Experiment study on condensation heat transfer and pressure drop of steam flow inside rectangular tube with different aspect ratio

In this study, the condensation heat transfer coefficient and pressure drop of steam are obtained in small rectangular tubes with different aspect ratios. The experiments were carried out on three rectangular tubes with aspect ratios of 1:2, 1:3 and 1:5, with mass flux between 25 and 45 kg/m2s, and vapor qualities between 0.1 and 0.8. The experimental data were analyzed to determine the effect of vapor quality, mass flux, and aspect ratio on the heat transfer coefficient and pressure drop. The results showed that the effect of aspect ratio on condensation heat transfer coefficient appears to be dependent on the flow pattern. For stratified flow, the condensation heat transfer coefficient increases as the mass flux increases. For annular flow, the condensation heat transfer coefficient hardly changed. The pressure drop always increases as the aspect ratio increases. Previous studies on round tube heat transfer and pressure drop correlations have not successfully predicted the small rectangular tube data; therefore, modified Shah correlation and Lockhart & Martinelli correlation are proposed, which predict the data with 20% and 23% RMS error, respectively.

Effect of Exposure Temperature on the Crashworthiness of Carbon/Epoxy Composite Rectangular Tubes Under Quasi-Static Compression

The exposure of polymeric composites to thermal loading is a ubiquitous problem that leads to the degradation of mechanical properties, reducing the service life of an engineered structure, and potentially premature, catastrophic modes of failure. In the current paper, an experimental study is presented in order to investigate the effect of thermal exposure on the crushing performance of carbon fiber-reinforced plastic (CFRP) composite tubes. Specimens of rectangular tubes are subjected to thermal exposure at 90, 120, 150 and 180 °C before being crushed under quasi-static loading. The results showed a reduction in the peak load by increasing the aging temperature up to °C, which is followed by an increase in the peak load at 150 °C, due to post-curing. For the energy absorbed and the specific energy, a sharp reduction is recorded (up to 70% reduction) due to thermal aging. These results showed that the effect of thermal exposure on crashworthiness needs more attention during composites’ design, especially for transportation applications.

Closed knight’s tour problem on some (m,n,k,1)-rectangular tubes

A closed knight’s tour of a normal two-dimensional chessboard by using legal moves of the knight has been generalized in several ways. One way is to consider a closed knight’s tour on a ringboard of width [Formula: see text], which is the [Formula: see text] chessboard with the middle part missing and the rim contains [Formula: see text] rows and [Formula: see text] columns. Another way is to stack [Formula: see text] copies of the [Formula: see text] chessboard to construct an [Formula: see text] rectangular chessboard and the closed knight’s tour can be on the surface or within the [Formula: see text] rectangular chessboard. This paper combines these two ideas by stacking [Formula: see text] copies of [Formula: see text] ringboard of width [Formula: see text], which we call the [Formula: see text]-rectangular tube. We explore the existence and the nonexistence of closed knight’s tours for [Formula: see text]-tube and [Formula: see text]-tube.