Jorge Kurita - Academia.edu (original) (raw)
Papers by Jorge Kurita
Experimental results on gravity driven fully condensing flows in vertical tubes, their agreement ... more Experimental results on gravity driven fully condensing flows in vertical tubes, their agreement with theory, and their differences with shear driven flows ' boundary-condition sensitivities
Volume 10: Fluids Engineering
The COVID 19 pandemic has struck the global economy and slowed down human activity. Paraguay, a s... more The COVID 19 pandemic has struck the global economy and slowed down human activity. Paraguay, a small South-American country, was not an exception. This work results from the urgent need to reopen universities, schools, and other academic institutions to resume teaching activities in light of restrictive access to online learning in Paraguay. In order to contain the spread of this virus, school activities such as course lectures were placed on hold indefinitely. Inappropriate airflow in an enclosed space is one of the main factors in the spread of this virus. When combined with personal protective equipment, proper air ventilation and air replacement can significantly reduce this airborne virus’s spread. Potential sources of contaminant accumulation are stagnant locations of air in a closed volume. It is, therefore, essential to first identify these hot spots. Utilizing computational tools, such as CFD, an airflow analysis can be conducted to see any potential stagnant point. In the...
Bulletin of the American Physical Society, 2009
Proceeding of 5-6th Thermal and Fluids Engineering Conference (TFEC), 2021
Bulletin of the American Physical Society, 2009
ABSTRACT Preliminary experimental flow regime types have been observed for partial and full conde... more ABSTRACT Preliminary experimental flow regime types have been observed for partial and full condensation in a horizontal channel of millimeter scale. Effects of hydrostatic pooling, wall vibrations, vapor flow pulsations, and solid-liquid-vapor contact on the top surface of the condenser are observed. Wave phenomena such as wave reflection, standing waves, and waves on the interface of vapor bubbles are presented in 2 and 3 dimensions. Due to the high density and low kinematic viscosity of the liquid phase of the fluid (perfluorohexane), the effects observed are primarily inertial. It is found that in these flows pressure pulsation and surface tension effects very strongly influence the morphology of the interface where it contacts the top wall. Wall vibrations contribute to standing waves on the interface. This investigation outlines some of the types of flow one might expect to encounter in a millimeter scale horizontal condenser with wall vibration and pressure pulsation where inertial effects dominate the liquid flow.
2019 ASEE Annual Conference & Exposition Proceedings
2020 ASEE Virtual Annual Conference Content Access Proceedings
Proceeding of Second Thermal and Fluids Engineering Conference
Proceeding of Second Thermal and Fluids Engineering Conference
Preliminary experimental flow regime types have been observed for partial and full condensation i... more Preliminary experimental flow regime types have been observed for partial and full condensation in a horizontal channel of millimeter scale. Effects of hydrostatic pooling, wall vibrations, vapor flow pulsations, and solid-liquid-vapor contact on the top surface of the condenser are observed. Wave phenomena such as wave reflection, standing waves, and waves on the interface of vapor bubbles are presented in 2 and 3 dimensions. Due to the high density and low kinematic viscosity of the liquid phase of the fluid (perfluorohexane), the effects observed are primarily inertial. It is found that in these flows pressure pulsation and surface tension effects very strongly influence the morphology of the interface where it contacts the top wall. Wall vibrations contribute to standing waves on the interface. This investigation outlines some of the types of flow one might expect to encounter in a millimeter scale horizontal condenser with wall vibration and pressure pulsation where inertial ef...
Heat Transfer, Part B, 2005
The flow and heat transfer rates inside a condenser depend on the specification of inlet, wall, a... more The flow and heat transfer rates inside a condenser depend on the specification of inlet, wall, and exit conditions. For steady/quasi-steady internal condensing flows, the vapor's ability to sense exit condition and, for certain exit conditions, even change its density (despite low Mach numbers) allows the flow to have a rather significant dependence on conditions downstream of the condenser. The change in flows due to change in exit conditions is usually accompanied by significant changes in interfacial mass transfer rates and associated locations of the interface. Both experimental and direct computational simulation results presented here show that this is indeed the case for a large class of flows of pure vapor experiencing film condensation on the inside walls of a vertical tube. In applications, the totality of boundary conditions is determined not only by the condenser; but also by the flow-loop (or the system)-of which the condenser is only a part. Therefore, the results outlined here should contribute towards a better understanding of the behavior (particularly the extent to which flow "ellipticity" and vapor compressibility affect the flow regimes of operation-i.e. annular, plug/churn, etc.) and response of condensers (transients due to start-up, system instabilities, etc.) in different application systems (e.g. Rankine Cycle Power Plants, Capillary Pumped Loops, Looped Heat Pipes, Thermal Management Systems, etc.). In this connection, two experimental examples of relevant system instabilities are also presented here. In summary, the experimental results presented here, and the computational results summarized here but presented elsewhere, reinforce the fact that there exist multiple steady solutions (with different heat transfer rates) for different exit conditions. However under certain flow situations there exists a "natural" steady flow with a "natural" exit condition. This happens if the vapor flow is seeking a specific exit condition and the conditions downstream of the condenser allow the vapor the choice to select it.
