Objective Revie the Cooling Cycle Learn about air distribution systems Define Building Zones Solve part of HW3

Zones In building How to define the zone in building Based on cooling/heating load requirement Based on ventilation requirement Based on use of buildings – different apartments deferent zones

Air Handling Units (AHU) Control of air Systems Provide conditioned air Heating, cooling, humidification, dehumidification Ventilation Provide fresh air, remove contaminated air

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

Air Handling Units (AHS) Equipment For AHU: Fans Cooling and heating coils Combustion heat exchangers Filtration Dampers, controls, mixing valves Humidification: steam/spray Dehumidification: cooling coil/desiccant Noise control

Control of air Systems Vary temperature, constant flow Constant temperature, vary flow Vary temperature, vary flow

Constant Temperature, Variable Volume On-off systems Residential and small commercial Vary volume by turning system on and off

Constant Air Volume Single zone constant air volume Fan always runs Vary temperature of air in response to space thermostat Single zone constant air volume with reheat Often used for precise humidity control Multizone constant air volume with reheat Good humidity control, flexible Not very efficient

Multizone constant air volume with reheat 55°F 62°F Require less cooling

Variable Air Volume Single zone VAV Multizone VAV Can also use reheat Varies air flow based on room thermostat Multizone VAV Central chilled air supply Zone thermostats control flow to each zone Can also use reheat Still need to provide adequate air flow for ventilation and for comfort Smaller energy penalty than CAV

VAV terminal

Multizone VAV 55°F Vary the flow

Reading Assignment Tao and Janis Chapter 3 Chapter 6 (from 6.1 to 6.7)

Homework Assignment 4 Table 1 Results of cooling load calculation and required amount of fresh air for ventilation Zone 1 Zone 2 Zone 3 Whole building Sensible cooling load for zone Time when the max cooling load appear 41000 Btu/h at 4 PM 45000 Btu/h at 6 PM 27000 Btu/h at 8 AM 92000 Btu/h Sensible cooling load for critical hour for whole building (6 PM) 37000 Btu/h 9000 Btu/h Latent cooling load (internal sources + infiltration) 5400 Btu/h 5200 Btu/h 16000 Btu/h Required amount of fresh air based on number of occupants 240 CFM (12 occupants) 520 CFM (26 occupants) 1000 CFM (50 occupants)

Homework Assignment 3 Supply air 55°F Recirculation air 76°F Fresh air (Dallas, TX) DBT=102°F