Latent Heat Of Condensation Research Articles

The optimum shape for converting rectangular fins when condensation occurs

There may be condensation on the fin surfaces of the air conditioning systems due to the temperature of the fin surfaces being below the dew point temperature of the water vapor in the surrounding air. Heat and mass transfer occur from the saturated air layer to the liquid water film and the latent heat of condensation is transferred to the fin. This study presents a quasilinearization solution for vertical rectangular fins when condensation occurs, assuming that the average convective heat and mass transfer coefficients are constant along the height of the fin. Rectangular fins with and without condensation on the surface have been compared and optimum fin dimensions have been given. The optimum fin length, the fin effectiveness and the average fin temperature in the case of condensation were found to be smaller than in the case of no condensation.

On the Diagnosis and Conservation of Energy During Condensation

Abstract The diagnosis and conservation of energy during condensation is examined. It is shown that the latent enthalpy, when defined in conjunction with the individual enthalpies of water vapor and liquid water, cannot be a function of the latent heat of condensation L but a modified value (L′) which is ∼30% larger than L. The additional energy represented in L′ can be thought of as a necessary absorption by the liquid water to bring the post-condensation air-vapor-liquid system into thermal equilibrium. The difference between L′ and L is a function of the difference in specific heats of water vaper and liquid water. If we assume that (Cpd−Cpr is constant, as is required in our energy conservation derivation, L′ is shown to vary by only 0.59% when computed over the range −50 to +60°C; a representative value for L' is 3.142×106 J Kg−1

The effect of latent heat from moist air on the vortex in a tornado-type wind energy generator system

A local-similarity method is presented for the equations that describe a vortex, which is generated by a stationary tower with a partly opening top, directed by vertical vanes, and which is affected by the latent heat of condensation from moist air which creates a buoyant force.

Vapor phase nucleation and growth of menthol on carbon, glass and fuzed quartz substrates

The morphology of the hetero-epitaxy of menthol on carbon, fuzed quartz and glass substrates is investigated for inert gas transport vapor deposition. Substrate temperatures of 22–24°C are utilized, some 19°C less than the melting temperature of menthol. Formation of an intermediate lifetime liquid menthol drop state is observed, which has a significant effect on deposit growth morphology. It is suggested that liquid supercooling, latent heat of condensation and low thermal conductivity to the substrate all contribute to maintenance of the liquid state with connective turbulence causing fluctuations in instantaneous heat of condensation input to menthol nuclei by modulating local flux rates. Formation of the observed intermediate liquid stage tends to decrease initial sticking coefficient and results in deposit growth by menthol crystallite stacking, branching and network formation. A related morphological growth mechanism was first discussed by Wagner and Ellis for whisker development in the vapor-liquid-solid deposition of silicon. There are significant differences in the mechanisms and parameters important to the actual formation of the liquid state, however, and consequently the growth morphology for menthol is much more complex.

An experiment in forecasting with diabatic baroclinic model over India and neighbourhood

This paper contains the results of experiments in forecasting the flow patterns over India and neighbourhood at 850, 700, 500 and 300-mb levels with the help of a four-layer quasi-geostrophic diabatic model. The effects of the ground contour, latent heat of condensation and radiation have been taken into account for computation of the vertical velocity UJ. To bring out the salient features of the model in this paper, we present the results of a case study.

Conditions for normal summer monsoon rainfall and causes of droughts over western India

Model for the Arabian Sea summer monsoon proposed by Ramage ( 1969) and his conclusions about drought of 1899 in western India have been discussed. The heat-low over Pakistan and the air from across the equator drawn north and northeastwards which helps development of the trough over the Gangetic valley under the influence of the topographical features of the subcontinent, are considered the primary causes responsible for the setting up of monsoon circulation upto about 600 mb and the latent heat of condensation would not appear to play any significant role in the same.

