Effects of Different Ventilation Modes and Outlet Height on Nursery Piggery Environment

In order to study the effects of ventilation modes and outlet height on the airflow field of a nursery piggery,computational fluid dynamics (CFD) technology was used to simulate the wind speed and temperature of an experimental pig house in the cold northern region.This study was conducted with simulation and a comparative analysis of transverse ventilation,longitudinal ventilation and roof air intake modes.Furthermore,the effects of the air outlet height of 0.7,0.6 and 0.5 m with the roof air inlet mode on the environment in the pig house were studied.Field experiments verified the model of roof air intake model.The results showed inadequate ventilation in both the vertical and horizontal ventilation.However,the airfield gradients were less variable and more balanced when using the rooftop air intake mode.The variation of outlet height significantly affected nursery pig houses’ airflow velocity and temperature.Roof air inlet mode with an outlet height of 0.7 m was better than the other two.The normalized mean square error (NMSE) of air velocity and temperature was less than 0.01,and the simulation analysis could genuinely reflect the distribution of the airflow field in the nursery.

Experimental Study of Tunnel Fire with Natural Ventilation

The 1/15 reduced-scale experiments using Froude scaling were designed to study the effect on the smoke control efficiency for subway tunnel fires with natural ventilation mode.The propane gas fires with heat release rate 11.48 kW was used,which corresponds to the heat release rate 10 MW in the full-scale tunnel.The temperature distributions under the ceiling were measured by K-type thermocouples to investigate smoke movement,and the velocity of smoke in shafts was measured by hot-wire anemometer to obtain the smoke extract amount of ventilation shafts.The results show that the smoke temperature under the ceiling varies with the longitudinal different distance from fire source.The results also show that the smoke temperature distributions and the smoke control efficiency in tunnel vary with the space between ventilation shafts and vary with the area and the height of ventilation shaft.

Applied analysis of ventilation technology in residential buildings in Changjiang river valley

Making the use of ventilation technology may decrease building energy consumption,improve indoor thermal environment,and ameliorate indoor air quality. Combining with the meteorological characteristics in the Changjiang river valley and focusing on Chongqing,this work makes an applied analysis of the feasibility of intermittent mechanical ventilation. By comparison of various ventilation modes,it gives a summary of the suitable ventilation ways for different weather conditions with the combination of testing data and experimental data.

Numerical simulation and analysis for indoor air quality in different ventilation

Indoor air environment includes indoor thermal environment and air quality, and a reasonable ventilation provides guarantee for a good indoor environment. A numerical study of the indoor environment in different ventilation is presented in this paper. The External Energy Saving Lab of the WenYuan Building was selected for this purpose, and its indoor air quality and thermal performance in the typical summer climate were simulated. For the numerical simulation, the techniques of Fluent Air-pak was adopted to establish the physical and numerical model of lab. A attention is given to the velocity field and the distribution of pollutant concentration, followed by a discussion of two ventilation modes (displacement ventilation and up-in and up-out ventilation). By comparison, it is found that the Displacement ventilation in improving indoor air quality is obviously superior to the traditional up-in and up-out ventilation.

Carbon dioxide levels and ventilation for running vehicle

Factors contributing to ventilation quantity of the vehicle are ventilation modes, cabin characteristics and vehicle speeds. CO2 levels were investigated under different speeds and ventilation modes. Four modes were selected： A： vent closed and fan shut, B： vent closed and fan started, C： vent opened and fan shut, D： vent opened and fan started. In vent closed modes, CO2 levels reached several thousands of ppm in few minutes at any speeds. For mode C, CO2 levels exceeded the guideline at low speeds 50 km/h, while it reduced below one at higher speeds 80 km/h. Fan has no significant impact on ventilation during vent closed. The ventilation efficiency in each mode increased with the speed raising. To determine the ventilation rate of running vehicle, the experiment was implemented by using CO2 emitted from driver and passengers as tracer gas. Ventilation rate for the different modes and speeds were calculated.

