Methodology for uncertainty calculation of net total cooling effect estimation for rating room air conditioners and packaged terminal air conditioners

This article presents the general procedure for uncertainty calculation of net total cooling effect estimation for rating room air conditioners and packaged terminal air conditioners, by means of measurements carried out in a test bench specially designed for this purpose. The uncertainty analysis presented in this work looks for establishing a confidence degree or certainty of experimental results. It is particularly important considering that international standards related to this type of analysis are too ambiguous when treating this subject. The uncertainty analysis is on the other hand an indispensable requirement to international standard ISO 17025 [ISO, 2005. International Standard. 17025. General Requirement to Test and Calibration Laboratories Competences. International Organization for Standardization, Geneva.], which must be applied to obtain the required quality levels according to the Word Trade Organization WTO.     

家用变频空调标准解释

简介上海市地方标准DB31 355-2006《变速(变频)房间空气调节器能效限定值及能源效率等级》制定的背景、原则及分等的依据,说明在今年6月1日标准开始执行时行业的状况、制订标准的体会及今后尚须深化的方向.     

房间空调器能量调节特性研究

本介绍了房间空调器的开／停式和变频式能量调节机制及其影响因素;分析并比较了两种调节方式的系统结构特点及其对房间空调器性能的影响。同时,对房间空调器今后的发展方向作出了评价。     

空调器非稳态制热量测量方法探讨

分析空调器非稳态制热量测量的特点和常规焓差法在非稳态制热量测量方面的欠缺。提出一种基于焓差法的改进型空调器非稳态制热量测量方法,即前置式测量空调器出风温度的方法,并对这种方法进行试验验证。结果表明,这种方法能够有效排除出风与受风室之间非稳态换热量对测量结果的影响,提高测试精度。     

单元式空调机冷却除湿技术分析

系统地介绍广泛应用于单元式空调机的冷却除湿技术。根据冷凝盘管再热技术在单元式空调机应用方式的不同,归纳4种代表性的方案,并分析每种方案的性能和成本。最后针对这几种不同的设计方案及应用,分别提出不同的技术设计要点和注意事项。     

高能效比家用空调器制冷系统的优化设计

介绍实施2010年最新能效等级标准后一款高能效定频空调器的设计思路和开展过程,包括制冷系统的匹配以及压缩器、蒸发器、毛细管等各主要零部件的选择过程和确认方法.结合工作中出现的问题,指明匹配试验过程中需要注意的事项,介绍关于家用空调器制冷系统匹配的一些经验总结和体会.     

Experimental validation of void fraction models for R410A air conditioners

This paper presents the combined void fraction models on the basis of flow pattern to choose suitable models for calculating the two-phase refrigerant mass of R410A air conditioners, and the model is validated experimentally. The existing single void fraction models are also evaluated experimentally. The Taitel–Dukler flow pattern map is recommended to use in the combined void fraction models. The results presented herein show that the calculated refrigerant mass using the combined void fraction models agrees relatively better with the measured refrigerant mass than that of the single void fraction models. T–B model (for intermittent flow) and Premoli model (for annular flow) are recommended for calculating the two-phase refrigerant mass in evaporator, and T–B model (for intermittent flow) and Harms model (for annular flow) are also indicated for calculating the two-phase refrigerant mass in condenser.     

A general method for calculating the uncertainty of virtual sensors for packaged air conditioners

Virtual sensors use data from low-cost measurements and calibrated models to provide outputs that would either be too expensive or impossible to measure directly. Virtual sensor technology has the potential to enable cost-effective implementation of advanced monitoring, diagnostic, and/or control features for buildings. While it is commonly known that the reliability of virtual sensors depends on the amount and conditions of calibration data, no methods have been presented that quantify the effect of the conditions of calibration data on virtual sensor output uncertainty. In this paper, a general method is presented for estimating the virtual sensor output uncertainty in terms of the uncertainty, conditions and amount of calibration data. The method is demonstrated with a power consumption virtual sensor for packaged air conditioning systems.     

