Hello everyone! Here is the problem: The air removal in a drying room is done via a pipe (length 6 m, diameter 100 mm and surface roughness 0,152mm). The pipe system is composed of a sharp edged entrance and 4 standard 90 degrees turns. The excess pressure in the dryer is 50 Pa. Calculate the flow speed at which the air is removed from the dryer as well as the mass flow rate. The temperature of the air is 37 celcius degrees (density: 1,12kg/m3 dynamic viscosity: 1,9.10-5 kg/ms) The height drop is negligeable and we assume that the dryer is so big that the flow speed in it is 0 m/s How far I've gotten: I thought of using Bernoulli's equation to figure out the speed of the flow, but I think I'm missing some information: p1-p2=(1/2)*rho*(C22-C12) problem is that I have no idea what is c1 or c2 (speeds) is c1 supposed to be the speed of the flow in the dryer (0 m/s)? That's where I went first. Then I asked myself what if I had to use the pressure drop equation delta(p)=(1/2)*rho*C2*(f*(L/d)+sum(K)) The K's (rughness elements) are easy to solve (0,5 for the sharp edge and 0,3 for each of the standard turns) but to solve the friction factor, I need to use the moody chart...but to use it, I need the flow speed for the Reynold's number. So back to square one. That is pretty much how far I've got and I see no solution in sight. I'm pretty sure it can't be too complicated of an answer. Thanks ahead for your help, this problem has been bugging me for a while now. P.S. : excuse my poor English as it is not my native tongue.