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Research paper thumbnail of 3.26.4 Heat Transfer in Refrigeration Applications: Evaporators

Heat Exchanger Design Updates

Sections 3.26.1 - 3.26.6 - Place in folder for Part 3 after Section 3.25.

Research paper thumbnail of Experimental Analysis of Refrigerant Mixing in Lubricant Oil

Research paper thumbnail of Solubility and Density of Mixtures of R-744 and Two Synthetic Lubricant Oils

Research paper thumbnail of Experimental Characterization of Phase Equilibrium, Liquid Density and Viscosity of a Mixture of R-744 (CO2) and Polyol Ester Oil

Research paper thumbnail of Phase distribution of air-water flows in return bends

Research paper thumbnail of Viscosity and Thermal Conductivity of Soybean Oil-Diesel Blends Between 293 and 353 K

Research on alternative fuels such as vegetable oils is attracting considerable attention due to ... more Research on alternative fuels such as vegetable oils is attracting considerable attention due to pollutant emis-sions from conventional fuels, depletion of fossil fuel reserves, increase of petroleum costs and more severe emission protocols. This work reports on experimental data of dynamic viscosity and thermal conductivity of diesel fuel and soy-bean oil mixtures at different compositions for temperatures ranging from 293 to 353 K (20 to 80 o C). The viscosity was measured with an oscillating piston viscometer and the thermal conductivity was determined via a hot-wire meter. An Arrhenius-type relationship and a mixing rule based on the classical relationship of Eyring were used to correlate the viscosity of the pure fluids and mixtures. The blend viscosity decreases with increasing diesel concentration and decreases with temperature. The thermal conductivity of the blends was observed to increase with temperature.

Research paper thumbnail of Developing air–water flow downstream of a vertical 180° return bend

International Journal of Multiphase Flow, 2014

ABSTRACT

Research paper thumbnail of Experimental investigation of two-phase flashing flows of a binary mixture of infinite relative volatility in a Venturi tube

Experimental Thermal and Fluid Science, 2015

An experimental facility was constructed to study two-phase flashing flows of binary mixtures in ... more An experimental facility was constructed to study two-phase flashing flows of binary mixtures in a converging-diverging nozzle (Venturi tube). The effects of mass flow rate, concentration of the volatile component in the liquid phase and inlet sub-saturation (overpressure) on the axial distribution of static pressure are discussed. A transparent test section enabled visual observation of the two-phase flow in the Venturi by means of high-speed visualization (HSV) and a quantitative assessment of the velocity field was carried out using particle image velocimetry (PIV). Experimental results generated for mixtures of R-134a (volatile component) and POE ISO 10 lubricating oil (non-volatile component) showed that the liquid phase viscosity has a significant effect on both the throat pressure drop and pressure recovery in the diverging section, with the latter being directly proportional to the refrigerant concentration in the liquid phase. Visual analysis of bubble cavitation in the convergingdiverging nozzle revealed that the occurrence of two-phase flow in the throat

Research paper thumbnail of Theoretical Analysis of the Volumetric Efficiency Reduction in Reciprocating Compressors due to In-Cylinder Thermodynamics

Research paper thumbnail of Experimental Analysis of Peripheral Finned-Tube Evaporators

Research paper thumbnail of Thermodynamics, heat transer and fluid mechanics role of lubricant oil in hermetic reciprocating compressors

Research paper thumbnail of Dynamics of gas bubble growth in oil-refrigerant mixtures under isothermal depressurization

Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2012

This paper proposes a numerical model to predict the growth of gaseous refrigerant bubbles in oil... more This paper proposes a numerical model to predict the growth of gaseous refrigerant bubbles in oil-refrigerant mixtures with high contents of oil subjected to isothermal depressurization. The model considers an Elementary Cell (EC) in which a spherical bubble is surrounded by a concentric and spherical liquid layer containing a finite amount of dissolved liquid refrigerant. The pressure reduction in the EC generates a concentration gradient at the bubble interface and the refrigerant is transported to the bubble by molecular diffusion. After a sufficiently long time, the concentration gradient in the liquid layer and the bubble internal pressure reach equilibrium and the bubble stops growing, having attained its stable radius. The equations of momentum and chemical species conservation for the liquid layer, and the material balance at the bubble interface are solved via a coupled finite difference procedure to determine the bubble internal pressure, the refrigerant radial concentration distribution and the bubble growth rate. Numerical results obtained for a mixture of ISO VG10 polyolester oil and refrigerant HFC-134a showed that the bubble growth dynamics depends on model parameters such as the initial bubble and liquid layer radii, the initial refrigerant concentration in the liquid layer, the initial pressure in the liquid phase, the decompression rate and the EC temperature. Despite its simplicity, the model demonstrated to be a potential tool for predicting bubble growth and foaming that may occur as a result of cavitation in oil-lubricated bearings and refrigerant degassing from the oil sump during compressor start-up.

