Industrial Aerodynamics. Mr.B.Navin Kumar Senior Lecturer Rajalakshmi Engineering College Thandalam-602 105. Unit - I. ATMOSPHERIC BOUNDARY LAYER. Atmospheric circulation.
Rajalakshmi Engineering College
Local winds blow over a much smaller area than global winds and have a much shorter time span. Hot windsoriginate in vast anticyclones over hot deserts and include the Santa Ana (California), the Brickfielder (south-east Australia), the Sirocco (Mediterranean), the Haboob (Sudan), the Khamsin (Egypt), and the Harmattan (West Africa).
A local wind is a little zephyr that one can get occasionally. A global wind would be the jet streams.
Aerodynamicists use wind tunnels to test models of proposed aircraft and engine components. During a test, the model is placed in the test section of the tunnel and air is made to flow past the model. Various types of instrumentation are used to determine the forces on the model. There are four main types of wind tunnel tests.
BLUFF BODY AERODYNAMICS
The Strouhal number St is a function of the Reynolds number Re (although a sufficiently varying one that it may be said that it is typically equal to 0.2, e.g. see figure below) and is proportional to the reciprocal of vortex spacing expressed as a number of obstacle diameter. It is used in the momentum transfer in general, and in both Von Karmann vortex streets and unsteady flow calculations in particular. It is normally defined in the following form :
where : - n is the frequency of the observed phenomenon,
- d is the characteristic length (which is the diameter of the cylinder in the case of vortex streets),
- U is the velocity of the fluid.
The number of cars available on our planet is continuously increasing. But also other factors are important for the emissions and the energy consumption: How efficient is the motor of the car? How much fuel does it consume on a certain distance? How long are the distances the car owner goes per year in average? What driving style does the driver exhibit? What is the average speed?
WIND ENERGY COLLECTORS
Most of the technology described on these pages is related to horizontal axis wind turbines (HAWTs, as some people like to call them).
The reason is simple: All grid-connected commercial wind turbines today are built with a propeller-type rotor on a horizontal axis (i.e. a horizontal main shaft).
The purpose of the rotor, of course, is to convert the linear motion of the wind into rotational energy that can be used to drive a generator. The same basic principle is used in a modern water turbine, where the flow of water is parallel to the rotational axis of the turbine blades.
Vertical Axis Wind Turbines Eole C, a 4200 kW Vertical axis Darrieus wind turbine with 100 m rotor diameter at Cap Chat, Québec, Canada. The machine (which is the world's largest wind turbine) is no longer operational.
Vertical axis wind turbines (VAWTs as some people call them) are a bit like water wheels in that sense. (Some vertical axis turbine types could actually work with a horizontal axis as well, but they would hardly be able to beat the efficiency of a propeller-type turbine).
The only vertical axis turbine which has ever been manufactured commercially at any volume is the Darrieus machine, named after the French engineer Georges Darrieus who patented the design in 1931. (It was manufactured by the U.S. company FloWind which went bankrupt in 1997). The Darrieus machine is characterised by its C-shaped rotor blades which make it look a bit like an eggbeater. It is normally built with two or three blades
Very simply, we just divide the electrical power output by the wind energy input to measure how technically efficient a wind turbine is. In other words, we take the power curve , and divide it by the area of the rotor to get the power output per square metre of rotor area. For each wind speed, we then divide the result by the amount of power in the wind per square metre.
The graph shows a power coefficient curve for a typical Danish wind turbine. Although the average efficiency for these turbines is somewhat above 20 per cent, the efficiency varies very much with the wind speed. (If there are small kinks in the curve, they are usually due to measurement errors).
Building code, or building control, is a set of rules that specify the minimum acceptable level of safety for constructed objects such as buildings and nonbuilding structures. The main purpose of building codes are to protect public health, safety and general welfare as they relate to the construction and occupancy of buildings and structures. The building code becomes law of a particular jurisdiction when formally enacted by the appropriate authority.
Ventilating(the V in HVAC) is the process of "changing" or replacing air in any space to provide high indoor air quality (i.e. to control temperature, replenish oxygen, or remove moisture, odors, smoke, heat, dust, airborne bacteria, and carbon dioxide). Ventilation is used to remove unpleasant smells and excessive moisture, introduce outside air, to keep interior building air circulating, and to prevent stagnation of the interior air.