Investigation on thermal performance of glazed solar chimney walls

This paper reports investigation on the thermal performance of glazed solar chimney walls (GSCW) under the tropical climatic conditions of Thailand. The GSCW consisted of double glass panes with an air layer and openings located at the bottom (room side glass pane) and at the top (ambient side glass pane). A prototype of GSCW was integrated into the southern wall of a small room of 2.8 m³ volume. Its dimensions were as follows: 0.74 m height, 0.50 m width and 0.10 m air gap. The size of openings was 0.05 × 0.5 m². With a clear glass of 6 mm thickness, velocity field measurement indicated that the induced airflow rate was about 0.13–0.28 m³/s. The temperature difference between room and ambient was less than that with a single layer clear glass window. The reduction of daylight due to the double glass layer is negligible. Comparison between simulated and experimental results showed a reasonable agreement, therefore, the developed numerical model is valid and could be used as a tool for the design of GSCW.     

Simulation of indoor temperature and humidity conditions including hygrothermal interactions with the building envelope

The hygrothermal behaviour of the building envelope affects the overall performance of a building. Numerous tools exist for the simulation of the heat and moisture transfer in the building envelope and whole building simulation tools for energy calculations. However, working combinations of both models for practical application are just about to be developed. In this paper such a combined model, that takes into account moisture sources and sinks inside a room, input from the envelope due to capillary action, diffusion and vapour absorption and desorption as a response to the exterior and interior climate conditions as well as the well-known thermal parameters will be described. The new model is validated by performing a series of field experiments and the moisture buffering capacity of the building envelope is investigated. In the conclusions the possible range of future applications of hygrothermal building performance models is addressed and the needs for further research are identified.     

回风源热泵技术在煤矿的应用与实践研究

热泵技术是近年来倍受关注的新能源技术,针对某矿井总回风蕴含热能较大、回收利用价值高的优势,提出了利用回风源热泵技术将回风热能交换到循环水中,作为热泵系统低温热源的方案,结合矿井的实际情况和实测数据出发,进行了方案实施。经使用验证,该方案达到了节能环保的目的,年节约煤炭2 500 t,减排CO26 365 t,减排SO249 t,取得了良好的经济效益与社会效益。     

A novel household refrigerator with shape-stabilized PCM (Phase Change Material) heat storage condensers: An experimental investigation

In this study, a kind of shape-stabilized phase change material (PCM) was adopted for constructing heat storage condensers. And a novel household refrigerator equipped with the heat storage condensers was setup based on an ordinary double-door three-star compartment refrigerator. The experimental investigation on the characteristics of the novel refrigerator and an ordinary refrigerator was carried out under the ISO standard test conditions. For the novel refrigerator, part of the condensation heat was stored in the shape-stabilized PCM during the on-time and discharged to the environment while the compressor was off. Therefore, the heat dissipation of the novel refrigerator was continuous during a complete cycle (including a successive on-time and off-time period), different from the intermittent heat dissipation of the ordinary setup. Thus, the overall heat-transfer performances of the condensers could be significantly improved, which resulted in a lower condensation temperature, a higher evaporation temperature and a much larger subcooling degree at the condenser outlet. Compared to the ordinary refrigerator, the total cycle time and the ratio of on-time to the total cycle time of the novel refrigerator were much smaller, which led to more frequent starts of the compressor but lower energy consumption. Experiments demonstrated that the novel refrigerator could increase the energy efficiency by about 12% with only little increase of the cost.     

