System Overview - Agilent Technologies 1100 Series Reference Manual

System Overview

The Concept of Heating and Cooling
The design of this thermostatted column compartment uses column heating
and cooling devices with Peltier elements. The solvent entering the column
compartment is heated up or cooled down to a settable temperature with two
low-volume heat exchangers (3 µl on left side, 6 µl on right side), made of a
short piece of capillary 0.17 mm i.d. leading through a heat exchanger. The
heat exchanger is designed such that it can function simultaneously as an air
heater. The surface of the heat exchanger is shaped such that the area around
the column is kept on similar temperature level as the liquid running through
the column. This is done by thermal convection and radiation between the
heat exchanger fins. With this design it is ensured that the column and the
solvent flowing through it, are almost at the same temperature.
Actual temperature control is accomplished at the heat exchanger. The solvent
cools down or heats up on its transfer from the heating block to the column
inlet. This depends on several factors: flow rate, setpoint temperature,
ambient temperature and column dimensions.
For example, temperature setpoint is 40 °C. The heat-exchanger temperature
is controlled at 40.8 °C and at the column entry there could be 39.8 °C.
The actual temperature displayed on the user interface is always the derived
temperature taken at the heat exchanger, corrected by the offset explained
above.
Default mode: heater actual, column ± offset
NO TE
Corrected mode: heater ± offset, column actual
Any type of heated column compartment brings one important consequence
for column temperature equilibration. Before an equilibrium is reached the
whole mass of column, column packing and solvent volume inside the column
has to be brought to the selected temperature. This depends on several factors:
flow rate, setpoint temperature, ambient temperature and column dimensions.
The higher the flow rate, the faster the column equilibrates (due to
thermostatted mobile phase).
1100 Series TCC Reference Manual
Introduction to the Column Compartment
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