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.

Impact of an Anisotropic Fin Surface Design on the Thermal-Hydraulic Performance of a Plain-Fin-and-Tube Heat Exchanger

2011 ◽  
Author(s):  
Rong Yu ◽  
Andrew D. Sommers ◽  
Nicole C. Okamoto ◽  
Koushik Upadhyayula
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Hydraulic Performance ◽  
Normal Operation ◽  
Surface Design ◽  
Tube Heat Exchanger ◽  
Silane Coating ◽  
Side Pressure

In this study, we have explored the effectiveness of heat exchangers constructed using anisotropic, micro-patterned aluminum fins to more completely drain the condensate that forms on the heat transfer surface during normal operation with the aim of improving the thermal-hydraulic performance of the heat exchanger. This study presents and critically evaluates the efficacy of full-scale heat exchangers constructed from these micro-grooved surfaces by measuring dry/wet air-side pressure drop and dry/wet air-side heat transfer data. The new fin surface design was shown to decrease the core pressure drop of the heat exchanger during wet operation from 9.3% to 52.7%. Furthermore, these prototype fin surfaces were shown to have a negligible effect on the heat transfer coefficient under both dry and wet conditions while at the same time reducing the wet airside pressure drop thereby decreasing fan power consumption. That is to say, this novel fin surface design has shown the ability, through improved condensate management, to enhance the thermal-hydraulic performance of plain-fin-and-tube heat exchangers used in air-conditioning applications. This paper also presents data pertaining to the durability of the alkyl silane coating.

GA-Based Optimization of Compact Plate Heat Exchangers With Manifold-Microchannel Grooves

2017 ◽  
Author(s):  
Foluso Ladeinde ◽  
Kehinde Alabi ◽  
Wenhai Li
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Fitness Function ◽  
Functional Dependence ◽  
Microchannel Plate ◽  
Continuous Variables ◽  
Plate Heat ◽  
Manifold Microchannel

Manifold-microchannel combinations used on heat transfer surfaces have shown the potential for superior heat transfer performance to pressure drop ratio when compared to chevron type corrugations for plate heat exchangers (PHE) [1–4]. However, compared with heat transfer enhancements such as intermating troughs and Chevron corrugations, manifold-microchannels (MM) have several times more variables that influence the heat transfer and pressure drop characteristics, including microchannel width, depth, passes, manifold depth, width, and manifold fin thickness. Previous work has reported on the effects of some of the variables, and provides some models for their effects on thermal and hydraulic performance. The current paper presents a genetic algorithm (GA)-based procedure to analyze the implicit effects of some of the manifold-microchannel variables, and compare the performance of manifold-microchannel plate heat exchangers to those using standard Chevron corrugations. The objective of the present work is to evaluate the performance of manifold-microchannel heat transfer enhancements and demonstrate the potential for using GA-based procedure to optimize the heat exchanger. This paper also presents the modifications of the standard GA algorithm when applied to the optimization of MM. The resulting GA procedure is particularly well suited to PHEs for several reasons, including the fact that it does not require continuous variables or functional dependence on the design variables. In addition, the computational effort required for the GA technique in our implementation scales linearly, with a scaling coefficient that is significantly less than one, making it economical to analyze PHEs with several variables with degrees of freedom (DOF) with respect to the fitness function. The results of optimizing a manifold-microchannel plate heat exchanger are presented, and the exchanger’s performance is compared to more conventional PHE of the same volume utilizing chevron corrugations. Finally, results from the empirical procedure presented in this paper for a manifold-microchannel are compared with experimental measurements in Andhare [5].

Air-Side Heat Transfer Performance of Louver Fin and Multitube Heat Exchanger for Direct Methanol Fuel Cell Cooling Application

2014 ◽  
Vol 11 (4) ◽  
Author(s):  
Hie Chan Kang ◽  
Hyejung Cho ◽  
Jin Ho Kim ◽  
Anthony M. Jacobi
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Direct Methanol Fuel Cell ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Side Pressure ◽  
Direct Methanol ◽  
Methanol Fuel Cell

The present work is performed to evaluate the heat transfer performance of a heat exchanger used in a direct methanol fuel cell. Because of material constraints and performance requirements, a louver fin heat exchanger is modified for use with conventional microchannel tubes and also with multiple small-diameter tubes (called multitubes). Prototype heat exchangers are tested, and the air-side heat transfer, pressure drop, and fan power are measured in a wind tunnel and simulated using a commercial code. The air-side pressure drop and heat transfer coefficient of the multitubes show similar trends to those of the flat-tube heat exchanger if the contact resistance is negligible. The tube spacing of the prototype multitube heat exchangers has a small effect on the pressure drop and heat transfer, but it has a profound effect on the air-side heat transfer performance because of the contact resistance between the tubes and louver fins. The air-side pressure drop agrees well with an empirical correlation for flat tubes.

