Scraped Surface Heat Exchanger Research Articles

Optimization of Scraped Surface Heat Exchanger Process Parameters for Manufacture of Bottle Gourd Halwa

The present investigation has been aimed to study the effect of various process parameters of scraped surface heat exchanger (SSHE) on the sensory characteristics of fresh bottle gourd halwa. The horizontal SSHE designed and fabricated at the Institute was used to manufacture bottle gourd halwa. The freshly prepared bottle gourd halwa samples were analyzed for their sensory characteristics prepared at different scraper speed (R1, R2, R3 at 20, 30 and 40 rpm respectively), and operating steam pressure (G1, G2, G3 at 0.75, 1.0 and 1.5 kg/cm2 respectively) for varying batch size (B1, B2, B3 of 2, 3 and 4 kg respectively). A uniform quality product with respect to flavor, body and texture, color and appearance, and overall acceptability (sensory scoring) was obtained employing the combination of treatments G2B3S2 among the rest of combinations. Cost analysis of bottle gourd halwa prepared in SSHE under operating condition G2B3S2 was computed at `150.35; the raw materials cost and operating cost was `116.82 and `33.53, respectively.

Crystallization of interesterified soybean oil using a scraped surface heat exchanger with high intensity ultrasound

The aim of this research is to crystallize a low saturated interesterified soybean oil (IESBO) using a scraped surface heat exchanger (SSHE) combined with high intensity ultrasound (HIU). The SSHE operated at a flow rate of 3.125 mL/s, crystallization temperature of 32 °C, pressure of 2 bars, and barrels/pin worker speed of 344/208 rpm, respectively. HIU was applied at amplitudes between 20 and 80% using continuous, 5 s or 10 s pulses. The microstructure, melting behavior, rheology, hardness, and oil binding capacity (OBC) of the samples were evaluated. Non-sonicated sample resulted in a crystalline network characterized by 8.9 μm diameter crystals, elasticity values of 25,255Pa, hardness values of 1.3N and OBC values of 61%. Sonication using 50% amplitude for 5 s was the most efficient condition and resulted in a decrease in crystal size to 4.5 μm, an increase in elasticity values to 100,238Pa, and an increase in hardness and OBC values to 3.7N and 81.3%, respectively.

Computational Analysis of Thermal Behavior within a Scraped Surface Heat Exchanger SSHE

Computational Analysis of Thermal Behavior within a Scraped Surface Heat Exchanger SSHE

MHD and heat transfer analyses of a fluid flow through scraped surface heat exchanger by analytical solver

Scraped surface heat exchangers (SSHEs) diversely used in various industries for different settings when continuous processing of fluid and related material is required. In this work, heat transfer for steady incompressible flow of a Newtonian fluid in the presence of high magnetic field with temperature variant viscosity in a small gap of SSHE is studied for a fixed temperature difference narrow gaps between rotor and stator. The fluidic system is modeled mathematically in terms of PDEs for non-isothermal megnetohydrodynamic (MHD) flow with temperature dependent viscosity for linear blade shape. The solution of modeled PDEs are obtained analytically by exploiting the strength of Adomian decomposition method (ADM). The effects of different flow parameters of the systems are studied and their results are presented with analytical expressions and graphical illustrations.

A numerical study on heat transfer enhancement via mechanical aids

The work deals with an experimental and numerical analysis on disturbed thermal boundary layer obtained in a heat exchanger by two rotating blades (scrapers). A three-dimensional numerical model of unsteady forced convection in an analyzed device is proposed and taken into consideration. The model allows for the transient nature of the processes occurring in a very efficient in terms of heat transfer the Scraped Surface Heat Exchanger (SSHE) and the impacts on the body forces such as gravity, centrifugal and Coriolis forces on processes. In order to validate the model, a specially constructed experimental test stand was designed and manufactured. The series of experiments for the Reynolds number equal to 1100 and the Nusselt number in the range of 10–25 were performed and compared with numerical results achieving satisfactory agreement, with the error smaller than 5% for temperature and 9% for the heat flux values. The set of governing equations of conservation of mass, momentum, and energy was solved within the framework of the Finite Volume Method (FVM). The movement of the scrapers was incorporated into the model with the use of the Sliding Mesh Method (SMM). The distributions of temperature and velocity were elaborated and scrutinized. It was found that in the analyzed flow regime, the gap width between the stator wall and the scraping blade tip highly affects the Nusselt number. Moreover, the numerical results were compared with other mathematical models available in the literature and the discrepancy between the conventionally used model based on penetration theory was found.

