arXiv subjects

Rajeshree Chakraborty

Publications and source records attributed to Rajeshree Chakraborty.

3 recordsLinked to original sources

arXiv2026

Endoreversible Carnot machines with long-time reversible limit

The well-known Curzon-Ahlborn (CA) engine [Am. J. Phys. {\bf 43}, 22 (1975)] runs in finite time and yields a finite power output. In order to recover the standard Carnot cycle from the CA model, the limit of quasi-static operation has to be concurrent with the reversible limit, a condition strangely missing from the CA model. We augment this model by specifying the duration of the isothermal process as a monotonic decreasing function of the temperature difference between the working substance and the reservoir. As an illustration, we analyze the machine's operation in the low-dissipation (LD) regime in which the entropy production in each isothermal branch is inversely proportional to the duration of the process. The modified model, while retaining the optimal features of the CA model, also yields explicit expressions for the optimal durations of isothermal processes. We compare the optimal cycle periods of the present model and the LD model, and show their agreement in the linear response regime.

cond-mat.stat-mech↗

arXiv2026

Optimization of cooling power of a thermoelectric refrigerator: A unified approach

We analyze the steady-state formalism for optimizing the cooling power of a thermoelectric refrigerator (TER), unifying the endoreversible and exoreversible approximations within one framework. Although the cooling power is non-optimizable within the endoreversible model based on Newtonian heat-transfer law, we show that the issue can be circumvented in the near-reversible regime where the external thermal conductances are large, but finite. We extend this analysis to optimize the cooling power in the presence of both internal and external irreversibilities and derive a closed-form expression for the coefficient of performance (COP) that depends on the thermoelectric figure of merit and the ratio of internal to external thermal conductances. The model reproduces the endoreversible and the exoreversible limits as special cases. We conclude that for small temperature differences, the combined irreversibilities reduce the COP to values below 1/2, which aligns with the observed performance of the single-stage TER, and can provide realistic estimates for the COP.

cond-mat.stat-mech↗

arXiv2025

Optimal performance of thermoelectric devices with small external irreversibility

In the thermodynamic analysis of thermoelectric devices, typical irreversibilities are for the processes of finite-rate heat transfer, heat leak and Joule heating. Approximate analyses often focus on either internal or external irreversibility, obtaining well-known expressions for the efficiency at maximum power (EMP), such as the Curzon-Ahlborn value for endoreversible model and the Schmiedl-Seifert form for exoreversible model. Within the Constant Properties model, we simultaneously incorporate internal as well as external irreversibilities. We employ the approximation of a symmetric and small external irreversibility (SEI), allowing a tractable expression for EMP that depends on three parameters i) the ratio of internal to external thermal conductance ii) the figure of merit of the thermoelectric material and iii) the ratio of hot and cold reservoir temperatures. We study limiting forms of this EMP and compare our framework with the exact model as well as with other irreversible models in finite-time thermodynamics, such as the minimally nonlinear model. In particular, we argue that the TEG in endoreversible approximation can be mapped to the mesoscopic model of Feynman's ratchet in the high temperatures regime, thus providing an alternative to the viewpoint in literature where the TEG in linear regime is mapped to an exoreversible case. Finally, extending our study to the thermoelectric refrigerator under similar assumptions as for the generator, we analyze the efficiency at the maximum cooling power.

cond-mat.stat-mech↗