Optimal Design Of Secondary Water Supply System Based On Water Consumption Pattern In An Office Building

Nowadays, as a growing number of high-rise offices burst upon the sight, theenergy consumption of secondary water supply system is gaining speed. How tomaximize the energy-saving system while maintaining the requirement of waterquality, water quantity and water pressure has became a new target of design.Inaccuracy of current design parameters of water supply system in officebuilding as well as insufficiency of design basis maintains one of reasons of highenergy consumption. The paper aims to provide data support for existing norms andtechnical support for energy conservation and optimization in secondary water supplysystem by targeting at an existing high-rise office building and respectivelymonitoring the variation regularity of water amount in real time in drinking watersystem and reclaimed water system. By comparing the two systems’ parametersmonitored in this research with the specified value, it is found that water consumptionper day per person of these two systems are over2times higher than the standardvalues of norms. And the hourly variation coefficients of these two systems are1.87and2.12, which are more than1.2times higher than the standard values. Moreover,the peak flow in real measure of DWS is only0.6time as much as theoretical value,while the RWS’s consumption is1.8times as much as theoretical value. Mass flow ofhigher frequency in2systems lie in0to5m3/h and0to9m3/h.The maximumfrequency of water consumption lies in average hourly water consumption ofeveryday. These conclusions provide basis for code revision.Another critical reason for the waste of energy in secondary water supply systemlies in the mismatch between the design and operation of the pumps and the law ofwater consumption. According to the research, the similarities of water consumptionlaw between DWS and RWS are as follows. Firstly, people in the office usually don’tuse water during off-hours. Secondly, people use less water in the non-working days.Thirdly, monthly water consumption increases as the temperature rises. Thedifferences between the two lie in2points. Firstly, the water consumption of RWS ismore than that of DWS, and varies within wide limits. Secondly, the waterconsumption of DWS is apt to get influenced by air conditioning system andtemperature.To meet the maximum flow requirements, and make sure all the pumps workefficiently, a small-power pump is added to each of these two systems. Based on thehourly variation of flow, different types of variable frequency pumps operate alternatively combined with small pressure vessel. When the flow is small, thesmall-power pump is turned on, and switched to a larger pump with larger waterconsumption, avoiding pumps work inefficiently. Energy saving rates of DWS andRWS is as high as31.3%and17.6%respectively. This paper will provide referencematerials for not only designing and operating of water supply system of officebuildings, but also the design of pumping stations.