基于Android操作系统的智能手机下湿空气参数计算

暖通空调设计人员需经常通过查询湿空气焓湿图确定状态参数,鉴于Android智能手机的普及和查图工作的繁琐与耗时,本文基于Android Studio编程工具,采用Java编程语言编写了湿空气状态参数的计算应用程序,实现了标准大气压下湿空气焓湿图上状态参数的无缝嵌入。该应用将极大地方便暖通设计人员随时随地的快速获取湿空气的相关状态参数,具有较高的实用价值。     

湿空气状态参数关系式的改进

作制冷空调方案常用到湿空气的焓湿图,但查图作图方法误差较大,此工作完全可由湿空气状态参数关系式编程计算替代。对空调系统和设备进行数学模拟,常需根据湿空气各状态参数间的关系式编制计算程序。这些关系式的改进有助于计算程序的改良。     

基于手机平台下的湿空气状态参数计算

鉴于暖通空调设计人员在设计时经常要翻看湿空气焓--湿图来查找相应参数的繁琐和目前手机已经普遍使用的现实情况,本文运用J2ME技术编制程序,将常用的标准大气压下的湿空气焓.湿图上的一系列状态参数嵌入手机当中计算,此项技术可以极大地方便暖通空调设计和研究人员快速地获取所需要的湿空气状态参数,具有较高的实用价值.     

湿空气热力性质数值计算分析

本文对国内外现行的湿空气热力性质的计算公式和数值计算方法进行了分析,对其中存在的一些问题进行了讨论。在此基础上,提出了一组可用于空调和制冷工程中各种类型的湿空气热力性质数值计算的公式和方法。     

湿空气绝热节流系数计算及讨论

基于修正的PR方程(MPR方程)与压缩因子方程,将焦耳-汤姆孙系数的计算转化为压缩因子在等压条件下对温度的偏导数的计算,提出了一种计算湿空气绝热节流系数的方法.对该方法进行了验证,首先计算了饱和湿空气的压缩因子,与相关文献的数据进行了比较；其次计算了不同压力、不同温度下氧气的焦耳-汤姆孙系数,与基于实验数据的经验公式的计算值进行了比较,结果均表明此方法具有较高精度.最后分析了温度、压力及含湿量对湿空气绝热节流系数的影响,并比较了MPR方程和PR方程的计算结果.     

利用神经网络预测湿空气的状态参数

由于湿空气的状态参数间存在着复杂的非线性关系，采用传统的方法确定湿空气的状态参数既不便于软件实现，也不能适应空调实时控制的需要。为了解决这一问题，本文根据空调设计过程的特点，利用人工神经网络方法，建立了两个湿空气状态参数的神经网络预测模型，实现了湿空气状态参数的智能化预测，这一方法在空调系统实时控制过程中有良好的应用前景。     

计算肋形板自振频率的能量法

应用能量原理导出肋形板自振频率计算式,针对工程中肋形板不同的边界约束状况,给出振型试函数各种形式,指出该方法既适用于不同纵、横梁布置的板,也适用于板边各种支承情况,与有限单元法相比,无需计算机程序,计算过程简单易行。     

汽车空调冷负荷计算研究

从汽车的动态传热实际过程出发，应用冷负荷传送函数计算方法，对汽车空调的冷负荷的各项组成进行分析计算并编制出计算机程序，通过实例计算得出的结果与实测结果基本相符。     

考虑位移影响的土压力非线性计算

极限土压力理论计算结果与工程实测数据偏差较大。为解决该问题,以朗肯土压力理论为出发点,借鉴双参数法思想,提出了一种考虑位移影响且同时适用于黏土和砂土的主、被动土压力计算方法,利用试验数据对本文方法进行了验证;将本文土压力计算方法与地下结构弯曲微分方程相结合,通过迭代即可得到地下结构的内力及变形,通过算例对该过程进行了分析说明。     

湿空气性质移动计算及焓湿图移动查询

本文介绍了湿空气性质计算基本公式及移动计算的实现方法,并基于J2ME开发实现了湿空气移动计算及焓湿图的移动查询。采用了优化浮点运算、多线程、双缓冲以及优化的计算策略加快运算并减少系统资源占用。文中给出了具体实例,测试及应用结果表明,文中提出的移动实现方法计算精确、快速,提供了随时随地开展湿空气计算和焓湿图查询的手段。     

