Study of Heat Transfer Rate in Electric Evaporators of Liquefied Petroleum Gas Using Electrothermal Modeling

In modern domestic and foreign experience of gas power supply to houses and industrial facilities located remotely from the main power station, decentralized gas power supply systems fed with propane-butane mixtures of liquefied petroleum gases from tanks are increasingly used. When using liquefied petroleum gases as the main energy carrier in gas tank systems, they are evaporated artificially in evaporators with an intermediate solid-state or liquid heat transfer agent, under conditions of its natural convection. The main operational characteristic of industrial tube evaporators of propane-butane mixtures of liquefied petroleum gases used for gas power supply from tank installations of housing and communal, industrial and industrial facilities that are remote from the main power supply stations is evaporation capacity. The evaporation capacity of industrial tube evaporators of propane-butane mixtures with a solid-state intermediate heat transfer medium is determined by the heat input from the tubular electric heaters through the aluminum casting layer. Therefore, the study of heat transfer in the solid–state intermediate heat transfer medium-evaporation coil system is the most important prerequisite for the effective operation of industrial tube evaporators of propane-butane mixtures and requires detailed research. To solve the problem of determining the heat transfer resistance between the layers of aluminum casting in contact with the surface of the tubular electric heaters group and the outer evaporation coil surface studies were performed on an electrical model. The average value of the total error of the results of experimental studies on electrothermal modeling is 3.7 %, with a confidence probability of 95 %. Recommendations are given for reducing the thickness of the layers in clear from the lower coil of the evaporative tube coil to the lower generatrix of the solid-state aluminum mass and the upper coil of the evaporative tube coil to the upper generatrix of the solid-state aluminum mass.

A Mechanistic Study of Clustering and Diffusion of Molybdenum and Rhenium Atoms in Liquid Sodium

Liquid Na is widely used as the heat transfer medium in high-temperature heat pipes based on Mo-Re alloys. In this study, ab initio molecular dynamics are employed in order to understand the interactions between the Na solvent and Mo or Re solute in the liquid phase. Both the temperature and concentration effects on the clustering and diffusion behaviors of solute atoms are investigated. It is found that Mo2 and Re2 dimers can be stabilized in liquid Na, and the higher temperature leads to a stronger binding force. Pure Re and Mo-Re mixed solutes can form tetramers at the highest concentration. However, for the pure Mo solute, Mo4 is not observed. The diffusivities of a single solute atom and clusters are calculated. It is found that the Mo species diffuse faster than the Re species, and the diffusivity decreases as the cluster size increases.

Application Methods for Refractory Insulation in Hot Particle Storage Bins

The National Solar Thermal Test Facility (NSTTF) at Sandia National Laboratories is conducting research on a Generation 3 Particle Pilot Plant (G3P3) that uses falling sandlike particles as the heat transfer medium. G3P3 proposes a system with 6 MWh of thermal energy storage in cylindrical bins made of steel that will be insulated internally using multiple layers of refractory materials[1]. The refractory materials can be applied by stacking pre-cast panels in a cylindrical arrangement or by spraying refractory slurry to the walls (shotcrete). A study on the two methods determined that shotcrete would be the preferred method in order to minimize geometric tolerance issues in the pre-cast panels, improve repairability, and to more closely resemble commercial-scale construction methods. Testing and analysis was conducted which showed shotcrete refractories could be applied with minimal damage and acceptable heat loss.

Investigation of the Degree of Augmentation of the Mass Transfer Coefficient of the Heat Transfer Medium in a Vortex Heat Exchanger of a Gas Pressure Regulating and Metering Station Heating System

Purpose of research. is to investigate the degree of augmentation of the mass transfer coefficient of a heat transfer medium in contact with a "spot" of liquid on the surface of the vortex blade when it is bombarded with dispersed contaminants in a vortex heat exchanger in order to identify a pattern that allows obtaining design values of the heat transfer coefficient of the heat transfer medium that have the best agreement with the experimental values provided in previously published articles [4, 6, 7].Methods. A complex analysis of the degree of augmentation of the mass transfer coefficient of the heat transfer medium on the surface of the vortex blade in a vortex heat exchanger based on the known theoretical positions and equations of heat and mass transfer processes.Results. The dependence of the augmentation of the mass transfer coefficient of the heat transfer medium in contact with the "spot" of liquid on the surface of the vortex blade when it is bombarded with dispersed contaminants was obtained, which allows obtaining the best agreement of the design and experimental values of the heat transfer coefficient in the vortex heat exchanger of a gas pressure regulating and metering station.Conclusion. The values of the heat transfer coefficient of the heat transfer medium calculated using the obtained dependence of the augmentation of the mass transfer coefficient of the heat transfer medium have a satisfactory convergence with the experimental data, which allows us to use this dependence in engineering calculations of the design parameters of the vortex heat exchanger used as a heat exchanger for the heating system of the working area of the gas pressure regulating and metering station. This technical solution allows not only saving natural gas as a source of heat generation, but also reducing the negative impact on the environment, since there is no need to burn natural gas. In this case, the production of thermal energy is carried out due to a regulated pressure drop of natural gas coming from the main line to consumers.

