ITER magnetic sensor platform engineering analyses

Enhancing heat transfer performance of aluminum-based vapor chamber with a novel bionic wick structure fabricated using additive manufacturing

EM analyses on the 55.NE.V0 loom system and attached components

The purpose of this article is to experimentally investigate the effect of different pore size distributions in bidisperse wicks upon the heat transfer performance in a LHP. Three bidisperse wicks and one monoporous wick were tested in a loop heat pipe. The pore size distributions of the bidisperse wicks were measured, and the results reflected the three different large/small pore size ratios. The experiments showed that the maximum heat load of the monoporous wick reached about 400 W; and the three bidisperse wicks showed improvements on the maximum heat load up to 570 W. For the monoporous wick, the evaporator heat transfer coefficients of 10 kW/m2 K and total thermal resistance of 0.19°C/W were achieved at a high heat load of 400 W. For the better bidisperse wick, the evaporator heat transfer coefficients could attain about 23 kW/m2 K and total thermal resistance of 0.13°C/W. The results also indicated that a smaller cluster size in a bidisperse structure created a small pore size ratio. It was also found that the bidisperse wick with smaller clusters had a better enhancement in terms of the evaporator heat transfer coefficient.

Heat pipe dryout and temperature hysteresis in response to transient heat pulses exceeding the capillary limit

This paper specifically addresses the effect of changing the constant temperature region of the sintering temperature curve in manufacturing nickel powder capillary structure (wick) on the performance of a flat loop heat pipe (FLHP). The sintering temperature curve is composed of three regions: a region of increasing temperature, a region of constant temperature, and a region of decreasing temperature, with the sintering time and temperature in the region of constant temperature having significant effect on the permeability of the wick. In this study, for wick manufacturing the temperatures in this region tested range from 550°C to 650°C and the time from 30 minutes to 60 minutes. The properties and internal parameters of the wick are measured, and the wick is placed into FLHP for performance testing. Experimental results show that at sintering temperature of 550°C and lasting about 45 minutes, maximum heat load is 200W, minimum thermal resistance is 0.32°C/W, permeability is , porosity is 66%, effective porosity is 3.8and heat flux is around 21W/cm2; related literatures have only reported maximum heat load increase of 25%.

High power and high power densities due to absorbed radiation are significant design considerations which can limit performance of mirrors receiving highly collimated synchrotron radiation from insertion devices and bending magnet sources. Although the grazing incidence angles needed for x-ray optics spread the thermal load, localized, non-uniform heating can cause distortions which exceed allowable surface figure errors and limit focusing resolution. This paper discusses the suitability of numerical approximations using finite element methods for heat transfer, deformation, and stress analysis of optical elements. The primary analysis objectives are (1) to estimate optical surface figure under maximum heat loads, (2) to correctly predict thermal stresses in order to select suitable materials and mechanical design configurations, and (3) to minimize fabrication costs by specifying appropriate tolerances for surface figure. Important factors which determine accuracy of results include finite element model mesh refinement, accuracy of boundary condition modeling, and reliability of material property data. Some methods to verify accuracy are suggested. Design analysis for an x-ray mirror is presented. Some specific configurations for internal water-cooling are evaluated in order to determine design sensitivity with respect to structural geometry, material properties, fabrication tolerances, absorbed heat magnitude and distribution, and heat transfer approximations. Estimated accuracy of these results is discussed.

The present paper proposes a proof of concept of a completely passive thermosyphon for cooling of power electronics. This thermosyphon is composed of an evaporator to cool down a four-heater pseudo-transistor module and a natural air-cooled condenser to reject the heat into the environment. R1234ze, R1234yf, and R134a are used as the working fluids with charges of 524, 517, and 566 g, respectively, for the low charge tests, and 720, 695, and 715 g for the high charge tests. It has been demonstrated that the refrigerant R1234ze with a low charge is not a good solution for the cooling system proposed here since low evaporator performance and fluid instability have been detected at moderate heat fluxes. In fact, R1234ze needed a larger charge of refrigerant to be safely used, reaching a transistor temperature of 53 °C at a heat load of 65 W. R1234yf and R134a, on the other hand, showed good results for both the low and the high charge cases. The maximum temperatures measured, respectively, were 52 °C and 48 °C at 65 W for the low charge case and 55 °C and 47 °C at 62 W for the high charge case. The corresponding values of overall thermal resistances of the thermosyphon for the working fluids R1234yf and R134a at the maximum heat load are very similar, being in the range of 0.44−0.46 K/W.

