile of the interacted medium with pump laser can be achieved by this technique. As a liquid sample, a DCJ dye in water solution was studied. The value of nonlinear refractive index, n2, and absorption coefficient, α, were obtained -2.54×10-4 cm2 w-1 and 1.368 cm-1, respectively.

Applications using high-Tc superconducting terahertz emitters.

Using recently-developed THz emitters constructed from single crystals of the high-Tc superconductor Bi2Sr2CaCu2O8+δ, we performed three prototype tests of the devices to demonstrate their unique characteristic properties for various practical applications. The first is a compact and simple transmission type of THz imaging system using a Stirling cryocooler. The second is a high-resolution Michelson interferometer used as a phase-sensitive reflection-type imaging system. The third is a system with precise temperature control to measure the liquid absorption coefficient. The detailed characteristics of these systems are discussed.

Quantitative calculation of reaction performance in sonochemical reactor by bubble dynamics* *Project supported by the National Natural Science Foundation of China (Grant Nos. 11404245, 11204129, and 11211140039).

In order to design a sonochemical reactor with high reaction efficiency, it is important to clarify the size and intensity of the sonochemical reaction field. In this study, the reaction field in a sonochemical reactor is estimated from the distribution of pressure above the threshold for cavitation. The quantitation of hydroxide radical in a sonochemical reactor is obtained from the calculation of bubble dynamics and reaction equations. The distribution of the reaction field of the numerical simulation is consistent with that of the sonochemical luminescence. The sound absorption coefficient of liquid in the sonochemical reactor is much larger than that attributed to classical contributions which are heat conduction and shear viscosity. Under the dual irradiation, the reaction field becomes extensive and intensive because the acoustic pressure amplitude is intensified by the interference of two ultrasonic waves.

Model Development and Performance Studies of a Concentrating Direct Absorption Solar Collector

A detailed three-dimensional (3D) computational fluid dynamics (CFD) model of a direct absorption solar collector (DAC) is presented. Radiative transfer equation (RTE) is coupled with Navier–Stokes equations and solved numerically to predict the collector efficiency. The spectral properties of absorbing liquids are captured using a band-averaged absorption model. This numerical model is validated with experimental data for two different types of absorbing fluids viz., gray (graphite particles in water) and nongray (copper sulfate) fluids. The validated model is used for parametric studies to determine the right design choices for an improved collector. Impact of optical concentration ratio (CR), optical density of the fluid, mass flowrate, and thermal insulation on the collector efficiency were studied. Increase in collector efficiency of up to 28% is seen due to higher optical CRs, which is attributable to good absorption characteristics of the receiver and reduced area for losses. The collector efficiency does not improve with absorption coefficient of the fluid beyond a certain value for a given thickness of the fluid layer. The range of mass flow rates considered in the study was found to have no impact on collector efficiency. Thermal insulation is found to be very effective in minimizing the overall thermal losses and enhancing the collector efficiency. The numerical model presented here may be used to identify optimum CR, absorption coefficient of liquid for a direct absorption concentrating collector.

Influence of liquid absorption coefficient on hygrothermal behaviour of an existing brick wall with Lime–Hemp plaster

The study of the hygrothermal parameters and performance of permeable materials is being expanded; however, there is a lack of guidelines or regulation regarding the level of liquid water migrations associated with existing materials. Even if some existing recommendations demand the installation of materials that are increasingly permeable to vapour, the liquid water absorption coefficient is often neglected. This study analyses the influence of six material parameters, such as the liquid absorption coefficient and vapour diffusion resistance, on the hygrothermal behaviour of an existing brick wall insulated on the inside surface with a Lime–Hemp plaster. A specific methodology is developed combining hygrothermal simulations, sensitivity analysis and an experimental planning method. This reproducible methodology allows recommendations to be proposed to help designers choose an appropriate combination of material parameters. The paper demonstrates that the water liquid absorption coefficients of brick and of insulation have a greater influence than the vapour diffusion resistance of those materials in the studied cases. Water liquid absorption coefficient should thus be one of the parameters systematically considered in the hygrothermal analyses of wall components.

