Proposal of humid air turbine cycle incorporated with absorption heat transformer

A detailed graphical exergy study based on the energy‐utilization diagram (EUD) is applied to humid air turbine (HAT) cycle incorporated with a modified two‐stage absorption heat transformer (TAHT). Employing the sensible and latent heat exchange modes in this TAHT and then introducing to the HAT cycle have clarified that this method can intensively recover the waste heat of HAT cycle and improve the system performance. Compared to a conventional HAT cycle, the overall cycle efficiency can be increased by 2 per cent points and the specific work can be increased by 7.3 per cent. Copyright © 2000 John Wiley & Sons, Ltd.     

HAT循环饱和器工质(火用)计算分析及(火用)效率

饱和器是HAT循环中的关键部件,对其性能的认识关系到整个系统的性能分析。运用的方法,计算了饱和器工质湿空气和水的值,分析了不同参考点的温度和湿度对值的影响规律,以及物理和化学扩散随湿空气温度的变化情况。通过建立饱和器平衡模型,采用了目的效率作为饱和器效率。计算结果表明：湿空气值随参考点的温度和湿度变化规律为：先减小,直到最低点为零,然后不断增加,值始终大于(等于)零,并且与参考点参数差距越大,值越大。当湿空气温度增加,物理所占比重减少,而化学扩散的比重增加,在到达一定温度后,化学大于物理。     

A novel EFHAT system and exergy analysis with energy utilization diagram

In this paper, a new type of gas turbine cycle has been proposed based on an innovative combination of a newly designed HAT cycle with an externally fired heater. In this manner, “dirty” fuels such as coal and biomass can be more efficiently used than before and the water in this cycle can be recycled. This is radically different from the conventional HAT cycle. In particular, the temperature of the clean humid air out of the turbine is not restricted by the dew point of gas. Hence, some amount of latent heat can be utilized to generate hot water being supplied to the humidifier. This will enhance the humidification ability for improving performance of the system. The new system is also analyzed by using the graphical exergy methodology based on energy-utilization diagrams (EUDs). As a result, for a turbine inlet temperature (TIT) of 1073 K, the thermal efficiency of the new system may be as high as 45.37%. The new system will effectively recover both the energy quality and quantity at the low- and middle-temperature ranges.     

Performance analysis of humid air turbine cycle with solar energy for methanol decomposition

According to the physical and chemical energy cascade utilization and concept of synthesis integration of variety cycle systems, a new humid air turbine (HAT) cycle with solar energy for methanol decomposition has been proposed in this paper. The solar energy is utilized for methanol decomposing as a heat source in the HAT cycle. The low energy level of solar energy is supposed to convert the high energy level of chemical energy through methanol absorption, realizing the combination of clean energy and normal chemical fuels as compared to the normal chemical recuperative cycle. As a result, the performance of normal chemical fuel thermal cycle can be improved to some extent. Though the energy level of decomposed syngas from methanol is decreased, the cascade utilization of methanol is upgraded. The energy level and exergy losses in the system are graphically displayed with the energy utilization diagrams (EUD). The results show that the cycle’s exergy efficiency is higher than that of the conventional HAT cycle by at least 5 percentage points under the same operating conditions. In addition, the cycle’s thermal efficiency, exergy efficiency and solar thermal efficiency respond to an optimal methanol conversion.     

Thermodynamic performance assessment of an indirect intercooled reheat regenerative gas turbine cycle with inlet air cooling and evaporative aftercooling of the compressor discharge

This study provides a computational analysis to investigate the effects of cycle pressure ratio, turbine inlet temperature (TIT), and ambient relative humidity (φ) on the thermodynamic performance of an indirect intercooled reheat regenerative gas turbine cycle with indirect evaporative cooling of the inlet air and evaporative aftercooling of the compressor discharge. Combined first and second‐law analysis indicates that the exergy destruction in various components of gas turbine cycles is significantly affected by compressor pressure ratio and turbine inlet temperature, and is not at all affected by ambient relative humidity. It also indicates that the maximum exergy is destroyed in the combustion chamber; which represents over 60% of the total exergy destruction in the overall system. The net work output, first‐law efficiency, and the second‐law efficiency of the cycle significantly varies with the change in the pressure ratio, turbine inlet temperature and ambient relative humidity. Results clearly shows that performance evaluation based on first‐law analysis alone is not adequate, and hence more meaningful evaluation must include second‐law analysis. Decision makers should find the methodology contained in this paper useful in the comparison and selection of gas turbine systems. Copyright © 2006 John Wiley & Sons, Ltd.     

