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Developments. Preindustrial Era: prior 1800s where the building envelop was the principal means of controlling thermal environment and illumination within the building Industrial Era : Architecture has changed due to changes in materials, technology even knowledge. Developments. Energy .
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Developments • Preindustrial Era: prior 1800s where the building envelop was the principal means of controlling thermal environment and illumination within the building • Industrial Era: Architecture has changed due to changes in materials, technology even knowledge
Energy What is Energy: is an indirectly observed quantity which comes in many forms Energy Forms: 1. Kinetic Energy Which depends on motion 2. Potential Energy which depends on position 3. Radiant Energy is the energy of electromagnetic waves
Energy • Units: • The most important energy units are: • Joule (J)= NM (work) =Force*Displacement 1kJ=1000J 1MJ=1000000J • kWh = 3600 kJ • Calorie =4.1868 J • British Thermal Unit (BTU)=1.055056kJ
Energy Examples: • Convert 10 J into Calorie Answer is 10/ 4.1868= 2.388459 • Convers 10kWh into Calorie Answer: 10kWh? In kJ kJ=3600*10=36 MJ Calorie=36000000/4.1868=8598452.27859=8.6MCalorie
Principle of Conservation of Energy • It states that the total amount of energy in an isolated system remains constant over time • Energy can not be created or destroyed. It can be changed from one form to another. • This law means energy is localized and can change its location within the system, and it can change form within the system, for example, mechanical energy can become electric energy
Heat Transfer • Heat is energy transferred from one body to another by thermal interactions (energy transit or moving energy) • Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy and heat between physical systems.
Heat Transfer • Heat transfer Mechanism: • Thermal Conduction (Solid materials have better conductivity than liquids and gases) • Thermal Convection(dominant form of heat transfer in liquids and gases) • Thermal Radiation
Thermal Conduction • Conduction heat transfer: Heat conduction occurs as hot, rapidly moving or vibrating atoms and molecules interact with neighbouring atoms and molecules, transferring some of their energy (heat) to these neighbouring particles
Thermal Conduction • If one end of a metal rod is at a higher temperature, then energy will be transferred down the rod toward the colder end.
Thermal Conduction • The rate of conduction heat transfer or loss is: • Where Q is heat transfer in time t • k is the thermal conductivity of the barrier (next) • A is the surface area • T is temperature • d is barrier thickness
Thermal Conduction Example: what is the rate of heat loss for a steel door of 2.5 m^2 area with 6 cm thickness if the hot temperature interred this door at 318.15 K at exited at 300 K? • Answer =(50.2*2.5(318.15-300))/6 =379.6375
Thermal Convection • Thermal Convection heat transfer is heat transfer by mass motion of a fluid such as air or water when the heated fluid is caused to move away from the source of heat, carrying energy with it. • Convection above a hot surface occurs because hot air or fluid expands, becomes less dense, and rises
Thermal Convection • Natural Thermal Convection heat transfer occurs when bulk fluid motions (steams and currents) are caused by buoyancy forces that result from density variations due to variations of temperature in the fluid. • Forced Thermal Convection heat transfer is a term used when the streams and currents in the fluid are induced by external means—such as fans, stirrers, and pumps—creating an artificially induced convection current
Radiant heat transfer • Radiation heat transfer happens when electromagnetic field travel through space. When electromagnetic waves come into contact with an object, the waves transfer the heat to the object • Examples Microwave oven Light pulp
Solar Radiations • The figure shows the solar radiation spectrum for direct light at both the top of the Earth's atmosphere and at sea level • The sun produces light with a distribution similar to what would be expected from a 5525 K (5250 °C) blackbody, which is approximately the sun's surface temperature • As light passes through the atmosphere, some is absorbed by gases with specific absorption bands
Radiant heat • When the heat radiation is projected onto the object surface, usually three phenomena occur: • Absorption • Reflection • Transmission
Absorption • Absorption: is the fraction of irradiation absorbed by a surface. • Absorption of electromagnetic radiation is the way in which the energy of a photon is taken up by matter, typically the electrons of an atom. Thus, the electromagnetic energy is transformed into internal energy of the absorber, for example solar panels
Reflection • Reflectivity: is the fraction reflected by the surface. • It is generally refer to the fraction of incident electromagnetic power that is reflected at an interface
