  We study the temperature relaxation dynamics of nodal-line semimetals after a
sudden excitation in the presence of acoustic and optical phonon modes. We find
that the nodal line constrains the electron momenta in scattering processes
and, as a result, the temperature relaxation due to acoustic phonons is
exponential as a function of time. However, depending on initial conditions,
other functional forms are possible. In typical pump-probe experiments, the
temperature relaxation is linear due to acoustic phonons with rates that vary
as $\sim n^{1/2}$ with density. The temperature relaxation due to optical
phonons is also linear with rates $\sim n^{-1/2}$ or $\sim n$.
