A high pressure reactor calorimeter has been developed to study chemical reactions in supercritical fluids. Non-dimensional analysis of the heat transfer mechanism in the calorimeter verifies the application of the Nusselt correlation in scCO(2). The reactor's cover and flange have been modified to be fully temperature controlled and their contribution to the dynamic response of the calorimeter is investigated. Finally, the esterification of methanol with acetic anhydride was chosen as a model reaction and the role of heat transfer in chemical reactions in supercritical fluids is discussed. (c) 2006 Elsevier B.V. All rights reserved.