Impact of indoor air volume on thermal performance in social housing with mixed mode ventilation in three different climates

There are prototypes of social housing massively built in contrasting climatic conditions,generating thermal comfort needs that are difficult to satisfy by the users themselves.Variation of indoor air volume in living spaces where the use of air conditioning and natural ventilation strategies provides elements to improve thermal comfort conditions.This research shows the thermal performance located in a representative social housing according to Mexico’s National Housing Commission.Operative temperature results from a benchmark case were compared to six Virtual Evaluation Models,using the Dynamic Thermal Simulation tool Design Builder®from the perspective of probability.The main objective was to determine the minimum use of active systems with different indoor air volumes and improve comfort conditions to promote sustainable living in social housing.The analysis was conducted under an adaptive comfort range according to three different climate conditions in Mexico adopting a Numerical Theoretical Method.The main findings can be divided into two parts:a)the impact of the indoor air volume on thermal performance was evidenced in a proportion of time in three representative climates of the central region of Mexico,and b)no relationship was found between indoor air volume and thermal comfort in sub-humid cold climate;in sub-humid temperate climate,the same number of comfort hours was found in two different models,and in sub-humid warm climate,an inversely proportional relationship was found between indoor air volume and the comfort hours.This findings implies a greater knowledge relative to what we know about sub-humid cold,temperate and warm climates.

Study on the optimal operation mode of ventilation system during metro double-island platform fire

Large metro transfer stations have been widely constructed in China,among which the double-island station faces the serious fire safety issues owing to its large passenger flow.In this paper,simulation cases were carried out to investigate the effectiveness of different ventilation modes by jointly operating tunnel ventilation fan(TVF)and platform screen doors(PSD)under two typical fire scenarios in the platform.The numerical model was established by Fire Dynamics Simulator software and verified via reduced-scale model experiments.The results indicate that the TVF mode of supplying at the end near fire and exhausting at the other end is superior to that of exhausting at both ends.Besides,activating more PSD and TVF on the both sides of platform will restrict smoke in one end to the greater extent.During a fire in the middle of the platform,opening all PSD near tunnel-2 and TVF in tunnel-2 and tunnel-3 is the most appropriate mode.While during a fire at the left end of the platform,activating all PSD and TVF on both sides is the optimal operation mode.The conclusions can provide guidance for smoke control design and on-site emergency ventilation operation in double-island platform fire.

Predicting indoor particle dispersion under dynamic ventilation modes with high-order Markov chain model

Mechanical and natural ventilations are effective measures to remove indoor airborne contaminants,thereby creating improved indoor air quality(IAQ).Among various simulation techniques,Markov chain model is a relatively new and efficient method in predicting indoor airborne pollutants.The existing Markov chain model(for indoor airborne pollutants)is basically assumed as first-order,which however is difficult to deal with airborne particles with non-negligible inertial.In this study,a novel weight-factor-based high-order(second-order and third-order)Markov chain model is developed to simulate particle dispersion and deposition indoors under fixed and dynamic ventilation modes.Flow fields under various ventilation modes are solved by computational fluid dynamics(CFD)tools in advance,and then the basic first-order Markov chain model is implemented and validated by both simulation results and experimental data from literature.Furthermore,different groups of weight factors are tested to estimate appropriate weight factors for both second-order and third-order Markov chain models.Finally,the calculation process is properly designed and controlled,so that the proposed high-order(second-order)Markov chain model can be used to perform particle-phase simulation under consecutively changed ventilation modes.Results indicate that the proposed second-order model does well in predicting particle dispersion and deposition under fixed ventilation mode as well as consecutively changed ventilation modes.Compared with traditional first-order Markov chain model,the proposed high-order model performs with more reasonable accuracy but without significant computing cost increment.The most suitable weight factors of the simulation case in this study are found to be(λ_(1)=0.7,λ_(2)=0.3,λ_(3)=0)for second-order Markov chain model,and(λ_(1)=0.8,λ_(2)=0.1,λ_(3)=0.1)for third-order Markov chain model in terms of reducing errors in particle deposition and escape prediction.With the improvements of the efficiency of state transfer matrix construction and flow field data acquisition/processing,the proposed high-order Markov chain model is expected to provide an alternative choice for fast prediction of indoor airborne particulate(as well as gaseous)pollutants under transient flows.

