Dimitrios Kouremenos - Academia.edu (original) (raw)

Papers by Dimitrios Kouremenos

Research paper thumbnail of A High Temperature Heat Pump With Methanol/Water Absorption

Advanced Energy Systems

The high temperature lift heat pumps required in many technical applications can not be achieved ... more The high temperature lift heat pumps required in many technical applications can not be achieved by conventional single stage absorption units. In recent years as solution of this problem have been proposed the multistage absorption cycles with many heat exchange units, control devices and a higher capital expenditure. The purpose of this work is to investigate the posibility of a design of a methanol/water single stage AHP, capable to meet the high temperature lift heating requirements. The lacking thermodynamic properties of the working medium are estimated at modest and higher pressures. The results are given in correlations suitable for computer use as well as in diagrams. A parametric study is conducted for the proposed unit in order to reveal the influence of the varius parameters on the performance of the cycle.

Research paper thumbnail of Isentropic Expansion and the Three Isentropic Exponents of R152a

Advanced Energy Systems, 1999

The isentropic change of an ideal gas is described by the well known relations pvk = const., Tv(k... more The isentropic change of an ideal gas is described by the well known relations pvk = const., Tv(k-1) = const. and p(1-k)Tk = const., where the exponent k is defined as the ratio of the constant pressure to the constant volume specific heat, k = Cp/Cv. The same relations can be used for real gases only if the differential isentropic changes under consideration are small. A better examination of the differential isentropic change shows that for p, v, T systems, there are three different isentropic exponents corresponding to each pair formed out of the variables p, v, T. These three exponents noted kT,p, kT,v, kp,v after the corresponding pair of variables used, are interconnected by one relation, and accordingly only two out of the three are independent. The analysis of the present paper shows the numerical values of these exponents as well as the isentropic expansion ratios for R152a in the vapor phase, presented in diagram form. It can be seen that the deviations of the three isentr...

Research paper thumbnail of Thermodynamic Analysis of Direct Injection Diesel Engines by Multi-Zone Modelling

Research paper thumbnail of Isentrope Expansion des Wasserdampfes

Brennstoff Warme Kraft, 1985

Calcul, a l'aide d'un programme d'ordinateur, et representation sous forme de graphiq... more Calcul, a l'aide d'un programme d'ordinateur, et representation sous forme de graphiques en fonction du nombre de Mach, de l'expansion isentropique de la vapeur d'eau pour des temperatures initiales de 200, 400, 600 et 800°C et un volume initial de 0,5 m 3 /kg

Research paper thumbnail of The flow of individual cylindrical gas bubbles in vertical circular tubes

Ph D Thesis Scitran Inc Santa Barbara Ca Transl into English from Eidgenoess Tech Hochschule 1967 123 P, Nov 1, 1975

Research paper thumbnail of Using a Phenomenological Multi-Zone Model to Investigate the Effect of Injection Rate Shaping on Performance and Pollutants of a DI Heavy Duty Diesel Engine

SAE Technical Paper Series, 2002

... using sophisticated 3-D CFD codes due to extremely high computational time. ... modelling of ... more ... using sophisticated 3-D CFD codes due to extremely high computational time. ... modelling of mixture formation and combustion in a DI diesel engine”, SAE Paper ... Kouremenos, DA, Rakopoulos, CD and Hountalas, DT, “Thermodynamic analysis of indirect injection diesel engines ...

Research paper thumbnail of Prechamber and main chamber insulation effects on the performance of an IDI diesel engine coupled to power turbine

Heat Recovery Systems and CHP, 1992

ABSTRACT

Research paper thumbnail of Performance of a solar driven compound NH3/H2OH2O/LiBr absorption refrigeration system in athens

