Assessment of Mixing by Chemical Probe in Swirl Flow HEX Reactors

2012 ◽  
Author(s):  
Akram Ghanem ◽  
Thierry Lemenand ◽  
Dominique Della Valle ◽  
Hassan Peerhossaini
Keyword(s):  
Heat Exchanger ◽  
High Performance ◽  
Low Cost ◽  
Swirl Flow ◽  
Adaptive Procedure ◽  
Chemical Probe ◽  
Stirred Tanks ◽  
Thermal Transfer ◽  
Liquid Liquid Extraction ◽  
Competing Reactions

Mixing is a fundamental issue in process engineering and many industrial fields. It is closely related to a large number of different applications, such as chemical reactions, thermal transfer, liquid-liquid extraction, crystallization, and the like. In fact, mixing whether at the reactor scale, sustained by the flow structures, or at molecular scales, influences the selectivity and hence the productivity of reactions. Understanding and quantification of the micromixing mechanism is critical in industrial chemical processes, especially for fast exothermal reactions. Micromixing can be characterized by chemical probe methods based on observation of a local chemical reaction that results from a competition between turbulent mixing at microscales and the reaction kinetics. A system of parallel competing reactions producing iodine was developed by Fournier et al. [1] to study partial segregation in stirred tanks. The coupling of the borate neutralization and the Dushman reaction in this system allows the measurement of micromixing efficiency in reactors by monitoring the amount of iodine produced. Called the iodide-iodate method, this technique has been extensively used in different types of reactors. A novel adaptive procedure recently developed by the authors to improve the reliability of the iodide-iodate method is used here. The heat exchanger-reactor presented here is an innovative geometry based on the addition in parallel of tubes equipped with helical inserts. It is expected to qualify as a low-cost compact heat-exchanger reactor and static mixer of high performance.

Optimal Allocation of Heat Exchanger Inventory of a Two-Stage Vapor Compression Cycle for Maximum Coefficient of Performance

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
M. J. Morales ◽  
S. A. Sherif
Keyword(s):  
Heat Exchanger ◽  
High Performance ◽  
Optimal Allocation ◽  
Low Cost ◽  
Coefficient Of Performance ◽  
Vapor Compression ◽  
Refrigeration System ◽  
Two Stage ◽  
Inventory Allocation ◽  
Maximum Coefficient

The purpose of this study is to investigate how the heat exchanger inventory allocation plays a role in maximizing the thermal performance of a two-stage refrigeration system with two evaporators. First, the system is modeled as a Carnot refrigerator and a particular heat transfer parameter is kept constant as the heat exchanger allocation parameter is allowed to vary. The value of the heat exchanger allocation parameter corresponding to the maximum coefficient of performance (COP) is noted. The results are compared to those of a non-Carnot refrigerator with isentropic and nonisentropic compression. It is found that the Carnot refrigerator can be used to predict the value of the heat exchanger allocation parameter where the maximum COP occurs for a non-Carnot refrigerator. In order to improve the accuracy of that prediction, the predicted value of the heat exchanger allocation parameter has to be inputted into the set of equations used for the non-Carnot refrigerator. This study is useful in designing a low-cost, high-performance refrigeration system.

Optimal Allocation of Heat Transfer Surface of a Two-Stage Refrigeration System

Volume 4 ◽  
2004 ◽  
Author(s):  
M. J. Morales ◽  
S. A. Sherif
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
High Performance ◽  
Optimal Allocation ◽  
Low Cost ◽  
Coefficient Of Performance ◽  
Refrigeration System ◽  
Two Stage ◽  
Isentropic Compression ◽  
Inventory Allocation

