Simplified minimum volume calculation:

Minimum volume = (minimum heat output × minimum compressor on time) ÷ (specific heat × target DT)

Above example: ({{ minimum_heat_output }}W × {{ minimum_on_time_min*60 }}s) ÷ (4187 J/kg.K × 5K) = {{ suggested_volume | toFixed(0) }} Litres

Target DT range is typically 5-10K

Think of this as the volume required to provide the compressor with the minimum on time under a zero load (no emitter output) condition assuming the volume increases in temperature by the target DT given.