The Average Catalyst Temperature, Determined using a Magnetic Method Developed in This Laboratory, is Used with the Measured Values of Bulk Fluid Temperature and Conversion to Determine the Interphase Nusselt Number for Heat Transfer for Several Catalytic Reactor Models: Differential, Plug Flow, Axially Dispersed Plug Flow and Plug Flow with Bypassing. the Reynolds Number Dependence of the Interphase Nusselt Number is Determined for Each of These Models by Regression Analysis of Low Conversion Kinetic Data Obtained from a Single Catalyst Bed. the Reynolds Number Range is 0.1 to 1.3. Accounting for Axial Dispersion or Bypassing Yields Somewhat Higher Nusselt Numbers Relative to the Differential Model, Though They Are Still Orders of Magnitude Less Than One. in Addition, It is Not Apparent from the Results that the Nusselt Number is Approaching a Lower Limiting Value as the Reynolds Number ADDroaches Zero. © 1987, Gordon and Breach Science Publishers S.A.