Concentration of apple juice with an intelligent freeze concentrator

A 2.5-L multi-pass intelligent freeze concentration (FC) prototypical instrument with liquid food freezing point depression (FPD) data built into its controller was tested in this study for the concentration of apple juice. The instrument operates in suspension crystallization mode and integrates a traditional separated scraped surface heat exchanger (SSHE), crystallizer, and washing column into a compact three-in-one structure. Its concentration ratio in a single pass on apple juice was approximately 1.8 (e.g. from 10% to 18%). After three passes of FC, the apple juice concentration increased to 34.5 °Bx; the retention rate of vitamin C and aromatic substances, represented by ethyl butyrate, were both more than 90%, but little change in reducing sugars and color value occurred, and the partition coefficients of soluble solids in ice and the mother liquor were between 0.0081 and 0.067, obtaining a general yield of soluble solids of 97%. The controller correlates the juice concentration with its FPD to log the concentration change, and correlates the mechanical load current with the ice bed maturity to determine the end point of the freeze stage. This study contributes to our knowledge of FC of liquid food and future research and development efforts in this area.

Designing heat exchanger for enhancing heat transfer of slurries in biogas plants

Abstract Heat transfer geometries with enhanced performance for the slurries with high viscosity can improve the net raw biogas production in bio-methane process. In this study, the rheological properties of different slurries were tested, correlated and implemented to computational fluid dynamics (CFD). CFD was then used to screen a new geometry based on the twisted tube combined with mechanism study, and experimental testing was conducted for verification. It shows that the twisted hexagonal tube (THT) has the highest performance. The mechanism for enhancing the heat transfer with THT was mainly due to the effective shear rate. Furthermore, the waste-heat recovery with the THT heat exchanger in biogas production was estimated quantitatively and compared with the normal heat exchanger and scraped-surface heat exchanger (SSHE). Compared to the normal heat exchanger, for THT, the increase of net raw biogas production δNRBP can be up to 17%, while it is only up to 8.53% for SSHE. Besides, the external heating up processes with THT and normal heat exchanger were studied to estimate the heating time for different temperature fluctuations and power requirements of boiler. It is found that the process with THT can save 25-38% heating time for the anaerobic reactor compared to the normal heat exchanger. Therefore, designed THT heat exchanger is promising, and the developed methods can also be beneficial for studying other heat transfer processes.

Effect of high cooling and shear rate on the microstructural development of hybrid systems containing diacylglycerols and triacylglycerols of palm origin

This research explores the potential of diacylglycerol (DAG) and triacylglycerol (TAG) combinations in shortenings. An alternative formulation of a fat blend alters the crystallization behavior, which was investigated with differential scanning calorimetry (DSC) and synchrotron X-ray diffraction. DSC experiments demonstrated that by replacing TAGs with DAGs, crystallization had an earlier onset. However, the lower concentrations of TAGs require more undercooling to fully crystallize, which resulted in more crystallization events during the isothermal step for samples with a higher DAG and lower TAG concentration. A higher DAG concentration also resulted in a more dominant presence of the β polymorphic form. As both DAG and TAG structuring are based on crystal network formation, processing conditions (cooling and shear) will play an important role. Considering processing is essential to understand the behavior of newly formulated fats on an industrial processing line. Samples were prepared both statically, without shear or rapid cooling, and dynamically, under high shear and fast cooling using a bench-top scraped surface heat exchanger. Dynamically crystallized samples containing DAGs were more brittle than samples without DAGs, which can be related to the slower crystallization kinetics of lower TAG concentrations at higher DAG concentrations. The final textural properties of the statically crystallized samples could not predict the properties of the dynamic values. As such, it was demonstrated that preparing crystalline samples using processing conditions similar to those used in an industrial setting is essential to assess applicability of alternatively structured crystalline fat phases.

