Question

Air flows through pipe. A orifice meter is used to measure the mass flow. The temperature and static pressure of the air are 19.2 °C and 91.5 kPa respectively. The diameter of the pipe is 19 cm and the diameter of the orifice plate is 17.85 cm. Assume the discharge coefficient of the orifice plate as 0.60. A pressure difference of 177 Pa is measured over the orifice plate. Determine the mass flow in the pipe(kg/s)

Answer 1

Explanation:

properties of the orifice and the inherent properties of the fluid are known, the orifice can be used to measure flow rates. Flow measurement by an orifice is based on the application of Bernoulli’s equation, which states that a relationship exists between the pressure of the fluid and its velocity. The flow velocity and discharge calculated based on the Bernoulli’s equation should be corrected to include the effects of energy loss and viscosity. Therefore, for accurate results, the coefficient of velocity (Cv) and the coefficient of discharge (Cd) should be calculated for an orifice. This experiment is being conducted to calibrate the coefficients of the given orifices in the lab.

2. PRACTICAL APPLICATION

Orifices have many applications in engineering practice besides the metering of fluid flow in pipes and reservoirs. Flow entering a culvert or storm drain inlet may act as orifice flow; the bottom outlet of a dam is another example. The coefficients of velocity and discharge are necessary to accurately predict flow rates from orifices.

3. OBJECTIVE

The objective of this lab experiment is to determine the coefficients of velocity and discharge of two small orifices in the lab and compare them with values in textbooks and other reliable sources.

4. METHOD

The coefficients of velocity and discharge are determined by measuring the trajectory of a jet issuing fluid from an orifice in the side of a reservoir under steady flow conditions, i.e., a constant reservoir head.

5. EQUIPMENT

The following equipment is required to perform the orifice and free jet flow experiment:

F1-10 hydraulics bench;

F1-17 orifice and free jet flow apparatus, with two orifices having diameters of 3 and 6 mm;

Measuring cylinder for flow measurement; and

Stopwatch for timing the flow measurement.