ASME 2009 Second International Conference on Micro/Nanoscale Heat and Mass Transfer, Volume 2, 2009
This paper presents computational simulations for internal condensing flows over a range of tube/... more This paper presents computational simulations for internal condensing flows over a range of tube/channel geometries ranging from one micro-meter to several millimeters in hydraulic diameters. Over the mm-scale, three sets of condensing flow results are presented that ...
International Journal of Heat and Mass Transfer, 2011
Annals of the New York Academy of Sciences, 2006
This article presents accurate numerical solutions of the full 2D governing equations for steady ... more This article presents accurate numerical solutions of the full 2D governing equations for steady and unsteady laminar/laminar internal condensing flows of pure vapor (FC-72 and R-113) inside a vertical tube and a channel. The film condensation is on the inside wall of a tube or one of the walls of a channel (the lower wall in case of a downward sloping channel). Both experiments and simulations find that exit condition specifications are important. The computations are able to predict whether or not a steady flow exists with a well-defined and steady natural exit condition. If well-defined natural steady/quasi-steady flows exist-as is shown to be the case for gravity-dominated or strong shear-dominated condensate flows that remain parabolic up to the exit location-the computations are able to predict both the natural exit condition and any point of transition (from stable to unstable or smooth to wavy behavior) that may exist within this zone. Compared to gravity-driven cases, shear-driven cases (zero gravity or horizontal cases) tend to destabilize easily. It is found that only for gravity-driven cases interfacial waves are able to cause a concurrent enhancement in heat transfer rates along with an enhancement in interfacial shear. Also it is found that this enhancement in interfacial wave energy is significant if the condensing surface noise is in resonance with the intrinsic waves.
Annals of the New York Academy of Sciences, 2009
Reported experimental and computational results confirm that both the flow features and heat tran... more Reported experimental and computational results confirm that both the flow features and heat transfer rates inside a condenser depend on the specification of inlet, wall, and exit conditions. The theoretical and experimental results presented in this paper allow us to propose important exit condition based categorization of these flows. Of these, category II flows are defined to be cases for which exit pressures are left unspecified. However it is shown here that steady flows under specified exit pressure conditions (category I flows) are more stable and can be more easily achieved under all conditions (normal or zero-gravity). Existence of self-selected exit pressure conditions for unspecified exit condition cases (category II flows) are more difficult to achieve and are often limited to gravity driven flows. In practice, however, special hardware arrangements are required for repeatable realization of both these categories of flow. If this is not so, one often has an inadvertent category I flow (flows with specified exit pressure) without the explicit knowledge of the exit pressure value. For microgravity situations, the remedy is to run condensers under suitably specified inlet and exit pressures (category I conditions) as well as a proper cooling strategy (i.e., proper wall temperature variations).
Journal of Heat Transfer, 2007
Reported experimental and computational results confirm that both the flow features and heat-tran... more Reported experimental and computational results confirm that both the flow features and heat-transfer rates inside a condenser depend on the specification of inlet, wall, and exit conditions. The results show that the commonly occurring condensing flows’ special sensitivity to changes in exit conditions (i.e., changes in exit pressure) arises from the ease with which these changes alter the vapor flow field in the interior. When, at a fixed steady mass flow rate, the exit pressure is changed from one steady value to another, the changes required of the interior vapor flow toward achieving a new steady duct flow are such that they do not demand a removal of the new exit pressure imposition back to the original steady value—as is the case for incompressible single phase duct flows with an original and “required” exit pressure. Instead, new steady flows may be achieved through appropriate changes in the vapor/liquid interfacial configurations and associated changes in interfacial mass,...