Energy saving analysis and thermal performance evaluation of a hydrogen-enriched natural gas-fired condensing boiler

Hydrogen-enriched natural gas (HENG) has attracted widespread attention due to its lower pollutant emissions and industrial decarbonization in the past decades. HENG combustion boosts the water content in the flue gas, which is highly favorable for condensing boilers to recover additional latent heat. The energy saving and thermal performance of a condensing boiler burning HENG were evaluated at a constant heat load of 2.8 MW in this study. The variations in combustion products and boiler efficiency were investigated based on the material balance and energy conservation. The heat transfer calculations were employed to evaluate the thermal performance of boiler heating surfaces. The energy recovery performance of the condenser was assessed via a thermal design method. Results show that H₂ enrichment enhances the radiation intensity of the flame due to the incremental triatomic gases with higher emissivity in the furnace. The heat absorption ratio increases with H₂ enrichment in the radiative heating surface, while it shows a reverse tendency in the convective heating surface. The condensing boiler efficiency based on lower heating value increases from 101.83% to 110.60%, the total heat transfer rate of the condenser increases from 2.77 × 10⁵ W to 4.61 × 10⁵ W, and the total area required decreases from 46.45 m² to 42.16 m², as the H₂ enriches from 0 to 100% under the exhaust flue gas temperature of 318 K. Although the amount of recoverable heat in the exhaust flue gas increases considerably after H₂ blending, the original condenser with natural gas as the designed fuel could meet the requirements of the heat recovery for HENG without increasing the extra heating surface. When the H₂ fraction is enriched from 0 to 100%, CO₂ emission intensity drops from 6.05 × 10⁻⁸ kg J⁻¹ to 0. This work may offer some theoretical references for the application and generalization of HENG condensing boilers.     

Experimental investigation of aluminum oxide nanofluid on heat pipe thermal performance

In this research, the effect of using aluminum oxide nanofluid (pure water mixed with Al₂O₃ nanoparticle with 35 nm diameter) on the thermal efficiency enhancement of a heat pipe on the different operating state was investigated.     

The impact of household behavioral changes on GHG emission reduction in Lithuania

It is commonly understood that households must change their behavior to reduce problems related increased energy consumption and climate change therefore in the search of cheap GHG emission reduction measures households are an important target group because they are responsible for more than 20% of total energy consumption in developed countries. In addition waste management and responsible consumption of products are the key issues in GHG emission reduction.The aim of the paper is to assess GHG emission reduction potential in households in terms of behavioral changes towards sustainable consumption. The review of literature on analysis of households behavioral changes impact on GHG emission reduction was performed; the daily survey of household agenda and energy use records were performed in Lithuania for two scenarios – baseline and GHG emission reduction scenario including energy saving. GHG emission reduction potential in household was assessed based on daily survey data and energy consumption records by applying carbon calculator based on modified coefficients. Evaluated GHG emission reduction potential in households was compared with GHG emission reduction potentials in other sectors of Lithuania. Based on analysis performed in the paper the tools to promote household behavioral changes towards sustainable consumption were proposed.     

Energy saving and emission reduction: A project of coal-resource integration in Shanxi Province,China

The small or middle coal mines with illegal operations in developing countries or regions can cause bad energy waste and environmental disruption. The project of coal-resource integration in Shanxi Province of China gives a new idea or an approach to energy saving and emission reduction. It is a social- and economic-ecological project. The paper shows the targets of energy saving and emission reduction in Shanxi Province, and analyses the aims, significance, design process and implementation of the integration project. Based on that, the paper discusses the challenges and opportunities the project brings. The analysis shows that the project of coal-resource integration in developing countries or regions can effectively improve mining technologies, collect capital and impel international cooperation and exchange. Finally, the paper analyses the concerns about the future, including the possible problems of implementation period, industrial updating, environmental impact and re-employment. However, the successful integration of coal resources can mitigate energy crisis and climate crisis and promote cleaner production effectively.     

