The Thermal Character of the Underwater Heat Exhausting Source

The underwater heat exhausting source can cause the thermal difference of the surrounding and surface water.In this paper,the thermal character caused by the underwater heat exhausting source is studied by numerical simulation and experiment.The results show that the thermal floating distance is related with the sailing velocity of the underwater target.The higher the velocity is,the longer the hot wake is,and the broader the hot scope is.The relative distance of the thermal floating spot is almost in a logarithmic law with the velocity.The experimental results are accordant with the numerical simulation,and the obvious hot wake can be observed by the moving underwater heat exhausting source testing with temperature sensors and infrared camera.

Experimental Study of Thermoelectric Heat Pump Water Heater with Exhaust Heat Recovery from Kitchens

A new kind of thermoelectric heat pump water heater for kitchens exhaust heat recovery was presented,and its performances were investigated under different operating voltages.The experiment results show that the coefficient of performance decreases and the temperature difference between the hot and cold sides becomes larger with the increase of the operating voltage,but the heating time becomes short.The higher the temperature of water,the greater the temperature difference between the hot and cold sides,leading to a smaller coefficient of performance.Under an exhaust temperature of 36 ℃,the coefficient of performance decreases from 1.66 to 1.22 when the temperature of water increases from 28 ℃ to 46 ℃ with operating voltage 16 V.Performance tests illustrate that,compared with the conventional electrical water heaters,the new kind of thermoelectric heat pump water heater is more coefficient.

Simulation of Gas-Fired Triple-Effect LiBr/Water Absorption Cooling System with Exhaust Heat Recovery Generator

An exhaust heat recovery generator is proposed to be integrated with conventional gas-fired triple-effect LiBr/water absorption cooling cycles to improve system energy efficiency. As a case study, simulation of the novel cycle based on promising parallel flow with cooling capacity of 1 150 kW is carried out under various heat recovery generator vapor production ratios ranging from 0 to 3.5%. The life cycle saving economic analysis, for which the annual gas conservation is estimated with Bin method, is employed to prove the worthiness of extra expenditure. Results show that the optimum gas saving revenue is obtained at 2.8% heat recovery generator vapor production ratio with 42 kW exhaust heat recovered, and the system energy efficiency is improved from 1.78 to 1.83. The initial investment of exchanger can be paid back within 7 years and 9 000 CNY of gas saving revenue will be achieved over the 15-year life cycle of the machine. This technology can be easily implemented and present desirable economic effects, which is feasible to the development of triple-effect absorption cycles.

Techno-economic feasibility assessment of a diesel exhaust heat recovery system to preheat mine intake air in remote cold climate regions

Underground mines in Arctic and Subarctic regions require the preheating of mine intake air during winter.The cold fresh air of those remote areas can be as severe as
40℃ and commonly needs to be heated to around+3℃.This extensive amount of heating is usually provided by employing large-size air heaters,fueled by diesel,propane,natural gas,or heavy oil,leading to high energy costs and large carbon footprints.At the same time,the thermal energy content of a diesel generator sets(gen-sets)exhaust is known to be one-third of the total heating value of its combusted fuel.Exhaust heat recovery from diesel gen-sets is a growing technology that seeks to mitigate the energy costs by capturing and redirecting this commonly rejected exhaust heat to other applications such as space heating or pre-heating of the mine intake air.The present study investigated the possibility of employing a simple system based on off-theshelf heat exchanger technology,which can recover the waste heat from the exhaust of the power generation units(diesel gen-sets)in an off-grid,cold,remote mine in Canada for heating of the mine intake air.Data from a real mine was used for the analysis along with environmental data of three different location-scenarios with distinct climates.After developing a thermodynamic model,the heat savings were calculated,and an economic feasibility evaluation was performed.The proposed system was found highly viable with annual savings of up to C$6.7 million and capable enough to provide an average of around 75%of the heating demand for mine intake air,leading to a payback period of about eleven months or less for all scenarios.Deployment of seasonal thermal energy storage has also been recommended to mitigate the mismatch between supply and demand,mainly in summertime,possibly allowing the system to eliminate fuel costs for intake air heating.

