# Lecture Objectives: Final discussion about HW3 Introduce more final project topics Continue with HVAC Systems.

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Lecture Objectives: Final discussion about HW3 Introduce more final project topics Continue with HVAC Systems

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

Refrigeration Cycle T outdoor air T cooled water Cooling energy (evaporator) Released energy (condenser) - What is COP? - How the outdoor air temperature affects chiller performance?

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

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

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

Energy and mass balance equations for Air handling unit model – steady state case m S is the supply air mass flow rate c p - specific capacity for air, T R is the room temperature, T S is the supply air temperature. w R and w S are room and supply humidity ratio - energy for phase change of water into vapor The energy balance for the room is given as: The air-humidity balance for room is given as: The energy balance for the mixing box is: ‘r’ is the re-circulated air portion, T O is the outdoor air temperature, T M is the temperature of the air after the mixing box. The air-humidity balance for the mixing box is: w O is the outdoor air humidity ratio and w M 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:

Non-air system Radiant panel heat transfer model

T OA water Building users (cooling coil in AHU) T CWR = 11 o C T CWS =5 o C Evaporation at 1 o C T Condensation = T OA + ΔT What is COP for this air cooled chiller ? COP is changing with the change of T OA Example of Plant Models: Chiller P electric (  ) = COP (  ) x Q cooling coil (  )

Chiller model: COP= f(T OA, Q cooling, chiller properties) Chiller data: Q NOMINAL nominal cooling power, P NOMINAL electric consumption for Q NOMINAL Cooling water supplyOutdoor 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: The consumed electric power [KW] under any condition Available capacity as function of evaporator and condenser temperature

Example of HVAC system in eQUEST

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