Exergetic performance assessment of a solar photovoltaic thermal (PV/T) air collector

In this paper, an attempt is made to evaluate the exergetic performance of a solar photovoltaic thermal (PV/T) air collector. A detailed energy and exergy analysis is carried out to calculate the thermal and electrical parameters, exergy components and exergy efficiency of a typical PV/T air collector. Some corrections are done on related heat loss coefficients. An improved electrical model is used to estimate the electrical parameters of a PV/T air collector. Further, a modified equation for the exergy efficiency of a PV/T air collector is derived in terms of design and climatic parameters. A computer simulation program is also developed to calculate the thermal and electrical parameters of a PV/T air collector. The results of numerical simulation are in good agreement with the experimental measurements noted in the previous literature. Finally, parametric studies have been carried out. It is observed that the modified exergy efficiency obtained in this paper is in good agreement with the one given by the previous literature. It is also found that the thermal efficiency, electrical efficiency, overall energy efficiency and exergy efficiency of PV/T air collector is about 17.18%, 10.01%, 45% and 10.75% respectively for a sample climatic, operating and design parameters.     

Airflow distribution through perforated tiles in raised-floor data centers

Raised-floor data centers are the most commonly used facilities for housing computer and telecommunication equipment. To adequately cool this equipment, the cooling air through perforated tiles must be distributed properly. The airflow distribution depends on the pressure distribution or the flow field in the space under the raised floor (plenum); it is a complex function of a large number of variables, including the size of the plenum, the open area of the perforated tiles, the locations and flow rates of the computer room air conditioner (CRAC) units, and the size and location of the under-floor obstructions like cables and pipes. In this article, the effect of these parameters on the airflow distribution is studied using an idealized one-dimensional computational model. Within the one-dimensional framework, the airflow distribution is governed by two dimensionless parameters: one related to the pressure variation in the plenum and the other to the frictional resistance. Results, in terms of distributions of pressure in the plenum and flow rates through the perforated tiles, are presented over a range of values of these two parameters. These results provide an understanding of the fundamental fluid mechanical processes controlling the airflow distribution through the perforated tiles. The one-dimensional model is used to calculate flow rates for two possible arrangements of the CRAC units, and these results are compared with those given by a three-dimensional model.     

Determining osmotic suction through electrical conductivity for unsaturated low-plasticity soils

Determining osmotic suction from the electrical conductivity (EC) of soil pore water was widely reported in the literature. However, while dealing with unsaturated soils, they do not have enough soil pore water to be extracted for a reliable measurement of EC. In this paper, the chilled-mirror dew-point hygrometer and contact filter paper method were used to determine the total and matric suctions for low-plasticity soils with different salinities (0.05‰, 2.1‰, and 6.76‰). A new piecewise function was proposed to calculate the osmotic suction, with the piecewise point corresponding to the first occurrence of precipitated salt in mixed salt solutions (synthetic seawater). EC, ion and salt concentrations used for osmotic suction calculation were transformed from the established relationships of mixed salt solution instead of experimental measurement. The calculated osmotic suction by the proposed equation and the equations in the literature was compared with the indirectly measured one (the difference between the measured total and matric suctions). Results showed that the calculated osmotic suction, especially the one calculated using the proposed function, was in fair agreement with the indirectly measured data (especially for specimens with higher salinity of 6.76‰), suggesting that the transformation of EC and concentrations from the established relationship is a good alternative to direct measurement for low-plasticity soil. In particular, the proposed method could be applied to unsaturated low-plasticity soils which do not have enough soil pore water for a proper EC measurement.     