Transmission • Transitivity is the fraction of electromagnetic radiation at a specified wavelength that transmitted by the surface
Solar energy on Architecture and urban planning • Sunlight has influenced building design since the beginning of architectural history: Solar effect on urban planning were first employed by the Greeks and Chinese, who oriented their buildings toward the south to provide light and warmth • Agriculture: Agriculture and horticulture seek to optimize the capture of solar energy in order to optimize the productivity of plants
Solar energy on Architecture and urban planning • Agriculture • Greenhouses: in greenhouses solar light is converted into heat enabling year-round production and the growth (in enclosed environments) of specialty crops and other plants not naturally suited to the local climate. • The first modern greenhouses were built in Europe in the 16th century to keep exotic plants brought back from explorations abroad
Solar energy on Architecture and urban planning • Solar thermal: Solar thermal technologies can be used for water heating, space heating, space cooling and process heat generation • Solar electric: where sun light converted to produce electricity
Microclimate • Microclimate is a local atmospheric zone where the climate differs from the surrounding area. Example this room climate is different from the whole building, The building climate is different from the whole university climate, etc. It may refer to areas as small as a few square metersor as large as many square meters • It is important to architect to understand microclimate to design houses that more energy efficient.
Factors affecting Microclimate • Temperature • Humidity • Wind • Solar radiation
Factors affecting Microclimate • Temperature: temperature affected by: • Altitude: Air temperature drops 1°C for 100 m rise in altitude during summer and 130 m in winter • Proximity to water: Sea and lakes drops surrounding temperatures • Ground Cover: Natural vegetation tends to moderate extreme temperature (Green roof houses) • Urban development: it raises air temperature because it blocks winds.
Factors affecting Microclimate 2. Humidity: the amount of water vapour in the air Humidity affected by: • Altitude: Humidity decreases with higher altitude • Proximity to water: Sea and lakes increases Humidity • Ground Cover: Natural vegetation tends to increase humidity(Green roof houses) • Urban development: decreases humidity near the ground
Factors affecting Microclimate 3. wind affected by two factors which determine wind speed. The pressure gradient is the first. The second is friction • Altitude: wind speed increases at higher altitude • Urban development: decreases wind speed
Factors affecting Microclimate 4. Solar radiation affecting microclimate as south facing slope receive greater solar radiations than north slopes resulting higher ground temperature.
Factors affecting Microclimate The usage of overhangs and shades
Optimum site location Temperature (in winter) we need to make the site warmer by implementing: 1. Maximize solar exposure 2. Provide means to reduce outgoing radiation at night 3.Remove shading devices during day 4. Use heat retaining structural materials i.e. concrete 5. Locate outdoor on the south or south west side of the buildings
Optimum site location Temperature (in summer) we need to make the site cooer by implementing: • Extensive use of trees as shade • Use overhangs and light colour blinds • Use ground covers on earth surfaces rather than paving • Use areas on north and east of the building for outdoor activities
Optimum site location Humidity to make the site more humid we need to implement: • Allow standing water on the site all the time • Increase overhead planting to add moisture • Use grass as ground cover • Add water fountain, pool, water features and etc.
Optimum site location Humidity to make the site drier we need to implement: • Maximize solar radiation exposure and reduce shadings and overhangs • Increase ventilation and air flow • Install efficient drainage system • Use pavement like tarmac • Reduce grass and plantings • Eliminate water fountains, pools and water features
Optimum site location Wind to make the site less windy: • Use extensive wind break like trees and structures • Do not trim lower branches of tall trees
Optimum site location Wind to increase wind flow: • Remove all obstruction (trees, structures, etc.) • Trim all lower branches of tall trees • Limit all trees grow to 3 m • Built dicks or platforms on the areas most exposed to breezes
Cooling Load • Cooling load (heat gain): Is the amount of heat energy to be removed from a space by the HVAC equipment to maintain the space at a certain comfort level
Cooling Load Types • Latent heat: Is the heat content due to the presence of water vapour in the atmosphere • Sensible heat: Is the heat content causing an increase in dry bulb temperature • Total gain: Is the sum of latent and sensible
