scholarly journals A Numerical Study on the Energy Performance of a Novel Furnace With Acidic Gas Trap Absorbers

2020 ◽  
Author(s):  
Mingkan Zhang ◽  
Tim LaClair ◽  
Lingshi Wang ◽  
Xiaobing Liu ◽  
Zhiming Gao ◽  
...  
Keyword(s):  
Water Vapor ◽  
Heat Exchanger ◽  
Natural Gas ◽  
Liquid Water ◽  
High Efficiency ◽  
Numerical Study ◽  
Energy Performance ◽  
Cfd Model ◽  
Reactive Processing ◽  
Conventional Furnace

Abstract Natural gas furnaces are widely used in US residential and commercial building markets. An important issue for natural gas furnaces is serious corrosion and fouling problems caused by acidic gas, such as SOx. An advanced adsorption technology based on acidic gas trap (AGT) absorbers offers the possibility to remove SOx acidic gas from natural gas furnaces with high efficiency and low cost, thereby enabling the development of condensing furnaces without the use of expensive corrosion resistant materials in the heat exchanger. A three-dimensional (3D) computational fluid dynamics (CFD) model has been developed to evaluate the heat transfer performance of a furnace with AGT absorbers and to compare it with a baseline conventional furnace without the AGT. Moreover, an axisymmetric model has been built focusing on the absorbing process in the AGT. The baseline conventional furnace used for the study is a commercial condensing furnace (Rheem 92% AFUE 84,000 BTU Multi-Position Gas Furnace). This furnace was completely disassembled, and the dimensions of each part were carefully measured and used to build a detailed CFD model. A model representing the new furnace, incorporating the AGT absorbers, was developed by adding the AGT system to the conventional furnace model. For the CFD analysis, a mixture model was employed to characterize the heat and mass transfer during the condensing process in the furnace while considering three components — air, water vapor and liquid water. Condensation takes place in the condensing heat exchanger, where water vapor changes phase to liquid water, and the latent heat is thus used in the furnace for useful heating. The simulation results characterize the energy performance of both the conventional furnace and the novel furnace with AGT absorbers, as well as the reactive processing in the AGT. These results provide insightful guidance for the development of the AGT absorber-based furnace from the perspective of its energy performance and will be used to further optimize this novel furnace design.

scholarly journals High-Performance Computing to Enable Next-Generation Low-Temperature Waste Heat Recovery

2020 ◽  
Author(s):  
Vivek M. Rao ◽  
Marc-Olivier G. Delchini ◽  
Prashant K. Jain ◽  
Mohammad T. Bani Ahmad
Keyword(s):  
Heat Exchanger ◽  
Low Temperature ◽  
High Performance Computing ◽  
Liquid Water ◽  
Direct Contact ◽  
High Performance ◽  
Cfd Model ◽  
Contact Heat ◽  
Direct Contact Heat Exchanger ◽  
Performance Computing

Abstract The Oak Ridge National Laboratory (ORNL), in collaboration with Eaton Corporation, has performed computational research and development to design an innovative, direct-contact heat exchanger (DCHE) that is optimized for a low-temperature organic Rankine cycle. A computational fluid dynamics (CFD) model of DCHE was developed in STAR-CCM+ which was later calibrated and validated against the experimental data from literature. The validated CFD model was used to develop an industry-relevant liquid-liquid direct-contact heat exchanger system with water and pentane working fluids. This work heavily relied on high-performance computing (HPC) resources to investigate multiple designs and to identify a baseline design. The innovative design consists of two chambers connected by a converging-diverging nozzle. Phase change for pentane, from liquid to vapor, occurs in the first chamber, whereas the second chamber serves as a separator. Outlets in the second chamber are staggered to prevent entrainment of the liquid water by the gaseous pentane. CFD results confirm that the design behaves as expected and the addition of baffles enhances mixing and heat transfer for higher flow rates while preventing entrainment of gaseous pentane by the liquid water.

Numerical Study on Flow and Heat Transfer Performance of Natural Gas in a Printed Circuit Heat Exchanger During Trans-Critical Liquefaction

2020 ◽  
Author(s):  
Ting Ma ◽  
Pan Zhang ◽  
Jie Lian ◽  
Hanbing Ke ◽  
Wei Wang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Natural Gas ◽  
Numerical Study ◽  
Local Pressure ◽  
Local Flow ◽  
Printed Circuit ◽  
Minimum Value ◽  
Flow And Heat Transfer