空调新风随机控制系统的实验研究

在非工业场所，CO2浓度不仅代表了CO2本身作为污染物对室内空气的污染程度，而且还能反映室内人员的状况．体现室内人员对新风的需求。利用CO2浓度可以方便地实现新风量的需求控制。参考欧美等国家和地区的标准，室内CO2浓度的允许值取为1000ppm。在控制系统中，传感器不断地将室内CO2浓度信号转换为电信号，通过A／D转换器转换为数字信号送入计算机与给定值比较，由此获得的偏差值经D／A转换器转换为电信号送入控制器，控制器根据此偏差信号，按照设定的控制规律输出电信号并驱动可逆电机转动，调节风门的开度，从而实现新风量的随机控制。新风阀与回风阀是联动的，以此保证空调系统的总送风量仍为设计值。采用传递函数法进行了理论分析，并在实验小室中，进行了控制系统的参数整定。本控制系统能根据室内情况，在保证室内空气品质的前提下，最大程度地减少空调系统的新风量，降低能耗，达到了节能的目的。     

巷道通风预测的非定常解析系统的开发

研究开发了一种用于地下通风巷道网络的非定常预测解析系统,解析系统包含了巷道外气候的季节变化及巷道壁的围岩与巷道内气流的热传递关系对预测解析的影响因素。采用差分法计算巷道围岩内的温度分布,在自然通风条件下,使用某隧道口的一年间季节变化的实测数据,对一地下通风巷道网络模型进行了预测解析。解析结果表明,该预测解析系统能时时刻刻同时详细地计算地下通风巷道的风量,温度,湿度等通风参数,解析得到的有关通风参数是合理的。     

单峰和双峰土水特征曲线基本参数的确定

土水特征曲线基本参数(如进气值、残余吸力值和过渡区脱湿曲线的斜率等)的确定是预测非饱和土强度、渗透性以及本构关系的基础。基于修正Fredlund和Xing拟合方程,提出单峰和双峰土水特征曲线基本参数的确定方法。首先,对试验数据点进行最优化拟合,获取拟合方程的参数,对于双峰土水特征曲线,根据试样的孔径分布特征将其分段进行拟合;其次,根据拟合方程的几何关系求出过渡区和残余区土水特征曲线的斜率及其切线方程;再根据切线方程可以准确地确定单峰和双峰土水特征曲线的进气值、残余吸力值等。最后,利用单峰和双峰土水特征曲线的试验数据,验证了此方法的可行性。     

数据中心机房新风送风状态点的分析

基于数据中心机房微正压的要求,针对新风系统的能耗控制措施在降低PUE值方面效果显著.新风系统能耗可通过确定系统所需的新风量、准确的新风送风状态点控制.其中,新风送风状态点的选取对新风系统能耗有直接影响.针对数据中心不同通道封闭情况、不同季节的新风处理过程进行了分析,得出了在不同情况下相对合理的机房新风送风状态点,为类似...     

POINT-ESTIMATE MOMENT-BASED RELIABILITY ANALYSIS

In moment-based reliability analysis, the probability of failure is calculated from a probability distribution fitted to the first few calculated moments of a limit state function. The calculation of the moments and the distributions fitting in the analysis are described. We suggest using the point estimate method to calculate the moments of the limit state function. A probability distribution from the Gram-Charlier series type A distributions or the Johnson family of distributions is selected to fit the calculated moments. The method, in general, does not require knowledge of the probability distributions of the basic random variables involved in the limit state function but their statistical moments. The method is simple to implement and can be used directly with an available deterministic computer program because it does not require iteration or derivatives of the limit state function.     

通风空调系统能耗评价方法探讨

以北京市某公共建筑通风空调系统为对象,应用DeST软件模拟通风空调建筑全年热负荷和全年冷负荷,采用当量满负荷运行时间法分析空调系统的能耗,从能源消耗的品质和数量上分析空调系统的能量转换效率ECC,同时探讨了通风空调系统能耗评价方法。     

Investigation of moisture condensation on papermaking plant envelopes in high humidity environment by orthogonal analysis and CFD simulation

The objective of this study is to investigate the problem of moisture condensation on papermaking plant envelopes in high humidity environment. In this study, orthogonal experiment method is combined with CFD simulation to explore how moisture condensation varies with governing factors, such as the thermal parameters of building envelopes, temperature and humidity distributions or ventilation and air distribution. The criteria used by our work to determine whether the condensation will occur on envelopes are to calculate the temperature differences between the inner surface and the air dew point near the envelopes. Specifically, the temperature differences have a linear relationship with the governing parameters, and a first-order linear regression equation is derived, which is validated by data from investigation and measurement. This research provides theoretical support and measurement data for solutions of the envelope condensation problems and anti-condensation design of HVAC systems in papermaking plants.