Subtropical Mode Water in the Northwestern Pacific

Based on the in situ XBT and other data sets, by analyzing the seasonal cycle of the mixed layer depth (MLD) and using the conservative potential vorticity (PV) as a tool, a clear description of the formation process of the North Pacific Subtropical Mode Water (NPSTMW) is presented for explaining the well known 'Stommel Demon'. The forming of NPSTMW reflects well the ventilation process of the isotherms of the permanent thermocline. The formation process can be divided into the 'ventilation' phase and the 'formation' phase. In the first phase (October-March), with large heat losses at the sea surface from October, the mixed layer deepens and correspondingly, the water mass with low PV emerges and sinks. After continual cooling from October to March, the mixed layer reaches its maximum value ( >300 m) in March. Then, in the second phase (April-June), the mixed layer shoals rapidly from April, a large part of the low PV water mass is sheltered from further air-sea interaction by the emerging seasonal thermocline, and thus forms new NPSTMW. Further analysis indicates that the formation region of warm NPSTMW (17-18℃) is limited between 140°-150°E, while the relatively cold NPSTMW (16-17℃) originates in a wider longitude range (140°-170°E).Climate features of NPSTMW are presented with the use of climatological Levitus (1994 a, b) dataset. It is shown that NPSTMW lies in the region of (130°-170°E, 22°-34°N) with core temperature ranging from about 16-19℃ and potential density around 25-25.8σθ NPSTMW has a three-dimensional structure lying below the seasonal thermocline (about 100 m deep) and reaches almost to 350m depths.

冬季不同最小通风量模式对肉种鸡育雏育成期生长性能及环控能耗的影响

为研究冬季不同最小通风量模式对肉种鸡育雏育成期舍内环境、生长性能以及环控能耗的影响,试验测试了间歇式通风和连续式通风两种不同的最小通风量通风控制模式,分别比较了两种模式下鸡舍内主要环境质量参数、环控能耗、体重均匀度和抗体效价。结果显示:第一周,连续通风温度高于间歇通风(P>0.05),相对湿度显著低于间歇通风(P<0.05),二氧化碳浓度显著高于间歇通风模式(P<0.05),第2~10周,连续通风温度极显著高于间歇通风(P<0.01),相对湿度极显著低于间歇通风(P<0.01),二氧化碳浓度极显著高于间歇通风模式(P<0.01),同时连续通风鸡舍内环境参数波动度小于间歇通风;试验期间连续通风环控总能耗(7036.01 kW·h)低于间歇通风(7633.02 kW·h),并且连续通风种鸡体重均匀度优于间歇通风;H5N1亚型禽流感病毒抗体效价显著高于间歇通风(P<0.05),H7N9亚型禽流感病毒抗体效价极显著高于间歇通风(P<0.01)。研究表明,冬季肉种鸡育雏育成期采用连续通风的最小通风量模式对比间歇通风的最小通风量模式,可以获得更加稳定的舍内环境,雏鸡生长性能以及免疫效果更优,且能源消耗更少。

基于信息化平台的急诊危重症患者护理核查单的设计及应用

目的探讨基于信息化平台的急诊危重症患者护理核查单的设计及应用效果。方法基于院内信息化平台,设计急诊危重症患者护理核查单。采用前瞻性类实验性研究方法,观察危重症患者护理核查单应用前后护理交接班的遗漏率、临床护理效果和护理质量。结果应用急诊危重症患者护理核查单后,护士在管路、通气方式、留置针、用药、皮肤和约束方面的交接班遗漏率显著低于应用前(均P<0.05);临床护理效果和护理质量较核查单应用前显著提升(均P<0.05)。结论基于信息化平台的急诊危重症患者护理核查单的应用可减少护士交接班的遗漏内容,提高护理记录准确性,并缩短书写时长,提高护理质量。

