Limitations of Additive Manufacturing on Microfluidic Heat Exchanger Components

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Yenny Rua ◽  
Russell Muren ◽  
Shanon Reckinger
Keyword(s):  
Plastic Deformation ◽  
Natural Convection ◽  
Additive Manufacturing ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Structural Integrity ◽  
Microfluidic Channel ◽  
Microfluidic Channels ◽  
And Performance

This work describes the testing of microfluidic components created using additive manufacturing. An Objet Eden 250 was used to create microfluidic channel test coupons with passages ranging from 0.5 to 3.0 mm and wall thicknesses ranging from 0.032 to 0.5 mm. Coupons were cleaned and tested under flow to examine structural integrity. Microfluidic channels with wall thicknesses down to 0.032 mm could be printed, cleaned, and tested successfully, although plastic deformation was observed in coupons with wall thicknesses below 0.1 mm. Given these limits, additive manufacturing based microfluidic heat exchangers (HXs) offer cost and performance benefits in natural convection HX applications.

scholarly journals Design, additive manufacturing, and performance of heat exchanger with a novel flow-path architecture

2020 ◽  
Vol 180 ◽  
pp. 115775 ◽  
Author(s):  
Adrian S. Sabau ◽  
Adrian Bejan ◽  
David Brownell ◽  
Kyle Gluesenkamp ◽  
Bart Murphy ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Heat Exchanger ◽  
Flow Path ◽  
And Performance

Transient Natural Convection Heat Transfer Correlations for Tube Bundles Immersed in a Thermal Storage

2005 ◽  
Vol 129 (2) ◽  
pp. 210-214 ◽  
Author(s):  
Yan Su ◽  
Jane H. Davidson
Keyword(s):  
Nusselt Number ◽  
Natural Convection ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Tube Bundle ◽  
Single Tube ◽  
Tube Heat Exchanger ◽  
Storage Vessel ◽  
Transient Natural Convection ◽  
Nusselt Numbers

A scale analysis of the transient discharge of a fully mixed thermal storage vessel with an immersed single-tube heat exchanger is extended to provide a generalized expression for the transient natural convection Nusselt number for heat exchangers comprising many tubes. The transient Nusselt number is expressed in terms of the Rayleigh number at the initiation of the discharge (or charge) process and easily measured geometric parameters. Nusselt numbers measured for a 240-tube heat exchanger immersed in a fully mixed 126L storage vessel are well correlated in the proposed form. The applicability of the approach to thermally stratified storage fluids is evaluated for both a single-tube and the 240-tube bundle. For heat exchangers of practical size for solar systems, for example the 240-tube bundle, buoyancy driven flow within the storage is sufficient to mix an initially stratified fluid. In this case, Nusselt numbers during the discharge process are predicted accurately by the proposed transient formulation. However, if the storage fluid remains stratified during discharge, as is the case for an initially stratified vessel with a single-tube heat exchanger, the transient formulation is not recommended.

The Correlation of Heat Transfer Coefficients for the Laminar Natural Convection in a Circular Finned-Tube Heat Exchanger

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Hie Chan Kang ◽  
Se-Myong Chang
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Nusselt Number ◽  
Natural Convection ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Finned Tube ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Laminar Natural Convection

This study proposes an empirical correlation for laminar natural convection applicable to external circular finned-tube heat exchangers with wide range of configuration parameters. The transient temperature response of the heat exchangers was used to obtain the heat transfer coefficient, and the experimental data with their characteristic lengths are discussed. The data lie in the range from 1 to 1000 for Rayleigh numbers based on the fin spacing: the ratio of fin height to tube diameter ranges from 0.1 to 0.9, and the ratio of fin pitch to height ranges from 0.13 to 2.6. Sixteen sets of finned-tube electroplated with nickel–chrome were tested. The convective heat transfer coefficients on the heat exchangers were measured by elimination of the thermal radiation effect from the heat exchanger surfaces. The Nusselt number was correlated with a newly suggested composite curve formula, which converges to the quarter power of the Rayleigh number for a single cylinder case. The proposed characteristic length for the Rayleigh number is the fin pitch while that for the Nusselt number is mean flow length, defined as half the perimeter of the mean radial position inside the flow region bounded by the tube surface and two adjacent fins. The flow is regarded as laminar, which covers heat exchangers from a single horizontal cylinder to infinite parallel disks. Consequently, the result of curve fitting for the experimental data shows the reasonable physical interpretation as well as the good quantitative agreement with the correction factors.

