scholarly journals Optimization of the operation mode of regenerative heat exchangers

2021 ◽  
Vol 2119 (1) ◽  
pp. 012156
Author(s):  
Yu V Shatskikh ◽  
A I Sharapov ◽  
A G Arzamassev ◽  
Yu A Geller
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Heating Temperature ◽  
Operation Mode ◽  
High Heat ◽  
Equivalent Diameter ◽  
Regenerative Heat ◽  
Air Heating ◽  
Relative Water ◽  
The One

Abstract The paper considers the operation of regenerative heat exchangers with a fixed checkerwork. Such a checkerwork allows for high-temperature heating of gases and is made of refractory materials with a relatively high heat capacity, but low thermal conductivity. The article presents calculations of regenerative heat transfer for devices with block checkerwork. It is shown that a decrease in the equivalent diameter of the channel d e leads to an increase in the average air heating temperature over the period. An increase in the relative water section of the checkerwork f also leads to an increase in the air heating temperature, but only to a certain limit. On the one hand, with an increase in the relative water section, the specific heat exchanger surface increases. On the other hand, at a certain value f, the accumulating mass of the checkerwork significantly decreases, and as a result, the air heating temperature decreases. For the same reason, for checkerwork with a high value of the relative water section, it is necessary to reduce the duration of the heating/cooling periods of the checkerwork. The paper also examines several types of compact checkerwork, which are very promising, including in heat storage systems. It is noted that the use of such attachments in conventional regenerate heat exchangers is impossible. First, it is necessary to increase the water section of the heat exchanger and significantly reduce its height, otherwise, the pressure loss will increase sharply. Secondly, it is necessary to significantly reduce the duration of the heating/cooling periods, otherwise, due to more intense heat exchange, the air temperature at the outlet of the regenerative heat exchanger changes much more than in the block checkerwork.

scholarly journals Influence of coolant flow rates on the heat exchanger parameter at variable operation modes

Vestnik MGSU ◽  
2019 ◽  
pp. 621-633 ◽  
Author(s):  
Tatyana A. Rafalskaya ◽  
Valery Ya. Rudyak
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Operation Mode ◽  
Coolant Flow ◽  
Flow Rates ◽  
Variable Heat ◽  
Operation Modes ◽  
Mathcad Software ◽  
The Given ◽  
Supply Systems

Introduction. Being used in various industries, heat exchangers most often work under conditions of variable coolant flows and temperatures. At the same time, the existing theories of calculating the heat exchanger operation modes are based on the use of constant unitless parameters at any operation mode. Taking into account the effect of coolant rates on the heat transfer coefficient of the heat exchangers, the given relations are bound to specific types of heat exchangers and can only be used at constant coolant temperatures. The purpose of this study is to obtain expressions for determining the effect of coolant flow rates on the variable heat exchanger parameter. Materials and methods. The main variable operation modes for water-to-water heat exchangers used in heat supply systems are determined. Using simulation in the PTC Mathcad software, dependencies describing the change in the heat exchanger parameter for all the considered variable operation modes are defined. This made it possible to obtain a general formula for the change in the heat exchanger parameter for varying coolant flow rates. Coefficients in this formula take into consideration the effect of coolant temperatures, which cannot be known when calculating variable conditions, especially when the interconnected heat exchangers are operating. Results. To test applicability of the existing relations describing the change in the heat exchanger parameter and of obtained formula, a large number of heat exchangers is calculated at variable operation modes. Comparison with the simulation results shows that the correlations of heat exchanger theories work well at the mode with constant coolant temperatures only, while their use at other operation modes can lead to large calculation errors. Conclusions. The obtained formula allows finding the effect of coolant flow rates on the variable heat exchanger parameter. The formula can be used to predict the operation modes of large systems including a large number of various-type heat exchangers.

Modeling Large-Size Boilers As a Set of Heat Exchangers: Tips and Tricks

2001 ◽  
Author(s):  
Cristóbal Cortés ◽  
Luis I. Díez ◽  
Antonio Campo
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Heat Recovery ◽  
Practical Calculation ◽  
Approximate Methods ◽  
Monitoring Method ◽  
Large Size ◽  
Thermoelectric Plant ◽  
The One

Abstract Practical calculation of the heat-recovery sections of large-size boilers is still based on approximate methods. On the one hand, CFD-based models cannot directly handle the geometric intricacy of tube bundles, and thus rely on volume-averaged source terms that demand empirical input. On the other hand, the standard, lumped heat exchanger calculation, which can be a far simpler and more robust alternative, fails in several important aspects, mainly related to the effects of thermal radiation and the coupling between several sections. In this paper, we consider the diverse sections of a coal-fired utility boiler as a case study to show how to deal with these shortcomings. Under the objective of developing a simple monitoring method, we extend the traditional heat exchanger model to take into account most of the peculiarities of boiler superheaters, reheaters and economizers. Techniques range from the re-examination of analytical solutions to the auxiliary use of CFD calculations. The models are assembled to simulate the thermal performance of the boiler as a whole unit. Results are validated against actual measurements taken at a thermoelectric plant.

