Ocean Thermal Energy Conversion Heat Exchangers: A Review of Research and Development

1985 ◽  
Vol 22 (01) ◽  
pp. 64-73
Author(s):  
Eugene H. Kinelski
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Low Cost ◽  
Cost Effective ◽  
Department Of Energy ◽  
Test Facility ◽  
Working Fluid ◽  
Ocean Energy ◽  
The U.S ◽  
Mechanical Cleaning

The goal of the OTEC heat exchanger program within the Division of Ocean Energy Systems in the U.S. Department of Energy was to develop designs, evaluate enhanced surfaces, and control biofouling using corrosion-resistant materials that were cost-effective. This report summarizes the available data on a closed-cycle OTEC power system and shows how such data could be applicable to heat exchangers used by the power industry, the U.S. Navy, and merchant ships. Ammonia was selected as the best choice for an OTEC working fluid because of its superior thermodynamics properties at the temperatures involved and its low cost. It was chosen for the advanced tests of the prototypical shell-and-tube and compact heat exchangers. The most effective biocontrol procedure for maintaining clean heat transfer surfaces in the evaporators was intermittent chlorination with possibly periodic mechanical cleaning. Preliminary, short-term test data indicated that cold seawater (at the Seacoast Test Facility at Ke-ahole Point, Hawaii) does not appear to cause fouling in condensers; however, long-term data are still needed to determine the level of biocontrol needed. Titanium and the high-alloy stainless alloys, such as AL-6X and AL-29-4C, are expected to provide the 30-year life in OTEC systems. The use of aluminum alloys is predicated upon the reduction of frequency of mechanical cleaning (to remove biofouling) that will reduce the erosion-corrosion of the heat-transfer surfaces.

Dropwise Condensation on Carbon Steel Surface

2016 ◽  
Author(s):  
Fangyu Cao ◽  
Sean Hoenig ◽  
Chien-hua Chen
Keyword(s):  
Heat Transfer ◽  
Carbon Steel ◽  
Power Plants ◽  
Heat Dissipation ◽  
Low Cost ◽  
Condensation Heat Transfer ◽  
Working Fluid ◽  
High Heat Flux ◽  
Dropwise Condensation ◽  
Two Phase

The increasing demand of heat dissipation in power plants has pushed the limits of current two-phase thermal technologies such as heat pipes and vapor chambers. One of the most obvious areas for thermal improvement is centered on the high heat flux condensers including improved evaporators, thermal interfaces, etc, with low cost materials and surface treatment. Dropwise condensation has shown the ability to increase condensation heat transfer coefficient by an order of magnitude over conventional filmwise condensation. Current dropwise condensation research is focused on Cu and other special metals, the cost of which limits its application in the scale of commercial power plants. Presented here is a general use of self-assembled monolayer coatings to promote dropwise condensation on low-cost steel-based surfaces. Together with inhibitors in the working fluid, the surface of condenser is protected by hydrophobic coating, and the condensation heat transfer is promoted on carbon steel surfaces.

Single-Phase Heat Transfer and Pressure Drop of Water Cooled Inside Horizontal Smooth Tubes in the Transitional Flow Regime

2010 ◽  
Author(s):  
Josua P. Meyer ◽  
Leon Liebenberg ◽  
Jonathan A. Olivier
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Transition Region ◽  
Heat Exchangers ◽  
Operating Conditions ◽  
Transitional Flow ◽  
Working Fluid ◽  
Tube Heat Exchanger ◽  
Smooth Tubes

Heat exchangers are usually designed in such a way that they do not operate in the transition region. This is usually due to a lack of information in this region. However, due to design constraints, energy efficiency requirements or change of operating conditions, heat exchangers are often forced to operate in this region. It is also well known that entrance disturbances influence where transition occurs. The purpose of this paper is to present experimental heat transfer and pressure drop data in the transition region for fully developed and developing flows inside smooth tubes using water as the working fluid. The use of different inlet disturbances were used to investigate its effect on transition. A tube-in-tube heat exchanger was used to perform the experiments, which ranged in Reynolds numbers from 1 000 to 20 000, with Prandtl numbers being between 4 and 6 while Grashof numbers were in the order of 105. Results showed that the type of inlet disturbance could delay transition to a Reynolds number as high as 7 000, while other inlets expedited it, confirming results of others. For heat transfer, though, it was found that transition was independent of the inlet disturbance and all commenced at the same Reynolds number, 2 000–3 000, which was attributed to secondary flow effects.

