Numerical and Experimental Investigations of an Orifice Type Cryogenic Pulse Tube Refrigerator

2012 ◽  
Author(s):  
Dion Savio Antao ◽  
Bakhtier Farouk
Keyword(s):  
Porous Media ◽  
Experimental Studies ◽  
Travelling Wave ◽  
Cryogenic Cooling ◽  
Experimental Results ◽  
Experimental Investigations ◽  
Pulse Tube ◽  
Pulse Tube Refrigerator ◽  
Mean Pressure ◽  
Energy Equations

A helium filled orifice type pulse tube refrigerator (OPTR) was designed, built and operated to provide cryogenic cooling. The OTPR is a travelling wave thermoacoustic refrigerator that operates on a modified reverse Stirling cycle. The experimental studies are carried out at various values of the mean pressure of helium (0.35 MPa – 2.2 MPa), amplitudes of pressure oscillations, frequencies of operation and sizes of orifice opening. The experimental results are compared with the predictions from a detailed time-dependent numerical model. In the CFD model, the compressible forms of the continuity, momentum and energy equations are solved for both the refrigerant gas (helium) and the porous media regions (the regenerator and the three heat-exchangers) in the OPTR. An improved representation of heat transfer in the porous media is achieved by employing a thermal non-equilibrium model to couple the gas and solid (porous media) energy equations. The model predictions show better comparisons with the experimental results when the effects of wall thicknesses of the various components of the OPTR are included in the model.

Experimental and Numerical Characterization of an Orifice Type Cryogenic Pulse Tube Refrigerator

2011 ◽  
Author(s):  
Dion Savio Antao ◽  
Bakhtier Farouk
Keyword(s):  
Porous Media ◽  
Heat Exchanger ◽  
Fluid Dynamic ◽  
Travelling Wave ◽  
Cryogenic Cooling ◽  
Energy Separation ◽  
Pulse Tube ◽  
Cfd Model ◽  
Pulse Tube Refrigerator ◽  
Energy Equations

An orifice type pulse tube refrigerator (OPTR) was designed, built and operated to provide cryogenic cooling. The OTPR is a travelling wave thermoacoustic refrigerator that operates on a modified reverse Stirling cycle. We consider a system that is comprised of a pressure wave generator (a linear motor), an aftercooler heat-exchanger, a regenerator (comprising of a porous structure for energy separation), a pulse tube (in lieu of a displacer piston as found in Stirling refrigerators) with a cold and a warm heat-exchanger at its two ends, a needle-type orifice valve, an inertance tube and a buffer volume. The experimental characterization is done at various values of mean pressure of helium (∼ 0.35 MPa–2.2 MPa), amplitude of pressure oscillations, frequency of operation and size of orifice opening. A detailed time-dependent axisymmetric computational fluid dynamic (CFD) model of the OPTR is simulated to predict the performance of the OPTR. In the CFD model, the continuity, momentum and energy equations are solved for both the refrigerant gas (helium) and the porous media regions (the regenerator and the three heat-exchangers) in the OPTR. An accurate representation of heat transfer in the porous media is achieved by employing a thermal non-equilibrium model to couple the gas and solid (porous media) energy equations. In the future, a validated computational model can be used for system improvement and optimization.

Computational and experimental investigations in a cyclone dust separator

1997 ◽  
Vol 211 (4) ◽  
pp. 247-257 ◽  
Author(s):  
S M Fraser ◽  
A M Abdel-Razek ◽  
M Z Abdullah
Keyword(s):  
Flow Field ◽  
Richardson Number ◽  
Swirling Flow ◽  
Laser Doppler Anemometry ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Experimental Results ◽  
Experimental Investigations ◽  
Cyclone Chamber ◽  
Dust Separator

Three-dimensional turbulent flow in a model cyclone has been simulated using PHOENICS code and experimental studies carried out using a laser Doppler anemometry (LDA) system. The experimental results were used to validate the computed velocity distributions based on the standard and a modified k-∊ model. The standard k-∊ model was found to be unsatisfactory for the prediction of the flow field inside the cyclone chamber. By considering the strong swirling flow and the streamlined curvature, a k-∊ model, modified to take account of the Richardson number, provided better velocity distributions and better agreement with the experimental results.

