海水源热泵系统的(火用)经济分析

利用(火用)经济分析方法建立了海水源热泵系统的(火用)经济分析模型,并对海水源热泵系统流程的(火用)成本进行计算,结果表明热泵机房的(火用)流成本最高,因此可以通过提高热泵效率等途径来减小(火用)流成本.建议以(火用)流成本最小作为约束函数,并将(火用)经济分析法用于海水源热泵系统的优化设计中.     

折合(火用)成本在空调冷热源优化决策中的应用

考虑了冷热源在不同运行工况时能源"质"的利用情况及制冷工况和制热工况的综合系数,提出了折合(火用)成本的概念,并分别采用折合冷量(火用)成本和折合热量(火用)成本作为评价指标,对3种方案进行分析比较,得到了相同的结果.研究表明,将折合(火用)成本作为评价冷热源系统方案优劣的指标,是较为科学合理的.     

蒸发冷却与机械制冷复合空调机组分析

对蒸发冷却与机械制冷复合空调机组进行了(火用)分析,并根据实测数据计算出了机组各功能段进出口(火用)的大小,并通过(火用)效率和(火用)效比分析得出了复合空调机组能量利用效率低的薄弱环节,提出了节能改进方法.     

热经济学用成分分析法在实际中的应用

本文以某轻化工厂的实际工程为背景,在分析了原热、电、冷分产系统的基础上,提出了几种合产系统方案,并分别对其做了(火用)效率计算,最后以热经济学的产品(火用)成本为目标函数进行方案筛选,得到了合理的合产系统。     

空调系统中热湿处理过程的(火用)评价方法及应用

提出对热、湿处理过程进行单独(火用)评价的概念,并构建了相应评价指标.以某一次回风空调系统的典型夏季空气处理过程为例,在热力学极限意义上阐明了对热、湿处理进行单独(火用)评价的实施过程,计算结果表明该空气处理过程的显热(火用)效明显高于潜热(火用)效,潜热(火用)效低下的原因主要在于再热显热(火用)损和冷凝水(火用)损...     

砖瓦轮窑的分析

本文将(火用)(有效能)应用于轮窑的能量平衡.通过(火用)平衡与热平衡的对比分析和热效率与(火用)效率的分析计算,论述了(火用)平衡能更科学、更准确地反映轮窑实际用能状况.指出轮窑有效能(火用)主要损失在轮窑内部,而不在外部.     

集中式制冷与空调系统的热经济性分析

运用<火用>炯分析理论和热经济学中成本分摊法、孤立优化原理和<火用>定价方法理论,分析了制冷系统在不同蒸发温度和冷凝温度下的<火用>效率,计算了全空气空调系统几种典型送风方式的炯效率.在工程预算的基础上对炯价格进行了比较,得出了提高炯效率的方法,确定了整个系统热经济性的最优方案.     

拟协调九参数三角形板单元刚度

本文较为详细地叙述了拟协调九参数元单元刚度的推导过程,并利用矩阵和的方法推导出[C]矩阵,计算公式显得简洁并易于编制程序。我们在APPLE—Ⅱ微型计算机上进行了薄板和扁壳的计算,结果是令人满意的。     

制冷循环各过程(火用)损失的计算建模及影响因素

节能分析及优化已不只是能的量的问题,而是能的质与量的综合估价的问题。文中用VC 6.0编制了能与质综合评价的计算程序模块,用(火用)分析方法分析计算制冷系统循环各过程的(火用)损失、(火用)效率,并且分析影响(火用)损失的因素。找出了制冷系统节能部位和节能应采取的措施。给出一个易操作的计算软件可以方便地判断任何系统在(火用)损失最小,(火用)效率最大时,实现热泵节能优化的最佳方案。     

开式循环吸收式冷水机组火用分析模型的建立

介绍了开式循环吸收式冷水机组的工作原理及特点;运用热力学第二定律,从(火用)流的角度分别建立了系统部件以及湿空气和溶液的(火用)分析模型;并对系统(火用)效率进行了初步分析,为系统的(火用)分析奠定了理论基础.     

Exergetic cost analysis of a space heating system

In order to evaluate and improve the design of space heating systems with groundwater source heat pumps (GWHP), common design practices should be examined. In this paper, a GWHP system with common design is studied. The COP of the heat pump is 3.5 at design condition. The system is divided into five subsystems, and exergetic cost analysis is performed on it based on structural theory of thermoeconomics. The results show that the three largest relative exergy destructions and lowest exergy efficiencies occur in power generation and distribution, heat pump, and terminal unit subsystems with relative exergy destructions of 71.2%, 17.1% and 7.02% and exergy efficiencies of 32.8%, 54.8% and 65.6% respectively. The three subsystems also have the largest increases of unit exergetic costs of 2.04 W/W, 2.15 W/W, and 2.73 W/W respectively. Therefore, designers of GWHP space heating systems should pay close attention to heat pump and terminal unit subsystems, especially to the latter one because of its larger increase of unit exergetic cost. The unit exergetic cost of the system final exergetic product is 7.92 W/W. This value can be used to evaluate the system and compare it with others from the viewpoint of energy conservation.     

