Papers by Keyword: Thermal Barrier

Abstract: Heat resistant coatings are considered for the external surface Low-Pressure Steam Turbines (LPST). 410 stainless steel covered with nano heat resistant coatings consists of a heat resistant connecting layer enhanced by nanoparticles. A commercial paint was modified by using 20%wt of (titanium dioxide (TiO₂) - aluminum oxide (Al₂O₃)) with different concentrations range (25,50,75wt% of TiO₂) layers. These nano-coatings paints were airbrushed onto the surface of specimens of steam turbine blades. The test rig and experimental apparatus have been fabricated and collected to accomplish the thermal tests. The samples were subjected to heat resistance and a temperature test approximately similar to the steam turbine's operation condition temperature. The test results are used to choose the nano-coating layer with a concentration that ensures a composition's highest protective properties. The test sample with concentration (paint-(75% Al₂O₃+25% TiO₂)) showed the highest thermal properties compares with the other cases.

Abstract: In this work, the authors tried to solve a typical problem of inexpensive 3D printers using FDM technology: material clogging of the hotend. To cope with the problem, it is necessary to solve the problem of optimization the temperature regimes of the hotend. For this, the temperature fields of the heating device were simulated taking into account the physical properties of the printing materials. Modeling was carried out using the ANSYS software package, the verification of theoretical calculations was carried out in a full-scale experiment. The data obtained was used to upgrade the 3D printer hotend.

Abstract: In the present study, experiments were conducted to compare the effect of oxide layer formation on the piston crown coated using Micro-Arc Oxidation (MAO) with uncoated piston on the combustion and emission characteristics of the port injected Spark Ignition engine fueled by gasoline. The micro-arc oxidation (MAO) coating technique is the modern process to form a ceramic oxide layer on the reactive metal substrate (base metal) by electrochemical and electro-thermal oxidation in an alkaline electrolytic solution. Using MAO technique, an oxide layer of thickness 72 μm was formed on the piston crown. This oxide layer acts as a thermal barrier to reduce the in-cylinder heat rejection and increase the durability of the piston by withstanding high temperature and pressure produced during combustion. Combustion flames have been captured using the AVL combustion analyzer to analyze the development and propagation of flames within the engine cylinder. From the flame images, it was observed that propagation of flame was faster in MAO coated piston compared to uncoated piston. This is because of higher local temperature inside the combustion chamber that was resulted due to low thermal conductivity of MAO layer. It was also found that carbon monoxide (CO) and hydrocarbon (HC) emissions were reduced as a result of efficient fuel combustion, while NOx emissions increased because of increased combustion temperatures for MAO coated pistons. Keywords: Electro-thermal oxidation, Flame propagation, Micro-arc oxidation, Piston crown, Thermal barrie

Abstract: The main objective in building constructions is reducing energy consumption and increasing the proportion of renewable energy sources. We can find the various ways of reducing energy consumption, where the most used method is passive thermal protection and thus increasing thermal resistance of structures. There are also ways of active thermal protection, where one of the new ways is the system of TB (thermal barrier) using renewable energy sources to reduce heat loss through non-transparent parts of building envelope. It is one of the new types of thermal protection and there are not available clear rules for the design of the structures with TB and there are not quantified energy savings compared to buildings without a TB. TB decrease heat transmission only through opaque constructions, what is only one part of the total heat loss and thus is questionable payback period and primary energy consumption of TB system compared to the standard buildings. The paper is focused on comparison of temperatures in the wall construction with and without TB system and determining the external temperatures at which it is appropriate to apply a construction with TB.

Abstract: In this paper, mathematical model for heat transfer in thermal barrier is established based on the experiment which tested apparent heat conductivity of heat insulation oil pipes. Vacuum degree influence on performance of vacuum heat insulation oil pipe is analyzed by contrasting heat insulation oil pipes in different grades. The main conclusions are as follow. When internal pressure in the thermal barrier is between 0~20Pa or greater than 40Pa, the apparent heat conductivity increases with the pressure. And when internal pressure in the thermal barrier is between 20~40Pa, the apparent heat conductivity decreases with the pressure in volatility. When internal pressure in the thermal barrier is between 30~40Pa, the apparent heat conductivity of heat insulation oil pipe is lesser.

Abstract: In this paper, thermal barrier materials of mullite whiskers made by kyanite is studied, take -325~+400 mesh kyanite as raw material, the firing conditions is that nucleation temperature is 1150°C and crystallization temperature is 1250°C; the adding method of catalyst (AlF₃) is external additive. After the orthogonal experiment, it is determined that the effects order on products of raw material granularity, heating rate and catalyst addition is raw material granularity > catalyst addition > heating rate, and the best experimental conditions is obtained.

Abstract: In recent years, thermal barrier technologies have become an important energy-saving for space heating and cooling of residential and commercial buildings in many countries. Building energy efficiency can be improved by implementing either active or passive energy efficient strategies. Improvements to heating, ventilation and air conditioning systems etc. can be categorized as active strategies, whereas, improvements to building envelope elements can be classified under passive strategies. Using cooling wall system and phenolic resin as thermal barrier are one of the effective passive strategies. Cooling wall system is composed of galvanized iron pipes located inside of walls. Fluid flows inside the pipes and then supply constant cooling temperature. In the study, system using of groundwater as renewable energy source for pipes cooling. The groundwater at depth of more than 5 meters below the surface has constant temperature year round. Lower temperature groundwater would cool the pipes of system by heat exchange process to achieve the cooling effect of wall. The phenolic resin is proposed as construction materials to use its thermal insulation property for developing a comfortable living and working indoor environment. The phenolic resin is an environmental friendly material, and an excellent thermal barrier. In this research, cooling wall system and phenolic resin were evaluated to reduce the thermal transfer from sunlight into the buildings, thus reducing the electricity consumption needs for air conditioning of the buildings.