1、已知总风量Q=37000m3/h,计算直径(Dn)120mm支管道吸风量Qn(m3/h):
37000/37
=1000
2、计算支管道风速(m/s):
V=Qn/{(Dn/2)^2π3600}
=1000/{(120/1000/2)^2×3.14×3600}
=24.57
3、计算主管道直径D(m):
D=√{4Q/(Vπ3600)}
=√{4×37000/(24.57×3.14×3600)}
=0.729
4、为了确保每个120mm直径吸口吸风量相等,并且简化制造工艺,减少制造成本,为了生产方便,先在主管道D上安装120mm直径支管道7个,其余:37-7=30个支管分成每6个支管吸口为一组,变一次主管道直径Da(m),共分为30/6=5段。计算由主管道D之后的第一次变径:
Qa=Q-7Qn
=37000-7×1000
=30000
Da=√{4Qa/(Vπ3600)}
=√{4×30000/(24.57×3.14×3600)}
=0.657
5、计算第二次变径Db(m):
Qb=Q-(7+6)Qn
=37000-(7+6)×1000
=24000
Db=√{4Qb/(Vπ3600)}
=√{4×24000/(24.57×3.14×3600)}
=0.587
6、计算第三次变径Dc(m):
Qc=Q-(7+6+6)Qn
=37000-(7+6+6)×1000
=18000
Dc=√{4Qc/(Vπ3600)}
=√{4×18000/(24.57×3.14×3600)}
=0.509
7、计算第四次变径Dd(m):
Qd=Q-(7+6+6+6)Qn
=37000-(7+6+6+6)×1000
=12000
Dd=√{4Qd/(Vπ3600)}
=√{4×12000/(24.57×3.14×3600)}
=0.415
8、计算第五次变径De(m):
Qe=Q-(7+6+6+6+6)Qn
=37000-(7+6+6+6+6)×1000
=6000
De=√{4Qe/(Vπ3600)}
=√{4×6000/(24.57×3.14×3600)}
=0.293
9、计算每米主管道摩擦阻力R(Pa):(这里按平均主管道直径计算)
R=(λ/(D+De)/2)/{(D+De)/2}(V^2γ/2)
=(0.0125+0.0011/(0.729+0.293)/2)/{(0.729+0.293)/2}×(24.57^2×1.2/2)
=
追问我看不懂那些符号!