Entropy generation of MHD flow of sodium alginate (C6H9NAO7) fluid in thermal engineering

In this paper, impacts of magnetic field and porosity on the entropy generation of sodium-alginate (C6H9NaO7) fluid are studied. C6H9NaO7 is taken over a moving and heated vertical wall. Heat transfer is due to free convection. Initially, the problem is formulated in the form of PDEs along with physical conditions and then written in non-dimensional form. Problem is solved via Laplace transform and expression in analytical form is established for temperature and velocity field. The related relations for entropy generation and Bejan number and entropy generation are also examined. Nusselt number and Skin-friction are calculated and plotted in graphs. For numerical computations, a finite difference scheme is used using MATLAB software. The results in tables and graphs are discussed for embedded parameters. It is found that the magnetic field and porosity have strong influence on velocity, entropy generation and Bejan number. For greater Hartman number, entropy generation magnitude is greater compared to the Bejan number, conversely, this variation in Bejan number is more efficient. The porosity effect showed that if the medium is more porous, the entropy generation can decreases 50% when porosity increase from Ka = 1 to Ka = 2, however the Bejan number increases.

Numerical framework for unsteady bioconvection flow of third-grade nanofluid over a porous Riga surface with convective Nield approach

The ultra-high significances of thermal radiation, magnetic field and activation energy in thermal enhancement processes allow significant applications in chemical and mechanical engineering, modern technology and various thermal engineering eras. The improvement in energy resources and production became one of the major challenges for researchers and scientists for sustained development in industrial growths. Beside this, the bioconvection assessment in nanomaterials conveys prestigious applications in biotechnology like bio-sensors, enzymes, petroleum industry, bio-fuels and many more. In view of such renewable applications, present exploration discloses unsteady two-dimensional flow of third-grade nanomaterial accommodating gyrotactic microorganisms induced by unsteady stretched Riga sheet in porous medium. The formulated flow problem is further scrutinized by utilizing the chemical reaction, activation energy, thermal radiation and magnetic aspects. The convective Nield constraints are further subjected in the current investigation. Apposite transformations are used to condense the nonlinear developed problem into dimensionless ordinary form. The numerical solution of such similar flow problem is presented via shooting technique. The detailed graphical illustrations of the dimensionless temperature, nanoparticles concentration, velocity and motile microorganisms for physical significance of diverse relevant parameters are deliberated. Furthermore, numerical data of local Sherwood, Nusselt and motile density numbers is designated in tabular form. Study accentuated that velocity increases for higher modified Hartmann and material constants, while the effects of buoyancy ratio and bioconvected Rayleigh numbers are rather opposite. The temperature, microorganism and concentration distributions were enhanced for unsteady parameter. It is also acknowledged that the concentration distribution is enhanced for activating the energy number. Moreover, the microorganism distribution enhances for concentration difference and magneto-porous constants, while bioconvected Lewis and Peclet numbers show conflicting trend.

Effect of Cryogenic Treatment on Density, Resistivity and Conductivity of Manganese Used in Lithium-Ion Batteries

Refrigeration is one of the core branch in the field of thermal engineering. In other words, we can say that the refrigeration is the sister branch of the thermal engineering or thermal science. The main purpose of refrigeration is to maintain the low temperature than the atmospheric temperature or simply room temperature. In a few decades, the new trends in the field of the refrigeration and air condition has been changed drastically. The need for the development of new refrigeration processes is to achieve possible minimum temperature by the liquefaction techniques such as linde claude system. The new field known as cryogenics is developed in recent few years whose main aim is to achieve the lowest possible temperature in order of -100 to - 1500 C. the cryogenics has a wide veriety of the applications ranging from space research to the medical science which can be supposed as a science fiction in the real life. Our research work is based on the analysis of the cryogenic treatment to the lithium ion battery to improve the performance of the battery for the long period. Keywords: Cryogenics, lithium ion batteries, manganese, density, conductivity

