Predicting natural ventilation in residential buildings in the context of urban environments

The objective of this dissertation was to develop, through systematic research and experimentation, a mathematical model for predicting exterior surface pressures and indoor air velocities for small-scale buildings in urban settings. The resulting model is a step-by-step series of functions that produce these results while accounting for various possible geometric relationships between the building and the urban surroundings.This study was conducted in two phases. The first phase developed an empirical Pressure Prediction Model (PPM) for shielded surfaces using a sequence of wind tunnel tests. The model produces a non-dimensional Pressure Modification Coefficient (Cpm) using a set of geometric variables that describe urban surroundings in terms of obstruction blocks and the gaps between them. A number of empirical corrections account for horizontal displacement of obstructions and for wind direction effects. Cpm is then used to calculate the average pressure coefficient on shielded surfaces. The wind tunnel tests show that the shielding effect of an obstruction block is significant within a ±70° arc around the wind direction, and that it is possible to predict the shielding effect of multiple obstruction blocks within this arc by averaging the shielding effects of individual obstruction blocks and summing the effects of all the gaps.The second phase concentrated on the development of an Indoor Velocity Prediction Model (IVM). The IVM uses the PPM-predicted surface pressures on shielded walls as input to a model developed by Ernest (1991) to determine the Indoor Velocity Coefficients (IVC). The IVM model also adopts a procedure developed by Arens et al (1986) to convert remote weather station data into site-specific wind speeds. Arens’ procedure corrects for the differences in height between the weather station and the site, the differences in terrain roughness characteristics between the two locations, and wind acceleration due to site topography.The PPM was verified against Wiren’s (1984) tests of an instrumented model in different arrays of similarly configured obstruction blocks, and against an instrumented model in a more complex layout. The predicted and the measured pressure values showed a reasonably good fit in both cases. The successes and limitation of the model are discussed.The IVM predictions of interior airflow were not validated here. Ernest has validated his model in both unobstructed and simply-obstructed conditions, and the PPM is not expected to change the nature of the interior flows predicted by Ernest’s model

Predicting natural ventilation in residential buildings in the context of urban environments

The objective of this dissertation was to develop, through systematic research and experimentation, a mathematical model for predicting exterior surface pressures and indoor air velocities for small-scale buildings in urban settings. The resulting model is a step-by-step series of functions that produce these results while accounting for various possible geometric relationships between the building and the urban surroundings.This study was conducted in two phases. The first phase developed an empirical Pressure Prediction Model (PPM) for shielded surfaces using a sequence of wind tunnel tests. The model produces a non-dimensional Pressure Modification Coefficient (Cpm) using a set of geometric variables that describe urban surroundings in terms of obstruction blocks and the gaps between them. A number of empirical corrections account for horizontal displacement of obstructions and for wind direction effects. Cpm is then used to calculate the average pressure coefficient on shielded surfaces. The wind tunnel tests show that the shielding effect of an obstruction block is significant within a ±70° arc around the wind direction, and that it is possible to predict the shielding effect of multiple obstruction blocks within this arc by averaging the shielding effects of individual obstruction blocks and summing the effects of all the gaps.The second phase concentrated on the development of an Indoor Velocity Prediction Model (IVM). The IVM uses the PPM-predicted surface pressures on shielded walls as input to a model developed by Ernest (1991) to determine the Indoor Velocity Coefficients (IVC). The IVM model also adopts a procedure developed by Arens et al (1986) to convert remote weather station data into site-specific wind speeds. Arens’ procedure corrects for the differences in height between the weather station and the site, the differences in terrain roughness characteristics between the two locations, and wind acceleration due to site topography.The PPM was verified against Wiren’s (1984) tests of an instrumented model in different arrays of similarly configured obstruction blocks, and against an instrumented model in a more complex layout. The predicted and the measured pressure values showed a reasonably good fit in both cases. The successes and limitation of the model are discussed.The IVM predictions of interior airflow were not validated here. Ernest has validated his model in both unobstructed and simply-obstructed conditions, and the PPM is not expected to change the nature of the interior flows predicted by Ernest’s model

A parametric study of impact of Neighborhood Morphology on air pollution dispersion patterns due to unplanned building demolition.

An unplanned demolition of a building can be a result of either natural e.g. earthquake or human-made disaster e.g. terrorist attack and wars. It generates considerable amount of coarse, fine and ultrafine Particulate Matter, which are significantly associated with chronic and acute adverse health effects. Literature study attributed to few studies about the impact of planned demolition on local air quality, while the short-term bursts of pollutants and public exposure to this high pollution levels during an unplanned demolition were widely overlooked. Meanwhile, the existing research has also pointed out that the characteristics of the pollutant dispersion are highly dependent on the urban morphology. The primary objective of this research is to investigate the pattern and characteristics of pollution dispersion due to unplanned building demolition in a compact high-rise/ low rise and open high-rise/ low rise neighborhood. CFD-based microscale air quality model “ENVI-met” was used to simulate the pollution dispersion in the selected morphologies. The pollution concentration was measured at the various horizontal and vertical distance at various times and wind directions (0 and 315 deg). Thirty-six different measurement from horizontal dispersion and forty-eight different measurements from vertical dispersion for PM concentration and wind speed were measured and tabulated. LEONARDO was used to visualize the output in ENVI_met binary files and Microsoft Excel was used to plot the graphs showing a summary of relationship between the tested parameters. The results indicated that the pollution dispersion pattern depended on its neighborhood morphology which is represented by its street canyon and building height, wind flow and vegetations. These findings are followed by the design recommendations based on the observation of pollution dispersion pattern in different morphologies while suggesting a need of air quality standards for short term high pollution levels

