Search

Search Results

• 1. [Article] Studies of homogeneous nucleation and transient heat transfer in cryogenic liquids

  We report the results of a series of experimental studies in two interrelated areas: homogeneous nucleation and transient heat transfer in cryogenic liquids. We report the first determination of the homogeneous ...

  Citation × Citation Citation Abstract Copy Title: Studies of homogeneous nucleation and transient heat transfer in cryogenic liquids Author: Sinha, Dipen N. Year: 1980 We report the results of a series of experimental studies in two interrelated areas: homogeneous nucleation and transient heat transfer in cryogenic liquids. We report the first determination of the homogeneous nucleation temperature of liquid helium I and liquid nitrogen employing a transient superheating technique. This technique in liquid helium involved the development of a new transient magnetoresistive thermometer which relies on the strong temperaure dependence of magnetoresistance in bismuth as a thermometric property. Our measurements of the homogeneous nucleation temperature for both liquid helium I and nitrogen are in good agreement with the predictions from the Becker-Doring Volmer-Zel'dovich-Frenkel nucleation theory. On the basis of such agreement between theory and experiment in both liquid helium and liquid nitrogen we have developed a corresponding state analysis applicable to the case of homogeneous nucleation in liquid noble gases, both quantum and classical. Predictions of the homogeneous nucleation temperature and surface tension of several hydrogen isotopes are made from such a quantum mechanical law of corresponding states. We also comment on the limiting superheat temperature of liquid helium I. It is suggested that a comparison between the limiting superheat temperaure and the peak nucleate boiling temperature is meaningless and that the reported agreement between the two is largely fortuitous. In the studies of transient heat transfer in helium we find that the heat transfer from a solid into liquid helium is markedly enhanced by the application of a visible pulse of light. In liquid nitrogen we find that a transition to stable film boiling can be observed for power values as low as 40 per cent of the steady-state peak heat flux. Title: Studies of homogeneous nucleation and transient heat transfer in cryogenic liquids Author: Sinha, Dipen N. Year: 1980 We report the results of a series of experimental studies in two interrelated areas: homogeneous nucleation and transient heat transfer in cryogenic liquids. We report the first determination of the homogeneous nucleation temperature of liquid helium I and liquid nitrogen employing a transient superheating technique. This technique in liquid helium involved the development of a new transient magnetoresistive thermometer which relies on the strong temperaure dependence of magnetoresistance in bismuth as a thermometric property. Our measurements of the homogeneous nucleation temperature for both liquid helium I and nitrogen are in good agreement with the predictions from the Becker-Doring Volmer-Zel'dovich-Frenkel nucleation theory. On the basis of such agreement between theory and experiment in both liquid helium and liquid nitrogen we have developed a corresponding state analysis applicable to the case of homogeneous nucleation in liquid noble gases, both quantum and classical. Predictions of the homogeneous nucleation temperature and surface tension of several hydrogen isotopes are made from such a quantum mechanical law of corresponding states. We also comment on the limiting superheat temperature of liquid helium I. It is suggested that a comparison between the limiting superheat temperaure and the peak nucleate boiling temperature is meaningless and that the reported agreement between the two is largely fortuitous. In the studies of transient heat transfer in helium we find that the heat transfer from a solid into liquid helium is markedly enhanced by the application of a visible pulse of light. In liquid nitrogen we find that a transition to stable film boiling can be observed for power values as low as 40 per cent of the steady-state peak heat flux. Close

• 2. [Article] Studies of nucleation and heat transfer in liquid helium isotopes 3 and 4

  We report the results of a series of experiments in three interrelated areas: light induced nucleation of vapor bubbles in superheated liquid helium 4, transient heat transfer in liquid helium isotopes ...

