Thermal conductances are computed for relatively simple node geometries that are typical of analytical models of spacecraft. Heat-transfer rates computed with these conductances are compared to heat-transfer rates computed from exact, closed-form mathematical formulas. The comparisons show that most accurate results are obtained with rectangular nodal arrangements and with triangular arrangements with interior angles less than ninety degrees. For rectangles, the conductances obtained from finite-difference, finite-element and centroid methods are identical. For triangles, the finite-element conductances are best. For other quadrilateral arrangements and triangles, the centroid method is the most reliable.