Lecture Objectives:

• Finish with HVAC Systems

• Discuss Final Project

Building HVAC Systems (Primary and Secondary Building Systems)

AHU

Buildingenvelope

Cooling(chiller)

(or Gas)

Electricity

Gas

Heating(boilers)

Fresh air For ventilation

Distribution systems

Air transport

Secondary systems

Primarysystems

AHU – Air Handling Unit

HVAC systems affect the energy efficiency of the building as much as the building envelope

Integration of HVAC and building physics models

BuildingHeating/Cooling

SystemPlant

BuildingHeating/Cooling

SystemPlant

Load System Plant model

Integrated models

Qbuiolding Q

including

Ventilation

and

Dehumidification

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.

Air-conditioning in Air Handling Unit (AHU)

Compressorand Condenser

Roof top AHU

Gas/Electric Heater

to building

Fan

air from building

fresh air

Evaporator

filtermixing

hotwatercool

water

Return fan

Supply fan

flow control dampers

AHU

Fresh air

AHU schematic

Outdoor air To room

Exhaust From room

Processes in AHU presented in Psychrometric in psychrometric

OA Case forSummer in Austin

IA

MA

SA

Heat Recovery SystemsAir to Air Heat Exchanger

Plate heat exchangers

Enthalpy wheel Effectiveness ~60%

Effectiveness ~75%

Effectiveness ~50%

Ventilation Heat Recovery Systemsfor cooling and heating

Commercial buildings Residential buildings

Saving % - depends on how much ventilation we have in the building

Water Cooled Chiller

Outside air 95°F

Inside 75°FWater 42°F

BuildingWater 52°FWater 120°F

Water 100°F

Cooling tower

Chiller

Task: analyze COP for the whole yearand different locations

Solar hot water system

Geothermal Energy Systems(in combination with a cooling machine / heat pump)

Summer Winter

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.