MSc Management Of Built Environment HVAC PDF

MSc “Management of Built Environment” TECHNICAL ASSESSMENT OF BUILT ENVIRONMENT FUNDAMENTALS OF HVAC IN BUILDINGS Prof. Giancarlo PAGANIN  SUMMARY General objectives of the air-conditioning of buildings Basic principles...

MSc “Management of Built Environment” TECHNICAL ASSESSMENT OF BUILT ENVIRONMENT FUNDAMENTALS OF HVAC IN BUILDINGS Prof. Giancarlo PAGANIN  SUMMARY General objectives of the air-conditioning of buildings Basic principles of HVAC systems Types of systems and main components Prof.G.PAGANIN  General breakdown approach 1. Feed 2. Transformation Prof.G.PAGANIN 3. Distribution 4. Use-Terminals  Main goals To create and maintain in the built environment specified conditions of air temperature and humidity related to the Prof.G.PAGANIN external conditions; To control the air movement in the inhabited area; To ensure the desired air quality thanks to the air changes and/or air filtration; Check the air infiltration from the outside or unwanted air movement from a space to another space in the building;  Main goals The term “air conditioning” has gradually changed, from meaning just cooling to the total control of: Prof.G.PAGANIN Temperature Moisture in the air (humidity) Supply of outside air for ventilation Filtration of airborne particles Air movement in the occupied space. Source: McDowall R., Fundamentals of HVAC Systems, Elsevier, 2007  Indoor air quality Prof.G.PAGANIN Source: McDowall R., Fundamentals of HVAC Systems, Elsevier, 2007  Main processes 1. Heating —the process of adding thermal energy (heat) to the conditioned space for the purposes of raising or maintaining the temperature of the space. 2. Cooling —the process of removing thermal Prof.G.PAGANIN energy (heat) from the conditioned space for the purposes of lowering or maintaining the temperature of the space. 3. Humidifying —the process of adding water vapor (moisture) to the air in the conditioned space for the purposes of raising or maintaining the moisture content of the air.  Main processes 4. Dehumidifying —the process of removing water vapor (moisture) from the air in the conditioned space for the purposes of lowering or maintaining the moisture content of the air. Prof.G.PAGANIN 5. Cleaning —the process of removing particulates (dust, etc.) and biological contaminants (insects, pollen, etc.) from the air delivered to the conditioned space for the purposes of improving or maintaining the air quality.  Main processes 6. Ventilating —the process of exchanging air between the outdoors and the conditioned space for the purposes of diluting the gaseous contaminants in the air and improving or maintaining air quality, composition, and Prof.G.PAGANIN freshness. Ventilation can be achieved either through natural ventilation or mechanical ventilation. 7. Air Movement —the process of circulating and mixing air through conditioned spaces in the building for the purposes of achieving the proper ventilation and facilitating the thermal energy transfer.  The refrigeration cycle Prof.G.PAGANIN Source: McDowall R., Fundamentals of HVAC Systems, Elsevier, 2007  The refrigeration cycle Prof.G.PAGANIN Building Services Handbook, Roger Greeno, Fred Hall, Fred Hall, and Roger Greeno  Air treatment Prof.G.PAGANIN  Air treatment (ASHRAE diagram) Prof.G.PAGANIN  Terminology (Building Services Handbook, Roger Greeno, Fred Hall, Fred Hall, and Roger Greeno) The following is a glossary of some of the terminology used in air-conditioning design: Prof.G.PAGANIN Dew point – temperature at which the air is saturated (100% RH) and further cooling manifests in condensation from water in the air. Dry bulb temperature – temperature shown by a dry sensing element such as mercury in a glass tube thermometer (°C db).  Terminology (Building Services Handbook, Roger Greeno, Fred Hall, Fred Hall, and Roger Greeno) Moisture content – amount of moisture present in a unit mass of air (kg/kg dry air). Percentage saturation – ratio of the amount of moisture in the air compared with the moisture content of Prof.G.PAGANIN saturated air at the same dry bulb temperature. Almost the same as RH and often used in place of it. Relative humidity (RH) – ratio of water contained in air at a given dry bulb temperature, as a percentage of the maximum amount of water that could be held in air at that temperature.  