Experimental results on gravity driven fully condensing flows in vertical tubes, their agreement ... more Experimental results on gravity driven fully condensing flows in vertical tubes, their agreement with theory, and their differences with shear driven flows ' boundary-condition sensitivities
Volume 10: Fluids Engineering
The COVID 19 pandemic has struck the global economy and slowed down human activity. Paraguay, a s... more The COVID 19 pandemic has struck the global economy and slowed down human activity. Paraguay, a small South-American country, was not an exception. This work results from the urgent need to reopen universities, schools, and other academic institutions to resume teaching activities in light of restrictive access to online learning in Paraguay. In order to contain the spread of this virus, school activities such as course lectures were placed on hold indefinitely. Inappropriate airflow in an enclosed space is one of the main factors in the spread of this virus. When combined with personal protective equipment, proper air ventilation and air replacement can significantly reduce this airborne virus’s spread. Potential sources of contaminant accumulation are stagnant locations of air in a closed volume. It is, therefore, essential to first identify these hot spots. Utilizing computational tools, such as CFD, an airflow analysis can be conducted to see any potential stagnant point. In the...
Bulletin of the American Physical Society, 2009
Proceeding of 5-6th Thermal and Fluids Engineering Conference (TFEC), 2021
Bulletin of the American Physical Society, 2009
ABSTRACT Preliminary experimental flow regime types have been observed for partial and full conde... more ABSTRACT Preliminary experimental flow regime types have been observed for partial and full condensation in a horizontal channel of millimeter scale. Effects of hydrostatic pooling, wall vibrations, vapor flow pulsations, and solid-liquid-vapor contact on the top surface of the condenser are observed. Wave phenomena such as wave reflection, standing waves, and waves on the interface of vapor bubbles are presented in 2 and 3 dimensions. Due to the high density and low kinematic viscosity of the liquid phase of the fluid (perfluorohexane), the effects observed are primarily inertial. It is found that in these flows pressure pulsation and surface tension effects very strongly influence the morphology of the interface where it contacts the top wall. Wall vibrations contribute to standing waves on the interface. This investigation outlines some of the types of flow one might expect to encounter in a millimeter scale horizontal condenser with wall vibration and pressure pulsation where inertial effects dominate the liquid flow.
2019 ASEE Annual Conference & Exposition Proceedings
2020 ASEE Virtual Annual Conference Content Access Proceedings
Proceeding of Second Thermal and Fluids Engineering Conference
Proceeding of Second Thermal and Fluids Engineering Conference
Preliminary experimental flow regime types have been observed for partial and full condensation i... more Preliminary experimental flow regime types have been observed for partial and full condensation in a horizontal channel of millimeter scale. Effects of hydrostatic pooling, wall vibrations, vapor flow pulsations, and solid-liquid-vapor contact on the top surface of the condenser are observed. Wave phenomena such as wave reflection, standing waves, and waves on the interface of vapor bubbles are presented in 2 and 3 dimensions. Due to the high density and low kinematic viscosity of the liquid phase of the fluid (perfluorohexane), the effects observed are primarily inertial. It is found that in these flows pressure pulsation and surface tension effects very strongly influence the morphology of the interface where it contacts the top wall. Wall vibrations contribute to standing waves on the interface. This investigation outlines some of the types of flow one might expect to encounter in a millimeter scale horizontal condenser with wall vibration and pressure pulsation where inertial ef...
Heat Transfer, Part B, 2005
The flow and heat transfer rates inside a condenser depend on the specification of inlet, wall, a... more The flow and heat transfer rates inside a condenser depend on the specification of inlet, wall, and exit conditions. For steady/quasi-steady internal condensing flows, the vapor's ability to sense exit condition and, for certain exit conditions, even change its density (despite low Mach numbers) allows the flow to have a rather significant dependence on conditions downstream of the condenser. The change in flows due to change in exit conditions is usually accompanied by significant changes in interfacial mass transfer rates and associated locations of the interface. Both experimental and direct computational simulation results presented here show that this is indeed the case for a large class of flows of pure vapor experiencing film condensation on the inside walls of a vertical tube. In applications, the totality of boundary conditions is determined not only by the condenser; but also by the flow-loop (or the system)-of which the condenser is only a part. Therefore, the results outlined here should contribute towards a better understanding of the behavior (particularly the extent to which flow "ellipticity" and vapor compressibility affect the flow regimes of operation-i.e. annular, plug/churn, etc.) and response of condensers (transients due to start-up, system instabilities, etc.) in different application systems (e.g. Rankine Cycle Power Plants, Capillary Pumped Loops, Looped Heat Pipes, Thermal Management Systems, etc.). In this connection, two experimental examples of relevant system instabilities are also presented here. In summary, the experimental results presented here, and the computational results summarized here but presented elsewhere, reinforce the fact that there exist multiple steady solutions (with different heat transfer rates) for different exit conditions. However under certain flow situations there exists a "natural" steady flow with a "natural" exit condition. This happens if the vapor flow is seeking a specific exit condition and the conditions downstream of the condenser allow the vapor the choice to select it.
