Lecture Objectives: Model processes in AHU –Use eQUEST predefined models –Use detail modeling Define your topics for your final project

Where to look for info about eQUEST simulation tool You will find more info about eQUEST at: eQUEST help file User manual Detail manual eQUEST user blog

eQUEST HVAC Models Predefined configuration (no change) Divided according to the cooling and heating sources Details in e quest help file: For example: DX Coils No 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 Coils Furnace 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.

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

Schematic for model of simple air handling unit 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:

Cooling coil model To enable coupling of air handling unit model with the chiller model We need cooling coil model: Models gives a relationship between the supply temperature (T ref_in ) and return temperature (T ref_out ) of the circulating fluid for a given mass flow rate (m ref ) of this fluid thorough the cooling coil E = f(T air_in,w air_in,T r_in, m air,m ref ) Also, it depends on the cooling coil geometry and type of circulating fluid (water or refrigerant) The cooling coil effectiveness (E) describes this relationship: Air Cooling coil m air m ref T r_in T r_out T air_in w air_in T air_out w air_out

Cooling coil model - water cooled E =  = f(T air_in,w air_in,T r_in, m air,m ref ) m w =m ref, m a =m air UA - product of heat transfer coefficient and coil area (property of coil - several page long model) Physical based models based on heat transfer theory

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:

Integration of HVAC and building physics models Building Heating/Cooling System Plant Load-System-Plant model does not work in cases when HVAC components radiate to other surfaces We have to use Integrated models: T w_out m w, T w_in External weather parameters T surrounding surfaces T surrounding surfaces Q rad_plant Solve simultaneously system of equation or use iterative procedure.

Final project topics: Software based Energy analysis of building form Integrated design course, Envelope analysis of glass buildings …. Detail Modeling (your model) Heat recovery systems, Economizers, Water cooled chiller, Geothermal heat pump, Solar hot water systems, Mass transfer (moisture, ozone, VOCs,…) Vented cavity walls - exam problem …. Your ideas