FLOW FIELD NEAR AN OCEAN THERMAL ENERGY CONVERSION PLANT

D.M. Sheppard, G.M. Powell, I.B. Chou

Abstract


The flow field in the vicinity of an Ocean Thermal Energy Conversion (OTEC) Plant is extremely complex. The plants will normally be located in an area of relatively high surface currents and the location must also be such that a large temperature difference exists between the lower layers and the surface. Locations that demonstrate this characteristic can in many cases be modeled as a two layer fluid as shown in Figure 1. A number of different designs for the OTEC plants are being considered, but they all have one thing in common, a large vertical cold water pipe. This pipe extends from near the surface to some point in the cold water layer (see Figure 1). In some designs this pipe is as large as 40 m in diameter and 460 m in length. Having such a large object penetrating the interface between the two temperature layers in the presence of a shear flow can significantly alter the character of the interface. The highly turbulent wake downstream from the pipe can drastically effect the mixing across this density interface. A conventional heat engine cycle is used in the plant with the high temperature source being the water in the upper layers and the low temperature reservoir being the water from the lower depths. \ Since the temperature difference is small for this type of plant (20° max.), vast quantities of both high and low temperature water must be used. The intake and discharge for the warm water as well as the cold water discharge will be in the upper layer; the intake for the cold water will be in the lower layer at or near the end of the cold water pipe. The flow problem is thus one of a vertical cylinder in a two layer stratified shear flow with sources and sinks located along the cylinder.

Keywords


flow field; thermal energy; energy conversion plant; ocean energey

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