Exergy analysis of an ammonia?water absorption system for cooling applications is presented in this paper. Exergy destruction rate and heat rate in each component of the system are evaluated. From the results obtained it can be concluded that the evaporator and condenser heat loads and exergy destruction rate are less than those of the absorber and generator. This is due to the heat of mixing in the solution. Furthermore, a simulation program is written and used for the determination of the total exergy destruction rate, the effectiveness and the coefficient of performance of the absorption system under different operating conditions.

Exergy analysis of an ammonia?water absorption system

L’epuisement des ressources fossiles et la necessite de reduire les emissions de gaz a effet de serre incitent a rechercher de nouvelles sources d’energie a la fois renouvelables et moins polluantes. La biomasse, par son abondance, apparait comme une filiere interessante de remplacement des energies fossiles et notamment du petrole. L’objectif de ce travail est d’effectuer une analyse 4E (Energetique, Exergetique, Environnementale et Economique) d’un systeme de production de l’electricite via la gazeification des dechets de palmiers. Ces derniers constituent l’une des richesses vegetales les plus abondantes en Tunisie et qui de nos jours, restent tres peu exploitees. Un gazeifieur a lit fixe couple a un moteur a combustion interne est considere pour produire 330kW d’electricite. Le rendement de gazeification « Cold Gaz Efficiency » du procede est de 58,58%. Les resultats montrent que les rendements energetique et exergetique du systeme etudie sont de 22,6% et 19,22%, respectivement. Les performances environnementales du systeme sont evaluees a l’aide d’une Analyse de Cycle de Vie (ACV). L’evaluation economique est realisee dans le but d’evaluer le cout de production de l’electricite par l’installation de gazeification. Les resultats donnent un cout de 3,88ct€ pour 1kWh.

https://tel.archives-ouvertes.fr/tel-01884559/document

Analyse 4E (Energétique, Exergétique, Environnementale et Economique) de systèmes de valorisation énergétique de biomasses

A fundamentally new concept of a heat engine on the basis of heterogeneous working body, consisting of liquid and lyophobic towards it capillary-porous matrix was proposed in the middle 1980's. The unusualness of the new thermodynamic cycle and engine is that the interface of condensed heterogeneous lyophobic systems (HWB), "liquid- rigid solid capillary-porous matrix", the carrier of free surface energy, serves as a working body (in a thermodynamic sense) instead of traditional gas/steam. In this paper the main advantages, challenges and prospects for use of HWB as the working fluid for external combustion engine are discussed.

http://dergipark.ulakbim.gov.tr/eoguijt/article/download/1034000509/1034000478

Current Status and Perspectives of Thermomolecular Engine Developments

A second law analysis of an ammonia -water double-effect double-generator absorption chiller is performed. The irreversibility in each component in the chiller is quantified and the contribution of each component to the overall system efficiency determined. Computer simulation was carried out in order to determine the stream properties and heat and work exchanged with the surroundings [1]. Simulation results where then used to analyse the entropy generation and irreversibility (or exergy destruction) of each component. The results indicate that in the absorber, the solution heat exchangers, and the condenser the greatest irreversibilities occur. In these equipements may lay the most improvement potential of the cycle efficiency.

/pdf/second-law-study-of-ammonia-water-double-effect-absorption-42ovz7i181.pdf

Second Law Study of Ammonia-Water Double Effect Absorption Chiller

This contribution focuses on some non-classical aspects of capillary phenomena, mostly omitted in classical approaches, in particular the non-isothermal aspects. A systematic thermodynamic approach is proposed that allows a rigorous formulation of the governing equations in non-isothermal situations, by introducing the surface effects in the energy and entropy balances. The energetic quantities (work and heat) are calculated in a number of examples, such as adiabatic and isothermal wetting/dewetting of a porous medium, nanofluids heating, emulsion split, and new equilibrium criteria are derived were appropriate.

Some New Results From Applying Thermodynamics to Wetting Phenomena

On montre que la performance energetique d'un systeme ouvert quelconque est independante de la temperature de reference choisie pour calculer le bilan d'exergie. On conseille donc de choisir celle qui facilite les calculs. Application a une pompe a chaleur a sorption.

Quelle température de référence choisir dans le calcul de l'exergie ?

Thermodynamics aspects of capillary flows

The paper aims to propose a general thermodynamic analysis concerning the systems in which capillarity plays an important role. Forced or spontaneous intrusion of a liquid in a microporous body is a form of the process consisting of wetting a solid having a large specific surface with a given liquid. The first and second law of thermodynamics are applied so that to take into account both surface and volume energies. The tool proposed permits to study the equilibrium in capillaries and to derive a general relation giving the intrusion pressure. The general equations are then applied to study isothermal and isentropic intrusion. Mots-Cles : Thermodynamique, capillarite, milieux poreux

http://documents.irevues.inist.fr/bitstream/handle/2042/16532/CFM2007-0401.pdf;sequence=1

Ahmed Laouir

Papers

Quelle température de référence choisir dans le calcul de l'exergie ?

Some New Results From Applying Thermodynamics to Wetting Phenomena

Thermodynamics aspects of capillary flows

Analyse thermodynamique de l'intrusion forcée et spontanée des liquides dans les corps microporeux