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.

scholarly journals INFLUENCE OF GEOMETRIC, THERMOPHYSICAL AND OPERATING PARAMETERS ON THERMAL EFFICIENCY OF REGENERATIVE HEAT EXCHANGER

2019 ◽  
Vol 9 (4) ◽  
pp. 33-38
Author(s):  
Nikolay N. MONARKIN ◽  
Sergey V. LUKIN ◽  
Aleksandr A. KOCHKIN
Keyword(s):  
Heat Capacity ◽  
Heat Exchanger ◽  
Wall Thickness ◽  
Thermal Efficiency ◽  
Single Channel ◽  
Air Flow ◽  
Operating Parameters ◽  
Regenerative Heat ◽  
Regenerative Heat Exchanger ◽  
One Stage

The influence of geometric (length, diameter and wall thickness of a unit equivalent channel of the nozzle), thermophysical (density and heat capacity of the nozzle material) and operating parameters (air flow through the regenerator and the time of one stage of accumulation / regeneration of thermal energy) on the thermal efficiency of stationary switching regenerative heat exchangers was studied . It was revealed that by varying the length and diameter of the channel and air flow, it is possible to increase thermal efficiency up to 10%. It was found that the wall thickness of a single channel, the density and heat capacity of the material of the nozzle, as well as the time of one stage, slightly aff ect the thermal efficiency of the regenerative heat exchanger.

scholarly journals Evaluation and Improvement of Thermal Energy of Heat Exchangers with SWCNT, GQD Nanoparticles and PCM (RT82)

2020 ◽  
Vol 79 (1) ◽  
pp. 153-168
Author(s):  
Mohammadreza Hasandust Rostami ◽  
Gholamhassan Najafi ◽  
Ali Motevalli ◽  
Nor Azwadi Che Sidik ◽  
Muhammad Arif Harun
Keyword(s):  
Energy Storage ◽  
Heat Exchanger ◽  
Heat Exchange ◽  
Phase Change ◽  
Thermal Energy ◽  
Thermal Efficiency ◽  
Heat Exchangers ◽  
Phase Change Materials ◽  
Single Wall Carbon Nanotubes ◽  
In Series

Today, due to the reduction of energy resources in the world and its pollutants, energy storage methods and increase the thermal efficiency of various systems are very important. In this research, the thermal efficiency and energy storage of two heat exchangers have been investigated in series using phase change materials (RT82) and single wall carbon nanotubes (SWCNT) and graphene quantum dot nanoparticles (GQD) In this research, two heat exchangers have been used in combination. The first heat exchanger was in charge of storing thermal energy and the second heat exchanger was in charge of heat exchange. The reason for this is to improve the heat exchange of the main exchanger (shell and tube) by using heat storage in the secondary exchanger, which has not been addressed in previous research. The results of this study showed that using two heat exchangers in series, the thermal efficiency of the system has increased. Also, the heat energy storage of the double tube heat exchanger was obtained using phase change materials in the single-walled carbon nanotube composition of about 3000 W. The average thermal efficiency of the two heat exchangers as the series has increased by 52%. In general, the effect of the two heat exchangers on each other was investigated in series with two approaches (energy storage and energy conversion) using fin and nanoparticles, which obtained convincing results.

Minimum Irreversibility Criteria for Heat Exchanger Configurations

1999 ◽  
Vol 121 (4) ◽  
pp. 241-246 ◽  
Author(s):  
F. E. M. Saboya ◽  
C. E. S. M. da Costa
Keyword(s):  
Heat Capacity ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Cross Flow ◽  
Second Law Of Thermodynamics ◽  
The Other ◽  
Maximum Heat ◽  
Transfer Rates ◽  
Mass Flow Rates ◽  
Flow Heat

From the second law of thermodynamics, the concepts of irreversibility, entropy generation, and availability are applied to counterflow, parallel-flow, and cross-flow heat exchangers. In the case of the Cross-flow configuration, there are four types of heat exchangers: I) both fluids unmixed, 2) both fluids mixed, 3) fluid of maximum heat capacity rate mixed and the other unmixed, 4) fluid of minimum heat capacity rate mixed and the other unmixed. In the analysis, the heat exchangers are assumed to have a negligible pressure drop irreversibility. The Counterflow heat exchanger is compared with the other five heat exchanger types and the comparison will indicate which one has the minimum irreversibility rate. In this comparison, only the exit temperatures and the heat transfer rates of the heat exchangers are different. The other conditions (inlet temperatures, mass flow rates, number of transfer units) and the working fluids are the same in the heat exchangers.

