An integral model of jet fires, originally developed for free fires, has been extended to predict the internal flame structure of jet fires normally impacting cylindrical obstacles, and to predict the radiative and convective loading on the impacted obstacle, based on that flame structure. Predictions of mean temperatures, gaseous species and soot concentrations, provided by the integral model, are used in an adaptation of the discrete transfer method and a single grey-plus-clear gas radiation model to determine radiative fluxes. An independent assessment of the performance of the model in determining radiative heat transfer is presented for both laboratory and field scale fires. Convective loading to the impacted obstacle is determined via a Nusselt number/Reynolds number correlation, where local mean velocities, temperatures and thermodynamic properties of the flow are derived from the integral model. The performance of the complete model for predicting total fluxes to impacted obstacles has been assessed by comparing model predictions with data obtained from field scale experiments. In situations where the simplifying assumptions of the integral model for flame structure can be applied, predictions of the model are shown to be in good agreement with the available data.