Investigation of an ammonia-water combined power and cooling system driven by the jacket water and exhaust gas heat of an internal combustion engine

An ammonia-water combined power and cooling system is proposed and investigated in this work, in which the waste heat contained in the jacket water and exhaust gas of an internal combustion engine can be recovered efficiently to generate power and cooling energy simultaneously. The proposed system was simulated, and its thermodynamic performance in the base case was calculated based on waste heat data from an actual gas engine with a rated power output of 300 kW. The equivalent heat-to-power efficiency of the combined system is 19.76%, and the total equivalent power output is as high as 92.86 kW. The exergy efficiency of the combined system reaches 33.69%. The effects of the turbine inlet pressure, generation pressure in the reboiler, exhaust gas temperature and cooling water temperature were studied to provide guidance for the system design. The results of an economic analysis indicate that the proposed system has good economic benefit.     

A theoretical study on a novel combined power and ejector refrigeration cycle

A new combined power and refrigeration cycle is proposed for the cogeneration, which combines the Rankine cycle and the ejector refrigeration cycle by adding an extraction turbine between heat recovery vapor generator (HRVG) and ejector. This combined cycle could produce both power output and refrigeration output simultaneously, and could be driven by the flue gas from gas turbine or engine, solar energy, geothermal energy and industrial waste heats. Parametric analysis and exergy analysis are conducted to examine the effects of thermodynamic parameters on the performance and exergy destruction in each component for the combined cycle. The results show that the condenser temperature, the evaporator temperature, the turbine inlet pressure, the turbine extraction pressure and extraction ratio have significant effects on the turbine power output, refrigeration output, exergy efficiency and exergy destruction in each component in the combined cycle. It is also shown that the biggest exergy destruction occurs in the heat recovery vapor generator, followed by the ejector and turbine.     

Optimum pressure ratios for different gas turbine cycles

It is important to know the optimum pressure ratios for maximum power and efficiency of gas turbine engines. Their use would improve performance and reduce component design complexities and cost and help to select the appropriate cycle combination to meet the requirements of a specific application of the gas turbine engine,

In this work optimum pressure ratios for maximum power r wand efficiency r’l were derived for eight alternative gas turbine cycles involving intercooling, heat exchange and reheat. The independent variables were maximum cycle temperature ratio t, compressor efficiency 11e, and turbine efficiency 11t. Due to the non-linear nature of the r’l equations, a numerical technique was used for the solution.

Results show that r_w is more sensitive to changes in the operating parameters than r’l’ especially in cycles which involve heat exchange. The final decision may be a thermo-economic optimum pressure ratio for the selected cycle, which is likely to be between r_w and r’l’     

冷热水联供机组性能实验研究

建立了燃气内燃机驱动的冷热水联供系统,测量了空调名义工况条件下机组的制冷和供热性能,并实验研究了内燃机的转速对机组制冷和供热的影响特性。实验结果表明系统在空调名义工况条件下的制冷量467．1kW,供热量为148．7kW,一次能源利用率达1．9,与常规电制冷＋锅炉供热相比能源节约率达37．8％。在实验测试的内燃机转速范围内制冷系统的制冷量和余热回收供热量随内燃机转速的降低而降低,但制冷系统和冷热水联供系统能源利用率均随内燃机转速的降低而升高,表明机组在部分负荷运行时,应优先调节内燃机的转速,从而确保系统具有较高的能源利用率。该联供系统有效回收利用了内燃机的余热,提高了能源利用率,商业化前景较好。     

结合燃气-蒸汽联合循环的液化天然气冷能发电利用

提出了结合燃气-蒸汽联合循环的利用液化天然气（liquefied natural gas,LNG）冷能的朗肯循环发电系统,实现LNG冷能梯级利用。朗肯循环蒸发器和燃气-蒸汽联合循环凝汽器换热量匹配一致,循环水系统实现闭式且不受环境温度影响。对系统进行模拟并分析了影响系统的主要参数,结果显示：随着朗肯循环冷凝温度的降低,朗肯循环净输出功率和净效率均有提升;随着循环水温度的提高,朗肯循环的净输出功率和净效率都将提高,而蒸汽轮机输出功率减少,但二者总的输出功率降低幅度不大。     

