Heat Transfer Models of Moving Packed-Bed Particle-to-SCO2 Heat Exchangers

2017 ◽  
Author(s):  
Kevin J. Albrecht ◽  
Clifford K. Ho
Keyword(s):  
Heat Transfer ◽  
Particle Size ◽  
Residence Time ◽  
Heat Exchangers ◽  
High Efficiency ◽  
Operating Temperature ◽  
Constitutive Relations ◽  
Packed Bed ◽  
Working Fluid ◽  
Trade Offs

Particle-based concentrating solar power (CSP) plants have been proposed to increase operating temperature for integration with higher efficiency power cycles using supercritical carbon dioxide (sCO2). The majority of research to date has focused on the development of high-efficiency and high-temperature particle solar thermal receivers. However, system realization will require the design of a particle/sCO2 heat exchanger as well for delivering thermal energy to the power-cycle working fluid. Recent work has identified moving packed-bed heat exchangers as low-cost alternatives to fluidized-bed heat exchangers, which require additional pumps to fluidize the particles and recuperators to capture the lost heat. However, the reduced heat transfer between the particles and the walls of moving packed-bed heat exchangers, compared to fluidized beds, causes concern with adequately sizing components to meet the thermal duty. Models of moving packed-bed heat exchangers are not currently capable of exploring the design trade-offs in particle size, operating temperature, and residence time. The present work provides a predictive numerical model based on literature correlations capable of designing moving packed-bed heat exchangers as well as investigating the effects of particle size, operating temperature, and particle velocity (residence time). Furthermore, the development of a reliable design tool for moving packed-bed heat exchangers must be validated by predicting experimental results in the operating regime of interest. An experimental system is designed to provide the data necessary for model validation and/or to identify where deficiencies or new constitutive relations are needed.

Heat Transfer Models of Moving Packed-Bed Particle-to-sCO2 Heat Exchangers

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Kevin J. Albrecht ◽  
Clifford K. Ho
Keyword(s):  
Heat Transfer ◽  
Particle Size ◽  
Residence Time ◽  
Heat Exchangers ◽  
High Efficiency ◽  
Operating Temperature ◽  
Constitutive Relations ◽  
Packed Bed ◽  
Working Fluid ◽  
Trade Offs

Particle-based concentrating solar power (CSP) plants have been proposed to increase operating temperature for integration with higher efficiency power cycles using supercritical carbon dioxide (sCO2). The majority of research to date has focused on the development of high-efficiency and high-temperature particle solar thermal receivers. However, system realization will require the design of a particle/sCO2 heat exchanger as well for delivering thermal energy to the power-cycle working fluid. Recent work has identified moving packed-bed heat exchangers as low-cost alternatives to fluidized-bed heat exchangers, which require additional pumps to fluidize the particles and recuperators to capture the lost heat. However, the reduced heat transfer between the particles and the walls of moving packed-bed heat exchangers, compared to fluidized beds, causes concern with adequately sizing components to meet the thermal duty. Models of moving packed-bed heat exchangers are not currently capable of exploring the design trade-offs in particle size, operating temperature, and residence time. The present work provides a predictive numerical model based on literature correlations capable of designing moving packed-bed heat exchangers as well as investigating the effects of particle size, operating temperature, and particle velocity (residence time). Furthermore, the development of a reliable design tool for moving packed-bed heat exchangers must be validated by predicting experimental results in the operating regime of interest. An experimental system is designed to provide the data necessary for model validation and/or to identify where deficiencies or new constitutive relations are needed.

Binary Particle Mixtures as a Heat Transfer Media in Shell-and-Plate Moving Packed Bed Heat Exchangers

2021 ◽  
Author(s):  
Chase Ellsworth Christen
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Particle Size ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Packed Bed ◽  
Particle Sizes ◽  
Overall Heat Transfer Coefficient ◽  
Solid Media

Solid particles are being considered in several high temperature thermal energy storage systems and as heat transfer media in concentrated solar power (CSP) plants. The downside of such an approach is the low overall heat transfer coefficients in shell-and-plate moving packed bed heat exchangers caused by the inherently low packed bed thermal conductivity values of the low-cost solid media. Choosing the right particle size distribution of currently available solid media can make a substantial difference in packed bed thermal conductivity, and thus, a substantial difference in the overall heat transfer coefficient of shell-and-plate moving packed bed heat exchangers. Current research exclusively focuses on continuous unimodal distributions of alumina particles. The drawback of this approach is that larger particle sizes require wider particle channels to meet flowability requirements. As a result, only small particle sizes with low packed bed thermal conductivities have been considered for the use in the falling-particle Gen3 CSP concepts. Here, binary particle mixtures, which are defined in this thesis as a mixture of two continuous unimodal particle distributions leading to a continuous bimodal particle distribution, are considered to increase packed bed thermal conductivity, decrease packed bed porosity, and improve moving packed bed heat exchanger performance. This is the first study related to CSP solid particle heat transfer that has considered the packed bed thermal conductivity and moving packed bed heat exchanger performance of bimodal particle size distributions at room and elevated temperatures. Considering binary particle mixtures that meet particle sifting segregation criteria, the overall heat transfer coefficient of shell-and-plate moving packed bed heat exchangers can be increased by 23% when compared to a monodisperse particle system. This work demonstrates that binary particle mixtures should be seriously considered to improve shell-and-plate moving packed bed heat exchangers.

