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RESEARCH PAPERS

J. Energy Resour. Technol. 1987;109(2):49-57. doi:10.1115/1.3231324.

Manure from cattle feedlots is a renewable energy source which has the potential of supplementing the existing fossil fuels. But the heat content of manure is rather low. Since, the fluidized bed combustion technology has been used for the energy conversion of marginal fuels, such a technology is being explored for the combustion of feedlot manure. A fluidized bed combustor of 0.15 m (6 in.) diameter was used for the combustion tests on manure. Experiments were conducted with −20 to +20 percent excess air and at bed temperatures ranging from 600°C (1112°F) to 800°C (1472°F). Experimental data revealed that the gasification efficiencies ranged from 90 to 98 percent, while the combustion efficiencies varied from 45 to 85 percent. Higher combustion efficiencies were obtained with decreased volatile solids content of manure. The low combustion efficiencies are attributed to the limited residence time available for the volatiles to burn within the reactor.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1987;109(2):58-65. doi:10.1115/1.3231325.

This paper presents operating experience with a fluidized bed combustor burning various coals. The primary focus is on the effect of relevant coal properties on combustor performance. Tests were carried out using anthracite, HVB and HVC bituminous and sub-bituminous A coals, and petroleum coke. Comparisons of the performance of the combustion on the various fuels are made. A two-stage fluidized bed combustor operating in a single-stage mode without recycle was employed. Experimental measurements included temperature, fuel feed rate, fluidization velocity and bed height. For some of the coals, bed agglomeration was found to occur. The results indicate that coal properties have an important effect upon the operation of the fluidized bed combustor.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1987;109(2):66-70. doi:10.1115/1.3231326.

The physical processes that occur typically within an oil sand bed are considered when the bed is subjected to a hot gaseous stream. In this study, the extent of fluid volatilization was obtained from a consideration of the simultaneous heat and mass transfer processes within the oil sands. The resulting system of equations together with the boundary conditions were solved numerically using an implicit finite difference method. The transient fluid concentration and temperature distributions within the oil sand bed were then obtained under a wide range of operating conditions. The resulting theoretical rates of volatilization and temperatures show generally good agreement with corresponding experimental values that were obtained for the purpose.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1987;109(2):71-74. doi:10.1115/1.3231327.

Based on a quasi-steady system, published experimental data on mass transfer in packed beds of spherical particles at relatively low Reynolds numbers, were employed to estimate the convective mass-transfer coefficients in the bed in terms of the corresponding values for single particles. The average transient fluid concentrations within the bed of particles were also obtained in terms of the corresponding single-particle concentrations using the lumped-heat-capacity system. Thus, experimental data published on volatilization of single oil sand spheres could then be extended to estimate the rates of volatilization of packed beds of oil sand spheres. A simple analytical expression could, therefore, be derived for estimating the transient mass loss from fixed beds of oil sand spheres in terms of the parameters involved.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1987;109(2):75-78. doi:10.1115/1.3231328.

Clusters of preshaped oil sand spherical fragments were subjected to hot steady streams of air at low Reynolds number and constant stream temperature. A wide range of different combinations and arrangements of these fragments were employed involving up to twenty identical spherical samples that were either piled or set normal to the free stream of air and left exposed for various prescribed time periods at constant stream temperatures. The rates of mass loss due to fluid volatilization off these clusters during this exposure were then established experimentally and compared with the corresponding rates derived from the behavior of single spheres. This comparison showed, for the cases considered in this investigation, essentially no significant effect due to the interaction of the spherical samples with each other. The behavior of a single fragment can then form the basis for establishing the volatilization rate of the cluster. However, it was shown that the confinement of these clusters of fragments within a cylindrical tube placed axially along the heating stream produced appreciable effects on the rates of volatilization. The extent of the deviation from the single fragment model observed was then examined and a number of variables affecting it identified.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1987;109(2):79-83. doi:10.1115/1.3231329.

A mathematical model is developed to simulate the thermal characteristics of energy recovery incinerators. This model takes descriptions of the fuel and of the incinerator as inputs then predicts system temperatures, steam generation rate, and energy recovery efficiency. There are options to include primary or secondary water-walls, a water/firetube boiler, or combinations of these heat exchangers. Both starved and excess air operation are considered.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1987;109(2):84-89. doi:10.1115/1.3231330.

The thermal characteristics of energy recovery incinerators are examined, both parametrically and, to the extent possible, by direct comparison. A mathematic model is employed, using a computer program to solve the governing equations. Three energy recovery configurations are considered: a water tube heat exchanger downstream from the combustion chambers, waterwalls, and a combination of the two. Results show the advantages of combining water walls and a convection boiler.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1987;109(2):90-95. doi:10.1115/1.3231331.

The essential design parameters for determining the optimum configuration of an air-cooled condenser are identified in this paper. For a power plant operating on a Rankine cycle, expressions for (i) the minimum frontal area, (ii) the minimum heat transfer area, and for (iii) the maximum net cycle efficiency, with respect to the condenser temperature and the cooling air velocity are derived. The analyses are carried out with the assumption that the exit temperature of the cooling air is equal to the condenser temperature. All resulting equations are presented in dimensionless form so that they are applicable to any power cycle with a gas-cooled condenser.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 1987;109(2):96-100. doi:10.1115/1.3231332.

Many industrial sectors reject heat to the atmosphere in the form of hot water with a temperature between 40° and 70°C. This low grade heat can be upgraded by using a vapor absorption heat transformer (AHT). The present study considers a single stage AHT with binary mixture of NH3 –H2 O as the working fluid. The performance characteristics of the system have been evaluated by solving the governing mass and energy balance equations using a digital computer. It is found that the permissible range of concentration across the absorber is 0.04<ΔX <0.075 for the following operating conditions:

Tuseful heat≤120°C,
43°≤Twaste heat≤88°C
and
10°≤Tsink≤27°C.

Commentary by Dr. Valentin Fuster

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