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Gaseous Diffusion Coefficient Apparatus Didactic Equipment Vocational Training Equipment Chemical Engineering

Item No.: CERa-MKII
Gaseous Diffusion Coefficient Apparatus Didactic Equipment Vocational Training Equipment Chemical Engineering
Description
CERa-MKII Gaseous Diffusion Coefficient Apparatus Didactic Equipment Vocational Training Equipment Chemical Engineering

DESCRIPTION
CERa-MKII apparatus for investigation of mass transfer and gaseous diffusion has traditionally used a capillary tube in a hot water bath, with a travelling microscope used to measure the rate of diffusion over a period of time. Although capable of giving good results, this type of apparatus was not without its disadvantages, particularly ease of use.
 have yet again introduced a radical alternative to the traditional methods, utilising the benefits of modern computer compatible microscopy, producing a novel system with a large number of benefits.
A small quantity of the volatile liquid to be investigated is placed in a capillary tube, which is positioned in a heated metal block. The block is heated by an electric cartridge heater and kept at a constant temperature using an electronic control loop.
A stream of air is passed across the top of the capillary tube, with a stationary layer of air above the liquid surface, creating a partial pressure difference between the liquid surface and the flowing air stream. As vapour diffuses from the liquid into the air stream, the amount of liquid in the tube reduces and the phase boundary between the liquid and the air drops. Measurement of how this phase boundary changes with time enables the molar mass transfer rate to be determined.
A slot in the heater block enables the phase boundary to be observed using a high definition microscope. This microscope produces high definition images onto a standard windows computer (not supplied). The software provided with this microscope includes highly accurate measurement and an automated time lapse facility (either as video or multiple still images).


TECHNICAL SPECIFICATIONS
A self-contained bench mounted apparatus for the determination of diffusion coefficients of a vapour in air
The apparatus blows air across the top of the capillary tube, inside diameter 2mm
The tube is contained in a heated aluminium block with a 25W heater
The temperature control system maintains the block to be better than +/- 1°C from ambient to 60°C.
Operating temperature typically achieved in 20 minutes (40°C operation)
The equipment incorporates a high definition USB microscope with a resolution of 1600 x 1200 and preset to an optical gain of approximately x37
Microscope and heater block containing the capillary are visible to the user and internal illumination of the capillary is provided
Viewing length of the capillary is 12mm
Physical reference scale provided (can be used for software calibration)
Phase boundary measurement resolution < 0.0002mm
Powered by universal power adaptor with worldwide approvals
Software can create individual images under operator control, multiple timed images under automatic control or time lapsed video. Images can be time and date tagged. Time lapse periods can be set from five seconds to many days.
Output formats include .jpg .bmp .avi
EXPERIMENTAL CONTENT
To determine the diffusion coefficient of a gas by evaporation from a liquid surface
Direct measurement of mass transfer rates in the absence of convective effects
Use of gas laws to calculate concentration differences in terms of partial pressures
Use of Fick’s law to measure diffusion coefficients in the presence of a stationary gas
Measurement of the effect of temperature on diffusion coefficients
Investigation into diffusion coefficients of alternative fluids
Gaining familiarity with the use of laboratory instruments to achieve accurate measurements of data required for industrial process design