Calculation and parameter specification selection of pipeline quality water supply system (2)

10.
4.
2.
3 Pipeline flow velocity and pipe diameter

When the pipe diameter DN≥32mm, the flow velocity w=1.
0～1.
5m/s; when the pipe diameter DN<32mm, the flow velocity v=0.
6～1.
0m/s
.

The pipe diameter can be calculated according to the following formula:

In the formula, D is the pipe diameter, m; Q is the design flow rate of the pipe section, m ³ /s; v is the water flow velocity of the pipe, m/s
.

In the calculation of the direct drinking water system, since the designed second flow rate is an empirical value, the following empirical values ​​can also be used directly for the pipe diameter
.

(1) The diameter of the riser pipe can be constant
.

(2) The water distribution horizontal trunk pipe of the vertical pipe in the ring pipe network, the pipe diameter can be constant, and the maximum value of the following two data is taken:

①One size smaller than the water mains;

②According to 2/3 of the total number of faucets, calculate the instantaneous peak flow and select the pipe diameter
.

(3) The diameter of the horizontal trunk pipe connected to the end of the riser can be constant.
The diameter of the pipe shall be the maximum of the following two data:

① One size smaller than the water distribution horizontal main pipe;

②One size larger than the riser
.

10.
4.
2.
4 The total number of taps of water supply pipes flowing into the node

The total number of taps borne by the water supply pipes flowing into the node is the sum of the total number of taps borne by the water supply pipes flowing out of the node
.

n _e =np/p _e

In the formula, n _e is the converted number of faucets; p _e is the new calculated probability value

10.

The water production rate Q _j (L/h) of water purification equipment is calculated as follows:

Q _j =Q _d /T

In the formula, T is the highest daily working time of water purification equipment, generally 8-12h

10.

Pump flow rate: Q _b =q _s

Pump head: H _b =h _o +Z+∑h

In the formula, h _o is the free head of the faucet, m; Z is the geometric height difference between the most unfavorable faucet and the storage tank, m; ∑h is the total head loss of the pipeline from the most unfavorable faucet to the storage tank, m

If the circulation of the system is also maintained by the water supply pump, it needs to be checked that the total flow of the system should not be greater than the design flow of the pump in the circulating state