scholarly journals Testing Platform and Commercialization Plan for Heat Exchanging Systems for SCO2 Power Cycles

2013 ◽  
Author(s):  
Darryn Fleming ◽  
Jim Pasch ◽  
Thomas Conboy ◽  
Matt Carlson
Keyword(s):  
High Pressure ◽  
Heat Exchanger ◽  
Power Plant ◽  
Temperature Difference ◽  
Heat Exchangers ◽  
Brayton Cycle ◽  
Flow Temperature ◽  
Pressure Flow ◽  
Power Cycles ◽  
Capital Costs

Supercritical Closed Brayton Cycle (SCO2 CBC) systems have the potential to convert thermal energy to electricity at an efficiency significantly higher than traditional steam Rankine cycles. The primary difference in the Brayton cycle that enables higher efficiency is the availability of a useful temperature difference between the high temperature, low pressure flow exiting the turbine, and the low temperature, high pressure flow exiting the compressor. In the SCO2 CBC cycle, this temperature difference drives heat transfer through recuperation in heat exchangers. Overall cycle energy conversion efficiency increases as the extent of recuperation increases. Ideally, the low pressure flow temperature exiting the last heat exchanger before entering the compressor will equal the high pressure flow temperature exiting the compressor. Both heat exchanger capital costs and power plant operating income rise as this ideal is approached. The capital costs are considered in relation to their effect on profit from a SCO2 CBC power plant selling electricity. Sandia is currently designing a heat exchanger test platform to support research and development of heat exchanger technology for SCO2 power cycles. This platform will facilitate investigating performance characteristics of various new heat exchanger technologies, such as pressure drop, efficiency, failure modes, etc. The platform will be able to accommodate many types of exchangers of different physical sizes and flow rates. The purpose of this testing is to identify the correct heat exchanger for the many various SCO2 applications. Testing will be a focal point of the research and commercialization plan for Sandia to identify a path forward to develop a 10MW simple recuperated Brayton cycle. The platform, once commissioned, can test many types of heat exchangers to investigate performance characteristics and to select which application they will be best suited for. Characterizing these heat exchangers will facilitate understanding how they scale. Plant economics will be a major factor in the selection of these heat exchangers. It has been identified that at this time, up to 90% of the cost of the SCO2 Brayton Cycle will be in the heat exchangers. This percentage assumes the use of printed circuit heat exchangers. Although these heat exchanger are approximately 98% efficient and a relatively high cost, the use of a lower efficiency and less costly heat exchanger may make this SCO2 technology more attractive for a path forward commercialization.

Analysis of the Thermal Stress at the Tubesheet in Floating-Head or U-Tube Heat Exchangers

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
Jiuyi Liu ◽  
Caifu Qian ◽  
Huifang Li
Keyword(s):  
Thermal Stress ◽  
Heat Exchanger ◽  
Temperature Difference ◽  
Heat Exchangers ◽  
Influence Factors ◽  
Area Ratio ◽  
Shell Side ◽  
Tube Heat Exchanger ◽  
Numerical Tests ◽  
Hole Area

Thermal stress is an important factor influencing the strength of a heat exchanger tubesheet. Some studies have indicated that, even in floating-head or U-tube heat exchangers, the thermal stress at the tubesheet is significant in magnitude. For exploring the value, distribution, and the influence factors of the thermal stress at the tubesheet of these kind heat exchangers, a tubesheet and triangle arranged tubes with the tube diameter of 25 mm were numerically analyzed. Specifically, the thermal stress at the tubesheet center is concentrated and analyzed with changing different parameters of the tubesheet, such as the temperature difference between tube-side and shell-side fluids, tubesheet diameter, thickness, and the tube-hole area ratio. It is found that the thermal stress of the tubesheet of floating-head or U-tube heat exchanger was comparable in magnitude with that produced by pressures, and the distribution of the thermal stress depends on the tube-hole area and the temperature inside the tubes. The thermal stress at the center of the tubesheet surface is high when tube-hole area ratio is very low. And with increasing the tube-hole area ratio, the stress first decreases rapidly and then increases linearly. A formula was numerically fitted for calculating the thermal stress at the tubesheet surface center which may be useful for the strength design of the tubesheet of floating-head or U-tube heat exchangers when considering the thermal stress. Numerical tests show that the fitted formula can meet the accuracy requirements for engineering applications.