Research paper thumbnail of Modeling of Thermo-Magnetic Phenomena in Active Magnetic Regenerators

Volume 1: Heat Transfer in Energy Systems; Thermophysical Properties; Theory and Fundamental Research in Heat Transfer, 2013

Research paper thumbnail of Prediction of refrigerant-lubricant viscosity using the general PC-SAFT friction theory

International Journal of Refrigeration, 2014

ABSTRACT In this work, a friction theory (f-theory) viscosity model founded on the perturbed-chai... more ABSTRACT In this work, a friction theory (f-theory) viscosity model founded on the perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state (EoS) was used to calculate the viscosity of refrigerant-oil mixtures. The model, which links viscosity to the repulsive and attractive pressure terms of the PC-SAFT EoS, can provide satisfactory viscosity predictions of mixtures of carbon dioxide (R-744) and two synthetic lubricants, namely, a polyolester (POE) ISO VG 68 and an alkylbenzene (AB) ISObi,j VG 32, as well as mixtures of isobutane (R-600a) and two other synthetic lubricants, a POE ISO VG 7 and an AB ISO VG 5. The root-mean square (RMS) deviations related to the viscosity prediction were 0.69% (R-600a/POE ISO 7), 0.99% (R-600a/AB ISO VG 5), 3.16% (R-744/POE ISO VG 68) and 3.18% (R-744/AB ISO VG 32).

Research paper thumbnail of Recent Developments in Vapor Compression Technologies for Small Scale Refrigeration Applications

ASME 2011 9th International Conference on Nanochannels, Microchannels, and Minichannels, Volume 2, 2011

This paper reviews the current trends and research efforts associated with the development of min... more This paper reviews the current trends and research efforts associated with the development of miniaturized mechanical vapor compression refrigeration systems. Over the past decade, there has been a significant number of studies devoted to the miniaturization of its components, the most critical being the compressor. The paper will focus on the thermodynamic and thermal aspects of the development of small compressors and other components of small-scale cooling cycles. Whenever appropriate, issues and challenges associated with different cycle and component designs will be addressed.

Research paper thumbnail of Performance of Vertical Transient Two-Phase Flow Models Applied to Liquid Loading in Gas Wells

All Days, 2011

Liquid loading in gas wells is triggered when the produced gas loses the ability to lift the co-p... more Liquid loading in gas wells is triggered when the produced gas loses the ability to lift the co-produced liquids up the tubing. These co-produced liquids accumulate at the bottom of the wellbore, causing a higher back-pressure on the formation which reduces production from the reservoir, and may ultimately kill the well. As this phenomenon is transient in nature, it requires transient modeling for proper characterization of its associated flow features and prediction of future well performance. However, there is a lack of dedicated models that can mimic the transient behavior which is typical of liquid loading. This paper describes the modeling effort carried out to investigate the liquid loading sequence in a synthetic gas well using a commercial package for transient multiphase flow modeling and two research codes (one for steady-state flow, and one for transient flow). The results of the simulations for the pressure gradient were compared against experimental data. The experiment...

Research paper thumbnail of Analytical solution of single screw extrusion applicable to intermediate values of screw channel aspect ratio

Journal of Food Engineering, 2009

... Marcus Vinícius C. Alves a , Jader R. Barbosa Jr. ... the screw throughput and recommended th... more ... Marcus Vinícius C. Alves a , Jader R. Barbosa Jr. ... the screw throughput and recommended that the approximation of Rowell and Finlayson – by then employed in several important studies such as those by (Griffith, 1962), (Fenner, 1977), (Tadmor and Klein, 1978) and (Tadmor ...

