Determination of design space and optimization of solar water heating systems

In this paper, a methodology is proposed to determine the design space for synthesis, analysis, and optimization of solar water heating systems. The proposed methodology incorporates different design constraints to identify all possible designs or a design space on a collector area vs. storage volume diagram. The design space is represented by tracing constant solar fraction lines on a collector area vs. storage volume diagram. It has been observed that there exists a minimum as well as a maximum storage volume for a given solar fraction and collector area. Similarly existence of a minimum and a maximum collector area is also observed for a fixed solar fraction and storage volume. For multi-objective optimization, a Pareto optimal region is also identified. Based on the identified design space, the solar water heating system is optimized by minimizing annual life cycle cost. Due to uncertainty in solar insolation, system parameters and cost data, global optimization may not be utilized to represent a meaningful design. To overcome this, a region of possible design configurations is also identified in this paper.     

Targeting for cogeneration potential through total site integration

Total site integration offers energy conservation opportunities across different individual processes and also to design as well as to optimize the central utility system. In total site integration of the overall process, indirect integration with intermediate fluids or through a central utility system are preferred as it offers greater advantages of flexibility and process control but with reduced energy conservation opportunities. To achieve the maximum possible indirect integration between processes assisted heat transfer, i.e., heat transfer outside the region between process pinch points, plays a significant role. A new concept is proposed in this paper for total site integration by generating a site level grand composite curve (SGCC). Proposed SGCC targets the maximum possible indirect integration as it incorporates assisted heat transfer. In this paper, a methodology is proposed to estimate the cogeneration potential at the total site level, utilizing the concept of multiple utility targeting on the SGCC. The proposed methodology to estimate the cogeneration potential is simple and linear as well as utilizes the rigorous energy balance at each steam header.     

Design of solar thermal systems utilizing pressurized hot water storage for industrial applications

A large number of industrial processes demand thermal energy in the temperature range of 80–240 °C. In this temperature range, solar thermal systems have a great scope of application. However, the challenge lies in the integration of a periodic, dilute and variable solar input into a wide variety of industrial processes. Issues in the integration are selection of collectors, working fluid and sizing of components. Application specific configurations are required to be adopted and designed. Analysis presented in this paper lays an emphasis on the component sizing. The same is done by developing a design procedure for a specific configuration. The specific configuration consists of concentrating collectors, pressurized hot water storage and a load heat exchanger. The design procedure follows a methodology called design space approach. In the design space approach a mathematical model is built for generation of the design space. In the generation of the design space, design variables of concern are collector area, storage volume, solar fraction, storage mass flow rate and heat exchanger size. Design space comprises of constant solar fraction curves traced on a collector area versus storage volume diagram. Results of the design variables study demonstrate that a higher maximum storage mass flow rates and a larger heat exchanger size are desired while limiting storage temperature should be as low as possible. An economic optimization is carried out to design the overall system. In economic optimization, total annualized cost of the overall system has been minimized. The proposed methodology is demonstrated through an illustrative example. It has been shown that 23% reduction in the total system cost may be achieved as compared to the existing design. The proposed design tool offers flexibility to the designer in choosing a system configuration on the basis of desired performance and economy.     

A compact dual‐band zeroth‐order resonator antenna loaded with meander line inductor

A novel zeroth‐order resonator (ZOR) meta‐material (MTM) antenna with dual‐band is suggested using compound right/left handed transmission line as MTM. In this article, suggested antenna consists of patch through series gap, two meander line inductors, and two circular stubs. The MTM antenna is compact in size which shows dual‐band properties with first band centered at 2.47 GHz (2.05‐2.89 GHz) and second band is centered at 5.9 GHz (3.70‐8.10 GHz) with impedance bandwidth of (S₁₁ < ? 10 dB) 34.69% and 72.45%, respectively. At ZOR mode (2.35 GHz), the suggested antenna has overall dimension of 0.197λ_o × 0.07λ_o × 0.011λ_o with gain of 1.65 dB for ZOR band and 3.35 dB for first positive order resonator band which covers the applications like Bluetooth (2.4 GHZ), TV/Radio/Data (3.700‐6.425 GHz), WLAN (5‐5.16 GHz), C band frequencies (5.15‐5.35, 5.47‐5.725, or 5.725‐5.875 GHz) and satellite communication (7.25‐7.9 GHz). The radiation patterns of suggested structure are steady during the operating band for which sample antenna has been fabricated and confirmed experimentally. It exhibits novel omnidirectional radiation characteristics in phi = 0° plane with lower cross‐polarization values.     