ASME 2009 Second International Conference on Micro/Nanoscale Heat and Mass Transfer, Volume 2, 2009
This paper presents computational simulations for internal condensing flows over a range of tube/... more This paper presents computational simulations for internal condensing flows over a range of tube/channel geometries ranging from one micro-meter to several millimeters in hydraulic diameters. Over the mm-scale, three sets of condensing flow results are presented that ...
International Journal of Heat and Mass Transfer, 2011
Annals of the New York Academy of Sciences, 2006
This article presents accurate numerical solutions of the full 2D governing equations for steady ... more This article presents accurate numerical solutions of the full 2D governing equations for steady and unsteady laminar/laminar internal condensing flows of pure vapor (FC-72 and R-113) inside a vertical tube and a channel. The film condensation is on the inside wall of a tube or one of the walls of a channel (the lower wall in case of a downward sloping channel). Both experiments and simulations find that exit condition specifications are important. The computations are able to predict whether or not a steady flow exists with a well-defined and steady natural exit condition. If well-defined natural steady/quasi-steady flows exist-as is shown to be the case for gravity-dominated or strong shear-dominated condensate flows that remain parabolic up to the exit location-the computations are able to predict both the natural exit condition and any point of transition (from stable to unstable or smooth to wavy behavior) that may exist within this zone. Compared to gravity-driven cases, shear-driven cases (zero gravity or horizontal cases) tend to destabilize easily. It is found that only for gravity-driven cases interfacial waves are able to cause a concurrent enhancement in heat transfer rates along with an enhancement in interfacial shear. Also it is found that this enhancement in interfacial wave energy is significant if the condensing surface noise is in resonance with the intrinsic waves.
Annals of the New York Academy of Sciences, 2009
Reported experimental and computational results confirm that both the flow features and heat tran... more Reported experimental and computational results confirm that both the flow features and heat transfer rates inside a condenser depend on the specification of inlet, wall, and exit conditions. The theoretical and experimental results presented in this paper allow us to propose important exit condition based categorization of these flows. Of these, category II flows are defined to be cases for which exit pressures are left unspecified. However it is shown here that steady flows under specified exit pressure conditions (category I flows) are more stable and can be more easily achieved under all conditions (normal or zero-gravity). Existence of self-selected exit pressure conditions for unspecified exit condition cases (category II flows) are more difficult to achieve and are often limited to gravity driven flows. In practice, however, special hardware arrangements are required for repeatable realization of both these categories of flow. If this is not so, one often has an inadvertent category I flow (flows with specified exit pressure) without the explicit knowledge of the exit pressure value. For microgravity situations, the remedy is to run condensers under suitably specified inlet and exit pressures (category I conditions) as well as a proper cooling strategy (i.e., proper wall temperature variations).
Journal of Heat Transfer, 2007
Reported experimental and computational results confirm that both the flow features and heat-tran... more Reported experimental and computational results confirm that both the flow features and heat-transfer rates inside a condenser depend on the specification of inlet, wall, and exit conditions. The results show that the commonly occurring condensing flows’ special sensitivity to changes in exit conditions (i.e., changes in exit pressure) arises from the ease with which these changes alter the vapor flow field in the interior. When, at a fixed steady mass flow rate, the exit pressure is changed from one steady value to another, the changes required of the interior vapor flow toward achieving a new steady duct flow are such that they do not demand a removal of the new exit pressure imposition back to the original steady value—as is the case for incompressible single phase duct flows with an original and “required” exit pressure. Instead, new steady flows may be achieved through appropriate changes in the vapor/liquid interfacial configurations and associated changes in interfacial mass,...