Showing papers on "Latent heat published in 1970"
TL;DR: In this article, the reliability of the energy balance and lysimetric methods for measuring evaporation has been examined in experiments in a field of wheat using a weighing lysimeter.
85 citations
TL;DR: In this article, the authors describe a representation of the distribution of sensible and latent heat from the surface through the atmospheric boundary layer which has been formulated for use in a 10-level primitive equation model atmosphere.
Abstract: This paper describes a representation of the distribution of sensible and latent heat from the surface through the atmospheric boundary layer which has been formulated for use in a 10-level primitive equation model atmosphere. The transfer process is represented in two parts : (i) the transfer of energy across the Earth's surface into the lowermost 100 mb layer of the model atmosphere; and (ii) the subsequent redistribution of this energy through two or more such layers by small-scale convection. The fluxes of energy across the surface are calculated using empirical ‘bulk aerodynamic’ relationships. In land regions consideration of the energy balance at the surface is also necessary, and diurnal variations of radiation are taken into account. The redistribution of energy by small-scale convection is represented by convective adjustments which ensure that a certain neutral lapse rate of temperature is never exceeded. Some results of the incorporation of these effects into the 10-level model are described.
74 citations
Journal Article•
TL;DR: In this article, a heat-transfer model was developed for a multilayered PAVEMENT system to evaluate the effect of different types of weather conditions on the performance of the system.
Abstract: A HEAT TRANSFER MODEL FOR EVALUATING FROST ACTION AND TEMPERATURE-RELATED EFFECTS WAS DEVELOPED FOR A MULTI-LAYERED PAVEMENT SYSTEM. THE MODEL WAS DERIVED FROM ONE-DIMENSIONAL, FORWARD-FINITE-DIFFERENCE, HEAT-TRANSFER THEORY AND PROGRAMMED FOR COMPUTER SOLUTION. IT WAS DESIGNED TO INCLUDE INPUT PARAMETERS AND CAN BE EXPANDED TO INCLUDE NEWLY DEVELOPED PARAMETERS. IT IS USED TO EVALUATE THE TEMPERATURE REGIME OF VARIED PAVEMENT SYSTEMS IN DIFFERENT GEOGRAPHICAL LOCATIONS. METEOROLOGICAL PARAMETERS SUCH AS SHORT-WAVE RADIATION, LONG-WAVE RADIATION, CONVECTION, AND AIR TEMPERATURE ARE THE BASIC EXTRINSIC FACTORS IN THE HEAT-TRANSFER MODEL. INTRINSIC FACTORS CONSIDERED ARE THE PHYSICAL PROPERTIES AND THERMAL PROPERTIES OF THE PAVEMENT MATERIALS THAT INCLUDE UNIT WEIGHT, MOISTURE CONTENT, MATERIAL CLASSIFICATION, THERMAL CONDUCTIVITY, HEAT CAPACITY, AND LATENT HEAT. THE MODEL WAS DEVELOPED SO THAT APPROPRIATE THERMAL PROPERTIES OF THE PAVEMENT MATERIALS ARE USED DEPENDING ON WHETHER THE UNFROZEN, FREEZING, OR FROZEN STATE EXISTS. PAVEMENT TEMPERATURES GENERATED BY THE MODEL WERE COMPARED WITH LABORATORY TEMPERATURE DATA AND TEMPERATURE DATA FROM THE AASHO ROAD TEST, AND THE MODEL GAVE VALID RESULTS. USE OF THE MODEL FOR EVALUATING FROST ACTION IN A PAVEMENT SYSTEM AT A SPECIFIED LOCATION WAS DEMONSTRATED FOR 30 YEARS OF PAST CLIMATIC RECORD. IT WAS SHOWN THAT NECESSARY QUANTITATIVE DATA FOR THE EVALUATING COULD BE OBTAINED. A CLEARER UNDERSTANDING OF THE QUALITATIVE FACTORS INVOLVED IN FROST ACTION RESEARCH WAS ALSO PROVIDED. /AUTHOR/
70 citations
TL;DR: In this article, 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, consistent with the suggestion by Ingersoll and Cuzzi that Zones are warmer than Belts and that the zonal flow is geostrophic.
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 ...
59 citations
TL;DR: In this article, the phase exchange process in a condensing medium is investigated using a continuum-like formulation, where the liquid phase is assumed sufficiently disperse so that the field may be treated as a continuum.
