Latent Heat

The main purpose of this chapter is to briefly recapitulate what is learned in a first course in classical thermodynamics (Only those portions of a typical undergraduate curriculum that are relevant to combustion calculations are given emphasis). As defined in Chap. 1, thermodynamics is the science of relationships among heat, work, and the properties of the system. Our first task, therefore, will be to define the keywords in this definition: system, heat, work, and properties. The relationships among these quantities are embodied in the First and the Second laws of thermodynamics. The laws enable one to evaluate the change in the states of the system, as identified by the changes in its properties. In thermodynamics, this change is called a process, although, in common everyday language, the processes maybe identified with terms such as cooling, heating, expansion, compression, phase change (melting, solidification, evaporation, condensation), or chemical reaction (such as combustion, catalysis, etc.). As such, it is important to define two additional terms: state and process.

The power of the handheld electronics devices continues to increase because packaging advances reduce their size even as more features are added and enhanced. The computational fluid dynamics (CFD) numerical simulation is performed on thermal management of the mobile phone using a heat storage unit (HSU) filled with the phase change material (PCM). The chips and HSU are embedded in

Baghdad is a large city, warmer than surrounding areas due to the urban heat island effect. The study is to determine the energy balance influenced the heat and mass transfer in soil water within the soiltrees canopy system. Bowen ratio techniques were used to obtain the field energy balance, including total latent heat flux. Soil latent heat flux was calculated from the differences between LE and LEc. These measurements were coupled with radiation measurements at the soil surface to partition the energy balance into soil and canopy components every hour throughout the daytime. Daily energy balance was strongly influenced by sensible heat flux transfer, and the radiation balance alone did not account for the magnitude or diurnal pattern of LEs and LEc. When the soil surface was wet after rainfall, LEs accounted for more than 87 % of LE even when LAI greater than 2.0 m/m.

Latent heat thermal energy storage with phase change materials (PCMs) is attractive since providing a high energy density storage due to the phase change by solidification/melting at constant temperature. Relative to sensible heat energy storage systems, latent heat storage with PCMs requires a smaller weight and volume of material for a given amount of captured/stored energy, and has the capacity to store heat of fusion at a constant or nearly constant temperature, thus maintaining a high and constant temperature difference between the heat exchanging surface and the PCMs. The present review paper will summarize the required properties of PCMs, with their respective advantages and disadvantages; the current state of development and manufacturing; the development of PCM applications, including their incorporation into heat exchangers, insertion of a metal matrix into the PCM, the use of PCM dispersed with high conductivity particles. PCM uses will be illustrated through some case-studies.

This is the third of a three-part investigation into tropical cyclone (TC) genesis in the Australian Bureau of Meteorology’s Tropical Cyclone Limited Area Prediction System (TC-LAPS), an operational numerical weather prediction (NWP) forecast model. In Parts I and II, a primary and two secondary vortex enhancement mechanisms were illustrated, and shown to be responsible for TC genesis in a simulation of TC Chris. In this paper, five more TC-LAPS simulations are investigated: three developing and two nondeveloping. In each developing simulation the pathway to genesis was essentially the same as that reported in Part II. Potential vorticity (PV) cores developed through low- to middle-tropospheric vortex enhancement in model-resolved updraft cores (primary mechanism) and interacted to form larger cores through diabatic upscale vortex cascade (secondary mechanism). On the system scale, vortex intensification resulted from the large-scale mass redistribution forced by the upward mass flu...

The water and heat balances of an arable field and a forest in the boreal zone in Scandinavia were explored using 3 yr of observations and simulations with two different soil–vegetation–atmosphere transfer (SVAT) models over a 30-yr period. Results from a detailed mechanistic model [coupled heat and mass transfer model (COUP)] were compared with those obtained with a large-scale type of SVAT model used in the weather prediction model at the European Centre for Medium-Range Weather Forecasts [ECMWF tiled land surface scheme (TESSEL)]. The COUP model simulations agreed well with the observations from a seasonal perspective. The TESSEL model differed significantly from the measurements when standard operational parameter values were used. The introduction of a seasonal variation in leaf-area index values, tuned canopy resistance for forest, and a reduced roughness length over snow-covered open land reduced the discrepancies. Net radiation was 40% higher in the forest when compared with...

The Common Land Model (CLM), which results from a 3-yr joint effort among seven land modeling groups, has been coupled with the National Center for Atmospheric Research (NCAR) Community Climate Model (CCM3). Two 15-yr simulations of CCM3 coupled with CLM and the NCAR ...

Buildings with indoor swimming pools are recognised as very high-energy consumers and present a grate potential for saving energy. The management of indoor ambient conditions must act upon the most sensible parameters that affect the energy consumption; the energy is spending in several ways: Evaporation heat loss from the pool; ambient temperatures very high; and High rates of ventilation required. Control Strategies adapted to the reality of each building is an important way to reduce energy consumption. These paper presents control strategies that can implemented in the building automation system and the HVAC system of an existing indoor swimming pool complex, in order to minimise energy consumption. Taking into account the complexity of the parameters involved in a feasibility study of measures to reduce the energy consumption of the building, the choice of energy simulation programs is actually the better way, either from both economical and time perspectives, to quantify the b...

Removal of dissolved salts and toxic chemicals in water, especially at a few parts per million (ppm) levels is one of the most difficult problems. There are several methods used for water purification. The choice of the method depends mainly on the level of feed water salinity, ...

Ultrasonic velocities have been measured in Phosphoryl Chloride by Kaulgud et al. using a special technique as it is corrosive. Using these results we have studied the temperature dependence of Rao's constant, Wada's constant, acoustic impedance, pseudo-Gruneise4n parameter, effective Debye temperature, free length and Lagemann's relation. We have also studied the relation between ultrasonic velocity and latent heat of vaporization, suggested by B. Ramachandra Rao. The results indicate a strong molecular association in Phosphoryl chloride due to dipole-dipole interactions. The excess energy of association, over and above the Van der Waal's contribution, has a value comparable to the binding energy of potassium metal.

The heat transfer enhancement in the latent heat thermal energy storage system by using an internally finned tube is presented in this paper. The phase change material fills the annular shell space around the tube, while the transfer fluid flows within the internally finned tube. The melting of the phase change material is described by a temperature transforming model coupled to the heat transfer from the transfer fluid. The heat conduction in the internal fins is an unsteady two-dimensional heat conduction problem and is solved by a finite difference ...

A model of the atmospheric boundary layer (BL) is presented that explicitly calculates a two-way interaction of the background flow and convective motions. The model is utilized for investigation of the formation of large eddies (roll vortices) and their effects on the structure of the marine boundary layer under conditions resembling those of tropical cyclones. It is shown that two main factors controlling the formation of large eddies are the magnitude of the background wind speed and air humidity, determining the cloud formation and latent heat release. When the wind speed is high enough, a strong vertical wind shear develops in the lower part of the BL, which triggers turbulent mixing and the formation of a mixed layer. As a result, the vertical profiles of velocity, potential temperature, and mixing ratio in the background flow are modified to allow for the development of large eddies via dynamic instability. Latent heat release in clouds was found to be the major energy source...

The heat transfer enhancement in the latent heat thermal energy storage system by using an internally finned tube is presented in this paper. The phase change material fills the annular shell space around the tube, while the transfer fluid flows within the internally finned tube. The melting of the phase change material is described by a temperature transforming model coupled to the heat transfer from the transfer fluid. The heat conduction in the internal fins is an unsteady two-dimensional heat conduction problem and is solved by a finite difference ...