Measurements and simulations of transient characteristics of heat pipes
The rejection of heat generated by components and circuits is a very important aspect in design of electronics systems. Heat pipes are very effective, low cost elements, which can be used in cooling systems. This paper presents the modelling and measurements of the heat and mass transfer in heat pipes. The physical model includes the effects of liquid evaporation and condensation inside the heat pipe. The internal vapour flow was fully simulated using computational fluid dynamics. The theory has been compared with experimental measurements using thermographic camera and contact thermometers. The main purpose of this study is to determine the effective heat pipe thermal conductivity in transient state during start up the pipe operation and temperature increase.
U- and L-shaped heat pipes heat sinks for cooling electronic components employed a least square smoothing method
Abstract Heat pipes-heat sink modules transfer heat from a heat source to the heat pipes, and then to the heat sink and out into the surrounding ambient, and are suitable for cooling electronic components through a forced convection mechanism. The configuration and thermal performance of the heat sinks with inserted heat pipes were studied in the present paper. This article uses experimental procedures to investigate the thermal performance of two embedded U-shaped heat pipe and six embedded L-shaped heat pipe thermal modules with different fan speeds and heat source areas. And via the superposition method and least-square estimators in experimental data, the performance curves of individual U- and L-shaped heat pipes were derived and predicted. Results show that the lowest thermal resistances of U- and L-shaped heat pipe-heat sinks are respectively 0.246 °C/W and 0.166 °C/W given dual fans operating at 3000RPM and 30 × 30 mm2 heat sources. Results for a single U-shaped heat pipe are 0.04 °C/W at 78.85 W, while sequential results for L-shaped heat pipes are 1.04 °C/W, 2.07 °C/W, 2.76 °C/W, 2.19 °C/W and 1.7 °C/W between 34 W and 40 W.
Review of Literature on Probability of Detection for Magnetic Particle Nondestructive Testing
Abstract : A critical review of the available literature concerning the minimum reliably detectable defect size aNDI for magnetic particle testing (MPT) in aerospace applications is presented. Four probability of detection (POD) studies relevant to detection of fatigue cracks in aircraft components were found over the period 1968 to 2011. As the statistical methods used in these four previous studies were either outdated or otherwise deficient, the original data were reanalysed using currently accepted techniques. A meta-analysis of the results is presented, with emphasis on statistical inferences for the defect size expected to be detected with 90% POD. It is shown that the minimum reliably detectable defect size aNDI = 2.0 mm currently specified by the Royal Australian Air Force for wet fluorescent magnetic particle inspection using the continuous method is consistent with estimates of the average performance of MPT derived from the reanalysis of the literature.