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Published byRosamond Letitia Wilkerson Modified over 9 years ago

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

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Additional final project topics New EE&RC Design by JACOBS and Ennead Architects http://www.engr.utexas.edu/eerc Skylight Façade Systems Loads ….

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

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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?

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

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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

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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

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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:

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Non-air system Radiant panel heat transfer model

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The total cooling/heating load in the room The energy extracted/added by air system The energy extracted/added by the radiant panel: T he radiant panel energy is: The energy extracted/added by the radiant panel is the sum of the radiative and convective parts:

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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 ( )

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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

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Example of HVAC system in eQUEST

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