Developments Preindustrial Era: prior 1800s where the building envelop was the principal means of...

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

Pre Industrial Era Industrial Era

Thick external Thin minimum skin

Tight thermal envelop Mechanical HVAC

Short depth for light Greater depth for light due to artificial lighting

Short depth for ventilation Big depth for ventilations due to forced convection

High Ceiling Low ceiling

Low rise buildings High rise buildings

Materials was restricted to available resources All Materials are available due to transport

Energy

• What is Energy: is an indirectly observed quantity which comes in many forms

• Energy Forms:1. Kinetic Energy Which depends on

motion2. Potential Energy which depends on position3. Radiant Energy is the energy of

electromagnetic waves

Energy

• Units:• The most important energy units are:1. Joule (J)= NM (work) =Force*Displacement

1kJ=1000J 1MJ=1000000J2. kWh = 3600 kJ3. Calorie =4.1868 J 4. British Thermal Unit (BTU)=1.055056 kJ

Energy

Examples:

• Convert 10 J into Calorie Answer is 10/ 4.1868= 2.388459

• Convers 10kWh into CalorieAnswer: 10kWh? In kJ kJ=3600*10=36 MJCalorie=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:1. Thermal Conduction (Solid materials have

better conductivity than liquids and gases)2. Thermal Convection(dominant form of heat

transfer in liquids and gases)3. Thermal Radiation

Example of mechanism

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

d

TTkA

t

Q coldhot

Thermal Conductivity (k)Material Thermal conductivity

(W/m K)*Material Thermal conductivity

(W/m K)*

Diamond 1000 Fiberglass 0.04

Silver 406.0 Brick, insulating 0.15

Copper 385.0 Brick, red 0.6

Gold 314 Cork board 0.04

Brass 109.0 Wool felt 0.04

Aluminium 205.0 Rock wool 0.04

Iron 79.5 Polystyrene (Styrofoam) 0.033

Steel 50.2 Polyurethane 0.02

Lead 34.7 Wood 0.12-0.04

Mercury 8.3 Air at 0° C 0.024

Ice 1.6 Helium (20°C) 0.138

Glass, ordinary 0.8 Hydrogen(20°C) 0.172

Concrete 0.8 Nitrogen(20°C) 0.0234

Water at 20° C 0.6 Oxygen(20°C) 0.0238

Asbestos 0.08 Silica aerogel 0.003

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

d

TTkA

t

Q coldhot

t

Q

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

Natural Thermal Convection

Forced Thermal Convection

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

Radiant heat transfer

Solar Radiations

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:

1. Absorption2. Reflection3. 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

Distribution of Sun’s energy

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


• 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 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 meters or as large as many square meters

• It is important to architect to understand microclimate to design houses that more energy efficient.

Microclimate

Factors affecting Microclimate

1. Temperature2. Humidity3. Wind4. Solar radiation


1. Temperature: temperature affected by:1. Altitude: Air temperature drops 1°C for 100 m rise

in altitude during summer and 130 m in winter2. Proximity to water: Sea and lakes drops

surrounding temperatures3. Ground Cover: Natural vegetation tends to

moderate extreme temperature (Green roof houses)

4. Urban development: it raises air temperature because it blocks winds.


2. Humidity: the amount of water vapour in the airHumidity affected by:

1. Altitude: Humidity decreases with higher altitude 2. Proximity to water: Sea and lakes increases Humidity3. Ground Cover: Natural vegetation tends to increase

humidity(Green roof houses)4. Urban development: decreases humidity near the

ground


3. wind affected by two factors which determine wind speed. The pressure gradient is the first. The second is friction

1. Altitude: wind speed increases at higher altitude 2. Urban development: decreases wind speed


4. Solar radiation affecting microclimate as south facing slope receive greater solar radiations than north slopes resulting higher ground temperature.


