Armfield Instruction Manual
164
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.
Select ‘Configure...’ from the Sample menu. Set data logging to Automatic at 30
second intervals with Continuous duration.
Check that the temperature readings T1, T2 and T3 are giving sensible values
(usually between 5 and 30 degrees Celsius depending on mains water temperature).
Process fluid flow rate
The temperature of fluid exiting the vessel is controlled by controlling the flow rate of
the fluid through a coil, which is immersed in a heated water bath, and hence the
time available for heat transfer between the water bath and the process fluid.
The heater may be controlled using time proportional control to maintain a constant
bath temperature.
Select the Heater Control button beneath the small process vessel on the software
screen.
Check that the Proportional Band, Integral Time and Derivative Time are all set to 0.
Set a Set Point value of 30°C and a cycle time of 60 seconds. If the mains water
temperature is close to 30°C then a higher Set Point should be chosen- at least 10
degrees higher than mains water temperature is recommended.
Set the Mode of Operation to Automatic control. The controller is now configured as a
time proportional controller.
Apply and close the window.
Open valve SOL 1 by clicking on the SOL 1 switch in the software.
Select the Pump Control button situated above the Pump spin box on the software
screen.
Set the controller to Manual control, and in the Manual Output box set a constant flow
rate for water through the coil of 30%.
Apply the settings but do not close the controller window.
Allow time for the water bath in the process vessel to come up to temperature and
stabilise (temperature T1).
Select the
icon to begin data logging.
Using the Manual Output setting, adjust the flow rate to reach and maintain an exit
temperature T3 of 30°C (choose a higher value if the mains water temperature is
close to 30°C).
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