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Heating and Air Conditioning


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This is an overview of introduction of heating and air conditioning condition sytem in the application of civil and architectural works.

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Heating and Air Conditioning

  1. 1. Heating and Air-Conditioning Fundamentals A lecture series of Prof. Tomas Ucol-Ganiron Jr CE 331-Environmental 1 Control system
  2. 2. Objectives• Describe the difference between the high and low sides of the system• List the major heating and air- conditioning parts and describe their operation CE 331-Environmental 2 Control system
  3. 3. Sources of Heat• The system adds heat in the winter • Removes it in the summer• Sources of heat • Passengers • Outside air • Road • Engine • Catalytic converter • Sunlight CE 331-Environmental 3 Control system
  4. 4. Heating• Engine coolant is routed to heater core • Air passes over fins of the heater core CE 331-Environmental 4 Control system
  5. 5. Air Distribution System• Moves heat between different locations • Controls air volume, temperature, quality, and location• Plenum housing: case assembly • Combined or split• Air doors • Open and close to control air flow• Carbon air filter • Often replaced with screens• Control head: relays A/C system demands CE 331-Environmental 5 Control system
  6. 6. Air Conditioning• Air in passenger compartment is cooled, dried, and circulated • Heat is removed from inside to outside• Modern cars get better freeway fuel economy with windows up and air-conditioning on • Above 40 mph: more gas used with windows down CE 331-Environmental 6 Control system
  7. 7. Air-Conditioning Principles• Must be a transfer of heat for refrigerant to change state • Liquid absorbs heat as changes to gas • Vapor releases heat as changes to liquid CE 331-Environmental 7 Control system
  8. 8. Heat Transfer• Heat flows to anything with less heat • Convection • Heat rises • Heat always flows from hot to cold • Radiation • Example: heat from the sun • Evaporation • Moisture absorbs heat as it is vaporized • Example: perspiration CE 331-Environmental 8 Control system
  9. 9. Humidity• Low humidity • Permits heat to be taken away from the human body • Evaporation and perspiration• High humidity • Makes evaporation difficult • People feel as comfortable at 79°F with 30% humidity as at 72°F at 90% humidity CE 331-Environmental 9 Control system
  10. 10. States of Matter• Common matter exists in three states depending on temperature • Solid • Liquid • Gas• Solid heated above freezing melts • Becomes a liquid CE 331-Environmental 10 Control system
  11. 11. Latent Heat• Sensible heat • Goes into matter • Results in temperature increase• Latent heat • Extra heat required for matter to change state • Cannot be recorded on a thermometer• Additional concepts • Quantity of heat • Vaporization • Condensation CE 331-Environmental 11 Control system
  12. 12. CE 331-Environmental 12 Control system
  13. 13. Air-Conditioning System Operation• Closed system • Four major devices • Compressor • Condenser • Evaporator • Metering device • Refrigerant circulates among devices • Changing pressure and state of refrigerant regulates cooling cycle operation • Four stages: compression, condensation, expansion, and vaporization CE 331-Environmental 13 Control system
  14. 14. Absorbing Heat• Process • Liquid refrigerant is circulated to the evaporator • Loses pressure as it exits the metering device • Absorbs heat from inside of car • Boils and vaporizes • Pressurized again • Gives off heat to outside air • Each cycle through evaporator absorbs at least 25° of heat from air blowing across it CE 331-Environmental 14 Control system
  15. 15. Reducing Humidity• Sources • Outside air • Breathing of passengers• Moisture in the air condenses on evaporator fins • Drained off through the floor as water• System does not cool air as much when humidity is high• Defroster operation • Dried cool air moves through heater core before it is blown onto the windshield CE 331-Environmental 15 Control system
  16. 16. Compressing the Refrigerant• Vaporized refrigerant pulled from evaporator to compressor • Compressors are driven by a belt from the crankshaft • Pressurizes heated refrigerant, increasing its temperature• Compressor clutch • Electromagnetic clutch connects and disconnects from the crankshaft pulley CE 331-Environmental 16 Control system
  17. 17. CE 331-Environmental 17 Control system
  18. 18. Home Cooling
