Computational Fluid Dynamics Simulations of an Inertance Type Pulse Tube Refrigerator

2010 ◽  
Author(s):  
Dion Savio Antao ◽  
Bakhtier Farouk
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Heat Exchangers ◽  
Numerical Study ◽  
Working Fluid ◽  
Pulse Tube ◽  
Pulse Tube Refrigerator ◽  
Flow Recirculation ◽  
Temperature Heat

A numerical study is reported here for the investigation of the fundamental flow and heat transfer processes found in an inertance type pulse tube refrigerator (IPTR). The general design of an IPTR incorporates a pressure wave generator, a transfer line, an aftercooler, a regenerator, a pulse tube, a pair of heat exchangers for the cold and hot ends of the pulse tube, an inertance tube and a reservoir. The performance of the IPTR system is simulated using computational fluid dynamics (CFD) using cylindrical co-ordinates (r–z) and applying the axisymmetric assumption. The IPTR is driven by a cyclically moving piston at one end of the system operating at a fixed frequency with helium as the working fluid. Both constant temperature and convective heat transfer boundary conditions are examined along the external walls of the hot heat exchangers. The simulations reveal interesting steady-periodic flow patterns that develop in the pulse tube due to the fluctuations caused by the piston and the presence of the inertance tube. The secondary-flow recirculation patterns in the pulse tube reduce the heat pumping effect from the low-temperature heat exchanger to the high-temperature heat exchangers.

The Technical Derivation of Heat Transfer Performance of the Airside of a Novel Pin Design Heat Exchanger Using Computational Fluid Dynamics

2012 ◽  
Author(s):  
Tosha Churitter
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Heat Exchanger ◽  
Mass Flow ◽  
Heat Exchangers ◽  
Heat Transfer Performance ◽  
Diameter Ratio ◽  
Transfer Performance ◽  
Extended Surface

Pins are a common type of extended surface used in the field of heat transfer; their main application being in the electronics field. Historically, pins used in heat exchangers have diameters that are considered negligible in comparison to their lengths and are therefore termed as tubes. In this report, the use of pins as an extended surface is investigated for the heat transfer on the airside (cold) of the Compact Advanced Pin Surface Heat Exchanger. The pins are circular in cross section and follow a staggered arrangement. The uniqueness of the pin design is such that they cannot be treated as tubes. Key Pin Design features are as follows: • Pins have a maximum Length: Diameter ratio of 3. • Pin Spacing to Pin Diameter ratio is greater than in traditional arrangements. • Pins function as a primary as well as secondary surface. The heat transfer performance of extended surfaces possessing the above features has not been characterized, using commercially available Computational Fluid Dynamics (CFD) software, in any research specifically focused on applications for the aerospace industry. Based on actual test results, this study specially develops a unique approach that can predict the outlet temperature of the heat exchanger to within 1% accuracy. This ‘developed’ approach is applied over cold-side mass flow rates ranging from 0.05 kg/s to 0.23 kg/s, while keeping the hot side mass flow rate constant at 0.05 kg/s. At worst, the simulation results lie within 5% accuracy and at best the simulation accuracy is 1%, a significant improvement on traditional derivations. This article specifically discusses the methodology developed to analyse the heat transfer performance of the novel pin design using Fluent 6.2. It highlights the current limitations of existing equations as well as the theoretical knowledge gap that currently exists in the analysis of pins as extended heat transfer surfaces in heat exchangers.

The Effect of Fin Geometry on Design of Compact Off-Set Strip Fin High Temperature Heat Exchanger

2005 ◽  
Author(s):  
Sundaresan Subramanian ◽  
Valery Ponyavin ◽  
Clayton Ray De Losier ◽  
Yitung Chen ◽  
E. Hechanova ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Heat Exchanger ◽  
Transfer Enhancement ◽  
Heat Exchanger Design ◽  
Helium Gas ◽  
Temperature Heat ◽  
Overall Performance ◽  
Offset Strip Fin

