Displaced enhancement device

Displaced enhancement devices Electro-static fields... 

Displaced enhancement devices are inserted into the flow channel so as to indirectly improve energy transport at the heated surface. They are used with forced flow. 

A rather large variety of tube inserts falls into the category of displaced enhancement devices. The heated surface is left essentially intact, and the fluid flow near the surface is altered by the insert, which might be metallic mesh, static mixer elements, rings, disks, or balls. Laminar heat transfer data for uniform-wall-temperature tubes and uniformly heated tubes are plotted in Figs. 11.26 and 11.27, respectively. The isothermal friction factors are plotted in Fig. 11.28. 

Mesh or spiral brush inserts were used by Megerlin et al. [182] to enhance turbulent heat transfer in short channels subjected to high heat flux. The largest recorded improvements in turbulent heat transfer coefficients were obtained—up to 8.5 times however, the pressure drop was up to 2800 times larger. In general, it appears that these displaced enhancement devices are useful in very few practical turbulent situations, for reasons of pressure drop, plugging or fouling, and structural considerations. 

Uchida, M., Xu, C., GuiUy, M.L. and Taya, M. (2002) Design ofNqfion actuator with enhanced displacement. Proceedings of SPIE 4695, Smart structures and materials 2002 electroactive polymer actuators and devices (EAPAD), 57-66. 

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