The usage of overhangs and shades

Optimum site location

Temperature (in winter) we need to make the site warmer by implementing:

1. Maximize solar exposure2. Provide means to reduce outgoing radiation at

night3.Remove shading devices during day4. Use heat retaining structural materials i.e.

concrete 5. Locate outdoor on the south or south west

side of the buildings


Temperature (in summer) we need to make the site cooer by implementing:

1. Extensive use of trees as shade 2. Use overhangs and light colour blinds3. Use ground covers on earth surfaces rather than

paving4. Use areas on north and east of the building for

outdoor activities


Humidity to make the site more humid we need to implement:

1. Allow standing water on the site all the time2. Increase overhead planting to add moisture3. Use grass as ground cover 4. Add water fountain, pool, water features and etc.


Humidity to make the site drier we need to implement:

1. Maximize solar radiation exposure and reduce shadings and overhangs

2. Increase ventilation and air flow3. Install efficient drainage system4. Use pavement like tarmac 5. Reduce grass and plantings 6. Eliminate water fountains, pools and water features


Wind to make the site less windy:1. Use extensive wind break like trees and

structures 2. Do not trim lower branches of tall trees


Wind to increase wind flow:1. Remove all obstruction (trees, structures, etc.) 2. Trim all lower branches of tall trees3. Limit all trees grow to 3 m4. 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

Cooling load

Indoor environment quality groups

HVACs’ systems main task is to maintain indoor optimal comfort standard with minimal energy consumption and minimal negative impact on the environment

Indoor environment quality groups

Indoor thermal comfort

• Thermal comfort can be maintained when the generated heat by human body (metabolism) is dissipated to the environment while keeping thermal symmetry with surroundings

Indoor thermal comfort

• StandardsASHRAE 55

They indicate that thermal environmental conditions must be acceptable to 80% or more of a building’s occupantsIt is not 100% due to an expected group of occupants’ dissatisfaction with thermal environment during a building operation

Why Maintaining thermal comfort standards in a building

• Thermal discomfort can lead to what is known as sick building syndrome (SBS)– Symptoms of sick building syndrome are eyes

irritations, nose dryness, sore throat, skin irritations and dryness and other general health problems

Metabolism

• What is Metabolism: The combustion of nutrient materials and the transport of substances between the body cells produces heat

Human Bodies

• Human body generate heats because we are warm blooded creatures

• Heat is produced depends on the metabolic rate

• Metabolic rate depends on human activity level• Some of the energy generated by muscular

activity will be translated into work and the excess energy will be dissipated as heat

Parameters of indoor thermal comfort

• influenced by various environmental conditions – indoor air temperature, – mean radiant temperature, – humidity – air speed, – and other personal like clothing

indoor air temperature

• The suitable indoor temperatures are between 20° and 22°C in winter and 26° to 27°C in summer when the ambient temperature is above 30°C

Mean radiant temperature

• Mean radiant temperature is known as the mean temperature of the surfaces that environs an inhabited space

• the difference between indoor air temperature and mean radiant temperature should not be greater than 2 ºC

• Therefore, a bright coloured or reflective external window blinds can be used to minimise the affect of mean radiant temperature

Humidity

• high humidity will prevent the evaporation of human skin sweats and respiration system vapours leading to discomfort

• low humidity produces dryness, itching and annoying static electric sparks which lead to discomfort

• humidity should be 40 to 70%.

Air speed

• During cold ambient conditions human bodies feel uncomfortable with air velocities above 0.15 m/s

• In summer and hot days human bodies are comfortable with higher velocities up to 0.6 m/s

Indoor air Quality IAQ

• Human beings as a condition of survival need a continuous supply of fresh and clean air.

• The need for air is relatively constant at 10-20 m3 per a day.


• Indoor air quality (IAQ) is defined as the essence or the nature of a conditioned air within a building or a structure. It is considered as the scenery of air that affects the building occupant’s health and their well being


• Or where the air is free from any known contaminations at a harmful level.

