Microturbine Recuperation: Turbulators and Their Effect on Power Density and Thermal Efficiency

2012 ◽  
Author(s):  
Kaylee M. Dorman ◽  
Sergio Arias Quintero ◽  
Lucky V. Tran ◽  
Mark Ricklick ◽  
J. S. Kapat
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Power Density ◽  
Thermal Efficiency ◽  
High Reliability ◽  
Negative Effects ◽  
Reduced Pressure ◽  
Pressure Losses ◽  
Surface Areas ◽  
Compact Size

Microturbines have proven to be a vital part of the distributed power generation field due to their low emissions, compact size, high reliability and low maintenance. However, microturbines operate at low pressure ratios and relatively low turbine inlet temperatures that limit cycle efficiency. In order to overcome these limitations, microturbines often utilize a recuperator or regenerator to achieve the optimal balance between improved heat rates and reduced pressure ratios across the turbine. Recuperator design aims to achieve maximum effectiveness while staying reasonably compact, which creates the need to study novel heat transfer surfaces for compact heat exchanger application. In this study, experimental data of heat transfer augmentation and friction factor augmentation values for various turbulator geometries is used to determine the required heat exchanger volume to achieve 85%, 90%, and 95% effectiveness. A parametric analysis of various recuperator channel surface areas and turbulator geometry data will be utilized to determine the feasibility of increasing thermal efficiency while remaining compact to avoid large, negative effects on power density for a hypothetical gas turbine modeled after the Turbine Technologies, Ltd. SR-30 Turbo-Jet Engine. The turbulators considered in this study consist of 4 wedges, 4 ribs, and a dimpled geometry. The results will highlight the applicability of surface features in recuperator designs that can improve overall efficiency for microturbines. Results present the power density, thermal efficiency, and specific fuel consumption as functions of heat exchanger channel Reynolds number for heat exchangers implementing different turbulators. It is shown that dimples at low Reynolds numbers yield 85% effectiveness with only a 8% reduction in power density and 90% effectiveness with only a 12% reduction in power density. Ribs and wedges also perform well but suffer from high pressure losses due to their obtrusive design.

Shellside Waterflow Pressure Drop Distribution Measurements in an Industrial-Sized Test Heat Exchanger

1988 ◽  
Vol 110 (1) ◽  
pp. 60-67 ◽  
Author(s):  
H. Halle ◽  
J. M. Chenoweth ◽  
M. W. Wambsganss
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Operating Cost ◽  
Power Requirement ◽  
Pressure Drops ◽  
Pressure Losses ◽  
Finned Tubes ◽  
Heat Exchanger Design ◽  
Isothermal Water

Throughout the life of a heat exchanger, a significant part of the operating cost arises from pumping the heat transfer fluids through and past the tubes. The pumping power requirement is continuous and depends directly upon the magnitude of the pressure losses. Thus, in order to select an optimum heat exchanger design, it is is as important to be able to predict pressure drop accurately as it is to predict heat transfer. This paper presents experimental measurements of the shellside pressure drop for 24 different segmentally baffled bundle configurations in a 0.6-m (24-in.) diameter by 3.7-m (12-ft) long shell with single inlet and outlet nozzles. Both plain and finned tubes, nominally 19-mm (0.75-in.) outside diameter, were arranged on equilateral triangular, square, rotated triangular, and rotated square tube layouts with a tube pitch-to-diameter ratio of 1.25. Isothermal water tests for a range of Reynolds numbers from 7000 to 100,000 were run to measure overall as well as incremental pressure drops across sections of the exchanger. The experimental results are given and correlated with a pressure drop versus flowrate relationship.

Heat Transfer Characterization of a Finned-Tube Heat Exchanger (With and Without Condensation)

1990 ◽  
Vol 112 (1) ◽  
pp. 64-70 ◽  
Author(s):  
S. A. Idem ◽  
A. M. Jacobi ◽  
V. W. Goldschmidt
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Exchanger ◽  
Factor Versus ◽  
Finned Tube ◽  
Transfer Coefficients ◽  
Number Range ◽  
Tube Heat Exchanger ◽  
Pressure Losses ◽  
Finned Tube Heat Exchanger

The effects upon the performance of an air-to-water copper finned-tube crossflow heat exchanger due to condensation on the outer surface are considered. A four-tube, two-pass heat exchanger was tested over a Reynolds number range (based on hydraulic diameter) from 400 to 1500. The coil was operated both in overall parallel and overall counterflow configurations. Convective heat and mass transfer coefficients are presented as plots of Colburn j-factor versus Reynolds number. Pressure losses are, similarly, presented as plots of the friction factor versus Reynolds number. Enhancement of sensible heat transfer due to the presence of a condensate film is also considered.

