Proceedings of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences, 1997
Proper orthogonal decomposition (the Karhunen-Loève expansion) is applied to convective flows in ... more Proper orthogonal decomposition (the Karhunen-Loève expansion) is applied to convective flows in a tall differentially heated cavity. Empirical spatial eigenfunctions are computed from a multicellular solution at supercritical conditions beyond the first Hopf bifurcation. No assumption of periodicity is made, and the computed velocity and temperature eigenfunctions are found to be centro-symmetric. A lowdimensional model for the dynamical behaviour is then constructed using Galerkin projection. The reduced model successfully predicts the first Hopf bifurcation of the multicellular flow. Results determined from the low-order model are found to be in qualitative agreement with known properties of the full system even at conditions far from criticality.
This study presents an analytical flow model for the screw pump and compares it with the numerica... more This study presents an analytical flow model for the screw pump and compares it with the numerical simulations for the lubrication system of a variable speed hermetic reciprocating compressor used mainly in household refrigerators. Since variable capacity compressors (VCC) can be operated at different rotational speeds, a sufficient lubrication is required even at low rotational speeds where centrifugal effects are at a minimum. The lubrication system of such compressors includes a screw pump inside their crankshaft for this purpose. Using the analytical flow model, effects of the main design parameters for the screw pump to maximize the mass flow rate of the lubricant released from the upper part of the crankshaft are predicted and compared with numerical results. Specifically, the effects of the rotational speed, the oil viscosity, the submersion depth of the crankshaft in the oil sump and screw aspect ratio are investigated in this paper.
Bu calismada ev tipi buzdolaplarinda kullanilan degisken devirli hermetik pistonlu kompresorlerin... more Bu calismada ev tipi buzdolaplarinda kullanilan degisken devirli hermetik pistonlu kompresorlerin yaglama sisteminde bulunan vidali pompa etrafindaki akis analitik olarak modellenmis olup, sayisal modellemeler ile karsilastirilmistir. Degisken kapasiteli kompresorler (VCC) farkli devir sayilarinda calistirilabildikleri icin, merkezkac etkilerin en az seviyede oldugu dusuk devir sayilarinda dahi yeterli bir yaglamaya ihtiyac duyulmaktadir. Bu amac icin, krank mili icerisinde yer alan vidali pompa bu tip kompresorlerin yaglama sisteminin bir parcasidir. Analitik akis modeli kullanilarak, krank mili ucundan cikan kutlesel yag debisini arttiracak ana tasarim parametrelerinin etkileri tahmin edilmis ve sayisal sonuclar ile karsilastirilmistir. Bu calismada ozellikle devir sayisinin, yag viskozitesinin, krank milinin yag haznesi icerindeki daldirma derinliginin ve vida dis oraninin etkileri incelenmistir
Pamukkale University Journal of Engineering Sciences, 2018
Bu çalışmada farklı geometrideki mikrokanallar içerisinde saf su akışı için elde edilen cidar kay... more Bu çalışmada farklı geometrideki mikrokanallar içerisinde saf su akışı için elde edilen cidar kayma gerilmesi ve basınç farkı değerleri sayısal olarak elde edilmiştir. Çalışma, benzer bir laboratuvar ortamında farklı debilerde endotel ve immun sistem hücreleri üzerinde meydana gelebilecek farklı fiziksel etkileri ve bu hücrelerin davranışlarını inceleyebilmek için bir ön çalışma niteliğindedir. Belirlenen debi aralığında, endotel hücrelerinin ve monosit hücrelerinin in-vivo'da fizyolojik olarak maruz kaldıkları ya da kalabilecekleri alt ve üst cidar kayma gerilmesi değerleri sayısal olarak tahmin edilmeye çalışılmıştır. Bu kapsamda; farklı genişleme oranlarına sahip ani genişlemeli mikrokanallar, bir cidarı kaviteli ve simetrik kıvrımlı mikrokanal olarak adlandırılan üç değişik konfigürasyonda ve farklı hacimsel debi değerlerinde analizler yapılarak, mikrokanal alt cidarlarında meydana gelen kayma gerilmesi değerleri ve kanal girişi ile çıkışı arasında oluşan basınç farkı değerleri sayısal olarak elde edilmiştir. In this study, wall shear stress and pressure difference values for a pure water flow in various microchannel configurations are obtained numerically. Through simulations, physical effects of various flow rates on endothelium and immune system cells are predicted and case studies are carried out to investigate the behavior of such cells under similar laboratory conditions. In-vivo physiological behavior of endothelium and monocyte cells under real conditions can be predicted by pressure differences and wall shear stresses calculated for various flowrates. In this concept, various microchannel configurations such as sudden expanding microchannels with different expansion ratios, microchannels with cavities on one side and symmetrically curved microchannels are designed and CFD simulations are carried out to obtain computational values of the pressure drops between the inlet and outlet of the microchannels as well as wall shear stress distributions on the bottom walls of the configurations.
