Application of RC delay time for estimation of thermal properties

The analogy between the electrical and thermal system has been extensively used to solve different kinds of direct heat transfer problems. However, this analogy has not been explored much to obtain solutions of inverse heat transfer problems like estimation of thermal properties. This paper presents an approach of estimation of thermal properties using the correspondence between the thermal and electrical domains by exploiting the concept of RC delay time in the resistance-capacitance (RC) circuit. Simulations and experiments have been performed on stainless steel and glass samples to show the applicability of the proposed approach for materials belonging to different conductivity range.

Dar Zarrouk Parameters for delineation of groundwater potentials in Ganye and Environs, Adamawa State, Northeastern Nigeria

Groundwater is the main source of water supply in areas in Nigeria including the research area. The research is aimed at delineating groundwater potentials in Ganye and environs using Dar Zarrouk parameters. Fourteen (14) vertical electrical soundings were conducted across the study area in order to determine Dar Zarrouk parameters to determine groundwater potentials in Ganye and environs. The area is underlain by migmatite-gneiss and Pan African granites. Weathered/fractured basement constitute the aquifer type in the area. The aquifer conductivity in the study area range between 0.00871 to 0.032032 ?-1 with mean value of 0.019493 ?-1. The aquifer longitudinal conductance ranges between 0.22246 to 0.759252 with mean value of 0.432846. The transverse resistance range between 627.8721 to 1,857.282 ?m2 with average value of 1,235.854 ?m2. The aquifer hydraulic conductivity range between 6.9314 to 15.562 m/day with mean value of 9.738 m/day while the transmissivity across the study area range between 114.2152 to 378.774 m2/day with mean value of 216.0487 m2/day.

A comparative study of honeycomb-like 2D π-conjugated metal–organic framework chemiresistors: conductivity and channels

Honeycomb-like 2D π-conjugated conductive metal–organic framework gas sensors with channel sizes <2 nm and broad conductivity range are studied with low conductivity facilitating response, multi-porosity and short channel resulting in fast speed.

A Simplified Thermal Design Model for a Single Vertical U-Tube Borehole Utilized in Ground-Coupled Source Heat Pumps

The present work dealt with the thermal assessments of the ground-coupled heat pump heat exchangers utilized in the field of geothermal energy source. A model was performed to predict the overall thermal resistance of a single vertical heat exchanger embedded in the borehole. The philosophy of the U-tube replacement with a single equivalent tube size was implemented with new development. Four tube sizes were used to build several borehole geometry configurations, they were (9.53) mm, (12.7) mm, (15.88) mm, and (19.05) mm accommodated in borehole sizes of (65) mm, (75) mm, (90) mm, and (100) mm respectively. Twelve borehole geometry configurations were examined as DX condensers circulate R410A refrigerant. These geometry assemblies produced a range of (0.29-0.57) for tube spacing to borehole ratio tested at (0.73) W/m K to (1.9) W/m K filling thermal conductivity range. The results of the present correlation showed good agreement with previously published correlations in the open literature. A mean temperature difference between the condensed vapor refrigerant and soil was assumed to have existed as (14) °C. Increasing the tube spacing from (2) to (3) times the tube diameter exhibited an augmentation in the heat loading of the borehole. This rise in the heat loadings of the U-tube was (8-10) % and (13-17) % for the geometry configurations of (9.53) mm and (12.7) mm tube sizes respectively. The tube diameter has also shown its importance in the thermal process of the borehole. At (75) mm borehole size and tube spacing of (2) times tube outside diameter, the predicted borehole thermal resistance for (9.53) mm tube diameter was higher than that of (19.05) mm one by (78-80) % for the test range of grout thermal conductivity.

Taxonomic and ecological characterization of two Ulnaria species (Bacillariophyta) from streams in Cyprus