Solar & Wind Technology, 1990

A solar driven, high efficiency, compound refrigeration system is considered, made up of two coop... more A solar driven, high efficiency, compound refrigeration system is considered, made up of two cooperating absorption parts, which use NH3/H2O and H2O/LiBr solutions, respectively. Solar heat is given to the vapour generator of the NH3/H2O unit, and the heat produced by the absorber and the condenser of this unit is supplied to the vapour generator of the H2O/LiBr unit. A method for simulating the operation of the compound system has been developed and applied for predicting the hour by hour performance of the system operating during the typical year in Athens, for which solar radiation and ambient temperature data are available. An optimization study for the compound and the individual cycles has also been made. Very high performance of the system has been predicted. For example, on 21 May, the calculated theoretical coefficient of performance is 219% while the corresponding theoretical values of single H2O/LiBr and NH3/H2O units are 93% and 65% respectively. The corresponding calculated cooling power produced by the system is 543 W/m2-collector. An annual analysis shows that the cooling produced by a NH3/H2O unit in Athens is 0.87 GJ/m2-year, while the present compound system gives an impressive increase to 3 GJ/m2-year.

Research paper thumbnail of Ideal gas relations for the description of the real gas isentropic changes

Forschung im Ingenieurwesen, 1985

Research paper thumbnail of Die Anwendung der Redlich-Kwong-Zustandsgleichung zum Beschreiben des thermodynamischen Verhaltens der realen Gase

Forschung im Ingenieurwesen, 1991

Research paper thumbnail of The Effect of EGR on the Performance and Pollutant Emissions of Heavy Duty Diesel Engines Using Constant and Variable AFR

SAE Technical Paper Series, 2001

... The work is applied on a single cylinder truck test engine developed under a project funded b... more ... The work is applied on a single cylinder truck test engine developed under a project funded by the ... Desantes, JM, Arregle, J., Molina, SA and Lejeune, M., “Influence of the EGR Rate, Oxygen Concentration and ... ASME, J. Engng for Gas Turbines and Power, 112, 138-149, 1990. ...

Research paper thumbnail of Über die reduzierten Isentropenexponenten des Wasserdampfes

Forschung im Ingenieurwesen, 1989

ZusammenfassungEs wurde bereits bewiesen, daß es drei Isentropenexponenten gibt, nämlich kpv, kTp... more ZusammenfassungEs wurde bereits bewiesen, daß es drei Isentropenexponenten gibt, nämlich kpv, kTp und kTv. Wenn sie an Stelle des bekannten Exponenten k=cp/cv benutzt werden, könnte man mit Hilfe der einfachen Beziehungen des idealen Gases differentielle isentrope Zustandsänderungen eines realen Gases mit großer Genauigkeit beschreiben. Ferner ergibt sich für die Schallgeschwindigkeit α eines realen Gases die einfache Gleichung α=(kpvpv)1/2.Sowohl die drei Isentropenexponenten als auch die Schallgeschwindigkeit α eines realen Gases können nur dann berechnet werden, wenn ihre thermischen und kalorischen Zustandsgleichungen bekannt sind. Dies ist aber nur für wenige reale Gase der Fall. Zur Vermeidung dieses Hindernisses wurde versucht, Beziehungen zur Berechnung der Schallgeschwindigkeit und der Isentropenexponenten eines realen Gases mit Hilfe der allgemein gültigen Redlich-Kwong-Zustandsgleichung anzugeben. Die Ergebnisse werden in einer allgemeinen Form durch die reduzierte Temperatur, das reduzierte Volumen und den Kompressibilitätskoeffizienten—d.h. unabhängig von den Eigenschaften des realen Gases—erhalten und im Z,pr-Diagramm aufgetragen. Um die Genauigkeit des beschriebenen Verfahrens zu prüfen, wurden die reduzierten Werte der entsprechenden Größen für den Wasserdampf mit Hilfe seiner thermischen und kalorischen Zustandsgleichungen ermittelt und ebenfalls in den Diagrammen aufgetragen. Es wird eine starke Druckabhängigkeit der betreffenden Größen festgestellt. Ferner ergibt sich, daß die Redlich-Kwong-Zustandsgleichung nur für Überschlagsrechnungen herangezogen werden kann.