Optimizing Effectiveness of Double Pipe Heat Exchanger Using Nanofluid and Different Porous Fins Arrangement

2021 ◽  
Author(s):  
Avinash Kumar ◽  
Vinay Arya ◽  
Chirodeep Bakli
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Design Parameters ◽  
Heat Transfer Characteristics ◽  
Pressure Losses ◽  
Porous Fin ◽  
Transfer Characteristics ◽  
Porous Fins ◽  
Double Pipe ◽  
Pipe Heat

Abstract A numerical study is carried out to investigate the effect of porous fins in counter-flow Double Pipe Heat Exchanger (DPHE). Four DPHE with different porous fin arrangements is simulated for varying Darcy number, fin height, and the number of fins and compared with the conventional DPHE with no porous fins. The Darcy-Brinkman-Forchheimer equation is employed to model the flow in the porous fins considering fixed Re = 100. Al2O3-H2O nanofluid and water are used as hot and cold fluids respectively. Stainless steel is used as porous material with a porosity of 0.65. Results are evaluated in terms of effectiveness and Performance Evaluation Criterion (PEC). The effectiveness of the heat exchanger is used to analyze the heat transfer characteristics whereas the PEC is used to analyze the heat transfer characteristics considering pressure losses also. We evaluated maximum enhancement in thermal performance using effectiveness analysis and through PEC study we evaluated optimal effectiveness and corresponding design parameters. It is shown that utilizing porous fins in DPHE enhances the heat transfer by 134.3%. However, along with enhancement in heat transfer, the pressure losses also enhance which makes the application of porous fin non-viable. Therefore, using the PEC study we obtained optimal design parameters (Da = 10−3, hf = 4 cm, and n = 30) which adapts porous fin viable with enhancement in heat transfer by 66.38%.

Numerical Modeling of Conjugate Heat Transfer on Complex Geometries With Diagonal Cartesian Method, Part II: Applications

1999 ◽  
Vol 121 (2) ◽  
pp. 261-267 ◽  
Author(s):  
K. D. Carlson ◽  
W. L. Lin ◽  
C.-J. Chen
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Conjugate Heat Transfer ◽  
Complex Geometries ◽  
Compact Heat Exchanger ◽  
Temperature Analysis ◽  
Heat Transfer Characteristics ◽  
Reduced Pressure ◽  
Diagonal Cartesian Method

Part I of this study discusses the diagonal Cartesian method for temperature analysis. The application of this method to the analysis of flow and conjugate heat transfer in a compact heat exchanger is given in Part II. In addition to a regular (i.e., Cartesian-oriented) fin arrangement, two complex fin arrangements are modeled using the diagonal Cartesian method. The pressure drop and heat transfer characteristics of the different configurations are compared. It is found that enhanced heat transfer and reduced pressure drop can be obtained with the modified fin arrangements for this compact heat exchanger.

Numerical Simulation of Manifold Microchannel Heat Exchanger

2016 ◽  
Author(s):  
Muhammad Ansab Ali ◽  
Tariq S. Khan ◽  
Ebrahim Al Hajri
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Transfer Rate ◽  
Heat Exchangers ◽  
Transfer Rate ◽  
Water Mixture ◽  
Microchannel Heat Exchanger ◽  
Compact Size

The quest to achieve higher heat transfer rate, smaller size and minimum pressure drop is a main area of focus in the design of heat exchangers. Plate heat exchangers are one of viable candidates to deliver higher heat duties but still have a drawback of higher pressure drop due to long restricted flow path. Motivated by demand of miniaturization and cost reduction, a novel design of tubular microchannel heat exchanger for single phase flow employing ammonia water mixture is proposed. Numerical simulation of unit fluid domain is conducted in ANSYS Fluent. Parametric study of the different flow geometries is evaluated in terms of Nusselt number and pressure drop. The salient features of the design include ultra-compact size with higher heat transfer rate and acceptable pressure drop.

scholarly journals Performance of Conventional and Innovative Single U-Tube Pipe Configuration in Vertical Ground Heat Exchanger (VGHE)

2021 ◽  
Vol 13 (11) ◽  
pp. 6384
Author(s):  
Adel Eswiasi ◽  
Phalguni Mukhopadhyaya
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Rate ◽  
Thermal Efficiency ◽  
Transfer Rate ◽  
Green Technology ◽  
Ground Heat Exchanger ◽  
Pump System ◽  
Heat Pump System ◽  
Vertical Ground

A ground source heat pump system (GSHP) with a ground heat exchanger (GHE) is a renewable and green technology used for heating and cooling residential and commercial buildings. An innovative U-Tube pipe configuration is suggested to enhance the heat transfer rate in the vertical ground heat exchanger (VGHE). Laboratory experiments are conducted to compare the thermal efficiency of VGHEs with two different pipe configurations: (1) an innovative U-Tube pipe configuration (single U-Tube with two outer fins) and (2) a single U-Tube. The results show that the difference between the inlet and outlet temperatures for the innovative U-Tube pipe configuration was 0.7 °C after 60 h, while it was 0.4 °C for the single U-Tube after the same amount of time. The borehole thermal resistance for the innovative U-Tube pipe configuration was 0.680 m·K/W, which is 29.22% lower than that of the single U-Tube. The heat exchange rate in the innovative U-Tube pipe configuration is increased by 57.95% compared to the conventional single U-Tube. Measured ground temperatures indicate that compared to single U-Tube pipe configuration, the innovative U-Tube pipe configuration has superior heat transfer performance. Based on the experimental results presented in this paper, it was concluded that increasing the surface area significantly by introducing external fins to the U-Tube enhances the heat transfer rate, resulting in increased thermal efficiency of the VGHE.