Fabrication and Performance of a Pin Fin Micro Heat Exchanger

2004 ◽  
Vol 126 (3) ◽  
pp. 434-444 ◽  
Author(s):  
Christophe Marques ◽  
Kevin W. Kelly
Keyword(s):  
Heat Exchanger ◽  
Gas Turbine ◽  
Heat Exchangers ◽  
Turbine Blades ◽  
High Heat ◽  
Gas Turbine Engine ◽  
High Heat Flux ◽  
Turbine Engine ◽  
Pin Fin ◽  
Micro Heat Exchanger

Nickel micro pin fin heat exchangers can be electroplated directly onto planar or non-planar metal surfaces using a derivative of the LIGA micromachining process. These heat exchangers offer the potential to more effectively control the temperature of surfaces in high heat flux applications. Of particular interest is the temperature control of gas turbine engine components. The components in the gas turbine engine that require efficient, improved cooling schemes include the gas turbine blades, the stator vanes, the turbine disk, and the combustor liner. Efficient heating of component surfaces may also be required (i.e., surfaces near the compressor inlet to prevent deicing). In all cases, correlations providing the Nusselt number and the friction factor are needed for such micro pin fin heat exchangers. Heat transfer and pressure loss experimental results are reported for a flat parallel plate pin fin micro heat exchanger with a staggered pin fin array, with height-to-diameter ratios of 1.0, with spacing-to-diameter ratios of 2.5 and for Reynolds numbers (based on the hydraulic diameter of the channel) from 4000 to 20,000. The results are compared to studies of larger scale, but geometrically similar, pin fin heat exchangers. To motivate further research, an analytic model is described which uses the empirical results from the pin fin heat exchanger experiments to predict a cooling effectiveness exceeding 0.82 in a gas turbine blade cooling application. As a final point, the feasibility of fabricating a relatively complex micro heat exchanger on a simple airfoil (a cylinder) is demonstrated.

scholarly journals The influence of main parameters of regenerative heat exchanger on its energy efficiency

2020 ◽  
Vol 178 ◽  
pp. 01024
Author(s):  
Nikolay Monarkin ◽  
Anton Sinitsyn ◽  
Mikhail Pavlov ◽  
Timur Akhmetov
Keyword(s):  
Energy Efficiency ◽  
Heat Capacity ◽  
Heat Exchanger ◽  
Wall Thickness ◽  
Thermal Energy ◽  
Thermal Efficiency ◽  
Heat Exchangers ◽  
Regenerative Heat ◽  
Flow Through ◽  
Geometric Length

The influence of various parameters of stationary switching regenerative heat exchangers used for ventilation on its thermal efficiency was studied. Considered are the geometric (length, diameter and wall thickness of a single equivalent nozzle channel), thermophysical (density and heat capacity of the nozzle material) and operation (air flow through the regenerator and the time of one stage of accumulation/regeneration of thermal energy) parameters.

Assessment of ASME Code Examinations on Regenerative, Letdown and Residual Heat Removal Heat Exchangers

2005 ◽  
Author(s):  
S. R. Gosselin ◽  
F. A. Simonen ◽  
S. E. Cumblidge ◽  
G. A. Tinsley ◽  
B. Lydell ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Power Plants ◽  
National Laboratory ◽  
Operating Experience ◽  
Heat Removal ◽  
Pacific Northwest National Laboratory ◽  
Regenerative Heat ◽  
Asme Code ◽  
Residual Heat