Research paper thumbnail of Second law analysis of non-equilibrium fluid streams

Forschung im Ingenieurwesen, 1989

Research paper thumbnail of Thermodynamic determination of the top dead centre of diesel engines

Forschung im Ingenieurwesen, 1987

Research paper thumbnail of The normal shock waves of real gases and the generalized isentropic exponents

Forschung im Ingenieurwesen, 1986

Research paper thumbnail of Experimental Investigation of the Effect of Fuel Composition on the Formation of Pollutants in Direct Injection Diesel Engines

SAE Technical Paper Series, 1999

Research paper thumbnail of Development of a Detailed Friction Model to Predict Mechanical Losses at Elevated Maximum Combustion Pressures

SAE Technical Paper Series, 2001

Abstract Engineers use phenomenological simulation models to determine engine performance. Using ... more Abstract Engineers use phenomenological simulation models to determine engine performance. Using these models, we can predict with reasonable accuracy the heat release rate mechanism inside the engine cylinder, which enables us to obtain a ...

Research paper thumbnail of Use of helium instead of hydrogen in inert gas absorption refrigeration

International Journal of Refrigeration, 1988

Abstract The behaviour of helium in place of hydrogen as a pressure equalizing gas in triple-flui... more Abstract The behaviour of helium in place of hydrogen as a pressure equalizing gas in triple-fluid absorption refrigeration units is examined. The main thermodynamic and transport properties of the real NH3/He binary gas mixture are presented in the form of diagrams and analytical expressions, with the temperature and the mass fraction of the mixture as input variables. Among others, the mass or mole fraction of the NH3/He gas mixture as a function of the dry and wet bulb temperatures has been plotted. A computer simulation has been developed to calculate the evaporation of NH3 in a NH3/He atmosphere within an insulated tube, allowing measurement of the composition of the mixture via temperature measurement. The results are compared with the corresponding values of evaporation of NH3 in a NH3/H2 atmosphere.

Research paper thumbnail of On the three exponents of the isentropic change of the refrigerant R22

International Journal of Heat and Fluid Flow, 1986

Research paper thumbnail of Sound velocity and isentropic exponents of real air on its compressibility chart

International Journal of Heat and Fluid Flow, 1991

... classical exponent k=cJc, in the ideal-gas isentropic-change equations, may be applied with g... more ... classical exponent k=cJc, in the ideal-gas isentropic-change equations, may be applied with great ... the developed relations may be employed not only in the field of thermodynamics but also ... between the air and other real gases for the purpose of drawing generalized conclusions ...

Research paper thumbnail of A High Temperature Heat Pump With Methanol/Water Absorption

Advanced Energy Systems

The high temperature lift heat pumps required in many technical applications can not be achieved ... more The high temperature lift heat pumps required in many technical applications can not be achieved by conventional single stage absorption units. In recent years as solution of this problem have been proposed the multistage absorption cycles with many heat exchange units, control devices and a higher capital expenditure. The purpose of this work is to investigate the posibility of a design of a methanol/water single stage AHP, capable to meet the high temperature lift heating requirements. The lacking thermodynamic properties of the working medium are estimated at modest and higher pressures. The results are given in correlations suitable for computer use as well as in diagrams. A parametric study is conducted for the proposed unit in order to reveal the influence of the varius parameters on the performance of the cycle.

Research paper thumbnail of Isentropic Expansion and the Three Isentropic Exponents of R152a

Advanced Energy Systems, 1999

The isentropic change of an ideal gas is described by the well known relations pvk = const., Tv(k... more The isentropic change of an ideal gas is described by the well known relations pvk = const., Tv(k-1) = const. and p(1-k)Tk = const., where the exponent k is defined as the ratio of the constant pressure to the constant volume specific heat, k = Cp/Cv. The same relations can be used for real gases only if the differential isentropic changes under consideration are small. A better examination of the differential isentropic change shows that for p, v, T systems, there are three different isentropic exponents corresponding to each pair formed out of the variables p, v, T. These three exponents noted kT,p, kT,v, kp,v after the corresponding pair of variables used, are interconnected by one relation, and accordingly only two out of the three are independent. The analysis of the present paper shows the numerical values of these exponents as well as the isentropic expansion ratios for R152a in the vapor phase, presented in diagram form. It can be seen that the deviations of the three isentr...

