The ideal gas Joule cycle at maximum specific work

2000 ◽  
Vol 214 (12) ◽  
pp. 1545-1551 ◽  
Author(s):  
J D Lewins
Keyword(s):  
Heat Exchanger ◽  
Ideal Gas ◽  
Specific Work ◽  
Perfect Gas ◽  
Regenerative Heat ◽  
Turbine Engine ◽  
Ideal Gases ◽  
Principal Theorem ◽  
Specific Heat Capacities ◽  
The Ideal

The condition for maximum specific work from a gas-turbine engine operated on a Joule cycle is generalized to ideal gases from the well-known result obtained by using a perfect gas. An obvious corollary is shown to be the principal theorem, when the working substance is an ideal gas with specific heat capacities varying with temperature, that the turbine outlet and compressor outlet temperatures are equal. Two additional corollaries are shown to hold in general. A simple study shows that the optimum condition point is not much affected by real departures from reversible behaviour. The condition for which a regenerative heat exchanger is then desirable is found. The results are generalized to any gas for which the enthalpy is a function of temperature only.

Ideal gas processes – and two ideal gas case studies too

2018 ◽  
Author(s):  
Dennis Sherwood ◽  
Paul Dalby
Keyword(s):  
Case Studies ◽  
Constant Pressure ◽  
Ideal Gas ◽  
Heat Capacities ◽  
Carnot Cycle ◽  
State Function ◽  
Ideal Gases ◽  
First Case ◽  
The Ideal

This chapter brings together, and builds on, the results from previous chapters to provide a succinct, and comprehensive, summary of all key relationships relating to ideal gases, including the heat and work associated with isothermal, adiabatic, isochoric and isobaric changes, and the properties of an ideal gas’s heat capacities at constant volume and constant pressure. The chapter also has two ‘case studies’ which use the ideal gas equations in broader, and more real, contexts, so showing how the equations can be used to tackle, successfully, more extensive systems. The first ‘case study’ is the Carnot cycle, and so covers all the fundamentals required for the proof of the existence of entropy as a state function; the second ‘case study’ is the ‘thermodynamic pendulum’ – a system in which a piston in an enclosed cylinder oscillates to and fro like a pendulum under gravity, in both the absence, and presence, of friction.

Optimising an Intercooled Compressor for an Ideal Gas Model

2003 ◽  
Vol 31 (3) ◽  
pp. 189-200 ◽  
Author(s):  
Jeffery D. Lewins
Keyword(s):  
Equation Of State ◽  
Specific Heat ◽  
Ideal Gas ◽  
Heat Capacities ◽  
Perfect Gas ◽  
Temperature Dependent ◽  
Specific Heat Capacities ◽  
Ideal Gas Model

Many of the conventional results obtained when optimising the performance of an intercooler during compression using a perfect gas model can be obtained when the restrictions of the model are relaxed to an ideal gas. That is, we now have temperature-dependent specific heat capacities but retain the equation of state pV = RT. This note illustrates the theme.

Ideal gases and the ideal gas laws

Thermofluids ◽  
1996 ◽  
pp. 106-122
Author(s):  
Keith Sherwin ◽  
Michael Horsley
Keyword(s):  
Ideal Gas ◽  
Gas Laws ◽  
Ideal Gases ◽  
The Ideal

The Effect of Gas Models on Compressor Efficiency Including Uncertainty

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Fangyuan Lou ◽  
John Fabian ◽  
Nicole L. Key
Keyword(s):  
Pressure Ratio ◽  
Ideal Gas ◽  
Experimental Measurements ◽  
Perfect Gas ◽  
Real Gas ◽  
The Real ◽  
Compressor Efficiency ◽  
Ideal Gas Model ◽  
Isentropic Efficiency ◽  
The Ideal

Since isentropic efficiency is widely used in evaluating the performance of compressors, it is essential to accurately calculate this parameter from experimental measurements. Quantifying realistic bounds of uncertainty in experimental measurements are necessary to make meaningful comparisons to computational fluid dynamics simulations. This paper explores how the gas model utilized for air can impact not only the efficiency calculated in an experiment, but also the uncertainty associated with that calculation. In this paper, three different gas models are utilized: the perfect gas model, the ideal gas model, and the real gas model. A commonly employed assumption in calculating compressor efficiency is the perfect gas assumption, in which the specific heat, is treated as a constant and is independent of temperature and pressure. Results show significant differences in both calculated efficiency and the resulting uncertainty in efficiency between the perfect gas model and the real gas model. The calculated compressor efficiency from the perfect gas model is overestimated, while the resulting uncertainties from the perfect gas model are underestimated. The ideal gas model agrees well with the real gas model, however. Including the effect of uncertainty in gas properties results in very large uncertainties in isentropic efficiency, on the order of ten points, for low pressure ratio machines.