电阻抗断层成像技术的心肺信号降维集合经验模态分解方法研究

心脏射血与肺通气活动信息的实时获取具有重要临床意义。本研究提出了一种基于胸部电阻抗断层成像(EIT)的心肺信号降维集合经验模态分解方法,以同时分离胸部EIT数据中的心脏射血和肺通气活动信号。招募9名志愿者进行了EIT胸部数据采集。首先,根据屏息状态下胸部EIT数据中心脏活动信号的强弱对测量通道分类;随后,使用集合经验模态分解方法对自主呼吸状态下的EIT数据进行分解,并根据频谱特性对分解出的各分量归类,以得到肺通气EIT信号;然后,结合带通滤波方法,同时依据前述通道分类对心脏活动信号降维,得到心脏活动EIT信号;最后,重构得到通气相和心搏相EIT图像序列。结果表明,该方法可在通气相图像的肺区能够获得最高的肺通气功率谱峰(52.71±1.39)dB,在心搏相图像的心脏区域能够获得最高的心脏活动功率谱峰(43.05±3.26)dB,表明保留的通气信息和心脏活动信息非常丰富,同时在通气相图像心脏区域获得了最低心脏活动相关功率谱峰(10.02±2.65)dB,表明心脏活动的抑制效果更佳,相较于参考方法均有显著性差异(P<0.05)。研究表明,该方法可以有效分离肺通气与心脏活动相关信号,分别保留各自活动信息并抑制心脏对肺区成像的影响,同时实现对干扰信号的有效抑制,为临床上提供更加准确的治疗策略指导奠定基础。

扁平大空间船舶火灾烟气控制试验研究

为有效控制扁平大空间船舶火灾烟气蔓延,研究大尺度火灾过程中的油池质量损失速率、舱室温度分布、隔热效率和烟气控制效果。利用尺寸为30 m×24 m×2.3 m的模拟舱,在0.35、0.55和0.70 m等3种不同挡烟垂壁高度和机械通风条件下开展试验。结果表明:挡烟垂壁高度增加,油池质量损失速率峰值减小;挡烟垂壁高度对舱室上层烟气温度的影响比对下层气体温度的影响更明显,1.4 m以上空间温度峰值明显下降,而1.4 m以下空间温度峰值无明显变化。顶棚平均温度和隔热效率随挡烟垂壁高度增加而下降。随挡烟垂壁高度增加,火源区与非火源区同时控烟模式隔热效率从28.2%提升至50.8%,火源区单独控烟模式隔热效率从29.4%提升至54.7%。

隧道纵向风及列车侧门开启方式对车厢内火灾温度场影响研究

为了探究隧道纵向通风、列车侧门开启方式对车厢内部火灾烟气温度分布的影响规律,建立1∶15缩尺寸“车-隧”耦合试验模型,以及着火车厢侧门双侧开启时“车-隧”耦合区间车厢内部考虑无量纲纵向风速、无量纲侧门开口因子、无量纲火源热释放速率的无量纲烟气回流长度分段函数关系式。定性分析车厢顶部烟气温度分布规律,定量分析车厢内烟气回流长度数据,从而揭示烟气回流长度随纵向风速、侧门开启方式和火源热释放速率变化的规律。研究结果表明:不同纵向风速下,火源上游烟气温度分布在贯通门位置处发生明显降低。不同侧门开启方式下,着火车厢侧门双侧开启工况的火源上游温度衰减速率大于侧门单侧开启的工况;随着车厢每侧侧门开启数量增加,着火车厢侧门单侧开启工况与双侧开启工况的火源上游温度衰减速率差距随之增大。着火车厢、非着火车厢侧门均单侧开启时,烟气回流长度变化规律受贯通门停滞影响较大,当火源热释放速率增大至5.7 kW,纵向风速大于0.8 m/s后,烟气回流长度不再随纵向风速的增大而变化。着火车厢侧门双侧开启、非着火车厢侧门单侧开启时,烟气回流长度符合加速衰减区、停滞区、缓慢衰减区变化规律。研究结果可为提升列车火灾烟气防治效果,加强区间隧道烟气控制及运营安全提供经验和理论参考。