Abstract: The process of acoustic attenuation in a condensing medium is investigated using a continuumlike formulation that allows for the phase‐exchange process. The liquid phase is assumed sufficiently disperse so that the field may be treated as a continuum. The elementary relaxation processes associated with droplet velocity, temperature, and vapor pressure equilibration are equally important in determining the attenuation when vapor, liquid, and inert gas mass fractions are of the same order. When the liquid mass fraction is small, however, a strong attenuation band appears at low frequencies. This attenuation process involves a coupled relaxation process in which heat transfer and vaporization processes combine to change the temperature of the relatively large gas mass. This attenuation band (i) centers on a frequency that is proportional to the concentration of liquid, and (ii) has a maximum value that varies directly as the concentration of condensible vapor and roughly as the square of the latent heat of vaporization. When the concentrations of liquid and condensible vapor are both small, the low‐frequency attenuation band is nearly isolated and may be described in a convenient analytical manner.
57 citations
TL;DR: In this paper, a wide class of one-dimensional heat conduction problems with phase change is considered on the assumption that the latent heat is a given function of the position of the separation plane between the two phases: L=φ[s(t)].
Abstract: A wide class of one-dimensional heat conduction problems with phase change is considered on the assumption that the latent heat is a given function of the position of the separation plane between the two phases: L=φ[s(t)]. Some sufficient conditions for the existence and uniqueness of the solution in a given time-interval are given. This work permits the generalization of some previous results and the investigation of some cases of particular interest.
25 citations
TL;DR: In this paper, an improved method was presented to measure the latent heat of vaporization of volatile liquids at atmospheric pressure on a differential scanning calorimeter, and individual measurement errors of 8-10mg samples were reduced to less than 2% and the average error of five runs on benzene and toluene was less than.01%.
19 citations
TL;DR: In this paper, a mathematical model is given for an artificially produced vapor bubble growing on a surface and into a turbulent subcooled stream flowing parallel to the surface, which is tested for steam injection through a 0·0135 in. hole in a stainless steel plate and into water stream with Reynolds numbers from about 0·9 × 10 4 to 2·0 × 10 5, inlet bulk temperatures from 80 to 140°F, and near atmospheric pressure.
12 citations
TL;DR: In this paper, the melting of materials during heating is modelled automatically on a resistance-capacitance network analogue using field effect transistor switches, and the results are shown to be independent of the conditions on the edge of the slab provided that the edge is a distance of at least 1?5 times the slab depth from the heat source.
Abstract: The melting of materials during heating is modelled automatically on a resistance-capacitance network analogue using field effect transistor switches. Full details are given of the experimental techniques. Results are presented for the particular example of a flat slab heated by a concentrated heat source with melting occurring in the vicinity of the heat source. Non-dimensional curves are included from which the rise of temperature with time at a number of points can be determined. The latent heat of the material is also modelled on the network and for the problem of the concentrated heat source it is found to have no significant effect on the results. The results are shown to be independent of the conditions on the edge of the slab provided that the edge is a distance of at least 1?5 times the slab depth from the heat source.
6 citations
TL;DR: In this paper, the authors compared experimental calorimetric results with predicted refrigeration requirements by adding the contributions of sensible heat of mix above the initial freezing point and latent heat.
6 citations
TL;DR: In this article, the authors examined the time variation of various fluxes, namely net radiation, soil heat, sensible heat and latent heat observed at a tropical station, in relation to various meteorological parameters and atmospheric conditions.
Abstract: Studies of various fluxes, namely net radiation, soil heat, sensible heat and latent heat observed at a tropical station are presented in this paper. The time variation of these fluxes are examined in relation to various meteorological parameters and atmospheric conditions. The turbulent transfer coefficients have been evaluated to examine the applicability of the classical theory or the non-equivalence theory for eddy transport in the lower layers of the atmosphere. The energy balance at a tropical station is evaluated. It is found over year there is a net surplus of 94,000 ly. A detailed discussion of the disposal of this energy by various consuming processes is given.
Journal Article•
TL;DR: In this article, the results of the measurement of turbulent fluxes on Lake Kasumigaura as part of a project for the study of evaporation from reservoirs are presented.
Abstract: The results of the measurement of turbulent fluxes on Lake Kasumigaura as part of a project for the study of evaporation from reservoirs are presented in this paper. The sensor used in this study is the combination of the sonic anemo meter and the fine psychrometer. The data are analysed by the analog data analyser. The turbulent fluxes of momentum, sensible and latent heat are obtained as well as the mean values, and standard deviations of meteorological parameters are also obtained. The mean ratio of the standard deviation of vertical velocity to the friction velocity is 1.1 and the mean drag coefficient is about 4xlo3 • The total evaporation from the lake on a fine day in December is about 0.6 mm. Fairly large downward water vapor flux is seen in the daytime and upward flux in the night time. The mean vertical motion is observed, and this might be caused by the bank, 4 meters high, behind. The difference between vertical turbulent flux and the cross stream line turbulent flux is discussed.
