Measuring Specific Heat Capacity of Paraffin Wax using the TPS Specific Heat Method

Feb 17, 2015Blog, Testing

What is the Specific Heat Capacity of Paraffin Wax?

To find the specific heat capacity of paraffin wax a sample (pictured in TPS Standard Cell) was recently measured multiple times for Specific Heat Capacity (J/kg·K) at 19.5°C using the TPS 2500 S Thermal Conductivity Measurement System and the Transient Plane Source (TPS) Specific Heat Analysis Method.

specific heat capacity of paraffin waxDifferential Scanning Calorimetry (ASTM E1269-11) is a standard method for measuring specific heat capacity and involves heating a small test sample (milligrams) at a controlled heating rate (°C/min) in a controlled atmosphere through the temperature region of interest. The difference in heat flow into the test sample and a reference material or blank due to energy changes in the material is continually monitored and recorded.

By contrast, the TPS Specific Heat Analysis Method has two different sized Specific Heat Cells both offering the capability to measure much larger samples than by DSC. The Standard Cell accommodates test samples up to 19 mm diameter and 5 mm thick and the Large Cell accommodates test samples up to 40 mm diameter and 10 mm thick. The cells are made of a high thermal conductivity material and surrounded by a thermally insulating backing. During measurements, the cell is exposed to a constant output of power that induces heating and the temperature rise is recorded from the resistance increase of the Cell’s sensor. Typical test times would be 40 seconds or longer at the temperature of interest.

How did we measure the Specific Heat Capacity of Paraffin Wax?

During measurements, 200 data points are collected, analyzed and results reported. Larger test samples enable easier preparation and better ensure the bulk sample is represented for measurements. Making measurements for a defined measurement period at the temperature of interest offers the advantage of a more robust measurement of specific heat capacity.

In total, four measurements were made using the TPS Specific Heat Capacity Method to highlight reproducibility of measurements. Mean specific heat capacity results are compared to literature values.

Specific Heat Capacity of  Paraffin Wax at 19.5°C using the TPS 2500 S Thermal Property System

Mean Cp (J/kg·K) Ambient Density (kg/m3) RSD (%) Literature Cp (J/kg·K)* Literature Density (kg/m3)*
2144.1 869.4 1.7 2140-2900 800-900

Notes: Cp is specific heat capacity; RSD is relative standard deviation. Test parameters included a 40 second test time and 0.08 Watts of power supplied to the TPS Specific Heat Cell at a measurement temperature of 19.5°C.

The results from measurements of ambient density and specific heat capacity show good agreement with literature values and the mean results of specific heat capacity had an excellent reproducibility of ± 1.7%.