Experimental Study on Horizontal Fire Spread Characteristics of Transformer Oil

In order to study the horizontal fire spread characteristics of transformer oil, a series of experiments were carried out on the experimental platform developed, the influence of the initial temperature and the width of the oil pool on the flame propagation, including the propagation speed, flame morphology and the temperature field distribution of the gas-liquid two-phase, was analyzed to reveal the flame propagation characteristics and the oil surface temperature rise law in the process of transformer oil fire propagation, and a theoretical model of coupled liquid-phase convective heat transfer and flame radiation heat transfer was established by combining thermodynamic theory to quantitatively calculate the heat transfer process of surface flow in flame propagation process. Through the theoretical analysis and quantitative calculation of gas-liquid heat transfer, it is proved that the surface flow is mainly driven by surface tension and the flame spreads in the form of pulsation. Combined with the experimental data for verification, it is found that the proportion of liquid-phase convective heat transfer to the total heat flow is much larger than that of flame radiation to the total heat flow, which proves that liquid-phase convective heat transfer is the main mode of surface flow heat transfer.

Heat transfer estimation through a high-temperature geothermal field in New Zealand quantified by multi-channel data modelling

<p>In high-temperature geothermal systems, understanding heat transfer helps conceptualize the whole system as well as estimating the resource size. To obtain the fullest picture, it is necessary to integrate different types of data, e.g., surface electromagnetic surveys, wellbore lithology, geochemistry, and temperature logs. This can be achieved through joint modelling. Here, we quantify the spatial distribution of heat transfer through the hydrothermally-altered, impermeable smectite layer that has developed atop the Wairākei-Tauhara geothermal system, New Zealand. Our approach involves first constraining 1D magnetotelluric (MT) inversion models with methylene blue analysis (MeB, an indicator of conductive smectite clay) and mapping these onto temperature and lithology data from geothermal wells. Then, one-dimensional models of heat transfer are fitted to well temperature logs to estimate heat flux variations across the field. We use our integrated method to estimate the average heat flux through the clay cap (2.2 W/m2) and total heat flow (380 ± 21 MW) of the Wairākei-Tauhara geothermal field. This approach models multiple datasets for estimating heat fluxes and could be applied in geothermal provinces around the world with implications for sustainable resource management and our understanding of magmatic systems.</p>

Effects of Temperature on Lifespan of Drosophila melanogaster from Different Genetic Backgrounds: Links between Metabolic Rate and Longevity

Despite many studies of the aging process, questions about key factors ensuring longevity have not yet found clear answers. Temperature seems to be one of the most important factors regulating lifespan. However, the genetic background may also play a key role in determining longevity. The aim of this study was to investigate the relationship between the temperature, genetic background (fruit fly origin), and metabolic rate on lifespan. Experiments were performed with the use of the wild type Drosophila melanogaster fruit flies originating from Australia, Canada, and Benin and the reference OregonR strain. The metabolic rate of D. melanogaster was measured at 20 °C, 25 °C, and 28 °C in an isothermal calorimeter. We found a strong negative relationship between the total heat flow and longevity. A high metabolic rate leads to increased aging in males and females in all strains. Furthermore, our results showed that temperature has a significant effect on fecundity and body weight. We also showed the usefulness of the isothermal calorimetry method to study the effect of environmental stress conditions on the metabolic activity of insects. This may be particularly important for the forecasting of impact of global warming on metabolic activity and lifespan of various insects.

EFFICIENCY OF SOLAR PROTECTION OF THE MOBILE AGRICULTURAL MACHINE CAB

The article checks the effectiveness of translucent enclosing structures of the tractor cab in reducing solar radiation. For this purpose, the value of the total heat flow entering the interior during the entire working day was determined, which was later compared with the hygienic standards. The result demonstrated an average low efficiency of the tractor cab sun protection. In this regard, the use of more effective shading elements and the use of glass with increased light and heat protection properties in light openings is proposed.

Effect of Thermophysical Property Variation on Entropy Generation towards Micro-Scale

In this work, the effect of temperature-dependent thermal conductivity (k(T)) and viscosity (\mu (T)) variation on entropy generation in circular channels with an approach from macro- to micro-scale is numerically investigated. Thermally as well as hydrodynamically fully developed flow of water through the fixed length channels with constant total heat flow rate and total mass flow rate is considered. The effects of k(T) variation and \mu (T) variation on entropy generation are analyzed individually as well as collectively. It is observed that in the case of Constant Property Solutions (CPS) {S_{\mathit{gen},\mathit{tot}}} is maximum at the macro-level; however, in the case of combined k(T) and \mu (T) variations it is maximum at the micro-level. The Bejan number (\mathit{Be}) and irreversibility distribution ratio (φ) are also calculated for asserting the dominance of frictional irreversibility and conduction heat transfer irreversibility. Additionally, the optimum diameter ({D^{\ast }}) corresponding to the optimum number of channels is calculated at minimum total entropy generation. It is observed that {D^{\ast }} is minimum for k(T) variation followed by CPS, \mu (T) variation, and combined k(T) and \mu (T) variations.

