 Flow calorimeter

A flow calorimeter uses a flowing material to carry energy from a measurement region. In a common arrangement, a heated receiver exchanges energy with a coolant stream. Measurements of mass flow rate and inlet/outlet temperatures determine the stream's enthalpy gain, while the vessel and environmental paths are included in the overall balance.^[ref]

For a steady stream with negligible changes in bulk kinetic energy and height,The approximation uses a suitable approximately constant specific heat capacity. An absorber, inlet and outlet thermometers, and a calibrated flow measurement turn this equation into an apparatus rather than just a temperature reading.

For a synthetic example, let $\dot{m}=0.010\mathrm{kg}{\mathrm{s}}^{-1}$ and $c_p=4000\mathrm{J}\mathrm{k}{\mathrm{g}}^{-1}{\mathrm{K}}^{-1}$. A $0.60\mathrm{K}$ rise gives $P_{\mathrm{fluid}}=24\mathrm{W}$. If a 30-watt electrical reference produces this response under matched conditions, the observed response fraction is $0.8$. Under an explicitly tested proportional-response assumption, a later 36-watt fluid reading would correspond to a 45-watt source.

A single calibration point does not establish that assumption at every power. The full balance includes receiver storage and other losses:Warm-up, leakage, thermometer offsets and transport delays can all affect a time-varying measurement. Calorimeter calibration and electrical calorimetry can test the response across a range, with the same thermodynamic system boundary used for calibration and the unknown source.