一种新型跨临界CO2冷电联供系统热力分析

提出一种新型跨临界二氧化碳（trans-critical carbon dioxide,TCO₂）再压缩循环和喷射器制冷循环耦合的冷电联供系统。该系统在输出电能的同时,利用低品位热能驱动喷射器工作输出冷量。以输出电量1 MW为设计目标,对比冷电联供系统和再压缩发电系统的性能,研究联供系统各部件（火用）损和主要热力参数对其性能的影响。结果表明：联供系统利用CO₂余热驱动喷射器输出冷量,循环热效率高于单一再压缩系统;加热器（火用）损所占比例最大,回热器次之;透平进口温度、压力和背压对联供系统工质流量、循环效率、输出功率、加热器功率、压缩机耗功及喷射器制冷量等参数影响较大;而冷凝温度和蒸发温度仅对制冷循环制冷量影响较大。在设定条件下,联供系统的循环热效率和（火用）效率可分别达到46.99%和47.21%。     

Cyclic operation of aero gas turbines – materials and component life implications

Abstract

Historically, the issues connected with the lifing of power generation gas turbine components have been very different from those associated with aero engines. Specifically, component lives in the power generation application have been dictated by creep and high cycle fatigue, whereas low cycle fatigue has been the driver for aero engines. However, developments in the design and usage of gas turbines within the respective industries have resulted in this distinction becoming increasingly blurred. This paper highlights recent advances in the materials technology, stress analysis and lifing of aero engine components, which are potentially relevant to industrial gas turbines. In particular, the development of complex constitutive equations for modelling plasticity and anisotropic creep are discussed, with particular reference to the behaviour of single crystal turbine blades. Moreover, developments in the methodologies used to estimate safe service lives for the components are considered. Specifically, a new lifing procedure, capable of accurately predicting component lives from plain specimen data alone, is discussed.     

Thermal and exergoeconomic analysis of a novel solar driven combined power and ejector refrigeration (CPER) system

In the present study, a novel solar driven combined power and ejector refrigeration system (CPER) of 50 kW power capacity composed of an ORC (organic Rankine cycle) and an ejector refrigeration system is investigated. Solar driven CPER system is composed of two main cycles: collector cycle and refrigeration cycle. The collector cycle is made of a U-tube ETC and circulation pump and the ejector refrigeration cycle consists of generator, turbine, ejector, heat exchanger, condenser, evaporator, expansion valve, and pump. Thermodynamic performance of the proposed CPER system is evaluated and a thermo-economic analysis is conducted using the SPECO (specific exergy costing) method. A parametric study showed the effects of condenser temperature, evaporator temperature, generator pressure, turbine back pressure and turbine extraction ratio. The genetic algorithm optimization analysis is conducted which shows 25.5% improvement in thermal energy, 21.27% in exergy efficiency, and 7.76% reduction in the total cost of the CPER system. The results reveal that the performance of the CPER system is considerably improved at higher temperatures of generator and evaporator.     

Hybrid vapor compression refrigeration system with an integrated ejector cooling cycle

A refrigeration system was developed which combines a basic vapor compression refrigeration cycle with an ejector cooling cycle. The ejector cooling cycle is driven by the waste heat from the condenser in the vapor compression refrigeration cycle. The additional cooling capacity from the ejector cycle is directly input into the evaporator of the vapor compression refrigeration cycle. The governing equations are derived based on energy and mass conservation in each component including the compressor, ejector, generator, booster and heat exchangers. The system performance is first analyzed for the on-design conditions. The results show that the COP is improved by 9.1% for R22 system. The system is then compared with a basic refrigeration system for variations of five important variables. The system analysis shows that this refrigeration system can effectively improve the COP by the ejector cycle with the refrigerant which has high compressor discharge temperature.     

Control optimisation of CO2 cycles for medium temperature retail food refrigeration systems

This paper describes a detailed procedure into the investigation of optimised control strategies for CO₂ cycles in medium temperature retail food refrigeration systems. To achieve this objective, an integrated model was developed composing of a detailed condenser/gas cooler model, a simplified compressor model, an isenthalpic expansion process and constant evaporating temperature and superheating. The CO₂ system can operate subcritically or transcritically depending on the ambient temperature. For a transcritical operation, a prediction can be made for optimised refrigerant discharge pressures from thermodynamic cycle calculations. When the system operates in the subcritical cycle, a floating discharge pressure control strategy is employed and the effect of different transitional ambient temperatures separating subcritical and transcritical cycles on system performance is investigated. The control strategy assumes variable compressor speed and adjustable air flow for the gas cooler/condenser to be modulated to achieve the constant cooling load requirement at different ambient conditions.     