Abstract The main cryogenic heat exchanger is a core piece of equipment in the liquefaction of natural gas. The printed circuit heat exchanger is gradually becoming a primary choice for the main cryogenic heat exchanger, because it has good pressure resistance, high efficiency, and compactness. In this work, a numerical simulation is conducted to examine the local flow and heat transfer characteristics of natural gas in the printed circuit heat exchanger during trans-critical liquefaction. It is found that the heat flux density reaches a minimum value and the heat transfer is the worst when the temperature difference between the hot and cold sides is the smallest. Owing to the large variations in physical properties of trans-critical natural gas, the local pressure drop exhibits an upward parabolic shape along the flow direction, and the pressure drop reaches a minimum value near the pseudo-critical point. Finally, the friction factor and heat transfer correlations for natural gas during trans-critical liquefaction are fitted.

scholarly journals Evaluation of a counter-flow microchannel heat exchanger performance with air-water vapor mixture to liquid water

2020 ◽  
Vol 194 ◽  
pp. 01025
Author(s):  
C. Ren ◽  
J.H. Weng ◽  
J.N. Yan ◽  
L. Wang ◽  
H.L. She ◽  
...  
Keyword(s):  
Water Vapor ◽  
Heat Exchanger ◽  
Liquid Water ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Vapor Mixture ◽  
Counter Flow ◽  
Microchannel Heat Exchanger ◽  
Operation Conditions ◽  
Continuum Flow

Given its configuration and operation conditions, the performance of a counter-flow microchannel heat exchanger (MCHX) is evaluated through detailed calculations. The fluids, both liquid water and air, are considered as continuum flow flowing in microchannels. The MCHX has 59 sheets, and each sheet has 48 microchannels. The microchannels for both fluids have the same cross section of 0.8mm×1mm and same length of 200mm. Log mean temperature difference method is adopted for this evaluation. Using appropriate equations, the properties of air-water vapor mixture are calculated based on that of the two components. Given the inlet temperature for liquid water(35℃) and air (170℃),the calculated outlet temperature for both fluids are 55.5℃ and 43.3℃, respectively. The results also show that the air at the outlet is saturated. The overall heat transfer coefficient reaches 100W/m2ꞏK, which is much higher than that of conventional heat exchanger with similar fluid combinations.

Advanced Zero Emissions Gas Turbine Power Plant

2003 ◽  
Author(s):  
Timothy Griffin ◽  
Sven Gunnar Sundkvist ◽  
Knut A˚sen ◽  
Tor Bruun
Keyword(s):  
Water Vapor ◽  
High Temperature ◽  
Heat Exchanger ◽  
Power Plant ◽  
Natural Gas ◽  
Gas Turbine ◽  
Exhaust Gas ◽  
Generation Process ◽  
Temperature Heat ◽  
Gas Turbine Power Plant

The AZEP (Advanced Zero Emissions Power Plant) project addresses the development of a novel “zero emissions,” gas turbine-based, power generation process to reduce local and global CO2 emissions in the most cost-effective way. Preliminary process calculations indicate that the AZEP concept will result only in a loss of 2–5% efficiency, as compared to approximately 10% loss using conventional tail-end CO2 capture methods. Additionally, the concept allows the use of air-based gas turbine equipment and thus, eliminates the need for expensive development of new turbomachinery. The key to achieving these targets is the development of an integrated MCM-reactor, in which a) O2 is separated from air by use of a mixed-conductive membrane (MCM), b) combustion of natural gas occurs in an N2-free environment and c) the heat of combustion is transferred to the oxygen depleted air by a high temperature heat exchanger. This MCM reactor replaces the combustion chamber in a standard gas turbine power plant. The cost of removing CO2 from the combustion exhaust gas is significantly reduced, since this contains only CO2 and water vapor. The initial project phase is focused on the research and development of the major components of the MCM-reactor (air separation membrane, combustor and high temperature heat exchanger), the combination of these components into an integrated reactor, and subsequent scale-up for future integration in a gas turbine. Within the AZEP process combustion is carried out in a nearly stoichiometric natural gas/O2 mixture heavily diluted in CO2 and water vapor. The influence of this high exhaust gas dilution on the stability of natural gas combustion has been investigated, using lean-premix combustion technologies. Experiments have been performed both at atmospheric and high pressures (up to 15 bar), simulating the conditions found in the AZEP process. Preliminary tests have been performed on MCM modules under simulated gas turbine conditions. Additionally, preliminary reactor designs, incorporating MCM, heat exchanger and combustor have been made, based on the results of initial component testing. Techno-economic process calculations have been performed indicating the advantages of the AZEP process as compared to other proposed CO2-free gas turbine processes.