• In addition, whether this air satisfies thermal comfort, normal concentration of respiratory gases (oxygen and carbon dioxide) and acceptable limit of air pollutants.

Importance of IAQ

• Indoor air quality is a major concern for building designers, developers, operators, tenants and owners

• because human exposure to poor indoor air quality may cause a high health risk; like respiratory illness, fatigue, nausea and allergies.

• Indoor air quality affects occupants’ comfort, production, job satisfaction and performance.

Importance of IAQ

• Presently, humans become alert for potential health hazards associated with poor indoor air quality and its negative impact on human production. This is due to gaseous or substances contaminants as well as biological and building particles released into indoor air and inadequate building ventilation.

Why Poor IAQ Happens

• In addition poor indoor air quality can be exacerbated by the implementation of

• energy conservation strategies• the awareness of environmental issues

associated with energy usage• sealed buildings• the wide spread of photocopiers and printers

and • other resources of air contaminators

Factors affecting indoor air quality

Source

• Indoor air pollution sources: Indoor air contamination sources are internal and external.– Internal contamination sources are originated from

buildings internal envelope .– External contamination sources are originated from

outdoor sources. – The possible sources of contaminants and pollutants to

indoor air are: biological contaminants, building materials and substances, tobacco and smoke, cleaning products and maintenance, combustion sources, HVAC systems, and outside sources [69].

Building layout

• Physical buildings’ layout: Physical building layout including sight, climate, building materials and furnishings, moisture, processes and activities within the building controls air pressure differentials and the way how indoor air moves inside a building as well as how much fresh outdoor air enters the building.

• Thus a sudden change of air patterns can affect contaminant concentrations in different spaces within a building that have a direct impact on IAQ.

HVAC

• Buildings HVAC systems: The main function of buildings HVAC systems is to change the indoor air property of an occupied space of a building in order to provide thermal comfort for occupants.

• Poorly designed or maintained ventilation systems will cause indoor air quality problems.

• In general, economic and environmental restrictions control buildings’ ventilation system which has a direct impact on indoor air quality. For example in some cases buildings’ operators reduce the amount of fresh air through the building in order to reduce the cost of HVAC systems operation.

Buildings’ occupants:

• Buildings’ occupants are considered as a main source of contaminations.

• Buildings’ occupants’ contribution to contaminants and pollutants varies from one occupant to another as a result of different people having different metabolism rates and different activities such as cooking, washing, smoking, and body odour production.

Buildings’ occupants:

In some cases there are special groups of occupants that require different air purity standards and special conditioned air needs such as people with allergy, asthma, people with respiratory disease, people whose immune system is suppressed, people who require radiation therapy and people with contact lenses, etc

Types of contaminants and pollutants

• different from building to another depending on buildings’ nature and site such as building’s geographical position, building’s different materials which have been used during its construction or operation and traffic volume around it.

• the most common indoor pollutants are Carbone dioxide (CO2), Nitrous Oxide (N2O), Carbone Monoxide (CO), Nitrogen Dioxide (NO2), Sulphur Dioxide (SO2), Ozone (O3) and Radon.

indoor air problems can be eliminated or decreased by adopting

• Source control: This strategy is considered as the most cost effective approach in order to eliminate or to reduce IAQ problems. Methods of source control strategy are:– Pollutions and contaminations sources elimination

or reduction.– Pollutions and contaminations source cover or

concealment.– Buildings’ environment modifications e.g. indoor

humidity and temperature control.


• Buildings’ ventilation modifications: This strategy is effective when buildings are under ventilated and when the source of contaminations or pollutions are unknown. Methods of ventilation modifications are:– Diluting contaminations and pollutions with outdoor

fresh air.– Air pressure control to isolate pollutions or

contaminations.– Increasing the flow of outdoor air.


