This project is a Heat Conduction Isothermal Calorimeter based on the designs of Dr Lars Wadsö, Sweden.
I added some NaHCO3 with water (exothermic reaction) into the sample vial and the reference vial contained sand at that time.
The following is a plot of the raw calorimeter readings in micro-Volts versus the time in seconds, the plot was created in Python using matplotlib.
I thought I should add the thermal power after conversion as well in milli-Watts,
Calibration Coefficient as well as baseline was calculated using the calibration procedure explained in the previous log.
Next, I'll start calculating the heat of hydration for a cement sample with the help of a PhD student at my University.
U: Calorimeter Output in Volts (V)
P: Thermal Power in Watts (W)
Q: Heat Produced in Joules (J) or J/g
mc: Cement Weight in grams (g)
The duration of the experiment will be 3 days.
Also the calorimeter readings are logged every 5 seconds onto the microSD card.
It's time for calibrating the calorimeter! There are two parameters I'm interested in for the cement hydration process, which are:
I'm busy at college so didn't have the chance to update the log much further.
I created a PCB to plug-in the Teensy 2.0 board and handle external power using a single cell 3.7V LiPo 4000mAh, running the Teensy at 3V instead of 5V will consume less power and give the battery roughly 6-8 days of continuous data logging to the SD card. During the experiment we experienced periodic loss of power so that's why we are adding external power source.
Also, I believe the battery powered device will reduce lots of the noise from the AC adapters.
I'll be adding more photos after I finish etching the board and soldering the components.
The prototype is complete now, I calibrated my sensors with water in the reference vial so this calibration coefficient will work with solution but I will have to re-calibrate it for cement.
The calibration for cement will require filling the reference (inert) vial with Sand or NaCl. Because the specific heat capacity for water is 4182 J/kg while Concrete is 880 J/kg which matches that of Salt and NaCl of 880 J/kg. Sand will be accessible in our Lab, and its specific heat capacity is 830 J/kg.
A PhD student at my faculty is using the device now to perform the heat of hydration of cement experiment over an interval of 7 days. The data is being logged to a micro SD card into a CSV file every 5 seconds (which can be opened via libreOffice Calc or any spreadsheet program).
I'll be adding more specific details about the build and the calibration process.