  Citation × Citation Citation Abstract Copy Title: Studies of nucleation and heat transfer in liquid helium isotopes 3 and 4 Author: Lezak, David Year: 1985 We report the results of a series of experiments in three interrelated areas: light induced nucleation of vapor bubbles in superheated liquid helium 4, transient heat transfer in liquid helium isotopes 3 and 4, and homogeneous nucleation of vapor bubbles in superheated liquid helium 3. This work has resulted in significant contributions in each of these particular areas. Our transient heat transfer work has resulted in extremely high temperature measurements of the Kapitza thermal boundary conductance limits in helium 3 and 4, in measurements of the delay time to the onset of film boiling over a wide range of bath temperatures in helium 4, and in a determination of bubble growth rates in helium 4. These measurements have been compared with theory and have in some cases allowed the extension or elucidation of that theory. We have characterized the so called "light effect" and established photographically that small amounts of visible light will cause the formation of vapor bubbles at the interface of a solid and superheated liquid helium 4 and that this vapor can influence the quasi-steady-state heat flux vs temperature hysteresis curve. Finally, we have measured the homogeneous nucleation temperature of liquid helium 3 and found good agreement with the predictions of the Becker-Doring-Volmer-Zel'dovich Frenkel nucleation theory. This work is shown to have applications to practical cryogenic engineering, to further understanding of basic heat transfer and nucleation theory, and to practical and theoretical environmental and resource considerations. Title: Studies of nucleation and heat transfer in liquid helium isotopes 3 and 4 Author: Lezak, David Year: 1985 We report the results of a series of experiments in three interrelated areas: light induced nucleation of vapor bubbles in superheated liquid helium 4, transient heat transfer in liquid helium isotopes 3 and 4, and homogeneous nucleation of vapor bubbles in superheated liquid helium 3. This work has resulted in significant contributions in each of these particular areas. Our transient heat transfer work has resulted in extremely high temperature measurements of the Kapitza thermal boundary conductance limits in helium 3 and 4, in measurements of the delay time to the onset of film boiling over a wide range of bath temperatures in helium 4, and in a determination of bubble growth rates in helium 4. These measurements have been compared with theory and have in some cases allowed the extension or elucidation of that theory. We have characterized the so called "light effect" and established photographically that small amounts of visible light will cause the formation of vapor bubbles at the interface of a solid and superheated liquid helium 4 and that this vapor can influence the quasi-steady-state heat flux vs temperature hysteresis curve. Finally, we have measured the homogeneous nucleation temperature of liquid helium 3 and found good agreement with the predictions of the Becker-Doring-Volmer-Zel'dovich Frenkel nucleation theory. This work is shown to have applications to practical cryogenic engineering, to further understanding of basic heat transfer and nucleation theory, and to practical and theoretical environmental and resource considerations. Close

• 3. [Article] Nucleation and Heat Transfer in Liquid Nitrogen

  With the advent of the new" high Tc superconductors as well as the increasing use of cryo-cooled conventional electronics, liquid nitrogen will be one of the preferred cryogens used to cool these materials. ...

  Citation × Citation Citation Abstract Copy Title: Nucleation and Heat Transfer in Liquid Nitrogen Author: Roth, Eric Year: 1993 With the advent of the new" high Tc superconductors as well as the increasing use of cryo-cooled conventional electronics, liquid nitrogen will be one of the preferred cryogens used to cool these materials. Consequently, a more thorough understanding of the heat transfer characteristics of liquid nitrogen is required. In these investigations the transient heating characteristics of liquid nitrogen to states of nucleate and film boiling under different liquid flow conditions are examined. Using a metal hot wire/plate technique, it is verified that there is a premature transition to film boiling in the transient case at power levels as much as 30 percent lower than under steady state nucleate boiling conditions. It is also shown that the premature transition can be reduced or eliminated depending on the flow velocity The second part of this research analyses the nucleation (boiling) process from a dynamical systems point of view. By observing how the boiling system variables evolve and fluctuate over time, it is hoped that physical insight and predictive information can be gained. One goal is to discover some indicator or signature in the data that anticipates the transition from nucleate boiling to film/boiling. Some of the important variables that make up the boiling system are the temperature of the heater and the heat flux through the heater surface into the liquid nitrogen. Results, gained by plotting the system’s trajectory in the heat flux-temperature plane, are that on average the system follows a counterclockwise trajectory. A physical model is constructed that explains this behavior. Also, as the applied heater power approaches levels at which the transition to film is known to occur, the area per unit time swept out in the heat flux-temperature plane is seen to reach a maximum. This could be of practical interest as the threshold to film boiling can be anticipated and possibly prevented. Title: Nucleation and Heat Transfer in Liquid Nitrogen Author: Roth, Eric Year: 1993 With the advent of the new" high Tc superconductors as well as the increasing use of cryo-cooled conventional electronics, liquid nitrogen will be one of the preferred cryogens used to cool these materials. Consequently, a more thorough understanding of the heat transfer characteristics of liquid nitrogen is required. In these investigations the transient heating characteristics of liquid nitrogen to states of nucleate and film boiling under different liquid flow conditions are examined. Using a metal hot wire/plate technique, it is verified that there is a premature transition to film boiling in the transient case at power levels as much as 30 percent lower than under steady state nucleate boiling conditions. It is also shown that the premature transition can be reduced or eliminated depending on the flow velocity The second part of this research analyses the nucleation (boiling) process from a dynamical systems point of view. By observing how the boiling system variables evolve and fluctuate over time, it is hoped that physical insight and predictive information can be gained. One goal is to discover some indicator or signature in the data that anticipates the transition from nucleate boiling to film/boiling. Some of the important variables that make up the boiling system are the temperature of the heater and the heat flux through the heater surface into the liquid nitrogen. Results, gained by plotting the system’s trajectory in the heat flux-temperature plane, are that on average the system follows a counterclockwise trajectory. A physical model is constructed that explains this behavior. Also, as the applied heater power approaches levels at which the transition to film is known to occur, the area per unit time swept out in the heat flux-temperature plane is seen to reach a maximum. This could be of practical interest as the threshold to film boiling can be anticipated and possibly prevented. Close