Distributed Pumping Chilled Water Hydronic System for Air-conditioning Systems

摘要

The most prevalent systems used in commercial chilled water pumping systems are Primary only, Primary-Secondary and Primary-Secondary-Tertiary systems. Pumping energy accounts for about 20% to 30% of the total chilled water plant energy. Code requirements in Singapore necessitate a pump power limitation for chilled water pumps of 349 kW/m~3/s (SS553,2016). Similar pumping power limitation requirements can be found in ASHRAE 90.1 2016. Newer system designs are required to meet or exceed this pump power limitation in order to improve the overall chiller plant efficiency. This has increased the necessity to revisit some pumping strategies that have not been traditionally used for systems with standard sizes. Coil pumping strategy is known to be the best solution for systems serving large air handling units (Taylor, July 2011). A Primary-Coil Secondary (P-CS) system is also introduced in the past (EDR, 2009) which uses a coil pump at the AHU's and primary pump in the chiller plant. Recent improvement in efficiency of low flow high head pumps with variable speed drives have made using a P-CS type configuration more economical viable. This article provides the results of application of a Primary-Coil Secondary pumping system to a small commercial building.