The purpose of this study is to investigate how the heat exchanger inventory allocation plays a role in maximizing the thermal performance of a two-stage refrigeration system with two evaporators. First, the system is modeled as a Carnot refrigerator and a particular heat transfer parameter is kept constant as the heat exchanger allocation parameter is allowed to vary. The value of the heat exchanger allocation parameter corresponding to the maximum coefficient of performance (COP) is noted. The results are compared to those of a non-Carnot refrigerator with isentropic and non-isentropic compression. It is found that the Carnot refrigerator can be used to predict the value of the heat exchanger allocation parameter where the maximum COP occurs for a non-Carnot refrigerator. In order to improve the accuracy of that prediction, the predicted value of the heat exchanger allocation parameter has to be inputted into the set of equations used for the non-Carnot refrigerator. This study is useful in designing a low cost, high-performance refrigeration system.

scholarly journals Investigation of Thermo-Hydraulics Flow and Augmentation of Heat Transfer in the Circular Pipe by Combined Using Corrugated Tube with Dimples and Fitted with Varying Tape Insert Configurations

2021 ◽  
Vol 39 (2) ◽  
pp. 365-374
Author(s):  
Ahmed Ramadhan Al-Obaidi ◽  
Jassim Alhamid
Keyword(s):  
Heat Exchanger ◽  
High Performance ◽  
Research Work ◽  
Industrial Applications ◽  
Swirl Flow ◽  
Geometrical Parameters ◽  
Twisted Tape ◽  
Computational Calculations ◽  
Important Field ◽  
Passive Technique

In various industrial applications, the high performance of heat exchanger demand is increasing. Subsequently, the energy resources depletion, for instance, in power plant, air-conditioning system and food processing systems. The important field for saving energy was through improving thermal performance, which can provide high performance heat exchanger. Present enhancing approaches can be classified by three changed types, which are passive technique, active technique and compound technique. Dimple, twisted tape and corrugated pipe are the passive heat improvement technique which includes more surface extensions. Hence, this research work concentrates on verifying the computational calculations of flow in the heat exchanger pipe with different surface extensions in the pipe. It is carried out for turbulent flow with a range of Reynolds number from 1000 to 15000 using CFD methods. The numerical outcomes illustrate that change twisted tape configurations have more effect on flow and heat performance. Experimental and numerical results agreement can confirm the simulation technique reliability, which adopts in this investigation. The deviation errors are observed by less than 6% compared with the normal pipe. Pressure drop increases due to the rise of twisted tape dimensions (width and thickness), leading to more mixing of fluid, secondary flow, and swirl flow inside the pipe. As the tape geometrical parameters increase, the f value also increases due to more variance in velocities flow between liquid layers, which are adjacent to tape surfaces a pipe wall, and pipe core flow layers, become higher. Correspondingly, compared to the normal pipe, twisted configurations can rise f about 5.4 to 33.5%. The better thermal evaluation factor is at a twisted tape of 1x1 mm at Re number of about 1000. The range value of the thermal evaluation factor is more than 1.67.

Comparison of UV- and Derivative-Spectrophotometric and HPTLC UVDensitometric Methods for the Determination of Amrinone and Milrinone in Bulk Drugs

2020 ◽  
Vol 16 (3) ◽  
pp. 246-253
Author(s):  
Marcin Gackowski ◽  
Marcin Koba ◽  
Stefan Kruszewski
Keyword(s):  
Thin Layer ◽  
Thin Layer Chromatography ◽  
High Performance ◽  
Low Cost ◽  
Uv Spectra ◽  
Derivative Spectrophotometry ◽  
Therapeutic Monitoring ◽  
Bulk Drug ◽  
Layer Chromatography ◽  
Standard Solutions

