This work presents the comparison between experimental and theoretical results obtained for three straight annular seals. One of the annular seals has smooth rotor and stator while the others have a textured stator; the textures are equally spaced shallow round holes, with two different depths. The experimental results were obtained on a test rig dedicated to the identification of the dynamic coefficients of high Reynolds bearings and annular seals. The test rig uses hot water (<50 °C) as a working fluid. Dynamic excitations imposed by piezoelectric shakers to the rotor enable the identification of dynamic coefficients via complex impedances. Theoretical results compared with experimental findings were obtained by numerically solving the “bulk flow” equations (film thickness averaged equations dominated by inertia effects). The numerical model was extensively validated for smooth annular seals but is less confident for textured surfaces. The present comparisons between experimental and numerical results enable to estimate the accuracy of the numerical model employed for the textured seals.

The partly hot-water driven CO 2 capture plant offers a significant potential for improvement in performance when implemented in a combined-cycle power plant (CCPP). It is possible to achieve the same performance with a dual-pressure steam cycle as in a triple-pressure unit. Even a single-pressure plant can attain an efficiency competitive with that achievable with a triple-pressure plant without the hot-water reboiler. The underlying reasons are better heat utilization in the heat recovery unit and less steam extraction to the absorbent regenerating unit(s). In this paper, the design criteria for a combined cycle power plant utilizing hot-water absorbent regeneration will be examined and presented. The results show that the most suitable plant is one with two steam pressure levels. The low-pressure level should be much higher than in a conventional combined cycle in order to increase the amount of heat available in the economizer. The external heat required in the CO 2 capture plant is partly supplied by the economizer, allowing temperature optimization in the unit. The maximum value of the low-pressure level is determined by the reboiler, as too great a temperature difference is unfavorable. This work evaluates the benefits of coupling the economizer and the reboiler in a specially designed CCPP. In the CO 2 separation plant both monoethanolamine (MEA) and ammonia are evaluated as absorbents. Higher regeneration temperatures can be tolerated in ammonia-based plants than in MEA-based plants. When using a liquid heat carrier the reboiler temperature is not constant on the hot side, which results in greater temperature differences. The temperature difference can be greatly reduced by dividing the regeneration process into two units operating at different pressures. The possibility of extracting more energy from the economizer to replace part of the extracted steam increases the plant efficiency. The results show that very high efficiencies can be achieved without using multiple pressure-levels.

The design-point performance characteristics of a wide variety of combined-cogeneration power plants, with different amounts of supplementary firing (or no supplementary firing), different amounts of steam injection (or no steam injection), different amounts of exhaust gas condensation, etc., without limiting these parameters to present-day limits are investigated. A representative power plant with appropriate components for these plant enhancements is developed. A computer program is used to evaluate the performance of various power plants using standard inputs for component efficiencies, and the design-point performance of these plants is computed. The results are presented as thermal efficiency, specific power, effectiveness, and specific rate of energy in district heating. The performance of the simple-cycle gas turbine dominates the overall plant performance; the plant efficiency and power are mainly determined by turbine inlet temperature and compressor pressure ratio; increasing amounts of steam injection in the gas turbine increases the efficiency and power; increasing amounts of supplementary firing decreases the efficiency but increases the power; with sufficient amounts of supplementary firing and steam injection the exhaust-gas condensate is sufficient to make up for water lost in steam injection; and the steam-turbine power is a fraction (0.1 to 0.5) of the gas-turbine power output. Regions of “optimum” parameters for the power plant based on design-point power, hot-water demand, and efficiency are shown. A method for fuel-cost allocation between electricity and hot water is recommended.