This paper deals with the development of a three-dimensional numerical model to predict the overall performance of an advanced high temperature heat exchanger design, up to 1000°C, for the production of hydrogen by the sulfur iodine thermo-chemical cycle used in advanced nuclear reactor concepts. The design is an offset strip-fin, hybrid plate compact heat exchanger made from a liquid silicon impregnated carbon composite material. The two working fluids are helium gas and molten salt (Flinak). The offset strip-fin is chosen as a method of heat transfer enhancement due to the boundary layer restart mechanism between the fins that has a direct effect on heat transfer enhancement. The effects of the fin geometry on the flow field and heat transfer are studied in three-dimensions using Computational Fluid Dynamics (CFD) techniques. The pre-processor GAMBIT is used to create a computational mesh, and the CFD software package FLUENT that is based on the finite volume method is used to produce the numerical results. Fin dimensions need to be chosen that optimize heat transfer and minimize pressure drop. Comparison of the overall performance between two fin shapes (rectangular versus curved edges) is performed using computational fluid dynamics techniques. Fin and channel dimensions need to be chosen such as to optimize heat transfer performance and minimize pressure drop. The study is conducted with helium gas and liquid salt as the working fluids with a variety of Reynolds number values and fin dimensions. Both laminar and turbulent modeling is performed for the helium side fluid flow. The effect of the fin geometry is performed computational fluid dynamics techniques and optimization studies are performed. The model developed in this paper is used to investigate the heat exchanger design parameters in order to find an optimal design.

scholarly journals Heat Transfer Enhancement and Flow Physics Behavior of Fluid in Circular Tube with Insert

2019 ◽  
Vol 8 (3) ◽  
pp. 1708-1715
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Flow Behavior ◽  
Vortex Generator ◽  
Leading Edge ◽  
Working Fluid ◽  
Literature Study

The paper presents computational fluid dynamics study of non-conventional insert vortex generator using Commercial software, to analyze the effect of vortex generator insert on heat transfer augmentation and fluid flow behavior. The study was done for Reynolds number 10000, 15000, 25000, 35000 and 45000 with working fluid as air flowing through a tube with a constant heat flux of 1000 w/m2. Current study validates the experimental results from the literature study. The heat transfer of these inserts with various geometrical arrangements viz. pitch to projected length ratio, angle of attack and height to inner diameter ratio are investigated here with the help of computational fluid dynamics software. The physical mechanism of formation and development of vortex flow from the leading edge to trailing edge of the insert is studied and it is observed that Nusselt number increases as an increment in Reynolds number. The ratio of augmented Nusselt number to smooth tube Nusselt number is found to be decreasing with increase in Reynolds number.

Predicting the Decompression Characteristics of Carbon Dioxide Using Computational Fluid Dynamics

2012 ◽  
Author(s):  
H. E. Jie ◽  
B. P. Xu ◽  
J. X. Wen ◽  
R. Cooper ◽  
J. Barnett
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Carbon Dioxide ◽  
Computational Fluid Dynamics ◽  
Shock Tube ◽  
Pipe Wall ◽  
Numerical Study ◽  
Wall Friction ◽  
Transfer Model ◽  
Dense Phase

In a previous paper, we reported the development of CFD-DECOM, a Computational Fluid Dynamics (CFD) model based on the Arbitrary Lagrangian Eulerian (ALE) approach and the Homogeneous Equilibrium Method (HEM) for simulating multi-phase flows, to predict the transient flow following the rupture of pipelines conveying rich gas or pure carbon dioxide (CO2). The use of CFD allows the effect of pipe wall heat transfer and friction to be quantified. Here, the former is considered through the implementation of a conjugate heat transfer model while the two-phase pipe wall friction is computed using established correlations. The model was previously validated for rich gas and to a limited extent dense phase CO2 decompression against the available shock tube test data. This paper describes the extension of the model to the decompression of both gaseous and dense phase CO2 with impurities. The Peng-Robinson-Stryjek-Vera Equation Of State (EOS), which is capable of predicting the real gas thermodynamic behaviour of CO2 with impurities, has been implemented in addition to the Peng-Robinson and Span and Wagner EOSs. The liquid-vapour phase equilibrium of a multi-component fluid is determined by flash calculations. The predictions are compared with the measurements of some of the recent gaseous and dense phase CO2 shock tube tests commissioned by National Grid. The detailed comparison is presented showing reasonably good agreement with the experimental data. Further numerical study has also been carried out to investigate the effects of wall friction and heat transfer, different EOSs and impurities on the decompression behaviour.

