S. K. Tyagi

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.

Ecological Optimization and Parametric Study of an Irreversible Regenerative Modified Brayton Cycle with Isothermal Heat Addition

An ecological optimization along with a detailed parametric study of an irreversible regenerative Brayton heat engine with isothermal heat addition have been carried out with external as well as internal irreversibilities. The ecological function is defined as the power output minus the power loss (irreversibility) which is ambient temperature times the entropy generation rate. The external irreversibility is due to finite temperature difference between the heat engine and the external reservoirs while the internal irreversibilities are due to nonisentropic compression and expansion processes in the compressor and the turbine respectively and the regenerative heat loss. The ecological function is found to be an increasing function of the isothermal-, sink- and regenerative-side effectiveness, isothermal-side inlet temperature, component efficiencies and sink-side temperature while it is found to be a decreasing function of the isobaric-side temperature and effectiveness and the working fluid heat capacitance rate. The effects of the isobaric-side effectiveness are found to be more than those of the other parameters and the effects of turbine efficiency are found to be more than those of the compressor efficiency on all the performance parameters of the cycle.

Ecological optimisation of an irreversible regenerative intercooled Brayton heat engine with direct heat loss

SYNOPSIS The ecological function, which is defined as the power output minus the power loss (irreversibility), has been optimised with respect to working fluid temperatures and the optimal performance parameters of an irreversible regenerative intercooled Brayton heat engine with direct heat loss are calculated for a typical set of operating conditions. The effects of the source-side effectiveness are found to be greater than those of the other side effectiveness not only on the maximum ecological function but also on the corresponding power output and thermal efficiency. This particular result is different from those obtained by earlier workers available in the literature. Again, the effects of the turbine efficiency are found to be greater than those of the compressor efficiencies on all the performance parameters for the same set of operating conditions. On the other hand, there exist the optimum values of intercooling and cycle pressure ratios at which the cycle attains the maximum ecological function and the corresponding power output and thermal efficiency for a given set of operating parameters.

Thermoeconomic optimization and parametric study of an irreversible Stirling heat pump cycle

The thermo-economic optimization of an irreversible Stirling heat pump cycle with a detail parametric study for the finite heat capacity of external reservoirs is presented in this article. The external irreversibility is due to finite temperature difference between the working fluid and the external reservoirs while the internal irreversibility is due to the regenerative heat loss. The Thermo-economic function is defined as the heating load divided by the total cost of the system along with the running cost. The Thermo-economic function is optimized with respect to the working fluid temperatures and the values for various parameters at the optimal operating condition are calculated. The effects of different operating parameters on the performance of the cycle have been studied. It is found that the effect of regenerative effectiveness and the economic parameter are more pronounced than that of the other parameters.

Optimum Criteria on the Performance of an Irreversible Braysson Heat Engine Based on the new Thermoeconomic Approach

An irreversible cycle model of a Braysson heat engine operating between two heat reservoirs is used to investigate the thermoeconomic performance of the cycle affected by the finite-rate heat transfer between the working fluid and the heat reservoirs, heat leak loss from the heat source to the ambient and the irreversibility within the cycle. The thermoeconomic objective function, defined as the total cost per unit power output, is minimized with respect to the cycle temperatures along with the isobaric temperature ratio for a given set of operating parameters. The objective function is found to be an increasing function of the internal irreversibility parameter, economic parameters and the isobaric temperature ratio. On the other hand, there exist the optimal values of the state point temperatures, power output and thermal efficiency at which the objective function attains its minimum for a typical set of operating parameters. Moreover, the objective function and the corresponding power output are also plotted against the state point temperature and thermal efficiency for a different set of operating parameters. The optimally operating regions of these important parameters in the cycle are also determined. The results obtained here may provide some useful criteria for the optimal design and performance improvements, from the point of view of economics as well as from the point of view of thermodynamics of an irreversible Braysson heat engine cycle and other similar cycles as well.

Year round performance and economic evaluation of solar power plant for Indian tropical condition

In this paper, a 50 MWe design capacity solar parabolic dish concentrator Stirling engine power plant (SPDCSPP) has been modeled for analysis, where 2000 units of 25 kWe parabolic dish concentrator each considered for getting desired capacity. An attempt has been made to carryout the economic evaluation of SPDCSPP for selected Indian tropical condition. Variations of the efficiency of Stirling engine power plant at the variation of the load conditions are considered for year round performance evaluation. The developed model is examined for Indian location, i.e., Delhi. It is found that year round collector-receiver efficiency varies from 69.43% to 77.88%, and overall power plant efficiency varies from 16.86% and 25.79%. The installation cost per MWe electrical capacity is 15.32 crore rupees, and 28.10 lakhs rupees as operation and maintenance cost per MWe electrical capacity. The unit cost of electric energy generation (kWhe) is about 11.06 Indian rupees, with 30 years lifespan of the plant and 10% intere...

Important optimum criteria on the performance parameters of an irreversible Brayton heat engine

SYNOPSIS An irreversible cycle model of a Brayton heat engine is presented in this paper. The internal irreversibility is due to nonisentropic processes in the compressor and turbine while the external irreversibility is due to finite temperature differences between the external heat reservoirs and the heat engine. The power output is maximised with respect to the working fluid temperatures and the pressure ratio of two isobaric processes. It is found that there are optimal values of the pressure ratio and cycle temperatures at which the power output attains its maximum for a typical set of operating parameters. Some optimum criteria for the important parameters such as power output, thermal efficiency, pressure ratio, temperatures of the working fluid in the two isobaric processes, and heat transfer area ratios, are obtained. The important problems concerning the optimal design and operation of Brayton heat engines are discussed in detail.