Thermal calculations of two versions reference object CUBI. Prameter test and measurements


  • Jan Fagerström
  • Annica Hjelm
  • Nils Karlsson
  • Roland Lindell
  • Jonas Rahm

Publish date: 2011-10-14

Report number: FOI-R--3268--SE

Pages: 77

Written in: Swedish


  • Thermal calculation
  • IR-modelling
  • temperature measurements
  • LWIR
  • SWIR
  • CUBI
  • RadThermIR


We have performed thermal calculations and measurements of a reference object, CUBI. The work is done to give a better understanding how different parameters influence the thermal behaviour of an object but also how these parameters is treated by the software RadThermIR. This investigation is also a validation of RadThermIR software. CUBI is a well defined object concerning its geometry and material. Measurements are made of its surface temperature by the use of Pt100 elements. IR-images are recorded in a scene dominated by the CUBI. Relevant weather data is collected during the measurements. The measured data is used as reference to the result of calculated data. The results from the calculations roughly follow the same trends and levels as the measured temperature. At some surfaces and moments the temperature differences are almost 10 degrees. This is the case for vertically oriented surfaces only. To further increase the understanding of which parameters that are most critical for the thermal computation a great number of executions of the software is made. Parameters of the CUBI material, weather and convection coefficients are varied. One result of the parameter test is that the convection parameter is particularly important. A change of this parameter has a large influence on the temperatures of the CUBI surfaces. Adjusting this parameter to differently oriented surfaces gives a better compliance between measured and calculated data. The result of this report results in some questions: What is possible or reasonable to simulate with a good accuracy? What compliance is reasonably to achieve in a complex scene?