• Air cleaning process: This strategy is the most effective way to mitigate IAQ problems specially when combined it with either source control or ventilation. Moreover it is the only strategy can be used when the contamination sources are external. Methods of air cleaning processes are:– Particulate filtration.– Electrostatic precipitation.– Negative ion generation.– Gas sorption.


• Exposure control: This strategy is a set of administrative tactics can be used by buildings’ managerial team and operators to tackle IAQ problems by controlling occupants’ behaviours and activities. Examples of exposure control strategies are:– Scheduling contaminant-producing activities.– Relocating susceptible individuals.– Education and communication.

Energy conservation strategies

• Buildings energy consumption depends on building envelop, efficiency of HVAC and lighting systems, amount of required fresh air, internal and external heat gain and the building operation hours and maintenance.

Energy Reduction

• Buildings’ energy demand can be reduced by implementing certain strategies:– Operational management: This process is based

on rescheduling after hours activities and implementing of building management system (BMS) which enable building operators to control full or partial shutdown of building as well as control and regulate temperature in each space or zone to comply with ASHRAE comfort standards.

Energy Reduction

• Reduction of cooling loads (heat gain): This can be achieved throughout a set of procedures including solar radiation control which leads to a reduction of heat gain throughout the building envelop. Solar radiations control can be done using plants, vegetation and using light coloured exteriors walls.

Energy Reduction

• Buildings envelop modifications: The most common techniques used in building envelop modifications are installation of internal and external shading devices, double glazing and walls and roofs insulations.

Energy Reduction

• Equipment modifications: Examples of this strategy are installing heat recovery wheels, ventilation and radiant terminals.

Energy Reduction

• Employing passive and renewable energy cooling techniques: these techniques are free cooling techniques despite the fact of their high installation cost.

Solar Energy

Solar energy

• Solar energy is the energy produced by sun radiation. It is considered to be the most powerful, abundant, clean, environmental friendly and inexhaustible energy resource available to humans.

Solar energy

• In general all renewable energy resources derive their energy from the sun except geothermal and atomic energy. For example wind energy is derived by temperature and pressure variation that is created by sun’s affect. Hydro energy is a result of solar driven water cycle. Fossil fuels came as a result of drying process of organic matters by the sun’s radiation millions of years ago

Solar energy harvesting techniques

• Passive harvesting techniques: Examples of this technique are materials selections favourable for their thermal specifications, building designs with respect to natural air circulation and building oriented to the sun and sun light dispersing.

• Active harvesting techniques: Where solar collectors including electric photovoltaic panels and thermal collectors is used to convert solar radiation and heat into energy

Active harvesting techniques

• Solar thermal collectors: where solar radiations and heat is collected and used to produce heat. In other words it is defined as the conversion of solar radiation into thermal energy (heat).

• Solar photovoltaic (PV) modules: where solar radiations are converted directly into electricity (Direct Current) using photovoltaic cells (PV).

How much energy we can get

• The total annual energy output from a solar system Eₒ in (KWh) can be calculated :

– where η is energy conversion efficiency, Ac is solar panels surface area in (m²), G is the integrated solar irradiance over a year (W/m²).

key problem confronting a wider use of solar energy

• is the substantial variation of spatial and temporal in solar radiation pattern

• Requirements of high quality information and a comprehensive database

• The cost of solar energy production remains high compared to other production options.

• Solar resources intermittency especially in rainy days.

• Lack of support and grants

Solar collectors

• Solar thermal collectors: solar collectors are a type of heat exchange that is designed to absorb and convert solar radiation into usable or storable forms of energy

Solar thermal collectors

• solar collectors classified into three types of collectors:– low temperature collectors,– medium temperature collectors – high temperature collectors

Low temperature collectors

• The outlet temperature of these types of collectors normally ranges between 40 ºC and 90 ºC. – The most common type of low temperature

collectors is flat plate collectors (FPC). – Low temperature collectors are used for

processing heat e.g. to heat swimming pools and in HVAC systems. Normally collector’s heat medium is water and air.