The Efficiency Analysis of the Exhaust Air Heat Pump System

This paper is based on long term parameter measurements of the exhaust air heat pumps (EAHP) system in a new built apartment building. The building was equipped with an exhaust air ventilation system and exhaust air heat pump for ventilation heat recover. The results of the measurements show that the COP of the EAHP is mainly related to the temperature graph of the heating system and the supply temperature of domestic hot water (DWH). During the measurement period some other impact factors, such as the quality of maintenance, the nighttime temperature graph of the heating system, the reduction of the exhaust air flows in case of low temperatures, mistakes in designing and low building quality, have also played a role. An analysis of energy consumption shows that in winter conditions the COP is about 3.0 and in the transition period about 3.3. The energy recovery value of the EAHP is 0.5.

Gas Flow Development Through Tandem Heat Exchangers Inside Exhaust Nozzle by Using Porous Medium Model

A computational study on the flow development through tandem double-U-shaped-tubes compact heat exchangers inside exhaust nozzle is presented.In order to simplify the computational process on modeling the flow field,the compact heat exchanger is modeled as a porous matrix by using an isotropic porous medium assumption,which makes two-dimensional numerical simulation realistic.With the use of an existed quadratic relation which connects the pressure drop with the inlet velocity in the external part of the heat exchanger,the permeability and drag coefficient in the porous medium model are determined and a corresponding computational method validation is also made.Two schemes of tandem double-U-shaped-tubes compact heat exchangers are numerically analyzed.In relative to the baseline scheme,the modified scheme is improved by smoothing the nozzle expansion,varying heat exchanger mounting angle and installing boat-tail ramp at the trailing edge of the last heat exchanger.The results show that the pressure losses due to the existence of local recirculation zones and inappropriate distribution of the flow field are reduced in the modified scheme.The pressure loss coefficient is decreased from 1.7% under the baseline scheme to 1.2% under the modified scheme.

Experiment Study on the Exhaust-Gas Heat Exchanger for Small and Medium-Sized Marine Diesel Engine

This paper aims to design a special exchanger to recover the exhaust gas heat of marine diesel engines used in small and medium-sized fishing vessels,which can then be used to heat water up to 55°C–85°C for membrane desalination devices to produce fresh water.A new exhaust-gas heat exchanger of fins and tube,with a reinforced heat transfer tube section,unequal spacing fins,a mixing zone between the fin groups and four routes tube bundle,was designed.Numerical simulations were also used to provide reference information for structural design.Experiments were carried out for exhaust gas waste heat recovery from a marine diesel engine in an engine test bench utilizing the heat exchanger.The experimental results show that the difference between heat absorption by water and heat reduction of exhaust gas is less than 6.5%.After the water flow rate was adjusted,the exhaust gas waste heat recovery efficiency was higher than 70%,and the exhaust-gas heat exchanger’s outlet water temperature was 55°C–85°C at different engine loads.This means that the heat recovery from the exhaust gas of a marine diesel engine meets the requirement to drive a membrane desalination device to produce fresh water for fishers working in small and medium-sized fishing vessels.

A Model for Regional Energy Utilization by Offline Heat Transport System and Distributed Energy Systems—Case Study in a Smart Community, Japan

Under the Kyoto Protocol,Japanwas supposed to reduce six percent of the green house gas (GHG) emission in 2012. However, until the year 2010, the statistics suggested that the GHG emission increased 4.2%. What is more challenge is, afterFukushimacrisis, without the nuclear energy,Japanmay produce about 15 percent more GHG emissions than1990 inthis fiscal year. It still has to struggle to meet the target set by Kyoto Protocol. The demonstration area of “smart community” suggests Japanese exploration for new low carbon strategies. The study proposed a demand side response energy system, a dynamic tree-like hierarchical model for smart community. The model not only conveyed the concept of smart grid, but also built up a smart heat energy supply chain by offline heat transport system. Further, this model promoted a collaborative energy utilization mode between the industrial sector and the civil sector. In addition, the research chose the smart community inKitakyushuas case study and executed the model. The simulation and the analysis of the model not only evaluate the environmental effect of different technologies but also suggest that the smart community inJapanhas the potential but not easy to achieve the target, cut down 50% of the CO2 emission.

