arXiv subjects

I. Iyyappan

Publications and source records attributed to I. Iyyappan.

6 recordsLinked to original sources

arXiv2026

Fluctuation theorems for a non-Gaussian system

In this work, we numerically verify the Jarzynski equality and Crook fluctuation theorem for a Brownian particle diffusing in a heterogeneous thermal bath and hence having a non-Gaussian position distribution. We use the diffusing-diffusivity model to take the account of heterogeneity of the thermal bath where the mobility is considered as a fluctuating quantity. The Brownian particle is confined by a time-dependent harmonic potential. By changing the stiffness coefficient, we perform an isothermal process. We use the stochastic thermodynamics framework to calculate the work. We find that the Jarzynski equality and the Crook fluctuation theorem are convincingly satisfied for a non-Gaussion system. We also find that the work distribution is non-Gaussian for diffusing-diffusivity system even at a larger process time.

cond-mat.stat-mech↗

arXiv2025

Nonlinear refrigerator with a finite-sized cold heat bath

We study the refrigerator working between a finite-sized cold heat bath and an infinite-sized hot heat bath (environment) in the nonlinear response regime. We assume that the initial temperature $T_i$ of the finite-sized cold heat bath satisfies $T_i\leq T_h$, where $T_h$ is the temperature of the hot heat bath. By consuming the input power, the refrigerator transfers the heat from a finite-sized cold heat bath to the hot heat bath. Hence, the temperature of the finite-sized cold heat bath decreases until it reaches the desired low-temperature $T_f$. By minimizing the input work for the heat transport process, we derive the optimal path for temperature change. We calculate the coefficient of performance as a function of average input power. We also obtain the bounds for the coefficient of performance by applying the asymmetric dissipation limits. For the parameter values considered in this study, we observe that the relation between the coefficient of performance and the average input power strongly depends on the nature of the finite-sized heat cold bath.

cond-mat.stat-mech↗

arXiv2024

Brownian yet Non-Gaussian Heat Engine

We investigate the performance of a Brownian heat engine working in a heterogeneous thermal bath where the mobility fluctuates. Brownian particle is trapped by the time-dependent harmonic potential, by changing the stiffness coefficient and the bath temperatures, we perform a Stirling cycle. We numerically evaluated the average work, power and efficiency. We compare our results with the Brownian heat engine working in a homogeneous thermal bath. We find that for the normal diffusive system, the performance of a Gaussian heat engine serves as an upper bound. We also observe that the non-Gaussian position distribution decreases the stochastic heat engine performance.

cond-mat.stat-mech↗

arXiv2019

Efficiency of a two-stage heat engine at optimal power

We propose a two-stage cycle for an optimized linear-irreversible heat engine that operates, in a finite time, between a hot (cold) reservoir and a finite auxiliary system acting as a sink (source) in the first (second) stage. Under the tight-coupling condition, the engine shows the low-dissipation behavior in each stage, i.e. the entropy generated depends inversely on the duration of the process. The phenomenological dissipation constants are determined within the theory itself in terms of the heat transfer coefficients and the heat capacity of the auxiliary system. We study the efficiency at maximum power and highlight a class of efficiencies in the symmetric case that show universality up to second order in Carnot efficiency, while Curzon-Ahlborn efficiency is obtained as the lower bound for this class.

cond-mat.stat-mech↗

arXiv2018

General relations between the power, efficiency and dissipation for the irreversible heat engines in the nonlinear response regime

We derive the general relations between the maximum power, maximum efficiency and minimum dissipation for the irreversible heat engine in nonlinear response regime. In this context, we use the minimally nonlinear irreversible model and obtain the lower and upper bounds of the above relations for the asymmetric dissipation limits. These relations can be simplified further when the system possesses the time-reversal symmetry or anti-symmetry. We find that our results are the generalization of various such relations obtained earlier for different heat engines.

cond-mat.stat-mech↗

arXiv2017

Thermoelectric energy converters under a trade-off figure of merit with broken time-reversal symmetry

We study the performance of a three-terminal thermoelectric device such as heat engine and refrigerator with broken time-reversal symmetry by applying the unified trade-off figure of merit ($\dotΩ$ criterion) which accounts for both useful energy and losses. For heat engine, we find that a thermoelectric device working under the maximum $\dotΩ$ criterion gives a significantly better performance than a device working at maximum power output. Within the framework of linear irreversible thermodynamics such a direct comparison is not possible for refrigerators, however, our study indicates that, for refrigerator, the maximum cooling load gives a better performance than the maximum $\dotΩ$ criterion for a larger asymmetry. Our results can be useful to choose a suitable optimization criterion for operating a real thermoelectric device with broken time-reversal symmetry.

cond-mat.stat-mech↗