Transient Analysis of the Thermal and Hydraulic Behavior of a Cooling Fluid in a Bayonet Tube

2006 ◽  
Author(s):  
J. M. Luna ◽  
S. Hernandez-Guerrero ◽  
C. Rubio-Arana ◽  
R. H. Chavez
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Heat Exchangers ◽  
Thermal Stresses ◽  
High Efficiency ◽  
Numerical Approach ◽  
Working Fluid ◽  
Nusselt Numbers ◽  
Flow Changes ◽  
Time Required

Analysis of forced convection in transient fluid flows have recently gathered attention due to the development of automatic control devices for precision control of the fluid flow in heat transfer devices of high efficiency. The precise regulation of the fluid flow is very important when the control of heat exchangers has to be assured, thus requiring a better understanding and a precise evaluation of the transient heat behavior. With few exceptions, the calculus methods for the heat exchangers devices are based on the flow patterns using considerations that could be apart from reality and restricted to stationary state conditions. These methods give little information on the possible variations due to the fluid flow changes and temperature distribution that arise due to thermal stresses. This paper deals with the details of a numerical approach to describe the transient hydrodynamic and thermal behavior in a bayonet tube with a fixed geometry using water as the working fluid. The results are reported as a function of the dimensionless Reynolds, Euler and Nusselt numbers. For each zone of the bayonet tube the time required for the fluid flow to be hydro and thermally developed is determined. The effect of the hydrodynamic flow changes on the heat flow local distribution is discussed. For a given Reynolds number a separation vortex is detected in the returning zone and it changes its position as time elapses. It is found that as time approaches the steady state the heat transfer becomes more stable throughout the bayonet.

Heat transfer enhancement of plate heat exchanger utilizing kaolin-including working fluid

2019 ◽  
Vol 233 (5) ◽  
pp. 626-634 ◽  
Author(s):  
Adnan Sözen ◽  
Ataollah Khanları ◽  
Erdem Çiftçi
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
High Efficiency ◽  
Plate Heat Exchanger ◽  
Deionized Water ◽  
Working Fluid ◽  
Improvement Rate ◽  
Plate Heat ◽  
Triton X

Plate heat exchangers having high efficiency and small size are one of the mostly used heat exchangers. They are used in many applications ranging from cooling to heating. Heat transfer improvement of plate heat exchangers can be performed using nanoparticle-including working fluids, i.e. nanofluids. Influences of kaolin-including nanofluid utilization as working fluid on heat transfer performance of the plate heat exchanger were experimentally investigated in this study. The prepared nanofluid included 2% (wt/wt) nanoparticle content and Triton X-100 surfactant was added to the prepared mixture at the rate of 0.2% of a final concentration to increase the solubility of nanoparticles. The experiments were performed in various working conditions with changes in mass flow rate and temperature. The obtained results showed that nanofluid usage as the working fluid enhanced the heat transfer rate in plate heat exchanger in comparison to the results acquired from the tests conducted by deionized water. The improvement rate in mean heat transfer coefficient was achieved as 9.3% when kaolin–deionized water nanofluid was used as the working fluid in plate heat exchanger.

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.

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.

Effect of High Coolant Velocity on Heat Transfer in Compact Heat Exchangers

2006 ◽  
Author(s):  
P. L. Sathyanarayanan ◽  
N. Venkateswaran ◽  
R. Ramprabhu
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
High Efficiency ◽  
Fluid Velocity ◽  
Small Diameter ◽  
Space Applications ◽  
Compact Heat Exchangers ◽  
Military Vehicle ◽  
Transfer Capability ◽  
Lower Fluid

Compact Heat Exchangers were developed to have very high efficiency in transfer of heat within a very small space or volume and are being used in the automotive, aircraft and space applications. In order to obtain much higher heat transfer, these Heat Exchangers uses closely packed fins, narrow or small diameter passages and turbulators or turbulence promoters. Though these arrangements result in much higher pressure drop for the fluids, this disadvantage is expected to be off-set with a larger increase in heat transfer capability. Generally it is known that turbulence enables better mixing of the fluid and results in enhancing the heat being transferred. However in practice it has been observed that there is a limit to this enhancement and the heat transfer does not improve beyond certain turbulence levels. The higher turbulence level probably results in carrying the heat away along with the fluid without transferring all the heat to the cooling medium. The presence of turbulence promoters was found to be beneficial at a lower fluid velocity level, where they conduct the heat away more by surface conduction than by convection in the fluid. Detailed experimental investigation and findings of this phenomenon using a compact heat exchanger for a military vehicle is described in this paper.

scholarly journals Multi-objective optimization of CuO based organic Rankine cycle operated using R245ca

2019 ◽  
Vol 116 ◽  
pp. 00062 ◽  
Author(s):  
Parth Prajapati ◽  
Vivek Patel
Keyword(s):  
Heat Transfer ◽  
Thermal Efficiency ◽  
Heat Exchangers ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Multi Objective Optimization ◽  
Multi Objective ◽  
Source Fluid

The present work deals with multi objective optimization of nanofluid based Organic Rankine Cycle (ORC) to utilise waste heat energy. Working fluid considered for the study is R245ca for its good thermodynamic properties and lower Global Warming Potential (GWP) compared to the conventional fluids used in the waste heat recovery system. Heat Transfer Search (HTS) algorithm is used to optimize the objective functions which tends to maximize thermal efficiency and minimize Levelised Energy Cost (LEC). To enhance heat transfer between the working fluid and source fluid, nanoparticles are added to the source fluid. Application of nanofluids in the heat transfer system helps in maximizing recovery of the waste heat in the heat exchangers. Based on the availability and cost, CuO nanoparticles are considered for the study. Effect of Pinch Point Temperature Difference (PPTD) and concentration of nanoparticles in heat exchangers is studied and discussed. Results showed that nanofluids based ORC gives maximum thermal efficiency of 18.50% at LEC of 2.59 $/kWh. Total reduction of 7.11% in LEC can be achieved using nanofluids.

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