SUMMARYThe steady-state responses of four heat flux gauges (Schmidt-Boelter, Gardon, directional flame thermometer (DFT) and hemispherical heat flux gauge (HFG)) were examined under various radiative and convective heating conditions. In radiative environments, Gardon measurements were up to 8% higher than Schmidt-Boelter measurements, but in mixed radiative-convective environments, Gardon measurements were 8-18% below those of the Schmidt-Boelter gauge. This difference increased as the convective portion of the total heat transfer increased, due to discrepancies between the radiation-based calibration environment and the application environment. The DFT data in radiative environments were comparable with the Schmidt-Boelter and Gardon values (within 12%), with the difference largely attributed to natural convection losses from the DFT. In mixed environments, the DFT values were significantly lower than those of the Schmidt-Boelter gauge due to differences in the surface temperatures of the gauges, resulting in the convective flow cooling, rather than heating, the DFT. The HFG heat flux estimates were 35-48% lower than the Schmidt-Boelter measurements under radiative conditions, influenced by large conduction losses from the sensor plate to the gauge housing. Lateral conduction due to a mismatch between the experimental convective flow outlet diameter and the gauge width also affected results from the DFT and HFG.

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Heat flux is an important parameter for characterization of the thermal impact of a fire on its surroundings. However, heat flux cannot be measured directly because it represents the rate of heat transfer to a unit area of surface. Therefore, most heat flux measurements are based on the measurement of temperature changes at or near the surface of interest [1,2]. Some instruments, such as the Gardon gauge [3] and the thermopile [2], measure the temperature difference between a surface and a heat sink. In radiation-dominated environments, this difference in temperature is often assumed to be linearly related to the incident heat flux. Other sensors measure a surface and/or interior temperature and inverse heat conduction methods frequently must be employed to calculate the corresponding heat flux [1,4]. Typical assumptions include one-dimensional conduction heat transfer and negligible heat loss from the surface. The thermal properties of the gauge materials must be known and, since these properties are functions of temperature, the problem often becomes non-linear.

Geocaching is a location-based game where players search for physical containers in the real world using GPS coordinates. Over the past twelve years, Geocaching has grown to include over 1.5 million players. In addition to real world Geocaching, this game has also extended into virtual worlds like Second Life. In this paper, we document our explorations of Geocaching in Second Life. Here we compare it to Geocaching in real life and describe the likely reasons why the game has not created a player base that is as active as real world Geocaching.