Papers by Keyword: High Heat Flux

Abstract: Metallic thermal barrier coatings (TBCs) consisting of a bond coating and a top coating have been extensively utilized for protecting the walls of rocket combustion chambers. However, standard coating systems often encounter failures due to the significant differences in coating composition and thermal expansion coefficient compared to the substrate under high heat flux conditions. To protect liquid rocket combustion chamber walls, a novel metallic multilayer TBC system applied with atmospheric plasma spraying is developed in the present work. It attempted to deposit dense Ni-based alloy and Cu-based bonding coatings with low oxide contents achieved by introducing boron as a deoxidizer element through atmospheric plasma spraying. The structural stability of the TBC was assessed through high temperature thermal exposure experiments, while the thermal cycle life is evaluated using laser thermal shock. Results show that the NiCrCu2B and CuNi2B bonding coatings prepared through in situ deoxygenation effect of boron exhibit dense structures, low oxide content, and excellent bonding quality. The high temperature thermal exposure experiment reveals that the multilayer structural TBC can withstand 850 °C for 10 hours without the formation of Kirkendal effect pores. Moreover, the thermal cycling life results indicate that the multilayer structural TBC designed in this study, employing a composition gradient transition and the in situ deoxygenation effect of boron, possesses a significantly improved thermal cycle lifetime compared to traditional structural TBCs.

Abstract: In this paper, the heat transfer characters of heat pipe radiator for cooling electronic device with high heat flux were investigated by visualization method. The surface temperature of heat pipe radiator was measured at different heat flux and constant fan speed of 0.7m/s, and the results show that the surface temperature of electronic apparatus is below 75°C for the heat flux 8W/cm2 at constant fan speed of 0.7m/s; The error in measured value using thermocouple and technique of infrared thermography was analyzed based on the principles of temperature measurement of infrared thermal imager.

Abstract: The realization of a fusion reactor is critically dependent on the successful development of high performance materials. Especially, the plasma facing components (PFCs) which basically consist of a direct plasma facing armor material and a heat sinking material. Tungsten (W) and Copper-alloy (CuCrZr) have been considered as the potential candidates for armor materials and heat sinking materials, respectively, due to their attractive nuclear and physical properties. However, due to the incompatibility of the coefficient of thermal expansion and the elastic properties between the W and the Cu-alloy as well as the non-homogeneous temperature distribution in PFCs, one of the crucial issues is the generation of thermally-induced residual stresses in W/CuCrZr PFC on cooling either during fabrication or during operation of fusion reactor. Therefore, the thermo-mechanical response of PFCs under high heat flux from the fusion reactor is a critical issue for the development of fusion technology. In the present work, in order to optimize the thermal and mechanical integrity of PFCs, thermally-induced residual stresses in W/CuCrZr PFCs with a compliant interlayer (OFHC-Cu: Oxygen Free High Conductivity Copper) are analyzed numerically by means of finite element method. Result indicated that the use of interlayer in PFCs could significantly reduce the magnitude and the concentration of thermally-induced stresses in comparison to the PFCs without interlayer. And also the optimum thickness for interlayer was suggested based on the current analysis conditions.

Abstract: A novel porous micro heat sink system is presented for thermal management of high power LEDs, which has high heat transport capability. Numerical model for the micro heat sink is developed to describe liquid flow and heat transfer based on the local thermal equilibrium of porous media, and it is solved with SIMPLE algorithm. The numerical results show that the heated surface temperature of porous micro heat sink is low at high heat fluxes and is much less than the bearable temperature level of LED chips. The heat transfer coefficient of heat sink is very high, and increasing the liquid velocity can enhance the average heat transfer coefficient. The overall pressure loss of heat sink system increases with the increasing the inlet velocity, but the overall pressure drop is much less than the pumping pressure provided by micro pump.

Abstract: A novel porous micro heat sink system was presented for dissipating high heat fluxes of electronic device. The flow and heat transfer of porous micro heat sink was investigated by experiment at the condition of high heat fluxes, and the results showed that the heat load of up to 280W was removed by the heat sink, and the heater junction temperature was 63.8°C at the coolant flow rate of 5.1cm³/s. The whole heat transfer coefficient of heat sink increased with the increases of coolant flow rate and heat load, and the maximal heat transfer coefficient was 33kW(m².°C)^-1 in the experiment. The minimum value of 0.19°C/W for whole thermal resistance of heat sink was achieved at flow rate of 5.1cm³/s, and increasing of coolant flow rate and heat fluxes could decrease the thermal resistance.

Abstract: The ITER Divertor is aimed at exhausting the major part of the plasma thermal power including alpha power and at minimizing the helium and impurity content in the plasma. It consists of assembly of 54 divertor cassettes. Each divertor cassette has three plasma-facing components (PFCs) and one cassette body that accommodates these PFCs. The PFCs consist of the Inner and Outer Vertical targets and the Dome. The Vertical Targets directly intercept the magnetic field lines and are designed to withstand heat fluxes as high as 20 MW/m2. After the successful completion of the qualification phase, three Parties (Japan, Europe and Russia) are qualified and they are in charge of procurement of the first Divertor set. In the paper, the detail component design and the manufacturing as well as the integration of the system are reported.

Abstract: The behavior of thick SiC gradient coatings on different graphites under high power electron beam irradiation, pulsed high energy laser impact, and HT-7 limiter plasma action was investigated. In the following tests at these facilities, the samples were examined using SIMS, EDAX, X-ray crystallography, profilometer and Auger spectroscopy. Thick SiC gradient coatings showed excellent durability under high heat flux and in real conditions of HT-7 limiter plasma irradiation. The primary results indicated that the use of multi-element doped graphite, GBST1308 (1%B4C, 2.5%Si, 7.5%Ti) with high thermal conductivity, as substrate will improve the durability of thick SiC gradient coatings significantly.