“A REVIEW OF HEAT DISSIPATION ANALYSIS BY VARYING GEOMETRICAL CONDITION OF CYLINDRICAL FIN”

If the heat in the heat engine is not removed properly, it causes the development of the detonation and eventually reduces the efficiency of the engine, so that the heat dissipation rate of the cylinder an important and interesting task is the option. The cylinder of the engine is one of the most important automotive components, variations of high temperature and thermal loads. To cool the cylinder, the ribs are provided on the surface of the cylinder, to increase the rate of heat transfer. By a thermal analysis of the motor cylinder and the ribs that surround it, it is useful to know the heat transfer rate and the temperature distribution inside the cylinder. We know that we can increase the heat dissipation rate by increasing the surface so it is very difficult to design such a complex motor. The main objective of this project is to analyze thermal properties such as thermal directed flow, total heat flow and temperature distribution. The cooling mechanism of the air cooled engine depends mainly on the design of the cylinder head and the block ribs. The cooling fins are used to increase the heat transfer rate of the specified surface. The life and efficiency of the engine can be improved by efficient cooling. The finite element method was used using the ANSYS software as a simulation tool for analysis.

Efecto de la Corriente y Longitud de Arco en Soldaduras con Arco Eléctrico Asistido por Modelado Matemático

A 2D mathematical model was developed for the GTAW arc welding process (Gas Tungsten Arc Welding). Computational simulations were performed by using the commercial software PHOENICS based on mass and momentum conservation equations as well as on Maxwell equations. The model predicts the electric characteristics of the arc column, flow patterns, temperature profiles, heat flux, total heat flow and the electrical potential, by varying the arc length and the applied current. By increasing the current the arc jet is stronger, hotter and provides more heat to the weld pool, while by increasing the arc length the maximum temperature, maximum velocity and heat flow are unchanged, although a short arc focuses the heat in a small area and a long arc spreads the heat in a wider area of the work piece.Keywords: Electric arc, heat transfer, fluid flow, mathematical modeling.

Investigation of Morphology of Recycled PET by Modulated DSC

During research injection molded samples were made from recycled poly (ethylene terephthalate) (PET). Morphological properties of samples were investigated by modulated differential scanning calorimetry (MDSC). Total heat flow was separated in two parts, reversing and non-reversing heat flow during measurements. Relationships were found between crystallization and melting processes: the initial crystallinity equals to the non-reversing melting, and the post-crystallization processes equals to reversing melting.

The Influence of Spherical Nano-SiO2 Content on the Thermal Protection Performance of Thermal Insulation Ablation Resistant Coated Fabrics

In the high temperatures experienced in fire, radiant heat accounts for 80% of the total heat flow; therefore, improving the radiation protection is the best way to enhance the thermal protective performance of thermal insulation ablation resistant coated fabrics. To achieve this goal, the coating process and the ingredients used were optimized, spherical nano-SiO2 and other particles were added, and thermal insulation ablation resistant coated fabrics with high radiant heat reflectivity were prepared. The influence of the spherical nano-SiO2 content on the thermal protection performance of the prepared coated fabrics was investigated. Research showed that (1) the radiant heat reflectivity of the prepared coated fabrics improves significantly with increasing content of spherical nano-SiO2; when the mass fraction of spherical nano-SiO2 is 15%, the reflectivity of coated fabrics is at its largest, and its average value was 74.30%. At present, the average size of grains in samples increased 1.9 times; (2) after adding the spherical nano-SiO2, the thermal stability of the thermal insulation ablation resistant coated fabrics is significantly improved; the residual mass is as high as 88.49% at 1200°C, which is 18.77% higher than the residual mass of the coated fabrics with no spherical nano-SiO2 added at the same temperature.

The Geothermal Field Analysis of Cooling and Heating Load Imbalance for GSHP

This paper developed a heat transfer model of the underground pipe group to study the effect of cooling and heating load imbalance to geothermal field. The results show that, there are the approximate linear relationship between average soil temperature and the total heat flow provided by GSHP system to the soil during the whole running period. The temperature of soil restoration ratio is less than the heat flux ration in the spring and autumn. Simulation results show that when heating/ cooling load equal to 0.5 and the heating flux for the bore hole are 60w/m and -40w/m in the Summer and Winter respectively, after this system run 12 months and 10 hours every day, the average soil temperature around borehole will increase 0.48°C, and the soil close borehole temperature will increase 1.3°C than the initial soil average temperature with the value of 17.6°C, which make GSHP not be efficiently for long term running. The results is hoped to be useful for GSHP design and long term running.