Medium temperature collectors:

• outlet temperature of this type of collector is 60 ºC-250 ºC. – An example of medium temperature collectors is

evacuated tube collectors (ETC). – This technology is used on solar drying, solar

cooking and distillation. – Normally this type of collector’s heat medium is

also water and air.

High temperature collectors

• The outlet temperature of this type is more than 250 ºC. – An example of high temperature collectors are

parabolic dish reflector (PDR). – These types of collectors are used directly to

produce steam and then electricity. – heat medium is liquid fluoride salts

Market available solar thermal collectors

• Market available collectors’ fall into two categories – non-concentrated collectors where the collector

area is the same as solar radiations’ absorber area. – The second is concentrated collectors where

collectors have a concave reflecting surfaces or mirrors to intercept, magnifying and focus the sun’s radiation to smaller receiving areas in order to increase radiation flux

Non-concentred collectors

• These types of collectors collect solar irradiance without using magnifying or concentration mediums like mirrors

• Types of this family– flat plate collectors– evacuated tube collectors– compound parabolic concentrators.

Flat plate collectors

• Flat-plate collectors are the most common, cheapest and simplest type of solar thermal collector.

• These types of collectors were developed by Hottel and Whillier in the 1950s

Flat plate collectors FPC


• FPC consist from the followings– The first part is the absorber: This part of the

collector is a flat plate absorber of solar energy. – The absorber consists of pipes network which has a

direct contact with the absorbent background which is made from thin dark coloured metal sheet e.g. thermal polymers, aluminium and steels.

– Absorber plates are normally painted with special coatings, which is able to absorb and retain heat better than normal black paint.


• FPC consist from the followings– The Second part is the transparent cover (glazed):

The weatherproof absorbent box is covered by a transparent cover (glass) and filled with air cavity between the surfaces to prevent heat dissipation and to minimise radiation losses


• FPC consist from the followings– Third part is heat transport medium (fluid): A heat

transport fluid is used in order to remove heat from the absorber and then transfer it to the end user or a storage facility. Examples of these fluids are air, antifreeze, glycol-water and water. Fourth part is the heat insulation box: The absorber system is fitted in a box that is insulated to prevent heat loss to the surroundings.


• FPC Principle of work– Based on the law of blackbody radiation the

process starts by passing the sun light directly to the absorber plate through the glass cover, causing heat to the absorber. The heat is then removed by the transport fluids through the pipes network in the absorber box

– Flat plat collectors normally are installed at a fixed solar collection angle.


• Applications of FPC– This type of collector is commonly used to

generate hot water for residential buildings, space heating and cooling and to heat swimming pools’ water. The use of FPC in commercial buildings is limited to small businesses like a car wash, Laundromat and restaurant.

Evacuated tube collectors

• evacuated tube collectors consist of an array of parallel evacuated heat pipe tubes (EHPT) which are connected to the top header pipe or a heat exchanger manifold.


– Each heat tube is composed of a metal heat pipe that is connected to a dark coloured absorber plate. Absorber and the heat pipes are normally made from copper, due to its superior thermal conductivity

– Both components setup are surrounded by glass tube to prevent convection and conduction heat loss to surroundings, where the space between the tube and the absorber is evacuated

Evacuated Tube Collectors ETC

• ETC Principle of work– The heat process is achieved by transferring heat

into the header tube (heat exchanger manifold). – The sealed metal heat pipes contain a small

amount of fluids below atmospheric pressure. The low pressure fluids evaporate causing the hot gas to rise up in the heat pipes by convection

– Then the condensed fluid falls down the heat pipe by gravity, so the process starts again

Evacuated Tube Collectors ETC

• ETC Principle of work– Due to evacuated tube collectors tubular design it

is capable of collecting sun energy from different angles

Evacuate Tube Collectors ETC

• Applications of ETC– This type of collectors is commonly used in

cooking, commercial buildings’ water heating, solar cooling technologies (excludes desiccant) and electric power generation.

