Circulation-Enhanced Tank Heating Using Shallow Profile Coil Bundles

Heavy fuel oils require heated tanks to facilitate their transportation and processing.This paper proposes and investigates threeand four-level heating coil bundles.Numerical study revealed that powerful large-scale circulation of the heated fluid enhances heat transfer,delivering 16.7%and 23%improvements to the average heat transfer coefficient for the three-and four-level bundles,respectively.Furthermore,this circulation improves oil mixing and limits the variation in bulk oil temperature to-0.3 to+1.3°C from the average.The study also quantified oil flow velocity near the bottom of the tank.The time-averaged horizontal components of velocity,estimated 25 mm and 50 mm above the bottom of the tank,exceed 2 mm/s and 4 mm/s,respectively.The proposed heating coil bundles feature a compact design that reduces the material and labor costs of construction and that,by occupying only a small portion of the bottom of the tank,improves accessibility,maintenance,and cleaning.

Water-Tank Experiment on the Thermal Circulation Induced by the Bottom Heating in an Asymmetric Valley

Water tank experiments were carried out to investigate the thermal convection due to the bottom heating in an asymmetrical valley under neutral and stably stratified approach flows with the Particle Image Velometry (PIV) visualization technique. In the neutral stratification approach flow, the ascending draft induced by bottom heating is mainly located in the center of the valley in calm ambient wind. However, with ambient wind flow, the thermal convection is shifted leeward, and the descending draft is located on the leeward side of the valley, while the ascending draft is located on the windward side. The descending draft is minorly turbulent and organized, while the ascending draft is highly turbulent. With the increase of the towing speed, the descending and ascending drafts induced by the mechanical elevation begin to play a more dominant role in the valley flow, while the role of the thermal convection in the valley airflow becomes limited. In the stable stratification approach flow, the thermal convection is limited by the stable stratification and no distinct circulation is formed in calm ambient wind. With ambient wind, agravity wave appears in the upper layer in the valley. With the increase of the ambient wind speed, a gravity wave plays an important role in the valley flow, and the location and intensity of the thermal convection are also modulated by the gravity internal waves. The thermal convection has difficulty penetrating the upper stable layer. Its exchange is limited between the air in the upper layer and that in the lower layer in the valley, and it is adverse to the diffusion of pollutants in the valley.

Operation Performance of Central Solar Heating System with Seasonal Storage Water Tank in Harbin

This paper presented a preliminary research on the central solar heating system with seasonal storage(CSHSSS)used in cold climate in China.A mathematical model of the solar energy seasonal storage water tank used in the central solar heating system was firstly developed based on energy conservation.This was followed by the simulation of the CSHSSS used in a two-floor villa in Harbin,and analysis of the impacts on storage water temperature of tank volume,solar collector area,tank burial depth,insulation thickness around the tank,etc.The results show there is a relatively economical tank volume to optimize the system efficiency,which decreases with increasing tank volume at the constant collector area,and increases with increasing collector area at the constant tank volume.Furthermore,the insulation thickness has obvious effect on avoiding heat loss,while the tank burial depth doesn't.In addition,the relationship between the solar collector efficiency and storage water temperature is also obtained,it decreases quickly with increasing storing water temperature,and then increases slowly after starting space heating system.These may be helpful for relevant design and optimization in cold climates in China and all over the world.

A Laboratory Model for the Flow in Urban Street Canyons Induced by Bottom Heating

Water tank experiments are carried out to investigate the convection flow induced by bottom heating and the effects of the ambient wind on the flow in non-symmetrical urban street canyons based on the PIV (Particle Image Visualization) technique. Fluid experiments show that with calm ambient wind, the flows in the street canyon are completely driven by thermal force, and the convection can reach the upper atmosphere of the street canyon. Horizontal and vertical motions also appear above the roofs of the buildings. These are the conditions which favor the exchange of momentum and air mass between the street canyon and its environment. More than two vortices are induced by the convection, and the complex circulation pattern will vary with time in a wider street canyon. However, in a narrow street canyon, just one vortex appears. With a light ambient wind, the bottom heating and the associated convection result in just one main vortex. As the ambient wind speed increases, the vortex becomes more organized and its center shifts closer to the leeward building.

