1. Interpretation of Efficiency Indicators

• Definition and Calculation Method of Pump Efficiency: Pump efficiency refers to the ratio of the effective power of the pump to the shaft power. It is an important indicator to measure the performance of the pump, reflecting the effective utilization degree of the pump in the energy conversion process. Effective power is the power obtained by the pump in actually delivering liquid, and the calculation formula is Ne=ρgQH/1000(where ρ is the density of the liquid, in kg/m³; g is the acceleration due to gravity, usually taken as 9.81m/s²; Q is the flow rate of the pump, in m³/s; H is the head of the pump, in m). Shaft power is the power transmitted from the prime mover to the pump shaft. The calculation formula is η=(Ne/N)×100%(where η is the pump efficiency, Ne is the effective power, and N is the shaft power).

• Efficiency Performance of Different Types of Food - Grade Pumps Under Different Working Conditions: Different types of food - grade pumps have different efficiency performances under different working conditions. Centrifugal food - grade pumps have high efficiency under design conditions, usually reaching 70% - 85%, but when deviating from the design flow rate and head, the efficiency will decrease significantly. Positive displacement food - grade pumps such as gear pumps have relatively high efficiency under the working conditions of small flow rate and high head, generally 60% - 75%, and the efficiency curve is relatively flat, with little change in efficiency within a certain flow range. However, food - grade pumps driven by DC brushless motors, due to their advanced control technology, can maintain high efficiency in a wide range of working conditions, especially in partial load conditions, which can effectively reduce energy waste. For example, in household appliances such as juicers, the flow demand will change with the juicing process, and DC brushless food - grade pumps can adjust the speed according to actual needs, always maintaining high operating efficiency.

2. Selection of Energy - Saving Pumps and Long - Term Operating Costs

• Technical Characteristics of High - Efficiency and Energy - Saving Pumps (e.g., DC Brushless Motor Drive): Food - grade pumps driven by DC brushless motors have many energy - saving technical characteristics. The DC brushless motor itself has high efficiency, and compared with traditional brushed motors, the energy conversion loss is smaller. It adopts electronic commutation, avoiding mechanical friction between the brush and the commutator, thus reducing energy loss. At the same time, the DC brushless motor can realize stepless speed regulation through precise electronic control, and can flexibly adjust the speed according to actual working needs (such as the flow and head requirements of different household appliances in different working stages), so that the pump always operates in the efficient range, greatly reducing energy consumption. In addition, such pumps often adopt optimized hydraulic design to reduce energy loss of water flow in the pump, further improving the overall efficiency.

• Analysis of the Significance of Energy - Saving Pumps in Reducing Costs from a Long - Term Operation Perspective: Although the initial purchase cost of energy - saving food - grade pumps may be higher than that of ordinary pumps, in the long run, they can significantly reduce costs. Take a food - grade pump used in a dishwasher as an example. It is assumed that the power of an ordinary pump is 1.5kW, the power of an energy - saving pump is 1.0kW, it runs for 8 hours a day, 300 days a year, and the electricity fee is 0.8 yuan per kWh. The annual electricity fee for the ordinary pump is 1.5×8×300×0.8 = 2880 yuan, and the annual electricity fee for the energy - saving pump is 1.0×8×300×0.8 = 1920 yuan, saving 960 yuan in electricity fees per year. If the service life of the equipment is 5 years, only the electricity fee can save 4800 yuan, which is far more than the difference in the initial purchase cost. At the same time, energy - saving pumps usually run more stably and generate less heat, which can reduce the downtime loss and maintenance cost caused by equipment failure, extend the overall service life of the equipment, and reduce the long - term operating cost for enterprises in many aspects.