The results of extensive scientific research show that sound has an effect on thermal processes in gases. The Ranque and Hartmann-Sprenger effects belong to this class of phenomena. Existing conventional theories cannot explain the heat transfer processes in devices based on these effects. The concept of Pressure Gradient Elastic Waves provides a physical description of heat transfer in these processes. Pressure Gradient Elastic Waves are waves of sound type. These waves arise in compressible fluids (in gases) as a result of the existence of a pressure gradient within the volume of the gas, and in the presence of initial density fluctuations (under the influence of sound). Under these conditions the pressure forces act on micro volumes having density fluctuations along the pressure gradient vector. However the resultant forces act on fluctuations of rarefaction and on fluctuations of compression in opposite directions. The compression front of Pressure Gradient Elastic Wave propagates in the direction of increasing pressure, while the rarefaction front propagates in the opposite direction i.e. in the direction of reducing pressure. Thus these waves carry energy from the low pressure zone to the high pressure zone. This heat transfer manifests itself in the heating of the wall bounding the high pressure zone and in the cooling of the low pressure region. The article presents the results of experiments performed by the author on a short vortex chamber and on Sprenger heat tubes. The maximum possible extent of heating and cooling are estimated. It is shown that conventional theories, previously used to explain the Ranque and Hartmann-Sprenger effects, fundamentally cannot explain the results obtained. (C) 2016 Elsevier Ltd. All rights reserved.