A large-scale experiment was performed to measure heat transfer to a massive cylindrical calorimeter engulfed in a 30 minute circular-pool fire. This test simulated the conditions of a truck-sized nuclear waste transport package in a severe fire. The calorimeter inner surface temperature and the flame environment emissive power were measured at several locations as functions of time. An inverse heat conduction technique was used to estimate the net heat flux to the calorimeter. Tall porous fences surrounded the test facility to reduce the effect of wind on the fire. Outside the fences, 2.9 m/s winds blew across the calorimeter axis at the beginning of the test but decreased with time. The wind tilted and moved the fire so that the initial flame environment emissive power was substantially less on the windward side than the leeward side. The calorimeter became more uniformly engulfed as the winds decreased. The maximum heat flux to the calorimeter was 150 MW/m2 on the leeward side at the beginning of the fire, and generally decreased with time. The local variations of calorimeter temperature and heat flux were closely related to the local flame environment emissive power.
Quasi-steady-state heat fluxes absorbed on the calorimeter surface in ten vertical 0.1 m highx 1 m wide zones were measured by means of water calorimetry. The calorimeter surface also included an array of intrinsic thermocouples to measure surface temperatures, and an array of Schmidt-Boelter radiometers for a second, more responsive, method of heat flux measurement. The pool fire environment characterization was done with measurements from velocity probes, directional flame thermometers (DFTs), and thermocouples. The initial measurements with a 1 m x 1 m water cooled vertical flat plate calorimeter located 0.8 m above and inside a 6 m x 6 m JP-4 pool fire are described. Water calorimetry measured absorbed surface heat fluxes of about 65-70 kW m-2 with a gradual decrease with increasing height above the pool. Intrinsic thermocouple measurements recorded typical calorimeter surface temperatures of about W C , with spatial variations of f 150°C. Gas velocities across the calorimeter face averaged 3.4 m s-' with a predominant upward component, but with an off-vertical skew. Analysis of data collected in the fire environment in the vicinity of the calorimeter was performed to characterize the fire environment and to determine the input parameters required to calibrate analytical models. For this test, the emissive power distribution near the plate was essentially linear. Flux measurement in the fire environment ranged from 75 kW m-2 to 175 kW m-2. With temperature and heat flux data, effective absorption coefficients were determined by using a two-flux method to solve the inverse problem. The results show that the optical thickness increases with increasing distance from the calorimeter surface. The effective absorption coefficient is approximately 0.8 m-l in the vicinity (0-1.85 m) of the calorimeter and is approximately 2 m-l in the vicinity (1.85-2.8 m) of the plume centerline. The observed decrease in heat flux on the calorimeter surface with increasing vertical height is consistent with analytical fire models derived for constant temperature surfaces. Results from several diagnostics also indicated trends and provided additional insight into events that occurred during the fire. Some events are correlated, and possible explanations are discussed.
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