Phase Changer Research Articles

Functional and financial analysis of an inclined step solar desalination using phase change nanomaterials.

Recent decades have seen a shortage of water, which has led scientists to concentrate on solar desalination technologies. The present study examines the solar water desalination system with inclined steps, while considering various phase change materials (PCMs). The findings suggest that the incorporation of PCM generally enhances the productivity of the solar desalination system. Additionally, the combination of nanoparticles has been used to PCM, which is a popular technique utilized nowadays to improve the efficiency of these systems. The current investigation involves the transient modeling of a solar water desalination system, utilizing energy conservation equations. The equations were solved using the Runge-Kutta technique of the ODE23s order. The temperatures of the salt water, the absorbent plate of the glass cover, and the PCM were calculated at each time. Without a phase changer, the rate at which fresh water is produced is around 5.15 kg/m2·h. The corresponding mass flow rates of paraffin, n-PCM I, n-PCM III, n-PCM II, and stearic acid are 22.9, 28.9, 5.9, 11.9, and 73 kg/m2·h. PCMs, with the exception of stearic acid, exhibit similar energy efficiency up to an ambient temperature of around 29°. However, at temperatures over 29°, n-PCM II outperforms other PCM.

Antimony Nanofilms as Optical Phase Changers

Antimony Nanofilms as Optical Phase Changers

Dynamic modelling of Adsorption systems: a comprehensive calibrateddataset for heat pump and storage applications

The growing efforts for the development of clean and efficient energy systems require the use of a multi-disciplinary approach and the integration of multiple generation appliances. Among the fields that can be considered enabling technologies, adsorption systems for air conditioning and thermal energy storages, are constantly increasing their maturity. However, for a proper design and integration of such systems, there is the need for a simulation framework that is reliable and computationally convenient. In the present paper, the implementation of a dynamic model for adsorption systems is presented, which includes different components (adsorber, phase changer, sorption materials) and is structured as a library. Modelica language and the commercial software Dymola® are used for the analysis. Data for different heat exchangers and working pairs are calibrated using experimental results and the calibrated model is subsequently used for the design of an adsorber based on a plate heat exchanger for thermal energy storage applications. The results proved that the model is fast and can reproduce experimental results with good accuracy, thus being a useful tool for the design and optimization of the different components of sorption systems.

Role of condensation on boiling heat transfer in a confined chamber

A theoretical model of the coupled boiling and condensation phase changer heat transfer in a confined chamber is developed and numerically analyzed based on the modified hybrid lattice Boltzmann method. The interaction of boiling and condensation behavior is investigated with particular attention focused on the influence of condensation surface wettability on the boiling heat transfer process. Besides, the temperature response and the detailed two-phase flow pattern inside the chamber with different condensation surface wettability are evaluated. The results indicated that an optimal contact angle of 85° for the condensation surface wettability promoted the heat transfer on the evaporation surface. Subsequently, two modified condensation surfaces (biphilic surface with alternative hydrophilic and hydrophobic regions and gradient surface with a gradual wettability transition from hydrophilic to hydrophobic) are proposed for further heat transfer enhancement of the confined chamber. The results of the boiling curves, the two-phase flow pattern and the local/averaged heat transfer coefficient on the evaporation surface indicated that, compared with the single wettability with the optimal contact angle, both modified condensation surfaces can achieve a higher critical heat flux and a higher boiling heat transfer coefficient. Among these, the biphilic surface can achieve relatively better heat transfer performance.

Development and Performance Evaluation of an Indirect Heat Copra Dryer with Phase Changer

In the Philippines, farming communities produce copra using traditional open sun drying method that could be severely affected by heavy rainfall, temperature change, and intermittent sunshine, which could cause high microbial infection to the product. On the other hand, kiln drying may avoid these circumstances. However, smoke deposits in the finished product still cause farmers to have low-quality grade copra. Keeping this in view, an indirect heat copra dryer with phase changer (IHCDPC) was designed, fabricated, and evaluated in the hopes of providing farmers an alternative approach in drying copra, which may yield to producing a high-quality grade product. The developed IHCDPC was able to reduce the moisture content in fresh coconut meat from 57.4% w.b. to about 7.2% w.b. for a drying time of twenty-five hours. The IHCDPC was found out to have a thermal efficiency of 30.87%. The copra produced were graded as 84% MGC1, 13% MGC2, and 3% MGC3.