Performance representation of variable-speed compressor for inverter air conditioners based on experimental data

Variable speed control of compressors is one of the best methods to regulate the capacity of heat pumps and air conditioners. An analysis is conducted for modeling the variable speed compressor for simulation of inverter air conditioner and heat pump. Having scattered the real operation performance of inverter compressor into infinite operation performance of constant speed compressor, the map-based method is utilized to fit the performance curves of inverter compressor. The model is built at the basic frequency and the map condition as the second-order function of condensation temperature and evaporation temperature. Then it is corrected by the compressor frequency as the second-order function of frequency and by the actual operating condition as the actual specific volume of the suction gas. This method is used to set up simulation models of three different compressors. Compared with the data provided by the compressor manufacturers, the average relative errors are less than 2, 3 and 4% for refrigerant mass flow rate, compressor power input and coefficient of performance (COP), respectively. This model of variable speed compressor is suitable for the simulation of inverter air conditioner and heat pump systems. Based on the experimental data and simulation model, the frequency at zero mass flow rate and power input at zero frequency are discussed and the relation between COP and compressor frequency is analyzed.     

Decoupling features and virtual sensors for diagnosis of faults in vapor compression air conditioners

This paper describes the development and evaluation of features and virtual sensors that form the basis of a methodology for detecting and diagnosing multiple-simultaneous faults in vapor compression air conditioning equipment. The features were developed based upon a physical understanding of the system, cost considerations, and heuristics derived from experimental data and modeling results. Virtual sensors were developed in order to reduce the cost of implementation. The validity of the features and virtual sensors was evaluated using measurements from a variety of different air conditioners tested in a laboratory environment. More detailed evaluation results are presented in separate papers.     

Improved decohesion modeling with the material point method for simulating crack evolution

A combined elastoplasticity and decohesion model is used with the material point method for the crack problem as described in the Sandia National Laboratories challenge. To predict the cracking path in a complex configuration with the least computational cost, the decohesion modeling is improved by making the failure mode adjustable and by replacing the critical normal and tangential decohesion strengths with the tensile and shear peak strengths, without performing discontinuous bifurcation analysis in each loading step after the onset of failure is identified. It is found that there is a transition between different failure modes along the cracking path, which depends on the stress distribution around the path due to the nonlocal nature of failure evolution. Based on the parametric study and available experimental data, the proposed model-based simulation procedure could be calibrated to predict the essential feature of the observed cracking response.     

Method for simulating atmospheric turbulence phase effects for multiple time slices and anisoplanatic conditions

Simulating the effects of atmospheric turbulence on optical imaging systems is an important aspect of understanding the performance of these systems. Simulations are particularly important for understanding the statistics of some adaptive-optics system performance measures, such as the mean and variance of the compensated optical transfer function, and for understanding the statistics of estimators used to reconstruct intensity distributions from turbulence-corrupted image measurements. Current methods of simulating the performance of these systems typically make use of random phase screens placed in the system pupil. Methods exist for making random draws of phase screens that have the correct spatial statistics. However, simulating temporal effects and anisoplanatism requires one or more phase screens at different distances from the aperture, possibly moving with different velocities. We describe and demonstrate a method for creating random draws of phase screens with the correct space-time statistics for a bitrary turbulence and wind-velocity profiles, which can be placed in the telescope pupil in simulations. Results are provided for both the von Kármán and the Kolmogorov turbulence spectra. We also show how to simulate anisoplanatic effects with this technique.     

混合室轴向结构参数对蒸汽喷射器性能的影响

在实际环境条件下,采用变几何喷射器是提高喷射器性能的重要途径。基于喷嘴距可调式的喷射器实验测试平台,采用实验和数值分析相结合的方法,研究不同无量纲混合室喉部长度下,无量纲喷嘴距对喷射器的性能及不可逆性影响。结果表明：在测试范围内,喷射器的临界喷射系数随着喷嘴距的增加先增加后减小,当达到最佳无量纲喷嘴距5.83时,临界喷射系数达到最大值0.45,合理的喷嘴距应避免激波链出现在混合室收缩段;喷射器的临界冷凝压力随喷嘴距的增加逐渐下降,当无量纲混合室喉部长度为4时,其临界冷凝压力下降7.36%,下降速度最慢,原因是较大的射流冲量提高了扩压室的压力恢复能力,使流体动能衰减速度有所减缓;当无量纲混合室喉部长度为4,无量纲喷嘴距为5.83时,热力学完善度达到最大值0.21;由喷嘴距引起的喷射器熵产主要来源于两股入口流在混合室收敛段的混合和第二冲击波向扩压室出口的移动,提高扩压室的压力恢复能力能有效避免熵产的急剧增加。研究结果对喷射器的结构及综合性能进行多目标优化,以减小喷射器不可逆性提供重要参考。