Bi-directional reflectance study on particulate layers: Effects of pore liquid absorption coefficient

We have made bi-directional reflectance distribution function (BRDF) measurements on particulate layers wetted by absorbing liquids. The measurement results indicate that the BRDF tends to become more Lambertian as the interstitial pore liquid becomes more absorbing. The directional hemispherical reflectance, or albedo, of such a layer decreases nonlinearly with a wetting liquid's absorption coefficient. This behavior may be fit by two empirical relationships which independently treat the reflectance from the front surface and reflectance from the bulk material.

Analysis of integrated cloud liquid and precipitable water vapor retrievals from microwave radiometers during the Surface Heat Budget of the Arctic Ocean project

We investigated a variety of factors that influence the determination of precipitable water vapor (V) and integrated cloud liquid (L) by dual‐channel microwave radiometers (MWRs). These factors include radiometric calibration; dry, water vapor, and liquid absorption coefficients; and physical versus statistical retrieval methods. We then applied the analysis to the MWR that was operated by the Atmospheric Radiation Measurement Program (ARM) during the Surface Heat Budget of the Arctic Ocean project. In the work reported here, MWR data taken from April 1 to July 31, 1998, were analyzed. Data acquired in situ did not always agree with the original MWR liquid retrievals, with MWR estimates at times being too large by perhaps a factor of 2. These differences led us to examine in detail several of the assumptions that go into V and L retrievals. The radiometer was carefully examined and found to be well calibrated with a 0.3 K RMS error. The predicted accuracy in the L retrievals, for this 0.3 K RMS radiometric error and a statistical retrieval, was 25 g m−2 RMS. This accuracy improves to 10%, if we use the improved knowledge of cloud temperature, as can be obtained using radiosondes and cloud radar/lidar measurements. We also studied the degree to which different clear air and cloud liquid models have an effect on V and L retrievals. The most significant changes from the original ARM retrievals were due to the dry opacity and the cloud liquid dielectric model. Although nothing was found in the original ARM data that was grossly incorrect, application of these models reduced the original ARM retrievals by roughly 20 to 30%. The change of clear‐air absorption model from the original to a more recent one has little impact on V retrievals except when V is &lt;0.5 cm.

Pulsed photoacoustic measurements of large optical absorption coefficients

A method to determine large optical absorption coefficients of liquids from the amplitude ratio of acoustic waves generated under rigid- and free-boundary conditions is presented. This has been examined both experimentally and theoretically, taking into account the attenuation of the pulse amplitude ratio with the increased acoustic path length due to attenuation effects. Although the proposed method was tested in a narrow wavelength interval and close to the limit of precision of the experimental arrangement, the results show quantitative agreement with the literature values.

A computer-controlled submillimeter Fourier spectrometer

A system for submillimeter-wave Fourier transform spectroscopy (FTS) has been automated for the measurement of the power absorption coefficient of liquids in the wavenumber range 10-400 cm/sup -1/. The interferometer is interfaced with a RM380Z Research Machines microcomputer. Software and hardware have been developed to automate the process of collecting and storing the data. Some points of relevance to the analysis of interferometric data are reviewed including the use of phase modulation, the resolution of spectra computed using the discrete Fourier transform, and the necessity of proper optical filtering in spectrometers which use Fourier transform techniques. Spectra measured using the FTS system described have been compared with results obtained using a tunable submillimeter laser and a good agreement was found between the two sets of data. >

High-Q plano-concave resonator with and without Straubel quartz for ultrasonic absorption measurements of liquids

A resonator technique for the measurement of the sound absorption coefficient of liquids is described. It is designed for use at low frequencies with reasonably small sample values. The construction of a high-precision cylindrically shaped specimens cell is shown and results for different versions of the resonator are presented. The relative merits of using a Straubel quartz instead of a disc-shaped quartz as the transmitter crystal and of using a concave instead of a plane reflector as the opposite face of the cavity are discussed. The accuracy of the method is illustrated by results of measurements which have been performed at frequencies down to 80 kHz on a low-loss 0.1-M aqueous solution of magnesium sulfate. >

Acoustical absorption spectroscopy of liquids between 0.15 and 3000 MHz: II. Ultrasonic pulse transmission methods

