HVAC Systems: Heating, Ventilation, and Air Conditioning PDF

HEATING, VENTILATION AND AIR CONDITIONING SYSTEMS (HVAC) 1.1 DEFINITION OF AIR-CONDITIONING It is the simultaneous control of the temperature, humidity, motion and purity of the air in a confined space. Refrigerant -A substance that produces a refrigerating effect while expanding or vaporizing as i...

HEATING, VENTILATION AND AIR CONDITIONING SYSTEMS (HVAC) 1.1 DEFINITION OF AIR-CONDITIONING It is the simultaneous control of the temperature, humidity, motion and purity of the air in a confined space. Refrigerant -A substance that produces a refrigerating effect while expanding or vaporizing as it circulates as a gas or liquid through a closed vapour-compression refrigeration system. -It picks up heat by evaporating at a low temperature and pressure and gives up heat by condensing at a higher temperature and pressure HEATING, VENTILATION AND AIR CONDITIONING SYSTEMS (HVAC) 1.1 DEFINITION OF AIR-CONDITIONING Common refrigerants: Hydrochlorofluorocarbon (HCFC) – HCFC 22, HCFC 123 Hydrofluorocarbon (HFC) – HFC 134a Obsolete Refrigerants: Dichlorodifluoromethane – Freon 12 Trichloromonofluoromethane – Freon 11 Chlorofluorocarbons – CFC 12 HEATING, VENTILATION AND AIR CONDITIONING SYSTEMS (HVAC) 1.1 DEFINITION OF AIR-CONDITIONING Functions of Air-Conditioning 1. Cooling and de-humidifying of air 2. Heating or humidifying of air 3. Cleaning of air or filtration 4. Circulation of air HEATING, VENTILATION AND AIR CONDITIONING SYSTEMS (HVAC) 1.1 DEFINITION OF AIR-CONDITIONING Air-Conditioning Standards 1. Cooling and de-humidifying- for summer cooling, temperatures of 70-80 deg F (20-24 deg C) and 50% relative humidity are a frequent design average. 2. Heating and humidifying- for winter cooling, temperatures of 70-75 deg F and relative humidity of 30%-35% are found most satisfactory. 3. Air motion – air velocity should average 15ft-25ft per minute measured 36” above floor HEATING, VENTILATION AND AIR CONDITIONING SYSTEMS (HVAC) 1.1 DEFINITION OF AIR-CONDITIONING Air-Conditioning Standards 4. Air Supply- a. 5 cuft. To 7-1/2 cuft. Of air per minute per person. In rooms where smoking is not allowed. b. 25 cuft. To 40 cuft. Of air per minute per person allowed in rooms where smoking is permitted. HEATING, VENTILATION AND AIR CONDITIONING SYSTEMS (HVAC) 1.1 DEFINITION OF AIR-CONDITIONING Methods of Cooling and De-humidifying 1. Passing the air through a spray of cold water (e.g. portacool) 2. Passing the air through coils containing cold water (evaporative cooler) 3. Passing the air through coils containing the refrigerant itself; in this case the coils are called “direct expansion” coils (window type ac, split type ac also DX systems) 4. Passing the air through a combination of sprays and coils (centralized) HEATING, VENTILATION AND AIR CONDITIONING SYSTEMS (HVAC) 1.1 DEFINITION OF AIR-CONDITIONING Cooling Capacity Tonner (TR)- 1 ton=12,000 British thermal unit (Btu)/hr Horsepower (HP)