Termophysical properties of cupuaçu pulp at different solids contents

cagro Ciência e Agrotecnologia Ciênc. agrotec. 1413-7054 1981-1829 Editora da Universidade Federal de Lavras Lavras, MG, Brazil This work was accomplished with the aim of determining the termophysical properties, thermal diffusivity, specific heat and thermal conductivity of cupuaçu pulp in three conditions of solids contents: 12ºBrix, 9ºBrix, and partial elimination of the insoluble solids (sieving). The thermal diffusivity was determined by means of Dickerson’s (1965) apparatus, for the specific heat the method of mixtures was used and the thermal conductivity was determined starting from the relationship among thermal diffusivity, specific heat and density. Equations were used for the theoretical calculation of those properties and the results were compared with the experimental values. The average results, obtained for the thermal diffusivity, specific heat and thermal conductivity of the 12ºBrix, 9ºBrix and sieved samples were, respectively: 1.31x10-7, 1.32x10-7 and 1.27x10-7 m²/s; 3.24, 3.71 and 3.18 kJ/kgºC; and 0.44 W/mºC, 0.50 W/mºC and 0.42 W/mºC. a11 Propriedades termofísicas da polpa do cupuaçu com diferentes teores de sólidos1 Termophysical properties of cupuaçu pulp at different solids contents Josalice de Lima AraújoI; Alexandre José de Melo QueirozII; Rossana Maria Feitosa de FigueirêdoII IQuímico Industrial, Av. Aprígio Veloso, 759, Bodocongó, Caixa Postal 10017 – 58109-970 – Campina Grande, Paraíba IIEngenheiro Agrícola - UFPB, Caixa Postal 10017 – 58109-970 – Campina Grande, PB RESUMO Este trabalho foi realizado com o objetivo de determinar as propriedades termofísicas difusividade térmica, calor específico e condutividade térmica da polpa do cupuaçu em três condições de teor de sólidos: integral (12ºBrix), 9ºBrix e com eliminação parcial dos sólidos insolúveis (peneirado). A difusividade térmica foi determinada por meio do aparato de Dickerson (1965); para o calor específico, utilizou-se a metodologia do calorímetro de mistura, e a condutividade térmica foi determinada considerando-se a relação entre a difusividade térmica, o calor específico e a massa específica. Foram utilizadas equações para o cálculo teórico dessas propriedades e os resultados foram comparados com os valores experimentais. Os resultados experimentais médios, obtidos para as difusividades térmicas, calores específicos e condutividades térmicas das amostras integral, 9ºBrix e peneiradas foram, respectivamente: 1,31x10-7, 1,32x10-7 e 1,27x10-7 m2/s; 3,24, 3,71 e 3,18 kJ/kgºC; e 0,44 W/mºC, 0,50 W/mºC e 0,42 W/mºC. Termos para indexação: termofísica, fruta, Theobroma grandiflorum. ABSTRACT This work was accomplished with the aim of determining the termophysical properties, thermal diffusivity, specific heat and thermal conductivity of cupuaçu pulp in three conditions of solids contents: 12ºBrix, 9ºBrix, and partial elimination of the insoluble solids (sieving). The thermal diffusivity was determined by means of Dickerson’s (1965) apparatus, for the specific heat the method of mixtures was used and the thermal conductivity was determined starting from the relationship among thermal diffusivity, specific heat and density. Equations were used for the theoretical calculation of those properties and the results were compared with the experimental values. The average results, obtained for the thermal diffusivity, specific heat and thermal conductivity of the 12ºBrix, 9ºBrix and sieved samples were, respectively: 1.31x10-7, 1.32x10-7 and 1.27x10-7 m2/s; 3.24, 3.71 and 3.18 kJ/kgºC; and 0.44 W/mºC, 0.50 W/mºC and 0.42 W/mºC. Index terms: thermophysical, fruit, Theobroma grandiflorum. Texto completo disponível apenas em PDF. Full text available only in PDF format. (Recebido para publicação em 10 de setembro de 2002 e aprovado em 10 de junho de 2003) 1 Parte da dissertação do primeiro autor apresentada à Universidade Federal da Paraíba. ALVARADO, J. D. Propiedades físicas de frutas. IV: difusividad y conductividad termica efectiva de pulpas. Latin American Applied Research, Ambato, v. 24, n. 1, p. 41-47, 1994. 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