An Evaluation of Measures Regarding Road Traffic against the Urban Heat Island in the Tokyo Ward Area, Japan

This study aims to evaluate measures against the Urban Heat Island (UHI) regarding artificial exhaust heat of road traffic using Geographic Information Systems (GIS) in the Tokyo Ward Area where the degree of UHI is particularly strong. We developed a GIS database that reflected road traffic conditions, and calculated the volume of artificial exhaust heat of road traffic to evaluate measures against the UHI. The findings of this study can be summarized in the following three points. 1) Artificial exhaust heat volume for moving targets was remarkably higher than that of stationary targets and, in particular, artificial exhaust heat volume was high on roads with remarkable numbers of vehicles and running speeds such as expressways and ring roads. 2) In UHI- related policy for moving targets, the suppression of waste heat through choice of fuel burned, improvement of traffic flow by securing space for cyclists and pedestrians, development of bypasses, and upgrading signal control managed to reduce artificial exhaust heat volume, even though there were differences in degree of reduction. 3) In UHI-related policy for stationary targets, special road surfaces and the increase in efficiency of energy consumption equipment achieved a reduction ratio of around 30% in artificial exhaust heat volume, more than moving targets as well as making it possible to expect a reduction in artificial exhaust heat volume on a wide scale.

金属丝网强化余热回收烟气换热器的试验与数值研究

为探究金属丝网强化元件在余热回收烟气换热器中的应用可行性及其性能表现,对嵌有金属丝网的通道的流动与换热性能开展试验与数值研究。对嵌入不同孔隙率金属丝网的通道进行了试验研究,基于FLUENT软件进行了模拟计算和流场分析,并分析了丝网高度对流动和传热性能的影响。结果表明,相比于传统平直翅片,嵌入金属丝网后通道综合性能指标最大提高58%。综合性能随孔隙率的提高先增后减,0.945为最佳孔隙率。同时,使用高度与流道高度一致的金属丝网,可以获得最佳综合性能。在相同压力损失下,金属丝网通过均匀流体温度、破坏边界层可以比平直翅片通过增加传热面积获得更好的综合性能,证明了金属丝网作为烟气换热器强化元件的可行性。

Performance Optimization of Dual Pressure Heat Recovery Steam Generator (HRSG) in the Tropical Rainforest

This work evaluates the performance optimization of heat recovery steam generator system in Afam VI power plant, Rivers State. Nigeria. Steady state monitoring and direct collection of data from the plant was performed including logged data for a period of 12 months. The data were analysed using various energy equations. Hysys software was used to model the temperature across the heating surfaces, and MATLAB software was used to determine the heat transfer coefficient, heat duties, steam flow, effectiveness of the HRSG. The optimization technique was carried out by varying the exhaust gas flow, exhaust gas temperature, steam pressure and the theoretical introduction of duct burner for supplementary firing. The results show that between 490℃ and 526℃, the percentage increase in the overall heat absorbed in the HRSG is 37.39%. It also show that for an increase in the exhaust gas mass flow by 80 kg/s, the steam generation increase by 19.29% and 18.18% for the low and high pressure levels respectively. The overall result indicates an improvement in the HRSG energy efficiency and steam generation. As the exhaust gas mass flow and temperature increases, the steam generation and system effectiveness greatly improved under the various considerations, which satisfy the research objective.

侧部双点排烟模式排热效率研究

为探究隧道火灾侧部排烟口排热效率的表达公式,采用理论分析推导出排热效率与火灾热释放速率、排烟风速、排烟口距地面高度、排烟口间距4个影响参数的量纲一关系式,通过FDS数值模拟研究不同因素影响下的烟流特征并对数据进行拟合,确定了排热效率与这4个影响参数的关系。结果表明,在侧部双点排烟模式下,排热效率随火灾热释放速率增大呈-0.33次方减小关系,与排烟口排烟风速呈0.23次方增长关系,与排烟口距地面高度呈1.25次方增长关系,与排烟口间距呈-0.57次方减小关系,最终通过线性拟合建立了考虑吸穿影响的侧部双点排烟模式下排烟口处排热效率的模型。研究结果可为隧道侧部排烟系统的设计提供参考。

某核电厂电气仪控房间火灾排烟温度分析

对某核电厂电气厂房的2个电气仪控房间进行了火灾排烟温度模拟分析。模拟计算了排烟系统不同时刻启动时,这2个防火空间室内空气温度的变化情况。结果表明:排烟系统启动后房间空气温度迅速降低,然后逐渐升高,最后随着火灾热释放速率的降低而逐渐降低;对于手动启动的排烟系统,需及时启动才能有效排除火灾中的烟气;需合理设置排烟防火阀,以保护排烟风机等。