Ideal gases and the ideal gas laws

Thermofluids ◽  
1996 ◽  
pp. 21-23
Author(s):  
Keith Sherwin ◽  
Michael Horsley
Keyword(s):  
Ideal Gas ◽  
Gas Laws ◽  
Ideal Gases ◽  
The Ideal

Waste Energy Utilization in Regenerative Gas Turbine Cycles

1986 ◽  
Author(s):  
Yousef S. H. Najjar ◽  
Taha K. Aldoss
Keyword(s):  
Heat Exchanger ◽  
Gas Turbine ◽  
Power Output ◽  
Energy Utilization ◽  
Inlet Pressure ◽  
Maximum Temperature ◽  
Regenerative Heat ◽  
Turbine Engine ◽  
Turbine Inlet ◽  
Delivery Pressure

One of the ways that can be used to increase the efficiency of a shaft gas turbine engine is by installing a regenerative heat exchanger in one of the following two configurations: 1. after the low pressure turbine (usual case). 2. after the high pressure turbine (suggested). Analysis of ideal cycles as well as real cycle for both configurations is done by using a computer program, where the following parameters were studied: heat exchanger effectiveness, turbine efficiency, compressor efficiency, ratio of turbine inlet pressure to compressor delivery pressure (P3/P2), and maximum temperature ratio (T3/T1). From the sensitivity analysis for both configurations the usual configuration is inferior to the suggested in terms of the relative effects of compressor and turbine efficiencies on the overall efficiency and turbine inlet pressure on overall thermal efficiency and power output. However, the usual method is superior with respect to the relative effects of the compressor and turbine efficiencies on power output and flow path design and manufacture.

scholarly journals Analysis of Pressure Pulsation Influence on Compressed Natural Gas (CNG) Compressor Performance for Ideal and Real Gas Models

2019 ◽  
Vol 9 (5) ◽  
pp. 946 ◽  
Author(s):  
Zhan Liu ◽  
Wenguang Jia ◽  
Longhui Liang ◽  
Zhenya Duan
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Ideal Gas ◽  
Specific Work ◽  
Real Gas ◽  
The Real ◽  
Compressor Performance ◽  
Ideal Gas Model ◽  
The Ideal

This work investigates the effects of pressure pulsations on reciprocating natural gas compressor performance thermodynamically. A nonlinear hybrid numerical model is thus developed to consider the interaction between the compressor and the pipeline system. The suction chamber, compressor cylinder and discharge chamber are modelled integrally based on the first law of thermodynamics and mass balance, and the pipeline flow is described by using the gas dynamic model. Methane is considered as the working fluid and its properties are computed based on ideal and real gas assumptions. For the real gas model, the methane properties are obtained by means of calling the NIST REFPROP database. The validity of numerical results is confirmed by previous experimental values. Results from the examinations of pressure pulsation influence demonstrate that discharge resonance requires more specific work than suction resonance in the same harmonic; in the suction system, the first harmonic response reduces the mass flow rate but significantly increases specific work, and the second harmonic response has a strong supercharging effect but the specific work is increased slightly; in the discharge system, the mass flow rate is changed little by pressure pulsations, but the indicated power and specific work are increased significantly; for the real gas model, the in-cylinder temperature during the compression and discharge phases, mass flow rate and indicated power are higher than those for the ideal gas model, whereas the specific work is less for the real gas model than for the ideal gas model.

The Effect of Gas Models on Compressor Efficiency Including Uncertainty

2013 ◽  
Author(s):  
Fangyuan Lou ◽  
John Fabian ◽  
Nicole L. Key
Keyword(s):  
Pressure Ratio ◽  
Ideal Gas ◽  
Experimental Measurements ◽  
Perfect Gas ◽  
Real Gas ◽  
The Real ◽  
Compressor Efficiency ◽  
Ideal Gas Model ◽  
Isentropic Efficiency ◽  
The Ideal

Since isentropic efficiency is widely used in evaluating the performance of compressors, it is essential to accurately calculate this parameter from experimental measurements. Quantifying realistic bounds of uncertainty in experimental measurements are necessary to make meaningful comparisons to CFD simulations. This paper explores how the gas model utilized for air can impact not only the efficiency calculated in an experiment but also the uncertainty associated with that calculation. In this paper, three different gas models are utilized: the perfect gas model, the ideal gas model, and the real gas model. A commonly employed assumption in calculating compressor efficiency is the perfect gas assumption, in which the specific heat, is treated as a constant and is independent of temperature and pressure. Results show significant differences in both calculated efficiency and the resulting uncertainty in efficiency between the perfect gas model and the real gas model. The calculated compressor efficiency from the perfect gas model is overestimated, while the resulting uncertainties from the perfect gas model are underestimated. The ideal gas model agrees well with the real gas model, however. Including the effect of uncertainty in gas properties results in very large uncertainties in isentropic efficiency, on the order of 10 points, for low pressure ratio machines.

scholarly journals ANALYSIS OF LOW-TEMPERATURE EXPANSION PROCESSES OF NON-IDEAL GASES

2021 ◽  
Vol 2 (11(75)) ◽  
pp. 53-63
Author(s):  
N. Habibova
Keyword(s):  
Low Temperature ◽  
Energy Analysis ◽  
Ideal Gas ◽  
Chemical Technology ◽  
Cooling Effect ◽  
Adiabatic Expansion ◽  
Temperature Expansion ◽  
Ideal Gases ◽  
Ideal Gas Model ◽  
The Ideal

An energy analysis of the processes of obtaining and using artificial cold in chemical technology is presented. The most well-known methods of obtaining and applying the cooling effect are considered: adiabatic expansion of vapor and gaseous bodies in expanders, throttling. Special attention is paid to the effect of object deviation from the ideal gas model.

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