Advancements In Hydraulic Modeling of Cooling Water Intakes in Power Plants

Satisfactory hydraulic performance of pump intakes is very important to avoid flow conditions that would adversely affect the performance of cooling water and service water pumps in power plants. Hydraulic performance is best evaluated using physical hydraulic models. Typically, a hydraulic model is used to identify formation of any objectionable free surface and subsurface vortices, presence of any high swirl or pre-rotation and/or non-uniform axial velocity distribution at the impeller entrance. A model study would evaluate an initial design based on an acceptance criteria and derive remedial modifications as needed to meet the acceptance criteria. Over the past several years, modeling of pump intakes has evolved in terms of criteria for model scale selection, instrumentation accuracy and computerized data acquisition techniques, the use of computational fluid dynamics (CFD) to evaluate detailed approach flow patterns and the availability of Hydraulic Institute Standards (HIS) for acceptance criteria to evaluate hydraulic performance. Also, hydraulic model studies conducted by various laboratories over many years have contributed to the advancement of the knowledge about vortex formation, swirl and scale effects in models. To the benefit of all, these advancements have resulted in higher confidence in models with more efficient execution of the model studies at minimal costs. The purpose of this paper is to present advancements that have been made in the field of hydraulic modeling of pump intakes. Examples are provided to show how hydraulic models may be used to first identify unacceptable flow conditions and then to derive modifications to improve the hydraulic performance for both circulating water and cooling water pump intakes.