     

Initial conditions for simulating glass fiber orientation in the filling of center-gated disks

This work is concerned with the effect that initial conditions play in simulating long (>1 mm) glass fiber (LGF) orientation in the filling of a center-gated disk (CGD). For the CGD, most orientation simulations begin at the gate and make assumptions about the initial fiber orientation entering the mold. This paper reports on a method for simulating LGF orientation in a CGD by simulating the sprue, gate, and mold (S–G–M) as a single domain. The velocity field solution is determined using a finite element method including the advancing front. To predict LGF orientation, rigid and flexible fiber models are employed using parameters obtained from rheology. It is observed that predicting LGF orientation in systems with either model is highly sensitive to the choice of initial conditions. Furthermore, the flexible fiber model is observed to be more successful at predicting LGF orientation based on agreement with experimental results.     

Investigation of an experimental ejector refrigeration machine operating with refrigerant R245fa at design and off-design working conditions. Part 1. Theoretical analysis

The ejector refrigeration machine (ERM) offers several advantages over other heat-driven refrigeration machine, including simplicity in design and operation, high reliability and low installation cost, which enable its wide application in the production of cooling. In this paper the theoretical analysis of ejector design and ejector refrigeration cycle performance is presented. It is shown that ERM performance characteristics depend strongly on the operating conditions, the efficiency of the ejector used, and the thermodynamic properties of the refrigerant used. A 1-D model for the prediction of the entrainment ratio ω, and an optimal design for ejectors with cylindrical and conical-cylindrical mixing chambers are presented in this paper. In order to increase ERM performance values, it is necessary first of all to improve the performance of the ejector.     

Improved fractional step method for simulating fluid‐structure interaction using the PFEM

Numerical difficulties are present in the particle finite element method even though it has been shown to be a powerful and effective approach to simulating fluid‐structure interaction. To overcome problems of mass loss on the free surface and the added‐mass effect, an improved fractional step method (FSM) that handles added‐mass terms in a mathematically exact way is developed. A further benefit is that no assumptions regarding the structural response are made in handling added‐mass terms, thus it is straightforward to incorporate material nonlinearity in fluid‐structure interaction (FSI) under this approach. Patch tests and comparisons with experimental data are presented in order to verify and validate the improved FSM for FSI applications. The computational cost of this approach is shown to be negligible compared with the other aspects of the FSM, particularly when the size of the structure and the fluid‐structure interface is small relative to the volume of fluid. Copyright © 2014 John Wiley & Sons, Ltd.     

单元式空气调节机IPLV（C）测试中插值计算方法的研究

介绍单元式空气调节机标准中水冷式空调机的制冷综合部分负荷性能系数IPLV（C）的测试计算方法，对空调机无法准确卸载到75％，50％以及25％负荷能力的情况的插值计算方法进行分析，提出3种插值方案，并通过试验对比这3种插值方案计算IPLV（C）结果的差异。     

Some philosophies and methodologies for a knowledge-based standardization in fracture at high temperature

The concept is proposed for a knowledge-based standardization in fracture at high temperature. Examples are presented of the high temperature creep growth and fracture life, and the testing methodology of hard brittle materials with notch is discussed.     

Investigation of an experimental ejector refrigeration machine operating with refrigerant R245fa at design and off-design working conditions. Part 2. Theoretical and experimental results

The main results of a theoretical and experimental investigation of the performance characteristics of an ejector and an ejector refrigeration machine (ERM) operating with refrigerant R245fa at design and off-design working conditions are presented. The ejector and ERM were explored theoretically using improved 1D model and the calculated results were validated experimentally on ejector test rig that has been assembled and operated at National Taiwan University. For typical cases, the performance characteristics variation with condensing, generating and evaporating temperatures along with performance maps are presented. The theoretical results are compared with the results of a set of experiments and good qualitative and quantitative agreement is observed.