Synthesis and Characterization of Novel Ternary Hybrid Nanoparticles as Thermal Additives in H2O

The performance of water as a heat transfer medium in numerous applications is limited by its effective thermal conductivity. In order to improve the thermal conductivity of water, herein we report the development and thermophysical characterization of a novel metal-metaloxide-carbon based ternary hybrid nanoparticles (THNp), GO-TiO2-Ag and the rGO-TiO2-Ag. The results indicate that the graphene oxide and reduced graphene oxide based ternary hybrid nanoparticles dispersed in water enhance its thermal conductivity by 66% and 83%, respectively, even at very low concentrations. Mechanisms contributing to this significant enhancement are discussed. The experimental thermal conductivity is plotted against the existing empirical hybrid thermal conductivity correlations. We found that those correlations are not suitable for the metal-metaloxide-carbon combinations, calling for the developing a new thermal conductivity models. The rheological measurements of the nanofluids display non-Newtonian behavior, and the viscosity reduces with the increase in temperature. Such behavior is possibly due to the non-uniform shapes of the ternary hybrid nanoparticles.

Synthesis and Characterization of Novel Ternary Hybrid Nanoparticles as Thermal Additives in H2O

The performance of water as a heat transfer medium in numerous applications is limited by its effective thermal conductivity. In order to improve the thermal conductivity of water, herein we report the development and thermophysical characterization of a novel metal-metaloxide-carbon based ternary hybrid nanoparticles (THNp), GO-TiO2-Ag and the rGO-TiO2-Ag. The results indicate that the graphene oxide and reduced graphene oxide based ternary hybrid nanoparticles dispersed in water enhance its thermal conductivity by 66% and 83%, respectively, even at very low concentrations. Mechanisms contributing to this significant enhancement are discussed. The experimental thermal conductivity is plotted against the existing empirical hybrid thermal conductivity correlations. We found that those correlations are not suitable for the metal-metaloxide-carbon combinations, calling for the developing a new thermal conductivity models. The rheological measurements of the nanofluids display non-Newtonian behavior, and the viscosity reduces with the increase in temperature. Such behavior is possibly due to the non-uniform shapes of the ternary hybrid nanoparticles.

Using CFD to improve the performance of a heat exchanger from a gasifier

In this paper, a Computational Fluid Dynamics (CFD) analysis is performed on a gas-liquid heat exchanger fitted on a gasification equipment. The flow and temperature patterns are preliminary investigated using SolidWorks Flow Simulation software, in order to gain insight into the involved physical processes, and to find the exchanger weak points before being manufactured and tested. The analysed equipment tranfers heat from the flue gasses generated by a gasification system, towards a liquid heat transfer medium. This is subsequently sent to a second liquidliquid heat exchanger used to heat water from a boiler. As a result of the analysis, solutions aiming at performance improvement of the equipment are discussed and proposed.

Performance Improvement of Base Fluid Heat Transfer Medium Using Nano Fluid Particles

Base fluids like water, ethylene glycolandengineoilare conventionally used as a heat transfer medium. The performance of heat transferred is improved in the conventional fluids with the addition of Nano particles. Hence, this paper considers the forced conventional flow problem over the base fluid within a uniform heated tube placed on a wall. The analysis of heattransferco-efficientis done through a constant Reynoldsnumberfor both Nano and base fluid with a simulation tool. Further, a comparative analysis is carried out with heat transfer coefficient over the base and various Nano fluids. It is seen that the Nano fluids has a better performance due to its better thermal characteristics under standard conditions.

A Review on Heat Transfer of Nanofluids by Applied Electric Field or Magnetic Field

Nanofluids are considered to be a next-generation heat transfer medium due to their excellent thermal performance. To investigate the effect of electric fields and magnetic fields on heat transfer of nanofluids, this paper analyzes the mechanism of thermal conductivity enhancement of nanofluids, the chaotic convection and the heat transfer enhancement of nanofluids in the presence of an applied electric field or magnetic field through the method of literature review. The studies we searched showed that applied electric field and magnetic field can significantly affect the heat transfer performance of nanofluids, although there are still many different opinions about the effect and mechanism of heat transfer. In a word, this review is supposed to be useful for the researchers who want to understand the research state of heat transfer of nanofluids.