Development of a Plate Heat Exchanger for High-Temperature and High-Pressure

2013 ◽  
Author(s):  
Kiyoshi Ishihama ◽  
Seiichi Matsumura ◽  
Takahisa Funabiki ◽  
Yukiko Kushima ◽  
Junichi Nakamura ◽  
...  
Keyword(s):  
High Pressure ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Heat Removal ◽  
Plate Heat Exchanger ◽  
Plate Heat ◽  
Thermal Transients ◽  
Higher Temperature ◽  
Water Reactors ◽  
And Performance

A gasketed plate heat exchanger that has a seal pressure of 6.5 MPa or more has been developed. This heat exchanger can be applied to heat exchangers (design temperature: 182°C, design pressure: 3.43 MPa) for the residual heat removal (RHR) systems of boiling water reactors (BWR). Practical use of gasketed plate heat exchangers under the condition of higher temperature and higher pressure has been achieved by developing a high-pressure-retaining plate and frame, as well as a heat- and radiation-resistant gasket. Various element tests related to strength and performance were conducted in the process of this development. A verification test using a prototype heat exchanger was also conducted, and pressure resistance, heat resistance, radiation resistance, endurance against thermal transients, and heat transfer performance have been confirmed. As a result of this development, gasketed plate heat exchangers can be applied for use under the condition of higher temperature and higher pressure, and various effects such as lower system flow, smaller footprint, easier maintenance, and lower cost for weld inspection are expected, compared to conventional shell & tube heat exchangers.

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

High Temperature Heat Exchangers (HTHX) for Nuclear Applications

2006 ◽  
Author(s):  
James C. Govern ◽  
Cila V. Herman ◽  
Dennis C. Nagle
Keyword(s):  
High Temperature ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Operating Conditions ◽  
Heat Exchanger Design ◽  
Performance Requirements ◽  
Starting Point ◽  
Temperature Heat ◽  
And Performance ◽  
Design Challenges

Many nuclear engineering applications, current and future, require heat exchangers operating at high temperatures. The operating conditions and performance requirements of these heat exchangers present special design challenges. This paper considers these challenges with respect to a simple heat exchanger design manufactured of a novel carbon material. Heat transfer and effectiveness calculations are performed for several parametric studies regarding heat exchanger parameters. These results are used to better understand the design challenges of high temperature heat exchangers as well as provide a starting point for future optimization work on more complex heat exchanger designs.

Simulation of Effective Plume-Chimney Above Natural Draft Air-Cooled Heat Exchangers

2017 ◽  
Author(s):  
Christopher Chi-Ming Chu ◽  
Robert Hieng Yik Tie ◽  
Md. Mizanur Rahman
Keyword(s):  
Natural Convection ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Industrial Scale ◽  
Test Rig ◽  
Face Area ◽  
Scale Test ◽  
Forced Draft ◽  
Air Cooled Heat Exchanger

Effective Plume-Chimney Height (EPCH) was a factor engineers used to design and analyse the performance of natural convection in air-cooled heat exchangers particularly in the event of power outage. To date the number of papers in the open literature presenting data on natural convection performance of air-cooled heat exchangers is scarce. The aim of this study is to corroborate the experimental results and theoretical predictions of Effective Plume-Chimney Height (EPCH) using Computational Fluid Dynamics (CFD) in a laboratory-scale air cooled heat exchanger of 457mm × 457mm face area and an industrial-scale test rig of 2.4m × 6.0m face area forced draft air-cooled heat exchanger comprising of a bundle with 4 rows of annular finned tubes in staggered formation operating under natural convection. The CFD software Phoenics 2015 was employed to simulate the electrically-heated air-cooled heat exchanger fitted with a top screen which was built to study the aerodynamics of natural convection of air-cooled heat exchangers. The CFD geometry arrangement and dimensions were schematic in nature, where errors introduced were considered reasonably negligible. The laboratory-scale exchanger model experimental pressure drop data was found to have an insignificant effective plume-chimney height, as predicted by a theoretical equation. It was found that EPCH values calculated from CFD results agree closely to within −0.11m and +0.06m with both experiments and the theoretical prediction, confirming the same conclusion reached in an earlier report. However, for an industrial-scale test rig (ITR) in forced draft mode of large face dimensions the EPCH had been found to be non-negligible in an earlier work. Significant values of theoretical effective plume-chimney height were inserted in the heat transfer and pressure drop simulation that appeared to yield results that agreed with the experimental heat loads. The CFD simulations on the ITR have confirmed the existence of significant effective plume-chimney heights at more than 100 percent of the bundle depth, or the chimney height. The implication is that a solid-walled chimney can appear to have an efficiency of more than 100 per cent, if cold inflow can be prevented or the penetration to the central core hindered. Since the validation of the existence of EPCH by CFD here has used only a set of data from a single source, it is worthwhile to produce more experimental data and analysis to establish the concept for better predictions of air-cooled heat exchanger natural convection performance.

