§ 1065.640 Flow meter calibration calculations.

This section describes the calculations for calibrating various flow meters. After you calibrate a flow meter using these calculations, use the calculations described in § 1065.642 to calculate flow during an emission test. Paragraph (a) of this section first describes how to convert reference flow meter outputs for use in the calibration equations, which are presented on a molar basis. The remaining paragraphs describe the calibration calculations that are specific to certain types of flow meters.

(a) Reference meter conversions. The calibration equations in this section use molar flow rate, n _ref, as a reference quantity. If your reference meter outputs a flow rate in a different quantity, such as standard volume rate,V _stdref, actual volume rate,V _actref, or mass rate, m _ref, convert your reference meter output to a molar flow rate using the following equations, noting that while values for volume rate, mass rate, pressure, temperature, and molar mass may change during an emission test, you should ensure that they are as constant as practical for each individual set point during a flow meter calibration:

Example 1:

V _stdref = 1000.00 ft 3⁄min = 0.471948 m 3⁄sp_std = 29.9213 in Hg @ 32 °F = 101.325 kPa = 101325 Pa = 101325 kg/(m·s ) T_std = 68.0 °F = 293.15 K R = 8.314472 J/(mol·K) = 8.314472 (m ·kg)/(s ·mol·K)

n _ref = 19.619 mol/s

Example 2:

m _ref = 17.2683 kg/min = 287.805 g/s M_mix = 28.7805 g/mol

n _ref = 10.0000 mol/s

(b) PDP calibration calculations. Perform the following steps to calibrate a PDP flow meter:

(1) Calculate PDP volume pumped per revolution, V_rev, for each restrictor position from the mean values determined in § 1065.340 as follows:

Example:

n _ref = 25.096 mol/s R = 8.314472 J/(mol·K) = 8.314472 (m ·kg)/(s ·mol·K) T ~_in = 299.5 K P ~_in = 98.290 kPa = 98290 Pa = 98290 kg/(m·s ) f ~_nPDP = 1205.1 r/min = 20.085 r/s

V_rev = 0.03166 m /r

(2) Calculate a PDP slip correction factor, K_s, for each restrictor position from the mean values determined in § 1065.340 as follows:

Example:

f ~_nPDP = 1205.1 r/min = 20.085 r/s P ~_out = 100.103 kPa P ~_in = 98.290 kPa

K_s = 0.006700 s/r

(3) Perform a least-squares regression of V_rev, versus K_s, by calculating slope, a₁, and intercept, a₀, as described for a floating intercept in § 1065.602.

(4) Repeat the procedure in paragraphs (b)(1) through (3) of this section for every speed that you run your PDP.