Ali Kodal

Efficiency of a Joule-Brayton engine at maximum power density

A new kind of power analysis is conducted on a reversible Joule-Brayton cycle. Although many performance analyses have been carried out resulting in famous efficiencies (Carnot, Curzon-Ahlborn), most do not consider the sizes of the engines. In the studies of Curzon and Ahlborn and others, researchers utilized the thermal efficiency at maximum power as an efficiency standard for practical heat engines. In this paper, instead of just maximizing power for certain cycle parameters, the power density defined as the ratio of power to the maximum specific volume in the cycle, is maximised. Therefore the effects of the engine sizes were included in the analysis. The result showed a new type of efficiency at the maximum power density which is always greater than that at the maximum power (Curzon-Ahlborn efficiency). Evaluations show that design parameters at the maximum power density lead to smaller and more efficient Joule-Brayton engines.

Effects of internal irreversibility and heat leakage on the finite time thermoeconomic performance of refrigerators and heat pumps

By using finite time thermodynamic theory, a performance analysis based on the thermoeconomic criterion has been performed for an irreversible refrigerator and a heat pump. The thermoeconomic objective function is defined as the cooling load for the refrigerator and the heating load for the heat pump per unit total cost. The optimal performances and design parameters which maximize the objective functions are investigated. The design parameters under the optimal conditions have been derived analytically, and then, the effects of internal irreversibility, heat leakage and the economical parameter on the global and optimal performances have been discussed.

Maximum power density analysis of an irreversible Joule - Brayton engine

A performance analysis based on a power density criterion has been carried out for an irreversible Joule - Brayton (JB) heat engine. The results obtained were compared with those of a power performance criterion. It is shown that design parameters at maximum power density lead to smaller and more efficient JB engines than an engine working at maximum power output conditions. Due to irreversibilities in the heat engine, the power and thermal efficiency will reduce by a certain amount, however the maximum power density conditions still give a better performance than at the maximum power output conditions. The analysis demonstrated in this paper may provide a basis for the determination of optimal operating conditions and the design parameters for real JB heat engines.

Finite time thermoeconomic optimization for endoreversible refrigerators and heat pumps

This paper reports a new kind of finite time thermoeconomic optimization for an endoreversible refrigerator and a heat pump. The cooling load for the refrigerator and the heating load for the heat pump per unit total cost are proposed as objective functions for the optimization. The optimum performance parameters which maximize the objective functions are investigated. Since the optimization technique consists of both investment and energy consumption costs, the obtained results are more general and realistic.

Thermoeconomic optimization for irreversible absorption refrigerators and heat pumps

A performance analysis using finite time thermodynamic based on a thermoeconomic objective function has been performed for absorption irreversible refrigerators and heat pumps. The optimal design parameters at the maxima of the thermoeconomic objective functions for an absorption refrigerator and heat pump have been derived analytically, and the effects of the internal irreversibility, the economical parameter and the external temperatures on the global and optimal performances have been discussed.

Performance analysis of an endoreversible heat engine based on a new thermoeconomic optimization criterion

A new kind of finite time thermoeconomic optimization analysis for an endoreversible heat engine has been performed. The objective function has been taken as the power output per unit total cost. The optimum performance parameters that maximize the objective function are investigated. In this perspective, some analytical equations for the optimum working fluid temperatures, optimum thermal efficiency, optimal distributions of heat exchanger areas and optimum specific power output were found in terms of economical and technical parameters. The effects of the design parameters on the optimal conditions have been discussed.

A comparative performance analysis of irreversible regenerative reheating Joule-Brayton engines under maximum power density and maximum power conditions

A performance analysis based on the maximum power density criterion has been carried out for an irreversible regenerative reheating Joule-Brayton engine. The obtained results were compared with those obtained using the maximum power performance criterion. The design parameters under the optimal conditions have been derived analytically and their effects on the engines performance have been discussed. The overall effects of reheating, regeneration and internal irreversibilities are investigated. The obtained results may provide a general theoretical tool for the optimal design and operation of real non-regenerative and regenerative reheating gas turbines.

Performance optimization of a new combined power cycle based on power density analysis of the dual cycle

Abstract In this paper, maximum power density (MPD) analysis of an air standard internal combustion Dual cycle has been performed. Based on the obtained results for MPD analysis of the Dual cycle, a new combined power cycle model (Dual+Joule-Brayton) has been introduced and optimized. Optimal performance and design parameters are obtained analytically under the MPD conditions of the Dual cycle. The obtained results are discussed in terms of thermal efficiency, power and engine sizes. It is shown that for the combined cycle, a design based on the MPD conditions is more advantageous from the point of view of engine sizes and thermal efficiency.

Finite size thermoeconomic optimization for irreversible heat engines

An optimization analysis for an irreversible heat engine has been carried out based on a new thermoeconomic optimization criterion. The thermoeconomical objective function has been taken as the power output per unit total cost. In the analysis, the irreversibility effects due to heat transfer across finite temperature differences, the heat leak loss between the external heat reservoirs and internal dissipation of the working fluid are taken into account. The maximum of the objective function and the corresponding optimal conditions has been derived analytically. The effects of technical and economical parameters on the global and optimal performances have been investigated.

Thermoeconomic optimization of a two stage combined refrigeration system: a finite-time approach

A finite-time thermoeconomic performance analysis based on a new kind of optimization criterion has been carried out for a two-stage endoreversible combined refrigeration cycle model. The optimal performances and design parameters that maximize the objective function (cooling load per total cost) are investigated. In this context, the optimal temperatures of the working fluids, the optimum performance coefficient, the optimum specific cooling load and the optimal distribution of the heat exchanger areas are determined in terms of technical and economical parameters. The effects of the economical parameter that characterizes the investment and energy consumption costs on the general and the optimal performances have been discussed.