Advanced Zero Emissions Gas Turbine Power Plant

2005 ◽  
Vol 127 (1) ◽  
pp. 81-85 ◽  
Author(s):  
Timothy Griffin ◽  
Sven Gunnar Sundkvist ◽  
Knut A˚sen ◽  
Tor Bruun
Keyword(s):  
Water Vapor ◽  
High Temperature ◽  
Heat Exchanger ◽  
Power Plant ◽  
Natural Gas ◽  
Gas Turbine ◽  
Exhaust Gas ◽  
Generation Process ◽  
Temperature Heat ◽  
Gas Turbine Power Plant

The AZEP “advanced zero emissions power plant” project addresses the development of a novel “zero emissions,” gas turbine-based, power generation process to reduce local and global CO2 emissions in the most cost-effective way. Process calculations indicate that the AZEP concept will result only in a loss of about 4% points in efficiency including the pressurization of CO2 to 100 bar, as compared to approximately 10% loss using conventional tail-end CO2 capture methods. Additionally, the concept allows the use of air-based gas turbine equipment and, thus, eliminates the need for expensive development of new turbomachinery. The key to achieving these targets is the development of an integrated MCM-reactor in which (a) O2 is separated from air by use of a mixed-conductive membrane (MCM), (b) combustion of natural gas occurs in an N2-free environment, and (c) the heat of combustion is transferred to the oxygen-depleted air by a high temperature heat exchanger. This MCM-reactor replaces the combustion chamber in a standard gas turbine power plant. The cost of removing CO2 from the combustion exhaust gas is significantly reduced, since this contains only CO2 and water vapor. The initial project phase is focused on the research and development of the major components of the MCM-reactor (air separation membrane, combustor, and high temperature heat exchanger), the combination of these components into an integrated reactor, and subsequent scale-up for future integration in a gas turbine. Within the AZEP process combustion is carried out in a nearly stoichiometric natural gas/O2 mixture heavily diluted in CO2 and water vapor. The influence of this high exhaust gas dilution on the stability of natural gas combustion has been investigated, using lean-premix combustion technologies. Experiments have been performed both at atmospheric and high pressures (up to 15 bar), simulating the conditions found in the AZEP process. Preliminary tests have been performed on MCM modules under simulated gas turbine conditions. Additionally, preliminary reactor designs, incorporating MCM, heat exchanger, and combustor, have been made, based on the results of initial component testing. Techno-economic process calculations have been performed indicating the advantages of the AZEP process as compared to other proposed CO2-free gas turbine processes.

Evaluation of Earth-Air Heat Exchangers Efficiency in Hot and Dry Climates

2013 ◽  
Vol 739 ◽  
pp. 318-324
Author(s):  
N. Oudjehani ◽  
K. Abahri ◽  
A. Tahakourt ◽  
Rafik Belarbi
Keyword(s):  
Heat Exchanger ◽  
High Efficiency ◽  
Building Energy ◽  
Energy Performance ◽  
Tube Length ◽  
Thermal Mass ◽  
Simulation Tools ◽  
Passive Strategies ◽  
Dry Climates ◽  
Air Conditioning Systems

Energy efficiency of building, promotes strongly the integration of passive strategies, in order to achieve a thermal comfort especially in summer conditions by reducing or preventing the use of air conditioning systems. In this work, building energy performance has been evaluated using an earth-air heat exchanger (EAHE) during summer period. Energy requirements was analysis by the means of dynamic simulation tools called (TRNSYS) for hot and arid climate in the southern Algeria. This analysis was conducted function of different (such as soil typology, tube material, tube length and depth, ventilation airflow rates). Results show that earth-air heat exchanger has the highest efficiency for arid climates. Furthermore, the possibility of coupling of this technology with other passive strategies (nocturne ventilation and thermal mass) has been also examined. High efficiency was observed.

scholarly journals A Numerical Study of Methods for Moist Atmospheric Flows: Compressible Equations

2014 ◽  
Vol 142 (11) ◽  
pp. 4269-4283 ◽  
Author(s):  
Max Duarte ◽  
Ann S. Almgren ◽  
Kaushik Balakrishnan ◽  
John B. Bell ◽  
David M. Romps
Keyword(s):  
Water Vapor ◽  
Phase Change ◽  
Liquid Water ◽  
Time Scale ◽  
Numerical Study ◽  
Numerical Techniques ◽  
Adjustment Procedure ◽  
Atmospheric Flows ◽  
Coupled Technique ◽  
Two Phases

Abstract Two common numerical techniques for integrating reversible moist processes in atmospheric flows are investigated in the context of solving the fully compressible Euler equations. The first is a one-step, coupled technique based on using appropriate invariant variables such that terms resulting from phase change are eliminated in the governing equations. In the second approach, which is a two-step scheme, separate transport equations for liquid water and water vapor are used, and no conversion between water vapor and liquid water is allowed in the first step, while in the second step a saturation adjustment procedure is performed that correctly allocates the water into its two phases based on the Clausius–Clapeyron formula. The numerical techniques described are first validated by comparing to a well-established benchmark problem. Particular attention is then paid to the effect of changing the time scale at which the moist variables are adjusted to the saturation requirements in two different variations of the two-step scheme. This study is motivated by the fact that when acoustic modes are integrated separately in time (neglecting phase change related phenomena), or when soundproof equations are integrated, the time scale for imposing saturation adjustment is typically much larger than the numerical one related to the acoustics.

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