Design Considerations for Compact Ceramic Off-Set Strip Fin High Temperature Heat Exchangers

2005 ◽  
Author(s):  
Sundaresan Subramanian ◽  
Roald Akberov ◽  
Clayton Ray DeLosier ◽  
Yitung Chen ◽  
Anthony E. Hechanova ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Temperature ◽  
Heat Exchanger ◽  
Transfer Enhancement ◽  
Heat Exchanger Design ◽  
Temperature Heat ◽  
Overall Performance ◽  
Offset Strip Fin

This paper deals with the development of a three-dimensional numerical model to predict the overall performance of an advanced high temperature heat exchanger design, up to 1000°C, for the production of hydrogen by the sulfur iodine thermo-chemical cycle used in advanced nuclear reactor concepts. The design is an offset strip-fin, hybrid plate compact heat exchanger made from a liquid silicon impregnated carbon composite material. The two working fluids are helium gas and molten salt (Flinak). The offset strip-fin is chosen as a method of heat transfer enhancement due to the boundary layer restart mechanism between the fins that has a direct effect on heat transfer enhancement. The effects of the fin geometry on the flow field and heat transfer are studied in three-dimensions using Computational Fluid Dynamics (CFD) techniques. The pre-processor GAMBIT is used to create a computational mesh, and the CFD software package FLUENT that is based on the finite volume method is used to produce the numerical results. Fin dimensions need to be chosen that optimize heat transfer and minimize pressure drop. Comparison of the overall performance between two fin shapes (rectangular versus curved edges) is performed using analytical calculations (where available) as well as computational fluid dynamics techniques. The analytical calculations predict larger pressure losses than the numerical simulations. The model developed in this paper will be used to investigate the heat exchanger design parameters in order to find an optimal design.

Thermal Performance of the U-Tube Solar Collector Using Computational Fluid Dynamics Simulation

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
Rim Farjallah ◽  
Monia Chaabane ◽  
Hatem Mhiri ◽  
Philippe Bournot ◽  
Hatem Dhaouadi
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Model ◽  
Flow Rate ◽  
Solar Collector ◽  
Numerical Study ◽  
Numerical Results ◽  
Dynamics Simulation ◽  
Working Fluid ◽  
Discrete Ordinates

In this paper, we propose a numerical study of a tubular solar collector with a U-tube. A three-dimensional numerical model is developed. It was first used in order to study the efficiency of the solar collector and to evaluate the validity of the developed computational fluid dynamics (CFD) model by comparison with experimental results from the literature. For the numerical simulations, the turbulence and the radiation were, respectively, modeled using the standard k–ε model and the discrete ordinates (DO) model. This numerical model was then used to carry out a parametrical study and to discuss the effect of selected operating parameters such as the fluid mass flow rate, the absorber selectivity, and the material properties. Numerical results show that with the increase of the working fluid flow rate from 0.001 kg/s to 0.003 kg/s, the efficiency of the solar collector is improved (from 30% to 35%). Numerical results also show that the filled-type evacuated tube with graphite presents a best result in comparison with those found using the copper fin tube (η increases from 54% to 64%). Finally, we noted that the use of a high selective absorber surface adds to better performance in comparison with the black absorber tube. This is mainly due to the radiation losses reduction.

scholarly journals A Review on Triple Tube Heat Exchanger on Optimizing Thermal Efficiency

2020 ◽  
Vol 6 (12) ◽  
Author(s):  
Mr Suryakant ◽  
Shravan Vishwakarma ◽  
Jitendra Mishra
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Tube Heat Exchanger ◽  
The Past ◽  
Technological Developments ◽  
Working Principle ◽  
Pipe Heat

Over the past few decades, technological developments have faced challenges in meeting cooling needs. Further work is underway on optimal heat transfer in concentric heat exchangers; one of the double tube heat exchangers examined is the triple tube heat exchanger (TTHE). Three-pipe heat exchangers were found to be more efficient than two-pipe heat exchangers. This review presented is the working principle of the triple concentric tube heat exchanger and the proposed methodology is used in a computational fluid dynamics algorithm.  

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