Inservice inspection requirements for pressure retaining welds in the regenerative, letdown, and residual heat removal heat exchangers are prescribed in Section XI Articles IWB and IWC of the ASME Boiler and Pressure Vessel Code. Accordingly, volumetric and/or surface examinations are performed on heat exchanger shell, head, nozzle-to-head, and nozzle-to-shell welds. Inspection difficulties associated with the implementation of these Code-required examinations have forced operating nuclear power plants to seek relief from the U.S. Nuclear Regulatory Commission. The nature of these relief requests are generally concerned with metallurgical factors, geometry, accessibility, and radiation burden. Over 60% of licensee requests to the NRC identify significant radiation exposure burden as the principal reason for relief from the ASME Code examinations on regenerative heat exchangers. For the residual heat removal heat exchangers, 90% of the relief requests are associated with geometry and accessibility concerns. Pacific Northwest National Laboratory was funded by the NRC Office of Nuclear Regulatory Research to review current practice with regard to volumetric and/or surface examinations of shell welds of letdown heat exchangers, regenerative heat exchangers, and residual (decay) heat removal heat exchangers. Design, operating, common preventative maintenance practices, and potential degradation mechanisms were reviewed. A detailed survey of domestic and international PWR-specific operating experience was performed to identify pressure boundary failures (or lack of failures) in each heat exchanger type and NSSS design. The service data survey was based on the PIPExp® database and covers PWR plants worldwide for the period 1970–2004. Finally a risk assessment of the current ASME Code inspection requirements for residual heat removal, letdown, and regenerative heat exchangers was performed. The results were then reviewed to discuss the examinations relative to plant safety and occupational radiation exposures.

Calculation of the Geometrical Parameters of the Heat Exchanger Type “Pipe in Pipe” with a Spiral-Coiled Channel

2019 ◽  
Vol 16 (11) ◽  
pp. 4513-4518 ◽  
Author(s):  
Valeriya Leonidovna Vorontsova ◽  
Alfiya Gizzetdinovna Bagoutdinova ◽  
Almaz Fernandovich Galemzianov
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Characteristic Size ◽  
Geometrical Parameters ◽  
Equivalent Diameter ◽  
Annular Space ◽  
Integral Calculus ◽  
Criterial Equations ◽  
Type Tube

The designs of the modern type of twisting devices include spring-twisted channels, which to use as innovative heat exchange elements of tubular apparatuses. The paper presents a method for determining the equivalent diameter of the tube and intertubular space in a heat exchanger apparatus of the type “tube-in-tube” with a spring-twisted channel which composed of tori closely adjacent to each other. Based on the integral calculus, formulas are obtained for calculating the equivalent diameters of the tube and annular space in a tube-in-tube apparatus with a spring-twisted channel. The results of experiments on heat transfer are generalized by criterial equations, in which the equivalent diameter is used as the characteristic size. It is shown that the equivalent diameters of the examined channels differ from each other by no more than 5%. The results of this work can be used in the design and calculations of promising heat exchangers with intensified heat transfer.

Numerical Modeling of Chevron Plate Heat Exchangers for Thermal Management Applications

2016 ◽  
Author(s):  
Harsh Tamakuwala ◽  
Ryan Von Ness ◽  
Debjyoti Banerjee
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
High Heat ◽  
Plate Heat Exchanger ◽  
High Heat Flux ◽  
Plate Heat ◽  
Geometric Conditions ◽  
Swirl Flows

Plate-fin heat exchangers are widely used in industries especially aerospace, cryogenics, food and chemical process industries where high heat flux surface area per unit volume is of prime importance. These heat exchangers consists of series of corrugated plates (herringbone or chevron), separated by gasket sealing. Chevron angled plates are one of the most commonly used type of geometry. The complex design of chevron plate heat exchanger, induces high turbulence and flow reversals causing high heat transfer through the plates. This paper discusses about the computational fluid dynamics simulations conducted over a simplified geometry of Chevron Plate Heat Exchanger to understand the formulation of vortices at different Reynold’s number for various aspect ratios. A single phase laminar flow with periodic boundary condition is used for analysis of the fluid behavior in a unit pattern of the corrugation geometry. Based on different flow and geometric conditions, varying amounts of swirl-flows are observed and different behavior of shear stress and heat transfer plot along the length of the plate is observed. At higher Reynolds numbers (Re), the re-circulations and mixing by the induced vortices causes significant rise of heat flux, with marginal increase in friction factor.

