period one
Types of Water Chillers
notes
Absorption Chiller Types
single-effectdouble-effect
direct-fired
Figure 20
There are three basic types of absorption chillers. They are typically available in capacities ranging from 100 to 1,600 tons [350 to 5,600 kW].
Indirect-fired, single-effect absorption chillers operate on low-pressure steam (approximately 15 psig [205 kPa]) or medium-temperature liquids (approximately 270°F [132°C]), and have a coefficient of performance (COP) of
0.6to 0.8. In many applications, waste heat from process loads, cogeneration plants, or excess boiler capacity provides the steam to drive a single-effect chiller. In these applications, absorption chillers become conservation devices and are typically base-loaded. This means that they run as the lead chiller to make use of the “free” energy that might otherwise be wasted.
Indirect-fired, double-effect absorption chillers require medium-pressure steam (approximately 115 psig [894 kPa]) or high-temperature liquids (approximately 370°F [188°C]) to operate and, therefore, typically require dedicated boilers. Typical COPs for these chillers are 0.9 to 1.2.
The direct-fired absorption chiller includes an integral burner, rather than relying on an external heat source. Common fuels used to fire the burner are natural gas, fuel oil, or liquid petroleum. Additionally, combination burners are available that can switch from one fuel to another. Typical COPs for direct-fired, double-effect chillers are 0.9 to 1.1 (based on the higher heating value of the fuel). Higher energy efficiency and elimination of the boiler are largely responsible for the increasing interest in direct-fired absorption chillers. These types of absorption chillers have the added capability to produce hot water for heating. Thus, these “chiller–heaters” can be configured to produce both chilled water and hot water simultaneously. In certain applications this flexibility eliminates, or significantly down-sizes, the boilers.