Simulation and Optimization of Combined Cycle Power Cycles Through HRSG’s Heat Exchangers Arrangement and Parameters for Exergy and Cost

2012 ◽  
Author(s):  
Ravin G. Naik ◽  
Chirayu M. Shah ◽  
Arvind S. Mohite
Keyword(s):  
Power Plant ◽  
Steam Generator ◽  
Heat Exchangers ◽  
Heat Recovery ◽  
Second Law Of Thermodynamics ◽  
Combined Cycle ◽  
Heat Recovery Steam Generator ◽  
Exergetic Efficiency ◽  
Power Cycles ◽  
Combined Cycle Power Plant

To produce the power with higher overall efficiency and reasonable cost is ultimate aim for the power industries in the power deficient scenario. Though combined cycle power plant is most efficient way to produce the power in today’s world, rapidly increasing fuel prices motivates to define a strategy for cost-effective optimization of this system. The heat recovery steam generator is one of the equipment which is custom made for combined cycle power plant. So, here the particular interest is to optimize the combined power cycle performance through optimum design of heat recovery steam generator. The case of combined cycle power plant re-powered from the existing Rankine cycle based power plant is considered to be simulated and optimized. Various possible configuration and arrangements for heat recovery steam generator has been examined to produce the steam for steam turbine. Arrangement of heat exchangers of heat recovery steam generator is optimized for bottoming cycle’s power through what-if analysis. Steady state model has been developed using heat and mass balance equations for various subsystems to simulate the performance of combined power cycles. To evaluate the performance of combined power cycles and its subsystems in the view of second law of thermodynamics, exergy analysis has been performed and exergetic efficiency has been determined. Exergy concepts provide the deep insight into the losses through subsystems and actual performance. If the sole objective of optimization of heat recovery steam generator is to increase the exergetic efficiency or minimizing the exergy losses then it leads to the very high cost of power which is not acceptable. The exergo-economic analysis has been carried to find the cost flow from each subsystem involved to the combined power cycles. Thus the second law of thermodynamics combined with economics represents a very powerful tool for the systematic study and optimization of combined power cycles. Optimization studies have been carried out to evaluate the values of decision parameters of heat recovery steam generator for optimum exergetic efficiency and product cost. Genetic algorithm has been utilized for multi-objective optimization of this complex and nonlinear system. Pareto fronts generated by this study represent the set of best solutions and thus providing a support to the decision-making.

scholarly journals Study of the Performance of a Novel Radiator with Three Inlets and One Outlet Based on Topology Optimization

Micromachines ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 594
Author(s):  
Tao Zhou ◽  
Bingchao Chen ◽  
Huanling Liu
Keyword(s):  
Topology Optimization ◽  
Heat Exchanger ◽  
Temperature Difference ◽  
Heat Exchangers ◽  
Exchange Capacity ◽  
Numerical Results ◽  
Fluid Temperature ◽  
Channel Depth ◽  
Goal Model ◽  
Flow And Heat Transfer

In recent years, in order to obtain a radiator with strong heat exchange capacity, researchers have proposed a lot of heat exchangers to improve heat exchange capacity significantly. However, the cooling abilities of heat exchangers designed by traditional design methods is limited even if the geometric parameters are optimized at the same time. However, using topology optimization to design heat exchangers can overcome this design limitation. Furthermore, researchers have used topology optimization theory to designed one-to-one and many-to-many inlet and outlet heat exchangers because it can effectively increase the heat dissipation rate. In particular, it can further decrease the hot-spot temperature for many-to-many inlet and outlet heat exchangers. Therefore, this article proposes novel heat exchangers with three inlets and one outlet designed by topology optimization to decrease the fluid temperature at the outlet. Subsequently, the effect of the channel depth on the heat exchanger design is also studied. The results show that the type of exchanger varies with the channel depth, and there exists a critical depth value for obtaining the minimum substrate temperature difference. Then, the flow and heat transfer performance of the heat exchangers are numerically investigated. The numerical results show that the heat exchanger derived by topology optimization with the minimum temperature difference as the goal (Model-2) is the best design for flow and heat transfer performance compared to other heat sink designs, including the heat exchanger derived by topology optimization having the average temperature as the goal (Model-1) and conventional straight channels (Model-3). The temperature difference of Model-1 can be reduced by 37.5%, and that of Model-2 can be decreased by 62.5% compared to Model-3. Compared with Model-3, the thermal resistance of Model-1 can be reduced by 21.86%, while that of Model-2 can be decreased by 47.99%. At room temperature, we carried out the forced convention experimental test for Model-2 to measure its physical parameters (temperature, pressure drop) to verify the numerical results. The error of the average wall temperature between experimental results and simulation results is within 2.6 K, while that of the fluid temperature between the experimental and simulation results is within 1.4 K, and the maximum deviation of the measured Nu and simulated Nu was less than 5%. This indicated that the numerical results agreed well with the experimental results.

