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Placing the thermal nodes at the corners of the radiation surfaces results in greater thermal-model accuracy for a given number of nodes, as compared to the more common practice of placing the thermal nodes at the center of the radiation surfaces. Placing the thermal nodes at the corners does, however, add complications in computing radiant interchange factors. In this paper the accuracy of subdividing elements into radiation sub-elements is compared to the accuracy of allocating elemental radiation couplings to the corner nodes. The comparison shows that, for a given number of nodes, the two methods have nearly the same accuracy, provided good modeling practice is followed in both cases.

Simulation of radiant heat transfer in large systems results in perhaps millions of radiant-interchange factors. In the interest of reducing computation times, some engineers frequently omit the smallest factors. Others combine the smallest factors into effective radiation nodes. Still others reduce the number of radiation factors by introducing fictitious partitions, known as multiple enclosure simplification shields that divide the large system into smaller systems. In this paper we examine the errors introduced by these various techniques and offer a new method that has the same accuracy as incorporating all of the radiation factors but requires little increase in computation time. The methods are compared by application to three simple models that clearly illustrate how significant errors can be generated if the methods are incorrectly applied.

How accurate are your thermal models? Few thermal analysts have the time and budget to test the convergence of their thermal models (e.g., SINDA models) as a function of mesh size. This paper presents guidelines for selecting mesh sizes and other simulation parameters to ensure accurate simulations. We considered the following aspects of thermal models: mesh size as determined by combined conduction, convection and radiation; perferred mesh geometries; treatment of boundaries and boundary conditions; and required time steps.

To provide spacecraft thermal design engineers with the data needed to define the earth albedo and emission, we have analyzed data from the Earth Radiation Balance Experiment (ERBE) over a period of 36 months, covering orbital inclinations of 57 and 99 degrees. Design values of the albedo and earth emission can be obtained from this data directly; however, we present an earth-map (zonal) method for computing design values for any orbital parameters. In addition, the zonal method permits less pessimistic assumptions to be made in a proof-of-design simulation.