– Evacuated tube collectors (ETC) are the most efficient solar thermal collectors

Solar air collectors

• Solar air heat collectors are a type of collectors where sun radiations are harvested and used to heat air directly– This technology can be classified into two

categories: glazed and unglazed collectors

Glazed air collectors

• Glazed collectors are transparent (covered) collectors that have a top sheet and an insulated side and back panels to minimise heat loss to the environment

• air passes along the front or back of the absorber plate gaining heat directly from it

Un-Glazed air collectors

Air collectors

• the most common market available collectors that belong to this category are transpired solar air collectors

• Solar heat air collectors can be used directly for various applications or may be stored for later use. The most common applications for air glazed collectors are spaces heating and drying and it is also widely used in agriculture industry in crops drying.

Air collectors disadvantages

• However solar air heat collectors have two known disadvantages: low thermal capacity of air and low absorber to air heat transfer coefficient

Concentrated solar collectors

• Parabolic trough collectors• Parabolic trough collectors are a type of solar

energy collectors made from coated silver or polished aluminium (mirrors) which is shaped like the letter U as shown in the Figure


• They constructed and installed to form long parabolic mirrors with a flask tube (Dewar) running on its length at a focal point.

• The trough collectors can be oriented on a south south axis and have a sun tracking devices to rotate it in order to harvest the maximum possible sun irradiance


• Operation: Heat process in parabolic trough collectors is achieved by transferring heat from the absorber to the heat transport fluid (oil)

• Then the heated oil temperature increases to near 400 °C which can be used to generate steam

Selections

• The selection of suitable solar collectors depends on the climatic conditions, load requirements, costs, and output temperature.

HVAC

Heat ventilation and Air conditioning

Refrigeration

• Definition: The process of cooling of a bodies or fluids to temperature lower than those available in the surroundings at a particular time and place.– Note here in refrigeration cooling is involved but

refrigeration not exactly same as cooling• Cooling can be spontaneous and the final temperature

need to be lower than surroundings• Refrigeration is not spontaneous and the final

temperature should be lower than the surroundings.

Refrigeration

• Example of cooling process not refrigeration:– Cooling of s hot cup of coffee

• Here the final temperature cannot be lower than surrounding temperature

• Cooling of glass of water by adding ice here the final temperature will be lower than surroundings (refrigeration)

Air conditioning

• Air conditioning: is the treatment of air so to simultaneously control its temperature, moisture content, quality and circulation– In order it is

• required by occupants • a process• product in the space.

Application of refrigeration

• Food processing and preservation• Chemical and process industries• Comfort and industrial air conditioning

History of refrigeration

• Age of natural refrigeration– The beginning of 19th century

• Age of artificial refrigeration– From 19th century onwards

Refrigeration

• Natural Refrigeration methods– It is called natural because we relay in nature to provide

Refrigeration

– Use of natural ice, that is:– Transport from colder regions – Harvested in winter and stored for summer– Producing ice by nocturnal cooling

• nocturnal : The apparatus consisted of a shallow ceramic tray with a thin layer of water, placed outdoors with a clear exposure to the night sky

Refrigeration

• Natural Refrigeration methods– Use of evaporative cooling

• When water is evaporate to surroundings its provide cooling. Evaporative cooling is effective when surroundings is dry and useless on humid regions

– Cooling by salt solution • when we dissolve certain salts on water, the water

temperature will drop as a result of endothermic process. The quantity of cooling is too law.

Limitation of natural methods

• Depends on local conditions• Uncertainty due to dependence on weather• Difficult to produce large amount of

refrigeration• Not available to every body

Artificial refrigeration

• Classified into:– Non Cyclic :– Cyclic

Non Cyclic

– Non Cyclic :refrigeration is accomplished based on total loss refrigeration principle e.g. melting ice or sublimations of frozen carbon dioxide

– Example by melting ice, heat is transferred by convection from the warmer air inside a refrigerated space to the ice which absorbs heat, making the refrigerated space cooler than ambient.

