scholarly journals Numerical modelling of the temperature distribution in a two-phase closed thermosyphon

2013 ◽  
Vol 60 (1-2) ◽  
pp. 122-131 ◽  
Author(s):  
Bandar Fadhl ◽  
Luiz C. Wrobel ◽  
Hussam Jouhara
Keyword(s):  
Temperature Distribution ◽  
Numerical Modelling ◽  
Two Phase

scholarly journals Investigation of Separated Two-Phase Thermosiphon Loop for Relieving the Air-Conditioning Loading in Datacenter

Energies ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 105 ◽  
Author(s):  
Hafiz Daraghmeh ◽  
Mohammed Sulaiman ◽  
Kai-Shing Yang ◽  
Chi-Chuan Wang
Keyword(s):  
Temperature Distribution ◽  
Energy Saving ◽  
Air Conditioning ◽  
Energy Savings ◽  
Filling Ratio ◽  
Two Phase ◽  
System Pressure ◽  
Optimum Energy ◽  
Free Cooling ◽  
R 134A

This study investigates the feasibility of using R-134a filled separated two-phase thermosiphon loop (STPTL) as a free cooling technique in datacenters. Two data center racks one of them is attached with fin and tube thermosiphon were cooled by CRAC unit (computer room air conditioning unit) individually. Thermosiphon can help to partially eliminate the compressor loading of the CRAC; thus, energy saving potential of thermosiphon loop was investigated. The condenser is a water-cooled design and perfluoroalkoxy pipes were used as adiabatic riser/downcomer for easier installation and mobile capability. Tests were conducted with filling ratio ranging from 0 to 90%. The test results indicate that the energy saving increases with the rise of filling ratio and an optimum energy savings of 38.7% can be achieved at filling ratios of 70%, a further increase of filling ratio leads to a reduction in energy saving. At a low filling ratio like 10%, the evaporator starves for refrigerant and a very uneven air temperature distribution occurring at the exit of data rack. The uneven temperature distribution is relieved considerably when the evaporator is fully flooded. It is also found that the energy saving is in line with the rise of system pressure. Overfilling of the evaporator may lead to a decline of system pressure. A lower thermal resistance occurs at high filling ratios and higher ambient temperature.

Experimental and Numerical Evaluation of Small-Scale Cryosurgery Using Ultrafine Cryoprobe

2013 ◽  
Author(s):  
Junnosuke Okajima ◽  
Atsuki Komiya ◽  
Shigenao Maruyama
Keyword(s):  
Numerical Simulation ◽  
Temperature Distribution ◽  
Biological Tissue ◽  
Bioheat Transfer ◽  
Small Scale ◽  
Outer Diameter ◽  
Two Phase ◽  
Inner Diameter ◽  
Surgical Treatments ◽  
Tube Structure

Cryosurgery is one of the surgical treatments using a frozen phenomenon in biological tissue. In order to reduce the invasiveness of cryosurgery, the miniaturization of cryoprobe, which is a cooling device for cryosurgery, has been required. The authors have developed a ultrafine cryoprobe for realizing low-invasive cryosurgery by the local freezing. The objective of this study is to evaluate the small-scale cryosurgery using the ultrafine cryoprobe experimentally and numerically. The ultrafine cryoprobe has a double-tube structure and consists of two stainless microtube. The outer diameter of ultrafine cryoprobe was 550 μm. The inner tube, which has 70 μm in inner diameter, depressurizes the high-pressure liquidized refrigerant. Depressurized refrigerant changes its state to two-phase and passes through the gap between outer and inner tube. The alternative Freon of HFC-23 was used as a refrigerant, which has the boiling point of −82°C at 0.1 MPa. The cooling performance of this ultrafine cryoprobe was tested by the freezing experiment of the gelated water kept at 37°C. The gelated water at 37°C is a substitute of the biological tissue. As a result of the cooling in 1 minute, the surface temperature of the ultrafine cryoprobe was reached at −35°C and the radius of frozen region was 2 mm. In order to evaluate the temperature distribution in the frozen region, the numerical simulation was conducted. The two-dimensional axisymmetric bioheat transfer equation with phase change was solved. By using the result from the numerical simulation, the temperature distribution in the frozen region and expected necrosis area is discussed.