CFD Aided Design of Heat Transfer Plates for Gasketed Plate Heat Exchangers

2014 ◽  
Author(s):  
Ece Özkaya ◽  
Selin Aradag ◽  
Sadik Kakac
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Three Dimensional ◽  
Separate Flow ◽  
Working Fluid ◽  
Number Range ◽  
Plate Heat ◽  
Pressure Distributions ◽  
Cfd Analyses

In this study, three-dimensional computational fluid dynamics (CFD) analyses are performed to assess the thermal-hydraulic characteristics of a commercial Gasketed Plate Heat Exchangers (GPHEx) with 30 degrees of chevron angle (Plate1). The results of CFD analyses are compared with a computer program (ETU HEX) previously developed based on experimental results. Heat transfer plate is scanned using photogrammetric scan method to model GPHEx. CFD model is created as two separate flow zones, one for each of hot and cold domains with a virtual plate. Mass flow inlet and pressure outlet boundary conditions are applied. The working fluid is water. Temperature and pressure distributions are obtained for a Reynolds number range of 700–3400 and total temperature difference and pressure drop values are compared with ETU HEX. A new plate (Plate2) with corrugation pattern using smaller amplitude is designed and analyzed. The thermal properties are in good agreement with experimental data for the commercial plate. For the new plate, the decrease of the amplitude leads to a smaller enlargement factor which causes a low heat transfer rate while the pressure drop remains almost constant.

Development Status of Coal-Fired Gas Heaters for Brayton-Cycle Cogeneration Systems

1983 ◽  
Author(s):  
S. V. Gunn ◽  
J. R. McCarthy
Keyword(s):  
High Pressure ◽  
Heat Exchangers ◽  
Coal Combustion ◽  
Operating Experience ◽  
Department Of Energy ◽  
Test Facility ◽  
Brayton Cycle ◽  
Pulverized Coal Combustion ◽  
Development Status ◽  
Near Term

Under contract from the Department of Energy, Rocketdyne is developing the technology of coal-fired gas heaters for utilization in Brayton-cycle cogeneration systems. The program encompasses both atmospheric fluidized bed and pulverized coal combustion systems; and it is directed toward the development of gas heater systems capable of delivering high pressure air or helium at 1550 F, when employing metallic heat exchangers, and 1750 F, when employing ceramic heat exchangers. This paper reports on the development status of the program, with discussions of the completed “screening” corrosion/erosion tests of candidate heat exchanger materials, a description and summary of the operating experience with the 6- by 6-foot AFB test facility and a projection of the potential for relatively near term commercialization of such heater systems.

Design of a 6- by 6-Foot Coal-Fired Heater for a CCGT Air Heater

1982 ◽  
Author(s):  
L. H. Russell ◽  
J. Campbell
Keyword(s):  
Gas Turbine ◽  
Fluidized Bed ◽  
Atmospheric Pressure ◽  
Coal Combustion ◽  
Department Of Energy ◽  
Working Fluid ◽  
Design Rationale ◽  
Closed Cycle ◽  
Cogeneration System ◽  
The U.S

The U.S. Department of Energy is sponsoring a program of research and development on coal-fired heaters to provide heat input to the working fluid of a closed-cycle gas turbine/cogeneration system. One of the fired heater concepts being researched employs the atmospheric pressure fluidized bed coal combustion concept. This paper describes a research oriented atmospheric fluidized bed of 6- by 6-foot plan dimensions that has been designed and is being constructed for utilization during the R&D program. The design rationale is presented, details of the more significant details are described and discussed, and the planned methods for utilizing the 6- by 6-foot AFB as a research tool are presented.