Experimental investigation of pressurized packing saturator for humid air turbine cycle

Humid air turbine (HAT) cycle is an advanced power generation system, and its efficiency and output power are improved by humidifying the compressed air. This humidification process is completed in the saturator. Therefore, the humidifying performance of saturator has great influence on the performance of HAT cycle. In this work, a new type packing saturator was designed and a series of experiments were carried out to study its humidifying performance. In order to improve the uniformity of the saturator inlet, a twin-tangential annular flow gas distributor was designed. Then it was authorized by China invention patents (ZL201010200778.9). Now, the mal-distribution factor of inlet air is mainly between 0.15 and 0.35 in all experimental conditions. Some key parameters of air and water at the inlet and outlet of saturator were measured at different experimental conditions. These results show the outlet humid air temperature is an important parameter for determining the humidifying amount of the saturator. The humidifying performance of the saturator is mainly affected by the inlet water temperature and the liquid/gas (L/G) ratio. At the same operating pressure, the humidity ratio of outlet humid air increases with inlet water temperature and L/G ratio. At higher inlet water temperature, the L/G ratio has a greater effect on the humidity ratio of outlet humid air. The outlet water temperature is mainly affected by the inlet gas temperature. With the increasing of inlet air temperature, the outlet water temperature increases, and it is close to the wet-bulb temperature of inlet air.     

带压缩空气储能的冷热电联产系统的

对一种带压缩空气储能的冷热电联产系统进行了热力学(火用)分析,得到了各主要部件和整个系统的(火用)损失及(火用)效率的变化规律.分析结果表明空气透平绝热效率的提高对系统(火用)效率的贡献大于压缩机效率同样提高的功效;在其它参数确定时,存在最佳压比,可使系统的(火用)效率在该条件下达极值;高温换热器是新型冷热电联产系统中产生(火用)损失的主要部件,而循环水量的大小是影响高温换热器(火用)效率的主要因素.     

Performance investigation in modified and improved augmented power generation Kalina cycle using Python

In the generation of electricity and cogeneration, Kalina cycle is considered as one of the competitors to organic Rankine cycle. With the simplicity and identical components of the binary mixture, Kalina system makes it more prominent to get developed and implemented as well with its environmental friendly associate. This work proposes a new improved Kalina cycle system to convert the natural source from sun to useful work. The proposed system utilizes heat source suitable to medium temperature heat applications. The proposed cycle have 2 units of solar collector, favoring an additional heat recovery and higher performance. Solar hot source temperature and pressure are 190°C and 45 bar with additional flow to the turbine of 1.15 kg/s. Energy and second law analysis have considered in evaluating the performance of the proposed plant. The energy analysis shows minimum value of net power, energy efficiency and plant efficiency as 241 kW, 15.5% and 5.7. The exergy analysis defines that, to the proposed cycle, the exergy efficiency initializes at 77% with more exergy destruction at turbine with 31%. With the parametric analysis, the system is amended to have the maximum values of energy and exergy performances as 18.5%, 7.1% and 85%. The parametric study identifies the optimum value of the inlet temperature and pressure of the pump and turbine.     

An experimental study on the heat recovery from the exhaust air of stenters with a packed bed column

Stenters are the dryers that are commonly used in textile finishing mills. The exhaust air of the stenters is of great potential of energy saving via heat recovery mainly using the latent heat of condensation of the water vapour involved. This study reveals the usage possibility of a packed bed column for the heat recovery from the exhaust air of the stenter. An experimental investigation was carried out with a laboratory‐scale counter flow packed bed column. Additionally, an exergetic evaluation of the system was performed. Water inlet temperature and relative humidity ratio of the exhaust air are the main factors that affect the water outlet temperatures and efficiency of the system. It was observed that a decrease in the water inlet temperature increases the recovered exergy; however, water outlet temperature is not significantly affected by the inlet temperature of the water. The exergy efficiency of the system increases with the increase in the relative humidity ratio of the exhaust air. Copyright © 2007 John Wiley & Sons, Ltd.     