Experimental investigation of heat transfer and turbulent flow friction in a tube fitted with perforated conical-rings

Perforated conical-ring (PCR) is one of the turbulence-promoter/turbulator devices for enhancing the heat transfer rate in a heat exchanger system. In the present paper, the influences of the PCR on the turbulent convective heat transfer (Nu), friction factor (f) and thermal performance factor (η) characteristics have been investigated experimentally. The perforated conical-rings (PCRs) used are of three different pitch ratios (PR = p/D = 4, 6 and 12) and three different numbers of perforated holes (N = 4, 6 and 8 holes). The experiment conducted in the range of Reynolds number between 4000 and 20,000, under uniform wall heat flux condition and using air as the testing fluid. The experimental results obtained by using the plain tube and the tube equipped with the typical conical-ring (CR) are also reported for comparison. It is found that the PCR considerably diminishes the development of thermal boundary layer, leading to the heat transfer rate up to about 137% over that in the plain tube. Evidently, the PCRs can enhance heat transfer more efficient than the typical CR on the basis of thermal performance factor of around 0.92 at the same pumping power. Over the range investigated, the maximum thermal performance factor of around 0.92 is found at PR = 4 and N = 8 holes with Reynolds number of 4000.     

Investigation on generated power of thermoelectric roof solar collector

The aim of this paper was to conduct lab-scale investigation of a new roof design concept termed “the thermoelectric roof solar collector (TE-RSC)” for power generation using solar energy. The TE-RSC was composed of a transparent acrylic sheet, air gap, a copper plate, thermoelectric modules and a rectangular fin heat sink. The incident solar radiation heats up the copper plate so that a temperature difference is created between the TE module that generates a direct current. This current generated was used to run a fan for cooling the TE modules. The TE-RSC surface area was 0.0525 m² and 10 thermoelectric cooling modules (Tianjin Lantian model TEC1-12708) were used. Investigations were done by varying solar radiation, simulated by using a halogen lamp, between 400 and 1000 W/m².It was found that this new roof design can generate about 1.2 W under solar radiation intensity of about 800 W/m² at ambient temperature varying between 30 and 35 °C. The corresponding air velocity generated by the ventilation fan was about 1.7 m/s. Therefore, the proposed TE-RSC concept seems to be an interesting new alternative for various purposes such as power generation in remote areas, roof heat gain reduction and indoor ventilation of spaces.     

Studies on the retrofit of heat exchanger network based on the hybrid genetic algorithm

The retrofit of heat exchanger networks (HENs) is an important branch of investigation for systematic heat integration. The studies on the economical and efficient retrofit techniques are very important for the high energy-consumption enterprises to save energy, protect environment and improve their market competitiveness. Because the retrofit of HEN is an optimization problem normally solved by a mixed integer nonlinear program (MINLP) which requires enormous solution space, it is very difficult to solve it with the traditional optimization methods. In this paper, by the analysis of an existing heat exchanger network, the hybrid genetic algorithm is applied to obtain the optimal retrofitted HEN with full utilization of the existing heat exchangers and structures. Two examples are taken to show the better effect of the retrofit method with the optimal new heat exchangers and re-piping cost and energy saving.     

Experimental investigation of the influence of lubricating oil on heat pump performance

Experimental results are presented which demonstrate the effect of lubricating oil on the COP and evaporator performance of refrigeration and heat pump systems. These are compared with the predictions of a simple theoretical analysis and it is shown that the agreement is satisfactory. It is demonstrated that evaporator heat extraction can be degraded by as much as 50 per cent and the COP by up to 30 per cent when compared to the performance indicated by the properties of pure refrigerants for systems containing up to 15 per cent oil. An interesting phenomenon is also demonstrated, wherein there is a clearly identifiable optimum setting for the evaporator superheat control, and the way in which this varies with oil concentration is indicated.     

The energy saving obtainable with solar heating and heat pumps in a northern climate

The energy saving obtainable with active solar heating and heat pumps has been studied for several years in the Northern climate of Finland. The studies deal mainly with small houses. A computer program is developed which calculates hour by hour the annual energy balance of different heating systems. The performance, of the heating systems are also measured in inhabited houses. The calculations show that the useful solar energy obtainable from the collector is 50–400 kWh/m² annually depending on the system and the collector size. A heat pump in the system is very advantageous, because it keeps the heat losses low and the collector efficiency high. It approximately doubles the energy obtainable. The measurement results have not been as good as expected. The solar energy obtained from the collector has been 120–160 kWh/m² annually. The main reasons for the low solar energy are design and equipment faults and the shading effects. The best energy saving device is the earth heat pump. It is also therefore very advantageous that the peak power demand decreases markedly. When the area of the earth pipes is large enough, energy may be extracted from earth through the whole year. The annual coefficient of performance is 2–3. Also a heat pump which extracts heat from exhaust air in dwelling houses has been very promising.     