Research paper thumbnail of A departure-function approach to calculate thermodynamic properties of refrigerant-oil mixtures

International Journal of Refrigeration, 2013

Research paper thumbnail of Solubility, density and viscosity of a mixture of R-600a and polyol ester oil

International Journal of Refrigeration, 2008

Experimental data on solubility, liquid phase density and viscosity of a mixture of R-600a and a ... more Experimental data on solubility, liquid phase density and viscosity of a mixture of R-600a and a POE ISO 7 lubricant oil are presented. A specially designed experimental facility for simultaneous measurements of the physical properties was used in the experiments at temperatures ranging from 10 to 60 C. The VLE data were correlated with the Heil-Prausnitz and Flory-Huggins activity models and the Peng-Robinson equation of state (EoS). Liquid density was correlated with the Peng-Robinson EoS and with a first-order Redlich-Kister expansion for the excess molar volume. Liquid viscosity was correlated with an excess-property approach based on the classical Eyring liquid viscosity model. Satisfactory agreement was obtained between models and experiments; maximum root mean square (RMS) deviations of models used in the VLE, density and viscosity predictions were 1.1% (VLE EoS), 0.2% (Redlich-Kister) and 3.0% (Grunberg-Nissan), respectively.

Research paper thumbnail of Modeling absorption of pure refrigerants and refrigerant mixtures in lubricant oil

International Journal of Refrigeration, 2006

This paper addresses the problem of absorption of refrigerant vapor in a stagnant layer of lubric... more This paper addresses the problem of absorption of refrigerant vapor in a stagnant layer of lubricant oil. The bulk motion of the solute is described in terms of apparent diffusion coefficients that encompass both molecular diffusion and possible macroscopic motion induced by liquid density instability and surface tension. In absorption of refrigerant mixtures, diffusion in the vapor and liquid phases are coupled with a thermodynamic model for interfacial equilibrium. Results are compared with experimental data available in the literature for absorption of several refrigerants in polyol ester oil (POE68). The adequacy of the formulation is assessed in the light of its basic assumptions and performance of the model.

Research paper thumbnail of 3.26.4 Heat Transfer in Refrigeration Applications: Evaporators

Heat Exchanger Design Updates

Sections 3.26.1 - 3.26.6 - Place in folder for Part 3 after Section 3.25.

Research paper thumbnail of Experimental Analysis of Refrigerant Mixing in Lubricant Oil

Research paper thumbnail of Solubility and Density of Mixtures of R-744 and Two Synthetic Lubricant Oils

Research paper thumbnail of Experimental Characterization of Phase Equilibrium, Liquid Density and Viscosity of a Mixture of R-744 (CO2) and Polyol Ester Oil

Research paper thumbnail of Phase distribution of air-water flows in return bends

Research paper thumbnail of Viscosity and Thermal Conductivity of Soybean Oil-Diesel Blends Between 293 and 353 K

Research on alternative fuels such as vegetable oils is attracting considerable attention due to ... more Research on alternative fuels such as vegetable oils is attracting considerable attention due to pollutant emis-sions from conventional fuels, depletion of fossil fuel reserves, increase of petroleum costs and more severe emission protocols. This work reports on experimental data of dynamic viscosity and thermal conductivity of diesel fuel and soy-bean oil mixtures at different compositions for temperatures ranging from 293 to 353 K (20 to 80 o C). The viscosity was measured with an oscillating piston viscometer and the thermal conductivity was determined via a hot-wire meter. An Arrhenius-type relationship and a mixing rule based on the classical relationship of Eyring were used to correlate the viscosity of the pure fluids and mixtures. The blend viscosity decreases with increasing diesel concentration and decreases with temperature. The thermal conductivity of the blends was observed to increase with temperature.