The Influence of Welding Parameters on Brittle Fracture of Liquefied Natural Gas Storage Tank Welded Joint

Many applications operate at sufficiently low temperature conditions where most structural steels become very brittle and, therefore, unsuitable for use in safety-critical structures. So the materials used in the vessels or storage tanks which keep the natural gas at liquefaction temperatures need to remain ductile and crack resistant with a high level of safety. The material also needs to have high strength in order to reduce the wall thickness of the container and it must permit welding without any risk of brittle fracture. 9% Ni steel plates are one of most common used materials in the LNG storage tank application. However, the welding procedure for 9% Ni steel plates requires high level of skills of welding that is strictly controlled welding parameter for balancing avoidance of cold and hot cracking and maintenance of high strength. Mechanical properties are important characteristics of the weldment that must confirm to the application feasibility as well as functional requirements of the welded joint. The only way to enhanced the mechanical properties of welded joint by controlling the parameters of using welding process. From the main variables of the arc welding process are the heat input and interpass temperature where the two variables control the thermal cycle of welding process. The experiment show that for thin test specimen with thickness ≤ 14 mm, the heat input range from 1.4 to 2 KJ/mm and controlling interpass temperature within 80°C give high tensile strength with improving the toughness properties of welded joint and reduce the probability of brittle fracture happened by increase the ductility and reduce the yield strength and increased the transition temperature.

泳池式低温供热堆用衰减筒的设计

衰减筒是池式低温供热堆的主要部件,其功能是保证堆芯出口的放射性冷却水在衰减筒内的滞留时间不低于100s,使短周期放射性核素在池内大量衰减,从而使一回路的放射性水平显著降低。根据整体布置要求,该衰减筒的筒体结构为不规则扇形结构,并在内部设置有分流板和孔板。其设计工作主要包括结构设计、冷却水衰减时间计算以及结构件的强度分析计算,并通过相关计算结果对设计进行优化。最终的设计结果表明,衰减筒的结构设计满足功能要求,冷却水在衰减筒内的衰减时间不低于100s,且强度分析计算满足设计要求。

动态热条件下原油罐储维温过程主要影响因素分析

掌握原油罐储维温过程主要影响因素,对原油库实现节能降耗目的起重要作用。在建立动态热条件下含蜡原油罐储维温过程三维理论模型的基础上,提出了加热盘管空间结构、周向效应对罐内对流传热的影响,划分了内、外因素影响区以及过渡区域;采用多元非线性回归的方法,建立不同季节边界位置主控影响因素模型,定量表征了罐边界油温与内、外因素之间的作用机制。结果表明:罐内大涡结构受无加热盘管区域局部湍涡影响,导致大涡结构向无盘管区域发生偏移。罐底低温区域受盘管周向效应影响较大,罐顶边界油品受内外因素影响大,形成最大厚度1.79 m的外界环境影响区;罐壁受保温层影响,只形成了内部维温热流影响区;冬季罐底形成了0.13 m的外界土壤影响区。

斜温层储热罐动态特性及影响因素分析

为分析斜温层储热罐的动态特性,建立了一维非稳态数学模型,研究了储热罐内斜温层的变化规律,工质质量流量、储热罐径高比和热流体温度对斜温层储热水罐性能的影响。结果表明:随着储热过程的进行,储热罐内斜温层厚度先增加后减小;工质质量流量越大,斜温层的移动速度越快,斜温层厚度越大,斜温层厚度可增加6.7%;储热罐径高比越大,斜温层的移动速度越慢,斜温层厚度越小,斜温层厚度可下降8.3%;热流体温度对斜温层运动特性没有影响,但热流体温度越高,斜温层厚度越大,斜温层厚度可增加7.7%。

池火灾环境下喷涂涂料液化石油气储罐热响应机理试验研究

以无机水性非膨胀型防火涂料为研究对象、以涂层厚度为主要影响因素,进行了池火灾环境下的液化石油气罐热响应试验,研究了喷涂防火涂料后池火灾环境中储罐的壁温响应、毁坏时间和失效模式。结果表明:无机水性非膨胀型防火涂层对于迟滞储罐在火灾作用下发生爆炸的时间效果显著。对于民用液化石油气储罐,充装水平相同时,涂层厚度2 cm的储罐在池火灾环境下的持续时间是裸罐的6.91倍,涂层厚度3 cm的储罐持续时间是涂层厚度2 cm储罐的1.20倍,涂层厚度4 cm的储罐持续时间是涂层厚度3 cm储罐的1.05倍。增加涂层厚度对迟滞储罐在池火灾环境下毁坏时间的效果逐渐降低,因此,建议储罐涂层厚度以3 cm为宜。研究结果对池火灾环境下储罐的安全防护应用和防火涂料研究具有一定的意义。

