Air conditioning systems - BasicA/COperation 1...

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1 Mobile Air Conditioning Basic A/C Operation
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2 System Components All systems contain six major components: Compressor to circulate the refrigerant. Condenser to transfer heat to ambient air Receiver dryer or accumulator to store reserve  refrigerant, contain the desiccant, and filter  refrigerant Expansion device to control amount of refrigerant  entering evaporator Evaporator to transfer heat from in-vehicle air to the  refrigerant Lines and hoses to connect these parts together     and the refrigerant.
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3 Automotive A/C Systems 2 primary systems used to control  evaporator pressure and temperature: TXV systems (thermal or thermostatic  expansion valve) OT systems (orifice tube) Fixed  Variable 
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4 Low Side Operation Goal is to provide constant evaporator  temperature of 32 degrees Refrigerants have low boiling points When liquid boils, it absorbs large amounts  of heat Amount of heat absorbed in evaporator is  proportional to amount of refrigerant boiled
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5 Low Side Components Expansion device Evaporator Accumulator (if equipped)
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6 Expansion Devices The expansion device separates the high side from  the low side and provides a restriction for the  compressor to pump against. There are two styles of expansion devices: The TXV can open or close to change flow. It is  controlled by the superheat spring, thermal bulb that  senses evaporator outlet temperature, and  evaporator pressure Most OTs have a fixed diameter orifice
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7 A TXV controls the refrigerant flow from the high pressure side to the evaporator. A receiver dryer is mounted in the liquid line of all TXV systems. TXV System Animation: A/C Systems, TXV
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8 An OT controls the refrigerant flow from the high pressure side to the evaporator. An accumulator is mounted in the suction line of all OT systems. Animation: A/C Systems, OT OT System
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9 Thermal Expansion Valves, TXVs Variable valve that can change size of  opening in response to system load Opens or closes depending on  evaporator pressure and temperature
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10 Thermal Expansion Valves, TXVs The three major types of expansion valves: Internally balanced TXVs are the most common. Externally balanced TXVs are used on some larger evaporators. Block valves route the refrigerant
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This note was uploaded on 11/20/2011 for the course MECHANICAL 12345 taught by Professor Ahmed during the Spring '11 term at Alexandria Technical College.

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Air conditioning systems - BasicA/COperation 1...

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