节能减排浅论

简述节能减排的沿革,介绍节能减排的四个内涵,并且对节能减排的经济学机制和市场机制进行阐述,最后对能源、经济、环境相互协调的可持续发展能源体系发表看法。     

Experimental investigation of silver nano-fluid on heat pipe thermal performance

Nano-fluid is employed as the working medium for a conventional 211 μm wide × 217 μm deep grooved circular heat pipe. The nano-fluid used in this study is an aqueous solution of 35 nm diameter silver nano-particles. The experiment was performed to measure the temperature distribution and to compare the heat pipe thermal resistance using nano-fluid and DI-water. The tested nano-particle concentrations ranged from 1 mg/l to 100 mg/l. The condenser section of the heat pipe was attached to a heat sink that was cooled by water supplied from a constant-temperature bath maintained at 40 °C.At a same charge volume, the measured nano-fluid filled heat pipe temperature distribution demonstrated that the thermal resistance decreased 10–80% compared to DI-water at an input power of 30–60 W. The measured results also show that the thermal resistances of the heat pipe decrease as the silver nano-particle size and concentration increase.     

A comprehensive investigation of a low-energy building in Sweden

In Sweden, the building sector alone accounts for almost 40% of the total energy demand and people spend more than 80% of their time indoors. Reducing energy demand in the buildings is essential to the achievement of a sustainable built environment. At the same time, it is important to not deteriorate people's health, well-being and comfort in buildings. Thus, designing healthy and energy efficient buildings are one of the most challenging tasks for building scientists. A low-energy building that uses less than half of the purchased energy of a comparable typical Swedish building has been investigated from different viewpoints in an attempt to represent the building at different system levels. First, the ventilation performance in different rooms using the tracer gas method is reported. Second, results from simulations and in situ measurements are used to analyse the building's power demand and energy performance. The household's behaviour and their impact on energy usage as well as acceptance are reported. Finally, the CO₂ emissions with regard to the energy usage are analysed on the basis of different supply energy forms from surrounding energy systems, for example a Swedish and European electricity mix, or district heating as a substitute for electrical heating.     

酒店行业节能调查与分析

酒店是大型公共建筑中能耗较高的建筑之一,具有巨大的节能潜力和社会示范效应。本文选取部分典型酒店作为研究案例,对酒店的节能状况进行调查与分析,总结了酒店行业的主要节能技术及节能管理经验,为酒店行业全面实施节能行动,以及通过酒店的窗口和示范效应推动全社会开展节能行动,提供了值得借鉴的经验,提出了具有针对性的相关建议。     

磁场对燃料分子微观状态的影响

本文对磁化后燃料分子的红外吸收光谱、紫外吸收光谱进行了分析，发现红外吸收峰向高波数明显位移，红外吸收强度、紫外吸收强度增强，表明磁化后燃料分子微观状态发生了改变．测试由分子微观状态决定的燃料性质也发生明显变化，证明燃料分子微观状态的改变是发动机磁化消烟节油技术的理论依据．     

大型热载体锅炉节能问题的探讨

文章例举了两个有机热载体锅炉在不同行业中的应用实例，说明了大型有机热载体锅炉节约能源提高效率的有效途径。     

加快节能减排技术推广的思路与建议

加快节能减排技术推广是促进山西绿色转型发展的重要途径。山西加快节能减排技术推广,必须坚持技术创新和传统产业技术改造相结合,坚持制度、政策引导和市场机制运作相结合,坚持政府为主导、企业为主体、群众广泛参与等原则;必须建立节能减排技术推广的制度和政策体系。