Surface chemistry of polymers. The adsorption of carbon dioxide and sulfur dioxide on polyvinylidene chloride

AbstractIsotherms for the adsorption of nitrogen (77 K), carbon dioxide (195–247 K) and sulfur dioxide (254–293 K) on polyvinylidene chloride have been measured volumetrically. The B.E.T. cross‐sectional areas of 18 Å2 (CO2) and 24 Å2 (SO2) are comparable to liquid density values. The isosteric heat of adsorption of CO2 is constant for 0.2 < θ < 0.4 and is lower than the latent heat of condensation. For SO2, the two are practically identical up to the monolayer. Entropy calculations show ‘supermobility’ in the case of CO2.

On the numerical solution of diabatic quasi-geostrophic Omega equation

The quasi-geostrophic omega equation has been numerically solved to get the vertical velocity distribution in a typical westerly disturbance. The effects of sensible heat and latent heat of condensation are also for a 4-layer model. The computations were performed on HITAC 5020.
 The numerically obtained vertical velocity field is in good agreement with the observed weather pattern associated with the middle latitude large-scale disturbance, i.e., ascending motion in front of the trough and downward motion in the rear of the trough.

A Moist, Hadley Cell Model for Jupiter's Cloud Bands

Abstract A steady symmetric flow model is used to study the hypothesis that Jupiter's banded structure represents a variable concentration of condensing constituents with latitude. The flow is consistent with the suggestion by Ingersoll and Cuzzi that Zones are warmer than Belts and that the zonal flow is geostrophic. The driving for the flow is latent heat of condensation and is localized within the bands. No equator-to-pole temperature gradient is assumed. It is found that the atmosphere is in local radiative-convective equilibrium to a first approximation. Variations in moisture content with latitude modify the adiabatic lapse rate and induce thermal winds. The requirement that the stratosphere-troposphere interface be stress free produces an Ekman layer, which through Ekman suction controls the meridional flow. The net effect of meridional motions is to advect entropy away from the cloudiest bands, and for a steady state some radiative mechanism must provide net heating at these locations. The steady ...

Observational studies of the general circulation of the Tropics: long term mean values

AbstractData from 298 stations between 45°N and 30°S have been processed for the period July 1957 to December 1964. The mean wind and temperature fields are presented together with the momentum and heat fluxes for two three month seasons, December‐February and June‐August. The tropospheric results were obtained from objective analysis of the long term station means and the stratospheric results from latitude band means giving equal weight to data from odd and even years so that the biennial component has been virtually eliminated.The mean temperature cross‐sections show little seasonal variation in the tropical troposphere and gradients are small. The maximum temperature is in the vicinity of 5°S during the southern summer but moves to 20°N during June‐August as a consequence of stronger heating over the continents. In the tropical stratosphere the seasonal variation is from lower temperatures in December‐February to higher temperatures in June‐August. The mean zonal wind pattern shows the tropical easterlies to be stronger and to occupy a greater range of latitudes in the upper troposphere during June‐August. The Hadley circulation obtained appears quite reasonable with the winter hemisphere cell predominating and extending over the Equator.Although all three components of the momentum flux were evaluated for the troposphere, only the transient eddy contribution could be obtained for the stratosphere. A strong flux is observed in the upper equatorial troposphere directed into the summer hemisphere. The sensible heat‐flux in the middle troposphere is equatorward in the Tropics of both hemispheres and a small transport into the summer hemisphere is noted. This equatorward flux is countergradient in both hemispheres except during the northern summer. The mean motion transport of total energy is about an order of magnitude larger than the eddy transport at the Equator and supplies energy to the winter hemisphere.The zonal and eddy forms of kinetic energy and available potential energy have been evaluated for the tropical troposphere together with all conversions between them except for that by transient eddies between available potential energy and kinetic energy. On the average, kinetic energy contents are about twice as large as available potential energy contents and the momentum flux conversions are larger than those involving heat fluxes. The conversion by the mean motions, however, is largest of all over the range 24°N‐24°S and leads to a rejuvenation time of some 3–5 days for the zonal kinetic energy. This conversion appears to be sufficiently large to offset the destruction in middle latitudes.Taken together, the results presented here give a consistent pattern for the tropical circulation. The direct Hadley cell is seen as a source of both heat and momentum which are distributed by the eddy fluxes. The energy supply for the mean cell is thought to be the latent heat of condensation in its ascending branch.