Thermodynamic analysis of an LNG fuelled combined cycle power plant with waste heat recovery and utilization system

This paper has proposed an improved liquefied natural gas (LNG) fuelled combined cycle power plant with a waste heat recovery and utilization system. The proposed combined cycle, which provides power outputs and thermal energy, consists of the gas/steam combined cycle, the subsystem utilizing the latent heat of spent steam from the steam turbine to vaporize LNG, the subsystem that recovers both the sensible heat and the latent heat of water vapour in the exhaust gas from the heat recovery steam generator (HRSG) by installing a condensing heat exchanger, and the HRSG waste heat utilization subsystem. The conventional combined cycle and the proposed combined cycle are modelled, considering mass, energy and exergy balances for every component and both energy and exergy analyses are conducted. Parametric analyses are performed for the proposed combined cycle to evaluate the effects of several factors, such as the gas turbine inlet temperature (TIT), the condenser pressure, the pinch point temperature difference of the condensing heat exchanger and the fuel gas heating temperature on the performance of the proposed combined cycle through simulation calculations. The results show that the net electrical efficiency and the exergy efficiency of the proposed combined cycle can be increased by 1.6 and 2.84% than those of the conventional combined cycle, respectively. The heat recovery per kg of flue gas is equal to 86.27 kJ s^?1. One MW of electric power for operating sea water pumps can be saved. The net electrical efficiency and the heat recovery ratio increase as the condenser pressure decreases. The higher heat recovery from the HRSG exit flue gas is achieved at higher gas TIT and at lower pinch point temperature of the condensing heat exchanger. Copyright © 2006 John Wiley & Sons, Ltd.     

Thermodynamic analysis of an integrated power generation system driven by solid oxide fuel cell

A new integrated power generation system driven by the solid oxide fuel cell (SOFC) is proposed to improve the conversion efficiency of conventional energy by using a Kalina cycle to recover the waste heat of exhaust from the SOFC-GT. The system using methane as main fuel consists an internal reforming SOFC, an after-burner, a gas turbine, preheaters, compressors and a Kalina cycle. The proposed system is simulated based on the developed mathematical models, and the overall system performance has been evaluated by the first and second law of thermodynamics. Exergy analysis is conducted to indicate the thermodynamic losses in each components. A parametric analysis is also carried out to examine the effects of some key thermodynamic parameters on the system performance. Results indicate that as compressor pressure ratio increases, SOFC electrical efficiency increases and there is an optimal compressor pressure ratio to reach the maximum overall electrical efficiency and exergy efficiency. It is also found that SOFC electrical efficiency, overall electrical efficiency and exergy efficiency can be improved by increasing air flow rate. Also, the largest exergy destruction occurs in the SOFC followed by the after-burner, the waste heat boiler, the gas turbine. The compressor pressure ratio and air flow rate have significant effects on the exergy destruction in some main components of system.     

Two new high-performance cycles for gas turbine with air bottoming

The objective of this research is to model steam injection in the gas turbine with Air Bottoming Cycle (ABC). Based on an exergy analysis, a computer program has been developed to investigate improving the performance of an ABC cycle by calculating the irreversibility in the corresponding devices of the system. In this study, we suggest two new cycles where an air bottoming cycle along with the steam injection are used. These cycles are: the Evaporating Gas turbine with Air Bottoming Cycle (EGT-ABC), and Steam Injection Gas turbine with Air Bottoming Cycle (STIG-ABC). The results of the model show that in these cycles, more energy recovery and higher air inlet mass flow rate translate into an increase of the efficiency and output turbine work. The EGT-ABC was found to have a lower irreversibility and higher output work when compared to the STIG-ABC. This is due to the fact that more heat recovery in the regenerator in the EGT-ABC cycle results in a lower exhaust temperature. The extensive modeling performed in this study reveals that, at the same up-cycle pressure ratio and turbine inlet temperature (TIT), a higher overall efficiency can be achieved for the EGT-ABC cycle.     

Thermo-environmental analysis of an open cycle gas turbine power plant with regression modeling and optimization

In this paper, a gas turbine cycle is modeled to investigate the effects of important operating parameters like compressor inlet temperature (CIT), turbine inlet temperature (TIT) and pressure ratio (PR) on the overall cycle performance and CO₂ emissions. Such effects are also investigated on the exergy destruction and exergy efficiency of the cycle components. Furthermore, multiple polynomial regression models are developed to correlate the response variables (performance characteristics) and predictor variables (operating parameters). The operating parameters are then optimized. According to the results, operating parameters have a significant effect on the cycle performance and CO₂ emissions. The largest exergy destruction is found in the combustion chamber with lowest exergy efficiency. The regression models have appeared to be a good estimator of the response variables. The optimal operating parameters for maximum performance have been determined as 288 K for CIT, 1600 K for TIT and 23.2 for PR.     