渔船用吸附式制冰系统的模拟仿真以及试验

采用船用6160A型柴油机为热源,设计了一台发动机余热驱动的用于渔船上鱼类保鲜的吸附式剖冰系统。该系统中的吸附工质采用了块状活性炭,对系统的模拟仿真以及试验结果表明,回热回质可以显著的提高系统的性能。在具有回热回质的条件下,当系统的循环时间为50min时,所得到的制冷量为1．93kW。     

R290冷凝器的设计与制造

针对R290的性能特点和管内两相流的冷凝换热特性，设计并制造了R290／CO2复叠式制冷循环中的R290水冷式冷凝器，为自然工质R290／CO2复叠式制冷循环系统的研究和实际应用奠定基础。     

Theoretical study and design of a low-grade heat-driven pilot ejector refrigeration machine operating with butane and isobutane and intended for cooling of gas transported in a gas-main pipeline

This paper describes the construction and performance of a novel combined system intended for natural gas transportation and power production, and for cooling of gas transported in a gas-main pipeline. The proposed system includes a gas turbine compressor, a combined electrogenerating plant and an ejector refrigeration unit operating with a hydrocarbon refrigerant. The combined electrogenerating plant consists of a high-temperature steam–power cycle and a low-temperature hydrocarbon vapor power cycle, which together comprise a binary vapor system. The combined system is designed for the highest possible effectiveness of power generation and could find wide application in gas-transmission systems of gas-main pipelines. Application of the proposed system would enable year-round power generation and provide cooling of natural gas during periods of high ambient temperature operation. This paper presents the main results of a theoretical study and design performance specifications of a low-grade heat-driven pilot ejector refrigeration machine operating with butane and isobutane.     

Thermodynamic modelling and optimization of a dual pressure reheat combined power cycle

Heat recovery steam generator (HRSG) plays a key role on performance of combined cycle (CC). In this work, attention was focused on a dual pressure reheat (DPRH) HRSG to maximize the heat recovery and hence performance of CC. Deaerator, an essential open feed water heater in steam bottoming cycle was located to enhance the efficiency and remove the dissolved gasses in feedwater. Each of the heating section in HRSG is solved from the local flue gas condition with an aim of getting minimum possible temperature difference. For high performance, better conditions for compressor, HRSG sections, steam reheater and deaerator are developed. The CC system is optimized at a gas turbine inlet temperature of 1400°C due to the present available technology of modern gas turbine blade cooling systems. The exergetic losses in CC system are compared with each other. The present DPRH HRSG model has been compared and validated with the plant and published data.     

Exhaust gas energy recovery system of pneumatic driving automotive engine

Almost the same quantity to net output work of energy has been carried out and wasted by exhaust gas in typical automotive engine. Recovering the energy from exhaust gas and converting to mechanical energy will dramatically increase the heat efficiency and decrease the fuel consumption. With the increasing demand of fuel conservation, exhaust gas energy recovery technologies have been a hot topic. At present, many researches have been focused on heating or cooling the cab, mechanical energy using, and thermo-electronic converting. Unfortunately, the complicated transmission of mechanical energy using and the depressed efficiency of thermo-electronic converting restrict their widely applying. In this paper, a kind of pneumatic driving automotive engine exhaust gas energy recovery system, in which highly compressed air acts as energy storing and converting carrier, has been established. Pneumatic driving motor can produce moderate speed and high torque output, which is compatible for engine using. The feasibility has been certificated by GT-Power simulation and laboratory testes. The technologies about increasing recovery efficiency have been discussed in detail. The results demonstrated that the in parallel exhaust gas energy recovery system, which is similar to the compound turbo-charger structure can recovery 8 to 10 percent of rated power output. At last, a comprehensive system, which includes Rankine cycle based power wheel cycle unit etc, has been introduced.     

蒸发冷却式热管与蒸气压缩复合数据中心空调系统性能实验研究

为解决传统数据中心空调系统能耗高和冷却效率低等问题,本文提出了带有蒸发式冷凝器的制冷剂泵驱动热管与蒸气压缩复合数据中心空调系统,实验分析了不同室外温度与冷凝器风速下系统的运行性能.结果表明:在热管模式下,当室外温度低于0℃时,降低冷凝器风速能够提升系统COP;当室外温度高于0℃时,增大室外机风速能够提高系统节能性.降低...     