On the large scale motion in the tropics with latent heat due to condensation

A scale analysis for the large scale tropical motions with diabatic heating due to the latent heat of condensation is given. The analysis shows that the diabatic heating term in the thermodynamic energy equation becomes important when the rainfall rate is equal or greater than 2 mm per day.

Comments on “The Release of Latent Heat of Condensation in a Simple Precipitation Forecast Model”

Comments on “The Release of Latent Heat of Condensation in a Simple Precipitation Forecast Model”

The Release of Latent Heat of Condensation in a Simple Precipitation Forecast Model

Abstract A method is proposed for deriving a useful quantitative precipitation forecast from a physical model in which no account is taken of the release of latent heat of condensation. The approach is to calculate, on the basis of a simple theory, the ratio between the large-scale updraft speed when the latent heat is incorporated and the smaller updraft speed when it is not. The resulting ratio is then assumed to be equivalent to the ratio of the storm-average precipitation to the comparable smaller average computed from the thermodynamically dry model. An empirical test supports the assumption reasonably well for large winter storms in the central and eastern United States. For operational purposes it is suggested that the theoretical ratio be estimated statistically from the mean temperature of the layer from 1000 mb to 500 mb. Evidence is provided that this estimate can be made fairly successfully. Finally, some inferences are drawn concerning the role of cumulus convection in this type of storm.

James Espy and the Beginnings of Cloud Thermodynamics

The work of the nineteenth-century American meteorologist, James P. Espy, is discussed in relationship to the early development of understanding of the thermodynamics of clouds and the dynamics of convection. Espy was the first to recognize the important role of release of latent heat of condensation in sustaining cloud and storm circulations.

Convection in Conditionally Unstable Atmosphere

The analysis has shown that if the stratification is unstable for ascending motion over an infinite area and stable for descending motion, and small random perturbations of various scales are introduced, the final disturbance evolved will have the dimension of a cumulus cloud. The stable stratification in the descending region has the effect of increasing the critical lapse-rate and narrowing the ascending region and making the descending motion widespread, so that the centers of the ascending regions are further apart. The distance estimated from the theoretical analysis agrees favorably with those obtained from satellite observations. The distributions of the various perturbation quantities pertaining to a circular symmetrical disturbance have been obtained. They show many resemblances to the corresponding distributions in tropical storms. Since the main source of energy of the mature tropical storms is the latent heat of condensation, it is really tempting to attribute the formation of these large-scale disturbances directly to convection in conditionally unstable air. However, the analysis shows that some organizing mechanisms are needed in order to channel the release of the energy of unstable stratification into a large scale circulation. DOI: 10.1111/j.2153-3490.1961.tb00107.x

A NUMERICAL EXPERIMENT ON THE DEVELOPMENT OF A TROPICAL CYCLONE

Abstract A model of a tropical cyclone is constructed which is based upon conservation of momentum, mass,water vapor and heat in the hydrostatic system. The horizontal and vertical eddy-exchange processes for momentum, moisture and heat are included in the equations in order to incorporate the planetary frictional (Ekman) layer into the model. The effects of the surface boundary (Prandtl) layer are simulated by the boundary conditions for the equations, which permit the evaluation of surface stress, the sensible heat transport and the evaporation of water vapor from the earth surface. The energy sources of the model are the latent heat of condensation released during the ascent of moist air and the sensible heat transported from the ocean surface. The formulation of the finite-difference equations for the axially-symmetric case is presented, together with an examination of the computational stability. By means of a high-speed computer, two independent computations with and without the supply of latent hea...