Background: Spectrophotometry and thin layer chromatography have been commonly applied in pharmaceutical analysis for many years due to low cost, simplicity and short time of execution. Moreover, the latest modifications including automation of those methods have made them very effective and easy to perform, therefore, the new UV- and derivative spectrophotometry as well as high performance thin layer chromatography UV-densitometric (HPTLC) methods for the routine estimation of amrinone and milrinone in pharmaceutical formulation have been developed and compared in this work since European Pharmacopoeia 9.0 has yet incorporated in an analytical monograph a method for quantification of those compounds. Methods: For the first method the best conditions for quantification were achieved by measuring the lengths between two extrema (peak-to-peak amplitudes) 252 and 277 nm in UV spectra of standard solutions of amrinone and a signal at 288 nm of the first derivative spectra of standard solutions of milrinone. The linearity between D252-277 signal and concentration of amironone and 1D288 signal of milrinone in the same range of 5.0-25.0 μg ml/ml in DMSO:methanol (1:3 v/v) solutions presents the square correlation coefficient (r2) of 0,9997 and 0.9991, respectively. The second method was founded on HPTLC on silica plates, 1,4-dioxane:hexane (100:1.5) as a mobile phase and densitometric scanning at 252 nm for amrinone and at 271 nm for milrinone. Results: The assays were linear over the concentration range of 0,25-5.0 μg per spot (r2=0,9959) and 0,25-10.0 μg per spot (r2=0,9970) for amrinone and milrinone, respectively. The mean recoveries percentage were 99.81 and 100,34 for amrinone as well as 99,58 and 99.46 for milrinone, obtained with spectrophotometry and HPTLC, respectively. Conclusion: The comparison between two elaborated methods leads to the conclusion that UV and derivative spectrophotometry is more precise and gives better recovery, and that is why it should be applied for routine estimation of amrinone and milrinone in bulk drug, pharmaceutical forms and for therapeutic monitoring of the drug.

Azo (Hydrazone) pigments: general principles

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Robert Christie
Keyword(s):  
High Performance ◽  
Metal Salt ◽  
Low Cost ◽  
Cost Effective ◽  
Precipitation Process ◽  
Ambient Temperatures ◽  
Technical Performance ◽  
Chemical Structures ◽  
General Chemical ◽  
Physical Form

Abstract This paper presents an overview of the general chemical principles underlying the structures, synthesis and technical performance of azo pigments, the dominant chemical class of industrial organic pigments in the yellow, orange, and red shade areas, both numerically and in terms of tonnage manufactured. A description of the most significant historical features in this group of pigments is provided, starting from the discovery of the chemistry on which azo colorants are based by Griess in the mid-nineteenth century, through the commercial introduction of the most important classical azo pigments in the early twentieth century, including products known as the Hansa Yellows, β-naphthol reds, including metal salt pigments, and the diarylide yellows and oranges, to the development in the 1950s and 1960s of two classes of azo pigments that exhibit high performance, disazo condensation pigments and benzimidazolone-based azo pigments. A feature that complicates the description of the chemical structures of azo pigments is that they exist in the solid state as the ketohydrazone rather than the hydroxyazo form, in which they have been traditionally been illustrated. Numerous structural studies conducted over the years on an extensive range of azo pigments have demonstrated this feature. In this text, they are referred to throughout as azo (hydrazone) pigments. Since a common synthetic procedure is used in the manufacture of virtually all azo (hydrazone) pigments, this is discussed in some detail, including practical aspects. The procedure brings together two organic components as the fundamental starting materials, a diazo component and a coupling component. An important reason for the dominance of azo (hydrazone) pigments is that they are highly cost-effective. The syntheses generally involve low cost, commodity organic starting materials and are carried out in water as the reaction solvent, which offers obvious economic and environmental advantages. The versatility of the approach means that an immense number of products may be prepared, so that they have been adapted structurally to meet the requirements of many applications. On an industrial scale, the processes are straightforward, making use of simple, multi-purpose chemical plant. Azo pigments may be produced in virtually quantitative yields and the processes are carried out at or below ambient temperatures, thus presenting low energy requirements. Finally, provided that careful control of the reaction conditions is maintained, azo pigments may be prepared directly by an aqueous precipitation process that can optimise physical form, with control of particle size distribution, crystalline structure, and surface character. The applications of azo pigments are outlined, with more detail reserved for subsequent papers on individual products.

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