Research paper thumbnail of Developing air–water flow downstream of a vertical 180° return bend

International Journal of Multiphase Flow, 2014

ABSTRACT

Research paper thumbnail of Experimental investigation of two-phase flashing flows of a binary mixture of infinite relative volatility in a Venturi tube

Experimental Thermal and Fluid Science, 2015

An experimental facility was constructed to study two-phase flashing flows of binary mixtures in ... more An experimental facility was constructed to study two-phase flashing flows of binary mixtures in a converging-diverging nozzle (Venturi tube). The effects of mass flow rate, concentration of the volatile component in the liquid phase and inlet sub-saturation (overpressure) on the axial distribution of static pressure are discussed. A transparent test section enabled visual observation of the two-phase flow in the Venturi by means of high-speed visualization (HSV) and a quantitative assessment of the velocity field was carried out using particle image velocimetry (PIV). Experimental results generated for mixtures of R-134a (volatile component) and POE ISO 10 lubricating oil (non-volatile component) showed that the liquid phase viscosity has a significant effect on both the throat pressure drop and pressure recovery in the diverging section, with the latter being directly proportional to the refrigerant concentration in the liquid phase. Visual analysis of bubble cavitation in the convergingdiverging nozzle revealed that the occurrence of two-phase flow in the throat

Research paper thumbnail of Theoretical Analysis of the Volumetric Efficiency Reduction in Reciprocating Compressors due to In-Cylinder Thermodynamics

Research paper thumbnail of Experimental Analysis of Peripheral Finned-Tube Evaporators

Research paper thumbnail of Thermodynamics, heat transer and fluid mechanics role of lubricant oil in hermetic reciprocating compressors

Research paper thumbnail of Dynamics of gas bubble growth in oil-refrigerant mixtures under isothermal depressurization

Journal of the Brazilian Society of Mechanical Sciences and Engineering, 2012

This paper proposes a numerical model to predict the growth of gaseous refrigerant bubbles in oil... more This paper proposes a numerical model to predict the growth of gaseous refrigerant bubbles in oil-refrigerant mixtures with high contents of oil subjected to isothermal depressurization. The model considers an Elementary Cell (EC) in which a spherical bubble is surrounded by a concentric and spherical liquid layer containing a finite amount of dissolved liquid refrigerant. The pressure reduction in the EC generates a concentration gradient at the bubble interface and the refrigerant is transported to the bubble by molecular diffusion. After a sufficiently long time, the concentration gradient in the liquid layer and the bubble internal pressure reach equilibrium and the bubble stops growing, having attained its stable radius. The equations of momentum and chemical species conservation for the liquid layer, and the material balance at the bubble interface are solved via a coupled finite difference procedure to determine the bubble internal pressure, the refrigerant radial concentration distribution and the bubble growth rate. Numerical results obtained for a mixture of ISO VG10 polyolester oil and refrigerant HFC-134a showed that the bubble growth dynamics depends on model parameters such as the initial bubble and liquid layer radii, the initial refrigerant concentration in the liquid layer, the initial pressure in the liquid phase, the decompression rate and the EC temperature. Despite its simplicity, the model demonstrated to be a potential tool for predicting bubble growth and foaming that may occur as a result of cavitation in oil-lubricated bearings and refrigerant degassing from the oil sump during compressor start-up.

Research paper thumbnail of Modeling of Thermo-Magnetic Phenomena in Active Magnetic Regenerators

Volume 1: Heat Transfer in Energy Systems; Thermophysical Properties; Theory and Fundamental Research in Heat Transfer, 2013

Research paper thumbnail of Prediction of refrigerant-lubricant viscosity using the general PC-SAFT friction theory

International Journal of Refrigeration, 2014

ABSTRACT In this work, a friction theory (f-theory) viscosity model founded on the perturbed-chai... more ABSTRACT In this work, a friction theory (f-theory) viscosity model founded on the perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state (EoS) was used to calculate the viscosity of refrigerant-oil mixtures. The model, which links viscosity to the repulsive and attractive pressure terms of the PC-SAFT EoS, can provide satisfactory viscosity predictions of mixtures of carbon dioxide (R-744) and two synthetic lubricants, namely, a polyolester (POE) ISO VG 68 and an alkylbenzene (AB) ISObi,j VG 32, as well as mixtures of isobutane (R-600a) and two other synthetic lubricants, a POE ISO VG 7 and an AB ISO VG 5. The root-mean square (RMS) deviations related to the viscosity prediction were 0.69% (R-600a/POE ISO 7), 0.99% (R-600a/AB ISO VG 5), 3.16% (R-744/POE ISO VG 68) and 3.18% (R-744/AB ISO VG 32).