Photothermal Dye-based Subcellular-sized Heat Spot Enabling the Modulation of Local Cellular Activities

Thermal engineering at microscale such as the control and measurement of temperature is a key technology in basic biological research and biomaterials development, which remains challenge yet. Here, we engineered the polymeric nanoparticle, in which a fluorescent temperature sensory dye and a photothermal dye were embedded in its polymer matrices, termed nanoHT. When a near infrared laser at 808 nm is illuminated to the particle, it enables to create the subcellular-sized heat spot in a live cell, where fluorescence thermometry allows the read out of the temperature increment concurrently at individual heat spots. Owing to the controlled local heating, we found that the cell death of HeLa cells was induced at the certain temperature at rate of a few seconds. It should be also noted that the cell death was triggered from the very local heat spot at subcellular level. Furthermore, nanoHT was applied for the induction of muscle contraction of the C2C12 myotube by heat. We successfully showed that the heat-induced contraction took place at the limited area of a single myotube according to the alteration of protein-protein interactions related to the contraction event. These studies demonstrated that even a single heat spot provided by a photothermal material could be very effective in altering cellular functions, paving the way for novel photothermal therapies.

The Concept of Entropy and Its Application in Thermal Engineering

Today, 156 years after the invention of entropy by Clausius, there remains disagreement among the scientific community on what entropy and the phenomenon of entropy increase mean [...]

Cryogenic operation of NanoBridge at 4K for controlling qubit

A nonvolatile resistive switching of NanoBridgeTM (NB) at 4 K has been demonstrated for realizing the quantum-classical interface (QCI), in which the challenging of reset operation at cryogenic temperature is successfully achieved. The set voltage of the NB is increased with decreasing temperature, saturated around 150 K and to be 2.55 V at 4 K. The on-state resistances tuned at 1k-5kΩ show small temperature dependence down to 4 K due to high residual resistivity. The increased reset current of the NB at 4 K is compensated by the process optimization with thermal engineering and the increased Idsat of the select transistor at 4 K, resulting in the stable switching. The low-power QCI featuring NBs is a strong candidate for controlling a large number of qubits at cryogenic temperature.

Energy, Economic and Environmental Assessment of Thermal Barrier Application in Building Envelope Structures

Thermal engineering requirements for building structures are becoming more and more strict. Thermal barriers (TBs) are energy-active elements integrated into the building structure in which a heat transfer medium (water or air) flows. A survey of the scientific literature on the subject points to the fact that this is a very topical and promising area of research and, so far, most studies on TBs are based on calculations, computer simulations and experimental measurements. Few studies have focused on the economic and environmental aspects of TB use. Following the research results presented by authors from all over the world, as well as our contributions in this scientific field that are described in a European patent, three utility models and scientific articles, in this study we have focused on the evaluation of the TB in terms of energy performance, economic efficiency and environmental friendliness by comparing the use of a classical envelope wall with the required thickness of thermal insulation meeting the normative requirements for thermal resistance R ((m2K)/W) and a perimeter wall with an integrated TB significantly eliminating the thermal insulation thickness. We evaluate the use of the thermal barrier using: economic indicator one, where we compare the cost of heat delivered to the TB in a structure with significantly eliminated thermal insulation and the saved cost of thermal insulation at the standard thickness; economic indicator two, where we compare the cost of heat delivered to the TB in a structure with significantly eliminated thermal insulation with the potential gain from the sale of the useful area of the building gained compared to the area at the normative thickness of thermal insulation; and economic indicator three, where we compare the cost of heat delivered to the TB in a structure with significantly eliminated thermal insulation with the cost of grey energy at the normative thickness of thermal insulation. Based on a parametric study based on theoretical assumptions, it can be concluded that the thermal barrier shows a very promising and efficient solution in terms of the evaluation of economic indicators one to three, which are even more significant if we use heat for the TB from renewable energy sources (RES) or waste heat.