变流量水系统中水力平衡问题的探讨

分别从静态水力平衡、动态水力平衡角度分析了静态水力平衡阀、自力式流量控制阀、自力式压差控制阀与电动调节阀组合使用的特性,认为自力式流量控制阀与电动调节阀组合不适合应用在变流量水系统中.     

实施计量技术后供热系统的控制决策

实施计量技术后,供热系统的运行工况发生了很大变化,其运行调节与控制亦相应随之变化.在实施计量技术的过程中,供热系统要分别安装恒温阀、通断阀、智能平衡阀、电动调节阀和变频调速循环泵.本文主要探讨在这些设备的共同作用下,如何对系统进行变压变流量以及变温变流量调节.     

阀权度对散热器恒温控制阀调节性能的影响

以散热器热力调节特性、恒温阀流量调节特性和恒温阀与散热器的组合热力特性为基础,确定了恒温阀在不同阀权度下能够对散热器散热量进行比例调节的范围。根据天津市供暖实际负荷变化特性,在3%不保证率条件下,确定天津市保证恒温阀能够实现良好调控的允许最小阀权度值为0.15。     

蒸汽锅炉给水电动调节阀的应用

在蒸汽锅炉给水系统中,变流量给水系统极为普遍,然而实际工程中,变流量空调系统经常出现监而不控、控而不优的情况,这与控制系统的调节阀有着直接的联系。调节阀作为系统的一个控制中的执行器,在流量调解中起着调节和控制流量的作用。调节阀作为系统一个控制环节,它选择的正确与否直接关系到变流量给水系统是否能够正常运行。在给水系统中,调节阀流量特性及阀权度的选取十分重要,在应用时应充分了解阀门特性及管路阻力分布情况,使调节阀的工作特性满足系统运行要求,从而达到节能降耗,安全运行的目的。在本文中,通过实验实现20%以上的节电收益,增大阀门调节特性,使系统更加经济安全运行。     

建筑设备工程基础(2)——调节阀·调节风阀

1调节阀调节阀在空气调节自动控制系统中占有很重要的位置,它的选择要考虑到多个因素,而且直接影响到控制效果。1.1调节阀工作原理在空调水系统中的调节阀,根据控制信号的要求而改变其开度的大小来调节流量。从流体力学的观点看,调节阀在水系统中是一个局部阻力可以变化的节流元件,根据伯努力方程,对不可压缩流体,调节阀的流量方程为:(1)式中:ξ——调节阀阻力系数;P——阀前压力;1P——阀后压力;2F——调节阀接管截面积;ρ——流体密度。由(1)式可见,当F一定,(P-P)不变时,12流量Q随阻力系数ξ的变化而发生变化。1.2调节阀的分类在空调系…     

正确选择流量调节阀是实现供热系统流量平衡的关键

供热系统出现水力失调、冷热不均现象，其中一个重要原因是流量调节阀选择不当。本文就各种流量调节阀的调节特性、阀权度和流量调节阀的正确选择、应用进行了阐述并提出了相关建议。     

散热器恒温阀控制有效性的模拟分析研究

本文以实际建筑及安装恒温阀的供热系统为研究对象,建立了热力水力综合仿真模型,进行了多工况模拟,分析了恒温阀对不同原因(流量分配不均、散热器面积过大和供水温度过高)引起的过热现象的改善程度,进而探讨了适合新型供热系统的运行调节方式。主要结论为:当恒温阀设置档位为2~3时,恒温阀改善过热的有效性与过热原因及过热程度有关;对流量偏大引起的过热损失的控制有效性小于0.6,对供水温度偏高及散热器面积偏大引起的过热损失的控制有效性约为0.8;过热损失越大,应用恒温阀后的节能潜力越大,但仍有约20%~40%的过热损失需要从改善不合理的运行调节和设计角度去解决。基于上述分析,本文提出水泵定压差变频运行、并以系统流量变化为反馈量分日调节供水温度的策略,从而适应系统负荷变化,并可将系统流量控制在较合理范围内。     

在楼宇自控系统设计中如何选择最佳的电动调节阀口径

本文主要介绍理想的流量特性曲线,阀权度的最佳值,结合实际工程案例介绍电动调节阀的口径尺寸计算方法,探讨了按照经验选择电动调节阀口径的弊端。     

基于调节阀实际特性的空调机组优化控制

通过实测获得一空调机组调节阀实际的开度-相对流量特性.利用所建立的空调机组仿真平台,模拟研究了按照调节阀理想工作曲线制定的控制参数对实际调节阀的控制效果.结果显示,此调节阀在实际运行时单位开度变化引起的流量变化较理想流量特性下大,导致调节阀开度超调及房间温度波动,控制效果与预期理想效果出现偏差.基于调节阀实际流量特性,...     

变流量系统二次管网水力平衡装置选用探析

分析了变流量系统中静态平衡阀和自力式压差控制阀对恒温阀实际承受压降的影响,指出了静态平衡阀和自力式压差控制阀在减轻恒温阀调节过程承受压差方面的局限。结合阀门特性参数,提出了管网设计中静态平衡阀和自力式压差控制阀的选用原则,为供热系统设计和改造提供参考。     

轿车空调制冷剂流量控制的研究

采用电子膨胀阀代替热力膨胀阀作为轿车空调系统的节流机构,通过模糊自调整PID控制调节电子膨胀阀的开度,保证供给蒸发器合适的制冷剂流量.实验表明模糊自调整PID控制方法在变工况的情况下,可以供给蒸发器合适的制冷剂流量.     