基于室内非均匀环境营造的新型通风模式下人员热舒适性及系统节能潜力

为解决现有通风空调系统无法根据占用区域实现按需供冷造成的热不舒适及能源浪费问题,本研究根据人员占用区域需求实时切换气流模式组合及冷量供给,提出了一种新型通风模式,旨在利用多种气流模式的最优组合控制特定需求场景。采用数值模拟的方法探究了不同占用区域情况下新型通风模式的人员热舒适性和系统的节能潜力,并与混合通风模式和层式通风模式进行了对比。结果表明:新型通风模式在气流组织上具有明显优势;新型通风模式较混合通风模式和层式通风模式具有更高的热舒适性,空气分布特性指数最大;新型通风模式局部冷量利用系数最小,冷量有效利用率最高,所需供冷量最小,因此新型通风模式的节能潜力最大。

不同通风方式日光温室微环境模拟与作物蒸腾研究

日光温室后墙蓄热降低了通风降温效率,高温会刺激植物水分蒸腾,降低水资源利用率。本文以北京市通州区日光温室为研究对象,在原有的上、下通风口基础上,增设后墙通风口。基于DO辐射模型、组分输运模型和多孔介质模型建立了日光温室的计算流体力学(CFD)模型,探究了不同通风方式下温室微环境状况,并结合作物蒸腾模型分析获得了作物蒸腾特征。结果表明,气温变化会直接影响作物蒸腾强度,两者空间分布特征一致。中午温室高温,开启后墙、下通风口,较原来开启上、下通风口,气流走向相似,因减少部分蓄热墙体,降温效率提高5.7%,蒸腾量下降0.020 mm/h,开启后墙、上、下通风口,蒸腾量较原来下降0.005 mm/h。开启后墙、上通风口,由于两通风口靠近一侧且距离作物较远,只能形成北侧局部降温,降温效率下降10.3%,除湿效率较原来提高5.7%,蒸腾量升高0.035 mm/h。此外,在通风口组合中,将靠下的通风口设置在迎风方向,可减少外界来风能量、动量损失,以提高通风降温效率。研究结果可为日光温室微环境调节提供参考。

不同通风方式下“110工法”采空区自燃“三带”数值模拟研究

为探究不同通风方式下“110工法”采空区自燃“三带”分布特征,以顾北矿1532(1)工作面“两进一回”通风方式为工程背景,基于风流控制方程、浓度组分方程和能量方程等,利用Fluent数值模拟方法建立煤自然发火多物理场耦合数值模型、工作面实时动态推进模型,模拟了3种通风方式下“110工法”采空区自燃“三带”分布特征。结果表明:随着工作面不断推进,在通风方式1(机巷侧和沿空留巷进风,回风巷回风)和通风方式2(机巷侧和回风巷进风,沿空留巷回风)条件下,采空区氧化自燃带均匀分布在运输巷侧、工作面中部和留巷侧,其氧气体积分数分布形状相差不大,采空区温度首先升高,开采约50 d后,最高温度出现在运输巷侧深部,且该位置温度不随工作面继续推进而升高;在通风方式3(沿空留巷和回风巷进风,机巷侧回风)条件下,采空区留巷侧氧化自燃带变宽2~4倍,工作面中部和运输巷侧明显变窄,采空区运输巷侧氧气体积分数较低,留巷侧氧气体积分数较高,漏风量明显增大。采空区高温位置主要出现在1532(1)工作面始采线留巷侧,且当工作面开采50 d后,此处采空区温度最高。综上所述并结合现场实际情况,对氧化自燃带宽度及位置进行分析,最终确定通风方式3更有利于防止煤自燃的发生,对矿井煤自燃的预防提供了理论指导。