During a study of the diatoms of streams in Cyprus, two Ulnaria species were difficult to identify using current taxonomic concepts, which created difficulties when trying to understand their ecological preferences. As a result, both taxa were investigated in detail using light (LM) and scanning electron (SEM) microscopy. Literature searches showed that one of these corresponds to Synedra Monodi Guermeur, a “forgotten” species often misidentified as Fragilaria biceps. This species was shown to belong to the genus Ulnaria, and a new combination is provided together with LM and SEM illustrations and an expanded description. U. monodii appears to be widely distributed and was sometimes abundant. It is an important species in diatom assemblages in streams with relatively warm waters (Mediterranean or tropical / subtropical climate). The second species, one of several forms to which the name Ulnaria acus has often been inappropriately applied, is described as a species new to science (Ulnaria acuscypriacus sp. nov.). The new species differs from all similar taxa by a combination of characters including width, outline, central area shape, and the possession of biseriate areolae. A comprehensive environmental dataset allowed the ecological preferences of Ulnaria monodii comb. nov. to be established. This species was generally associated with low concentrations of total nitrogen and total phosphorus, corresponding to slightly nutrient enriched situations. By contrast, the low number of occurrences of U. acuscypriacus sp. nov. did not allow us to identify clear nutrient preferences. U. acuscypriacus sp. nov. was observed across a large conductivity range, suggesting that it may be more tolerant of brackish conditions than Ulnaria monodii comb. nov.

Preparation and Characterization of sPDVB/SPPO Composite Proton Exchange Membrane for Fuel Cell

In this study, a series of composite proton exchange membranes are prepared from sulfonated polydivinyl benzene (sPDVB) microspheres and sulfonated polyphenyl ether (SPPO). The PDVB microsphers and PPO are functionalized by direct sulfonation. The synthesis products are characterized by Fourier Transform Infrared Spectroscopy technique (FT-IR), thermogravimetry analysis (TGA), scanning electron microscope (SEM). The incorporation of sPDVB decreases the water uptake and proton exchange capacity, so the proton conductivity is lower than that of blank SPPO membrane. But the composite membranes still have the excellent conductivity range from 4.88×10-2 to 6.99×10-2 Scm-1.

Optimization of AC Electrokinetic Mixing by Nanocomposite Monolayer

The mixing of fluids using AC Electrokinetic is presented in this paper. Both AC electrothermal (ACET) and AC electroosmosis (ACEO) techniques are investigated for mixing operation. AC electrokinetic mixing utilizes the characteristics of short diffusion distance and large specific interface area, and the characteristics of laminar flow and multiphase flow in a microchannel. The proposed mixer will have advantages of easy implementation and compatibility with microchip fabrication. Furthermore low and high conductive fluid has been experimented for mixing operation. In this research, the ACET and ACEO mixing will be optimized by surface modification using a biocompatible hydrophobic nanocomposite monolayer. This coating will modify the mixer surface to a hydrophobic surface and improve the friction losses at the interface, and eventually increase the mixing rate. Both ACEO and ACET flow is a promising technique in microfluidic mixing toward laboratory automation applications, such as clinical diagnostics and high-throughput drug screening. But the mixing efficiency and type of AC electrokinetic usage depends on the conductivity range of the fluids. These mixers can be integrated with the lab-on-a-chip and can provide inexpensive disposable devices.

Studies on Dual Phase Conducting Polyaniline Magnetic Micro and Nanocomposites

The conducting polymers are vital sources for fabrication of micro electronics chips, GMR sensors, membranes and flexible electrodes. Polyaniline is widely chosen for such products because of its conductivity range. This paper focuses on the studies of dual phase properties of Polyaniline (PANI) - Magnetic Iron Oxide (MIO) composites wherein MIO micro and nanoparticles were incorporated in polyaniline. This type of MIO-Polyaniline composites can enhance both conductive and magnetic property. Polyaniline was synthesized by redox polymerization technique with MIO both in micro and nanosize by in-situ polymerization. The MIO content was maintained at 0.2 to 0.6 gm with respect to 4.6 gm of aniline in polymerization reaction. The composites were characterized by FTIR, UV, XRD, SEM and VSM and conductivity unit. The saturation magnetization of composites was 0.0057 emu/g for 0.6 MIO micro spheres and 1.5507 emu/g for 0.6 MIO nanospheres. The DC conductivity values for pure PANI are 2.06x10-2 S/cm , 5.13x10-3 S/cm for PANI-0.6 micro MIO and 1.13x10-3 S/cm for PANI-0.6 nanoMIO. Micro tubular structure was observed for PANI composite in SEM . It is evident that the electrical properties are altered significantly on tailoring MIO in microtubes and the magnetic property is altered by tuning the composition of MIO from micro to nanorange. These composites will satisfy the properties for applications such as actuators, supercapacitors, EMI shielding, Fuel cells and Sensors. Key words: Polyaniline, Microtubes, Magnetic iron oxide, DC conductivity