Discussion on pump energy savings

A central air conditioning system generally consists of a refrigeration compressor system, a refrigerant (cooling and heating) circulation water system, a cooling circulation water system, a coil fan system, a cooling tower fan system, and so on. The refrigeration compressor unit compresses the refrigerant (such as R134a, R22, and other cooling media) into a liquid state using a compressor, and then sends this liquid to the evaporator. The chiller water circulation system uses a chiller pump to deliver water at normal temperature into the evaporator coils, where it undergoes indirect heat exchange with the refrigerant; as a result, the water at normal temperature turns into chilled water. This chilled water is sent to the cooling coils located at the inlets of various fans, where it absorbs heat from the air surrounding those coils. The cooled air is then blown into various rooms by the coil fans, thereby achieving the purpose of cooling. After being fully compressed in the evaporator and undergoing the heat absorption process, the refrigerant is then sent to the condenser to return to normal pressure, so that it can release heat there; this heat is carried away by the cooling water of the circulating cooling water system. The cooling circulating water system pumps tap water into the heat exchange coils of the condenser using a cooling water pump, and then sends this heated cooling water to the cooling tower. There, it is cooled naturally or through forced air cooling via fans in the cooling tower, allowing for thorough heat exchange with the atmosphere so that the cooling water returns to normal temperature and can be reused. During winter when heating is required, the central air conditioning system only needs to use hot and cold water pumps (referred to as chiller pumps in summer) to pump water at normal temperature into the coils of the steam heat exchanger. After thorough heat exchange with steam, the hot water is then sent to the fan-coil units on each floor, thereby providing heated air for the users. Our company’s water supply plant has 3 circulating water cooling towers, numbered 1#, 2#, and 3#. The recycled hot water returned from various production units is pumped into these towers, where the packing inside the towers increases the contact area and time between the hot water and air, thereby facilitating heat exchange between them and cooling the circulating water. Thereby obtaining cold water with a circulating water temperature of ≤32°C required by various production units. As the ambient temperature rises, the axial flow fans in the cooling tower are activated to enable forced ventilation, thereby accelerating the heat exchange between the vapor and liquid phases of the circulating water on the filler in the cooling tower. Each cooling tower is equipped with an axial flow fan with a diameter of 8500 mm, driven by a 4-pole asynchronous motor operating at 380 V with a rated power of 160 kW. A reducer with a constant reduction ratio is used for direct connection between the motor and the fan, and no throttle valve is installed inside the tower. Therefore, the speed and air volume of the axial flow fan are not adjustable. The total processing capacity of the 3 towers is 8,000 m3/h, which is far greater than the combined maximum demand of all production units, which is 6,600 m3/h