Internal Irreversibility Parameter Research Articles

Finite time optimisation of an irreversible vapour-absorption heat transformer system

SYNOPSIS This communication presents finite time thermodynamic optimisation of a vapour-absorption heat transformer system affected by both external and internal irreversibility. External heat reservoirs (heat source/sink) have been considered of finite heat capacity. For given input heat transfer rate in the generator, the heating load has been maximised. The optimal limits for the coefficient of performance (COP) and working fluid temperatures of the system are determined at the maximum heating load. The parametric study gives the variation of maximum heating load, coefficient of performance, working fluid temperatures and heat transfer rate between the system and its thermal reservoirs, with operating variables (viz, inlet temperature of heat reservoirs, finite thermal capacitance of external fluid, effectiveness of the heat exchangers and internal irreversibility parameter).

Performance evaluation of an irreversible Stirling heat engine cycle

SYNOPSIS An irreversible heat engine model with finite heat capacity of external reservoirs is presented for the performance evaluation of a Stirling heat engine. The external irreversibilities are due to finite temperature difference between the heat engine and external reservoirs as well as the direct heat leak loss between the source and the sink, while the internal irreversibilities are due to the regenerative heat loss and the other entropy generations during the two isothermal processes within the cycle. The power output is adopted as an objective function for optimisation. The expressions for maximum power output and the corresponding thermal efficiency are derived. The effects of various parameters viz. the effectiveness on the source- and sink-side and the regenerative heat exchangers, and the internal irreversibility parameter have been studied in detail. It is found that the effectiveness of the regenerator affects only the thermal efficiency while the effectiveness of heat capacitance rates of the hot- and cold-side heat exchangers and the internal irreversibility affect both the parameters. The effects of the internal irreversibility parameter are found to be more than those of the other parameters on the maximum power output and the corresponding thermal efficiency. The results obtained by earlier workers, which represent special cases, are presented.

Ecological optimization and performance study of irreversible Stirling and Ericsson heat engines

The concept of finite time thermodynamics is used to determine the ecological function of irreversible Stirling and Ericsson heat engine cycles. The ecological function is defined as the power output minus power loss (irreversibility), which is the ambient temperature times, the entropy generation rate. The ecological function is maximized with respect to cycle temperature ratio and the expressions for the corresponding power output and thermal efficiency are derived at the optimal operating conditions. The effect of different operating parameters, the effectiveness on the hot, cold and the regenerative side heat exchangers, the cycle temperature ratio, heat capacitance ratio and the internal irreversibility parameter on the maximum ecological function are studied. It is found that the effect of regenerator effectiveness is more than the hot and cold side heat exchangers and the effect of the effectiveness on cold side heat exchanger is more than the effectiveness on the hot side heat exchanger on the maximum ecological function. It is also found that the effect of internal irreversibility parameter is more than the other parameters not only on the maximum ecological function but also on the corresponding power output and the thermal efficiency.

Ecological optimization and parametric study of irreversible Stirling and Ericsson heat pumps

This communication presents the ecological optimization and parametric study of irreversible Stirling and Ericsson heat pump cycles, in which the external irreversibility is due to finite temperature difference between working fluid and external reservoirs while the internal irreversibilities are due to regenerative heat loss and other entropy generations within the cycle. The ecological function is defined as the heating load minus the irreversibility (power loss) which is ambient temperature times the entropy generation. The ecological function is optimized with respect to working fluid temperatures, and the expressions for various parameters at the optimal operating condition are obtained. The effects of different operating parameters on the performance of these cycles have been studied. It is found that the effect of internal irreversibility parameter is more pronounced than the other parameters on the performance of these cycles.

Parametric study of irreversible Stirling and Ericsson cryogenic refrigeration cycles

This communication presents a parametric study of irreversible Stirling and Ericsson cryogenic refrigerator cycles including external and internal irreversibilities along with finite heat capacities of external reservoirs. The external irreversibility is due to finite temperature difference between the working fluid and external fluids in the source/sink reservoirs, while the internal irreversibilities are due to regenerative heat loss and other entropy generations in the cycle. The cooling load is maximized for the given power input. The cooling coefficient of performance, the heat transfers to and from the refrigerator and the working fluid temperatures at these conditions have been evaluated. The effect of different parameters (reservoirs fluid temperature, the effectivenesses, heat capacitance rates of the external reservoirs and irreversibility parameter) on the performance of these cycles has been studied. It is found that the effect of the internal irreversibility parameter is more pronounced than that of other parameters.

Finite time optimization of an endoreversible and irreversible vapour absorption refrigeration system

This communication presents a finite time thermodynamic optimization of a simple vapour absorption refrigeration system affected by both external and internal irreversibility. External heat reservoirs (heat source/sink) have been considered of finite heat capacity. For a given input heat transfer rate in the generator, the cooling load has been maximized. The optimal bounds for the coefficient of performance (COP) and working fluid temperatures of the absorption system are determined at the maximum cooling capacity. The parametric study gives the variation of the maximum cooling capacity, the COP, working fluid temperatures and heat transfer rate between the system and its thermal reservoirs with operating variables (viz. inlet temperature of heat reservoirs, finite thermal capacitance of external fluid, effectiveness of the heat exchangers and internal irreversibility parameter).

Performance evaluation of irreversible Stirling and Ericsson heat pump cycles

This communication presents the performance evaluation of irreversible Stirling and Ericsson Heat Pumps Cycles including external and internal irreversibilities along with finite heat capacities of external reservoirs. The external irreversibility is due to finite temperature difference between working fluid and external (source/sink) reservoirs fluid while the internal irreversibilities are due to regenerative heat loss and other entropy generation in the cycle. The heating load is maximized for the given power input. The heating coefficient of performance, the heat transfers to and from the heat pumps and the working fluid temperatures at these conditions have been evaluated. The effect of different parameters (reservoirs temperature, the various effectivenesses and irreversibility parameter), on the performance of these cycles have been studied. It is found that the effect of internal irreversibility parameter is more pronounced than that of other external irreversibility parameters.