Experimental investigation of free convection in roof solar collector

A test set-up was developed for determining the internal convective heat transfer coefficient and the induced air flowrate of a roof solar collector. The set-up was composed of an open-ended inclined rectangular channel. The tilt angle and air gap of channel were fixed at 30° and $\text{140}\text{mm}$, respectively. The inner channel width and length were 680 and $\text{1360}\text{mm}$, respectively. The upper plate was maintained at a uniform temperature and tests were carried out for a wide range of temperature varying between 40°C and 75°C. Data analysis were made to develop Nusselt and Reynolds number correlations as a function of Rayleigh number and aspect ratio (gap/length). The equations could be used for determining the mean convection heat transfer coefficient and the induced air flowrate of the roof solar collectors and a wide range of convective heat exchangers of similar geometry as well.     

CFD study on micro-environment around human body and personalized ventilation

A seated computational thermal manikin (CTM) with geometry of a real human body is used to study the micro-environment around human body with and without personalized ventilation (PV) system. Two novel evaluation indices, pollutant exposure reduction and personalized air utilization efficiency, are introduced. In the range of the personalized airflow rate from 0.0 to $\text{3.0}\text{l/s}$, the best inhaled air quality is achieved at the airflow rate of $\text{0.8}\text{l/s}$ in the numerical simulation, whereas in our earlier experiments this occurred at the maximum flow rate $\text{3.0}\text{l/s}$. Through detailed analysis of interaction between thermal plume around human body and personalized airflow, the mechanism of inhalation process becomes more perspicuous. Results from computational fluid dynamics (CFD) and experiment are compared and improvements of CFD simulation accuracy are recommended.     

Particle deposition in ventilation duct onto three-dimensional roughness elements

Gaining insights on particle deposition onto ventilation duct has many important applications. One key pathway by which outdoor polluted air enters the indoor environment is through mechanical ventilation ducts. An experimental system was designed for the study of particle deposition on regular arrays of uniform elements (in the form of discrete protrusions) in a turbulent ventilation duct flow using monodisperse tracer small particles, in the range 0.7–$\text{7.1}\text{μm}$. The Reynolds number for the test conditions was 44,000 in the $\text{150}\text{mm}$ square duct. Four different types of uniform roughness elements were tested. Compared to earlier measurements in the same duct system involving smooth or ribbed surfaces, a significant increase (up to 74 times) in deposition velocity onto the regular roughness elements is observed.     

Field measurement and experimental study of wind speed profile during thunderstorms

This paper investigates the variation of wind velocity with height during thunderstorms. Wind velocities during thunderstorms are measured at five levels on a $\text{150}\text{m}$ tall tower. Velocity profiles for more than 50 thunderstorms are studied. In the analysis, these profiles are classified into four types according to the profile shape and the height of the highest wind speed. It is observed that wind profiles during thunderstorms are affected by several factors with the major ones being distance from the thunderstorm cell centre, intensity of the storm and ground roughness. Experimental studies on the simulation of thunderstorm wind using an impinging jet are also carried out to further investigate the effect of these parameters.     

Stone decay in 18th century monuments due to iron corrosion. The Royal Palace,Madrid (Spain)

This study was designed to determine the origin, processing methods and the structural and compositional properties of the iron used in the construction of the Palacio Real, Madrid, in the form of reinforcement bars and ties used for the support and anchorage of stone elements. These iron structures, analysed by XRD, ICP-AES, ICP-MS, SEM+EDX, EPMA, magnetometry and ultrasounds velocity were found to be of high-quality iron. The iron, worked in an air furnace at a temperature below 690°C followed by puddling, is composed of ferrite and cohenite. Two types of slag were detected as streaks in the iron: friedelite–vivianite and friedelite–titanomagnetite. These bands of impurities in the iron favour corrosion processes that give rise to iron hydroxides (lepidocrocite followed by goethite) causing an 83% increase in volume. This volume increase exerts a pressure of some $\text{196}\text{MPa}$ leading to fissuring and disaggregation of the stone.     

Size-dependent particulate matter indoor/outdoor relationships for a wind-induced naturally ventilated airspace

We applied a simple size-dependent indoor air quality model associated with measured outdoors particulate matter (PM) profiles and potential loss mechanisms to characterize PM indoor/outdoor (I/O) relationships for wind-induced naturally ventilated residences in Taiwan region. The natural ventilation rate was quantified by the opening effectiveness for sidewall opening and covered ridge with sidewall-opening-type homes. The measured results demonstrate that integrated PM₁₀ and PM_2.5 mass concentrations for the urban area are 39.2 and $\text{3.13}\text{μg}\text{m}{}^{\mathrm{-3}}$, respectively, whereas for the suburban area are 75.76 and $\text{69.87}\text{μg}\text{m}{}^{\mathrm{-3}}$, respectively. The most significant removal mechanisms included natural ventilation through and particle deposition on indoor surfaces. The predicted average PM mass I/O ratios were 0.56 and 0.42 for PM_2.5 and PM₁₀, respectively. We also employed published data on mass-weighted size distributions for specific chemical constitutes of PM, sulfate and nitrate, to predict PM I/O ratios in the central Taiwan region; the resulting values ranged from 0.22 to 0.43 and 0.27 to 0.36 for sulfate and nitrate, respectively. Our results demonstrate that the PM I/O ratios for a wind-induced natural ventilated airspace depend strongly on the ambient particle distributions, building openings design (e.g. height-to-length ratio of openings and roof slope), wind speed, wind angle of incidence, and outdoor PM metrics.     

A new synthesis method for signals for testing of flame-detection algorithms

In this contribution, the development of a method for generating input data, for testing and optimising fire recognition algorithms, is presented. This work concentrates on the analysis and evaluation of sensor signals for detecting electromagnetic radiation in the infrared spectrum (IR). A current problem is the differentiation between the signal of a flame and the effect of non-fire IR sources in the same IR wavelength area that cause disturbance signals. The objective is to achieve a highly sensitive, early detection of fire and at the same time suppress false alarms. For testing of signal-processing algorithms, a great number of input data must be available reflecting a great variety of combinations of flame and non-fire IR source scenarios. Generally, these data records are created by test fires and physical simulation of simultaneous non-fire IR sources. The aim of this work is to develop a method for generating such input data based on a reduced number of experimental data. Our approach is to gain model functions based on measured sensor signals that are used to create parametric models. Assuming the linearity of the sensor transfer function, the synthesised signal components are superposed linearly and simulation signals are generated as new input signals. A uniform approach was developed for the simulation of signals caused by flames and non-IR sources. Three signal components were defined by their frequency range, the base function with $\text{f<1}\text{Hz}$, the flickering component with $\text{1}\text{Hz}\text{⩽f<10}\text{Hz}$ and the noise component with $\text{10}\text{Hz}\text{⩽f<256}\text{Hz}$. The modelling of the base function was carried out by cubic spline interpolation. Assuming that the flickering and noise components are stationary and non-deterministic, autoregressive models are used for the analysis of signals and for generating new random sequences. Comparison of the measured signal and the respective generated simulation data show a good consistency. Hence, considerably more effective input data records can be created for testing and optimisation of signal-processing algorithms. Generally, the method presented can also be applied for the simulation of signals generated by sensors utilising other physical detection principles.