The objective of this work was to study the dependence of the heat transfer coefficient (h) on the water loss rate of potato during frying. An indirect method was used where a metal piece with the same geometry of the potato pieces was placed on top of various potato samples at different frying times, and its temperature was recorded for 20–30 s. Another method consisted of direct recording of the temperature within a potato slice, close to the surface. Water loss rate was estimated by image analysis of bubbles. After immersion in hot oil, the potato temperature increases and water starts vapourising, leaving the surface in the form of bubbles that flow through the oil. The water loss rate increases until complete drying of the potato surface and then decreases till the end of frying. The h value showed the same behaviour increasing up by two times in relation to the values measured in the absence of bubbling, with maximum values depending on the oil temperature and potato geometry (443–750 W m−2 K−1). The percentage of heat transferred to the potato that is used for water evaporation showed an increase with time up to complete surface drying.
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机译：这项工作的目的是研究油炸过程中传热系数（h）对马铃薯失水率的依赖性。使用间接方法，将具有相同几何形状的马铃薯块的金属块在不同油炸时间放置在各种马铃薯样品的顶部，并记录其温度20–30 s。另一种方法包括直接记录马铃薯切片内靠近表面的温度。通过气泡的图像分析来估计失水率。浸入热油中后，马铃薯温度升高，水开始蒸发，以气泡形式流过油，使表面变油。失水率增加，直到马铃薯表面完全干燥，然后下降，直至油炸结束。 h值显示的相同行为相对于没有起泡时测得的值增加了两倍，最大值取决于油温和马铃薯的几何形状（443–750 W m-2 K-1）。传递到马铃薯上用于水分蒸发的热量百分比随时间的增加而增加，直至完全干燥为止。
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