Entropy hemodynamics particle-fluid suspension model through eccentric catheterization for time-variant stenotic arterial wall: Catheter injection

2019 ◽  
Vol 16 (11) ◽  
pp. 1950164 ◽  
Author(s):  
Kh. S. Mekheimer ◽  
A. Z. Zaher ◽  
A. I. Abdellateef
Keyword(s):  
Heat Transfer ◽  
Shear Stress ◽  
Temperature Distribution ◽  
Wall Shear Stress ◽  
Outer Cylinder ◽  
Flow Characteristics ◽  
Two Phase ◽  
Eccentric Cylinder ◽  
Wall Shear ◽  
Suspension Model

Catheterization has an imperative rule in heat transfer investigations, which are frequently applied to analyze and deal with the heart transfer studies. Here, the entering of a catheter adjusts the flow of the blood and it affects the hemodynamic status in the artery region. In practical clinical cases, catheters cannot be precisely concentric with the artery. The impartial of this work is to investigate the behavior of a blood streaming characteristics, in the case of injecting the catheter eccentrically all the way through a stenotic overlapping artery. In this paper, we consider the heat transfer within the presence of blood corpuscle which has been characterized by a macroscopic two-phase model (i.e. a suspension of erythrocytes in plasma). The model here considers the blood fluid as a liquid fluid with adjourned particles in the gap bounded by the eccentric cylinder. The inside cylinder is identically rigid demonstrating the movable thin catheter and kept at constant temperature, where the outer cylinder is a taper cylinder demonstrating the artery that has overlapping stenosis and it is cooled and maintained at zero temperature. The coupled differential equations for both fluid (plasma) and particle (erythrocyte) phases have been solved. The expressions for the flow characteristics, namely, the flow rate, the impedance (resistance to flow), the wall shear stress and the temperature distribution, have been derived. The model is very useful in medicine, where the hemodynamic speed is higher for eccentric case than that of concentric one. Also, the temperature distribution and the entropy generation in the state of eccentric position are higher than in the case of the concentric position. A significant increase in the magnitude of the impedance and the wall shear stress occurs for an increase in the hematocrit, C for diseased blood.

scholarly journals Numerical modelling approach for the temperature dependent forming behaviour of Ti-6Al-4V

2018 ◽  
Vol 190 ◽  
pp. 12004
Author(s):  
Thomas Papke ◽  
Matthias Graser ◽  
Marion Merklein
Keyword(s):  
Elevated Temperature ◽  
Temperature Distribution ◽  
Numerical Modelling ◽  
Tensile Test ◽  
Numerical Simulations ◽  
Numerical Models ◽  
Uniaxial Tensile ◽  
Temperature Dependent ◽  
Inhomogeneous Temperature ◽  
Forming Behaviour

Titanium alloys offer several beneficial characteristics, such as high specific strength, metallurgical stability at elevated temperature, biocompatibility and corrosion resistance. With regard to these superior properties, Ti-6Al-4V is a commonly used titanium alloy for aerospace components and medical products. The production of parts made of Ti-6Al-4V can be done in various ways. One approach is forming at elevated temperature, which requires a focused design of parts, processes and numerical modelling of the forming process. Essential input parameters for the numerical models are temperature dependent material parameters. Since, the yield stress and Young's modulus of the material decrease significantly at elevated temperature, the forming limits are enhanced. For the characterization of the forming behaviour, uniaxial tensile tests at temperatures from 250 °C to 400 °C have been conducted. The samples are heated by conduction in a thermal-mechanical simulator for the tensile test. However, the resulting inhomogeneous temperature distribution along the longitudinal axis of the specimen is a challenge in order to measure proper material properties. Inhomogeneous temperature distribution leads to varying mechanical properties and temperature dependent forming behaviour. To overcome this issue, simple numerical models based on experimental data are necessary, which allow the estimation of the influence of the inhomogeneous temperature distribution. In this paper, therefore, the temperature distribution and the subsequent tensile test are investigated using electrical-thermal and mechanical numerical simulations of the tensile test at elevated temperature. With the combined approach of experimental tests and numerical simulations, the forming behaviour of Ti-6Al-4V can be modelled.

scholarly journals Numerical Modelling and Simulation of Two-Phase Flow Flushing Method for Pipeline Cleaning in Water Distribution Systems

Water ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2470
Author(s):  
Zhaozhao Tang ◽  
Wenyan Wu ◽  
Xiaoxi Han ◽  
Ming Zhao ◽  
Jingting Luo ◽  
...  
Keyword(s):  
Numerical Modelling ◽  
Distribution Systems ◽  
Water Distribution ◽  
Two Phase Flow ◽  
Growth Ring ◽  
Water Distribution Systems ◽  
Water Phase ◽  
Phase Flow ◽  
Two Phase ◽  
Secondary Pollution

Secondary pollution by microorganisms and substances peeling off from the “growth ring” causes clean water deterioration during the water distribution process. In order to reduce the secondary pollution, our previous research investigated the best settings of a two-phase flow flushing method for pipeline cleaning in water distribution systems experimentally, and a case study was carried out for comparison of the efficiencies between two-phase and single-phase flow methods. In this paper, based on the results of the experimental study, numerical modelling and a simulation study are carried out by FLUENT to evaluate the performance of the two-phase flow flushing method for removal of the “growth ring”. Results: the simulation results match the experimental results; pressure, water-phase flow velocity and water-phase volume ratio distributions in a section of pipe are simulated and analysed; the shear force against time in a period is obtained; elbow pipes cause flushing energy loss, and therefore, at most one section of elbow pipe is flushed in one flushing period.

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