This paper is a presentation of a systematic study on externally fired gas turbine cogeneration fueled by biomass. The gas turbine is coupled in series with a biomass combustion furnace in which the gas turbine exhaust is used to support combustion. Three cogeneration systems have been simulated. They are systems without a gas turbine, with a non-top-fired gas turbine, and a top-fired gas turbine. For all systems, three types of combustion equipment have been selected: circulating fluidized bed (CFB) boiler, grate fired steam boiler, and grate fired hot water boiler. The sizes of biomass furnaces have been chosen as 20 MW and 100 MW fuel inputs. The total efficiencies based on electricity plus process heat, electrical efficiencies, and the power-to-heat ratios for various alternatives have been calculated. For each of the cogeneration systems, part-load performance with varying biomass fuel input is presented. Systems with CFB boilers have a higher total efficiency and electrical efficiency than other systems when a top-fired gas turbine is added. However, the systems with grate fired steam boilers allow higher combustion temperature in the furnace than CFB boilers do. Therefore, a top combustor may not be needed when high temperature is already available. Only one low-grade fuel system is then needed and the gas turbine can operate with a very clean working medium.

Computer models have been used to analyze the thermodynamic performance of a gas turbine (GT) cogeneration system and an internal combustion engine (IC) cogeneration system. The purpose of this study was to determine the effect of thermal matching of the load (i.e., required thermal energy) and the output steam fraction (fraction of the thermal output, steam and hot water, which is steam) on the thermodynamic performance of typical cogeneration systems at both full and partial output. The thermodynamic parameters considered were: the net heat rate (NHR), the power-to-heat ratio (PHR), and the fuel savings rate (FSR). With direct use (the steam fractions being different), the NHR of these two systems is similar at full output, the NHR of the IC systems is lower at partial output, and the PHR and the FSR of the GT systems are lower than those of the IC systems over the full range of operating conditions. With thermal matching (to produce a given steam fraction) the most favorable NHR, PHR, and FSR depend on the method of matching the load to the thermal output.

Selection criteria are developed for screening liquids for long-distance thermal energy transport. The model used in developing these criteria employs power function approximations for physical and economical relations. Its simplified version provides analytical insights into the optimal allocation of major cost components, as well as a solution for the total transmission cost. The resulting hierarchy of selection criteria can be used for fast screening and ranking of a large number of fluids, thereby eliminating the need for detailed engineering, economic, environmental, and safety studies on fluids which would ultimately prove undesirable. Representative fluids are discussed and compared with transmission by hot water. It is found that most thermal fluids can be rejected, because of less desirable physical properties compared with those of hot water, with the simplest of the criteria presented.

Steam turbines for cogeneration plants may carry a combination of industrial, space heating, cooling and domestic hot water loads. These loads are hourly, weekly, and seasonally irregular and require turbines of special design to meet the load duration curve, while generating electric power. Design features and performance characteristics of one of the largest cogeneration turbine units for combined electric generation and district heat supply are presented. Different modes of operation of the cogeneration turbine under variable load conditions are discussed in conjunction with a heat load duration curve for urban heat supply. Problems associated with the retrofitting of existing condensing type turbines for cogeneration applications are identified.

The advantages of gas turbine power plants in general and closed cycle systems under gas pressure in particular for waste heat recovery are well known. A satisfactory efficiency for electric power generation and good conditions to obtain a significant amount of hot water above 100°C lead to a high fuel utilization. However, as in most of projects, it is not much possible to produce high temperature steam or water without significantly decreasing the electricity production. A new method for an additional generation of high quality process or domestic heat is proposed. The basic feature of this method lies in arranging one or two steam generators or preheaters in parallel with the low pressure side of the recuperator. The high total efficiency and the noteworthy flexibility of this system are emphasized. This arrangement is suitable for any kind of heat source, but the applications presented in this paper are related to helium direct cycle nuclear power plants the main features of which are a single 600 MW(e) turbomachine, a turbine inlet temperature of 775°C, no or one intermediate cooling and a primary circuit fully integrated in a pre-stressed concrete reactor vessel.

Conditions leading to cavitation of liquids other than water are examined. The concept of the thermal cavitation criterion is considered in view of new test data on hot water and other liquids, and its utility for determination of NPSH corrections is demonstrated. The effect of the suction specific speed on the NPSH corrections is tentatively established.