2. In a laboratory experiment, air ( 1.2 kg/m3, = 0.000015 kg/ms) flows from a v

Question

2. In a laboratory experiment, air ( 1.2 kg/m3, = 0.000015 kg/ms) flows from a very large air tank through a 2 cm diameter smooth pipe open to atmosphere as shown. The flow is metered by a long-radius nozzle of 1 cm diameter, using oil (SG = 0.827). The pipe is 8 m long. Following measurements were taken at different flow rates Tank Pressure Page (Pa) Manometer Reading h (mm) Friction factor f Volume Flow rate m3/hr (theory) Volume Flow rate m3/hr (measured) 60 320 1200 2050 24703500 4900 6 38160295 380 575 820 (a) For each data point, compute the volume flow rate (m3/hr) using the energy equation and pipe flow analysis. Assume a smooth pipe. Consider major and minor losses loss coefficients for entrance (Kentrance 0.5) and nozzle (Knozle0.7). Enter friction factor f and volume flow rate values (theory) in the above table. Either use Moody's chart (or the Colebrook relation, this might be better as several data points are given) . Assume minor (b) Compute the volume flow rate (m3/hr) using the measured manometer reading across the nozzle (you will have to first relate the manometer reading and area change across nozzle to the velocity through the nozzle throat and then obtain the flow rate). Enter this value in the above table as well (c) Plot (using Matlab or other software), flow rate versus the flow Reynolds number (Re). Use solid line for the flow rate obtained from the pipe flow analysis and square symbols for the flow rate obtained from the manometer reading. Both should be plotted on the same figure with proper legend given. Show all steps and attach your program or procedure used to solve this part.

Explanation / Answer

So basically there are 5 types of minor losses in a pipe flow.

1. Losses at pipe entrance or exit

2. Losses due to sudden expansion or contraction

3. Losses due to gradual expansion or contraction

4. Losses due to pipe fittings

In the given question, only 1st and 2nd types of losses are occurring.

2nd type of loss occur due to the presence of nozzle which will be compensated by considering K(nozzle)

Also the loss at entrance can be considered by taking K (entrance)

Now the K values for losses at exit are generally taken as 1. This is because when the flow takes place from a pipe to a much larger body of same velocity then its velocity is completely reduced to zero and its kinetic energy is dissipated. Hence the losses are of only one velocity head irrespective of the exit geometry.

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