Classification of air conditioning systems Prof Dr M

Classification of air conditioning systems Prof. Dr. M. M. Nasr Professor of refrigeration and air conditioning Minia university

Classification of air conditioning systems: • Based on the fluid media used in thermal distribution system, air conditioning systems can be classified as: • 1. All air systems • 2. Air- water systems • 3. All water systems • 4. Unitary refrigerant based systems • • Selection of a suitable air conditioning system depends on: • 1. Capacity, performance and spatial requirements • 2. Initial and running costs • 3. Required system reliability and flexibility • 4. Maintainability • 5. Architectural constraints

1. All-air systems System Advantages Disadvantages All Air � Central equipment location � Duct clearance � No piping in occupied area � Large ducts - space � Use of outside air (free cooling) � Air balancing difficulties � Easy seasonal change � Heat recovery possible

2. Air-water systems System Air Water Advantages � Individual room control � Separate secondary heating/cooling � Less space for ducts � Smaller HVAC central equipment � Central filter, humidification Disadvantages � Changeover if only two pipes � Operating complex if two pipes � Control is numerous � Fan coil clearance problem � No-shut off for primary air � High pressure for induction � Four pipe system is too expensive

3. All-water systems System Advantages All Water � Less space � Locally shutoff (individual control) � Quick pull down � Good for existing buildings Disadvantages � More maintenance in occupied area � Coil cleaning difficulties � Filter � Open window for IAQ

4 -Unitary and hybrid systems • These systems are factory assembled and tested as per standard specifications, and are available in the form of package units of varying capacity and type. • System Unitary Advantages � Individual room control � Simple and inexpensive � Independent of other buildings � Manufacturer made it ready Disadvantages � Limited performance � No humidity control (general) � More energy (low efficiency) � Control of air distribution � Filter � Overall appearance

ALL - AIR SYSTEMS • As the name implies, in an “all – air” system air is used as the media that transports energy from the conditioned space to the A/C plant. • The system is categorized by the use of air-handling units (AHU) or roof top packages (RTP) to condition air. • A schematic arrangement of an All-Air system with its major components is shown below.

“All-Air” systems are classified by two main categories: 1. Single duct; 2. Dual or double duct. The single duct systems can provide either cooling or heating using the same duct, but not both heating and cooling simultaneously. Dual duct and multi zone systems can provide both heating and cooling simultaneously. These systems can be further classified as: • Single duct, constant volume, single zone system; • Single duct, constant volume, multiple zone system with terminal reheat; • Variable air volume system.

Thanks Prof. Dr. M. M. Nasr Mechanical Power and Energy Dept.