An investigation of transient three-dimensional buoyancy-driven flow and heat transfer in a closed horizontal annulus
Abstract Buoyancy-driven flow and heat transfer in a horizontal annulus bounded by two impermeable boundaries in the axial direction are numerically investigated in this work. A transient three-dimensional analysis of the end effects on heat transfer and the corresponding flow field is presented. The effects of the axial impermeable boundaries are shown to be characterized by retardation of the flow field through the viscous shearing force in regions near the end walls. The results show that the temperature distribution remains unchanged in the core region provided that the annulus length to outer radius ratio is larger than a critical value. Flow and temperature fields are found to be symmetrical with respect to the mid-axial plane of the annulus. A number of interesting features resulting from the sudden heating of the inner cylinder are presented. Finally, a thorough presentation of formation of flow and temperature fields as a result of the sudden heating of the inner cylinder is given.
A liquid-filled buoyancy-driven convective micromachined accelerometer
A novel class of accelerometer, based on the buoyancy of a heated fluid within a micromachined cavity, has previously been developed and reported. Based on dimensional analysis and computational modeling, it is predicted that the sensitivity of the accelerometer can be increased by several orders of magnitude over previously reported results by choosing a suitable liquid as the working fluid, though this increased sensitivity comes at the cost of an increased response time. A liquid-filled accelerometer is constructed; its sensitivity and response time are measured, and shown to be consistent with theoretical predictions and with the results of finite-element analysis. It is noted that the existing literature provides no basis for predicting the effect of Prandtl number on the sensitivity and response time of the accelerometer. The prediction of response time requires analysis of the transient response of the heated fluid to a sudden acceleration. This is a novel problem: previous studies of transient convection have focused on the effects of a newly imposed temperature differential in an existing gravity field, rather than a newly imposed acceleration on an existing thermal field. An approximate expression for response time as a function of radius ratio and Prandtl number is developed by curve-fitting to the results of FLOTRAN simulation.
The Collected Works of Irving Langmuir
Volume 7—Protein Structures Volume 8—Properties of Matter Volume 9—Surface Phenomena By (General Editor) GUY SUITS Oxford: Pergamon Press Ltd. Volume 7—Pp. xlii + 227 Volume 8—Pp. xxix + 251 Volume 9—Pp. xxi + 521 Price 100s. per volume These three volumes comprise many of Langmuir's papers on surface films and surface phenomena and are to some extent self-contained. However, Langmuir's work in this field was so extensive that, particularly for Vol. 9, reference to related works in Vols. 1 and 3 should be made for a complete review of his experiments on these subjects.