Mathematic Models of Heat Transfer for Frozen Foods

• Main Authors: Yang, Tzong-Rong, 楊宗榮
• Other Authors: Guu Yuan-Kuang
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/24418040629386239133

碩士 === 國立屏東技術學院 === 食品技術研究所 === 85 === AbstractIn this research, the freezing process of potato, carrot, green soybean, corn, taro, hot dog, ham, codfish, beefsteak, fried chicken, hamburger meat patty, minced pork ball, and cuttlefish ball was studied. The freezing curves of various specimens were established by measuring sample's surface and center temperatures using thermocouple and temperature recorder during the freezing process. Thermal properties, such as specific heat capacity, thermal conductivity and thermal diffusivity were calculated according to the empirical equations and the compositions of specimens. Biot number, heat transfer coefficient, and Nusselt number were calculated under different wind speeds (Reynolds number), freezing temperatures, and the thermal properties of experimental specimens. Results indicated that increase of wind speeds and decrease of freezing temperatures were helpful for the freezing process.Mathematical relationships of Nusselt number, Reynolds number, Prandtl number, Geometry factors (G, a/L, and b/L) were derived from different experiment conditions. They wereNu=0.0037(Re^0.734)( Pr^0.333)(G^7.122)((a/L)^1.475)((b/L)^5.501)Nu=0.015(Re^0.693)( Pr^0.333)(G^3.944)((a/L)^0.509)((b/L)^2.573) and for the tested vegetable specimens above and below freezing point, respectively.For the tested meat and fish products above and below freezing point, they wereNu=0.033(Re^0.563)(Pr^0.333)( G^-1.377)((a/L)^-0.271)((b/L)^-1.124)Nu=0.948(Re^0.495)( Pr^0.333)(G^-0.279)((a/L)^-0.494)((b/L)^-0.766) and respectively. The simulated freezing curves were done by the computer programs, and heat transfer equations of different coordinate systems according to sample's geometric characteristics. Results showed that the simulated and experimental values were closely similar. Therefore, these mathematical could be adequately used for predicting the optimal time for different frozen foods in the freezing process. key words: Surface heat transfer coefficient, Mathematic models of heat transfer, Frozen foods.-IV-