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Applications: Engineering with Ceramics
Published in David W. Richerson, William E. Lee, Modern Ceramic Engineering, 2018
David W. Richerson, William E. Lee
Much of the heat supplied to or produced in an industrial process is not efficiently used and goes up the stack as waste heat. For example, only 10% of the heat supplied to a combustion-heated glass-melting furnace is actually used to melt the glass; 67% escapes with the exhaust. The purpose of a heat exchanger is to reclaim a portion of this waste heat to preheat incoming air (such as combustion air) or process reactants.7 Ceramic heat exchangers have been demonstrated that can salvage enough heat to reduce energy input or fuel consumption by nearly 50%.
Transient conduction
Published in Tariq Muneer, Jorge Kubie, Thomas Grassie, Heat Transfer, 2012
Tariq Muneer, Jorge Kubie, Thomas Grassie
The current sheet glass tempering systems used by industry to toughen glass typically use the technique of blowing air over the glass as it leaves the furnace to cool and temper the glass. For toughening thin glass this involves very high capital and running cost as the fans for such systems are very large and expensive. For a 6 mm glass, the temperature from the furnace exit is typically around 620°C. The surface temperature of this heated glass has to drop to below 520°C within 4 s to reach the desired ‘strain point’. Owing to the fact that air is not a very effective medium for heat transfer large volume rates are required to cool the glass surface quickly enough to temper the glass. This requires a large blower, and blowers for these systems are typically of the order of 200–400 kW or more in capacity. A more effective method of cooling the glass surface would be to use the heat of vaporisation of water to extract heat at sufficient rates to temper the glass. This would involve relatively small quantities of water being sprayed in a fine mist-like fashion onto the glass surfaces to quench the glass. The main problem associated with water-cooling is the possibility of large sized droplets contacting the glass which may cause the glass to break. However, with a good design this problem may be addressed, thus enabling large energy savings. In the design of such a facility a transient conduction analysis of the quenching process is to be undertaken. Consider a 1.5 m2 sheet of glass that is 6 mm thick, which is to be quenched by water at 90°C under film boiling regime (assume convection heat transfer coefficient h of 375 W/m2 K). Determine the transient temperature profiles and the heat flux rates. Compare the above results with conventional cooling undertaken with air blowers, with a convection heat transfer coefficient of 180 W/m2 K. Use the following thermophysical properties of glass: thermal conductivity: 1 W/m K, density: 2800 kg/m3, and specific heat: 840 J/kg K.
Fluid structure governing the corrosion behavior of mild steel in oil–water mixtures
Published in Corrosion Engineering, Science and Technology, 2020
Zi Ming Wang, An Qing Liu, Xia Han, Xing Zhang, Lin Zhao, Jian Zhang, Guang-Ling Song
The oil–water mixtures used for microstructure analysis were sampled via the solution out pipe at the autoclave bottom just after corrosion test. The emulsion could keep stable within a short period and it assumed that the sampled liquid could be representative to the emulsion state of the fluids. For the 200 rev min−1 case, the oil–water mixture before injection into the autoclave was also sampled for observation. A small drop of mixture was randomly picked and quickly spread onto a pre-heated glass slide; the pre-heating temperature was 80°C. This process aimed at producing a slightly transparent thin layer of oil–water mixtures for an easy identification of different phases at the microscopic scale. The heated glass slide would be quickly cooled to room temperature within several minutes, quenching and preserving the emulsion structure. Microstructure was observed using an optical stereomicroscope (Leica FusionOptics™ M205C) with a maximum magnification of 160 times. The images were analyzed by ‘Leica Application Suite’ software (Copyright 2013 Leica Microsystems (Switzerland) Limited). For a better identification of the distribution and size of water droplets in oil–water mixtures, the images were adjusted by the aid of Image-Pro Plus software, producing a sharp contrast and a clear edge between these two phases.
Mesogens with central naphthalene core substituted at various positions
Published in Liquid Crystals, 2018
Václav Kozmík, Eva Rodinová, Tereza Prausová, Jiří Svoboda, Vladimíra Novotná, Ewa Gorecka, Damian Pociecha
Textures and their changes have been observed under a polarising microscope Eclipse E600Pol (Nikon, Tokyo, Japan). Sample cells were prepared from glasses with ITO transparent electrodes (5 × 5 mm2) separated by two mylar sheets, which were used to define the cell thickness (usually of about 3 µm). The glass cells were filled by studied compounds in the isotropic phase by capillary action. Commercial cell with surfactant ensuring a homogeneous anchoring (planar geometry) has been used as well. The Linkam LTS E350 heating/cooling stage with TMS 93 temperature programmer (Linkam, Tadworth, UK) was used which enabled temperature stabilisation within ±0.1 K. One-free-surface samples were prepared as thin films on a heated glass surface.
Experimental investigation of a solar energy based cooking system for the steam method of cooking using evacuated tube collector
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Ranjan Chaudhary, Lokesh Pandey, Avadhesh Yadav
The experimental set up accommodating evacuated tubes was exposed to radiations at 7:00 h and the solar collector started absorbing these radiations. Consequently, layer of (Al-N/Al) gets heated up due to capturing of thermal energy of solar radiations. Since, the vacuum is present within the two glass tubes, the loss of heat is minimized to a large extent. Hence, the transfer of energy from solar radiations is effectively converted in to thermal energy and inner most tube gets heated up. The heated glass tube further transfers its heat to thermal oil which was present in the cavity of the evacuated tubes. After gaining heat, the temperature of thermal oil starts rising up and its density starts decreasing. The decrease in density of heated oil forces it to rise up in the evacuated tube and consequently the cold fluid slides down. After rising through the tubes, hot thermal oil enters in to the header. The thermal oil possessing comparatively low temperature slides to downward position in the header. This flow behavior results in the rise of thermal oil to the SCP through insulated steel pipes. The thermal oil possessing high temperature passes through the Chamber II and transfers its energy to the bottom face of Chamber I. Hence, the heat from the Chamber II is communicated to the water present in Chamber I. After the gain of temperature nearly to boiling point, vapors starts rising from the water and contacts with the food kept in the assemblies of SCP for cooking. Assemblies A1 and A2 were utilized for the cooking of idli and dhokla, respectively, and assembly A3 was used for the cooking of momos. Prerequisite material for the cooking of respective food stuff is listed in Table 4.