  In the conventional picture, the temperature of a liquid bath in the
quiescent state is uniform down to thermal fluctuation length scales. Here we
examine the impact of a low frequency shear mechanical field (Hz) on the
thermal equilibrium of liquids (Polypropylene glycol and pentadecane away from
any phase transition) confined between high energy surfaces. We show the
emergence of both cooling and heating shear waves of several tens microns
widths varying synchronously with the applied shear strain wave. The thermal
wave is stable at low strain amplitude and low frequency while thermal
harmonics develop by slightly increasing the frequency or the strain amplitude.
The liquid layer behaves as a thermoelastic medium. This view is in agreement
with recent theoretical models predicting that liquids support shear elastic
waves up to finite propagation length scale of the order the thermal wave.
