Using delta wings placed at the leading edge of a flat plate, streamwise vortices are generated that modify the flow; the same wings are also used to modify a developing channel flow. Local and average measurements of convection coefficients are obtained using naphthalene sublimation, and the structure of the vortices is studied using flow visualization and vortex strength measurements. The pressure drop penalty associated with the heat transfer enhancement of the channel flow is also investigated. In regions where a vortex induces a surface-normal inflow, the local heat transfer coefficients are found to increase by as much as 300 percent over the baseline flow, depending on vortex strength and location relative to the boundary layer. Vortex strength increases with Reynolds number, wing aspect ratio, and wing attack angle, and the vortex strength decays as the vortex is carried downstream. Considering the complete channel surface, the largest spatially averaged heat average heat transfer enhancement is 55 percent; it is accompanied by a 100 percent increase in the pressure drop relative to the same channel flow with no delta-wing vortex generator.

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This paper describes the development of a straightforward, entropy-based method for evaluating air-side heat exchanger performance. Using energy conservation, the appropriate rate equations, and the second law of thermodynamics, all energy interactions were cast into their available-work equivalents with heat transfer rate limitations. The proposed method improved on previous techniques in two ways. First, it placed value explicitly on heat duty, recognizing system design constraints and external entropy generation. Second, it accounted for marginal entropy generation due to coupling between the system and the heat exchanger. The effects of the heat exchanger design on the system can cause significant exergy destruction and must be considered by any good performance measure. The proposed methods were applied to the evaluation of a condenser in a vapor-compression system. The condenser example is discussed here in detail, to explore design tradeoffs.

In LNG shipping / offshore offloading, liquid motion within the container sometimes leads to vapor entrapment at the container walls. Dynamic behavior of the entrapped vapor is governed by its thermal or thermodynamic state and profoundly affects LNG sloshing pressure on the container walls. In this paper, the authors will discuss experimental observation of condensable vapor dynamics including steam and natural gas at cryogenic temperatures. Additionally, the authors will also discuss relevant implications in sloshing experiments and the scale up to prototype design.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractMany offshore liquefied natural gas (LNG) import terminal designs have been proposed by industry in the last several years. Most base-load offshore LNG import terminals currently under development utilize either a bottom-founded structure, such as a gravity base or a jacket structure, or a floating structure such as a moored ship-shape hull. In either case, LNG transfer from the LNG carrier (LNGC) to the LNG import terminal is performed through side-by-side offloading.