International Journal of Automotive Engineering and Technologies, 2017
In this study, it is aimed to simulate aerodynamic forces acting on the windshield wiper system o... more In this study, it is aimed to simulate aerodynamic forces acting on the windshield wiper system on a simplified geometry at different blade angles. Numerical simulations reveal that at critical blade angles, undesired lift forces can reach their peak values. The blade-spoiler geometry is modified in a manner to alter aerodynamic lift and drag coefficients. On a simplified front windshield it is shown that at a blade angle of 40 , lift forces can be converted to pressing forces by implementing suggested modifications. Furthermore 2 vortex identification is used to understand the formation of vortex structures at different blade angles. On the other hand, soiling tests are performed both on original and modified wiper geometries and their performances are compared.
International Journal of Heat and Mass Transfer, 2003
Three-dimensional free convection in a vertical channel with spatially periodic, flush-mounted he... more Three-dimensional free convection in a vertical channel with spatially periodic, flush-mounted heat sources is investigated by a spectral element method. All numerical solutions are obtained using a time-accurate finite-difference integration scheme capable of capturing temporal instabilities that spontaneously appear at large values of Grashof number, Gr. In addition, the leading order approximation of the 3-D solution for small Gr is derived and compared with the numerical solutions. The agreement is excellent for sufficiently small Gr. Computations are carried out for a Boussinesq fluid, Prandtl number, Pr ¼ 0:71, non-dimensional reference temperature, H à b ¼ 0:12 and values of Grashof number in the range 0:1 6 Gr 6 5  10 4. For given aspect ratios, and for sufficiently small values of Grashof number, the solution evolves to a unique, time-independent state that exhibits the maximum symmetry consistent with the boundary conditions. At Gr à ' 28,000, self-sustained oscillations appear spontaneously in the flow and thermal fields. For time-dependent solutions (Gr P Gr Ã) the symmetry of the flow and temperature fields breaks down. Temperature and velocity distributions as well as maximum temperature, maximum velocity and local Nusselt number distributions are presented for the values of Grashof number studied. For time-dependent flows, instantaneous as well as averaged-in-time solutions are discussed.
A zero-net-mass flux Jet and Vortex Actuator (JaVA) device for active flow control was investigat... more A zero-net-mass flux Jet and Vortex Actuator (JaVA) device for active flow control was investigated in detail experimentally. The JaVA system in this study is derived from the work of Lachowicz et al., 1999. However, unlike there, we built a larger JaVA system and tested it in still water at much lower frequencies of order one. While attesting the same governing JaVA parameters (e.g, Reynolds number, scaled amplitude), such low-frequency values would allow us real-time observations with naked eye. The typical flow regimes induced by the JaVA system include angled jet, vertical jet, wall jet and vortex flows, as reported by Lachowicz et al., 1999. In this paper, we investigate the detailed quantitative temporal behaviour of basic JaVA-induced flow types utilizing the optical flow concept based on an image-gradient processing method. The temporal dynamics of instantaneous velocity fields obtained via optical flow are then investigated using Fourier analysis.
The aim of this study is to numerically investigate the effects of various parameters on the lubr... more The aim of this study is to numerically investigate the effects of various parameters on the lubricant (oil)-coolant two phase flow in the lubrication system of hermetic compressors commonly used on household refrigerators. Lubrication oil is pumped from the sump through an asymmetrically opened hole on the bottom of the crankshaft (suction side or inlet) by its rotational motion and climbs as an oil film on the internal surface of the helical channel carved on the crankshaft surface. This oil film is directed to crankshaft upper exit discharging into the coolant refrigerant and it is used to lubricate the moving components of the compressor including the cylinder piston. The oil forms an i mmiscible mixture with coolant, thus a two phase flow model using Volume of Fluid (VOF) method is used. Specifically, the mass flow-rate of oil is determined as a function of the rotational speed, oil viscosity and the submersion depth of the crankshaft in the oil-sump. With increasing rotational...