A simplified mathematical model of the vehicle engine electronic control cooling system is established by using the lumped parameter method, and non-linear control strategy and fuzzy control strategy are introduced to simulate the cooling system. Taking the optimal coolant temperature of the vehicle engine outlet as the research objective, non-linear controller, fuzzy controller and self-adjusting fuzzy controller are designed to control the engine coolant temperature and to study the energy consumption optimization of the cooling system. Experiments show that compared with non-linear control, self-adjusting fuzzy control, and fuzzy control strategy, When the engine is in the maximum heat load and the electronic valve is fully open, the energy consumption of the cooling system can be reduced by 33% by using self-adjusting fuzzy control strategy.

The heat flux deposition pattern on the toroidal limiters installed in HT-7 was simulated with ANSYS code. The simulation model was established with the ripple of the magnetic field. The heat deposition pattern and temperature distribution on the surface of the toroidal limiters were obtained. A comparison of the results obtained with and without the shaped tiles, used to reduce the heat flux on the leading edge of the limiters, was made. The maximum heat load allowed at the leading edge was about 1.8 MW/m2 because of the poor power removing capacity on the ends of the limiters. This approach can also be applied to other devices with a limiter configuration in a circular cross-section shape.

Thermal effects are critical limit relevant to the power scaling of single crystalline fiber laser. In this paper, thermal effects in thin-rod single crystalline fiber are numerically researched. The simulation results show that thermal effects can be effectively reduced by enhancing the convective coefficient and decreasing the diameter of single crystalline fiber. For the most thin-rod single crystalline fibers utilized with diameter of 1 mm and length of 40 mm, the maximum heat load is only about 107 W due to the thermal rupture effect, which limits the laser output power to ~1 kW levels. The numerical results provide references for the developments and designing of thin-rod SCF laser

Characterization of composite mesh-groove wick and its performance in a visualizable flat-plate heat pipe

A refined method for calculating wind load combinations on open-framed structures

The performance of a bolted flange joint is characterized mainly by its ‘strength’ and ‘sealing capability’. A number of numerical and experimental studies have been conducted to study these characteristics under internal pressure loading conditions alone. However, limited work is found in the literature under conditions of combined internal pressure and axial loading. The effect of external, axial loading pressure being unknown, the optimal performance of the bolted flange joint cannot be achieved. Current design codes do not address the effects of axial loading on structural integrity and sealing ability. To study joint strength and sealing capability under combined loading conditions, an extensive experimental and numerical study of a non-gasketed flange joint was carried out. Actual joint load capacity was determined at both design and test stages with the maximum external axial loading that can be applied for safe joint performance. Experimental and numerical results have been compared and overall joint performance and behaviour is discussed in detail.

ABSTRACTGrouted connections have been widely used in offshore wind support structures to connect upper structures and lower foundations. Their mechanical behaviour is critical to the integrity of the entire support structure. In this study, numerical models were established and verified to investigate the stress distributions of grouted connections under combined compression and bending loads. It was found that the locations of shear keys had a significant influence on the maximum Mises stress in the steel tubes and Tresca stresses in the grout. The following parametric study of geometric configurations indicated that the thickness of a tube had a reverse relationship to the maximum stress. Meanwhile, the maximum Tresca stress was not sensitive to any geometric configurations, except grout thickness. Considering the gap between the detailed solid modelling and design process, based on beam modelling, a nominal average stress was computed over the compressed side of the steel tube within grouted connections. Consequently, stress correlation factors were obtained between the maximum Mises stress in a steel tube and the nominal average stress of a grouted connection. This method can be used in the preliminary design to evaluate the general behaviour of grouted connections under combined actions.

The paper presents the review and evaluation of the containment prestressing system within reinforced concrete structures under seismic loads and severe accidents. Given the complex design of the containment, the detailed finite element model has been developed and used to describe real containment behavior. Containment stress and strain state was calculated by modern LIRA software. The first stage analyzed the results of WWER-1000/320 containment stress and strain state calculation under a combination of loads caused by maximum design basis accident (MDBA) and safe shutdown earthquake (SSE) and defined minimum acceptable tension of tendons. The research determines the minimum acceptable tension of tendons in the containment prestressing system, and evaluates the strength and reliability of containment structures under a combination of loads in normal operation + design-basis accident + maximum design earthquake (NO + DBA + MDE). The verification calculations have been performed using tendon tension of 780 ton-force in the cylindrical part of the containment and 760 ton-force in the containment dome. The second stage covered the analysis of severe accident parameters (pressure and temperature) and the results of calculation. Stress and strain state in ZNPP-1 containment has been calculated, parameters (pressure and temperature) under which the containment can loss its protective and isolation functions have been identified, calculation results have been analysed and conclusions of containment structural integrity and ensuring the implementation of the design confining functions have been made. Based on the calculation results, it can be concluded that strength of the containment cylindrical part during a beyond design-basis accident cannot be ensured under parameters t (temperature) = 120°С, p (pressure) = 0.6 MPa.