The paper addresses itself to the massive pumping requirements of the projected 100 MW OTEC Plants and objectively examines the current availability of pumping technology to fulfill the requirements.
Presents the findings of a comprehensive study on the optimum size and design of the pumps that will be required and the industry experience and projected reliability of the equipment.
Will also present current industry and government programs underway to improve the operating efficiency of the pumping equipment which, of course, is the single most major power consumer in the entire plant and the projected results of this development work.
Conclusions reached are that although the requirements are massive, the industry does possess the demonstrated technology to reliably respond to the OTEC requirements and that current developments are geared towards efficiency improvement and not any required technological breakthroughs.
Regardless of the ultimate conditions of service which may be specified for OTEC seawater pumps in operating power plants, it can be assured that these pumps will be of the axial flow type. This conclusion is inevitable in view of the tremendous volumes of water which must be handled, and the fact that unless the head is kept to a low value, the power required to drive the pumps could become such a large fraction of the plant's gross output as to render the whole project uneconomic.
In pump designer's parlance, axial flow pumps are identified with high specific speeds and vice-versa. Specific speed, Ns, is a characteristic number which relates RPM, capacity, and total head as follows:
(Available in full paper)
From this equation it is apparent that when the capacity (GPM) is very large and the head (H) is very low, Ns will tend to be high. Its actual value is also obviously dependent on the pump's operating speed (RPM), which is of paramount importance since it is inversely proportional to pump size, and hence to pump cost.
This being the case, the first, and most important, problem confronted in pump design is to determine how high to push the specific speed. If it is too low the pump becomes too large and too costly; if it is too high we know from experience that the pump efficiency will deteriorate, and that operating costs over the pump's lifetime will be excessive. In other words, the economic success or failure of the design hangs almost entirely on the selection of this value.
Past experience in the design and manufacture of large axial flow pumps has established that the maximum specific speed for which peak efficiencies can be achieved is approximately 10,000 (units for capacity and head are USGPM and feet, respectively), and all of the pump designs discussed herein are based on a value very close to this, namely 10,250.