基于斜温层等效容积的大型蓄热罐动态特性分析

斜温层蓄热罐可以提高热电联产(combined heat and power,CHP)机组在供热期间的调峰能力,因此逐渐向大型化发展,但设计参数对蓄热罐的性能影响较大,且采用目前的性能评估方法效率较低。为此,建立大型蓄热罐的物理模型及数学模型,研究蓄热过程中斜温层的形成及变化过程,提出斜温层等效容积的概念,同时分析结构参数及运行参数对斜温层等效容积的影响。结果表明:形成稳定斜温层后,随着蓄热量的增加,斜温层厚度变化不大,采用斜温层等效容积可以更高效的评估蓄热罐的性能。比较不同工况下蓄热罐等效容积的相对变化量可知,不同影响因素对斜温层等效容积的影响从高到低排序依次为布水器布置、蓄热流量、高径比和冷热水温差。研究成果为大型蓄热罐的性能评估提供了一种新参考。

考虑热储灵活配置与热网水力热力特性的电热综合能源系统优化规划

电热综合能源系统优化规划可以定量决策电热耦合系统转型,在规划层面充分开发风电消纳路径。为此,提出一种考虑热储灵活配置与热网水力热力特性的电热综合能源系统优化规划方法。基于变流量-变温度策略构建热网模型,建立电力系统与灵活热源-热网-热储协同规划模型。提出预定参数型、功率平衡下最优投资型、变流量温度下最优投资型、时间系数离散型4种热储建模方法,实现热储灵活配置,采用二项式凸松弛和大M法将非线性规划模型转化为混合整数二阶锥规划模型求解。通过算例分析验证了所提方法可以有效提升规划方案的经济性,保证系统运行可行性,实现风电高比例消纳。

双层相变材料复合水箱蓄热特性研究

以双层相变材料复合水箱为研究对象,通过数值模拟和实验研究的方法,对该水箱的蓄热特性进行模拟分析与实验验证,对比分析单、双层相变材料复合水箱的热特性,探究双层相变材料位置对复合水箱蓄热特性的影响规律。研究结果表明,与单层相变材料复合水箱相比,双层相变材料复合水箱的热分层更好,蓄热能力得到提升,双层相变材料复合水箱较普通水箱的蓄热量提高9.7%。双层相变材料距离进出水口位置较远时,相变材料完成熔化的时间更接近,更有利于蓄热水箱的热分层。

新型跨季节分区储热水池储/释热性能研究

规模化跨季节储热技术能够有效解决新能源供热冬夏热量不平衡的难题。文中提出了一种将储热水体分格储存控制的新型跨季节分区储热水池,运用数值模拟方法对两种不同储/释热模式下储热水池的散热效果和全年热效率进行了计算和对比分析。研究结果表明:两种储/放热模式下,该储热水池都能够保持较高的全年热效率。模式2采用“后储先放”的策略,虽然放弃了各别分区的热效率,但保证了至少一半分区都在较高的热利用率下工作,储热水池整体全年的热效率能达到88.25%。模式1的储热水池全年的热效率为87.55%,虽略差于模式2,但能保证整个供暖季热水的温度的稳定。

准二级高温热泵循环的性能分析及实验研究

为解决低温余热资源过剩与高温用热需求紧缺之间的矛盾,设计了一套基于准二级压缩的高温热泵机组,理论分析循环流程并进行优化设计,采用闪蒸器与回热器组合提高机组性能,开展了机组的性能实验,以制热量、制热COP、[火用]效率、冷凝压力、排气温度为性能指标,在冷凝器出水温度为85~120℃,蒸发器进水温度为50、60、70℃工况下,对机组性能进行分析。实测机组性能与理论计算结果吻合,蒸发器进水温度为49.8℃,冷凝器出水温度为118.1℃,机组制热量可达916.3 k W,制热COP为2.51,[火用]效率为46.3%,机组冷凝压力为1.8 MPa,排气温度为137℃,符合机组安全运行的要求。