Safety profile characterization of a cosmetic silanol compound in vivo

The heat transfer process to a non-Newtonian pseudoplastic fluid inside a scraped surface heat exchanger has been experimentally analysed. The scraping device consists of a rod with semicircular pieces mounted on it, which are in contact with the inner surface of the pipe. The whole moves axially and thus, the pieces scrape the inner surface of the pipe, in order to avoid fouling formation and enhance heat transfer.Pressure drop, heat transfer and power consumption measurements, using non-Newtonian pseudoplastic fluids, have been carried out in static and dynamic conditions of the scraper. Four flow regions have been identified: attached laminar, detached laminar, transitional and turbulent flow regions. A generalization method for the fluid viscosity that includes the effects of the non-Newtonian behaviour has been used. Friction factor and Nusselt number have been successfully correlated by employing the generalized viscosity on pressure drop and heat transfer results, both in static and dynamic conditions, for three of the four identified flow regions (it was not possible to get correlations in the transition to turbulent flow region). The study shows that, despite the high power consumption of the scraping movement, the device is suitable for an industrial process using non-Newtonian fluids, since it prevents fouling, increases heat transfer, provides flexibility and enhances the final product quality. Furthermore, the obtained correlations are a valuable tool in the design of heat exchangers.

3-D Numerical Simulation of Scraped Surface Heat Exchanger with Helical Screw

3-D Numerical Simulation of Scraped Surface Heat Exchanger with Helical Screw

Effect of process parameters on ice crystals and air bubbles size distributions of sorbets in a scraped surface heat exchanger

Ice crystals and bubbles size distributions were characterized for aerated sorbets produced during a crystallization-foaming process in a scraped surface heat exchanger. Size measurements were performed immediately at the exit of the heat exchanger by means of a low-temperature microscopy method especially developed in order to discriminate between ice crystals and bubbles and to make possible to measure both sizes simultaneously. The influence of process parameters such as refrigerant fluid evaporating temperature and air flowrate on both size distributions was investigated. Larger ice crystals were obtained when refrigerant fluid temperature increased, but this effect was minimized by the presence of air which retards crystal growth by insulation and hindrance effect. Low refrigerant fluid temperature led to small air bubbles size because of the enhancement of bubbles breakup by shear forces. Ice crystals size was reduced when air flowrate was increased, even if the effect was less pronounced at the lower refrigerant fluid temperature. Variations on air flowrate had a very small effect on air bubbles size.

Study of a Eyring–Powell Fluid in a Scraped Surface Heat Exchanger

Flow of a Eyring–Powell fluid in a scraped surface heat exchangers (SSHEs) is analyzed. Foodstuff behaves as non-Newtonian material so for studying non-Newtonian effects inside SSHE Eyring–Powell fluid model is considered. As every physical phenomena can be interpreted mathematically therefore in this work we mathematically studied flow inside SSHE. Steady isothermal incompressible flow of Eyring–Powell fluid about a periodic sequence of pivoted scraper blade in channel with one moving wall and other is stationary, pressure gradient is imposed in the direction transverse to the wall motion is modelled using lubrication approximation theory as the gap with the blades and device wall are narrow. The resulting nonlinear boundary value problem is solved using Adomian decomposition method. Expression for velocity profiles for different region, flow rates, stream function, forces on the wall and on the blade are found. Graphical representation for velocity profile and for different flow parameter involved is also discussed. Parabolic velocity profiles in various region of SSHE are obtained which are in line with the experimental results obtained through MRI.

Experimental study of heat transfer to non-Newtonian fluids inside a scraped surface heat exchanger using a generalization method

The heat transfer process to a non-Newtonian pseudoplastic fluid inside a scraped surface heat exchanger has been experimentally analysed. The scraping device consists of a rod with semicircular pieces mounted on it, which are in contact with the inner surface of the pipe. The whole moves axially and thus, the pieces scrape the inner surface of the pipe, in order to avoid fouling formation and enhance heat transfer.Pressure drop, heat transfer and power consumption measurements, using non-Newtonian pseudoplastic fluids, have been carried out in static and dynamic conditions of the scraper. Four flow regions have been identified: attached laminar, detached laminar, transitional and turbulent flow regions. A generalization method for the fluid viscosity that includes the effects of the non-Newtonian behaviour has been used. Friction factor and Nusselt number have been successfully correlated by employing the generalized viscosity on pressure drop and heat transfer results, both in static and dynamic conditions, for three of the four identified flow regions (it was not possible to get correlations in the transition to turbulent flow region). The study shows that, despite the high power consumption of the scraping movement, the device is suitable for an industrial process using non-Newtonian fluids, since it prevents fouling, increases heat transfer, provides flexibility and enhances the final product quality. Furthermore, the obtained correlations are a valuable tool in the design of heat exchangers.

