In this study, a conjugate gradient method based inverse algorithm is applied to estimate the unknown
frost-layer boundary profile on the external wall of a pipe system using temperature measurements. It is
assumed that no prior information is available on the functional form of the unknown profile; hence the
procedure is classified as the function estimation in inverse calculation. The temperature data obtained
from the direct problem are used to simulate the temperature measurements. The accuracy of the inverse
analysis is examined by using simulated exact and inexact temperature measurements. Results show that
an excellent estimation on boundary profile can be obtained for the test case considered in this study.