Study On Optimization Of Temperature Distribution And Heat Transfer Of Self-heating Food During Self-heating Process

Unbalance of temperature distribution and lack of evaluation indexes were studied in this paper.A new approach was established to rapidly assess eating quality of self-heating food.By optimizing the heating conditions,the efficiency of heater and the edibility of self-heating food were enhanced.According to the multivariate analysis method and principal component analysis,7 evaluation indicators were selected for assessing the quality of self-heating food.The 7 indicators(sweet taste,rice fragrance,grainy,compact structure,glossiness,viscoelasticity,chewiness)respectively represented the appearance of rice,flavor,color,taste,etc.Correlation analysis showed that sweet taste and rice fragrance were positively correlated,viscoelasticity and chewiness were closely correlated.Therefore,sweet taste,compact structure,color,chewiness and grainy were selected as the evaluation indicators for self-heating food quality.Duncan multiple range test and pairing t-testing showed that temperature distribution of self-heating food was symmetrical about food geometric center.Furthermore,the position that was directly contacted with the heater was highest,the position that was between the heaters came second,and the position that was at the edge of food was lowest.The heating processing of single heating device and multi-layer heating device were studied.The exothermal efficiency of heater and heating efficiency were investigated.Within a certain range,with the increase of water addition,heater space,ratio of heater and food,exothermal efficiency and heating efficiency increase gradually.Different increment had a different influence degree.The effect of water addition on exothermal efficiency and heating efficiency was the most remarkable.When water addition was less,heater couldn't fully react with water.As the water addition increased,water was evaporated by heater energy,and convected to cold point of food.While,when water addition was too much,heater particle was surrounded by water,similar to the construction of oil-in-water.Energy released by heater source was mostly used to heat water,not food,resulted to the decrease of heating efficiency.In the study of characteristics of multi-layer heating units,some regularity was found.Heating unit that was between the multi-layer was the highest,heating unit that was in the bottom of multi-layer came second,and heating unit that was on the top of multi-layer was lowest.By single factor experiments and response surface experiments,the optimum heating condition was studied.For single-layer heating unit,the best heating condition was water addition 132 g,heater space 35 mm,ratio of heater and food 64%.The result of the response surface experiment suggested that the effect of water addition and heater space was prominent on the heating efficiency during heating process.The result of heating process could be predicated well and truly by the mathematical model.Optimum conditions were as followed,water addition 3.60 g,heater space 35.50 mm,ratio of heater and food 62.30%.The predicted value of equation was 71.37%.And the result of verification test was 72.24±0.14%,demonstrated that a good coherence lied in between them.