液化天然气(LNG)冷能用于斯特林发动机和燃气轮机的联合系统研究

利用LNG冷能具有较好的节能潜力和经济效益,通过流程的创新设计,提出了一种将LNG冷能用于燃气轮机和斯特林发动机的联合系统。基于热力学第一、第二定律,对联合系统进行热力学分析,结果表明:在环境温度35℃条件下,联合系统的输出功率为5715.48kW,热效率为31.62%,效率为43.65%;相比燃气轮机系统和直接冷却进气系统,联合系统的输出功率分别提高了7.84%和0.78%,热效率分别提高了3.16%和1.18%,效率分别提高了4.23%和1.63%。联合系统在不同环境温度下,可将燃气轮机的进气温度降低10℃左右,系统的输出功率和效率随着进气温度的降低均有所提高。     

Experimental study on automotive cooling and heating air conditioning system using CO2 as a refrigerant

Recently, as one of the countermeasures against the global warming and energy conservation problems, natural refrigerants such as CO₂ are now paid attention as substitutes for HFCs in automotive air conditioning systems. Also, in recent years because the heat release from the eco-car's engine decreases, there is a problem that the present automotive heating air conditioning system cannot provide sufficient heating capacity.

As an alternative approach, we focused on a solution utilizing a CO₂-based heat pump, whereby the waste heat from the heat pump cycle during dehumidification of the incoming air (referred to as the dehumidifying condition) is recovered and used as an auxiliary heat source instead of an electric heater. Based on this concept, we aimed to develop an effective automotive cooling and heating air conditioning system using CO₂ as a refrigerant.

As the result, a prototype CO₂ automotive cooling and heating air conditioning system for medium-sized cars was successfully developed. With this system, performance superior to that of the present HFC134a system can be achieved.     

Potential energy benefits of integrated refrigeration system with microturbine and absorption chiller

This paper presents and analyzes the performance potential of a refrigeration system that is integrated with a microturbine and an absorption chiller (RMA). The waste heat from the microturbine operates the absorption chiller, which provides additional cooling. This additional cooling capacity can be utilized either to subcool the liquid exiting the condenser of the refrigeration system or to precool the air entering the condenser in the refrigeration system. Moreover, any surplus cooling capacity not utilized in the subcooler can be utilized to precool the microturbine intake air. The additional assistance to the refrigeration system enhances the efficiency of the refrigeration cycle, which in turn reduces the required microturbine size. The smaller size of the microturbine enhances the part load efficiency, especially in lower ambient temperatures. With increased microturbine efficiency, RMA with subcooler, RMA with subcooler and microturbine intake air precooler, and RMA with condenser air precooler can reduce the annual energy consumption by 12, 19, and 3%, respectively, as compared to a refrigeration system operating without any waste heat utilization from the microturbine. Therefore, RMA with subcooler and microturbine intake air precooler has the best potential of energy savings. The payback period of RMA with subcooler and microturbine intake air precooler is estimated in 3 years, which facilitates it as an economically feasible solution among the options investigated.     

Thermodynamic optimization of combined power and refrigeration cycle using binary organic working fluid

A combined cycle has been proposed for the production of power and refrigeration simultaneously. The cycle can be driven by low grade heat sources such as solar, geothermal and waste heat sources. In the first part of this paper, a model has been developed to perform a parametric analysis to evaluate the effects of important parameters on the performance of the cycle, which is a combination of Rankine and absorption refrigeration cycle. Propane–decane has been used as an organic dual working fluid. In the second part, multi objective genetic algorithm is applied for Pareto approach optimization of the cycle. There are three important conflicting objectives namely, turbine work (W_t), cooling capacity (Q_c) and thermal efficiency (η_th) which have been selected to find the best possible combination of these performance parameters. Optimization has been carried out by varying turbine inlet pressure, superheated temperature and condenser temperature as design variables. Among optimum design parameters, a trade-off point is selected. Turbine inlet pressure, superheated temperature and condenser temperature are assumed to be 29.5 bar, 410 K and 386.6 K respectively as the values assigned to this point. Furthermore, it has been shown that some interesting and important relationships can be discovered among optimal objective functions and decision variables involved, consequently.