Determining head versus flow rate curve.

[mpm]

I'm doing a lab on Laminar Flow Elements - Fan Performance Test.

So far I have had to find power coefficients (CP), discharge coefficient (CQ) and head coefficients (CH). I've plotted CH vs. CQ, CP vs. CQ and Efficiency vs. CQ.

My last requirement is that I "Use the curve fits to calculate the head versus flow rate curve under STP conditions at 3000 rpm".

I have no clue what this is asking or where to start.

Can anyone help me on this? I am not really sure what I need to use to get what the question wants.

 

[FredGarvin]

It might help if you tell us what steps you took in this lab. Did you have a portion where you kept the fan speed constant and varried a downstream restriction and measure pressure and flow?

To correlate a given temperature and pressure condition to standard conditions you do two things:

1) State what you are calling standard conditions. There are different definitions out there for STP. Your definition may not be the same as someone elses.

2) Use the following to correct to standard conditions. Here I am using 14.7 psia and 70°F as STP:

$$\rho_2 = \rho_1 *\frac{T_1}{T_2} \frac{P_2}{P_1}$$
This form will convert any density to a specific temperature (in °R) and pressure (absolute) to another temperature and pressure.

 

[piercas]

I can provide some guidance on how to approach this task. First, it is important to understand the concepts of head and flow rate in relation to laminar flow elements. Head refers to the pressure difference between the inlet and outlet of the element, while flow rate is the volume of fluid passing through the element per unit time. These two parameters are related to the performance of the fan and can be measured experimentally.

To determine the head versus flow rate curve, you will need to use the data you have collected for the power, discharge, and head coefficients. These coefficients are related to the head and flow rate through mathematical equations, which can be used to create a curve.

To start, plot the data you have collected for CP, CQ, and CH on a graph. This will give you three separate curves. Next, use a curve fitting tool or software to fit a curve to each of these plots. This will give you equations that relate each coefficient to the flow rate.

Once you have these equations, you can use them to calculate the head versus flow rate curve under standard temperature and pressure (STP) conditions. This means that you will need to convert your data to STP conditions, which can be done using the ideal gas law.

Finally, plot the calculated head versus flow rate curve on the same graph as your experimental data. This will allow you to compare the two and see how well your experimental data fits the curve.

In conclusion, determining the head versus flow rate curve for laminar flow elements requires a thorough understanding of the related coefficients and the use of curve fitting techniques. By following these steps, you should be able to complete this task successfully.