Study of the Influence of the Distance between Smoke Outlets and Fire Source on Smoke Flow Characteristics in Tunnel Fires

This paper explores the smoke flow characteristics in tunnel fires,giving a particular emphasis on the effects of different distances between the smoke outlets and the fire source.It examines the smoke behavior under different conditions,including variations in heat release rates,exhaust volumetric flow rates,spacing between smoke outlets,and the longitudinal fire source positions.Results indicate that altering the fire source positions and the smoke outlets in the tunnel leads to variations in the properties of smoke flow both the fire source upstream and downstream;the distance between fire source and smoke outlet increases gradually,airflow rate decreases initially and eventually reaches a stable state.Similarly,smoke mass flow rate exhibits an increasing trend that eventually reaches a stable state.Moreover,the heat exchange between the tunnel walls and hot smoke increases as the smoke outlet moves further away from the fire source.This interaction leads to a reduction in the heat exhaust coefficient and a decrease in the distance the smoke spreads.This study investigates the impact of altering the relative longitudinal fire source positions and smoke outlet on smoke flow characteristics by numerical simulation.A theoretical analytical method is used to give a predictive model for the heat exhaust coefficient and the smoke spreading distance.This research can support the theory and technical process of tunnel smoke exhaust prevention and control.

冷却通道对引射器红外辐射特性影响的研究

为降低燃气轮机排气系统中的引射器排气温度,从而减少排出燃气的红外辐射强度,本文提出了一种具有冷却通道的亚音速引射器结构,并提出了评价冷却通道引射器的综合系数。在原有的引射器喷嘴内增加冷却通道,使冷气直接与主流中心位置的高温气体掺混,破坏排气包覆性分布,达到提高主流温度均匀性、降低中心温度的目的。本文运用数值模拟的方法,研究引射器内冷却通道数量、冷却通道进深和排气通道的排布对引射器内阻力特性、换热特性、出口温度分布特性的综合影响。研究结果表明:单排冷却通道排布时,通道数量与换热特性成正比,与阻力损失成反比;双排冷却通道排布时,阻力损失降低。双排12通道引射器可有效降低出流总温,均匀主流温度,综合系数最高。

汽车尾气温差发电系统瞬态回收性能分析

为了预测温差发电(thermoelectric generator, TEG)系统的动态特性,基于COMSOL Multiphy-sics建立了用于求解温差发电系统温度场分布的瞬态计算流体力学(computational fluid dynamics, CFD)模型和用于研究温差发电模块瞬态响应特性的分析模型,提出了混合瞬态CFD-分析模型,并经过瞬态试验验证.结果表明:由于热惯性的影响,TEG系统的转化效率会出现一个瞬时的较高值;相较于尾气温度和质量流量的瞬态波动,热电半导体的热端温度和冷端温度会存在时滞;在美国环保局的高速公路燃油经济性测试(highway fuel economy test, HWFET)模式循环工况下,瞬态模型求解得到整个温差发电系统的平均输出功率、平均转化效率分别为35.63 W和3.40%,瞬态模型的输出电压平均误差为6.41%;该模型能够以较高的精度及较短的计算时间预测温差发电系统在瞬态热源激励下的瞬态响应特性.

侧向排汽凝汽器设计与研发

介绍了侧向排汽凝汽器的设计要点及关键技术,包括汽轮机与凝汽器的整体布置方案、凝汽器管束布置、凝汽器数值传热和真空力平衡方式等。侧向排汽机组布置紧凑,减少了土建成本,具有良好的社会及经济效益,通过对其设计与研发的介绍,为侧向排汽机组的推广提供了技术支持。

跨临界CO_(2)热泵系统最优风量实验研究

为探究在压缩机固定转速下风量对跨临界CO_(2)循环系统性能的影响,以及确定使系统达到最大COP的最优风量,搭建了跨临界CO_(2)热泵系统实验台。研究了室内、外风量对系统制热性能的影响,并总结出确定最优风量的方法。结果表明:跨临界CO_(2)热泵系统在制热模式下运行,当室内风量固定时,随着室外风量的增大,排气压力与室内出风温度均呈现出先升高后趋于平稳,系统制热COP随着室外风量的增大存在一个最优值;为准确预测最优室外风量,引入最优排气压力偏离度σ和参数变化率δ作为最优室外风量的判断依据,当σ=0.48%,δ=1.4%时,系统处于最优室外风量,即对应系统在最大的COP下运行。经过实验验证,最优室外风量预测值误差在5%以内,该方法具有较高的准确性。