Multi-objective approach in thermoenvironomic optimization of a small-scale distributed CCHP system with risk analysis

Multi-objective optimization for designing of a small-scale distributed CCHP system has been performed. Small-scale combined cooling, heating, and power generation technologies represent a key resource to increase generation efficiency and reduce greenhouse gas emissions with respect to conventional separate production means. In the multi-objective optimization of the small-scale distributed CCHP system, the three objective functions including the exergetic efficiency, total levelized cost rate of the system product and the cost rate of environmental impact have been considered. The environmental impact objective function has been defined and expressed in cost terms however this objective has not been integrated with the thermoeconomic objective. The thermodynamic modeling has been implemented comprehensively while the economic analysis conducted in accordance with the total revenue requirement (TRR) method. One of the most suitable optimization techniques namely as genetic algorithm has been applied to find the set of Pareto optimal solutions with respect to the aforementioned objective functions. In the present work, reliability and availability are introduced in the thermoenvironomic model of the system, so that redundancy is embedded in the optimal solution. Risk analysis is used for decision-making of the final optimal solution from the obtained Pareto optimal frontier.     

Exergetic assessment of transmission concentrated solar energy systems via optical fibres for building applications

Solar lighting with fibre optic bundles can be considered as a very promising option from the viewpoint of energy efficient green buildings. This study dealt with the exergetic analysis and the performance assessment of the system based on the idea of transmission concentrated solar energy via optical fibres (TCSEvOF).

Although the main objective of the present study includes the solar lighting to non-daylit areas, it could be possible to transform by additional components and some modifications for other applications, such as solar power generation, solar surgery, photobioreactors, hydrogen generation and photochemical reactions and solar pumped lasers. In the analysis, the experimental data obtained from the system composed of low cost dual sun tracking offset paraboloidal dish and fibre optic bundle and installed in Ege University Solar Energy Institute, Turkey were used. Monthly average hourly exergy efficiencies of the TCSEvOF system were calculated by applying the exergetic model. Exergy efficiencies varied between 1% and 28% in daytime depending on the solar radiation values along the whole year. The seasonal average exergy efficiencies were found to be 16%, 20%, 18%, and 7% for the spring, summer, autumn and winter seasons, respectively. Average annual exergy efficiency of the system for the whole year was obtained to be 15%. Parameters affecting the performance were discussed, while some suggestions towards increasing energy and exergy efficiencies of the system for further researches were made. It is expected that the model presented here would be beneficial to everyone involved in the design and performance evaluation of solar lighting with fibre optic bundles in building applications.     

Simulation and optimization of the performance in the air-conditioning season of a BCHP system in China

Building cooling, heating and power generation (BCHP) is expected to play an important role in the sustainable energy strategy for buildings. However, in many cases the performance of BCHP systems is not as good as predicted and thus perplexes designers and building owners. In this paper the performance of a typical BCHP system is investigated using thermodynamic and thermoeconomic analyses based on the simulation of off-design operation and the performance optimization of the system with the help of a great number of real operation data of the system and the master data supplied by manufacturers. Two optimization problems using exergetic efficiency and gross benefit of the whole BCHP system, respectively, as objective functions are developed in virtue of curve fitting. Computations result in various graphs, which as references are helpful for judging whether or not the system operation is correct. The graphs show that only with enough high load rates can the system operation yield positive benefits. The simulation tells that the fuel cost of BCHP in China accounts for 70–80% of its total cost and therefore is the most important factor in spreading BCHP in the country.     

Energy and exergy analysis of a ground-coupled heat pump system with two horizontal ground heat exchangers

In this paper we investigate of energetic and exergetic efficiencies of ground-coupled heat pump (GCHP) system as a function of depth trenches for heating season. The horizontal ground heat exchangers (HGHEs) were used and it were buried with in 1 m (HGHE1) and 2 m (HGHE2) depth trenches. The energy efficiency of GCHP systems are obtained to 2.5 and 2.8, respectively, while the exergetic efficiencies of the overall system are found to be 53.1% and 56.3%, respectively, for HGHE1 and HGHE2. The irreversibility of HGHE2 is less than of the HGHE1 as about 2.0%. The results show that the energetic and exergetic efficiencies of the system increase when increasing the heat source (ground) temperature for heating season. And the end of this study, we deal with the effects of varying reference environment temperature on the exergy efficiencies of HGHE1 and HGHE2. The results show that increasing reference environment temperature decreases the exergy efficiency in both HGHE1 and HGHE2.     

