  We modify and extend a recently proposed four-wave mixing scheme [Opt.
Express 25 (19),23164 (2017)] for achieving near-field thermal upconversion and
energy transfer, to demonstrate efficient thermal refrigeration at low
intensities $\sim 10^{-9}$W/m$^2$ over a wide range of gap sizes (from tens to
hundreds of nanometers) and operational temperatures (from tens to hundreds of
Kelvins). We further exploit the scheme to achieve magnitude and directional
tunability of near-field heat exchange between bodies held at different
temperatures.