高校宿舍太阳能-空气源热泵复合热水系统设计与应用探讨

在当前积极倡导节能减排的政策要求下,可再生能源利用逐渐普及。以西安建筑科技大学学生宿舍太阳能-空气源热泵复合热水系统为例,阐述了复合热水系统的构成、工作原理,对太阳能集热系统、空气源热泵换热系统、热水供水系统等进行了设计计算,给出了集热器、热泵机组、集热水箱、供热水箱等主要设备的选型结果,提出了系统运行控制方案,并结合实际运行工况下的热性能数据,计算得到系统在不同季节的太阳能保证率、热泵能效比COP值,表明系统具有极大的节能性。

计及蓄热罐与管网虚拟储能热电联供系统的经济运行优化分析

本文建立计及蓄热罐与管网虚拟储能热电联供系统模型,探讨不同储能装置配置(如无储能装置、含虚拟储能、含蓄热罐、含蓄热罐与虚拟储能)下负荷场景、燃煤价格、管网长度对系统运行成本的影响。结果表明:含蓄热罐与虚拟储能的储能配置使得热电联供系统的运行成本大幅降低,且当热电负荷波动较大时,运行成本降幅更大,如工业负荷场景下降幅达26.12%;燃料价格上涨使得系统运行成本线性增加,但相比于无储能装置,含储能装置系统的运行成本仍然较低,经济性更好;由于管网储能容量限制以及管网热损的影响,存在一个最佳管长使得系统运行成本最小。

2×330 MW热电机组热电解耦深度调峰技术研究

通过对比热电解耦技术路线,确定对A热电厂2×330 MW热电机组配合应用电锅炉解耦技术和储热罐解耦技术。结合该机组实际运行经验,对电锅炉和蓄热水罐设备进行了最优选择,可以满足供热期的最大供热需求。经济性分析证明该方案具有良好的经济效益,为热电企业深度调峰工作提供了经验。

基于fluent的电加热沥青罐温度场分析

电加热沥青罐是未来沥青搅拌站主要配置设备之一,为沥青混凝土提供一定温度的沥青。为研究电加热管布局方式对沥青温升的影响,本文首先利用fluent软件对电加热沥青罐的温度场进行瞬态分析,仿真结果表明:对于卧式电加热沥青罐,罐体中部沥青温升最快,顶部温升次之,靠近罐体底部的沥青温度最低;进一步对沥青的流场分析,发现沥青流速越快,沥青温度越高;同时,沥青温度场和流场以罐体垂直中分面呈现对称分布的特点。最后对三种电加热管的布局方式进行了研究,研究结果表明:在加热初期,T型布局的电加热管能够显著提高沥青温升速度,相比较矩型和半圆型的布局方式,温度分布也更加均匀;在整个加热过程中,T型布局形式下罐内沥青温升最大,半圆型布局形式下罐内沥青温升变化较小,温度易于控制。

基于一起机舱火灾险情的船舶燃油加温管理策略探讨

船舶燃油管理涉及船舶的正常营运及效益,涉及防止环境污染和船舶安全。燃油加温及其操作对于船舶燃油的正常使用有着至关重要的影响。因船舶燃油加温系统私自改装或者操作不规范导致的火灾爆炸时有发生,造成巨大的财产损失和人员伤亡。本文针对一起由于船舶燃油加温系统引起的火灾险情,探讨船舶燃油加温管理策略。

光伏蓄能恒温库系统数值模拟分析

为进一步降低热泵系统冬季能耗,减少恒温库能源消耗情况,本文提出了一种新型光伏驱动蓄能型恒温库系统。基于TRNSYS仿真系统,构建了太阳能-热泵蓄能型热力耦合数学模型,对该恒温库系统进行数值模拟和理论分析。结果显示,在新型光伏驱动蓄能型恒温库系统运行下,库内温度可以稳定维持在-2.0~3.7℃保持24 h,在稳定运行过程中热泵系统运行效率保持在3.0~4.0,系统平均性能系数(COPa)可以达到1.9,系统运行功率在0~0.7 kW,系统24 h累计制热量达到了18.0 kW·h,日平均累计消耗市电仅6.8 kW·h。结果表明,该系统可以为节能型恒温库提供一种设计依据。