Step multiple quantum well enabled performance enhancement in InGaN/GaN based light-emitting diodes

In this work, we propose and investigate numerically InGaN/GaN based multiple quantum well (QW) blue light-emitting diodes (LEDs) with step quantum well (InGaN)/barrier (GaN) structures. We design four LED structures—(LED-A) InGaN/GaN rectangular quantum well, (LED-B) one down step in the middle of the QW created using sharp increase in In contents, (LED-C) one down step in the middle of the QW and the other down step in the right barrier away from QW and (LED-D) similar to LED-C barring one down step in the left barrier facing the QW. Using well-calibrated APSYS simulation program we compare the variation of output power and internal quantum efficiency of LEDs with input injection current and analyze them in the light of energy band diagram, electric field distribution, carrier concentration and radiative recombination rate. The proposed LED-D exhibits significant improvement in optical output power ~ 180.7% compared to conventional LED-A. Furthermore unlike other three LED structures, LED-D shows a very low internal quantum efficiency droop of 5.1% only at injection current of 120 mA.

     

Collapse voltage analysis of central annular ring metallized membrane based MEMS micromachined ultrasonic transducer

In this paper we have explored central annular ring metallized capacitive micromachined ultrasonic transducer (CMUT) structure. The metallization is done partially and it is patterned in such a way that it forms a flat ring on the surface of the membrane. This will decrease the price of the device as the need of metallization is less. Moreover, it is seen that the maximum displacement that the membrane can attain just before collapsing does not change even for partial metallization. It is perceived that with decreasing the area of the electrode the collapse voltage increases and vice versa. Changing the gap height has a huge impact on the collapse voltage. We have also examined the effect of different membrane materials on collapse voltage. Changing the membrane thickness hardly affects the value of collapse voltage. The electrode thickness is infinitesimally small as compared to the membrane thickness and is neglected in the analytical modeling approach. The analytical results are compared with three-dimensional (3-D) finite element method (FEM) model results. Excellent agreements between them are observed.

     

Circular footings resting on geotextile-reinforced sand bed

The note pertains to an experimental study made on circular footings resting on semi-infinite layer of sand reinforced with geotextiles. Using the concept of homogenization of such soils, both analytical and numerical analyses have also been conducted to predict the load-settlement behavior and compared with experimental observations. The study highlights the effect of the footing size, number of reinforcing layers, reinforcement placement pattern and bond length and the relative density of the soil on the load-settlement characteristics of the footings.     

Preparation and Characterization of Ni-Ferrite Coating on Carbon Steel Coupons

1.IntroductionTheinteractionofhightemperaturewaterwithcarbonsteel(CS)structuralsurfacesundertheprimaryheattransport(PHT)chemistryconditionsresultsintheformationofaprotectivemagnetitefilmwhichhasabilayerstructure.TheoxidelayerclosetometalgrowsintoitduetoO2-movementandoxi-dationofiron.Theouterlayerisformedbyprecipita-tionofFe3O4duetosupersaturationofthecirculat-ingcoolallt.Therelativemagnitudeofthethicknessofthetwolayersandtheirvariationwithtimeareaffectedbymanyfactors.Theporosityofthefilmgi…     

Design of filtering directional coupler with improved performance

This letter presents a filtering directional coupler (FDC) with enhanced coupling and high directivity simultaneously. The proposed FDC is composed of a pair of coupled lines instead transmission line of a directional coupler. This coupled lines resonator increases the design parameters by which even/odd mode phase velocity can be compensated to improve the directivity and coupling level. The coupling enhancement can be explained by analyzing the even mode and odd mode circuit of the proposed coupler. A prototype of the proposed coupler is designed which provides a high directivity of 44 dB for 6 dB coupling level at 1 GHz frequency. The proposed coupler is designed, fabricated, and tested.