Specific heat capacity (Cp) is the amount of heat required to raise the temperature of a unit mass by one degree at constant pressure. For MIL-PRF-23699 it is measured in kJ/(kg·K) [SI] or Btu/(lbm·°F) [Imperial], and governs sizing of heat exchangers and thermal management systems. The heat transfer equation is:

Q = ṁ × Cp × ΔT

where Q is heat flow (W or BTU/hr), ṁ is mass flow rate, and ΔT is the temperature difference across the heat exchanger or system boundary.

The heat capacity data was measured by NIST using a differential scanning calorimeter (DSC) at ambient pressure. Data were collected at >1 point per second and reduced to 1-K intervals for tabulation. The expanded uncertainty is approximately ±0.048–0.065 J/(g·K), corresponding to a relative uncertainty of ~2.8–3.0 %. Cp increases nearly linearly with temperature from 1.737 J/(g·K) at 0 °C to 2.343 J/(g·K) at 219 °C.