Performance Characterization of an Additively Manufactured Titanium (Ti64) Heat Exchanger for an Air-Water Cooling Application

2016 ◽  
Author(s):  
M. A. Arie ◽  
A. H. Shooshtari ◽  
S. V. Dessiatoun ◽  
M. M. Ohadi
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Additive Manufacturing ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Heat Exchanger Design ◽  
Performance Reduction ◽  
Manifold Microchannel ◽  
Microchannel Design

Over the last decade, rapid development of additive manufacturing techniques has allowed the fabrication of innovative designs which could not have been manufactured using conventional fabrication technologies. One field that can benefit from such technology is heat exchanger fabrication, as heat exchanger design has become more and more complex due to the demand for higher performance systems. One specific heat exchanger design that has shown significant performance enhancement potential over conventional designs and can greatly benefit from additive manufacturing technology is a manifold-microchannel heat exchanger. It is a design that combines careful fluid distribution through appropriate manifolds with an enhanced heat transfer surface design to achieve specific thermohydraulics performance expectations. Additive manufacturing allows fins as thin as 150 μm to be fabricated, which is an important enabler feature for the heat exchanger thermal performance. In addition, additive manufacturing allows the manifold and the microchannel sections to be fabricated as a single piece, which eliminates the need to fuse those sections together through a subsequent bonding process. As part of this work, we fabricated and experimentally tested a high-performance titanium alloy (Ti64) air-water heat exchanger that utilizes manifold-microchannel design. The heat exchanger was fabricated using direct metal laser sintering (DMLS) fabrication technique. The air-side implemented a manifold-microchannel design, while the water side used multiple rectangular channels in parallel. This was because the major thermal resistance occurs on the air side. The pressure drop and heat transfer performance of this heat exchanger were evaluated. The experimental results showed a noticeable performance reduction compared to the ones projected by numerical simulation due to an inaccuracy and low fidelity in printing of thin fin profile. However, despite this manufacturing inaccuracy, compared to a conventional wavy-fin surface, 15%–50% increase in heat transfer coefficient was possible for the same pressure drop value. Compared to a plain plate-fin surface, 95%–110% increase in heat transfer coefficient was possible for the same pressure drop value. The air-side heat transfer coefficient in the range of 100–450 W/m2K was achievable using manifold-microchannel technology for air-side pressure drop of 90–1800Pa. Since metal based additive manufacturing is still in the developmental stage, it is anticipated that with further refinement of the manufacturing process in future designs, the fabrication accuracy can be improved.

Comparison of Louvered Plate-Fin Heat Exchangers Made via Additive Manufacturing

2018 ◽  
Author(s):  
Michael Bichnevicius ◽  
David Saltzman ◽  
Stephen Lynch
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Additive Manufacturing ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Pressure Loss ◽  
Heat Exchanger Design ◽  
Side Pressure ◽  
Geometric Deviations ◽  
Manufacturing Techniques

Additive manufacturing (AM) can enable complex and novel designs that are otherwise infeasible with traditional metal manufacturing techniques. In low-volume production scenarios, particularly for specialized applications which can benefit from customized designs, traditional metal manufacturing techniques may be limited by costs associated with tooling. The ability to produce novel designs is particularly interesting in heat exchanger (HX) design where performance is often largely based on the achievable geometry. However, consequences of the AM process such as surface roughness, deviation from specified dimensions, and defects such as cracks and voids could also affect HX performance. These effects may vary between identically designed AM parts based on AM machine settings. The goal of this work is to gain a better understanding of the performance variations across several different implementations of the same heat exchanger design. More specifically, the objective of this work is to experimentally compare the thermal and hydraulic performances of a traditionally manufactured, stamped-aluminum aircraft oil cooler and three geometrically equivalent, additively manufactured counterparts. Compared to the traditionally manufactured heat exchanger, the AM HXs exhibited significantly higher air-side pressure loss and higher heat transfer despite having nominally similar geometries. Between AM HXs, there were slight differences in surface roughness characteristics based on optimal profilometry measurements. In addition, the thickness of the air-side fins varied as much as 15 percent between the AM HXs. The net effect, without the contribution of each cause clear, was higher air-side pressure loss and slightly higher heat transfer for the AM HX with thicker fins. This study indicates that functional heat exchangers built using AM vary in performance even when the same digital model is used to print them, and that AM HXs as a group perform considerably differently than their traditional counterparts. Thus, there is a need to account for anticipated surface roughness, geometric deviations, and potential defects when designing HXs. Proper consideration could result in improved thermal performance for future heat exchangers.