Influence of operating conditions on residence time distributions in a scraped surface heat exchanger during aerated sorbet production

The residence time distribution (RTD) inside a scraped surface heat exchanger (SSHE) during simultaneous crystallization-foaming process for continuous production of an aerated sorbet was studied. The effect of mix flowrate, air flowrate and refrigerant temperature on the unfrozen liquid/ice crystals phase RTD was investigated using a dye tracer method. The experimental results revealed that both mix and air flowrates increase leads to a lessening of the minimum and of the mean residence time inside the SSHE. Flow diagnosis showed the presence of a nearly stagnant air pocket which volume increase with the air flowrate increase, resulting in an augmentation of the liquid phase velocity. More axial dispersion was observed at higher air flowrates and at lower refrigerant temperature due to greater radial temperature and axial velocity gradients. These conclusions were confirmed by the parameters of the fitted flow models (axial dispersion, tank-in-series and gamma distribution models) even if only the gamma distribution model succeeded to well describe the flow patterns observed. The findings of this pioneering work in the field of gas-liquid flow in SSHEs might be useful for several applications involving multiphasic flow in SSHEs.

Modeling flow and heat transfer in a scraped surface heat exchanger during the production of sorbet

A computational fluid dynamics model was implemented for studying the production of non-aerated sorbet in a scraped surface heat exchanger under different operating conditions. The coupled problem of fluid flow and heat transfer is solved by taking into account realistic values for the product physical properties as well as its complex rheology. The mathematical solution of the coupled problem represents a challenging task, among other reasons by the strong influence of temperature on product physical properties and rheology due to phase change. Fluid flow, heat transfer freezing and viscous dissipation phenomena are analyzed locally in the heat exchanger. The modeling approach is consistent, as indicated by comparisons between model predictions of the temperature profile along the heat exchanger and available experimental results.

Mechanism of waste-heat recovery from slurry by scraped-surface heat exchanger

Waste-heat recovery from discharged slurries can improve the net raw biogas production in the bio-methane process in order to meet the demand for a next-generation of anaerobic digestion. In this study, a numerical model of a scraped-surface heat exchanger was proposed with the consideration of the complete and precise rheological behaviour of the slurry of animal manure for the first time for achieving highly efficient waste-heat recovery. The rheological model results were verified with new experimental data measured in this work. Subsequently, the convective heat-transfer coefficient of the scraped-surface heat exchanger was calculated numerically with the proposed numerical model, and the performance was determined. Then, the contributions of waste-heat recovery from the slurry to the biogas production using a general shell-and-tube heat exchanger and the scraped-surface heat exchanger were calculated quantitatively and compared. For the case of scraped-surface heat exchanger, the increase of net raw biogas production can be up to 8.53%, which indicates that there is a great potential to increase the net raw biogas production in the bio-methane process using a scraped-surface heat exchanger with low-cost equipment and a compactible structure.

Horizontal scraped surface heat exchanger — Experimental measurements and numerical analysis

