Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
DEVELOPMENT AND COMPARISON OF EXPERIMENTAL EMISSIVITY MEASUREMENT METHODS: APPLICATION TO SURFACES FOUND IN OFFSHORE FLARES
Submission Author:
Florian Alain Yannick Pradelle , RJ
Co-Authors:
Pedro Oliveira, Sergio Braga, Florian Alain Yannick Pradelle, Zrinka Romani
Presenter: Pedro Oliveira
doi://10.26678/ABCM.COBEM2021.COB2021-0887
Abstract
With the growth of off-shore oil extraction in recent years, particularly from the pre-salt, it is necessary to adapt the platforms to the new needs, in particular related to the flare. Due to its greater dimension owing to the increase of platform production capacity, the design of offshore flare systems requires special concerns. Thus, it is important to correctly design the flare in terms of flow and heat transfer to guarantee the safe operation of the platform. Moreover, some radiation blocking technology, such as heat shields, can be useful to reach this goal. The present work introduced two techniques for measuring the emissivity of surfaces, commonly used in the structure of heat shields: a Thermal Sprayed Aluminum (TSA) coating, a Jotatemp1000 coating and a raw naval steel surface. The experimental study was based on two different experimental procedures, coupled with a mathematical model that enabled to calculate the heat transfer by convection and radiation and the emissivity. The first method measured the emissivity with the aid of a thermographic camera at five different temperatures, ranging from ambient temperature to 200°C for each surface. Moreover, for TSA and Jotatemp1000 coatings, the emissivities of a flat plate and tube (both coated) were compared to assess the impact of the curvature in the estimation. The second experiment determined the emissivity by estimating the heat transfer by natural convection and radiation in an annular space between an internal cylinder dissipating 15, 30, 45 and 60 W of heat from an electrical resistance and an instrumented external cylinder. To quantify the effects of natural convection, the tests were performed under three different pressures levels. The first experiment exhibited a significant variation between the values measured in tubes and plates for a same surface showing a strong impact of the geometry. In both experiments, the emissivity of all materials remained constant within the uncertainty range for temperature values higher than 100 °C. However, for the Jotatemp1000 coating and the naval steel, a significant difference was observed in the emissivity values depending of the procedures. Such difference can be related to the hypothesis used in the heat transfer model where conduction was considered negligible.
Keywords
radiation, emissivity, Annulus, Experiment, Thermography