Two methods are described which allow precise measurements of the ultrasonic absorption coefficient of liquids between about 5 and 400 MHz and 1 and 50 MHz, respectively. In both cases RF substitution techniques are applied to determine the attenuation of pulsed signals transmitted through the sample cell. In the former method a cell with variable spacing of the piezoelectric transmitter and receiver crystal is used and the measurements are automatically driven by a process control computer. The latter method is based on a cell of fixed pathlength, using a simple electronic set-up and a manual mode of operation. The construction of the cells is given in detail and the relative merits and limitations of the two methods are briefly discussed. Examples of acoustic absorption spectra are presented to demonstrate the accuracy of measurements.

Acoustical absorption spectroscopy of liquids between 0.15 and 3000 MHz. I. High resolution ultrasonic resonator method

A technique is described to determine the sound absorption coefficient of liquids by means of a sensitive resonator method. Details of the construction of high-precision sample cells are shown and the electronic circuit for computer-controlled measurements is presented. Also discussed are various possible sources of experimental errors and appropriate data recording and evaluation procedures. Results are given to illustrate the accuracy of this measurement technique.

Comparison of models for the absorption coefficient of liquids

Bandshape expressions for the condensed phase absorption coefficient and dielectric constant which incorporate the Lorentz and Onsager-Bottcher local field models are presented and compared with experiment for four liquid-phase infrared bands. The principal difference between the two models is the predicted value for the integrated absorptivity. While this quantity varies by up to 10% between the two models, differences of the same magnitude occur within each model when fit to both the real and imaginary components of the dielectric constant.

A broad-band single pulse technique for ultrasound absorption studies of aqueous solutions in the frequency range 200 kHz–1 MHz

A single pulse time-domain technique is described for determining, via Fourier transform methods, the compressional wave ultrasound absorption coefficient in liquids contained in spherical reverberators over a frequency range from ≈ 200 kHz to 1 MHz. Only modest data storage and computational facilities are required. Such a technique offers an advantage over variable continuous frequency methods in that data for a given frequency range can be acquired ‘instantaneously’ and thus it is possible to monitor ultrasound absorption in time-varying systems. The method is illustrated by provision of absorption data in the frequency range 200 kHz–1 MHz for out-gassed water, aqueous solutions of the electrolyte cobaltous sulphate, with and without gas bubbles, and for the protein bovine serum albumin under conditions of acid pH obtained using spherical reverberators of 100 and 250 ml capacity.

Measurements of refractive indices and power absorption coefficients of liquids at 2.54 THz (118 μm)

Measurements of refractive indices and power absorption coefficients of some liquids at 2.54 THz are made and compared with the measurements obtained by FTS. The accuracy of measurements of refractive indices is about 0.02 and 0.5% for full- and partial-fringe techniques, respectively. The precision of measurement of the power absorption coefficients is better than 3%.

Optimum laser cavity and internal cell place for thermal lens effect measurements by the photomixing method

The photomixing method for the measurement of small absorption coefficients of liquids placed in a Brewster-angle cell inside a He-Ne laser cavity is optimized, and criteria are given for the location of the cell inside the cavity, as well as for the cavity selection. These criteria allow for a maximum sensitivity and accuracy of the method. This improved technique has been used to determine the absorption coefficients of some organic liquids.

Determination of Ultrasonic Absorption Coefficients of Liquids by Thermoelectric Probes

The determination of ultrasonic absorption coefficients of high-absorption liquids by thermoelectric probes is accomplished by exciting the sound source (in contact with the liquid) electrically to emit acoustic pulses of accurately reproducible envelopes and time durations. The temperature in the immediate neighborhood of the thermocouple junction is transiently increased, principally because of the action of the viscous forces acting between the thermocouple wires and the liquid. The peak amplitude of this transient thermoelectric emf is proportional to the acoustic intensity in the plane wave field in the immediate neighborhood of the junction. The space gradient of the acoustic intensity is obtained, and the value of the absorption coefficient is readily computed from this data. Results obtained with several oils in the 100 Mc/sec frequency region will be presented. (This work was supported by the Office of Naval Research.)