台湾绿色B建筑节水措施英文文献和中文翻译(6)
4。2。 Evaluation of system for recycling rainwater
Initially, the quantity of rainwater collection and usage must be known。 A basic concept of input and output balance enables four parameters to be used to calculate the rainwater use system。 The two inputs are rainwater from collection devices, and supplementary tap water systems, while the outputs are consumption quantity for the user and overflow from storage devices。 Fig。 3 presents this concept。 The location of the design object, for example in Taipei, must be confirmed based on the daily precipitation database, and the meteorological precipitation data for the simulation or assessment are then used in calculating the utilization of the rainwater。 The area of the collection device must next be decided, while the object character of water utilization is used as the condition for simulation and assessment。 Table 3 presents the daily precipitation format of Taipei city, as an example。 The calculation [5] is as follows:
(1) The quantity collected (CRW) is determined from daily precipitation (Rd) and collection area (CA)。CRW(m3)=CA(m2)×Rd(mm/day)*ξ*10-3
(ξdenotes the flow out coefficient, governed by the character of collection location, and this parameter is usually between 0。85 and 0。95 for a typical roof。)
(2) The overflow quantity (OFV) is determined from the collection quantity (CRW), volumes of storage tanks (SV) and quantity remaining in the storage tanks(RSV)。
If CRW+RSV>SV (m3); then
OFV =CRW+RSV-SV。
If CRW+RSV < SV (m3); then OFV=0。
(3) The first remaining quantity in storage tank(RSV )following the above calculation is as follows:
If CRW+RSV > SV; then RSV′=SV;
If CRW+RSV < SV; then RSV′=CRW+RSV
(4) The quantity of water replenished(CW) from the quantity remaining in the storage tank(RSV′)and consumption for user (UW) is determined thus:
If RSV′-UW < 0; then CW = -( RSV′ -UW)。
If RSV′-UW > 0; then CW = 0。
(5) The second remaining quantity in storage tank (RSV) after the above calculation is as follows:
If RSV′-UW < 0; then RSV′′ =0;
If RSV′-UW > 0; then RSV′′ = RSV′–UW。
(6) The second remaining quantity in the storage tank
(RSV′′) is used as the initial data of RSV for the next day’s data that add up all parameters and yearly utilization by looping calculation。
(7) The above calculation can be used to obtain annual rainwater utilization quantity(YRU),annual rainwater collection quantity (YRC) and annual consumption quantity (YTU)。
YRU=∑(UW-CW); YRC=∑CRW; YTU=∑UW:
(8) Rainwater utilization rate (PRU%) and tap water substitution rate (PCW%) can be calculated as follows:
PRU(%) = YRU&pide;YRC×100，
PCW(%) =YRU&pide;YTC×100
The above procedure for calculating rainwater assessment was carried out on a computer program, and the simulation results were rapidly obtained。 Fig。4 illustrates the program’s flowchart。
4。3。 Case study and analysis
Following the above procedure, a primary school building with a rainwater use system is taken as an example for simulation and to verify the assessment results。 This building is located in Taipei city, has a building area of 1260 m and a total floor area of 6960 m ; it is a multi-discipline teaching building。 Roofing is estimated to cover 80% of the building area, and the rainwater collection area covers 1008 m 。Rainwater is used as intermediate water for the restrooms, and the utilization condition is set at 20 m per day, while
the out flow coefficient (Y) is 0。9。 A typical meteorological precipitation in Taipei in 1992 was adopted as a database。 The rainwater storage tank was set to an initial condition before the simulation procedure。 Herein, four tank volumes were considered in the simulations of rainwater utilization—15, 25, 50, 100 m。 The results indicate that increased storage tank volume reduces overflow and increases the utilization of rainwater。 Given a 50 m storage tank, the quantity of rainwater collection closely approaches the utilization quantity of rainwater。 Consequently, this condition obtains a storage tank with a roughly adequate volume。 When the volume of the storage tank is 100 m, the utilization rate is almost 100% and the overflow quantity approaches zero。 Despite this result being favorable with respect to utilization, such a tank may occupy much space and negatively impact building planning。 Consequently, the design concept must balance all these factors。 The building in this case is six floors high, and the roof area is small in comparison to the total floor area。 The water consumption of the water closet per year, but the maximum rainwater approaches 7280 m collection is 2136 m per year。 Thus, significant replenishment from tap water is required。 This result also leads to a conclusion that high-rise buildings use rainwater systems less efficiently than other buildings。 Lower buildings (e。g。 less than three floors) have highly efficient rainwater utilization and thus little need for replenishment of water from the potable water system。