d . Double Chilled Water Coils plus Heat Pipe System e . Chilled Water Coil Direct Expansion ( DX ) Hybrid System
Electric Reheat System
Picture 5 : Air Handling Unit with Heating Coil
The electric heater coils system , as shown in Picture 6 , is the simplest and lowest cost option , where the outside fresh air at 34 ° C is drawn into the system before going through the filtration system to remove pollutants , then the air is cooled to 10 ° C to 12 ° C dew point through the chilled water cooling coil . The air is then passed through the electric heater coil reheated to 18 ° C and , at the same time , its moisture content is lowered . Picture 6 shows a typical electric heater coil system .
The down side of this system are that it consumes a great deal of energy , while it cannot achieve the desired relative humidity level and it suffers from temperature fluctuations .
Picture 6 : Electric Heater Coils
Hot Water Reheat System
This system is similar to the electric reheat system as shown in Picture 6 except that the heating coil is a hot water coil using copper tubes with aluminium fins as shown in Picture 7 .
This system is commonly used in climatic regions where hot water systems or waste heat source systems are readily available . Hot water , typically generated through either a boiler or an electric heat pump or waste heat from upstream
Picture 7 : Copper Tube / Aluminium Fin Hot Water Coil
29