Terminology (Building Services Handbook, Roger Greeno, Fred Hall, Fred Hall, and Roger Greeno) Latent heat – heat energy added or removed as a substance changes state, while temperature remains constant, e.g. water changing to steam at 100°C and atmospheric pressure (W). Prof.G.PAGANIN Sensible heat – heat energy which causes the temperature of a substance to change without changing its state (W). Wet bulb temperature – depressed temperature measured on mercury in a glass thermometer with the sensing bulb kept wet by saturated muslin (°C wb).  Air treatment (ASHRAE diagram) Prof.G.PAGANIN  Air treatment (ASHRAE diagram) Prof.G.PAGANIN  Air treatment (ASHRAE diagram) Prof.G.PAGANIN  Air treatment (ASHRAE diagram) Prof.G.PAGANIN  Air treatment (ASHRAE diagram) Prof.G.PAGANIN Prof.G.PAGANIN Source: McDowall R., Fundamentals of HVAC Systems, Elsevier, 2007 Prof.G.PAGANIN Source: McDowall R., Fundamentals of HVAC Systems, Elsevier, 2007 Prof.G.PAGANIN Source: McDowall R., Fundamentals of HVAC Systems, Elsevier, 2007 Prof.G.PAGANIN Source: McDowall R., Fundamentals of HVAC Systems, Elsevier, 2007  Air treatment Prof.G.PAGANIN Source: McDowall R., Fundamentals of HVAC Systems, Elsevier, 2007  Air treatment Prof.G.PAGANIN Source: McDowall R., Fundamentals of HVAC Systems, Elsevier, 2007  Air treatment Prof.G.PAGANIN  Basic types Air based systems They guarantee the management of sensible loads and latent loads through the input of only treated air Primary air and fan coil plants Prof.G.PAGANIN They guarantee the management of sensitive loads and latent loads through the supply of air to control latent loads (humidity) and local cooling with fan-coils for controlling the sensitive loads VRV VRF systems (variable refrigerant volume/flow)  Basic types Chilled beams Prof.G.PAGANIN Source: TRANE engineering newsletter  Refrigerants gases Refrigerants – CFCs and HCFCs Chlorofluorocarbon (CFC) – in the latter part of the nineteenth century and early part of the twentieth century, refrigerants in common use were ammonia (R717), methyl chloride (R40) and sulphur dioxide (R764). Leakage of these toxic and corrosive gases had Prof.G.PAGANIN very harmful even deadly effects, promoting research into the development and manufacture of less aggressive man-made chemical blends. This chlorine, fluorine and carbon (CFC) blend was colourless, odourless, non-flammable and non-toxic. For several decades it was used in domestic appliances, commercial and automotive applications until the 1980s when it was found that CFC leakage contributed significantly to depletion of the ozone layer and  Refrigerants gases Chloro-Fluorocarbons (CFCs with main gas Freon 11 - R11); have been eliminated from use in refrigeration plants (MONTREAL PROTOCOL on Substances that Deplete the Ozone Layer SIGNED ON 1987) Hydrochlorofluorocarbons (HCFCs, such as, for example, R22) which exhibit less stable molecules for Prof.G.PAGANIN the presence of hydrogen not substituted by chlorine or fluorine. These fluids should also be completely replaced by refrigerant fluids that do not present a hazard to ozone attack. Today, complex molecular HCFCs (R113, R114, R125, R134a, R143) are characterized by multiple carbon atoms and the presence of more unmodified hydrogen molecules. In some cases, ammonia (NH3) is used  (fan – coil) Prof.G.PAGANIN  (fan – coil) Prof.G.PAGANIN  4 pipes systems Prof.G.PAGANIN  references Kreider F., Handbook of Heating, Ventilation, and Air Conditioning, CRC Press LLC. 2001 Prof.G.PAGANIN McDowall R., Fundamentals of HVAC Systems, Elsevier, 2007 (polimi.it_risorse elettroniche_ebook)  General layout Prof.G.PAGANIN  General layout VAV Prof.G.PAGANIN  dampers Prof.G.PAGANIN  Fire dampers (fire compartments) Prof.G.PAGANIN  Air diffusers Prof.G.PAGANIN  Air diffusers Prof.G.PAGANIN  Air handling units (AHU) Prof.G.PAGANIN  Air handling units (AHU) Prof.G.PAGANIN  Air handling units (AHU) Prof.G.PAGANIN  Chillers (air condensated) Prof.G.PAGANIN  Cooling towers Prof.G.PAGANIN  Cooling towers Prof.G.PAGANIN  Cooling towers Prof.G.PAGANIN  Individual AC systems Prof.G.PAGANIN  absorption refrigeration units Prof.G.PAGANIN  absorption refrigeration units The working fluid in an absorption refrigeration system is a binary solution consisting of refrigerant and absorbent. Many working fluids are suggested in literature. A survey of absorption fluids suggests that, there Prof.G.PAGANIN are some 40 refrigerant compounds and 200 absorbent compounds available. However, the most common working fluids are: Water/NH3 LiBr/water. Source: P. Srikhirin et al. “A review of absorption refrigeration technologies” Renewable and Sustainable Energy Reviews 5 (2001) 343–372