Thermodynamic Cycle Efficiency Research Articles

Analysis of the superheated steam cycle of a PWR secondary system

AbstractThe impacts of variations of turbine exhaust steam wetness, live steam parameters, and the turbine sectional pressure ratio on the thermodynamic efficiency of the saturated steam cycle in a PWR secondary system are analyzed. The effects of live steam parameters and turbine sectional pressure ratio on the thermodynamic efficiency and the turbine exhaust steam wetness for the superheated steam cycle are also investigated. The optimum ranges of operating parameters are proposed based on the comparison of the performance of the superheated steam cycle with that of the saturated steam cycle. © 2001 Scripta Technica, Heat Trans Asian Res, 30(3): 185–194, 2001

A conceptual scheme for electrical power generation from nuclear waste heat using liquid metal magnetohydrodynamic energy converter

A novel conceptual scheme has been proposed for utilizing the nuclear waste for electrical power generation by using a Liquid Metal Magnetohydrodynamic Energy Converter (LMMHDEC). The heat released during interim storage of the vitrified nuclear waste is used for this purpose. Possible modifications in the canister design for obtaining a higher air outlet temperature have been suggested. The basic design details of the LMMHD gravitational type energy converter is presented, and based on this model, various important parameters of the LMMHDEC system, suitable for coupling to the nuclear waste, are obtained. The gross thermodynamic cycle efficiency varies from 4.9% at a cycle temperature of 450 K to 20.1% at a cycle temperature of 570 K. Detailed engineering and economic studies are yet to be undertaken. However, in view of the minor modifications that are required in the existing canister system, this study suggests that it is possible to generate electrical power from nuclear waste heat using a LMMHDEC.

Refrigerants and energy efficiency

Environmental concerns ( i.e. ozone depletion and greenhouse warming) are forcing major shifts from traditional choices of refrigerant working fluids for individual systems and for specific applications. Energy efficiency has taken on new urgency to mitigate fossil fuel demands and the associated effects on greenhouse warming while allowing for future growth of refrigerant demand. Energy efficiency has thus become an increasingly important parameter and a key focus in the refrigerant selection process. Efforts to generically rank refrigerants with respect to their inherent thermodynamic efficiencies have thus far not proven to be very productive. Much conflicting information has surfaced as to the true impacts on energy demand of various candidate fluids. It is apparent that much more than a simple thermodynamic cycle efficiency is involved. Other factors may have an equal or even greater impact on the ultimate energy demands associated with any particular working fluid and/or system design. Even calorimeter testing may prove misleading in the absence of appropriate optimization. This paper discusses individual sources of inefficiency inherent in every real system and attempts to define key fluid characteristics associated with optimizing or degrading the effectiveness of individual system components and the overall system. Relative compressor efficiencies, heat transfer effectiveness, pressure drop impacts, etc., will be addressed.

Theoretical limits of engine economy with alternative automotive fuels

Calculations have been made of the theoretical limits of engine efficiency for various fuels. Considered were methanol, ethanol, benzene, iso-octane, ethane and methane. The ideal Otto cycle was used for the calculations, since it represents the upper limit for fast-burn adiabatic engines. At the conditions explored, small differences in thermodynamic cycle efficiency of under 2 per cent exist among the various fuels. These differences can be explained by the thermodynamic properties of the fuel/air mixtures themselves.

Direct conversion of thermonuclear plasma energy by high magnetic compression and expansion

We consider the useful work output from the magnetic compression, decompression and α-particle energy deposition of a single cycle of a D-T θ-pinch reactor. The intrinsic thermodynamic efficiency of the direct conversion cycle from α-particle energy to work is 62%. The direct-conversion output work is available to the reactor system at essentially 100% efficiency, and has an appreciable effect on the circulating power fraction and plant efficiency.

Efficiencies, Thermodynamics and the By-Pass Engine

I Think Mr. Filleul's main point, (in the November Journal) somewhat hidden behind some obscure comments about Carnot engines and the like, is that in a by-pass engine with heat exchanger, the heat exchange process is making a definite alteration to the thermodynamic cycle efficiency of the whole engine and not just changing the propulsive efficiency. This may or may not be an important point, depending upon the point of view of the expositor of the subject. In fact, even without heat exchange and when the by-pass compressor and turbine have realistic efficiencies, the by-pass process itself does alter in an unfavourable direction the overall thermodynamic cycle efficiency. This is one reason why in a by-pass compressor with separate jets one does not wish to make for optimum performance the by-pass and jet velocities equal.

LXXIII. Variable specific-heat corrections for the efficiency of the basic internal-combustion thermodynamic cycle and their application to the Constant-volume, Constant-pressure, Diesel and Humphrey Pump cycles

Summary The following paper is offered as a contribution to the problem of facilitating variable specific-heat analysis as applied to internal-combustion motor problems in general. The approach made to these problems is new, in so far as it involves the inclusion of a fifth ratio into the analysis of the basic internal-combustion engine cycle. This ratio, besides introducing a symmetry into the resulting expressions, also enables fairly convenient expressions to be obtained for the various thermodynamic quantities such as thermal efficiency, etc.

The Allen engine

A new method for determining the optimal heat-exchanger layout in a heat recovery steam generator and its operating parameters are presented in this paper. A robust mathematical model is developed, where arbitrary steam-pressure levels and steam-reheating levels can be set. The method considers all the possible heat-exchanger layouts, in both serial and parallel arrangements of steam pressure levels or steam reheating levels. The maximum thermodynamic efficiency of the steam-turbine cycle is set as the objective function. The results show that the optimal high pressure in heat recovery steam generator without reheating is in the region of subcritical pressures, whereas that for a heat recovery steam generator with reheating is in the region of supercritical pressures. In the case of similar water or steam temperature profiles in the heat exchangers of different steam pressure levels or reheating level, from a thermodynamic viewpoint, it is justified to use a parallel heat-exchanger arrangement.