Orifice pressure drop

When the single-phase pressure drops have been predicted and the quality of the flow is known, Eq. (3-161) gives the two-phase orifice pressure drop. 

Equation (10-21) represents the net total (unrecovered) pressure drop due to friction in the orifice. This is expressed as a percentage of the maximum (orifice) pressure drop in Fig. 10-5. 

An orifice meter with a hole of 1 in. diameter is inserted into a l- in. sch 40 line carrying SAE 10 lube oil at 70°F (SG = 0.93). A manometer using water as the manometer fluid is used to measure the orifice pressure drop and reads 8 in. What is the flow rate of the oil, in gpm ... 

The heat flow rate (Q) of a gaseous fuel is calculated as the product of its volumetric flow rate at standard conditions (V0) and its calorific value (CV). The Wobbe index (WI) measures the ratio between the net CV and the square root of specific gravity (SG). With orifice-type flow sensors, the advantage of detecting the WI is that it eliminates the need to separately measure the specific gravity this is because the product of the WI and orifice pressure drop results in a constant times the heat flow rate (KxQ), without requiring a separate measurement of SG. 

On-line analysis of the hydrocarbons in the vent gas was done on a 20-ft Porapak Q column with an internal standard. In many cases, the internal standard also allowed calculation of hydrogen by difference. A Beckman 3AM3 gas density balance provided a check on the vent gas analysis and the necessary parameter for calculating mass flow rates from orifice pressure drop data. Mass balance closure was typically better than it 2%. 

The orifice pressure drop may be calculated using the predicted model of Pilhofer and Goedl (1977). 

Uo = average hole velocity, cm/s Udow = average velocity in downcomer, cm/s Re = orifice Reynolds number, ( = doUopd/fXd) APo = orifice pressure drop, g/cm-s ... 

Therefore, the orifice pressure drop is calculated using equation 14.53. 

INTERNAL PIPE DIAMETER, inch ORIFICE PRESSURE DROP, inch H20 ORIFICE PRESSURE DROP, psi LIQUID DENSITY, lb/ft 3 ... 

DETERMINES WHETHER THE ORIFICE PRESSURE DROP IS PSI OR INCH-H20. 

READ THE ORIFICE PRESSURE DROP IN INCH-H20 AND THE FLUID FLOW RATE IN Ib/s. 

CALCULATE THE ORIFICE PRESSURE DROP IN PSI. CALCULATE THE GAS FLOW RATE IN ft 3/min. 

A technique which involves a so-called open-siphon is attractive in so far as the flow history of the fluid is apparently simple and readily calculated. Fluid is drawn up out of a beaker through an orifice into a low pressure chamber, and forces in the open siphon column are estimated from the orifice pressure drop, with corrections being made for inertia and gravity contributions [Binding et al., 1990]. Although the technique is very simple, the motion in the siphon may not be entirely shear Iree [Matthys, 1988]. 

The relation between the decay ratios and orifice pressure drop coefficients is shown in Fig. 1.27. The reactor becomes more stable when the orifice pressure drop coefficient increases as is also known for BWRs. It can be seen that the thermal-hydraulic stability criterion is satisfied in the Super LWR at full power normal operation for the average power channel. The maximum power channel can be stabilized by applying a proper orifice pressure drop coefficient. The minimum orifice pressure drop coefficient required for thermal-hydraulic stability at full power operation is found to be 6.18 (a pressure drop of 0.0054 MPa). The total core pressure drop at 100% maximum power operation is 0.133 MPa. The required orifice pressure drop is small compared with the total core pressure drop. 

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