In this study a numerical investigation of a suction muffler in a hermetic reciprocating compress... more In this study a numerical investigation of a suction muffler in a hermetic reciprocating compressor of a domestic refrigerator is performed using a finite volume based flow solver (Fluent). In order to reveal the behavior of the flow realistically, unsteady experimental pressure data has been used in the outlet boundary condition for the simulations. Detailed investigations are carried out to reveal the instantaneous flow behavior in different muffler sections such as channel and chambers based on the mass flow rate variation with respect to crankshaft angle. It is shown that there is a phase shifting between the mass flow rates through the chamber inlets. Future studies are underway to improve and optimize the muffler design in an effort to maximize the flow rate while keeping the noise levels at a minimum.
In this numerical study, the effect of combined suction and blowing with constant mass flux on he... more In this numerical study, the effect of combined suction and blowing with constant mass flux on heat transfer enhancement and flow separation control behind a backward facing step (BFS) in a sufficiently long channel is investigated. The simulations have been carried out by a laminar, incompressible, unsteady open-source flow solver (OpenFoam). Using three different Reynolds numbers for the base-flow (Re = 200, 400 and 600), a parametric investigation of ejections and suctions is performed where the jet configurations are modeled as to produce a zero net mass flux in the channel. The three equally-sized slots for flow control are located on the upper, lower walls of the channel and on the vertical step wall. The magnitudes of jet velocities for suction and blowing are determined with respect to the mean base flow velocity for four different values and jet off-condition. The representative variation of the mean friction coefficient and Nusselt number along the bottom wall downstream the step are reported in an effort to determine the most effective operation condition.
Fluttering suction valves are important components of hermetic reciprocating compressors used in ... more Fluttering suction valves are important components of hermetic reciprocating compressors used in refrigerators. The design parameters of the valve reed strongly determine the mass flow rate and consequently the compressor efficiency. Therefore, it is necessary to carefully design the reed valves to maximize compressor performance. In this study, a numerical flow model to mimic a fluttering suction valve in hermetic reciprocating compressors is developed. To simulate the unsteady flow dynamics and the motion of the fluttering valve in the cylinder, a simplified test geometry is used, where a fully coupled fluid structure interaction (FSI) problem is solved. The main goal of the study is to reveal the effects of some important design parameters of the valve reed such as the thickness, diameter of the circular part of the valve and the distance between valve reed and valve plate. These design parameters are vital for improving the aerodynamic and aeroacoustic behavior of the flow in the compressor. It is shown that increasing thickness of the valve reed decreases the mass flow rate significantly where the head diameter of the reed and distance between the reed and the plate have minor effects on both mass flow rate and displacement of the reed.
The aim of this experimental study is to investigate the mass flow rate of the lubricating oil in... more The aim of this experimental study is to investigate the mass flow rate of the lubricating oil in a hermetic reciprocating compressor. Essential parameters affecting the performance of the lubrication are the rotational speed of the crankshaft, the viscosity of the oil, the operating temperature and the submersion depth of the crankshaft. An experimental setup was built as to measure the oil mass flow rate with respect to the oil temperature variation during different operating conditions. The influence of the governing parameters such as the rotational speed, temperature (viscosity) and the submersion depth on the mass flow rate from crankshaft outlet are studied in detail. In addition, the oil flow visualization from the upper hole of the crankshaft is performed using a high-speed camera in order to observe the effectiveness of the lubrication of the various parts of the compressor. This study reveals that with increasing rotational speed, the submersion depth of the crankshaft and with decreasing viscosity of the lubricant, the mass flow rate from the crankshaft increases.
The aim of this study is to numerically investigate the effects of various parameters on the lubr... more The aim of this study is to numerically investigate the effects of various parameters on the lubricant (oil)-coolant two phase flow in the lubrication system of hermetic compressors commonly used on household refrigerators. Lubrication oil is pumped from the sump through an asymmetrically opened hole on the bottom of the crankshaft (suction side or inlet) by its rotational motion and climbs as an oil film on the internal surface of the helical channel carved on the crankshaft surface. This oil film is directed to crankshaft upper exit discharging into the coolant refrigerant and it is used to lubricate the moving components of the compressor including the cylinder piston. The oil forms an immiscible mixture with coolant, thus a two phase flow model using Volume of Fluid (VOF) method is used. Specifically, the mass flow-rate of oil is determined as a function of the rotational speed, oil viscosity and the submersion depth of the crankshaft in the oil-sump. With increasing rotational speed and submersion depth, the mass flow-rate through the crankshaft upper exit also increases. With increasing oil viscosity the mass flow-rate through the crankshaft upper exit decreases due to the increased friction.
