HVAC Pumps Characteristics and Energy Efficiency

Most HVAC systems are designed to handle the maximum potential temperature extremes, keeping the building cool on the hottest days and warm on the coldest days. As a result, the HVAC system only needs to work at full capacity on the ten or so hottest and coldest days of the year. On the other 345 days, the system could be operated at reduced capacity. HVAC pumps are generally designed for peak conditions and the output of these systems is controlled by mechanically constricting the flow with throttling valves. This wastes energy. By using a variable speed drives, chilled water flows can be matched to actual heating and cooling demands. This 5-hour Quick Book course provides the students with a firm understanding of the basic principles that centrifugal pumps operate under. Topics covered include the performance curve, series operation, parallel operation, the affinity laws, friction, specific gravity & viscosity, suction lift, and NPSH. Learning Objective At the conclusion of this course, the student will: 1. Understand the basic types of pumps used in HVAC applications. 2. Understand the key fluid properties such as viscosity, density, temperature, specific weight, concentration and vapor pressure. 3. Understand why pump performance in typically rated feet of head and not pressure. 4. Understand the various head terms such as suction lift, static head, discharge head, friction head, velocity head and pressure head. 5. Understand the laws of affinity and illustrate them with a pump operating under VFD control. 6. Understand the pump curve, system curve, operating point and the best efficiency point for the pump operation. 7. Understand the flat, smooth and drooping characteristic curve for the centrifugal pump and the applications for which it is best suited. 8. Understand the importance of specific speed and their relationship to the shape of impeller (radial, mixed or axial). 9. Understand pump cavitation and its relationship to net positive suction head (NPSH) available and required. 10. Understand the various techniques for flow control including throttling, speed adjustment and multi-pump installation considerations in parallel or series arrangement. 11. Learn by example the method to compute the frictional head through the HVAC chilled water system. 12. Define the pumping system efficiency and the tips to achieve the same.