无创通气AVAPS模式对慢性阻塞性肺疾病伴Ⅱ型呼吸衰竭患者的治疗价值

目的分析无创机械通气平均容积保证压力支持(AVAPS)模式对慢性阻塞性肺疾病伴Ⅱ型呼吸衰竭患者的治疗价值。方法选取2021年1月~2022年12月在北京市房山区良乡医院呼吸科住院的82例慢性阻塞性肺疾病伴Ⅱ型呼吸衰竭患者,随机数表法分为对照组(n=42)和观察组(n=40)。对照组采用双水平正压通气(BiPAP)S T模式+内科治疗方案,观察组采用AVAPS模式(S T+VT目标)+内科治疗方案。观察两组患者血气指标变化、通气效果和呼吸机相关并发症发生率。结果对照组患者呼吸机不耐受给予内科治疗5例、治疗失败气管插管者8例;观察组40例,呼吸机不耐受2例、治疗失败气管插管者3例,并且插管后进呼吸重症监护室(RICU)治疗,无1人死亡,其余患者全都好转出院。机械通气治疗后,两组患者pH值均上升,二氧化碳分压(PaCO_(2))降低,与机械通气前比较,差异有统计学意义(P<0.05);观察组机械通气不同时刻pH值的上升与PaCO_(2)降低优于对照组,但差异无统计学意义(P>0.05)。观察组平均潮气量(VT)(520.00±50.00)ml、每分钟静息通气量(VE)(9.77±1.30)L min高于对照组,呼吸频率(RR)(16.00±1.00)次min、平均漏气量(Lleak)(18.00±6.00)L min明显低于对照组,人均呼吸机吸氧时间日(TA)(7.35±2.44)h和人均带机时间(TB)(52.89±9.85)h高于对照组,差异有统计学意义(t=9.979、6.999、11.366、9.347、7.944、11.672,P<0.05)。观察组患者机械通气治疗依从性90.0%高于对照组71.43%,差异有统计学意义(χ^(2)=4.499,P<0.05)。观察组气管插管率7.50%、面部压伤7.50%、胃肠胀气5.00%、吸入性肺炎2.50%和眼结膜炎2.50%均低于对照组,差异有统计学意义(P<0.05)。结论无创机械通气平均容积保证压力支持AVAPS模式减少呼吸肌做功,人机协调性好,较BiPAP显示出一定的优越性。

基于失效模式和效果分析模式的督导式预警性护理预防成人心脏术后通气患者呼吸机相关性肺炎发生的效果

目的 探讨基于失效模式和效果分析(FMEA)模式的督导式预警性护理对成人心脏术后通气患者呼吸机相关性肺炎(VAP)发生的预防效果。方法 选取2020年11月至2022年11月新疆医科大学第一附属医院重症医学二科心脏术后接受通气治疗的84例成人患者为研究对象,根据随机数字表法将患者分为对照组与观察组,各47例。对照组采用常规护理方法,观察组在此基础上采用基于FMEA模式的督导式预警性护理干预,两组均护理15 d。比较两组护理期间VAP发生情况、机械通气治疗时间、住院时间及护理前后血气分析指标变化情况。结果 观察组VAP发生率低于对照组(P<0.05);观察组住院时间、机械通气治疗时间短于对照组(P<0.05);护理后,两组动脉血氧分压水平高于治疗前,且观察组高于对照组(P<0.05);护理后,两组动脉血二氧化碳分压水平均低于治疗前,且观察组低于对照组(P<0.05)。结论 应用基于FMEA模式的督导式预警性护理可有效预防成人心脏术后通气患者VAP的发生,缩短机械通气治疗时间及住院时间,改善动脉血气。

3S2E管理模式在重症机械通气患者中的应用

目的探讨3S2E管理模式在重症机械通气患者中的应用效果。方法采取随机数字表法将2020年5月至2023年2月郑州大学第一附属医院收治的103例神经外科重症机械通气患者分为研究组(51例)与对照组(52例)。对照组接受常规护理,研究组在对照组基础上接受3S2E管理模式干预。比较两组干预前后血气指标[动脉血二氧化碳分压(PaCO_(2))、动脉血氧分压(PaO_(2))、碱剩余水平]、生命质量综合评定问卷评分、机械通气、住院时间及护理满意度。结果干预后两组患者PaO_(2)、碱剩余水平均升高,且研究组患者PaO_(2)、碱剩余水平更高(P<0.05);干预后两组患者PaCO_(2)水平降低,且研究组PaCO_(2)水平更低(P<0.05)。研究组机械通气时间、住院时长均低于对照组(P<0.05)。干预后两组患者生命质量评分均升高,且干预后研究组生命质量评分更高(P<0.05)。研究组护理满意度高于对照组(96.08%vs 84.62%,P<0.05)。结论3S2E管理模式应用于重症机械通气患者中可有效缩短机械通气时间与住院时间,改善患者血气指标,提高生命质量。