Research on the control laws of the electronic expansion valve for an air source heat pump water heater

Compared to the conventional air conditioner, the air source heat pump water heater (ASHPWH) possesses wider operating ranges and more dramatic changes in working conditions. Conversely, traditional throttle devices, such as the thermostatic expansion valve (TEV) and capillary tube, are restricted by narrow regulating ranges in refrigerant mass flow rate and lagging response to the superheat. This article incorporates a novel dual-fuzzy-controller to regulate the electronic expansion valve (EEV) specialized for the ASHPWH system. The study analyzes the effects of the EEV initial opening and the target superheat on the performance of the ASHPWH. Moreover, this research proposes a fuzzy control method of selecting the initial opening and the target superheat on the basis of the ambient temperature and water temperature, and employs superheat error (e) and the derivation of superheat error (ec) as the input variables of the fuzzy controller B to regulate the opening of the EEV during steady running process. To improve self-adaptability of the fuzzy controller, a rule modifier and a gain scheduler are introduced. In order to quantitatively reflect the difference in the performance between the TEV-controlled system and EEV-controlled one, experimental comparison between the EEV and the TEV is presented. Results demonstrate that both the stability and efficiency of the ASHPWH can be improved significantly by the EEV.     

室内温度随温控阀调节的变化

根据供暖房间热平衡方程,建立室内温度随温控阀调节变化的数学模型。以某居住建筑为研究对象,对室内温度随温控阀调节的变化进行模拟分析。     

自力式调节阀适用条件分析

介绍自力式流量控制阀和自力式压盖控制阀的结构与工作原理，分析其适用条件和与电动阀、平衡阀的配合使用问题。     

A novel on-off TRV adjustment model and simulation of its thermal dynamic performance

Field test results show that about 15% to 40% of building heat loss in China is attributable to poor heating systems regulation. The current method for addressing this problem is to install thermostatic radiator valves (TRVs) to the ends of radiators, a method adapted from northern Europe. However, this method has resulted in poor performance from delayed controlling action due to thermal inertia as well as insufficient system control accuracy. This is further compounded by incorrect operation by system users and a lack of financial incentives to regulate the system if users are not billed for their heat consumption. We present a new method for simultaneously heat controlling and metering. The core challenge is to design a control strategy that will maintain the room’s temperature. Thus, we established dynamic heat transfer models for water flow, the radiator and the building so as to obtain the optimal heating strategy. We also simulated the indoor thermal dynamic performance of the heating system with different heating loads, supply water temperatures, and supply water flow rates using three methods: a continuously changing flow rate (Method 1), a step-change flow rate based on temperature deviation (Method 2) and an intelligent step-change flow rate (Method 3) which predicts the duty cycle of the valve in the proceeding period and controls the valve’s on-time. The simulation results indicate the performance of these three methods. For Method 1, as the room temperature is above the set point, the flow rate can be automatically reduced to a level which is proportional to the room temperature deviation. Further, the scale factor of the flow rate is designed according to the +2°C deviation, so it is accepted that the room temperature is higher than the set point by +2°C using this method. However, this low control precision is unsatisfactory. The mean temperature is higher than the set point and greatly affected by the heating load and supply water’s temperature and flow rate. For Method 2, the controlling action is delayed by thermal inertia, the room temperature fluctuates between the highest and lowest levels, and the temperature deviation can be greater than the set value. For Method 3, both the simulation and field test results showed that room temperature deviation was maintained within a ±0.5°C range under the various conditions. This method appears relatively robust and adaptable, and was the best control strategy of the three methods.     

以调节阀为执行机构的神经网络投矾控制系统

重点介绍了在自来水生产中,在重力自流投矾条件下,投矾流量的自动化控制技术和实施方案,简要介绍了投矾全自动化运行系统的组成原理和采用调节阀控制投矾流量的特点,并对调节阀与计量泵的性能进行比较,为自来水厂的投矾控制技术提供了一个可行的新方案。     

户内水平单管跨越式系统的设计计算

通过对能够实现分室控温,分户计量的户内水平单管跨越式系统的散热器数量的设计计算及分析,认为采用自力式两 恒温阀加跨越管的做法不妥,而应采用每组散热器前设置手动三通调节阀或自力式三通恒温阀的单管跨越式系统.     

热回收地源热泵机组的水温控制

提出了变流量间接控制方案,即通过调节地源侧水流量间接控制热回收热水温度,以保证冷水和热回收热水温度恒定的方法。给出了控制原理和控制方案。结合杭州某办公楼示范工程,验证了该系统的控制精度,结果表明该系统控制效果良好。     

三通恒温混水阀在地暖系统中的应用

介绍了三通恒温混水阀的基本原理与性能特点,探讨了其在地板辐射采暖系统中的实际应用,分析了带三通恒温混水阀型地暖系统的技术优势,以推广三通恒温混水阀的应用。