Heat Transfer Performance of Different Nanofluids Flows in a Helically Coiled Heat Exchanger

2013 ◽  
Vol 832 ◽  
pp. 160-165 ◽  
Author(s):  
Mohammad Alam Khairul ◽  
Rahman Saidur ◽  
Altab Hossain ◽  
Mohammad Abdul Alim ◽  
Islam Mohammed Mahbubul
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Friction Factor ◽  
Heat Exchangers ◽  
Heat Transfer Performance ◽  
Volume Concentration ◽  
Transfer Performance

Helically coiled heat exchangers are globally used in various industrial applications for their high heat transfer performance and compact size. Nanofluids can provide excellent thermal performance of this type of heat exchangers. In the present study, the effect of different nanofluids on the heat transfer performance in a helically coiled heat exchanger is examined. Four different types of nanofluids CuO/water, Al2O3/water, SiO2/water, and ZnO/water with volume fractions 1 vol.% to 4 vol.% was used throughout this analysis and volume flow rate was remained constant at 3 LPM. Results show that the heat transfer coefficient is high for higher particle volume concentration of CuO/water, Al2O3/water and ZnO/water nanofluids, while the values of the friction factor and pressure drop significantly increase with the increase of nanoparticle volume concentration. On the contrary, low heat transfer coefficient was found in higher concentration of SiO2/water nanofluids. The highest enhancement of heat transfer coefficient and lowest friction factor occurred for CuO/water nanofluids among the four nanofluids. However, highest friction factor and lowest heat transfer coefficient were found for SiO2/water nanofluids. The results reveal that, CuO/water nanofluids indicate significant heat transfer performance for helically coiled heat exchanger systems though this nanofluids exhibits higher pressure drop.

Performance Study of Heat Exchangers with Continuous Helical Baffles on Different Inclination Angles

2013 ◽  
Vol 655-657 ◽  
pp. 461-464 ◽  
Author(s):  
Su Fang Song
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Heat Exchangers ◽  
Performance Study ◽  
Three Dimensional Model ◽  
Shell Side ◽  
Inclination Angles

The three-dimensional model of heat exchangers with continuous helical baffles was built. The fluid flow dynamics and heat transfer of shell side in the helical baffled heat exchanger were simulated and calculated. The velocity, pressure and temperature distributions were achieved. The simulation shows that with the same baffle pitch, shell-side heat transfer coefficient increased by 25% and the pressure drop decreases by 18% in helical baffled heat exchanger compared with segmental helical baffles. With the analyzing of the flow and heat transfer in heat exchanger in 5 different inclination angles from 11°to 21°, it can be found that both shell side heat transfer coefficient and pressure drop will reduce respectively by 86% and 52% with the increases 11°to 21°of the inclination angles. Numerical simulation provided reliable theoretical reference for further engineering research of heat exchanger with helical baffles.

Analysis of Heat Exchanger Concepts for Use As Gas Turbine Intercoolers

2001 ◽  
Author(s):  
Arash Saidi ◽  
Daniel Eriksson ◽  
Bengt Sundén
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Gas Turbine ◽  
Power Output ◽  
Heat Exchangers ◽  
Advantages And Disadvantages ◽  
Volume Weight ◽  
Different Types ◽  
Core Volume

Abstract This paper presents a discussion and comparison of some heat exchanger types readily applicable to use as intercoolers in gas turbine systems. The present study concerns a heat duty of the intercooler for a gas turbine of around 17 MW power output. Four different types of air-water heat exchangers are considered. This selection is motivated because of the practical aspects of the problem. Each configuration is discussed and explained, regarding advantages and disadvantages. The available literature on the pressure drop and heat transfer correlations is used to determine the thermal-hydraulic performance of the various heat exchangers. Then a comparison of the intercooler core volume, weight, pressure drop is presented.

scholarly journals OTEC Maximum Net Power Output Using Carnot Cycle and Application to Simplify Heat Exchanger Selection

Entropy ◽  
2019 ◽  
Vol 21 (12) ◽  
pp. 1143 ◽  
Author(s):  
Kevin Fontaine ◽  
Takeshi Yasunaga ◽  
Yasuyuki Ikegami
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Power Output ◽  
Heat Exchangers ◽  
Power Plants ◽  
Seawater Temperature ◽  
Carnot Cycle ◽  
Ocean Thermal Energy ◽  
Net Power Output

Ocean thermal energy conversion (OTEC) uses the natural thermal gradient in the sea. It has been investigated to make it competitive with conventional power plants, as it has huge potential and can produce energy steadily throughout the year. This has been done mostly by focusing on improving cycle performances or central elements of OTEC, such as heat exchangers. It is difficult to choose a suitable heat exchanger for OTEC with the separate evaluations of the heat transfer coefficient and pressure drop that are usually found in the literature. Accordingly, this paper presents a method to evaluate heat exchangers for OTEC. On the basis of finite-time thermodynamics, the maximum net power output for different heat exchangers using both heat transfer performance and pressure drop was assessed and compared. This method was successfully applied to three heat exchangers. The most suitable heat exchanger was found to lead to a maximum net power output 158% higher than the output of the least suitable heat exchanger. For a difference of 3.7% in the net power output, a difference of 22% in the Reynolds numbers was found. Therefore, those numbers also play a significant role in the choice of heat exchangers as they affect the pumping power required for seawater flowing. A sensitivity analysis showed that seawater temperature does not affect the choice of heat exchangers, even though the net power output was found to decrease by up to 10% with every temperature difference drop of 1 °C.

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