Proceedings of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences, 1997
Proper orthogonal decomposition (the Karhunen-Loève expansion) is applied to convective flows in ... more Proper orthogonal decomposition (the Karhunen-Loève expansion) is applied to convective flows in a tall differentially heated cavity. Empirical spatial eigenfunctions are computed from a multicellular solution at supercritical conditions beyond the first Hopf bifurcation. No assumption of periodicity is made, and the computed velocity and temperature eigenfunctions are found to be centro-symmetric. A lowdimensional model for the dynamical behaviour is then constructed using Galerkin projection. The reduced model successfully predicts the first Hopf bifurcation of the multicellular flow. Results determined from the low-order model are found to be in qualitative agreement with known properties of the full system even at conditions far from criticality.
This study presents an analytical flow model for the screw pump and compares it with the numerica... more This study presents an analytical flow model for the screw pump and compares it with the numerical simulations for the lubrication system of a variable speed hermetic reciprocating compressor used mainly in household refrigerators. Since variable capacity compressors (VCC) can be operated at different rotational speeds, a sufficient lubrication is required even at low rotational speeds where centrifugal effects are at a minimum. The lubrication system of such compressors includes a screw pump inside their crankshaft for this purpose. Using the analytical flow model, effects of the main design parameters for the screw pump to maximize the mass flow rate of the lubricant released from the upper part of the crankshaft are predicted and compared with numerical results. Specifically, the effects of the rotational speed, the oil viscosity, the submersion depth of the crankshaft in the oil sump and screw aspect ratio are investigated in this paper.
Bu calismada ev tipi buzdolaplarinda kullanilan degisken devirli hermetik pistonlu kompresorlerin... more Bu calismada ev tipi buzdolaplarinda kullanilan degisken devirli hermetik pistonlu kompresorlerin yaglama sisteminde bulunan vidali pompa etrafindaki akis analitik olarak modellenmis olup, sayisal modellemeler ile karsilastirilmistir. Degisken kapasiteli kompresorler (VCC) farkli devir sayilarinda calistirilabildikleri icin, merkezkac etkilerin en az seviyede oldugu dusuk devir sayilarinda dahi yeterli bir yaglamaya ihtiyac duyulmaktadir. Bu amac icin, krank mili icerisinde yer alan vidali pompa bu tip kompresorlerin yaglama sisteminin bir parcasidir. Analitik akis modeli kullanilarak, krank mili ucundan cikan kutlesel yag debisini arttiracak ana tasarim parametrelerinin etkileri tahmin edilmis ve sayisal sonuclar ile karsilastirilmistir. Bu calismada ozellikle devir sayisinin, yag viskozitesinin, krank milinin yag haznesi icerindeki daldirma derinliginin ve vida dis oraninin etkileri incelenmistir
Pamukkale University Journal of Engineering Sciences, 2018
Bu çalışmada farklı geometrideki mikrokanallar içerisinde saf su akışı için elde edilen cidar kay... more Bu çalışmada farklı geometrideki mikrokanallar içerisinde saf su akışı için elde edilen cidar kayma gerilmesi ve basınç farkı değerleri sayısal olarak elde edilmiştir. Çalışma, benzer bir laboratuvar ortamında farklı debilerde endotel ve immun sistem hücreleri üzerinde meydana gelebilecek farklı fiziksel etkileri ve bu hücrelerin davranışlarını inceleyebilmek için bir ön çalışma niteliğindedir. Belirlenen debi aralığında, endotel hücrelerinin ve monosit hücrelerinin in-vivo'da fizyolojik olarak maruz kaldıkları ya da kalabilecekleri alt ve üst cidar kayma gerilmesi değerleri sayısal olarak tahmin edilmeye çalışılmıştır. Bu kapsamda; farklı genişleme oranlarına sahip ani genişlemeli mikrokanallar, bir cidarı kaviteli ve simetrik kıvrımlı mikrokanal olarak adlandırılan üç değişik konfigürasyonda ve farklı hacimsel debi değerlerinde analizler yapılarak, mikrokanal alt cidarlarında meydana gelen kayma gerilmesi değerleri ve kanal girişi ile çıkışı arasında oluşan basınç farkı değerleri sayısal olarak elde edilmiştir. In this study, wall shear stress and pressure difference values for a pure water flow in various microchannel configurations are obtained numerically. Through simulations, physical effects of various flow rates on endothelium and immune system cells are predicted and case studies are carried out to investigate the behavior of such cells under similar laboratory conditions. In-vivo physiological behavior of endothelium and monocyte cells under real conditions can be predicted by pressure differences and wall shear stresses calculated for various flowrates. In this concept, various microchannel configurations such as sudden expanding microchannels with different expansion ratios, microchannels with cavities on one side and symmetrically curved microchannels are designed and CFD simulations are carried out to obtain computational values of the pressure drops between the inlet and outlet of the microchannels as well as wall shear stress distributions on the bottom walls of the configurations.
