Function phase_change_energy 

pub fn phase_change_energy(mass_kg: f64, latent_heat_j_kg: f64) -> f64

Latent heat (J) of a phase change for mass_kg at specific latent heat latent_heat_j_kg — the multi-phase (boiling/condensing/melting) energy term that sits alongside the sensible Q = U·A·ΔT loss.