An investigation of uncertainties in determining convective heat transfer during immersion frying using the general uncertainty management framework

Although extensively studied (and of large importance for food processing) there is still no general consensus on the time-dependent convective heat transfer coefficient (h) in immersion frying – reported values differ by orders of magnitude (4–7000 W m⁻² K⁻¹). Moreover, none of the many methods suggested have become a generally agreed upon standard. This study uses the general uncertainty management (GUM) framework to analyze the standard uncertainties in four commonly used methods to measure h in immersion frying. It is concluded that the uncertainties (when including all sources of uncertainty in a systematic manner using the GUM) are often substantially larger than previously reported (up to 100% relative uncertainty), i.e., some methods used in previous studies are very sensitive to measurement uncertainties. This can help explain the large variation in previously reported h-values. Comparisons between methods suggest that evaporation rate based methods (with numerical differentiation) provide the highest reliability.