Subcooling

About: Subcooling is a(n) research topic. Over the lifetime, 6150 publication(s) have been published within this topic receiving 99125 citation(s).

Convective boiling and condensation

Abstract: Introduction 1. The basic models 2. Empirical treatments of two-phase flow 3. Introduction to convective boiling 4. Subcooled boiling heat transfer 5. Void fraction and pressure drop in subcooled boiling 6. Saturated boiling heat transfer 7. Critical heat flux in forced convective flow - 1. Vertical uniformly heated tubes 8. Critical heat flux in forced convective flow - 2. More complex situations 9. Condensation 10. Conditions influencing the performance of boiling and condensing systems 11. Multi-component boiling and condensation Appendix Index

A general correlation for flow boiling in tubes and annuli

Abstract: A new general correlation for forced convection boiling has been developed with the aid of a large data bank. This data bank consists of over 4300 data points for water, refrigerants and ethylene glycol, covering seven fluids and 28 authors, mostly for saturated boiling in vertical and horizontal tubes, but with significant information also for subcooled boiling and for annuli. The new correlation is simpler to apply and overall gives a closer fit to the data than existing correlations. The mean deviation between the calculated and measured boiling heat transfer coefficient is 21.4% for saturated boiling and 25.0% for subcooled boiling.

On the Size Range of Active Nucleation Cavities on a Heating Surface

Abstract: The importance of surfare condition on nucleate boiling has long been recognized. It has also been known that only cavities of a narrow size range can be active nucleation sites. In order to define the size range of active cavities as a function of wall temperature or heat flux, a model is proposed. The model pictures a bubble nucleus at a site enveloped by a warm liquid. The nucleus will begin to grow into a bubble only when the surrounding liquid is sufficiently superheated. The time required for the liquid to attain this superheat is called the waiting period. The transfer of heat from the superheated liquid into the bubble is considered to be a transient conduction process. A cavity is considered effective only if the waiting period is finite. This criterion gives the limiting sizes of effective cavities. The equations show that maximum and minimum sizes of effective cavities are functions of subcooling, pressure of the system, physical properties, and the thickness of the superheated liquid layer. Comparison of theoretical prediction with experimental data from several sources was made. The fluids considered were ether, pentane, and water, with water under various degrees of subcooling. The theory did predict the incipience of boiling and size range of cavities successfully.

A general correlation for saturated and subcooled flow boiling in tubes and annuli, based on a nucleate pool boiling equation

Abstract: Recent accurate correlations for predicting the heat transfer coefficient in saturated flow boiling all contain an empirical boiling number correction. The original idea behind the boiling number correction was to allow for the enhancement of the forced eonvective heat transfer mechanisms arising from the generation of vapour in the boundary layer next to the wall. However, the presence of the boiling number term appears to prevent application to subcooled boiling, throwing doubt on the physical basis of the correlation. This paper shows that the eonvective term in the correlation should have a Prandtl number dependence. In this way an accurate predictive method covering a very wide range of parameters is constructed with an explicit nucleate boiling term and without boiling number dependence.

A Theoretical model to predict pool boiling CHF incorporating effects of contact angle and orientation

Abstract: A theoretical model is developed to describe the hydrodynamic behavior of the vapor-liquid interface of a bubble at the heater surface leading to the initiation of critical heat flux (CHF) condition. The momentum flux resulting from evaporation at the bubble base is identified to be an important parameter. A model based on theoretical considerations is developed for upward-facing surfaces with orientations of 0 deg (horizontal) to 90 deg (vertical). It includes the surface-liquid interaction effects through the dynamic receding contact angle. The CHF in pool boiling for water, refrigerants and cryogenic liquids is correctly predicted by the model, and the parametric trends of CHF with dynamic receding contact angle and subcooling are also well represented