Research paper thumbnail of Recent Developments in Vapor Compression Technologies for Small Scale Refrigeration Applications

ASME 2011 9th International Conference on Nanochannels, Microchannels, and Minichannels, Volume 2, 2011

This paper reviews the current trends and research efforts associated with the development of min... more This paper reviews the current trends and research efforts associated with the development of miniaturized mechanical vapor compression refrigeration systems. Over the past decade, there has been a significant number of studies devoted to the miniaturization of its components, the most critical being the compressor. The paper will focus on the thermodynamic and thermal aspects of the development of small compressors and other components of small-scale cooling cycles. Whenever appropriate, issues and challenges associated with different cycle and component designs will be addressed.

Research paper thumbnail of Performance of Vertical Transient Two-Phase Flow Models Applied to Liquid Loading in Gas Wells

All Days, 2011

Liquid loading in gas wells is triggered when the produced gas loses the ability to lift the co-p... more Liquid loading in gas wells is triggered when the produced gas loses the ability to lift the co-produced liquids up the tubing. These co-produced liquids accumulate at the bottom of the wellbore, causing a higher back-pressure on the formation which reduces production from the reservoir, and may ultimately kill the well. As this phenomenon is transient in nature, it requires transient modeling for proper characterization of its associated flow features and prediction of future well performance. However, there is a lack of dedicated models that can mimic the transient behavior which is typical of liquid loading. This paper describes the modeling effort carried out to investigate the liquid loading sequence in a synthetic gas well using a commercial package for transient multiphase flow modeling and two research codes (one for steady-state flow, and one for transient flow). The results of the simulations for the pressure gradient were compared against experimental data. The experiment...

Research paper thumbnail of Analytical solution of single screw extrusion applicable to intermediate values of screw channel aspect ratio

Journal of Food Engineering, 2009

... Marcus Vinícius C. Alves a , Jader R. Barbosa Jr. ... the screw throughput and recommended th... more ... Marcus Vinícius C. Alves a , Jader R. Barbosa Jr. ... the screw throughput and recommended that the approximation of Rowell and Finlayson – by then employed in several important studies such as those by (Griffith, 1962), (Fenner, 1977), (Tadmor and Klein, 1978) and (Tadmor ...

Research paper thumbnail of A departure-function approach to calculate thermodynamic properties of refrigerant-oil mixtures

International Journal of Refrigeration, 2013

Research paper thumbnail of Solubility, density and viscosity of a mixture of R-600a and polyol ester oil

International Journal of Refrigeration, 2008

Experimental data on solubility, liquid phase density and viscosity of a mixture of R-600a and a ... more Experimental data on solubility, liquid phase density and viscosity of a mixture of R-600a and a POE ISO 7 lubricant oil are presented. A specially designed experimental facility for simultaneous measurements of the physical properties was used in the experiments at temperatures ranging from 10 to 60 C. The VLE data were correlated with the Heil-Prausnitz and Flory-Huggins activity models and the Peng-Robinson equation of state (EoS). Liquid density was correlated with the Peng-Robinson EoS and with a first-order Redlich-Kister expansion for the excess molar volume. Liquid viscosity was correlated with an excess-property approach based on the classical Eyring liquid viscosity model. Satisfactory agreement was obtained between models and experiments; maximum root mean square (RMS) deviations of models used in the VLE, density and viscosity predictions were 1.1% (VLE EoS), 0.2% (Redlich-Kister) and 3.0% (Grunberg-Nissan), respectively.

Research paper thumbnail of Modeling absorption of pure refrigerants and refrigerant mixtures in lubricant oil

International Journal of Refrigeration, 2006

This paper addresses the problem of absorption of refrigerant vapor in a stagnant layer of lubric... more This paper addresses the problem of absorption of refrigerant vapor in a stagnant layer of lubricant oil. The bulk motion of the solute is described in terms of apparent diffusion coefficients that encompass both molecular diffusion and possible macroscopic motion induced by liquid density instability and surface tension. In absorption of refrigerant mixtures, diffusion in the vapor and liquid phases are coupled with a thermodynamic model for interfacial equilibrium. Results are compared with experimental data available in the literature for absorption of several refrigerants in polyol ester oil (POE68). The adequacy of the formulation is assessed in the light of its basic assumptions and performance of the model.