Isothermal Conduction Calorimeter

Software for JAF Isothermal Conduction Calorimeter

The JAF conduction calorimeter is designed to measure the isothermal heats of hydration of small samples of cements.

The principle on which the calorimeter works is that heat generated during the chemical reaction flows rapidly through a thermal conductor formed by a sensitive thermopile which produces an electrical output proportional to the heat flow through it.

The output signal is monitored by a micro-voltmeter connected to the RS232 serial port of a computer.

The input to the voltmeter is switchable between the two calorimeters which form the basis of the system.

A simple question and answer software package guides the user through the following stages.

Data Collection

• Two scan rates selectable from 0.5minutes upwards e.g.
• scan at 3 - 6minute intervals for the first 48hours where the hydration rate is changing considerably
• scan at 10 - 15minutes from 48hours onwards

Calibration

After the reaction rate returns to a stable level, the calorimeter is calibrated by applying a known voltage to a small heater inside the sample container. This voltage is left on for around 1 hour and readings are taken every 0.5 - 1 minute.

Analysis of Calibration Data

A linear regression analysis is applied to the output signals generated by the calibration. The values obtained from this analysis are then used in the Tian Calvet equation to calculate the calorimeter constants.

Data Analysis

The calorimeter constants are used to convert the output signals from the test run into the rate of heat output in kJ/kg.

The rate of heat output curve is integrated to give the total heat output curve.

Graphical Output

During the test, the output signals from both calorimeters are displayed on the VDU screen.

After the test is complete, the output data for all three generated plots ( rate of heat, total heat and calibration ) are stored as ASCII data in separate files.

These curves can then be plotted using a suitable software package

The software, is written in compiled basic so that it will run on any computer ( 286, 386 or better ) which supports MSDOS.