🔍 Key Concepts

• centrifugal pump affinity laws for changes in impeller diameter at constant speed • how flow (capacity), head, and power/brake horsepower each change with impeller diameter • difference between efficiency and geometric scaling of the impeller

💭 Think About

• First recall how pump capacity (flow) changes when you increase the impeller diameter while keeping speed constant. Then recall how head changes. From those patterns, what is the usual pattern for power? • Think about whether brake horsepower is more closely tied to the size (geometry) of the impeller or to its efficiency. Which of the options follows the same kind of power relationship you see in the pump laws? • If you double the impeller diameter and nothing else changes, how many times larger would the brake horsepower be under the pump affinity laws? Which option’s relationship matches that behavior?

✅ Before You Answer

• Make sure you are thinking about change in impeller diameter at constant speed, not change in speed. • Verify the standard pump relationships: Q vs D, H vs D, and then P (or BHP) vs D. • Confirm that efficiency typically does NOT change in direct proportion to impeller diameter for large changes; it follows its own curve.