Inclusion of fluorine compounds in faujasite II. Heats of sorption

Heats of inclusion in faujasite have been evaluated for CF 4 , C 2 F 6 , C 3 F 8 , n -C 4 F 10 , SF 6 , C 2 F 4 Cl 2 , and perfluorodimethyl cyclo hexane. In the case of CF 4 , C 2 F 6 , C 3 F 8 and SF 6 the degree of filling, θ, of the intracrystalline volume was in the range 0.05 to 0.9; for the more condensable molecules this range was more restricted. The sorbate-lattice interaction appears to be independent of the amount included, at least over a considerable range in θ, and is dominated by dispersion and repulsion energy contributions. As the amount of included material increases this interaction is augmented by a self-potential between sorbate molecules, the magnitude of which can be given a reasonable physical explanation. The maximum values of ─ ∆ H , where ∆ H is the inclusion heat, are several times larger than the latent heat of condensation of the liquids. Much of this difference arises from the different mechanisms of vaporization from the permanent, honeycomb structure of the crystals and from a liquid, respectively. Over the narrow range in θ where extracrystalline capillary condensation begins to replace intracrystalline sorption the heats of uptake depend on temperature. Heats of inclusion of fluoro-carbons are appreciably higher than those of corresponding hydrocarbons.

Heat Transfer by Film Condensation : An Approximate Theory of Laminar-Film Condensation on a Vertical Wall

An approximate theory, accounted for the effects of both energy convection and fluid acceleration within the film condense layer, is reported in this paper and the similar method (Karman-Pohlhausen's method) to the heat transfer by free convection has been used also for the laminarfilm condensation on a vertical wall. Heat transfer results are expressed by the following simple equations and indicate a good agreement with the numerical exact solutions for special Prandtl numbers, which have been given by Sparrow and Gregg recently. (I) for high Prandtl numbers [numerical formula] (II) for low Prandtl numbers [numerical formula] where β is a functon of Prandtl number and of cΔT/hfg and is given by Figs. 2 and 3. The symbols used in the above equations are as follows : Nux : local Nusselt number, k : thermal conductivity, hfg : latent heat of condensation, c : specific heat, ΔT=Tsat-Tw ; Tsat : saturation temperature, Tw : wall temperature, g : acceleration due to gravity, ν : kinematic viscosity, ρ : condesate density, ρv : vapor density, x : distance measuring along wall from leading edge.

Adsorption properties of carbon adsorbents

1. The isosteres of the adsorption of benzene for activated charcoals with various microporous structures, calculated according to the theory of volume filling of micropores, is in good agreement with the experimental data within the range of temperatures and equilibrium pressures studied. 2. The adsorption isosteres for activated charcoals with a narrow distribution of micropores are practically linear. A wide distribution of micropores in activated charcoals is manifested in a curvature of the isosteres in the middle region of fillings of the volume of the adsorption space in the case when the parameters B of the first and second microporous structures approximating the distribution differ substantially. 3. The virtual linearity of the adsorption isosteres does not exclude a dependence of the differential heats of adsorption on the temperature, which is intensified when the change in the latent heat of condensation with the temperature is taken into consideration. 4. Two methods of calculating the differential entropy of adsorption were considered and the nature of the dependence of the entropy on the values of the adsorption and temperature was discussed.

Study on Vacuum Deposition of Metals, I On the Formation of Alloys by Successive Deposition of Constituent Metal Vapours in Vacuum

The formation of alloy phases by successive deposition of constituent metal vapours in vacuum was investigated by electron diffraction method for some binary alloy systems. It was concluded that the temperature of the surface layer of primary deposit is raised by the deposition of secondary metal vapour. This temperature rise, which contributes to the formation of alloy phases, is mainly due to the latent heat of condensation of the metal vapour which deposits on the substrate, and consequently metal pairs which have larger latent heat of condensation may form alloys easier than those which have smaller ones. It was also suggested that some structural defects in the substrate layer would contribute to the formation of alloy phases.