Passive solar cooling systems in hot-arid climates, The architectural implications of

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Architecture, 1988.Includes bibliographical references (leaves 245-250).Residential architectural design should fulfill both the comfort and the social requirements of the occupants. Khartoum, the capital of the Sudan was chosen for this study because of two reasons; The first is its unusually hot-arid climate (thus cooling interior spaces becomes a crucial design consideration). and the second is its multi-dimensional urban identity. The city is a mixture of African, Arab, and European influences and resembles at the same time an oasis in the middle of the desert. The research follows two distinct but closely related paths. The first is the study and analysis of the passive and hybrid cooling systems and strategies under which the climatic conditions of Khartoum determines the type and size of each approach. The second stage of the research will focus on the architectural implications of these systems. Both directions lead to better understanding of the built environment and its interactions with man. Two moves were taken into account, when considering the cooling potentials in this climate. First, the solar control strategies which were found to be most appropriate in Khartoum climatic conditions. These include the use of eggcrate shading devices on all openings except for southern exposures which can be shaded effectively by vertical fins to reduce the solar transmission through glazed surfaces. The study showed also that reducing the glazed area reduces the total heat gain but this affects negatively both daylighting and the freedom of design to incorporate the exterior spaces. This can be solved by using the Low-E glass which has better thermal properties in terms of reducing both solar transmission and heat conduction. The results of the study showed that using single Light-Green Low-E glass allows one and half times larger glass area with the same amount of heat gain. For the same area, the Double Low-E glass can reduce heat gain form these surfaces by a factor of two. Economically, their use is hard to justify because of their projected high prices as compared to the DS single pane clear glass. Another effective way of controlling the heat gain through buildingskin is to use thermal insulation on the walls and roof. Roof insulation which Is commonly specified in Khartoum was found to be thermally satisfactory and additional insulation will not reduce heat gain appreciably since the roof share is already reduced with basic insulation. The wall insulation strategy proved to be economically feasible and does not require skilled labor to install or to maintain since it is protected from the weather. Landscaping is another move that will improve the environmental quality through shading and evaporatively cooling the surrounding spaces and at the same time add to the visual quality of the space, but it is not cost effective. The second move was to promote heat losses through ventilation, convection, radiation, and evaporation. Because of the environmental condition of Khartoum, the first three moves are restricted to certain parts of the day or the year. Nevertheless, combination of either one with evaporative cooling increases the thermal comfort. The desert-type evaporative coolers reduce the indoor temperature and increase the relative humidity which is required in the dry periods of the year. Two-stage coolers which combines both evaporative (adiabatic) and sensible cooling concepts increases the rate of heat removal and thus reduces obtained indoor temperature. The air scoops or wind catchers are convective and evaporative cooling systems that admit high winds at high elevations to be circulated inside living spaces for ventilation. This air can be further cooled be passing the air stream over wet Clay jars or through wetted pads.by Adil M.K. Sharag-Eldin.M.S

Rare Presentation of Cardiotoxicity Related to 5-Fluorouracil

5-Fluorouracil (5-FU) is a chemotherapeutic agent frequently used for the treatment of solid tumors. In a few cases, 5-FU can be associated with coronary vasospasm, cardiac ischemia, or life-threatening arrhythmias. Recognition of 5-FU cardiotoxicity is clinically important as after the rapid sensation of therapy, cardiotoxicity can be completely reversible, and on the other hand, readministration may lead to serious damage of the heart and even death. A 70-year-old male came to the emergency department (ED) with chest pain which started while receiving an infusion of 5-FU. The patient did not have a personal history or risk factors of coronary artery disease and his electrocardiogram (ECG) before starting chemotherapy was completely normal. In the ED, his ECG had ischemic changes, troponin was elevated, and echocardiogram showed anterior wall hypokinesis. However, emergent coronary angiogram did not reveal any acute coronary occlusion. 5-FU-induced cardiotoxicity was suspected; the patient was admitted to a progressive care unit for close monitoring and infusion of calcium channel blockers was initiated. The patient’s symptoms and ECG findings gradually resolved, and two days later on discharge, patient was chest pain free and ECG was normal. This case supports the vasospastic hypothesis of 5-FU cardiac toxicity, describes its clinical course, and emphasizes the importance of better awareness and early recognition of the rare side effect as it may allow physicians to reduce the risk of life-threatening complications