  19. 19. Humidity in air• Relative Humidity • A measure of much water is in the air relative to the maximum amount of air can heat at that temperature. CE 331-Environmental 19 Control system
  20. 20. CE 331-Environmental 20 Control system
  21. 21. Principle A. Expansion Valve B. Compressor CE 331-Environmental 21 Control system
  22. 22. Arrangement CE 331-Environmental 22 Control system
  23. 23. TYPES OF AIR CONDITIONERS• Room air conditioners• Central air conditioning systems• Heat pumps• Evaporative coolers CE 331-Environmental 23 Control system
  24. 24. Air Conditioning CE 331-Environmental 24 Control system
  25. 25. Room air conditioner• Room air conditioners cool rooms rather than the entire home.• Less expensive to operate than central units• Their efficiency is generally lower than that of central air conditioners.• Can be plugged into any 15- or 20-amp, 115-volt household circuit that is not shared with any other major appliances CE 331-Environmental 25 Control system
  26. 26. CE 331-Environmental 26 Control system
  27. 27. Central Air conditioning• Circulate cool air through a system of supply and return ducts. Supply ducts and registers (i.e., openings in the walls, floors, or ceilings covered by grills) carry cooled air from the air conditioner to the home.• This cooled air becomes warmer as it circulates through the home; then it flows back to the central air conditioner through return ducts and registers CE 331-Environmental 27 Control system
  28. 28. Types of Central AC• split-system • an outdoor metal cabinet contains the condenser and compressor, and an indoor cabinet contains the evaporator• Packaged • the evaporator, condenser, and compressor are all located in one cabinet CE 331-Environmental 28 Control system
  29. 29. Large air conditioning systems• Outside air is drawn in, filtered and heated before it passes through the main air conditioning devices. The colored lines in the lower part of the diagram show the changes of temperature and of water vapor concentration (not RH) as the air flows through the system. CE 331-Environmental 29 Control system
  30. 30. Total Air Conditioning CE 331-Environmental 30 Control system
  31. 31. • Variable fresh air mixer and dust and pollutant filtration.• Supplementary heating with radiators in the outer rooms and individual mini heater and• Humidifier in the air stream to each room. CE 331-Environmental 31 Control system
  32. 32. Sizing Air Conditioners• how large your home is and how many windows it has;• how much shade is on your homes windows, walls, and roof;• how much insulation is in your homes ceiling and walls;• how much air leaks into your home from the outside; and• how much heat the occupants and appliances in your home generate CE 331-Environmental 32 Control system
  33. 33. Energy Consumption• Air conditioners are rated by the number of British Thermal Units (Btu) of heat they can remove per hour. Another common rating term for air conditioning size is the "ton," which is 12,000 Btu per hour.• Room air conditioners range from 5,500 Btu per hour to 14,000 Btu per hour. CE 331-Environmental 33 Control system
  34. 34. Energy Efficiency• Todays best air conditioners use 30% to 50% less energy than 1970s• Even if your air conditioner is only 10 years old, you may save 20% to 40% of your cooling energy costs by replacing it with a newer, more efficient model CE 331-Environmental 34 Control system
  35. 35. Energy Efficiency• Rating is based on how many Btu per hour are removed for each watt of power it draws• For room air conditioners, this efficiency rating is the Energy Efficiency Ratio, or EER• For central air conditioners, it is the Seasonal Energy Efficiency Ratio, or SEER CE 331-Environmental 35 Control system
  36. 36. Room Air Conditioners• Built after January 1, 1990, need have an EER of 8.0 or greater • EER of at least 9.0 if you live in a mild climate • EER over 10 for warmer climates CE 331-Environmental 36 Control system
  37. 37. Central AC• National minimum standards for central air conditioners require a SEER of • 9.7 for single-package and • 10.0 for split-systems • Units are available with SEERs reaching nearly 17 CE 331-Environmental 37 Control system
  38. 38. Energy Saving Methods• Locate the air conditioner in a window or wall area near the center of the room and on the shadiest side of the house.• Minimize air leakage by fitting the room air conditioner snugly into its opening and sealing gaps with a foam weather stripping material. CE 331-Environmental 38 Control system
  39. 39. Numerical Problem• A EER from 5.0 to 9 saving and pay back period CE 331-Environmental 39 Control system