AIR CONDITIONING OF SMALL BUILDINGS PREPARED BY NOOR AZILA BINTI JAMARI LECTURER CIVIL ENGINEERING DEPARTMENT
INTRODUCTION Cooling system vary mostly by the way heat is transferred from the rooms to the refrigeration machine/mechanical room and from there to the heat sink. The choice of the heat transfer methods depends on building type and size. Cooling system are often classified by the fluids that are used to transfer the heat from the habitable spaces to the refrigeration machine/mechanical room.
SYSTEM Choice of system will depend on building purpose and degree of occupancy. There are three categories : i. All -Air system ii. All-water system iii. Combination Air-water System
ALL-AIR SYSTEM Air is blown across the cold evaporator coil and then delivered by ducts to the rooms that require cooling. Air systems can effectively ventilate, filter and dehumidify air. The main disadvantages lies in the bulky ductwork that is required. Schematic diagram of an all-air system. .
ALL-WATER SYSTEM The water is chilled by the evaporator coil and then delivered to fan-coil units in each space. Although the piping in the building takes up very little space, the fan-coil units in each room do required some space. Ventilation, dehumidification and filtering of air are possible but not as effective as with an air system. Schematic diagram of an all-water system. .
COMBINATION AIR-WATER SYSTEM In smaller buildings, the heat given off by a refrigeration machine/mechanical room is usually dumped into the atmosphere by blowing outdoor air over the condenser coil. To make this heat transfer more efficient, water can be sprayed over the condenser coil. Medium sized buildings often use a specialized piece of equipment called an evaporative condenser to dump heat into the atmosphere by evaporating water. A cooling tower also dumps heat into the atmosphere by evaporating water. This cooling tower is pumped to the refrigeration machine/mechanical room. Most cooling towers are placed on roofs. Schematic diagram of an air-water system. .
Common locations for centralized mechanical equipment spaces in large multistorey buildings.
AIR CONDITIONING OF SMALL BUILDINGS There are 3 units air conditioning in small building : i. Window units ii. Packaged units iii. Split units
WINDOW UNITS For air conditioning single spaces like motel rooms, a window units is used. The condenser coil, compressor and one fan are on the exterior side of an internal partition. The compressor is on the outside because it is the noisiest part of the equipment. On the interior side of the partition there is the evaporator coil and a fan to blow air over it. As indoor air passes over the evaporator coil, its temperature is often lowered below its dew point temperature. An adjustable opening in the interior partition allows a controlled amount of fresh air to enter for ventilation purposes. A schematic diagram for a window unit air conditioner that can heat as well as cool
PACKAGED UNITS Packaged units are pre-engineered self-contained units where most of the mechanical equipment is assembled at the factory. They offer low installation, operating and maintenance costs. Rooftop versions are the most common with each unit serving a separate zone. Packaged units are also used on the ground for building with crawl spaces or above suspended ceiling when there is enough space below the roof.
PACKAGED UNITS Packaged units can contain both heating and cooling equipment
SPLIT UNITS Most homes and some other buildings find the split units to be most appropriate. In the split unit, the compressor and condenser coils are outdoors while the air handling unit with the evaporator coil is indoors. The air handling unit also contains the central heating systems.
The illustrate the use of split systems for a small office building. The air handling units (AHU) with their evaporator coils and heating systems are in a mechanical equipment room (MER) The supply ducts are above a suspended ceiling but on the indoor side of the roof insulation. The air is supplied to each room through a top register or a ceiling diffuser. Return air grilles and ducts bring the air back to the air handling units. A schematic diagram of a split unit system .