Latent heat

About: Latent heat is a research topic. Over the lifetime, 13503 publications have been published within this topic receiving 302811 citations.

Nucleation, crystal growth and the thermal regime of cooling magmas

Abstract: Crystallization at the margin of a quiet cooling magma has been studied numerically, taking into account the kinetics of crystallization. The variables are the latent heat value, the growth and nucleation functions, the initial magma temperature, and the thermal contrast between magma and country rock. We have investigated a wide range of values for these parameters corresponding to natural conditions. We show that after a highly transient stage, crystallization tends toward an equilibrium between heat production (latent heat release) and heat loss. Given the small diffusivity of country rocks, latent heat release is the main factor controlling the temperature evolution. In order to minimize the latent heat release, crystallization occurs at a temperature where nucleation is small. This can be close to either the liquidus or the solidus, depending on the initial conditions. The main process controlling crystallization is nucleation and not crystal growth. Nucleation occurs as a series of sharp pulses followed by longer periods of crystal growth. The nucleation pulses give birth to thermal oscillations. These oscillations can be sustained if the interior magma temperature is above the liquidus independently of the heat loss mechanism. We show that the phenomenon occurs on the scale of a few centimeters which corresponds to the inch-scale layering of many ultrabasic complexes. The model allows us to calculate crystal sizes which are in good agreement with geological observations. The crucial parameters which determine crystal size variations near the margins of igneous bodies are the initial thermal conditions as well as the nucleation and growth functions. In the main cooling regime close to the liquidus, significant size variations can be created by small thermal disturbances.

An Experimental and Thermodynamic Investigation of the Hydrogen-Titanium System

Abstract: The temperature-pressure-concentration relationships of the hydrogen-titanium system have been studied, and its more important thermodynamic aspects considered. Part of the equilibrium diagram has been established, and free-energy curves for the α- and β -solutions have been plotted for a number of temperatures. The experimental results have been used to obtain values for the latent heat of the α ⇌ β transformation and the transformation temperature.

Relative role of dynamic and thermodynamic processes in the development of the Indian Ocean dipole: An OGCM diagnosis

Abstract: [1] The relative role of oceanic dynamics and surface heat fluxes in the initiation and development of the Indian Ocean dipole was investigated by analyzing results from an oceanic general circulation model. The model was forced by observed surface wind stress and heat flux fields for 1958–1997. The results show that it was capable of reproducing observed dipole events over the tropical Indian Ocean. The diagnosis of the mixed-layer heat budget indicates that the SST anomaly (SSTA) in the east pole is primarily induced by anomalous surface latent heat flux and vertical temperature advection, whereas in the west pole it is mainly caused by meridional and vertical temperature advection anomalies. In both regions shortwave radiation anomalies tend to damp the SSTA. The ocean Rossby waves are essential in linking the anomalous wind and SST off Sumatra and subsurface temperature variations in southwest Indian Ocean.