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by munir sharif

Published in: Education
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  2. 2. Introduction to HVAC HEATING : is process of increasing the temperature of the substance or a body or thermodynamic system heating system are design for colder climates system HEATING : Designing the system for cold climate Cooling : is process of decreasing temperature of the substance or body Cooling : Designing the system for warmer or Hot climate
  3. 3. Ventilation : is the process to maintains the indoor air quality Ventilation : extraction of air (exhaust + fresh air) Air conditioning :condition the air to provide human comfort by maintaining artificial temp, relative humidity, purifying the air through filter, noise level & by providing fresh air to improve indoor air quality Air conditioning is the process of altering the properties
  4. 4. PRINCIPAL OF AC SYSTEM Oxygen supply Heat removal Moisture removal Air motion Purify of air The goal is to keep it more comfortable inside the house than it is outside
  5. 5. Human comfort conditions Relative humidity 50% Temp 24.4◦C /76*F Dust filtration –fr Noise criteria Smell /odor This human comfort is define by ASHRAE American society for heating refrigeration and air condition engineering
  6. 6. Vapour compression cycle Most common refrigeration cycle in use today ► There are four principal control volumes involving these components: ►Evaporator ►Compressor ►Condenser ►Expansion valve Two-phase liquid-vapor mixture
  7. 7. All energy transfers by work and heat are taken as positive in the directions of the arrows on the schematic and energy balances are written accordingly. Process 4-1: two-phase liquid-vapor mixture of refrigerant is evaporated through heat transfer from the refrigerated space. Process 1-2: vapor refrigerant is compressed to a relatively high temperature and pressure requiring work input. Process 2-3: vapor refrigerant condenses to liquid through heat transfer to the cooler surroundings. Process 3-4: liquid refrigerant Two-phase liquid-vapor mixture
  8. 8. Vapor Absorption cycle  The vapour absorption refrigeration system is one of the method of producing refrigerating effect.  Uses heat energy instead of mechanical energy as in vapour compression system.  In the vapour absorption system the compressor is replaced by an absorber, a pump, a generator, and a pressure reducing valve.  These componet in vapour absorption system perform the same function as that of a compressor in vapour compression system
  9. 9. It mainly consists of three parts ANALYSER RECTIFIER HEAT EXCHANGER ANALYSER-When ammonia is vapourised in the generator some water is also vapourised,and flow into the condenser along with ammonia . if these unwanted particle are not removed before entering into the condenser,they will enter into the expansion valve where they freeze and choke the pipe line,so in order to remove the unwanted particle flowing in the condeser the analyser is used.
  10. 10. PSYCHOMETRIC CHART The subject which deals with the behavior of moist air is know as psychometric Psychometric is the science dealing with the physical laws of air-water mixtures. Psychometric chart contains relation between properties of air. The properties of mixture of air and water vapour are as follows
  11. 11. Properties of air Dry air : it is the mixture nitrogen and oxygen neglecting small percentage of other gases. Dry bulb temperature :it is the temperature of air measured by thermometer Wet Bulb temperature : it is the temperature of air measured by a thermometer whose bulb is covered with a wet wick or cloth and kept in current of moving air
  12. 12. Dew point temperature (change of phase): it is the temperature of the air when it is fully saturated and the moisture condenses on a surface. Relative Humidity : it is the ratio of the actual moisture present in the air to the maximum moisture the air can hold. Humidity ratio: describes the actual weight of water in an air-water vapour mixture also humidity ratio can be expressed as grains of moisture per pound of dry air.
  14. 14. WINDOW A/C Window air conditioners are one of the most commonly used and cheapest type of air conditioners. To install one of these units, you need the space to make a slot in the wall, and there should also be some open space behind the wall. Window air-conditioner units are reliable and simple-to- install solution to keep a room cool while avoiding the costly construction of a central air system. Better yet, when the summer heat dies down, these units can be easily removed for storage, and you can use the window sill for other purpose
  15. 15. Split A/c The split air conditioner comprises of two parts: the outdoor unit and the indoor unit. The outdoor unit, fitted outside the room, houses components like the compressor, condenser and expansion valve. The indoor unit comprises the evaporator or cooling coil and the cooling fan. For this unit you don’t have to make any slot in the wall of the room. Further, the present day split units have aesthetic looks and add to the beauty of the room. The split air conditioner can be used to cool one or two rooms
  16. 16. PACKAGE A/C The window and split air conditioners are usually used for the small air conditioning capacities up to 5 tons. The central air conditioning systems are used for where the cooling loads extend beyond 20 tons. The packaged air conditioners are used for the cooling capacities in between these two extremes. The packaged air conditioners are available in the fixed rated capacities of 3,5, 7, 10 and 15 tons. These units are used commonly in places like restaurants, telephone exchanges, homes, small halls, etc.
  17. 17. Central a/c The central air conditioning plants or the systems are used when large buildings, hotels, theaters, airports, shopping malls etc. are to be air conditioned completely. The window and split air conditioners are used for single rooms or small office spaces. If the whole building is to be cooled it is not economically viable to put window or split air conditioner in each and every room. Further, these small units cannot satisfactorily cool the large halls, auditoriums, receptions areas etc.