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  2. Heat pump and refrigeration cycle - Wikipedia

    en.wikipedia.org/wiki/Heat_pump_and...

    Thermodynamic heat pump cycles or refrigeration cycles are the conceptual and mathematical models for heat pump, air conditioning and refrigeration systems. [1] A heat pump is a mechanical system that transmits heat from one location (the "source") at a certain temperature to another location (the "sink" or "heat sink") at a higher temperature ...

  3. Air changes per hour - Wikipedia

    en.wikipedia.org/wiki/Air_changes_per_hour

    Air changes per hour, abbreviated ACPH or ACH, or air change rate is the number of times that the total air volume in a room or space is completely removed and replaced in an hour. If the air in the space is either uniform or perfectly mixed, air changes per hour is a measure of how many times the air within a defined space is replaced each hour.

  4. Glossary of HVAC terms - Wikipedia

    en.wikipedia.org/wiki/Glossary_of_HVAC_terms

    The hourly ventilation rate divided by the volume of a space. For perfectly mixed air or laminar flow spaces, this is equal to the number of times per hour that the volume the space is exchanged by mechanical and natural ventilation. Also called air change rate or air exchange rate. Abbreviated ACH or ac/hr. air conditioner

  5. Heating, ventilation, and air conditioning - Wikipedia

    en.wikipedia.org/wiki/Heating,_ventilation,_and...

    Too high of an air change rate may be uncomfortable, akin to a wind tunnel which has thousands of changes per hour. The highest air change rates are for crowded spaces, bars, night clubs, commercial kitchens at around 30 to 50 air changes per hour. [22] Room pressure can be either positive or negative with respect to outside the room.

  6. Heat recovery ventilation - Wikipedia

    en.wikipedia.org/wiki/Heat_recovery_ventilation

    Diagramatic operation of a thermal wheel Ljungström Air Preheater by Swedish engineer Fredrik Ljungström (1875–1964). A thermal wheel, also known as a rotary heat exchanger, or rotary air-to-air enthalpy wheel, energy recovery wheel, or heat recovery wheel, is a type of energy recovery heat exchanger positioned within the supply and exhaust air streams of air-handling units or rooftop ...

  7. Coefficient of performance - Wikipedia

    en.wikipedia.org/wiki/Coefficient_of_performance

    The coefficient of performance or COP (sometimes CP or CoP) of a heat pump, refrigerator or air conditioning system is a ratio of useful heating or cooling provided to work (energy) required. [1] [2] Higher COPs equate to higher efficiency, lower energy (power) consumption and thus lower operating costs. The COP is used in thermodynamics.

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  9. Vapor-compression refrigeration - Wikipedia

    en.wikipedia.org/wiki/Vapor-compression...

    A representative pressure–volume diagram for a refrigeration cycle. Vapour-compression refrigeration or vapor-compression refrigeration system (VCRS), [1] in which the refrigerant undergoes phase changes, is one of the many refrigeration cycles and is the most widely used method for air conditioning of buildings and automobiles.