– Non cyclic refrigeration is used on small scale applications e.g. portable coolers, workshops and laboratories.

Non Cyclic Refrigeration

– The principle portable coolers :The domestic ice box used to be made of wood with suitable insulation. Ice used to be kept at the top of the box, and low temperatures are produced in the box due to heat transfer from ice by natural convection. A drip pan is used to collect the water formed due to the melting of ice. The box has to be replenished with fresh ice once all the ice melts.

Cyclic refrigeration

• Cyclic refrigeration operates using compression and expansion of refrigerant e.g. chlorofluorocarbons (CFC) and Hydro chlorofluorocarbons (HCFC).

• Principle : Heat is removed from a cooled space and rejected to a higher temperature sink by means of work and inverse work that is carried out by a refrigerant.

Cyclic refrigeration

• Cyclic refrigeration is divided in two classifications: – vapour compression cycle refrigeration systems.

• Currently the dominant refrigeration and cooling systems worldwide are electrically driven vapour compression machines

– Gas cycle : similar to air conditioning used in air planes

History

• General electric (GE) introduced the first domestic refrigeration in 1911 in USA., followed by Frigidaire in 1915 and kelvinator in 1918.

• There are a rapid growth is attributed to the simultaneous development of:– Electric motors and compressors– Better shaft seals– Automatic control– Introducing of CFCs in 1930

Artificial refrigeration methods

• Artificial refrigeration methods classified into three categories based on there working principles

• vapour compression systems• vapour absorption systems• gas cycle systems

vapour compression systems

• The basis of modern refrigeration – It is the most dominant in refrigeration

• The vapour-compression uses a circulating liquid refrigerant as the medium which absorbs and removes heat from the space to be cooled and subsequently rejects that heat elsewhere


• Components are :– a compressor– a condenser– a thermal expansion valve (also called a throttle

valve)– and an evaporator.

Compressor

• The cooling process starts with stage 1 by entering (the compressor) where the circulating refrigerant enters the compressor as a saturated vapour and compressed to higher pressure and higher temperature (stage 2) to form a superheated vapour.– Saturated vapour: contains as little thermal energy

as it can without condensing– Superheated maximum temperature with

maximumpressure

Condenser

• The hot, compressed vapour is then in the thermodynamic state known as a superheated vapour and it is at a temperature and pressure at which it can be condensed with either cooling water or cooling air.

• That hot vapour is routed through a condenser where it is cooled and condensed into a liquid by flowing through a coil or tubes with cool water or cool air flowing across the coil or tubes phase (saturated liquid).

Condenser

– A saturated liquid contains as much thermal energy as it can without boiling (opposite of saturated vapour)

• This is where the circulating refrigerant rejects heat from the system and the rejected heat is carried away by either the water or the air (whichever may be the case).

Expansion Valve

• Afterwards the saturated liquid from the condenser is routed through the expansion valve, allowing its pressure and temperature to drop considerably.

Evaporator

• The cold mixture is then routed through the coil or tubes in the evaporator

• A fan circulates the warm air in the enclosed space across the coil or tubes carrying the cold refrigerant liquid

• That warm air evaporates the liquid part of the cold refrigerant mixture. At the same time, the circulating air is cooled and thus lowers the temperature of the enclosed space to the desired temperature

Cycle

• Then the evaporative refrigerant evaporates to the compressor to repeat the cycle

Advantages

• Vapour compression cycle is characterised by • its low mass flow rate• high coefficient of performance (COP)• low cold plate temperatures and the ability to

transport heat away from its source.