IOT Survey: The Phase Changer in Healthcare Industry

IOT Survey: The Phase Changer in Healthcare Industry

ПринциП И устрОйствО формированиЯ сигналоВ С определенныМ фазовыМ сдвигоМ В диапазонЕ часТоТ

One of possible approaches in the problem solving of a high-performance broadband phase changers creation is considered. Offered principle and device allow to extend working frequency range or improve precision of phase shift in a former range.

Lossless transmission and the measurement off insertion loss

A method of finding the true insertion loss of a dissipationless device interposed between a mismatched source and load is described. The VSWRs of the source, device, and load are found from the extremes, or in practice from the ratios of the extremes in transmission brought about by varying the electrical length of the interconnecting lines. The theory is verified by results obtained using a waveguide system with phase changers. A possible application would be in millimetre wave beam transmission where, in principal, only the source and detector need be moved to carry out the measurement.

Experimental Study Of Mirror Segment Phasing Using Tungsten Light

This paper describes the absolute phasing of two adjacent mirror panels using a 10 W tungsten lamp, a slit, a linear charge-coupled device array, and an oscilloscope. Repeatability of measurement settings equivalent to five one-thousandths of a wavelength was demonstrated using only visual observation of the oscilloscope and a calibrated phase changer. The indicator of phase used in these tests is the intensity distribution across the image, similar in this respect to the Phasar method developed by the Air Force Weapons Laboratory. The phasing of circular apertures as well as small subapertures is shown. A simple near-linear phase changer, to change phase manually by less than one thousandth of a wave, was developed to determine precision and accuracy of the phasing method.

Computer-aided design of high-frequency electromagnetic devices using the finite-element method

The finite-element method has been used in the electromagnetic analysis of a wide range of devices from microwave to optical frequencies. Established early on as a means of finding waveguide modes, it has more recently been applied in the determination of equivalent circuit parameters for arbitrarily shaped N-port devices such as phase changers, directional couplers and circulators. What is needed now is an integration of the various finite-element methods into a software package for high-frequency electromagnetic design.

A broadband experimental null-steering antenna system for mobile communications

The paper describes a novel and particularly simple form of null-steering antenna suitable for the base station of a mobile communication system which is subject to high levels of directional interference. The antenna provides omnidirectional coverage in the horizontal plane and has the facility of introducing a directional null which may be electronically steered through 360° of azimuth. This can therefore be used to minimize an interfering signal without affecting communication in other directions. The antenna employs a 4 or 5 element circular array and a simple null steering network requiring only one phase changer to steer the null. Various configurations of this antenna are examined theoretically and supported by experimental measurements on a system operated at 153 MHz. Experimental values of null depth lie in the range of 25–50 dB when operating over a bandwidth of ±30% of the centre frequency. Null widths (measured at the − 10 dB points) may be electronically varied within the range 28°–68°. Applications for such a null-steering antenna and methods to increase the operating bandwidth are also discussed.

On the use of delays for wide-band superdirective beam forming in endfire and broadside arrays

In algebra, the values of a polynomial over a wide span of time can be inferred from its value and that of its derivatives, measured over a very short span of time. Somewhat analogously, closely-spaced measurements, defining the fine structure of the phase and amplitude distribution over a narrow antenna aperture, can provide the information conventionally obtained from a similar number of elements spaced at half-wavelength intervals over a wider aperture.Superdirective beam patterns, exploiting this principle, are conveniently synthesized by defining the directions in which zero (or minimum) response is required. The correlation between closely-spaced measurements will then cause some reduction of gain, even at the wanted peak of the directional response pattern, but the directivity, i.e. the gain in the wanted direction relative to that in other directions, can be significantly enhanced.Each direction of arrival produces a corresponding pattern of relative propagation delays to the different elements of an array. By suitably equalizing these with non-dispersive delay circuits and then subtracting for null-forming (in place of the usual phase changers), such superdirective arrays can be designed for bandwidths of up to several octaves. Thus superdirectivity can be of considerable value, in certain circumstances, for h.f. radio, sonar or radar.