TL;DR: In this article, the cooling effect of basaltic intrusions in the western part of Germany has been investigated using high-speed computers, where the latent heat being released during the solidification of the magma can be determined by means of numerical methods.
01 Apr 1970
TL;DR: In this paper, a seven layer physical-numerical model for the lower tropospheric region is described, which provides greater horizontal and vertical resolution in both the numerical analyses and numerical forecasts.
Abstract: : A limited area seven layer physical-numerical model for the lower tropospheric region is described. The grid interval is half that of the standard numerical weather prediction grid used in the hemispheric, free atmospheric operational model at the Air Force Global Weather Central (AFGWC). This model is an integral part of the complete AFGWC meso-scale (sub-synoptic) numerical analysis and prediction system. This model provides greater horizontal and vertical resolution in both the numerical analyses and numerical forecasts. It is used to predict the more detailed smaller scale atmospheric perturbations which are important in specifying sensible weather elements. Important features of this boundary layer model include: a completely automated objective numerical analysis of input data; the transport of heat and moisture by three dimensional wind flow (including terrain and frictionally induced vertical motions); latent heat exchange in water substance phase changes; and eddy flux of heat and water vapor.
TL;DR: In this paper, the authors used the heat balance method to estimate the transfer coefficient, foliage exchange velocity and stomatal exchange velocity within a corn canopy, and found that the extinction coefficient at the midpoint in the interval is in fairly good agreement with the mean transfer coefficient.
Abstract: Turbulent transfer coefficient, foliage exchange velocity and stomatal exchange velocity within a corn canopy are approached using the heat balance method. Measurements of air temperature, water vapour pressure, net radiation and wind speed were made at several levels within and above the canopy during the growing season of corn crops. Instruments presented schematically in Fig. 1 were used for the measurments.The results obatined can be summarized as follows:1: The exchange velocity in the interval h is given byD0-h=R(z1)/cpρ(ΔT+l/cpΔq)-A, where R(z1)=S(z1)-Bs; ΔT=T1-T2; Δq=q1-q2; S(z1), T1. q1, net radiation, air temperature and specific humidity at height z1; T2, q2 air temperature and specific humidity at height z2; Bs soil heat flux; Cp, ρ, specific heat and density of air; l, latent heat for evaporation. A is a term for considering the influence of changes of S and K in the interval on the exchange velocity. Mean transfer coefficient in the interval is given byK=h·D0-h.Preliminary computations indicate that the influence of the term A can be disregarded with acceptable errors in the canopy, provided the interval h is so small as 10cm (see Table 1). Fig. 2 shows that the transfer coefficient at the mid-point in the interval is in fairly good agreement with the mean transfer coefficient in the interval. Although the initial decrease of the transfer coefficient with the canopy depth is rapid, the decreasing rate diminishes gradually with the canopy depth. Values of the transfer coefficient at the canopy top are by one and two orders of magnitude larger than those in the lowest layer. The normalized profiles of the transfer coefficinet (K/KH) are shown in Fig. 4. Each point is the avergae of the respective normalized values for the 10-min profiles. The mean profiles were approximated by an exponential function. The values of its extinction coefficinet vary from 2.46 to 2.88, and agree well with those presented in literatures. The extinction coefficient seems to increase slightly with the maximum leaf area density within the canopy, but it requires futher experimental studies.2: The mean foliage exchange veloeity (Df) in the interval of 25cm was calculated byDf=ΔS-ΔlE/2cpρΔF(Tf-Ta), where ΔS, ΔlE, the divergence of net radiation and latent heat fluxes in the interval (ly/sec); ΔF, the partial leaf area index; (Tf-Ta), leaf-air temperature difference. The magnitudes of the foliage exchange velocity averaged for the daylight hours (0900-1700) are 3.8, 2.6, 1.9, 1.7, 1.0, 0.9cm/sec respectively in the layers of 275-250, 250-225, 225-200, 200-175, 175-150, 150-125cm. The absolute values of the foliage exchange velocity within the canopy are in fairly good agreement with results obtained by IMPENS et al. (1967) using a different method. The profiles of the foliage exchange velocity were also approximated by an exponential function. The value of extinction coefficient was found to be 2.8.Fig. 6 shows the foliage exchange velocity as a function of transfer coefficient. The following relation was obtained by regression analysisDf=0.56+1.25·10-3K.
