Fig. 5. The relative errors of temperature distribution (Eq. [23]) as a function of angle in a parallelepiped (5 by 5 by 5 cm³) with specified needle spacing for (a, b, and c) an adiabatic boundary condition (ABC) and (d, e, and f) a zero surface temperature (ZST) boundary condition with time t = 50, 100, 200, and 300 s and probe spacing r = 6, 10, 15, and 20 mm.