The Deeper the Better? A Thermogeological Analysis of Medium-deep Borehole Heat Exchanger Efficiency in Crystalline Rocks

2022 ◽  
Author(s):  
Kaiu Piipponen ◽  
Annu Martinkauppi ◽  
Sami Vallin ◽  
Teppo Arola ◽  
Nina Leppäharju ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Heat Exchanger ◽  
Thermal Energy ◽  
Heat Production ◽  
Heat Exchangers ◽  
Energy Production ◽  
Crystalline Rocks ◽  
Deep Borehole ◽  
Deep Well ◽  
Borehole Heat Exchangers

Abstract The energy sector is undergoing a fundamental transformation, with significant investment in low-carbon technologies to replace fossil-based systems. In densely populated urban areas, deep boreholes offer an alternative over shallow geothermal systems, which demand extensive surface area to attain large-scale heat production. This paper presents numerical calculations of the thermal energy that can be extracted from the medium-deep borehole heat exchangers of depths ranging from 600-3000 m. We applied the thermogeological parameters of three locations across Finland and tested two types of coaxial borehole heat exchangers to understand better the variables that affect heat production in low permeability crystalline rocks. For each depth, location, and heat collector type, we used a range of fluid flow rates to examine the correlation between thermal energy production and resulting outlet temperature. Our results indicate a trade-off between thermal energy production and outlet fluid temperature depending on the fluid flow rate, and that the vacuum-insulated tubing outperforms high-density polyethylene pipe in energy and temperature production. In addition, the results suggest that the local thermogeological factors impact heat production. Maximum energy production from a 600-m-deep well achieved 170 MWh/a, increasing to 330 MWh/a from a 1000-m-deep well, 980 MWh/a from a 2-km-deep well, and up to 1880 MWh/a from a 3-km-deep well. We demonstrate that understanding the interplay of the local geology, heat exchanger materials, and fluid circulation rates is necessary to maximize the potential of medium-deep geothermal boreholes as a reliable long-term baseload energy source.

Failure Analysis of Heat Exchangers

2021 ◽  
pp. 3-19
Author(s):  
Dusan P. Sekulic
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Failure Analysis ◽  
Thermal Energy ◽  
Solid Surface ◽  
Heat Exchangers ◽  
Heat Transfer Surface ◽  
Tubular Heat Exchanger ◽  
Erosion Corrosion ◽  
Different Temperatures

Abstract Heat exchangers are devices used to transfer thermal energy between two or more fluids, between a solid surface and a fluid, or between a solid particulate and a fluid at different temperatures. This article first addresses the causes of failures in heat exchangers. It then provides a description of heat-transfer surface area, discussing the design of the tubular heat exchanger. Next, the article discusses the processes involved in the examination of failed parts. Finally, it describes the most important types of corrosion, including uniform, galvanic, pitting, stress, and erosion corrosion.

Multipass Plate Heat Exchangers—Effectiveness-NTU Results and Guidelines for Selecting Pass Arrangements

1989 ◽  
Vol 111 (2) ◽  
pp. 300-313 ◽  
Author(s):  
S. G. Kandlikar ◽  
R. K. Shah
Keyword(s):  
Heat Capacity ◽  
Heat Exchanger ◽  
Finite Difference Method ◽  
Heat Exchangers ◽  
Rate Ratio ◽  
Plate Heat Exchanger ◽  
Tabular Form ◽  
Plate Heat ◽  
Number Of Passes ◽  
Selection Of

Plate heat exchangers are classified on the basis of number of passes on each side and the flow arrangement in each channel, taking into account the end plate effects. This results in four configurations each for the 1–1 (1 Pass–1 Pass), 2–1, 2–2, 3–3, 4–1, 4–2, and 4–4 arrangements, and six configurations for the 3–1 arrangement. These arrangements are analyzed using the Gauss–Seidel iterative finite difference method; the plate arrangement that yields the highest effectiveness in each pass configuration is identified. Comprehensive results are presented in tabular form for the temperature effectiveness P1 and log-mean temperature difference correction factor F as functions of the number of transfer units NTU1, the heat capacity rate ratio R1, and the total number of thermal plates. On the basis of these results, specific guidelines are outlined for the selection of appropriate plate heat exchanger configurations.