Numerical Simulation of Heat Pumping in a Pulse Tube Refrigerator

2007 ◽  
Author(s):  
Takao Koshimizu ◽  
Hiromi Kubota ◽  
Yasuyuki Takata ◽  
Takehiro Ito
Keyword(s):  
Numerical Simulation ◽  
Pulse Tube ◽  
Pulse Tube Refrigerator ◽  
Heat Quantity ◽  
The Difference ◽  
Regenerator Material ◽  
Energy Equations ◽  
Pulse Tube Refrigerators ◽  
Heat And Fluid Flow ◽  
Heat Pumping

Numerical simulation of heat and fluid flow in a basic and an orifice pulse tube refrigerator have been performed to visualize heat pumping generated in the regenerator and the pulse tube, and to clarify the difference in heat pumping caused by the phase difference between pressure and displacement of gas. Common components of the regenerator and the pulse tube are used in the basic and the orifice pulse tube refrigerator. The flow in the tube is assumed to be one-dimensional and compressible. As governing equations, the continuity, momentum and energy equations are used in this study. From the temperature and velocity field obtained as a result of the simulation, the relation between the displacement and the temperature change of gas elements is visually clarified, and consequently it is found that the characteristic that the temperatures of gas elements are nearly higher than those of the regenerator material or the pulse-tube wall during compression and lower during expansion is very important for the heat pumping in basic and orifice pulse tube refrigerators. Furthermore, the behavior of heat pumping in the basic and the orifice pulse tube refrigerator is illustrated by analyzing the relation between the displacement of gas elements and heat quantity transferred to the wall from the gas elements, and the difference in heat pumping between the basic and the orifice pulse tube refrigerator is made clear.

Bond Behavior of CFRP Cured Laminates: Experimental and Numerical Investigation

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
M. Naser ◽  
R. Hawileh ◽  
J. A. Abdalla ◽  
A. Al-Tamimi
Keyword(s):  
Reinforced Concrete ◽  
Fe Simulation ◽  
Experimental Studies ◽  
Theoretical Work ◽  
Experimental Results ◽  
Fiber Reinforced Polymers ◽  
Experimental Investigations ◽  
Fiber Reinforced ◽  
Reinforced Polymers ◽  
Bond Behavior

The use of externally bonded carbon fiber-reinforced polymers (CFRPs) as strengthening systems to improve the condition and overall capacity of existing reinforced concrete structural members is found to be a promising scheme. This field has drawn the attention of many researchers in the past two decades through the implementation of much theoretical work as well as experimental studies. It was evident through many experimental investigations conducted by a number of researchers that the bond action between fiber-reinforced polymers and reinforced concrete members is considered one of the main factors affecting the performance and reliability of external strengthening systems and warrants further investigation. Debonding failure is a brittle mode of failure that may occur prematurely before strengthened members develop their full composite and expected capacities. This paper aims to investigate the bond behavior between the CFRP-concrete interface via experimental work and finite element (FE) simulations. The experimental study consisted in testing nine concrete prisms with different bonded lengths of the CFRP plates that vary between 25% (60 mm), 50% (120 mm), and 75% (180 mm) of the total length of the concrete prisms and instrumented with strain gauges. A FE simulation model was created and validated using the experimental results of the tested specimens, and a parametric study was carried out to investigate the effect of several parameters on the bond behavior between CFRP and concrete surfaces. The trend of the FE simulation results shows a good agreement with the experimental results and those available in the literature. It was observed that the optimum length of the CFRP plate is in the range between 150 mm and 160 mm when bonded to concrete surfaces. Other conclusions and observations were drawn based on the experimental and numerical results.

Study on Flow Properties of Straightener in Pulse Tube Refrigerator with Numerical Simulation

2013 ◽  
Vol 281 ◽  
pp. 268-271
Author(s):  
Wen Qing Liang ◽  
Hua Qian ◽  
Xiao Hong Zheng ◽  
Bin Xu ◽  
Lu Lu Shi
Keyword(s):  
Numerical Simulation ◽  
Porous Media ◽  
Pressure Drop ◽  
Gas Flow ◽  
Flow Distribution ◽  
Pulse Tube ◽  
Flow Properties ◽  
Improve Performance ◽  
Pulse Tube Refrigerator ◽  
Key Parameter

The straightener of pulse tube refrigerator (PTR) can change gas flow distribution in the tube and improve performance of PTR .In this paper numerical simulation is used to study and optimize the property parameters of straightener with helium as work fluid. The straightener is treated as porous media. The key parameter fk. is defined as the ratio of streamwise and transverse permeabilities. The smallest length of straightener is optimized by changing the value of fk. The result shows that straightener can change gas flow distribution in tube and improve performance of PTR. fk. is bigger, the length of straightener is shorter and streamwise pressure drop is smaller.

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