Articles
Peltier element for real-time heat flux detection in fruit cooling under forced air convection
Article number
1396_38
Pages
277 – 284
Language
English
Abstract
Peltier elements are inexpensive and non-invasive sensors that detect heat flux in surfaces when a temperature difference is created.
Once food behaves as a hot body inside the refrigerator, small Peltier elements are suitable for heat flux monitoring in food.
During the initial cooling process, the flow of thermal energy in food occurs through a conduction process from the inside to the surface of the food, followed by dissipation through convection to the surrounding cold air, where air velocity plays a vital role in heat removal.
In this context, the aim of this study was to develop a novel sensor to measure heat flux from the fruit surface to its surroundings.
For this reason, Peltier elements were attached to the fruit surface in order to monitor, in real-time, the cooling kinetics of apples during postharvest storage.
Experiments were conducted inside a wind tunnel under controlled air temperature (1°C) and air velocity (0.5 to 4.0 m s‑1). Temperature sensors were also attached to the fruit in order to monitor and collect data from the surface of the apple.
As a result, the lower the air velocity, the longer it takes for the apple to reach the air temperature, as shown by the cooling kinetics parameters.
Results obtained with the Peltier element showed a faster reduction in heat flux, from fruit to the surroundings, by applying a higher air velocity.
However, the influence of air velocity becomes reduced after a certain velocity.
The Peltier element results were consistent with the cooling kinetics data, which indicates the suitability of this sensor measuring the heat flux in food.
Once food behaves as a hot body inside the refrigerator, small Peltier elements are suitable for heat flux monitoring in food.
During the initial cooling process, the flow of thermal energy in food occurs through a conduction process from the inside to the surface of the food, followed by dissipation through convection to the surrounding cold air, where air velocity plays a vital role in heat removal.
In this context, the aim of this study was to develop a novel sensor to measure heat flux from the fruit surface to its surroundings.
For this reason, Peltier elements were attached to the fruit surface in order to monitor, in real-time, the cooling kinetics of apples during postharvest storage.
Experiments were conducted inside a wind tunnel under controlled air temperature (1°C) and air velocity (0.5 to 4.0 m s‑1). Temperature sensors were also attached to the fruit in order to monitor and collect data from the surface of the apple.
As a result, the lower the air velocity, the longer it takes for the apple to reach the air temperature, as shown by the cooling kinetics parameters.
Results obtained with the Peltier element showed a faster reduction in heat flux, from fruit to the surroundings, by applying a higher air velocity.
However, the influence of air velocity becomes reduced after a certain velocity.
The Peltier element results were consistent with the cooling kinetics data, which indicates the suitability of this sensor measuring the heat flux in food.
Authors
T.G. Hoffmann, U. Praeger, P. Mahajan, M. Geyer, R. Jedermann, M. Linke
Keywords
Peltier element, apple, heat transfer, cold storage, cool chain, refrigeration, air velocity
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