Aerothermal Challenges in Syngas, Hydrogen-Fired, and Oxyfuel Turbines—Part I: Gas-Side Heat Transfer

2009 ◽  
Vol 1 (1) ◽  
Author(s):  
Minking K. Chyu ◽  
Danny W. Mazzotta ◽  
Sean C. Siw ◽  
Ventzislav G. Karaivanov ◽  
William S. Slaughter ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Natural Gas ◽  
Transfer Coefficient ◽  
Gas Turbines ◽  
Computational Simulation ◽  
Department Of Energy ◽  
Working Fluid ◽  
Computational Fluid Dynamics Analysis ◽  
The Heat Transfer Coefficient

To meet the performance goals of advanced fossil power generation systems, future coal-gas fired turbines will likely be operated at temperatures higher than those in the current commercial natural gas-fired systems. The working fluid in these future turbines could contain substantial moisture (steam), mixed with carbon dioxide, instead of air or nitrogen in conventional gas turbines. As a result, the aerothermal characteristics among the advanced turbine systems are expected to be significantly different, not only from the natural gas turbines but also will be dependent strongly on the compositions of turbine working fluids. Described in this paper is a quantitative comparison of thermal load on the external surface of turbine airfoils that are projected to be utilized in different power cycles the U.S. Department of Energy plans for the next 2 decades. The study is pursued with a computational simulation, based on the three-dimensional computational fluid dynamics analysis. While the heat transfer coefficient has shown to vary strongly along the surface of the airfoil, the projected trends were relatively comparable for airfoils in syngas and hydrogen-fired cycles. However, the heat transfer coefficient for the oxyfuel cycle is found to be substantially higher by about 50–60% than its counterparts in syngas and hydrogen turbines. This is largely caused by the high steam concentration in the turbine flow. Results gained from this study overall suggest that advances in cooling technology and thermal barrier coatings are critical for developments of future coal-based turbine technologies with near zero emissions.

Gas-Side Heat Transfer in Syngas, Hydrogen-Fired and Oxy-Fuel Turbines

2008 ◽  
Author(s):  
Danny W. Mazzotta ◽  
Ventzislav G. Karaivanov ◽  
Minking K. Chyu ◽  
William S. Slaughter ◽  
Mary Anne Alvin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Natural Gas ◽  
Transfer Coefficient ◽  
Gas Turbines ◽  
Fuel Cycle ◽  
Computational Simulation ◽  
Department Of Energy ◽  
Working Fluid ◽  
The Heat Transfer Coefficient

To meet the performance goals of advanced fossil power generation systems; e.g. FutureGen, future coal-gas fired turbines will need to be operated at temperatures higher than those in the current commercial natural gas-fired systems. The working fluid in these future turbines could contain substantial moisture (steam) mixed with carbon dioxide, instead of air or nitrogen in conventional gas turbines. As a result, the aero-thermal characteristics among these new turbines are expected to be significantly different not only from the natural gas turbines but also dependent strongly on the compositions of turbine working fluids. Described in this paper is a quantitative comparison of thermal load on the external surface of turbine airfoil present in different power cycles the US Department of Energy plans for the next decade. The study is pursued with a computational simulation based on three-dimensional computational fluid dynamics (CFD) analysis. While the heat transfer coefficient has shown to vary strongly along the surface of the airfoil, the projected trends were relatively comparable for airfoils in syngas and hydrogen-fired cycles. However, the heat transfer coefficient for the oxy-fuel cycle is found to be substantially higher, by about 50–60%, than its counterparts in syngas and hydrogen turbines. This is largely attributable to the high steam concentration in the turbine flow. This overall suggests that advances in cooling technology and thermal barrier coatings are critical for the developments of future coal-based turbine technologies with nearly zero emission.

scholarly journals Heat transfer and pressure drop evaluation of different triangular baffle placement angles in cross-corrugated triangular channels

2020 ◽  
Vol 24 (1 Part A) ◽  
pp. 355-365
Author(s):  
Koray Karabulut
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Navier Stokes ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Ansys Fluent ◽  
Number Range ◽  
Plate Heat ◽  
Corrugated Channel