International Journal of Automotive Engineering and Technologies, 2017
In this study, it is aimed to simulate aerodynamic forces acting on the windshield wiper system o... more In this study, it is aimed to simulate aerodynamic forces acting on the windshield wiper system on a simplified geometry at different blade angles. Numerical simulations reveal that at critical blade angles, undesired lift forces can reach their peak values. The blade-spoiler geometry is modified in a manner to alter aerodynamic lift and drag coefficients. On a simplified front windshield it is shown that at a blade angle of 40 , lift forces can be converted to pressing forces by implementing suggested modifications. Furthermore 2 vortex identification is used to understand the formation of vortex structures at different blade angles. On the other hand, soiling tests are performed both on original and modified wiper geometries and their performances are compared.
International Journal of Heat and Mass Transfer, 2003
Three-dimensional free convection in a vertical channel with spatially periodic, flush-mounted he... more Three-dimensional free convection in a vertical channel with spatially periodic, flush-mounted heat sources is investigated by a spectral element method. All numerical solutions are obtained using a time-accurate finite-difference integration scheme capable of capturing temporal instabilities that spontaneously appear at large values of Grashof number, Gr. In addition, the leading order approximation of the 3-D solution for small Gr is derived and compared with the numerical solutions. The agreement is excellent for sufficiently small Gr. Computations are carried out for a Boussinesq fluid, Prandtl number, Pr ¼ 0:71, non-dimensional reference temperature, H à b ¼ 0:12 and values of Grashof number in the range 0:1 6 Gr 6 5  10 4. For given aspect ratios, and for sufficiently small values of Grashof number, the solution evolves to a unique, time-independent state that exhibits the maximum symmetry consistent with the boundary conditions. At Gr à ' 28,000, self-sustained oscillations appear spontaneously in the flow and thermal fields. For time-dependent solutions (Gr P Gr Ã) the symmetry of the flow and temperature fields breaks down. Temperature and velocity distributions as well as maximum temperature, maximum velocity and local Nusselt number distributions are presented for the values of Grashof number studied. For time-dependent flows, instantaneous as well as averaged-in-time solutions are discussed.
A zero-net-mass flux Jet and Vortex Actuator (JaVA) device for active flow control was investigat... more A zero-net-mass flux Jet and Vortex Actuator (JaVA) device for active flow control was investigated in detail experimentally. The JaVA system in this study is derived from the work of Lachowicz et al., 1999. However, unlike there, we built a larger JaVA system and tested it in still water at much lower frequencies of order one. While attesting the same governing JaVA parameters (e.g, Reynolds number, scaled amplitude), such low-frequency values would allow us real-time observations with naked eye. The typical flow regimes induced by the JaVA system include angled jet, vertical jet, wall jet and vortex flows, as reported by Lachowicz et al., 1999. In this paper, we investigate the detailed quantitative temporal behaviour of basic JaVA-induced flow types utilizing the optical flow concept based on an image-gradient processing method. The temporal dynamics of instantaneous velocity fields obtained via optical flow are then investigated using Fourier analysis.
The aim of this study is to numerically investigate the effects of various parameters on the lubr... more The aim of this study is to numerically investigate the effects of various parameters on the lubricant (oil)-coolant two phase flow in the lubrication system of hermetic compressors commonly used on household refrigerators. Lubrication oil is pumped from the sump through an asymmetrically opened hole on the bottom of the crankshaft (suction side or inlet) by its rotational motion and climbs as an oil film on the internal surface of the helical channel carved on the crankshaft surface. This oil film is directed to crankshaft upper exit discharging into the coolant refrigerant and it is used to lubricate the moving components of the compressor including the cylinder piston. The oil forms an i mmiscible mixture with coolant, thus a two phase flow model using Volume of Fluid (VOF) method is used. Specifically, the mass flow-rate of oil is determined as a function of the rotational speed, oil viscosity and the submersion depth of the crankshaft in the oil-sump. With increasing rotational...
