1/18/2024 0 Comments Pasteurization unit calculation![]() The internal diameter of the product line (stainless steel tubing) is 7.75 mm or 9.40 mm (nominal 3/8” or 1/2”, respectively), depending on the process step. The unit has a nominal capacity of 0.5 L/min, a maximum flowrate of 3.0 L/min and a maximum processing temperature of 150 ☌. The RTD of a continuous flow microwave-assisted pasteurization unit Lab25-UHT/HTST EHVH (MicroThermics, Raleigh, USA) was characterized through tracer pulse experiments. 2 Material and methods 2.1 Pasteurization unit This will be illustrated through the study of the RTD of a continuous flow pilot unit used for microwave-assisted pasteurization of low viscosity liquid foods. ![]() This work aims to present a procedure to remove distortions in measured RTD data of holding tubes and other process steps caused by non-ideal tracer detection, using convolution in the time domain. verified that this procedure is very sensitive to noises which lead to a poor RTD characterization. While the most common procedure is the deconvolution method in frequency domain, ,, Serres et al. ![]() To the authors knowledge, few studies have used a convolution procedure in the time domain to study the RTD of systems, including the correction of distortions caused by in-line detection systems. Studies have also been carried on the RTD of short holding tubes, of high-pressure food process, of systems with particulate fluids, and of a microwave-assisted pasteurization system. Rennie and Raghavan developed a numerical study for a double-pipe helical heat exchanger to determine the residence time, temperature and lethality distributions. Studies on the RTD of the heating section of a thermal process were conducted for different systems, such as plate heat exchangers, scraped surface heat exchangers, tubular heat exchangers, and even coaxial heat exchanger used for micro reaction systems. RTD is a useful resource for detecting flow anomalies, such as stagnant zones and bypassing. Ī number of researchers have studied flow patterns and their effects on thermal processing of liquid foods. Also, the higher the number of bends, the narrower the E-curve becomes. When secondary flow is present, the transition from laminar to turbulent flow occurs at higher Reynolds numbers and Dean number becomes relevant to the study. Studies have confirmed that the use of helical tubes in laminar flow reduces the axial dispersion and the spread of the residence time due to the presence of a secondary flow, in comparison with straight tubes under the same conditions. (2010).įor the thermal processing of liquid foods, helically coiled tubes are often used in the heat exchangers and holding tube. Įffect of non-ideal tracer detection and the measured E-curve of the system, adapted from Gutierrez et al. The area under the curve is unitary, as shown in Eq. (1), where C 0 is the work fluid background concentration, if existent. The exit age distribution curve E( t) of a process is calculated from Eq. The distribution of fluid elements flowing through a system is represented by the E-curve, which can be obtained through pulse experiments using a tracer. The study of the residence time distribution (RTD) is important for the characterization of flow in continuous pasteurization units to evaluate the level of dispersion and the flow pattern. This can result in undesired degradation of nutrients and bioactive compounds by over processing. However, the heating and cooling sections do have some contribution to the lethality when heat transfer is slow, as well as the velocity profile in the holding tube. For process design, only the target inactivation that occurs in the holding tube at the minimum residence time is considered. The effect of the time and temperature in the inactivation of microorganisms and enzymes can be evaluated through the lethality function for first order kinetics. When processing liquid foods with high viscosities or with particulate matter, tubular heat exchangers are more appropriate than plate heat exchangers due to pressure drop limitations. In such processes, plate heat exchangers are commonly used for heating and cooling, while a holding tube ensures the desired holding time at the process temperature. Continuous pasteurization of liquid foods is a common process in the food industry and is designed for the inactivation of pathogens and also microorganisms and enzymes that reduce the product shelf life.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |