Determination and Correlation of Heat Transfer Coefficients in a Falling Film Evaporator
Journal of Food Engineering 73 (2006) 320–326 www.elsevier.com/locate/jfoodeng
Determination and correlation of heat transfer coefficients in a falling film evaporator
´ J.S. Prost a, M.T. Gonzalez a b
a,b
, M.J. Urbicain
a,b,*
´ ´ ´ Planta Piloto de Ingenierıa Quımica (PLAPIQUI), Camino La Carrindanga Km 7, (8000) Bahıa Blanca, Argentina ´ ´ ´ Departamento de Ingenierıa Quımica, Universidad Nacional del Sur (UNS), Alem 1253, (8000) Bahıa Blanca, Argentina Received 23 July 2004; accepted 22 January 2005 Available online 23 March 2005
Abstract The aim of the work was to determine the heat transfer parameters of a single effect evaporator under different operating conditions, in order to extrapolate them to a multiple effect unit. The falling film evaporator consisted of 12 stainless steel vertical tubes, 100 OD and 3 m long, having an evaporation capacity of 240 kg/h. In this unit the conditions of each effect of a multiple effect evaporator were simulated, varying the feed concentration and the pressure, setting in this way the saturation temperature and the transfer regime. Obtained values were correlated by means of an equation that links the heat transfer coefficient with the fluid properties, geometric parameters and flow conditions. Comparison with existing correlations was carried out. Ó 2005 Elsevier Ltd. All rights reserved.
Keywords: Heat transfer; Evaporator; Falling film; Coefficient
1. Introduction The concentration of a fruit juice is a widely used practice in the fruit juice manufacturing industry, and it has two main purposes: (1) to reduce the volume and weight of the product, with the subsequent lowering of storage, packaging and distribution costs, and (2) to increase the stability of the juice by reducing its water activity, which is a predominant factor in the majority of the mechanisms of deterioration. Although other methods of concentration such as freezing concentration and reverse osmosis are used nowadays, evaporation is still the
Determination and correlation of heat transfer coefficients in a falling film evaporator
´ J.S. Prost a, M.T. Gonzalez a b
a,b
, M.J. Urbicain
a,b,*
´ ´ ´ Planta Piloto de Ingenierıa Quımica (PLAPIQUI), Camino La Carrindanga Km 7, (8000) Bahıa Blanca, Argentina ´ ´ ´ Departamento de Ingenierıa Quımica, Universidad Nacional del Sur (UNS), Alem 1253, (8000) Bahıa Blanca, Argentina Received 23 July 2004; accepted 22 January 2005 Available online 23 March 2005
Abstract The aim of the work was to determine the heat transfer parameters of a single effect evaporator under different operating conditions, in order to extrapolate them to a multiple effect unit. The falling film evaporator consisted of 12 stainless steel vertical tubes, 100 OD and 3 m long, having an evaporation capacity of 240 kg/h. In this unit the conditions of each effect of a multiple effect evaporator were simulated, varying the feed concentration and the pressure, setting in this way the saturation temperature and the transfer regime. Obtained values were correlated by means of an equation that links the heat transfer coefficient with the fluid properties, geometric parameters and flow conditions. Comparison with existing correlations was carried out. Ó 2005 Elsevier Ltd. All rights reserved.
Keywords: Heat transfer; Evaporator; Falling film; Coefficient
1. Introduction The concentration of a fruit juice is a widely used practice in the fruit juice manufacturing industry, and it has two main purposes: (1) to reduce the volume and weight of the product, with the subsequent lowering of storage, packaging and distribution costs, and (2) to increase the stability of the juice by reducing its water activity, which is a predominant factor in the majority of the mechanisms of deterioration. Although other methods of concentration such as freezing concentration and reverse osmosis are used nowadays, evaporation is still the
References: Ahmed, S. Y., & Kaparthi, R. (1963). Heat transfer studies of falling film heat exchangers. Indian Journal of Technology, 1, 377–381. ALVAL Process Engineering Ltd. (1994). United Nations Development Program, Project No ARG 92R 41. Pilot plant falling film evaporator. Scotland.