Modified Manifold-Microchannel Heat Exchangers Fabricated Based on Additive Manufacturing: Experimental Characterization

2019 ◽  
Author(s):  
William C. Yameen ◽  
Nathan A. Piascik ◽  
Andrew K. Miller ◽  
Riccardo C. Clemente ◽  
Jingru Z. Benner ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Additive Manufacturing ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Flow ◽  
Heat Exchangers ◽  
Original Design ◽  
Flow Rates ◽  
Side Pressure ◽  
Manifold Microchannel

Abstract In this study, the additive manufacturing technique has been utilized to fabricate air-water heat exchangers for the application of thermoelectric power plants. Additive manufacturing is a powerful fabrication method that has enabled fabrication of complex geometries that are either challenging or impossible to fabricate based on conventional techniques. Three manifold-microchannel heat exchangers with different interior designs were fabricated by additive manufacturing and from stainless steel. The heat exchangers were tested at different air flow rates and different inlet water temperatures. One heat exchanger was designed and fabricated based on an original design of the manifold-microchannel heat exchanger. Two other heat exchangers were designed with some modifications compared to the original design. In one modified heat exchanger, cylindrical pin arrays were considered on air manifold walls in order to enhance air disturbance, and thus, increase heat transfer between water and air. The second modified heat exchanger contained same pins and also had microchannels in the perpendicular orientation compared to the original design in the outlet manifolds. This design modification was done in order to reduce air-side pressure drop in the heat exchanger. The heat transfer characteristics along with air-side pressure drop were measured and compared with the original design of the manifold-microchannel heat exchanger. Results indicated that the heat flow rate, convection heat transfer coefficient, and pressure drop did not significantly change in modified heat exchangers. For air Reynolds number between around 800 and 4,000, the heat flow rates obtained in the original heat exchanger (type A) and for 50° C water inlet temperature were between 63.9 and 228 W for the lowest and the highest air flow rates, respectively. For the same inlet water temperature, these heat flow rates were between 64.2 and 211 W for the lowest and the highest air flow rates and in one of the modified heat exchangers (type B), respectively. Similarly, while the highest air-side pressure drop in the original heat exchanger was 3458 Pa, this property was measured at 3525 (type B) and 3884 (type C) for the two modified heat exchangers.

Experimental Characterization of a Natural Convection Heat Exchanger for Solar Domestic Hot Water Systems

Solar Energy ◽  
2006 ◽  
Author(s):  
Cynthia A. Cruickshank ◽  
Stephen J. Harrison
Keyword(s):  
Natural Convection ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Computational Models ◽  
Operating Conditions ◽  
Hot Water ◽  
Test Method ◽  
Convection Flow ◽  
Convection Heat ◽  
Domestic Hot Water

To predict the long-term performance of solar domestic hot water (SDHW) systems requires computational models that can characterize the systems under a range of operating conditions. The development of detailed fundamental models that suitably describe the operation of systems with natural convection heat exchangers is, however, difficult and time consuming. The fact that the natural convection flow through the heat exchanger is intrinsically self-controlling and temperature dependent complicates the analysis. One approach to modeling this type of system is to use performance characteristics, empirically derived from experimental data, to predict the performance of the heat exchanger under typical operating conditions. Unfortunately, a significant number of tests may be required to characterize the full operation of the device. This paper presents a simplified test method that was developed to allow pre-configured SDHW systems that use natural convection heat exchangers, to be characterized. The results of this test method produce performance coefficients for simple empirical expressions that describe the fluid flow and heat transfer in the heat-exchange loop. These empirically derived coefficients are an input to a general simulation routine that allows overall system performance to be determined for various loads and climatic conditions. In this paper, data is presented for a typical heat exchanger under a range of operational conditions.

Selecting Optimum Plate Heat Exchanger Surface Patterns

1986 ◽  
Vol 108 (1) ◽  
pp. 153-160 ◽  
Author(s):  
W. W. Focke
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Plate Heat Exchanger ◽  
Plate Heat ◽  
Design Flexibility ◽  
Dimensionless Groups ◽  
Inclination Angles ◽  
Surface Patterns ◽  
And Performance

With appropriate simplifications, plate heat exchanger dimensions and performance can be described by suitable combinations of the base dimensionless groups: Colburn j factor, friction factor, and Reynolds number. Such combinations are used to construct graphic methods for finding optimum geometries (patterns that minimize the surface area required for heat transfer) subject to various constraints. It was found that the number of potentially optimum geometries increased with increasing number of constraints. In plate heat exchangers, the heat transfer performance is related to the pumping power expended. Therefore, in modular plate heat exchangers, the fixed plate lengths limit design flexibility in that heat transfer and pressure drop cannot be varied independently. This limitation can be partly overcome by using interchangeable chevron-type plates of different corrugation inclination angles in the same plate pack.

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