Research paper thumbnail of Thermodynamic Analysis of Direct Injection Diesel Engines by Multi-Zone Modelling

Research paper thumbnail of Isentrope Expansion des Wasserdampfes

Brennstoff Warme Kraft, 1985

Calcul, a l'aide d'un programme d'ordinateur, et representation sous forme de graphiq... more Calcul, a l'aide d'un programme d'ordinateur, et representation sous forme de graphiques en fonction du nombre de Mach, de l'expansion isentropique de la vapeur d'eau pour des temperatures initiales de 200, 400, 600 et 800°C et un volume initial de 0,5 m 3 /kg

Research paper thumbnail of The flow of individual cylindrical gas bubbles in vertical circular tubes

Ph D Thesis Scitran Inc Santa Barbara Ca Transl into English from Eidgenoess Tech Hochschule 1967 123 P, Nov 1, 1975

Research paper thumbnail of Using a Phenomenological Multi-Zone Model to Investigate the Effect of Injection Rate Shaping on Performance and Pollutants of a DI Heavy Duty Diesel Engine

SAE Technical Paper Series, 2002

... using sophisticated 3-D CFD codes due to extremely high computational time. ... modelling of ... more ... using sophisticated 3-D CFD codes due to extremely high computational time. ... modelling of mixture formation and combustion in a DI diesel engine”, SAE Paper ... Kouremenos, DA, Rakopoulos, CD and Hountalas, DT, “Thermodynamic analysis of indirect injection diesel engines ...

Research paper thumbnail of Prechamber and main chamber insulation effects on the performance of an IDI diesel engine coupled to power turbine

Heat Recovery Systems and CHP, 1992

ABSTRACT

Research paper thumbnail of Performance of a solar driven compound NH3/H2OH2O/LiBr absorption refrigeration system in athens

Solar & Wind Technology, 1990

A solar driven, high efficiency, compound refrigeration system is considered, made up of two coop... more A solar driven, high efficiency, compound refrigeration system is considered, made up of two cooperating absorption parts, which use NH3/H2O and H2O/LiBr solutions, respectively. Solar heat is given to the vapour generator of the NH3/H2O unit, and the heat produced by the absorber and the condenser of this unit is supplied to the vapour generator of the H2O/LiBr unit. A method for simulating the operation of the compound system has been developed and applied for predicting the hour by hour performance of the system operating during the typical year in Athens, for which solar radiation and ambient temperature data are available. An optimization study for the compound and the individual cycles has also been made. Very high performance of the system has been predicted. For example, on 21 May, the calculated theoretical coefficient of performance is 219% while the corresponding theoretical values of single H2O/LiBr and NH3/H2O units are 93% and 65% respectively. The corresponding calculated cooling power produced by the system is 543 W/m2-collector. An annual analysis shows that the cooling produced by a NH3/H2O unit in Athens is 0.87 GJ/m2-year, while the present compound system gives an impressive increase to 3 GJ/m2-year.

Research paper thumbnail of Ideal gas relations for the description of the real gas isentropic changes

Forschung im Ingenieurwesen, 1985

Research paper thumbnail of Die Anwendung der Redlich-Kwong-Zustandsgleichung zum Beschreiben des thermodynamischen Verhaltens der realen Gase

Forschung im Ingenieurwesen, 1991

Research paper thumbnail of The Effect of EGR on the Performance and Pollutant Emissions of Heavy Duty Diesel Engines Using Constant and Variable AFR

SAE Technical Paper Series, 2001

... The work is applied on a single cylinder truck test engine developed under a project funded b... more ... The work is applied on a single cylinder truck test engine developed under a project funded by the ... Desantes, JM, Arregle, J., Molina, SA and Lejeune, M., “Influence of the EGR Rate, Oxygen Concentration and ... ASME, J. Engng for Gas Turbines and Power, 112, 138-149, 1990. ...