scholarly journals Thermal Performance of a Low-Temperature Heat Exchanger Using a Micro Heat Pipe Array

Energies ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 675 ◽  
Author(s):  
Jingang Yang ◽  
Yaohua Zhao ◽  
Aoxue Chen ◽  
Zhenhua Quan
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchange ◽  
Low Temperature ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Flue Gas ◽  
Thermal Efficiency ◽  
Heat Exchangers ◽  
Micro Heat Pipe

Domestic heat exchangers, even though widely used in industry, are not adequate for studies on low-temperature flue-gas use technologies. Despite spite their limitations, very few theoretical models have been investigated based on practical applications. Moreover, most of the existing studies on heat exchangers have focused particularly on one-dimensional and two-dimensional heat transfer models, while limited studies focus on three-dimensional ones. Therefore, this study aims at investigating the thermal performance of a low-temperature flue-gas heat recovery unit in the cold regions. Specifically, this study was conducted in the context of Changchun of Jilin Province, China, a city with the mean ambient temperature of −14 °C and mean diurnal temperature of −10 °C during winter. Experimental results showed that the thermal efficiency of the heat exchanger was higher than 60%. Through assessing the heat exchange coefficient and heat exchange efficiency of the heat exchanger, it is found that the thermal efficiency had been improved up to 0.77–0.83. Furthermore, the ICEPAK software and the standard k-ε RNG turbulence model were used to carry out simulations. The velocity and outlet temperature of fresh airflow and polluted airflow were simulated through setting different inlet temperatures of fresh air and polluted air inlet. Numerical results further indicated that the flow state was laminar flow. The micro heat pipe array side had small eddies and the heat transfer was significantly improved due to the flow of air along the surface of the micro heat pipe.

scholarly journals Review: Observation on CFD Analysis of ZnO and TiO2 Nanofluid with Oil and Ethylene Glycol in Square and Helical Coil Heat Exchanger

2021 ◽  
Vol 9 (12) ◽  
pp. 503-507
Author(s):  
Rakesh Kumar
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Helical Coil ◽  
Coiled Tube ◽  
Heat Transfer Fluids ◽  
Nano Fluid ◽  
High Heat Transfer ◽  
Compact Size ◽  
Coil Heat

Abstract: Helically coiled heat exchangers are globally used in various industrial applications for their high heat transfer performance and compact size. Nanofluids can provide the excellent thermal performance in helical coil heat exchangers. Research studies on heat transfer enhancement have gained serious momentum during recent years and have been proposed many techniques by different research groups [1]. A fluid with higher thermal conductivity has been developed to increase the efficiency of heat exchangers. The dispersion of 1-100nm sized solid nanoparticles in the traditional heat transfer fluids, termed as nanofluids, exhibit substantial higher convective heat transfer than that of traditional heat transfer fluids. Nanofluid is a heat transfer fluid which is the combination of nanoparticles and base fluid that can improve the performance of heat exchanger systems. In this present paper the efforts are made to understand that how to compare the heat transfer rate in Copper helically coiled tube and squared coiled tube heat exchanger using Zinc Oxide and Titanium Dioxide Nano fluid by studying research papers of various authors. Keywords: Helical Coil, Nano-fluid, Heat Exchanger, CFD, Pressure Drop, Temperature Distribution.

scholarly journals Design and analysis of double-pipe heat exchanger using both helical and rotating inner pipe

2021 ◽  
Vol 25 (2 Part B) ◽  
pp. 1545-1559
Author(s):  
Tarkan Koca ◽  
Aydın Citlak
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Cold Water ◽  
Straight Tube ◽  
Empirical Formulas ◽  
Pressure Losses ◽  
Annular Gap ◽  
Double Pipe

In this study, the effects of rotating straight and helical inner tubes is experimentally discussed to determine heat transfer and pressure losses in rotating tubes and improve heat transfer. The outer tube remains stationary and the inner tube is rotated at different speeds in the work. In the experiments for straight and helical tubes, the flow regime is turbulent. According to the results, Nusselt number, pressure loss, and efficiency of heat exchanger were gauged. In addition, empirical formulas were obtained for each pipe type. It is observed that as the rotation speed of the pipe increases, the heat transfer rate increases. The pipe that provides the best increase in heat transfer is the five helixes tubes. At five helixes tubes; after the number of revolutions per minute exceeds 300, the increase in heat transfer rate has almost halt. At five helixes tubes and at 300 rpm speed when the flow of cold water through the annular gap with the fluid passing through the inner tube is equal, the heat transfer increases by 124.10% compared to straight tube, 23.47% compared to two helixes tubes, 7.92% compared to three helixes tubes, and 1.65% compared to four helixes tubes. Maximum effectiveness was obtained while rotating with 300 rpm in five helixes pipes.

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