Effects of evaporative inlet and aftercooling on the recuperated gas turbine cycle

Inlet air cooling and cooling of the compressor discharge using water injection boost both efficiency and power of gas turbine cycles. Four different layouts of the recuperated gas turbine cycle are presented. Those layouts include the effect of evaporative inlet and aftercooling (evaporative cooling of the compressor discharge). A parametric study of the effect of turbine inlet temperature (TIT), ambient temperature, and relative humidity on the performance of all four layouts is investigated. The results indicate that as TIT increases the optimum pressure ratio increases by 0.45 per 100 K for the regular recuperated cycle and by 1.4 per 100 K for the recuperated cycle with evaporative aftercooling. The cycles with evaporative aftercooling have distinctive pattern of performance curves and higher values of optimum pressure ratios. The results also showed that evaporative cooling of the inlet air could boost the efficiency by up to 3.2% and that evaporative aftercooling could increase the power by up to about 110% and cycle efficiency by up to 16%.     

航改燃气轮机的湿空气透平循环改型方案研究

航改燃气轮机具有压比高、效率高、可靠性高和结构紧凑等特点,它将航空发动机先进技术有效地应用于工业领域。以某型三轴航改燃气轮机为研究对象,对其不同的HAT循环改型方案进行了研究。建立了一种基于饱和曲线和工作线的饱和器模型,该模型避免使用难以准确获得的传热传质系数,利用饱和器实验数据对该模型进行了验证,结果表明:建立的饱和器模型具有较高的准确性,其中出口空气温度最大误差小于0.8%,出口湿度最大误差小于1.9%。此外,设计并仿真了3种不同结构形式的HAT循环方案,仿真结果表明:原始的压气机和透平特性不适合于改型后的HAT循环,它限制了HAT循环的效率和燃气轮机的输出功率(简称出功)。针对这一问题,提出了改进透平特性方案,该方案有效地解决了水蒸气的加入带来部件不匹配问题。在此基础上分析了3个HAT方案设计点的性能,结果表明方案2即在简单循环基础上加入了饱和器、经济器、回热器和中冷器是最佳的改型方案。     

Energy and exergy analyses of a CFB‐based indirectly fired combined cycle power generation system

Combined cycle configuration has the ability to use the waste heat from the gas turbine exhaust gas using the heat recovery steam generator for the bottoming steam cycle. In the current study, a natural gas‐fired combined cycle with indirectly fired heating for additional work output is investigated for configurations with and without reheat combustor (RHC) in the gas turbine. The mass flow rate of coal for the indirect‐firing mode in circulating fluidized bed (CFB) combustor is estimated based on fixed natural gas input for the gas turbine combustion chamber (GTCC). The effects of pressure ratio, gas turbine inlet temperature, inlet temperatures to the air compressor and to the GTCC on the overall cycle performance of the combined cycle configuration are analysed. The combined cycle efficiency increases with pressure ratio up to the optimum value. Both efficiency and net work output for the combined cycle increase with gas turbine inlet temperature. The efficiency decreases with increase in the air compressor inlet temperature. The indirect firing of coal shows reduced use with increase in the turbine inlet temperature due to increase in the use of natural gas. There is little variation in the efficiency with increase in GTCC inlet temperature resulting in increased use of coal. The combined cycle having the two‐stage gas turbine with RHC has significantly higher efficiency and net work output compared with the cycle without RHC. The exergetic efficiency also increases with increase in the gas turbine inlet temperature. The exergy destruction is highest for the CFB combustor followed by the GTCC. The analyses show that the indirectly fired mode of the combined cycle offers better performance and opportunities for additional net work output by using solid fuels (coal in this case). Copyright © 2009 John Wiley & Sons, Ltd.     

Energetic and exergetic performance analyses of a combined heat and power plant with absorption inlet cooling and evaporative aftercooling

In this paper, exergy method is applied to analyze the gas turbine cycle cogeneration with inlet air cooling and evaporative aftercooling of the compressor discharge. The exergy destruction rate in each component of cogeneration is evaluated in detail. The effects of some main parameters on the exergy destruction and exergy efficiency of the cycle are investigated. The most significant exergy destruction rates in the cycle are in combustion chamber, heat recovery steam generator and regenerative heat exchanger. The overall pressure ratio and turbine inlet temperature have significant effect on exergy destruction in most of the components of cogeneration. The results obtained from the analysis show that inlet air cooling along with evaporative aftercooling has an obvious increase in the energy and exergy efficiency compared to the basic gas turbine cycle cogeneration. It is further shown that the first-law efficiency, power to heat ratio and exergy efficiency of the cogeneration cycle significantly vary with the change in overall pressure ratio and turbine inlet temperature but the change in process heat pressure shows small variation in these parameters.     