血浆t-PAIC对热射病性凝血病的诊断价值

目的探讨血浆组织型纤溶酶原激活物-抑制剂复合物(t-PAIC)对热射病性凝血病(heat stroke-induced coagulopathy,HIC)的诊断价值。方法回顾性分析2018年5月至2023年9月解放军联勤保障部队第九〇八医院重症医学科收治的65例热射病患者,根据热射病严重程度分为热衰竭(heat exhaustion,HE)组(n=32)、热射病无凝血病(nHIC)组(n=13)和HIC组(n=20),比较三组患者t-PAIC水平变化,并进行相关性分析,绘制受试者工作特征(ROC)曲线,评估t-PAIC诊断HIC的价值。结果与HE组比较,nHIC组和HIC组t-PAIC显著升高[ng/mL:2.69(1.46~5.07)vs.8.70(3.99~20.41)和21.99(12.36~43.27),P<0.05];与nHIC组比较,HIC组t-PAIC显著升高(P<0.05)。Spearman相关分析显示,热射病患者乳酸水平、APACHEⅡ评分与t-PAIC水平均呈正相关(相关系数r分别为0.500、0.645,P<0.001)。t-PAIC诊断HIC的曲线下面积为0.843(P<0.05);当t-PAIC截断值为11.43 ng/mL时,其敏感度为80.0%,特异度为82.2%。结论血浆t-PAIC水平与热射病严重程度相关,可作为诊断HIC的分子标志物。

济南市不同类型燃煤供暖企业废气组分特征及排放估算

利用稀释通道采样法于2022年12月对济南市热电厂、热源厂、电厂3种类型冬季燃煤供暖典型企业废气细颗粒物进行采样,结合在线监测数据分析了SO_(2)、NO_(x)、PM_(2.5)和NH3排放情况及PM_(2.5)化学组分特征,并估算了济南市冬季3种类型供暖企业PM_(2.5)主要组分排放量。结果表明:3种类型燃煤供暖企业SO_(2)、NO_(x)、PM_(2.5)和NH3排放浓度均值范围分别为1.01-15.0、18.6-39.8、0.592-2.37、0.125-2.00 mg∙m^(-3),排放浓度差异较大,其中使用含硫率较低的燃煤供暖热源厂SO_(2)排放浓度明显低于热电厂和电厂。热电厂和电厂SO_(2)、NO_(x)、PM_(2.5)排放浓度均满足国家超低排放限值要求,热源厂满足山东省地方燃煤锅炉排放标准限值要求。PM_(2.5)组分特征分析结果表明不同供暖类型企业排放主要组分存在较大差异,其中热电厂主要为SO_(4)^(2−)(11.8%)、OC(17.1%),热源厂主要为Ca^(2+)(11.6%)、OC(33.5%),电厂主要为SO_(4)^(2−)(23.0%)、OC(18.6%),3类企业OC占比均远高于国内其他地区,这可能与本地调查企业煤质及环保设施运行工况等有关,热电厂和电厂高的SO_(4)^(2−)占比与燃料含硫率较高有关。经估算,2022-2023年供暖季济南市3种类型供暖企业排放烟气PM_(2.5)组分中水溶性离子总量最多,排放总量为3.74×10^(4) kg,是碳组分的2.07倍,是无机元素的5.18倍,其中水溶性离子排放总量以电厂最多,排放量为3.01×10^(4) kg,占比为80.5%;热源厂水溶性离子排放量是热电厂的4.14倍,无机元素排放量以电厂最高,排放量为4.96×103 kg,热源厂的水溶性离子(0.605 kg∙m^(-3)烟气)、碳组分(0.715 kg∙m^(-3)烟气)、无机元素(0.161 kg∙m^(-3)烟气)均呈现高排放特征,建议进一步加强对冬季热源厂PM_(2.5)中碳组分及水溶性离子的管控,关注脱硝设施的稳定运行。