Lecture Objectives: Discuss the exam problems Answer question about HW 3 and Final Project Assignments Building-System-Plant connection –HVAC Systems

Building HVAC Systems (Primary and Secondary Building Systems) AHU Building envelope Cooling (chiller) (or Gas) Electricity Gas Heating (boilers) Fresh air For ventilation Distribution systems Air transport Secondary systems Primary systems AHU – Air Handling Unit HVAC systems affect the energy efficiency of the building as much as the building envelope

Air-conditioning in Air Handling Unit (AHU) Compressor and Condenser Roof top AHU Gas/Electric Heater to building Fan air from building fresh air Evaporator filter mixing hot water cool water Return fan Supply fan flow control dampers AHU Fresh air AHU schematic Outdoor air To room ExhaustFrom room

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?

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

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:

eQUEST HVAC Models Predefined configuration (no change) Divided according to the cooling and heating sources Details in e quest help file: For example: DX CoilsNo Heating –Packaged Single Zone DX (no heating) Packaged single zone air conditioner with no heating capacity, typically with ductwork. –Split System Single Zone DX (no heating) Central single zone air conditioner with no heating, typically with ductwork. System has indoor fan and cooling coil and remote compressor/condensing unit. –Packaged Terminal AC (no heating) Packaged terminal air conditioning unit with no heating and no ductwork. Unit may be window or through-wall mounted. –Packaged VAV (no heating) DX CoilsFurnace Packaged direct expansion cooling system with no heating capacity. System includes a variable volume, single duct fan/distribution system serving multiple zones each with it's own thermostatic control. –Packaged Single Zone DX with Furnace Central packaged single zone air conditioner with combustion furnace, typically with ductwork. –Split System Single Zone DX with Furnace Central single zone air conditioner with combustion furnace, typically with ductwork. System has indoor fan and cooling coil and remote compressor/condensing unit. –Packaged Multizone with Furnace Packaged direct expansion cooling system with combustion furnace. System includes a constant volume fan/distribution system serving multiple zones, each with its own thermostat. Warm and cold air are mixed for each zone to meet thermostat control requirements.