Research paper thumbnail of Über die reduzierten Isentropenexponenten des Wasserdampfes

Forschung im Ingenieurwesen, 1989

ZusammenfassungEs wurde bereits bewiesen, daß es drei Isentropenexponenten gibt, nämlich kpv, kTp... more ZusammenfassungEs wurde bereits bewiesen, daß es drei Isentropenexponenten gibt, nämlich kpv, kTp und kTv. Wenn sie an Stelle des bekannten Exponenten k=cp/cv benutzt werden, könnte man mit Hilfe der einfachen Beziehungen des idealen Gases differentielle isentrope Zustandsänderungen eines realen Gases mit großer Genauigkeit beschreiben. Ferner ergibt sich für die Schallgeschwindigkeit α eines realen Gases die einfache Gleichung α=(kpvpv)1/2.Sowohl die drei Isentropenexponenten als auch die Schallgeschwindigkeit α eines realen Gases können nur dann berechnet werden, wenn ihre thermischen und kalorischen Zustandsgleichungen bekannt sind. Dies ist aber nur für wenige reale Gase der Fall. Zur Vermeidung dieses Hindernisses wurde versucht, Beziehungen zur Berechnung der Schallgeschwindigkeit und der Isentropenexponenten eines realen Gases mit Hilfe der allgemein gültigen Redlich-Kwong-Zustandsgleichung anzugeben. Die Ergebnisse werden in einer allgemeinen Form durch die reduzierte Temperatur, das reduzierte Volumen und den Kompressibilitätskoeffizienten—d.h. unabhängig von den Eigenschaften des realen Gases—erhalten und im Z,pr-Diagramm aufgetragen. Um die Genauigkeit des beschriebenen Verfahrens zu prüfen, wurden die reduzierten Werte der entsprechenden Größen für den Wasserdampf mit Hilfe seiner thermischen und kalorischen Zustandsgleichungen ermittelt und ebenfalls in den Diagrammen aufgetragen. Es wird eine starke Druckabhängigkeit der betreffenden Größen festgestellt. Ferner ergibt sich, daß die Redlich-Kwong-Zustandsgleichung nur für Überschlagsrechnungen herangezogen werden kann.

Research paper thumbnail of Second law analysis of non-equilibrium fluid streams

Forschung im Ingenieurwesen, 1989

Research paper thumbnail of Thermodynamic determination of the top dead centre of diesel engines

Forschung im Ingenieurwesen, 1987

Research paper thumbnail of The normal shock waves of real gases and the generalized isentropic exponents

Forschung im Ingenieurwesen, 1986

Research paper thumbnail of Experimental Investigation of the Effect of Fuel Composition on the Formation of Pollutants in Direct Injection Diesel Engines

SAE Technical Paper Series, 1999

Research paper thumbnail of Development of a Detailed Friction Model to Predict Mechanical Losses at Elevated Maximum Combustion Pressures

SAE Technical Paper Series, 2001

Abstract Engineers use phenomenological simulation models to determine engine performance. Using ... more Abstract Engineers use phenomenological simulation models to determine engine performance. Using these models, we can predict with reasonable accuracy the heat release rate mechanism inside the engine cylinder, which enables us to obtain a ...

Research paper thumbnail of Use of helium instead of hydrogen in inert gas absorption refrigeration

International Journal of Refrigeration, 1988

Abstract The behaviour of helium in place of hydrogen as a pressure equalizing gas in triple-flui... more Abstract The behaviour of helium in place of hydrogen as a pressure equalizing gas in triple-fluid absorption refrigeration units is examined. The main thermodynamic and transport properties of the real NH3/He binary gas mixture are presented in the form of diagrams and analytical expressions, with the temperature and the mass fraction of the mixture as input variables. Among others, the mass or mole fraction of the NH3/He gas mixture as a function of the dry and wet bulb temperatures has been plotted. A computer simulation has been developed to calculate the evaporation of NH3 in a NH3/He atmosphere within an insulated tube, allowing measurement of the composition of the mixture via temperature measurement. The results are compared with the corresponding values of evaporation of NH3 in a NH3/H2 atmosphere.

Research paper thumbnail of On the three exponents of the isentropic change of the refrigerant R22

International Journal of Heat and Fluid Flow, 1986

Research paper thumbnail of Sound velocity and isentropic exponents of real air on its compressibility chart

International Journal of Heat and Fluid Flow, 1991

... classical exponent k=cJc, in the ideal-gas isentropic-change equations, may be applied with g... more ... classical exponent k=cJc, in the ideal-gas isentropic-change equations, may be applied with great ... the developed relations may be employed not only in the field of thermodynamics but also ... between the air and other real gases for the purpose of drawing generalized conclusions ...