  We present a method that derives the dust temperatures and infrared (IR)
luminosities of high-redshift galaxies assuming radiation equilibrium in a
simple dust and stellar distribution geometry. Using public data from the
Atacama Large Millimeter/submillimeter Array (ALMA) archive, we studied dust
temperatures assuming a clumpy interstellar medium (ISM) model for
high-redshift galaxies, then tested the consistency of our results with those
obtained using other methods. We find that a dust distribution model assuming a
clumpiness of ${\rm log}\,\xi_{\rm clp}=-1.02\pm0.41$ may accurately represent
the ISM of high-redshift star-forming galaxies. By assuming a value of
$\xi_{\rm{clp}}$, our method enables the derivation of dust temperatures and IR
luminosities of high-redshift galaxies from dust continuum fluxes and emission
sizes obtained from single-band ALMA observations. to demonstrate the method
proposed herein, we determined the dust temperature ($T_{\rm
d}=95^{+13}_{-17}\,\rm{K}$) of a $z\sim8.3$ star-forming galaxy, MACS0416-Y1.
Because the method only requires a single-band dust observation to derive a
dust temperature, it is more easily accessible than multi-band observations or
high-redshift emission line searches and can be applied to large samples of
galaxies in future studies using high resolution interferometers such as ALMA.
