Plenary Lecture

Analysis of Irreversible Thermodynamic Processes
of Control Valves

Professor Ioana Diaconescu
Research Center for Mechanics of Machines and Technological Equipment
“Dunarea de Jos” University from Galati
Calea Calarasilor 29, 810017, Braila
Romania
E-mail: idiaconescu@ugal.ro

Abstract: The thermodynamic analysis of irreversible processes has an important influence in energy efficiency growing of any thermodynamic processes or systems. All of thermodynamic processes are entropy generators but there are processes with such a high level of irreversibility so that couldn’t be ignored. That is why is so important to provide a feel for what causes entropy generation and to identify those system components that contribute the most to the overall irreversibility of the thermodynamic system. One of the processes with the highest level of entropy generation is flow with friction in various ducts and flow networks such as control valves. In order to see the direct connection between frictional pressure drop and thermodynamic irreversibility the paper will firstly analyze the steady and adiabatic flow of pure substance through a short segment of pipe with variable section (control valve).
Because the entropy generation value during the throttling process is proportional to control valve pressure drop, the paper will do a flow thermodynamic analysis inside the control valve and the conclusions about drop pressure in different working conditions will be taken. Pressure drops along a valve are not constant, but rather vary in relation to the port left open by the plug. They normally increase as the vena contracta section is reduced, although the upstream drop does increase at a slower rate than the downstream one. Actual increases and decreases in pressure drops and their effects are related to valve type and flow direction. It can be deduced that, for all types, pressure drops increase at flow tending to close, mainly as a result of the increased drop generated downstream.
Also the paper will take into account the drop pressure variation during the substance flow and will be analyzed its influence on the process irreversibility.
In the same time, the paper will analyze the change of state influence during the liquid throttling process on the entropy generation, in situations of low titer bipolar phase fluid or high titer bi phase fluid and will identify this phenomenon effects and remedies.

Brief Biography of the Speaker:
Ioana Diaconescu received her Master‘s degree in Electrotechnics and Energetic from Polytechnic Institute from Bucharest, in 1987. She has earned her Ph.D in Advanced Engineering Thermodynamics from “Dunarea de Jos” University-Galati, in 1998. She is recognized as mechanical engineering professor at the department of Technical Sciences, Machines and Drives from “Dunarea de Jos” University from Galati and she teaches mainly Thermodynamics, Heat and Mass Transfer and Electrical Drives. Since 2001 she is a senior research at the Research Center for Mechanics of Machines and Technological Equipments and she focused her research activities during the last eight years to energy saving and trigeneration, mass and heat transfer (paper drying process), exergy and energy analysis of thermal processes, irreversible processes analysis, renewable energy. She is author of three books and more than 70 scientific papers published at international conferences and journals. She is Romanian and Bulgarian evaluator for R&D projects.
Ioana Diaconescu was invited two times as visiting professor in City University of Honk-Kong-China, were developed a fruitful collaboration with Mathematical Department regarding PDEs in mass transfer issues (paper drying process).