Heat Exchanger Options for Dry Air Cooling for the sCO2 Brayton Cycle

2017 ◽  
Author(s):  
Anton Moisseytsev ◽  
Qiuping Lv ◽  
James J. Sienicki
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Cost Effective ◽  
Finned Tube ◽  
Air Cooling ◽  
Brayton Cycle ◽  
Dry Air ◽  
Air Atmosphere ◽  
Air Cooler ◽  
Forced Air

The capability to utilize dry air cooling by which heat is directly rejected to the air atmosphere heat sink is one of the benefits of the supercritical carbon dioxide (sCO2) energy conversion cycle. For the selection and analysis of the heat exchanger options for dry air cooling applications for the sCO2 cycle, two leading forced air flow design approaches have been identified and analyzed for this application; an air cooler consisting of modular finned tube air coolers; and an air cooler consisting of modular compact diffusion-bonded heat exchangers. The commercially available modular finned tube air cooler is found to be more cost effective and is selected as the reference for dry air cooling.

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.

Thermal Analysis Technique for Coolers Operating in Off and Low Load Conditions

2012 ◽  
Author(s):  
Thomas J. Muldoon
Keyword(s):  
Heat Exchanger ◽  
Power Plant ◽  
Heat Exchangers ◽  
Cooling Water ◽  
Control Valve ◽  
Operating Conditions ◽  
Outlet Temperature ◽  
Inlet Valve ◽  
Plant Personnel ◽  
Load Conditions

The most conservatively designed power plant heat exchangers are designed to meet a maximum heat load with minimum fluid temperature differences. When the input temperatures are less than design maximums, the cooler will usually be in a position of over performance. This relationship is especially true when the heat exchanger is a closed Component Cooling Water (CCW) heat exchanger with inlet fluid at ambient conditions. Maintaining a consistent cooling temperature is an important concern in the operation of a power plant. It is important that the cooling needs of the equipment such as the hydrogen coolers are maintained at a set temperature. Overcooling may not be of benefit to the equipment. The component which cools the service water with the local cooling water is a component cooling water heat exchanger (CCW). The two primary methods of controlling the heat rejection performance on these vessels is to throttling the tubeside flow to get a consistent shell outlet temperature with control valves or leave the tubeside flow constant and by-pass a portion of the shellside flow. Estimating the performance of the heat exchanger with given set of inlet conditions and a fixed design point can be accomplished using a the Number Transfer Units (NTU) method. Opening and closing the control valve is based on the estimated performance. This analysis can be used by power plant personnel to gauge the operation of these vessels over varying operating conditions. The analysis can also include the effect of different values of cleanliness and the extent of throttling. As a unit experiences fouling, additional flow is required to meet the thermal requirements. Depending upon the extent of fouling, the inlet valve will be either opened or closed. Plant personnel may observe the cooling water inlet temperature and the extent to which the inlet valve is open, and use that information to determine possible fouling and setup a maintenance schedule. The following analytical approach for evaluating low, critical, or off load conditions is important in the design and operation of these types of power plant heat exchangers, piping and control valve systems.

Economic Optimization of Shell and Tube Heat Exchanger Based on Constructal Theory

2010 ◽  
Author(s):  
Majid Amidpour ◽  
Abazar Vahdat Azad
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Constructal Theory ◽  
Economic Optimization ◽  
Total Cost ◽  
Tube Heat Exchanger ◽  
Capital Costs ◽  
Operational Energy ◽  
Shell And Tube

In this paper, the new approach of Constructal theory has been employed to design shell and tube heat exchangers. Constructal theory is a new method for optimal design in engineering applications. The purpose of this paper is optimization of shell and tube heat exchangers by reduction of total cost of the exchanger using the constructal theory. The total cost of the heat exchanger is the sum of operational costs and capital costs. The overall heat transfer coefficient of the shell and tube heat exchanger is increased by the use of constructal theory. Therefore, the capital cost required for making the heat transfer surface is reduced. Moreover, the operational energy costs involving pumping in order to overcome frictional pressure loss are minimized in this method. Genetic algorithm is used to optimize the objective function which is a mathematical model for the cost of the shell and tube heat exchanger and is based on constructal theory. The results of this research represent more than 50% reduction in costs of the heat exchanger.

