Effect of linear variable specific heat of working medium on power efficiency performance of endoreversible Rallis cycle
An endoreversible Rallis cycle model is established by finite-time thermodynamic theory when the specific heat of working medium varies linearly with temperature.The analytical expressions of power(P)and efficiency(η)of the cycle are derived.The effects of cyclic pressurization ratio(λ),compression ratio(ε),pre-expansion ratio(ρ),heat transfer loss(B)and the coefficient of linear variation of specific heat with temperature(k1)on the characteristic curves of P and expansion ratio(σ),η and σ and,P and η are analyzed by numerical examples.The results show that the cyclic P-σ and η-σ characteristic curves are parabola-like,and the cyclic P-η characteristic curves are twisted blade shapes.There are optimum expansion ratios σP and ση,which make P and η reach the maximum(Pmax and ηmax),respectively.With the increase of ε and λ,the power(Pη)corresponding to Pmax,σP,ηmax,ση,ηmax and the efficiency(ηP)corresponding to Pmax increase monotonously.With the increase of ρ,Pmax,ηmax,ση and Pη increase monotonously,while σP remains unchanged and ηP decreases monotonically.With the increase of B and k1,ηmax and ηP decrease monotonously,and ση and Pη increase monotonously.The results are compared with the results of endoreversible Rallis cycle with constant specific heat.The results show that with the increase of ρ,σP remains unchanged,while at constant specific heat,σP increases monotonously.ηP decreases monotonously and increases monotonously at constant specific heat.Through the analysis,it can be seen that the change of specific heat of working medium has an obvious influence on the performance of Rallis cycle,and the conclusions obtained have certain reference significance for the application of this cycle.
finite time thermodynamicsendoreversible Rallis cycleworking fluid with variable specific heatsperformance optimization
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