Thermodynamic and multi-objective optimisation of solar-driven Organic Rankine Cycle using zeotropic mixtures

This paper communicates the performance of low-grade solar heat source powered Organic Rankine Cycle (ORC). To investigate the system performance, first law and exergetic efficiencies, power output are evaluated and compared for zeotropic mixtures of (iso)butane/(iso)pentane and cyclohexane/R123. The results indicate that there exists an optimal mass fraction for which energy and exergetic efficiencies, and power output are maximum corresponding to a given value of expander inlet temperature compared with pure fluids. However, the specific volume flow ratio of the expander is higher for zeotropic mixtures; which results in a lower economy of mixtures than pure fluids. The use of an internal heat exchanger in the system improves cycle performance. Moreover, the multi-objective genetic algorithm further improves the performance of ORC and exhibits better exergetic efficiency 51–57% and 0–14.09% reduction in lower expander-specific volume flow ratio (v ₆/v ₅) than thermodynamically optimised ORC.     

Operation costs exergoeconomic of transcritical refrigeration cycle with carbon dioxide

ABSTRACT

In this work, the thermodynamic and exergoeconomic studies are performed to a single vapour compression refrigeration cycle which uses CO₂ as a refrigerant in transcritical conditions. This analysis establishes the behaviour of the compressor discharge pressure based on the gas cooler temperature, when it is operating at ambient conditions greater than 20°C. The effect of varying the cooling chamber temperature is also shown. In the analysis, the coefficient of performance (COP), exergetic efficiency and exergoeconomic operation costs for each equipment are obtained, considering a refrigeration capacity of 5 TR. For instance, at a gas cooler temperature of 45°C and a cooling chamber temperature of ?5°C, the maximum COP is 1.78 to a gas cooler pressure of 120 bar and the exergetic efficiency is 0.1556; however, operating at these conditions, it generates an exergoeconomic operation cost of 1.74?€?h^?1.     

Exergetic modeling and performance evaluation of solar water heating systems for building applications

Solar water heating (SWH) is a well-proven renewable energy technology and has been used in many countries of the world. The basic technology is straightforward, although there are a variety of various types of SWH systems. In the performance assessment of SWH systems, energy analysis (first law) method has been widely used, while the number of the studies on exergetic assessment is relatively low. The SWH system investigated consists of mainly three parts, namely a flat plate solar collector, a heat exchanger (storage tank) and a circulating pump. The main objectives of the present study are as follows, differing from the previously conducted ones: (i) to model and assess SWH systems using exergy analysis (second law) method as a whole, (ii) to investigate the effect of varying water inlet temperature to the collector on the exergy efficiencies of the SWH system components, (iii) to study some thermodynamic parameters (fuel depletion ratio, relative irreversibility, productivity lack and exergetic factor) and exergetic improvement potential, and (iv) to propose and present an exergy efficiency curve similar to the thermal efficiency curve for solar collectors. The system performance is evaluated based on the experimental data of the Izmir province, Turkey, which is given as an illustrative example. Exergy destructions (or irreversibilities) as well as exergy efficiency relations are determined for each of the SWH system components and the whole system. Exergy efficiency values on a product/fuel basis are found to range between from 2.02 to 3.37%, and 3.27 to 4.39% at a dead (reference) state temperature of 32.77 °C, which is an average of ambient temperatures at eight test runs from 1.10 to 3.35 p.m., for the solar collector and entire SWH system, respectively. An exergy efficiency correlation for the solar collector studied was also presented to determine its exergetic performance. It is expected that the model presented here would be beneficial to the researchers, government administration, and engineers working in the area of SWH systems for residential applications.     

Modeling and performance evaluation of ground source (geothermal) heat pump systems

This study deals with the energetic and exergetic modeling of ground source heat pump (GSHP) systems for the system analysis and performance assessment. The analysis covers two various GSHPs, namely a solar assisted vertical GSHP and horizontal GSHP. The performances of both GSHP systems are evaluated using energy and exergy analysis method based on the experimental data. Energy and exergy specifications are also presented in tables. Some thermodynamic parameters, such as fuel depletion ratio, relative irreversibility, productivity lack and exergetic factor, are investigated for both systems. The results obtained are discussed in terms of energetic and exergetic aspects. The values for COP_HP ranged from 3.12 to 3.64, while those for COP_sys varied between 2.72 and 3.43. The exergy efficiency peak values for both whole systems on a product/fuel basis were in the range of 80.7% and 86.13%. It is expected that the model presented here would be beneficial to everyone dealing with the design, simulation and testing of GSHP systems.     

Comparative performance analysis for endoreversible simple air refrigeration cycles considering ecological,exergetic efficiency and cooling load objectives

On the basis of exergetic analysis, the performance analysis and optimisation of endoreversible simple air refrigeration cycles with constant-temperature heat reservoirs is carried out by using the finite-time thermodynamic method in this paper. The expressions for cooling load, ecological function and exergetic efficiency of the refrigeration cycle are derived. The influences of pressure ratio of the compressor and allocation of heat exchanger inventory on the optimal performance of the cycle are investigated by detailed numerical examples. Performance comparisons between ecological optimisation objective, exergetic efficiency optimisation objective and traditional cooling load optimisation objective are performed. The results may provide guidelines for the design and optimisation of practical refrigeration plants.