scholarly journals Energy and economy savings in the process of methanol synthesis unsig Pinch technology

2004 ◽  
Vol 69 (10) ◽  
pp. 827-837 ◽  
Author(s):  
Mirjana Kijevcanin ◽  
Bojan Djordjevic ◽  
Ozren Ocic ◽  
Mladen Crnomarkovic ◽  
Maja Maric ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Methanol Synthesis ◽  
Heat Exchangers ◽  
Energy Savings ◽  
Energy Costs ◽  
Pinch Analysis ◽  
Trade Off ◽  
Total Cost ◽  
Capital Costs ◽  
Pinch Technology

A heat exchanger network (HEN) for the process of methanol synthesis has been studied by pinch design analysis. Great economic and energy savings were realized by the pinch analysis in comparison to the existing plant. Also, it was found that it is possible to reduce the requirements for the consumption of utilities. The HEN was reconstruded by adding new heat exchangers. In order to produce new HEN, the capital costs had to be increased, but the total cost trade-off between the capital and energy costs will be decrease by 30 %.

Industrial Technical Development and Qualification of Highly Efficient Stainless Steel Plates and Fins Heat Exchanger for Heat Removal Supercritical CO2 Brayton Cycle Applied to Nuclear Power Plants

2020 ◽  
Author(s):  
Sarah Tioual-Demange ◽  
Gaëtan Bergin ◽  
Thierry Mazet ◽  
Luc de Camas
Keyword(s):  
Stainless Steel ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Supercritical Co2 ◽  
Nuclear Power ◽  
Power Plants ◽  
Heat Removal ◽  
Eutectic Phase ◽  
Steel Plates ◽  
Brayton Cycle

Abstract The sCO2-4-NPP european project aims to develop an innovative technology based on supercritical CO2 (sCO2) for heat removal to improve the safety of current and future nuclear power plants. The heat removal from the reactor core will be achieved with multiple highly compact self-propellant, self-launching, and self-sustaining cooling system modules, powered by a sCO2 Brayton cycle. Heat exchangers are one of the key components required for advanced Brayton cycles using supercritical CO2. Fives Cryo company, a brazed plates and fins heat exchangers manufacturer, with its expertise in thermal and hydraulic design and brazing fabrication is developing compact, and highly efficient stainless steel heat exchanger solution for sCO2 power cycles, thanks to their heat exchange capability with low pinch and high available flow sections. The aim of the development of this specific heat exchanger technology is to achieve an elevated degree of regeneration. For this matter, plates and fins heat exchanger is a very interesting solution to meet the desired thermal duty with low pressure drop leading to a reduction in size and capital cost. The enhancement of the mechanical integrity of plates and fins heat exchanger equipment would lead to compete with, and even outweigh, printed circuit heat exchangers technology, classically used for sCO2 Brayton cycles. sCO2 cycle conditions expose heat exchangers to severe conditions. Base material selection is essential, and for cost reasons, it is important to keep affordable heat-resistant austenitic stainless steel grades, much cheaper than a nickel-based alloy. Another advantage of high compactness of plates and fins heat exchangers is the diminution of the amount of material used in the heat exchanger manufacturing, decreasing even more its cost. The challenge here is to qualify stainless steel plates and fins heat exchangers mechanical resistance, at cycle operating conditions, and meet with pressure vessels codes and regulations according to nuclear requirements. One critical point in the development of the heat exchangers is the design of the fins. As secondary surface, they allow the maximization of heat transfer at low pressure drop. At the same time mechanical strength has to be guaranteed. To withstand high pressure, fins thickness has to be significant, which makes the implementation complicated. Efforts were dedicated to successfully obtain an optimal shape. Forming of fins was therefore improved compared to conventional techniques. Important work was undertaken to define industrial settings to flatten the top of the fins leading to a maximum contact between the brazing alloy and the fins. Consequently brazed joints quantity is minimized inducing a diminution of the presence of eutectic phase, which is structurally brittle and limits the mechanical strength of the construction. A metallurgical study brings other elements leading to the prevention of premature rupture of the brazed structure. The idea is to determine an optimized solidification path and to identify a temperature range and holding time where the brazed joint is almost free of eutectic phase during the assembly process in the vacuum furnace.

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