# CFD Analysis of a Tubular Heat Exchanger for the Conditioning of Olive Paste
###### Abstract  
The use of a heat exchanger for the conditioning of the olive paste could enhance the olive oil extraction process. Particularly, paste pre-heating could reduce the malaxation time and, most of all, improve the temperature control during this process (e.g., 27 \({}^{\circ}\)C). In this study, a three-dimensional computational fluid dynamics (CFD) analysis of a tubular heat exchanger was carried out to better understand the influence of the inlet conditions of the olive paste on thermal and hydrodynamic behavior within it. CFD analysis was performed with SOLIDWORKS Flow Simulation (ver.2016). The heat exchanger consists of a tube-in-tube module, in which the inner tube was fed with the olive paste, while the jacket was filled of hot water. The main aim was that to predict the heat transfer and pressure drop in paste side of the exchanger. Multiple analyses by varying the mass flow rate and inlet temperature of the paste were carried out, and temperature and pressure drop were estimated. The numerical model has proved very useful in identifying the main factors affecting the optimization of the heat exchanger in order to improve the extraction process of the olive paste. CFD analysis; heat exchanger; SOLIDWORKS Flow Simulation; oil quality +
Footnote †: journal: Applied Sciences  
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discontinuity of operation of the machine and due to the inadequate ratio between the heat exchange surface and the volume of the processed product, various negative aspects that significantly affect the functionality of the plant and the quality of the final oil occur. These aspects are reported in [9] such as: (i) time and temperature profiles of the olive paste that depend on the filling levels of the malaxer; (ii) time and temperature profile is not uniform for all olive paste particles in the malaxer due to a small portion of olive paste that can remain attached to the walls of the malaxer through many subsequent cycles; (iii) long operating times, in fact, the malaxation process consumes approximately two-thirds of the total time required for extra-virgin olive oil processing. In recent years, enormous efforts are being made in terms of energy saving in the food industry sector [10; 11]. As regards the mechanical extraction process of virgin olive oil (VOO), important lines of research have been focused on the introduction of new technologies to overcome the negative aspects that occur during the malaxation phase and consequently improve the production and quality of VOO. Various technological innovations in the VOO industry have been studied, such as microwave-assisted systems, low-frequency ultrasound, high-frequency ultrasound and pulsed electric fields, to obtain a positive impact on the extractability of the decanter, on the continuity of the process and, in several cases, on the quality of the olive oil [9; 12; 13; 14; 15]. An important innovation introduced in recent years in the mill to significantly reduce the time required to reach the optimal temperature of the olive pastes was the heat exchanger. First research regarding the application of heat exchange in the olive oil extraction process was carried out by [16], introducing a spiral heat exchanger between the crusher and malaxer, which proved to have a positive influence on the improvement of the malaxation efficiency because of the increment of olive oil extraction yield and the significant improvement in olive oil quality. However, due to clogging and cleaning problems at the end of the process related to the spiral heat exchanger, new technologies such as the tube-in-tube heat exchanger have been tested and subsequently implemented, albeit sparingly, in industrial oil extraction plants. Recently, several authors [17; 18] studied the use of tubular heat exchangers experimentally during the olive oil extraction process, to assess its influence on the processing time, olive oil extraction yield and the quality of the olive oil.