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Sulfuric acid is one of the most important products in inorganic synthesis. Half of the manufactured amount of sulfuric acid is used for the production of mineral fertilizers. In this paper, a technological scheme for the manufacture of sulfuric acid from liquid sulfur using double contacting with intermediate absorption is studied. The production method allows the increase of the degree of oxidation...
The author explains his views that we need to clarify better what we mean by the terms efficiency and loss, and utilize exergy-based-rather than energy-based-measures of these quantities in order to ensure that the measures are meaningful and useful.
Using energy and exergy analyses, a dynamic simulation is carried out with a CaO/Ca(OH) 2 chemical heat pump system for heating and cooling applications. The system consists of hydration/dehydration reactor connected to condenser/evaporator with a control valve in between. During the dehydration process, heat is supplied at 700<space>K for dehydration of Ca(OH) 2 and steam is...
A typical ideal distillation process is proposed and analyzed using the first and second-laws of thermodynamics with particular attention to the minimum work requirement for individual processes. The distillation process consists of an evaporator, a condenser, a heat exchanger, and a number of heaters and coolers. Several Carnot engines are also employed to perform heat interactions of the distillation...
The maximum and minimum temperatures available limit the usable fraction (or Carnot efficiency) of a power cycle. The construction of LNG terminals and the need to vaporize LNG offers a thermal sink at a very much lower temperature than seawater. By using this thermal sink in a combined plant, it is possible to recover power from the vaporization of LNG.To this purpose, in this paper combined systems...
Exergy analysis is a highly effective method of analysis for thermal processes because it provides insight that cannot be obtained from energy analysis alone. In general the field of exergy analysis is both well formulated and well understood. However, the exergy flux, or the maximum work obtainable, from thermal radiation (TR) heat transfer has not been clearly formulated. Several researchers claim...
Energy and exergy analyses are conducted of the fluidized bed drying of moist materials for optimizing the operating conditions and the quality of the products. In this regard, energy and exergy models are developed to evaluate energy and exergy efficiencies, and are then verified with experimental data (for the product, wheat) taken from the literature. The effects of inlet air temperature, fluidization...
Mixing, in general, is an irreversible process, and some entropy is generated and thus some exergy is destroyed during such a process. Therefore, combining two systems thermodynamically that are at different states may yield a system that is larger in size, but much smaller in exergy content or ''usefulness''. In this paper we consider some mixing processes, and show that getting bigger is not necessarily...
The present study describes details of exergy-based performance characteristics of a heavy-duty gas turbine, 150MW-class GE 7F model. Results have shown that a chemical reaction in the combustor of which the exergy destruction ratio is 28.3% at full-load is one of the major sources of exergy destructions in the gas turbine. It was found that, in spite of its usefulness to the performance enhancement...
The author explains his view that we need to clarify our use and understanding of the term energy conservation, in particular by referring to exergy conservation when that is what we mean, so that we can more effectively address energy-related problems and issues.
In general the field of exergy analysis is both well formulated and well understood. However, the exergy flux, or maximum work obtainable, from thermal radiation (TR) heat transfer has not been clearly formulated. In a previous article it was shown that Petela's result, from his thermodynamic approach, does in fact represent the exergy flux of blackbody radiation (BR) and the upper limit to the conversion...
The reasons of the considerable decrease of COP of a real heat pump in comparison with the Carnot heat pump have been expressed by means of the component thermodynamic efficiencies which determine the influence of the particular irreversible processes on the coefficient of performance of the considered heat pump. The COP of the total installation is expressed as a product of component efficiencies...
A chemical potential transformer operating among three reservoirs at different chemical potentials is analogous to a heat transformer operating among three heat reservoirs. When the influence of finite-rate mass transfer between the working fluid and the reservoirs is taken into account, a chemical potential transformer may be conceived as a combined system having a chemical pump driven by a chemical...
An innovative method for the exergy efficiency calculation of a complex energy-intensive system with arbitrary structures is described in this paper. The method is based on a novel general equation to calculate the total system exergy efficiency, and on an exergy flow graph proposed by the authors. This approach allows a user to obtain not only the exergy efficiency of the total system, but also to...
In this study, an exergoeconomic analysis of condenser type parallel flow heat exchangers is presented. Exergy losses of the heat exchanger and investment and operation expenses related to this are determined with functions of steam mass flow rate and water exit temperature at constant values of thermal power of the heat exchanger at 75240 W, cold water mass flow rate and temperature. The inlet temperature...
A finite time analysis of an ideal refrigeration cycle with the objective of maximising refrigeration effect has been performed. The optimised refrigeration cycle has then been combined with an optimised power cycle to produce a combined cycle. The general matching requirements of the two cycles are discussed. The cycles are then combined in a specific way such that they become a model for an ideal...
On the basis of endoreversible absorption refrigeration cycle model with the sole irreversibility of heat transfer between the working fluid and the heat reservoirs, an irreversible model of absorption refrigeration cycle with heat transfer law of q Δ(T -1 ), which includes the heat leak from the heat sink to the cooled space and irreversibilities due to the internal dissipation of the...
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