TL;DR: In this paper, the problem of heat and solvent transfer from plasticized film is considered, and the transport equations are solved by a numerical method, including the temperature dependence of diffusivity, the dependence of diffusion on decreasing solvent concentration and the latent heat of vaporization of the solvent.
Abstract: The problem of heat and solvent transfer from plasticized film is considered. The transport equations are solved by a numerical method. The formulation of the model includes the temperature dependence of diffusivity, the dependence of diffusivity on decreasing solvent concentration, as solvent leaves the film, and the latent heat of vaporization of the solvent. The Flory-Huggins theory is used as a model for vaporliquid equilibrium. Heat and mass transfer coefficients are taken either as constants (to simulate extrusion with blowing at the film surface) or from analytical solutions to the appropriate boundary layer equations (to simulate extrusion into a stationary medium.) The boundary layer theory takes into account the effect of rapid vaporization on heat and mass transfer coefficients. Several numerical solutions were obtained for cases corresponding to extrusion of polyvinylacetate, plasticized with acetone, extruded into air.
01 Jan 1970
TL;DR: In this paper, the components of the radiation balance and the heat balance are computed for Lat. 45°, 60° and 75°N for various geological periods, and the resulting mean data on radiation and heat-balance components are then used to reconstruct the probable range of climatic situations that may have existed in what are now the polar, middle and subtropical latitudes of the territory of the USSR.
Abstract: The components of the radiation balance and the heat balance are computed for Lat. 45°, 60° and 75°N for various geological periods. Cloud cover is estimated for each geological period on the basis of continentality, the character of the underlying surface, type of climate and landscape as well as the known mean magnitude during the present geological period. Albedo is based on the character of the underlying surface indicated by paleogeographic data. Effective outgoing radiation is also based on the character of the underlying surface as well as cloud cover and atmospheric moisture. The disposition of net radiation at the earth's surface is broken down into sensible and latent heat fluxes, the soil heat flux being ignored. The resulting mean data on radiation and heat-balance components are then used to reconstruct the probable range of climatic situations that may have existed in what are now the polar, middle, and subtropical latitudes of the territory of the USSR.
TL;DR: In this article, it was shown that the main quantity of heat is transferred from the surface into the vapor volumes due to the latent heat of vaporization, which is the main source of heat for boiling.
Abstract: It is shown that in the development of boiling the main quantity of heat is transferred from the surface into the vapor volumes due to the latent heat of vaporization.
TL;DR: It was concluded that because of the difficulty in estimating thermal radiant heat fluxes in nature, an accurate prediction of insect temperature from energy balance calculations would be impossible.
Abstract: Respiration and transpiration by lots of 100 Anthonomus grandis Boheman (Coleoptera: Curculionidae), were measured in an open system under artificial lights at 3 levels (1195, 0530, and 0 calories per centimeter squared per minute) and at a wind speed of 134 centimeters per second Using these data a table was constructed showing the relative magnitudes of the various elements of the energy budget for the insects It was necessary to evaluate the reflectance and the thermal emissivity of the weevil; they were found to be 105% and 097, respectively It was found that the sun is by far the insect's greatest energy source in nature Most variation in short-wave radiation input is offset by changes in rate of convected heat loss Latent heat losses amounted to 10% of the convected heat loss under bright light and up to 25% at light levels simulating cloud cover It was concluded that because of the difficulty in estimating thermal radiant heat fluxes in nature, an accurate prediction of insect temperature from energy balance calculations would be impossible
01 Jan 1970
TL;DR: In this article, three ways of cooling a gas: (1) by exploiting the latent heat of evaporation of another gas of lower boiling point; (2) by causing it to do external work; and (3) by making use of the negative Joule-Thomson effect, arising from repulsive intermolecular forces which result in the performance of what is called internal work on expansion.
Abstract: There are three ways of cooling a gas: (1) by exploiting the latent heat of evaporation of another gas of lower boiling point; (2) by causing it to do external work; and (3) by making use of the negative Joule — Thomson effect, arising from repulsive intermolecular forces which result in the performance of what is called internal work on expansion.
TL;DR: In this article, the transfer effect in porous media caused by condensation was treated theoretically and the theoretical equations based on the concept of overall specific heat were derived, where Cp = cps + cpr where Cps is the specific heat of the body, and cpr is the value of specific heat due to the latent heat contribution.