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Lecture Objectives:

Lecture Objectives:. Specify Exam Time Finish with HVAC systems HW3 Introduce Projects 1 & 2 eQUEST other options. Equipment Selection example. Need 1.2 ton Of water cooling 1 ton = 12000 Btu/h. Example Available capacity as function of evaporator and condenser temperature.

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Lecture Objectives:

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  1. Lecture Objectives: • Specify Exam Time • Finish with HVAC systems • HW3 • Introduce Projects 1 & 2 • eQUEST • other options

  2. Equipment • Selection • example • Need 1.2 ton • Of water cooling • 1 ton = 12000 Btu/h Example Available capacity as function of evaporator and condenser temperature • Capacity is 1.35 ton • only for: • 115 F air condenser temp • 50 F of water temperature

  3. Modeling of Chiller The consumed electric power [KW] under any condition of load Chiller model acronyms: Available capacity as function of evaporator and condenser temperature CAPacity as Function of Temperature Full load efficiency as function of condenser and evaporator temperature Energy Input Ratio as Function of Temperature Efficiency as function of percentage of load Energy Input Ratio as Function of Part Load Ratio Part load: Part Load Ratio

  4. HW3Chiller model: COP= f(TOA , Qcooling , chiller properties) Chiller data: QNOMINAL nominal cooling power, PNOMINAL electric consumption forQNOMINAL The consumed electric power [KW] under any condition Available capacity as function of evaporator and condenser temperature Cooling water supply Outdoor air Full load efficiency as function of condenser and evaporator temperature Efficiency as function of percentage of load Percentage of load: The coefficient of performance under any condition:

  5. Roof top AHU fresh air filter mixing Fan air from building to building Evaporator Gas/Electric Heater Air-conditioning in Air Handling Unit (AHU) AHU AHU schematic Exhaust From room Return fan flow control dampers Supply fan Compressorand Condenser Fresh air To room Outdoor air hotwater coolwater

  6. Processes in AHU presented in Psychrometric in psychrometric Case for Summer in Austin OA MA IA SA

  7. Building-System-Plant HVAC System (AHU and distribution systems) Plant (boiler and/or Chiller) Building

  8. Building Heating/Cooling System Plant Integration of HVAC and building physics models Load System Plant model Building Qbuiolding Heating/Cooling System Q including Ventilation and Dehumidification Plant Integrated models

  9. System Models:Schematic of simple air handling unit (AHU) Mixing box m - mass flow rate [kg/s], T – temperature [C], w [kgmoist/kgdry air], r - recirculation rate [-], Q energy/time [W]

  10. Energy and mass balance equations for Air handling unit model – steady state case The energy balance for the room is given as: mS is the supply air mass flow rate cp- specific capacity for air, TRis the room temperature, TS is the supply air temperature. The air-humidity balance for room is given as: wRand wS are room and supply humidity ratio - energy for phase change of water into vapor The energy balance for the mixing box is: ‘r’ is the re-circulated air portion, TO is the outdoor air temperature, TM is the temperature of the air after the mixing box. The air-humidity balance for the mixing box is: wOis the outdoor air humidity ratio and wM is the humidity ratio after the mixing box The energy balance for the heating coil is given as: The energy balance for the cooling coil is given as:

  11. Project 1:Use eQUEST softwareto model an example buildingUse it in simple and detailed modes

  12. Project 2:HVAC Topics

  13. Heat Recovery SystemsAir to Air Heat Exchanger Plate heat exchangers Effectiveness ~50% Effectiveness ~75% Effectiveness ~60% Enthalpy wheel

  14. Ventilation Heat Recovery Systemsfor cooling and heating Commercial buildings Residential buildings Saving % - depends on how much ventilation we have in the building

  15. Water Cooled Chiller Chiller Cooling tower Building Water 120°F Water 52°F Outside air 95°F Water 100°F Inside 75°F Water 42°F Task: analyze COP for the whole year and different locations

  16. Solar hot water system

  17. Geothermal Energy Systems(in combination with a cooling machine / heat pump) Winter Summer In the summer, the earth acts as a cooling tower. The Cooling Machine loads the loop with heat, sending warmed water to be cooled by the earth In the winter, the earth acts as the boiler. The Heat Pump extracts heat from the loop, sending cooled water to be warmed by the earth.

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