This paper deal with the overall heat transfer process and confrontation of experimental measurements and their numerical solutions on simplified model, inside the horizontal scraped surface heat exchanger. The experimental measurements were done on two horizontal scraped surface heat exchangers connected in series. As a product was thermally treated water, heated by vapor in the first stage and cooled by cold water in the second stage. Applied mass flow of the product: m=250, 500, 750, 1000 kgh−1 and rotary velocity of the shaft, scraper blades: rpm=20, 30, (45), 60, 90 min−1. For numerical analyses the simplified model was used, with taking only the area between the heat transfer tube, and the shaft with an aim to compare the result to experimental measurements and validate the obtained overall heat exchange, as justify the simplification. As a results from experimental measurements were obtained the correlations for Nusselt number in a form of Nu=f(Re,Pr,ηf/ηw). Based on the confrontation of results, it can be stated that the level of simplification used at numerical solutions, gives still an acceptable accuracy of overall heat transfer values. From numerical simulations were obtained further results as the velocity, temperature fields, which were used to make certain adaptation on proposed construction and their examination by additional numerical simulations. All these acquired results lead to better understanding the overall process inside the horizontal scraped surface heat exchangers and the proposed construction of mutators can increase the efficiency of heat transfer process for many products in a real processing.

Heat transfer enhancement in turbulent drag reducing surfactant solutions by agitated heat exchangers

Drag reducing solutions can reduce turbulent pressure loss by nearly 90% and can decrease pumping energy requirements and increase flow rates in fluid flow systems. Unfortunately, drag reduced flow is accompanied by lower convective heat transfer coefficients, which is undesirable in district heating and cooling systems, heated tube bundles for undersea petroleum production, and other recirculating heat transport systems.In this study, three different rotating agitators were installed inside the inner tube of a concentric tube heat exchanger to enhance heat transfer in a surfactant drag reducing solution. An earlier mathematical model for heat transfer in scraped surface heat exchangers was adapted for this application so that the effectiveness of agitators with different geometries could be compared quantitatively. In addition, an enhancement efficiency factor was defined to compare power efficiency with previous methods. It was found that agitation can increase the effective inner heat transfer coefficient to exceed that of pure water; heat transfer reduction compared to water was reduced from 60% to −20%. In addition, the enhancement can be more energy-efficient than that of previously studied static mixers.

Avaliação do armazenamento a frio sobre os compostos bioativos e as características físico-químicas e microbiológicas do suco de umbu pasteurizado

Resumo Este trabalho teve como objetivo avaliar o efeito do armazenamento a 6 °C nas características do suco de umbu pasteurizado. A pasteurização foi realizada a 86 °C por 25 s em um pasteurizador de superfície raspada, sendo o suco de umbu mantido a 6 °C por 90 dias. O suco pasteurizado atendeu ao padrão estabelecido pela legislação brasileira com contagem <3 NMP.g-1 para coliformes a 45 °C e ausência de Salmonella sp. Nesta condição de processo, a pasteurização foi eficiente também para a redução de bactérias aeróbias mesófilas. O teor de compostos fenólicos totais e, em particular, da rutina, assim como a atividade antioxidante do suco, não foram afetados pelo tratamento térmico. Ao longo do armazenamento, apesar de não perceptível visualmente, os parâmetros de cor do suco variaram significativamente (p<0,05). Apesar de pequena, também houve variação significativa (p<0,05) nos teores dos compostos fenólicos e de carotenoides. Por outro lado, o suco de umbu se manteve microbiologicamente estável durante o armazenamento, sendo, portanto, possível sua conservação por um período de 90 dias sem o uso de aditivos, quando submetido à pasteurização e mantido sob refrigeração.

Mechanization and optimization of parameters for the preparation of Burfi in Multipurpose Scraped Surface Heat Exchanger

Indian sweet-Burfi is very popular khoa based confection with added sugar as well as flavoring and taste imparting ingredients which is very popular all over India. In India mostly the product is manufactured manually in open pan by manual scraping. The quality of product is not uniform due to human intervention and batch to batch variation is also there. The throughput of the product is also low as it done manually. The multipurpose scraped surface heat exchanger has been designed and developed at Dairy engineering department of SMC College of Dairy Science, AAU, Anand. The optimization of process parameters for mechanized production of burfi in the multipurpose scraped surface heat exchanger has been studied. Load size, scrapper speed and steam pressure varied in different trials. The quality of the product was analyzed in terms of sensory analysis. The steam and electrical power consumption was estimated during the manufacture of burfi. The operating conditions of the SSHE required are 2.5 kg/cm2 steam pressure, 30 rpm scraper speed and 30 kg loading. The steam and electrical power requirements for the manufacture of Burfi are 1.45 kg per kg of water evaporated and 0.12 kWh per kg of product respectively.