because the pipes'diameters are the same, and water density can be considered as constant, so the elocity at section A-A u, =2.9m/s 2) volume flow rate of water V=3600A=3600×2×0.12×29=82m/h 12. The water at 20C flows through the horizontal pipe((38x2. 5mm)at 2.5m/s The pipe is onnected with the another horizontal( 53 x3mm )through a conical pipe. As shown in the figure, two vertical glass tubes are inserted in either side of the conical pipe. If the energy loss through sections A and B is 1.5J/kg, try to calculate the distance between the two liquid level of the glass be(in mm)? Draw the relative position of the liquid level in the figure Solution: From section A-A and section B-B, then the Bernoulli equation is p+∑b Z=Z=O ∑ according to the continuity equation for the incompressible fluid, then )2=2.5()2=1.23m/ the pressure difference between the two sections is P8-PA 2.52-1.232 1.5)×1000=8685N/m then PB-PA=868.5/9.798=88.6mmH20 the liquid level's difference between the two pipes is 88.6mm 886 so P8> PA the pipe's liquid level B is higher than the liquid level-A 13. The water at 20C is sent to the top of the scrubber from the reservoir by the centrifugalbecause the pipes’ diameters are the same, and water density can be considered as constant，so the velocity at section A-A u m s A = 2.9 / 2）volume flow rate of water 2 3 3600 3600 0.1 2.9 82 / 4 V Au m h h  = =    = 12. The water at 20℃ flows through the horizontal pipe(Φ382.5mm) at 2.5m/s.The pipe is connected with the another horizontal (Φ533mm)through a conical pipe. As shown in the figure, two vertical glass tubes are inserted in either side of the conical pipe. If the energy loss through sections A and B is 1.5J/kg,try to calculate the distance between the two liquid level of the glass tube(in mm)? Draw the relative position of the liquid level in the figure. Solution：From section A——A’ and section B——B’，then the Bernoulli equation is + + = + + + f AB B B B A A A h u p gZ u p gZ , 2 2 2  2  in the equation  = = = = h J kg u m s Z Z f AB A A B 1.5 / 2.5 / 0 , according to the continuity equation for the incompressible fluid，then 2 2 4 4 u A d A uB d B   = so m s d d u u B A B A ) 1.23 / 47 33 ( ) 2.5( 2 2 = = = the pressure difference between the two sections is ) 2 ( , 2 2 − − − = f AB A B B A h u u p p =（ 2 2 2 1.5) 1000 868.5 / 2 2.5 1.23 −  = N m − then pB − pA =868.5/9.798=88.6mmH2O the liquid level’s difference between the two pipes is 88.6mm。 because pB = 6 + pA 88. so pB  pA the pipe’s liquid level B is higher than the liquid level-A. 13. The water at 20℃ is sent to the top of the scrubber from the reservoir by the centrifugal