Pressure Drop over a Bubble Cap Plate.
EXPERIMENT: Pressure drop over a bubble cap plate.
AIM : This experiment is conducted in an experimental test ring in which the effect of the variation in vapor and liquid flow rates on the pressure drop across bubble cap plates is simulated using air and water to represent the vapor and liquid respectively.
THEORY: In a pilot tube the relation between the gas velocity and pressure drop is
Where, is the differential pressure as expressed in the head of the fluid flowing.
Where,
’=level difference
= density of air= 1.21 kg/m3
’=density of liquid (water) =1000 kg/m3
.
Volumetric gas flow rate V (m3/s) is calculated by assuming a flat velocity profile inside the tube. This is justifiable as the flow is turbulent
V= v * s’
Where s’= pipe cross sectional area
Vapor velocity inside the distillation column (v) =
PROCEDURE:
• Allow water to pass through the equipment to ensure the plates are loaded with liquid and then stop the water flow. Wait till the excess water is drained from the plates.
• Set the inclined manometer to a suitable inclination to measure the differential pressure.
• Switch on the blower and measure across the pilot tube, keeping the air flow rate constant. Select the appropriate valves only (one “high” valve and one “low” valve) and measure the pressure drop across the three plates.
• Reuse the air flow rate by partially closing the inlet of the blower and repeat the above procedure to obtain pressure drop at various air i.e. vapor velocities.
• Repeat the above with two different water (i.e. liquid) flow rates which are kept constant.
• Measure the water flow rate by measuring the amount of water collected in a known time interval.
Discussion
A distillation column can use either trays or packing. Their mechanisms of mass transfer differ, but the key for both is a good approach to equilibrium through the generation of large amounts of interfacial area. In a trayed column, liquid flows down the column
AIM : This experiment is conducted in an experimental test ring in which the effect of the variation in vapor and liquid flow rates on the pressure drop across bubble cap plates is simulated using air and water to represent the vapor and liquid respectively.
THEORY: In a pilot tube the relation between the gas velocity and pressure drop is
Where, is the differential pressure as expressed in the head of the fluid flowing.
Where,
’=level difference
= density of air= 1.21 kg/m3
’=density of liquid (water) =1000 kg/m3
.
Volumetric gas flow rate V (m3/s) is calculated by assuming a flat velocity profile inside the tube. This is justifiable as the flow is turbulent
V= v * s’
Where s’= pipe cross sectional area
Vapor velocity inside the distillation column (v) =
PROCEDURE:
• Allow water to pass through the equipment to ensure the plates are loaded with liquid and then stop the water flow. Wait till the excess water is drained from the plates.
• Set the inclined manometer to a suitable inclination to measure the differential pressure.
• Switch on the blower and measure across the pilot tube, keeping the air flow rate constant. Select the appropriate valves only (one “high” valve and one “low” valve) and measure the pressure drop across the three plates.
• Reuse the air flow rate by partially closing the inlet of the blower and repeat the above procedure to obtain pressure drop at various air i.e. vapor velocities.
• Repeat the above with two different water (i.e. liquid) flow rates which are kept constant.
• Measure the water flow rate by measuring the amount of water collected in a known time interval.
Discussion
A distillation column can use either trays or packing. Their mechanisms of mass transfer differ, but the key for both is a good approach to equilibrium through the generation of large amounts of interfacial area. In a trayed column, liquid flows down the column