Establishing a Relationship between Hydraulic Efficiency and Temperature Rise in Centrifugal Pumps: Experimental Study

Hydraulic losses of a low specific speed centrifugal pump originate in the friction and turbulent dissipations in all components between the suction and discharge nozzles as well as fluid recirculation mainly caused by momentum transfer between different parts of fluid zones. The best hydraulic efficiency of centrifugal pumps can reach 85-95% when operating at their designed condition. Shut-off conditions or low flow rates cause the greatest bulk of energy consumption. This study tests 11 distinct centrifugal pumps to calculate disk friction, mechanical losses (ignoring leakage losses due to their very insignificant values for the selected pumps), and hydraulic efficiency after energy balance. Temperature rise of the working fluid is also measured during operation at part load conditions. A theoretically analyzed experimental relation is derived for the temperature difference of suction and discharge. The proposed relation is used to evaluate hydraulic efficiency directly from the temperature rise value and other hydraulic characteristics of the centrifugal pump. The relation accuracy is examined by implementing several centrifugal pumps and it leads to satisfactory results.