The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform
Pilar Gayán - One of the best experts on this subject based on the ideXlab platform.
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Effect of formulation of steady-state Heat Balance for char particles on AFBC modelling
Fuel, 1993Co-Authors: Juan Adánez, Juan Carlos Abanades, Pilar GayánAbstract:Abstract For the solution of population Balances of char particles burning in the bed in modelling of an atmospheric fluidized-bed combustor (AFBC), a submodel for calculating the surface temperature of reacting char particles is included by solving the corresponding Heat Balance. This particle Heat Balance is strongly interrelated with other submodels through the kinetic term of Heat generation at the reaction surface. Three possible formulations for calculating the particle temperature are analysed: 1. (a) without particle Heat Balance; 2. (b) Heat Balance around the particle with a log mean of oxygen concentration; 3. (c) Heat Balance around the particle at each height in the bed. These assumptions are introduced into a model for an AFBC without a plume of volatiles, with slow bubble regime in the bed and with plug flow of gas, using the shrinking unreacted-core model and considering char losses by carryover and overflow. The effect of incorporating these hypotheses in the model is analysed through the solution of the population Balance. The results obtained indicate that the effect is appreciable on the carbon combustion efficiency and carbon loading in the bed.
Michael H. Unsworth - One of the best experts on this subject based on the ideXlab platform.
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Steady-State Heat Balance: (ii) Animals
Principles of Environmental Physics, 2013Co-Authors: John L. Monteith, Michael H. UnsworthAbstract:The Heat Balance of a leaf is determined mainly by its environment but the Heat Balance of warm-blooded animals (homeotherms) may also be modified by the animal’s ability to adjust its rate of internal metabolic Heat production and its rate of Heat dissipation by sweating. Cold-blooded animals (poikilotherms) have less physiological control of their Heat Balance but can seek shade, sun, or shelter from the wind to alter energy gains and losses. In this chapter each term of the animal Heat Balance equation is reviewed. The basal metabolic rate of homeotherms can be related to body mass or surface area by an empirical power law. Maximum metabolic rates are about one order of magnitude larger. Latent Heat is lost during breathing and by sweating. Desert animals conserve water by several mechanisms. The resistance to convective Heat loss is proportional to the square root of size and to the inverse square root of windspeed, so that temperatures of small animals are closely coupled to air temperature. Heat loss by conduction to the ground is reviewed. Some homeotherms (e.g. camels) and all poikilotherms store Heat by allowing their body temperature to increase, but most homeotherms keep their body temperature almost constant. The thermo-neutral diagram, representing the fundamental relation between metabolic Heat production and environmental temperature, is discussed in detail. A diagrammatic method of analyzing animal Heat Balance terms is described and applied to several examples. Finally the Heat Balance of man, including activities involving sweating, is analyzed.
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Steady-State Heat Balance: (i) Water Surfaces, Soil, and Vegetation
Principles of Environmental Physics, 2013Co-Authors: John L. Monteith, Michael H. UnsworthAbstract:Building on the principles of radiation, momentum, Heat, and mass transfer in previous chapters, we now address the steady-state Heat Balance of water bodies, soil, and vegetation by applying the First Law of Thermodynamics. We begin with the Heat Balance of dry-bulb and wet-bulb thermometers to establish basic principles and introduce the concept of resistances to Heat and mass transfer. The Heat Balance of wet surfaces introduces adiabatic and diabatic processes. This leads to the Penman Equation, discussion of its application to estimating evaporation from natural surfaces, and analysis of the dependence of evaporation rate on the weather. Considering the Heat Balance of leaves, the Penman-Monteith (PM) Equation is developed, identifying the distinction between boundary layer resistances to Heat and mass transfer and the stomatal resistance. Differences between factors influencing evaporation from wet surfaces and those influencing transpiration from leaves are discussed. The PM Equation is used to explore how transpiration and leaf temperature depend on radiation, humidity, windspeed, and stomatal resistance; rates of dew deposition are also discussed. Developments from the Penman and PM Equations conclude the chapter, including discussion of the “big-leaf model” for vegetation canopies, the equilibrium evaporation rate, and Priestley-Taylor coefficient, and the concept of “coupling” between vegetation and the atmosphere.
Juan Adánez - One of the best experts on this subject based on the ideXlab platform.
