# Determining head versus flow rate curve.

1. Nov 29, 2005

### 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). Ive 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? Im not really sure what I need to use to get what the question wants.

2. Nov 30, 2005

### 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.