In this study a numerical investigation of a suction muffler in a hermetic reciprocating compress... more In this study a numerical investigation of a suction muffler in a hermetic reciprocating compressor of a domestic refrigerator is performed using a finite volume based flow solver (Fluent). In order to reveal the behavior of the flow realistically, unsteady experimental pressure data has been used in the outlet boundary condition for the simulations. Detailed investigations are carried out to reveal the instantaneous flow behavior in different muffler sections such as channel and chambers based on the mass flow rate variation with respect to crankshaft angle. It is shown that there is a phase shifting between the mass flow rates through the chamber inlets. Future studies are underway to improve and optimize the muffler design in an effort to maximize the flow rate while keeping the noise levels at a minimum.
In this numerical study, the effect of combined suction and blowing with constant mass flux on he... more In this numerical study, the effect of combined suction and blowing with constant mass flux on heat transfer enhancement and flow separation control behind a backward facing step (BFS) in a sufficiently long channel is investigated. The simulations have been carried out by a laminar, incompressible, unsteady open-source flow solver (OpenFoam). Using three different Reynolds numbers for the base-flow (Re = 200, 400 and 600), a parametric investigation of ejections and suctions is performed where the jet configurations are modeled as to produce a zero net mass flux in the channel. The three equally-sized slots for flow control are located on the upper, lower walls of the channel and on the vertical step wall. The magnitudes of jet velocities for suction and blowing are determined with respect to the mean base flow velocity for four different values and jet off-condition. The representative variation of the mean friction coefficient and Nusselt number along the bottom wall downstream the step are reported in an effort to determine the most effective operation condition.
Fluttering suction valves are important components of hermetic reciprocating compressors used in ... more Fluttering suction valves are important components of hermetic reciprocating compressors used in refrigerators. The design parameters of the valve reed strongly determine the mass flow rate and consequently the compressor efficiency. Therefore, it is necessary to carefully design the reed valves to maximize compressor performance. In this study, a numerical flow model to mimic a fluttering suction valve in hermetic reciprocating compressors is developed. To simulate the unsteady flow dynamics and the motion of the fluttering valve in the cylinder, a simplified test geometry is used, where a fully coupled fluid structure interaction (FSI) problem is solved. The main goal of the study is to reveal the effects of some important design parameters of the valve reed such as the thickness, diameter of the circular part of the valve and the distance between valve reed and valve plate. These design parameters are vital for improving the aerodynamic and aeroacoustic behavior of the flow in the compressor. It is shown that increasing thickness of the valve reed decreases the mass flow rate significantly where the head diameter of the reed and distance between the reed and the plate have minor effects on both mass flow rate and displacement of the reed.
The aim of this experimental study is to investigate the mass flow rate of the lubricating oil in... more The aim of this experimental study is to investigate the mass flow rate of the lubricating oil in a hermetic reciprocating compressor. Essential parameters affecting the performance of the lubrication are the rotational speed of the crankshaft, the viscosity of the oil, the operating temperature and the submersion depth of the crankshaft. An experimental setup was built as to measure the oil mass flow rate with respect to the oil temperature variation during different operating conditions. The influence of the governing parameters such as the rotational speed, temperature (viscosity) and the submersion depth on the mass flow rate from crankshaft outlet are studied in detail. In addition, the oil flow visualization from the upper hole of the crankshaft is performed using a high-speed camera in order to observe the effectiveness of the lubrication of the various parts of the compressor. This study reveals that with increasing rotational speed, the submersion depth of the crankshaft and with decreasing viscosity of the lubricant, the mass flow rate from the crankshaft increases.
The aim of this study is to numerically investigate the effects of various parameters on the lubr... more The aim of this study is to numerically investigate the effects of various parameters on the lubricant (oil)-coolant two phase flow in the lubrication system of hermetic compressors commonly used on household refrigerators. Lubrication oil is pumped from the sump through an asymmetrically opened hole on the bottom of the crankshaft (suction side or inlet) by its rotational motion and climbs as an oil film on the internal surface of the helical channel carved on the crankshaft surface. This oil film is directed to crankshaft upper exit discharging into the coolant refrigerant and it is used to lubricate the moving components of the compressor including the cylinder piston. The oil forms an immiscible mixture with coolant, thus a two phase flow model using Volume of Fluid (VOF) method is used. Specifically, the mass flow-rate of oil is determined as a function of the rotational speed, oil viscosity and the submersion depth of the crankshaft in the oil-sump. With increasing rotational speed and submersion depth, the mass flow-rate through the crankshaft upper exit also increases. With increasing oil viscosity the mass flow-rate through the crankshaft upper exit decreases due to the increased friction.
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