Experimental investigation of R134a flow in a 1.65 mm copper minitube

Tekin, Bilgehan
This thesis investigates the refrigerant (R-134a) flow in a minitube experimentally. The small scale heat transfer is a relatively new research area and has been in favor since the end of 1970’s. Refrigerant flow in mini- and microscale media is a potential enhancement factor for refrigeration technology in the future. For the forthcoming developments and progresses, experimental studies are invaluable in terms of having an insight and contributing to the establishment of infrastructure in the field in addition to leading the numerical and theoretical approaches. The studies in the literature show that low mass flow rate and constant wall temperature approach in minitubes and minichannels were not among the main areas of interest. Therefore, an experimental set-up was prepared in order to perform experiments of two-phase refrigerant flow in a 1.65 mm diameter copper minitube with the constant wall temperature approach. The design, preparation, and modifications of the experimental set-up are explained in this thesis. Two-phase flow and quality arrangements were done by pre-heating the refrigerant at saturation pressure and the constant wall temperature was achieved by a secondary cycle with water and ethylene glycol mixture as the working fluid. The heat transfer coefficient and the pressure drop for the two-phase flow with varying quality values and saturation temperatures of the refrigerant were calculated and compared with the results available in literature.


A study of laminar forced film condensation of vapor flowing in cross-flow direction through the annular space between two concentric cylinders
Atılgan, Ahmet Koray; Yamalı, Cemil; Department of Mechanical Engineering (2006)
In this study laminar forced film condensation of vapor flowing in cross-flow direction through the annular space between two concentric cylinders was investigated numerically. To achieve this, governing equations of the vapor and the condensate flow in cross-flow direction between two concentric cylinders were developed. After obtaining the equations in integral forms by using the finite difference technique the vapor boundary layer thicknesses on the inner and outer cylinders and the condensate layer thic...
Experimental comparison of different minichannel geometries for use in evaporators
Ağartan, Yiğit Ata; Güvenç Yazıcıoğlu, Almıla; Department of Mechanical Engineering (2012)
This thesis investigates the refrigerant (R-134a) flow in three minichannels having different geometries experimentally. During the last 40 years heat transfer in small scales has been a very attractive research area. Improvements in heat transfer in the refrigeration applications by means of usage of micro/minichannels provide significant developments in this area. Also it is known that experimental studies are very important to constitute a database which is beneficial for new developments and research. D...
A Numerical Simulation of non-uniform Magnetic Field Effect on Ferrofluid Flow in a Half-Annulus Enclosure with Sinusoidal Hot Wall
Oglakkaya, F. S.; Bozkaya, Canan (2016-09-25)
In this study, the problem of two-dimensional, laminar ferrofluid flow in a semi-annulus enclosure with sinusoidal hot wall is investigated numerically by using the dual reciprocity boundary element method. The flow is under the influence of a nodal magnetic source placed below the mid of the sinusoidal inner wall. The equations governing the present problem are obtained under the principles of ferrohydrodynamics and magnetohydrodynamics. The numerical computations are performed for various values of Raylei...
Local thermal resonance control of GaInP photonic crystal membrane cavities using ambient gas cooling
Sokolov, Sergei; LİAN, Jin; Yüce, Emre; COMBRİÉ, Sylvain; LEHOUCQ, Gaelle; De Rossi, Alfredo; Mosk, Allard P. (2015-04-27)
We perform spatially dependent tuning of a GaInP photonic crystal cavity using a continuous wave violet laser. Local tuning is obtained by laser heating of the photonic crystal membrane. The cavity resonance shift is measured for different pump positions and for two ambient gases: He and N-2. We find that the width of the temperature profile induced in the membrane depends strongly on the thermal conductivity of the ambient gas. For He gas, a narrow spatial width of the temperature profile of 2.8 mu m is pr...
Numerical investigation of solidification
Alrmah, Masoud; Dursunkaya, Zafer; Department of Mechanical Engineering (2005)
Finite element solution of solidification process in 2-D Cartesian and axisymmetric geometries is investigated. The use of finite element may result in spurious increase of temperature in the field and the selection of the mushy zone range when used as a numerical tool along with the selection of the mesh size results in large errors in the predicted solidification time. The approach works best for problems where the mushy zone range is finite and the thermal conductivities of both phases are high.
Citation Formats
B. Tekin, “Experimental investigation of R134a flow in a 1.65 mm copper minitube,” M.S. - Master of Science, Middle East Technical University, 2011.