Frictional force coefficient of a moving dislocation in uranium dioxide with excess oxygen

The frictional force coefficient B of moving dislocations in uranium dioxide with excess oxygen in the UO 2 to U 4O 9 range was measured at temperatures from −40 to +200°C by means of ultrasonic attenuation. The B values increase in the two temperature regions of relaxational internal friction peaks. These increases of B values are interpreted in terms of the redistribution of atoms, which brings forth the phase changer and the Snoek ordering of excess interstitial oxygen atoms, respectively, in the stress field of the moving dislocations.

The measurement of permittivity of high-loss liquids at microwave frequencies using an unmatched phase changer

The behaviour of an adjustable length of coaxial line containing a standing wave is considered theoretically. It is shown that a relationship can be obtained between the change in the line length and the resulting change of phase. This is then followed by a description of how the complex permittivity of a liquid such as water can be measured using the phase changer in conjunction with a phase-amplitude balance method.

A Practical Design of a Simple Retardance Meter

A working design of a simple retardance meter is indicated. The device permits direct, quick, and accurate measurement of the retardance, for example, of an oriented polymeric film which is intended for use as a phase changer plate in the production of elliptically polarized light. The method involves the direct compensation of the sample's retardance using the calibrated retardance of a mica crystal which is variably tilted about one of its two principal planar axes. Several suggestions relating to the optical design, assembly, and calibration of the device are included.

High-voltage thyristor strings for inverter applications

The application of thyristors to inverters is, in general, difficult. Rapid change of voltage and current requires high component tolerance. Thyristor turn-off time is most important. High forward current and reverse voltage provide considerable component stress. Static inverters are enjoying great popularity as frequency changers, motor speed controls, standby systems, phase changers, voltage transformers, and in direct voltage transmission systems. A noticeable trend in these applications is the increasing power capability of the inverter. The use of higher operating potentials provides a means of handling higher power without using components having extremely large effective areas. Some applications, notably direct power transmission, are feasible only at operating potentials in the kilovolt range. Above about 400 volts, series strings are necessary. Combining a difficult application and cascaded components results in a design problem for both the component and the system designer. In addition to the normal inverter application troubles is the necessity for dynamic voltage balance. Such mundane problems as gate drive isolation and insulation prove to be formidable. The application of series thyristor strings in an oil-cooled inverter operating at 4000 direct volts is described. System design solutions to component limitations are also discussed.

Series-fed circular array

This letter describes how a circular array may be phased to produce a main beam in one direction by feeding the elements from a set of series-connected phase shifts. The direction of the main beam may consequently be varied by control of the values of phase shift. The significant feature of the series-feeding technique is the small phase deviation required per phase changer for 360° beam steering.

A new colinear antenna array

This paper describes the application of a phase changer which, when periodically distributed along a cylindrical conductor, controls the phase of the currents so that the radiation is concentrated in a plane perpendicular to the axis of the conductor. A theoretical analysis is made of a two-element structure, and the results are compared with those obtained by experiment. Further experimental results are given for multi-element structures.

Analysis of the variable-ratio microwave power divider (Correspondence)

It has been shown experimentally that a variable-ratio microwave power divider is easily assembled from two identical 3-db directional couplers and a phase changer. The scattering matrix of this structure is readily obtained from the flow graph showing the interconnections between the couplers. The following shows that the whole structure is still a directional coupler, derives the conditions to optimize the power transfer, and finally, gives the phase angles of the scattering coefficients.

Errors in a Magic-Tee Phase Changer

This paper recalls the basic properties of a magic-tee and how it can be used as a linear phase changer. An analysis of the symmetrical magic-tee phase changer is made, which shows that nonlinearities of the phase shift and amplitude modulation are second and higher order effects caused by small mismatches of the structure. Also, some qualitative comments are made on the errors of an asymmetrical phase changer. Measurements on a phase changer assembled from ordinary laboratory equipment show that the phase shift is linear to better than 1°.