scholarly journals Numerical and Experimental Study of the Thermal Efficiency of an Air-Soil Heat Exchanger in the Sahelian Zone

2021 ◽  
pp. 8-16
Author(s):  
Boureima Kaboré ◽  
Germain Wende Pouiré Ouedraogo ◽  
Adama Ouedraogo ◽  
Sié Kam ◽  
Dieudonné Joseph Bathiebo
Keyword(s):  
Experimental Study ◽  
Heat Exchanger ◽  
Thermal Efficiency ◽  
Heat Exchangers ◽  
Air Conditioning ◽  
Electrical Energy ◽  
Tube Length ◽  
Air Velocity ◽  
June July ◽  
Sahelian Zone

In the Sahelian zone, air conditioning in house by air-soil heat exchangers is an alternative in the context of insufficient of electrical energy. In this work, we carried out a numerical and experimental study of thermal efficiency of an air-soil heat exchanger. This study provided an estimation of thermal efficiency of an experimental air-soil heat exchanger during June, July and August 2016. Numerical results provided a better understanding of the influence of parameters such as tube length, air velocity and soil temperature on the thermal efficiency of this system.

Effectiveness of 3-Row Crossflow Heat Exchangers With Alternating Circuitry

2003 ◽  
Author(s):  
Tony D. Chen
Keyword(s):  
Heat Capacity ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Air Conditioning ◽  
The Other ◽  
Basic Tool ◽  
Tube Heat Exchanger ◽  
Fin Tube ◽  
Comparison Of Effectiveness ◽  
Air Conditioning Systems

Air-cooled heat exchangers with three tube rows are commonly seen in domestic air-conditioning systems. The analytical solutions of heat exchanger effectiveness for three-row plate fin-and-tube heat exchangers with alternating circuitries have been derived and expressed explicitly in terms of heat capacity ratio and number of transfer units in the recent study. These set of exact solutions serve as a basic tool in designing heat exchanger circuitry to its most accurate possible effectiveness. Comparison of plate-fin-tube heat exchanger effectiveness between airside unmixed and mixed for three-row configurations shows that the effectiveness could be different from 0.3 to 2.4% for the NTUs (Number of Thermal Units) range from 1.0 to 3.0. On the other hand, the result of the comparison of effectiveness between identical and alternating circuiting for 3-row crossflow heat exchangers shows that alternating circuiting could have less effectiveness than identical circuiting from 0.4 to 8.8% in the NTUs range from 1.0 to 3.0. Nevertheless, alternating circuit has its benefit for lower NTU cases, result shows that it could have 1.7 to 0.1% advantages over identical flow arrangement for 2-row heat exchangers with NTUs range from 1.0 to 2.0.

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.

Investigation of Reverse Thermosyphoning in an Indirect SDHW System

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
Cynthia A. Cruickshank ◽  
Stephen J. Harrison
Keyword(s):  
Heat Exchanger ◽  
Thermal Energy ◽  
Heat Exchangers ◽  
Reverse Flow ◽  
Numerical Models ◽  
Storage System ◽  
Relative Magnitude ◽  
Temperature Profiles ◽  
Heating Systems ◽  
And Storage

Thermal energy storages with thermosyphon natural convection heat exchangers have been used in solar water heating systems as a means of increasing tank stratification and eliminating the need for a second circulation pump. However, if the storage system is not carefully designed, under adverse pressure conditions, reverse thermosyphoning can result in increased thermal losses from the storage and reduced thermal performance of the system. To investigate this phenomenon, tests were conducted on single tank and multitank thermal storages under controlled laboratory conditions. Energy storage rates and temperature profiles were experimentally measured during charge periods, and the effects of reverse thermosyphoning were quantified. Further objectives of this study were to empirically derive performance characteristics, to develop numerical models to predict the performance of the heat exchanger during reverse thermosyphon operation, and to quantify the relative magnitude of these effects on the energy stored during typical daylong charge periods. Results of this study show that the magnitude of the reverse flow rate depends on the pressure drop characteristics of the heat exchange loop, the system temperatures, and the geometry of the heat exchanger and storage tank. In addition, the results show that in the case of a multitank thermal storage, the carryover of energy to the downstream thermal energy storages depends on the effectiveness of the exchangers used in the system.

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