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The performance of a rotating heat pipe was optimized in terms of the fluid charge ratio, speed of rotation, tapering angle together with relative positions, and the packing ratio of porous filling screens. The favourable effect of porous layers was testified by employing an inner liner along the whole tube interior surface to enhance both evaporation and condensation. The porosity effect was extended to include the whole pipe cross-section such that different configurations of screen layers packed together to form a turbulent extended heat transfer corrugated surface were investigated. It was found that the longitudinal temperature distribution along the heat pipe became more uniform as both the speed of rotation and the tapering angle increased, thus indicating a decrease in the heat pipe thermal resistance. Owing to the fact that enhanced evaporation and condensation take place, the overall heat transfer coefficient increased and the thermal capacity operational limits were extended by increasing the centrifugal acceleration within the stratified flow regime across the speed range of 0—700 r/min. The insertion of porous screens increased the rates of turbulent heat and mass transfer as well as the optimum charge ratio. By optimizing the porous configuration in terms of number of layers and bore size, the decrease in longitudinal temperature difference due to enhanced convection over-rode the increase in saturation temperature difference due to pressure drop. The increased fluid temperature uniformity in the core region, accompanied by severe radial temperature gradients close to the wall, thus revealed increased rates of convective heat transport.

Alkali-activated concrete (AAC) has attained great popularity since finding it as an alternative to Portland cement concrete due to its superior characteristics in terms of mechanical properties and durability, and its low negative environmental impact. This research investigated both experimentally and analytically the bond behavior between alkali-activated slag concrete (AASC) and steel rebars considering some important parameters (rebar diameter and development length-to-diameter ratio) before and after exposure to elevated temperature using beam-end bond testing technique. The obtained experimental results were compared with those obtained from applying the CEB-FIP model and the well-known available equations in the literature. A modified model was proposed for predicting the bond behavior of AASC. Results have showed that the CEB-FIP model provides more conservative values for bond strength compared to the experimentally obtained results which increases the safety level when estimating the bond strength for design purposes. The proposed modified model achieved a higher correlation with the experimental results than the CEB-FIP model at ambient temperature.

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