Objectives

• Finish with Multizone Systems

• Review/Learn about HVAC Configurations

• Learn about cooling towers

Multizone Systems

Single zone CAV

Single zone multi-room CAV

Multi zone CAV with Reheater

Duct reheat unit

Multizone CAV Dual Duct System

Dual duct terminal (Mixing box)

Single zone VAV

Multi zone VAV

VAV box

Multi zone VAV with Reheater

CAV Dedicated Outdoor Air System (DOAS)

with Fan Coil Units

100%OA Exhaust

Fan coil units for heating and cooling

For ventilation and humidity control

Fan Coil Units

Fan coil Units can be combined with mechanical ventilation or rely on infiltration

VAV Dedicated Outdoor Air System (DOAS)

with occupancy sensors

100%OA Exhaust

Fan coil units for heating and cooling

For ventilation and humidity control

VAV box VAV box

CO2 CO2

Fan Terminal Units Same as fan coil

Can be with or without recirculation

HVAC Systems

Single zone Multi zone

VAVCAV VAV CAVAll Hydroinicthat relay on infiltration

With and without reheaters

DOAS with fan coils

With reheaters

Dual duct

Dual duct DOAS with

fan coils

With and without humiditycontrol

This is not the complete list !

Cooling towes

• Similarity and difference between • Evaporative coolers and • Cooing towers

Cooling Tower

• Similar to an evaporative cooler, but the purpose is often to cool water• Widely used for heat rejection in HVAC systems• Also used to reject industrial process heat

Air Washer

• Sprays liquid water into air stream

• Typically, air leaves system at lower temperature and higher humidity than it enters

Schematic

Cooling Tower

Solution

• Can get from Stevens diagram (page 272)

• Can also be used to determine• Minimum water temperature• Volume of tower required

Real World Concerns

• We need to know mass transfer coefficients• They are not typically known for a specific direct-

contact device• Vary widely depending on packing material, tower

design, mass flow rates of water and air, etc.• In reality, experiments are typically done for a

particular application

Summary

• Heat rejection is often accomplished with devices that have direct contact between air and water• Evaporative cooling

• Can construct analysis of these devices• Requires parameters which need to be measured

for a specific system