Quantitative assessment of the surface crack density in thermal barrier coatings

In this paper, a modified shear-lag model is developed to calculate the surface crack density in thermal barrier coatings（TBCs）. The mechanical properties of TBCs are also measured to quantitatively assess their surface crack density. Acoustic emission（AE） and digital image correlation methods are applied to monitor the surface cracking in TBCs under tensile loading. The results show that the calculated surface crack density from the modified model is in agreement with that obtained from experiments. The surface cracking process of TBCs can be discriminated by their AE characteristics and strain evolution. Based on the correlation of energy released from cracking and its corresponding AE signals, a linear relationship is built up between the surface crack density and AE parameters, with the slope being dependent on the mechanical properties of TBCs.

Thermal comfort assessment in civil aircraft cabins

Aircraft passengers are more and demanding in terms of thermal comfort. But it is not yet easy for aircraft crew to control the environment control system （ECS） that satisfies the thermal comfort for most passengers due to a number of causes. This paper adopts a corrected predicted mean vote （PMV） model and an adaptive model to assess the thermal comfort conditions for 31 investigated flights and draws the conclusion that there does exist an uncomfortable thermal phe- nomenon in civil aircraft cabins, especially in some short-haul continental flights. It is necessary to develop an easy way to predict the thermal sensation of passengers and to direct the crew to con- trol ECS. Due to the assessment consistency of the corrected PMV model and the adaptive model, the adaptive model of thermal neutrality temperature can be used as a method to predict the cabin optimal operative temperature. Because only the mean outdoor effective temperature ET＊ of a departure city is an input variable for the adaptive model, this method can be easily understood and implemented by the crew and can satisfy 80-90% of the thermal acceptability levels of passen- gers.

Inherently safer reactors and procedures to prevent reaction runaway

Reaction runaway has longtime been an issue in chemical industry as it often leads to severe accidents if not controlled and inhibited properly.Herein we have reviewed several key considerations and procedures to prevent such phenomena,including inherently safer reactor design,thermal risk assessment and early warning detection of runaway,and pointed out that the basic principle underlying is necessary heat management and construction of resilient processes.For inherently safer reactor design,important factors such as heat removal,heat capacitance,flow behaviors and explosive behaviors have been investigated.The survey shows that heat exchanger(HEX) reactor and microreactor outperform traditional reactors.Meanwhile,we have looked into the effect of thermal risk ranking and safety operation region determining for thermal risk assessment,and the influence of runaway criteria and construction methods for early detection of reaction runaway as well.It shows that thermal risk assessment plays a key role on process design,and early warning detection system(EWDS) is preferable on prevention of reaction runaway.In the end,perspectives regarding inherently safer designs with the measures discussed above have been provided.