Mathematical modeling of temperature profiles during un-steady cooling of fruits stored in a cold store unit

Abstract

Temperature is an important parameter controlling the life of fruits in cold store units. Cooling the fruits within earliest time after harvest is very crucial. Relative Humidity (RH) and gas composition within the store rooms are critical apart from temperature to improve the shelf life of the produce. Finding cooling kinetics during un-steady heat transfer period is required for effective storage of fruits and vegetables. The present study was carried to monitor temperature profile of carrots during initial cooling period. Approximately 50MT of carrots were stored in a cold store using perforated plastic crates of 20 kg capacity each. Holding temperature was 5^oC + 0.2andRH 90-95%. Carbon dioxide levels were maintained at 0.5%. The data was recorded using Carel make temperature and RH sensors. Time taken to cool themfrom25^oC to 5^oC was 21hours. After achieving the holding temperature, same conditions of 5^oC were maintained throughout storage. During un-steady state, the first 24 hours is very critical to understand the heat liberating behavior of produce. So the temperature data were modeled with three different mathematical equations. Best fit of predicted Vs experimental values was found with third order polynomial equation with R² Value of 0.998 for 50 Metric Tons (MT) and second order model for 100MT quantity with R ²value of 0.995. This data will be useful for further design of refrigeration systems to cool them quickly especially in high capacity cold storage units.

Key words: Temperature profile, Relative Humidity, Fruit and Vegetable storage, Cold store unit, Mathematical modeling.