Exergy analysis of a coal‐based 210 MW thermal power plant

In the present work, exergy analysis of a coal‐based thermal power plant is done using the design data from a 210 MW thermal power plant under operation in India. The entire plant cycle is split up into three zones for the analysis: (1) only the turbo‐generator with its inlets and outlets, (2) turbo‐generator, condenser, feed pumps and the regenerative heaters, (3) the entire cycle with boiler, turbo‐generator, condenser, feed pumps, regenerative heaters and the plant auxiliaries. It helps to find out the contributions of different parts of the plant towards exergy destruction. The exergy efficiency is calculated using the operating data from the plant at different conditions, viz. at different loads, different condenser pressures, with and without regenerative heaters and with different settings of the turbine governing. The load variation is studied with the data at 100, 75, 60 and 40% of full load. Effects of two different condenser pressures, i.e. 76 and 89 mmHg (abs.), are studied. Effect of regeneration on exergy efficiency is studied by successively removing the high pressure regenerative heaters out of operation. The turbine governing system has been kept at constant pressure and sliding pressure modes to study their effects. It is observed that the major source of irreversibility in the power cycle is the boiler, which contributes to an exergy destruction of the order of 60%. Part load operation increases the irreversibilities in the cycle and the effect is more pronounced with the reduction of the load. Increase in the condenser back pressure decreases the exergy efficiency. Successive withdrawal of the high pressure heaters show a gradual increment in the exergy efficiency for the control volume excluding the boiler, while a decrease in exergy efficiency when the whole plant including the boiler is considered. Keeping the main steam pressure before the turbine control valves in sliding mode improves the exergy efficiencies in case of part load operation. Copyright © 2006 John Wiley & Sons, Ltd.     

Performance analysis of a waste‐heat‐powered thermodynamic cycle for multieffect refrigeration

A multieffect refrigeration system that is based on a waste‐heat‐driven organic Rankine cycle that could produce refrigeration output of different magnitudes at different levels of temperature is presented. The proposed system is integration of combined ejector–absorption refrigeration cycle and ejector expansion Joule–Thomson (EJT) cooling cycle that can meet the requirements of air‐conditioning, refrigeration, and cryogenic cooling simultaneously at the expense of industrial waste heat. The variation of the parameters that affect the system performance such as industrial waste heat temperature, refrigerant turbine inlet pressure, and the evaporator temperature of ejector refrigeration cycle (ERC) and EJT cycles was examined, respectively. It was found that refrigeration output and thermal efficiency of the multieffect cycle decrease considerably with the increase in industrial waste heat temperature, while its exergy efficiency varies marginally. A thermal efficiency value of 22.5% and exergy efficiency value of 8.6% were obtained at an industrial waste heat temperature of 210°C, a turbine inlet pressure of 1.3 MPa, and ejector evaporator temperature of 268 K. Both refrigeration output and thermal efficiency increase with the increase in turbine inlet pressure and ERC evaporator temperature. Change in EJT cycle evaporator temperature shows a little impact on both thermal and exergy efficiency values of the multieffect cycle. Analysis of the results clearly shows that the proposed cycle has an effective potential for cooling production through exploitation of lost energy from the industry. Copyright © 2014 John Wiley & Sons, Ltd.     

Performance analysis of combined cycle power plant

Combined cycle power plants (CCPPs) are in operation with diverse thermodynamic cycle configurations. Assortment of thermodynamic cycle for scrupulous locality is dependent on the type of fuel available and different utilities obtained from the plant. In the present paper, seven of the practically applicable configurations of CCPP are taken into consideration. Exergetic and energetic analysis of each component of the seven configurations is conducted with the help of computer programming tool, i.e., engineering equation solver (EES) at different pressure ratios. For Case 7, the effects of pressure ratio, turbine inlet temperature and ambient relative humidity on the first and second law is studied. The thermodynamics analysis indicates that the exergy destruction in various components of the combined cycle is significantly affected by the overall pressure ratio, turbine inlet temperature and pressure loss in air filter and less affected by the ambient relative humidity.