Exercise R
129
Procedure
SAFETY NOTE: During this exercise the apparatus may reach temperatures hot
enough to cause burns or scalds. Do not touch the process vessel during the
exercise, or remove the coil or sensors from within the vessel. Allow the apparatus to
cool before draining the water or disconnecting any of the tubes from the process
vessel.
Set the temperature at which the thermostat will operate. The Set Point is set by
rotating the dial on top of the thermostat mounted in the lid of the small process
vessel. The dial is turned until the arrow on the dial points at the required Set Point. A
recommended starting value is 30 degrees Celsius. If the local mains water
temperature is close to 30 °C then a higher value may be used: at least 10 °C greater
than the mains supply is recommended.
Check that the temperature reading T1 is a sensible value (usually between 5 and 30
degrees Celsius depending on mains water temperature).
Set data logging to automatic at intervals of 30 seconds with continuous duration.
Select the
icon to begin data logging.
Note the behaviour of the heating element as the temperature approaches the set
point. It is possible to observe heated water rising from the heating element when the
power is on. The heater also responds audibly when power is switched on or off.
Additionally, the switch for the heater is displayed on the mimic diagram screen
within the software, allowing observation of the heater action.
The change in temperature may be most easily observed using the graph screen in
the software. If the graph does not appear automatically when the graph screen is
selected, select ‘T1’ for the Y axis and ‘Time’ for the x-axis, then plot the graph. New
points will be added as they are logged.
Continue logging for 10 minutes. Select the
icon to finish data logging.
Disturbances
Within the software it is possible to introduce disturbances in the temperature inside
the process vessel by changing the flowrate of water through the vessel:
In the software, select the
icon to create a new results sheet.
Select the
icon to begin data logging.
In the software, increase the PSV setting by 20%. Open the drain valve at the base
of the process vessel enough to balance the flow in and out of the vessel, so that the
fluid level in the vessel remains constant.
Log the temperature for 10 minutes.
Increase the PSV setting by a further 20%, and open the drain valve more to
maintain the fluid level within the vessel.
Continue to log the temperature for another 10 minutes, and then select the
icon
to finish data logging.
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