Roller Profiling for Shaping Corrugated Profiles on the Heat Exchanger Tape for Wind Tunnels

2021 ◽  
pp. 16-27
Author(s):  
Yu.V. Shchipkova ◽  
A.Yu. Popov
Keyword(s):  
Plastic Deformation ◽  
Heat Exchanger ◽  
Contact Pressure ◽  
Heat Exchangers ◽  
Wind Tunnels ◽  
Regenerative Heat ◽  
Elastic Aftereffect ◽  
Study Results ◽  
Profile Correction ◽  
Profiling Techniques

The efficiency of regenerative heat exchangers with heat-accumulating nozzles made of rolled corrugated tapes depends on the profile of their corrugation. It is technologically difficult to obtain corrugations of a given shape by copying --- stamping. It is technically more expedientto form such a profile by rolling between two rollers. The contact area is smaller, and the contact pressure is significantly higher. In this case, the shape and accuracy of the tape profile are determined by the accuracy of calculation and manufacturing of the profile of the rollers. The length of the profiling zone and the contact pressure depend on the diameter of the rollers. To apply the known profiling techniques when calculating the corrugated profile of the rollers, it is necessary to find the position of the centroid. However, the difficulty is in the tape between the rollers whose thickness cannot be neglected. Therefore, the problem is solved by rolling the roller and the rail smooth, where the tape with a profile formed on it is considered as a rail. The paper introduces a technique of roller profiling taking into account the above factors. When profiling the rollers, the springing of the tape, i.e., elastic aftereffect of plastic deformation, is taken into account. The suitable diameter of the rollers has been determined. The study results in a method developed for calculating the rollers corrugation profile, taking into account the established parameters, i.e., diameters of the centroids and rollers, and the rollers teeth profile correction value, depending on the tape springing during rolling

Technical Basis for Revision of Inspection Requirements for Regenerative and Residual Heat Exchangers

2006 ◽  
Author(s):  
Warren Bamford ◽  
Bruce Bishop ◽  
Richard Haessler ◽  
Mark Bowler
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Ultrasonic Inspection ◽  
Regenerative Heat ◽  
Flaw Tolerance ◽  
Nuclear Plants ◽  
History Of ◽  
Technical Basis ◽  
Very High ◽  
Residual Heat

Section XI imposed volumetric inservice inspection requirements on heat exchangers in nuclear plants after most of this equipment was designed and installed. Consequently the equipment was not designed for ultrasonic examination, and in some cases such volumetric examination is not justified. The man-rem dose received from the ultrasonic inspection of some of these components is very high, and there are no known mechanisms of degradation; thus, the volumetric inspection serves no useful purpose. With the use of the newly approved code case, N706, volumetric and surface inspection of the regenerative and residual heat exchangers in PWR plants may be replaced with a visual inspection. These two heat exchangers have high irradiation fields, and both have a number of complicated weld geometries that are difficult to inspect. The regenerative heat exchanger provides preheat for the normal charging water going into the reactor coolant system (RCS). The residual heat exchanger is designed to cool the RCS during plant shut down operations. The technical basis for changing these inspection requirements was derived from four fundamental arguments: 1. The heat exchangers were carefully constructed to nuclear quality requirements. 2. They were inspected during construction, and then during service, and there is no history of degradation. 3. The flaw tolerance of the components is very high, since their duty cycle is mild, and they are constructed of stainless steel. 4. The risk is not significantly changed by replacement of the examinations with visual examinations. This paper will describe in detail the technical arguments under each of these topics, which together form the basis for the code case.

scholarly journals Review of Design and Modeling of Regenerative Heat Exchangers

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 759
Author(s):  
Bohuslav Kilkovský
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Fixed Bed ◽  
Packed Bed ◽  
Regenerative Heat ◽  
Adequate Accuracy ◽  
Proper Design ◽  
Bed Material ◽  
The Heat Transfer Coefficient

Heat regenerators are simple devices for heat transfer, but their proper design is rather difficult. Their design is based on differential equations that need to be solved. This is one of the reasons why these devices are not widely used. There are several methods for solving them that were developed. However, due to the time demands of calculation, these models did not spread too much. With the development of computer technology, the situation changed, and these methods are now relatively easy to apply, as the calculation does not take a lot of time. Another problem arises when selecting a suitable method for calculating the heat transfer coefficient and pressure drop. Their choice depends on the type of packed bed material, and not all available computational equations also provide adequate accuracy. This paper describes the so-called open Willmott methods and provides a basic overview of equations for calculating the regenerative heat exchanger with a fixed bed. Based on the mentioned computational equations, it is possible to create a tailor-made calculation procedure of regenerative heat exchangers. Since no software was found on the market to design regenerative heat exchangers, it had to be created. An example of software implementation is described at the end of the article. The impulse to create this article was also to broaden the awareness of regenerative heat exchangers, to provide designers with an overview of suitable calculation methods and, thus, to extend the interest and use of this type of heat exchanger.

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