Plate heat exchangers have a widespread usage and the simplest parallel plate channel structures. Cross-corrugated ducts are basic channel geometries used in the plate heat exchangers. In this study, the increasing of heat transfer from the cross-corrugated triangular ducts by inserting triangular baffles with different placement angles into the channel upper side and pressure drop have been numerically investigated. Numerical calculations have been carried out to solve Navier-Stokes and energy equations by employing k-? turbulence model as 3-D and steady with ANSYS-FLUENT program. While inlet temperature of the air used as working fluid is 293 K, constant surface temperature values of the the lower corrugated channel walls are 373 K. The height of the baffle and apex angle of the corrugated duct have been taken constant as 0.5 H and 60?, respectively. Investigated Reynolds number range is 1000-6000 while the baffle placement angles are 30?, 45?, 60?, and 90?. Numerical results of this study are within 3.53% deviation with experimental study existed in literature. The obtained results have been presented as mean Nusselt number temperature and pressure variations of the fluid for each baffle angle. The temperature and velocity vector contour distributions have been also assessed for different Reynolds numbers and baffle angles. The value of the Num for the corrugated channel with 60? baffle angle is 8.2% higher than that of the 90? for the Re = 4000. Besides, for Re = 1000 the value of the pressure drop is 39% lower in the channel with 60? baffle angle than that of 90?.

scholarly journals Investigation of heat transfer enhancement in an annular conduit with angled fins using functionalized GNP colloidal suspension

2021 ◽  
Vol 945 (1) ◽  
pp. 012058
Author(s):  
Sayshar Ram Nair ◽  
Cheen Sean Oon ◽  
Ming Kwang Tan ◽  
S.N. Kazi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Power Plants ◽  
Colloidal Suspension ◽  
Industrial Applications ◽  
Point Of View ◽  
Solid Particles ◽  
Working Fluid

Abstract Heat exchangers are important equipment with various industrial applications such as power plants, HVAC industry and chemical industries. Various fluids that are used as working fluid in the heat exchangers such as water, oil, and ethylene glycol. Researchers have conducted various studies and investigations to improve the heat exchanger be it from material or heat transfer point of view. There have been attempts to create mixtures with solid particles suspended. This invention had some drawbacks since the pressure drop was compromised, on top of the occurrence of sedimentation or even erosion, which incurs higher maintenance costs. A new class of colloidal suspension fluid that met the demands and characteristics of a heat exchanger was then created. This novel colloidal suspension mixture was then and now addressed as “nanofluid”. In this study, the usage of functionalized graphene nanoplatelet (GNP) nanofluids will be studied for its thermal conductivity within an annular conduit with angled fins, which encourage swirling flows. The simulation results for the chosen GNP nanofluid concentrations have shown an enhancement in thermal conductivity and heat transfer coefficient compared to the corresponding base fluid thermal properties. The data from this research is useful in industrial applications which involve heat exchangers with finned tubes.

Study of Heat Transfer Characteristics for the Fuel Cell System of the Humidifier due to Analysis and the Hot Testing

2011 ◽  
Author(s):  
Seon-hwa Kim ◽  
Jae-jun Lee ◽  
Young-min Oh ◽  
Sang-hoon Lee ◽  
Jae-sik Kim
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Fuel Cell ◽  
Heat Exchangers ◽  
Thermal Characteristic ◽  
Cell System ◽  
Test Facility ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Operation Temperature

The MCFC system of BOP (Balance of Plant) is contained various mechanical equipments. One of the equipments of the heat exchangers is important component for efficiency and cost. In MCFC system, several heat exchangers are used according to the application. Most typical heat exchanger is the humidifier in BOP for MCFC, which is named for the humidifier because it is to preheat the fuel and water so that a reactor will convert some of the incoming fuel to hydrogen. Then, hot side fluid service is used the exhausted gas from the fuel cell and cold side fluid service is the fuel and water. The operation temperature range is about 25∼500 Celsius Degree.[1] This heat exchanger has the problems of multiphase fluid and phase change heat transfer. So it is necessary to analyze the heat transfer characteristics and to propose the reasonable design methodology for the humidifier. In this study, the thermal characteristic for the humidifier is estimated by using commercial tool of heat exchanger design, rating and simulation. Also this study presents the results for test facility of fabrication and for testing.

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