Commercial HVAC

• Commercial air conditioning may be provided by a variety of equipment ranging from low horsepower self-contained systems to the very large built-up central systems of several thousand ton capacity.

architect’s/HVAC engineer's responsibility to guide and advise

the customers the best option

Customer/user’s ultimate objective is to acquire and utilize an air conditioning system that will provide the most appropriate: performance on a whole of life basis, in terms of capital, operating, replacement and maintenance costs..

HVAC systems are importance to architectural design because

1. The success or failure of thermal comfort efforts is usually directly related to the success or failure of a building’s (HVAC) systems;

2. HVAC systems often require substantial floor space and/or building volume for equipment and distribution elements that must be accommodated during the design process;

3. HVAC systems require significant capital investments; 4. The HVAC system is responsible for large portion of

building operating costs.

Selection of different HVAC system designs and operational

• every building is unique in its design and operation. For instance residential apartments, shopping complex, office complex, hospital, hotel, airport or industry; all have different functional requirements, occupancy pattern and usage criteria.

Selection of different HVAC system designs and operational

• The geographical location of the building, ambient conditions, indoor requirements, building materials, dimensional parameters, aesthetic requirements, noise and environment issues need different treatment.

The selection of appropriate HVAC

1. Thermal Comfort : The internal environment of the buildings must be a major focus point in the HVAC system selection and this determined by: – The activity level– age– and physiology of each person affect the thermal

comfort requirements of that individual


2. Building Architecture: The HVAC system selection is influenced by the characteristics of the building such as:

– Purpose of the building– Type of building structure, orientation, geographical

location, altitude, shape, size and height – Materials and thickness of walls, roof, ceilings, floors

and partitions and their relative positions in the structure, types of glazing, external building finishes and colour as they affect solar radiation, shading devices at windows, overhangs, etc.;


3. Available Space: • Considerable space is needed for mechanical rooms to

house the HVAC equipment. In addition shaft spaces are required for routing ducts/pipes and other services e.g. electrical and plumbing work.

• Early liaison is therefore required with the project architect to proportion the building that would be occupied by HVAC systems, as this will have an impact on the size and cost of the building.


4. Building ceiling heights: • The HVAC designer must thoroughly evaluate

the ceiling space for air distribution ducts • Inadequate spaces to run ducts, probably

force the system designer to use decentralized or unitary air conditioning units.


5. Building Aesthetics • The HVAC layout should be complementary to the building

architecture. Often the requirements are stringent for example: – No equipment should be visible or should suitably blend with

environment– Size and appearance of terminal devices in ceiling shall harmonize

with lighting layout, fire sprinklers, detectors, communication systems and ceiling design;

– Acceptability of components obtruding into the conditioned space;– Accessibility for installation of equipment, space for maintenance;


6. Efficiency/Performance and Energy Use:• To assemble the best HVAC system, the efficiency,

performance, cost and energy use will be major considerations when selecting components for the system.

• The cost of the energy consumed by the components of the HVAC system is an important aspect of the system selection. Each component must use as little energy as possible and still meet the performance requirements.


7. Availability of water: • The places where water is Insufficient for the

demand, the only choice leans towards air-cooled equipment


7. Noise control:• Sufficient attenuation is required to minimize

equipment and air distribution noise. It is important to select low decibel equipment and define its location relative to the conditioned space.


8. Indoor environment and its control• Equipment and control design must respond

to close tolerances on temperature/humidity, cleanliness, indoor air quality etc.

• Zone control or individual control is important consideration for the anticipated usage patterns.


9. Delivery and Installation schedules HVAC designer must evaluate the equipment options that provide short delivery schedules and are relatively easy to install.


10. System flexibility: The HVAC designer need to consider the likelihood of space changes and future ezpansion.


11. Codes & Standards The selection of the HVAC system is often constrained by various local codes and ASHRAE standards.


12. Life cycle costs:Capital, running costs, maintenance costs, and plant replacement costs need to be taken into account so that the selected system demonstrates value for money to install and operate

Developments Preindustrial Era: prior 1800s where the building envelop was the principal means of...

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