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Effect of formulation of steady-state Heat Balance for char particles on AFBC modelling
Fuel, 1993Co-Authors: Juan Adánez, Juan Carlos Abanades, Pilar GayánAbstract:Abstract For the solution of population Balances of char particles burning in the bed in modelling of an atmospheric fluidized-bed combustor (AFBC), a submodel for calculating the surface temperature of reacting char particles is included by solving the corresponding Heat Balance. This particle Heat Balance is strongly interrelated with other submodels through the kinetic term of Heat generation at the reaction surface. Three possible formulations for calculating the particle temperature are analysed: 1. (a) without particle Heat Balance; 2. (b) Heat Balance around the particle with a log mean of oxygen concentration; 3. (c) Heat Balance around the particle at each height in the bed. These assumptions are introduced into a model for an AFBC without a plume of volatiles, with slow bubble regime in the bed and with plug flow of gas, using the shrinking unreacted-core model and considering char losses by carryover and overflow. The effect of incorporating these hypotheses in the model is analysed through the solution of the population Balance. The results obtained indicate that the effect is appreciable on the carbon combustion efficiency and carbon loading in the bed.
John L. Monteith - One of the best experts on this subject based on the ideXlab platform.
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Steady-State Heat Balance: (ii) Animals
Principles of Environmental Physics, 2013Co-Authors: John L. Monteith, Michael H. UnsworthAbstract:The Heat Balance of a leaf is determined mainly by its environment but the Heat Balance of warm-blooded animals (homeotherms) may also be modified by the animal’s ability to adjust its rate of internal metabolic Heat production and its rate of Heat dissipation by sweating. Cold-blooded animals (poikilotherms) have less physiological control of their Heat Balance but can seek shade, sun, or shelter from the wind to alter energy gains and losses. In this chapter each term of the animal Heat Balance equation is reviewed. The basal metabolic rate of homeotherms can be related to body mass or surface area by an empirical power law. Maximum metabolic rates are about one order of magnitude larger. Latent Heat is lost during breathing and by sweating. Desert animals conserve water by several mechanisms. The resistance to convective Heat loss is proportional to the square root of size and to the inverse square root of windspeed, so that temperatures of small animals are closely coupled to air temperature. Heat loss by conduction to the ground is reviewed. Some homeotherms (e.g. camels) and all poikilotherms store Heat by allowing their body temperature to increase, but most homeotherms keep their body temperature almost constant. The thermo-neutral diagram, representing the fundamental relation between metabolic Heat production and environmental temperature, is discussed in detail. A diagrammatic method of analyzing animal Heat Balance terms is described and applied to several examples. Finally the Heat Balance of man, including activities involving sweating, is analyzed.
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Steady-State Heat Balance: (i) Water Surfaces, Soil, and Vegetation
Principles of Environmental Physics, 2013Co-Authors: John L. Monteith, Michael H. UnsworthAbstract:Building on the principles of radiation, momentum, Heat, and mass transfer in previous chapters, we now address the steady-state Heat Balance of water bodies, soil, and vegetation by applying the First Law of Thermodynamics. We begin with the Heat Balance of dry-bulb and wet-bulb thermometers to establish basic principles and introduce the concept of resistances to Heat and mass transfer. The Heat Balance of wet surfaces introduces adiabatic and diabatic processes. This leads to the Penman Equation, discussion of its application to estimating evaporation from natural surfaces, and analysis of the dependence of evaporation rate on the weather. Considering the Heat Balance of leaves, the Penman-Monteith (PM) Equation is developed, identifying the distinction between boundary layer resistances to Heat and mass transfer and the stomatal resistance. Differences between factors influencing evaporation from wet surfaces and those influencing transpiration from leaves are discussed. The PM Equation is used to explore how transpiration and leaf temperature depend on radiation, humidity, windspeed, and stomatal resistance; rates of dew deposition are also discussed. Developments from the Penman and PM Equations conclude the chapter, including discussion of the “big-leaf model” for vegetation canopies, the equilibrium evaporation rate, and Priestley-Taylor coefficient, and the concept of “coupling” between vegetation and the atmosphere.
Juan Carlos Abanades - One of the best experts on this subject based on the ideXlab platform.
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Effect of formulation of steady-state Heat Balance for char particles on AFBC modelling
Fuel, 1993Co-Authors: Juan Adánez, Juan Carlos Abanades, Pilar GayánAbstract:Abstract For the solution of population Balances of char particles burning in the bed in modelling of an atmospheric fluidized-bed combustor (AFBC), a submodel for calculating the surface temperature of reacting char particles is included by solving the corresponding Heat Balance. This particle Heat Balance is strongly interrelated with other submodels through the kinetic term of Heat generation at the reaction surface. Three possible formulations for calculating the particle temperature are analysed: 1. (a) without particle Heat Balance; 2. (b) Heat Balance around the particle with a log mean of oxygen concentration; 3. (c) Heat Balance around the particle at each height in the bed. These assumptions are introduced into a model for an AFBC without a plume of volatiles, with slow bubble regime in the bed and with plug flow of gas, using the shrinking unreacted-core model and considering char losses by carryover and overflow. The effect of incorporating these hypotheses in the model is analysed through the solution of the population Balance. The results obtained indicate that the effect is appreciable on the carbon combustion efficiency and carbon loading in the bed.
