Experiments were carried out to investigate the heat storage and heat transfer behavior of supercritical air flowing through a rock bed with the working temperature and pressure ranging up to 120 degrees C and 6.55 MPa, respectively. The particle-to-fluid heat transfer coefficients were determined at low Reynolds numbers of 55-125, and the effects of the air pressure, mass flow rate and the entrance distances on the heat transfer coefficient were studied. The results indicate that the radial temperature profile and the entrance effect would be decreased at high pressure, and the experimental heat transfer coefficients at both pressures fit well with Chandra's correlation and Yang's equation of non-uniform spherical particles. (C) 2014 Elsevier Ltd. All rights reserved.