ABSORPTION CHILLERS ,TYPES OF ABSORPTION CHILLERS ~ HVACR DICTIONARY

Absorption Water Chillers

So far, we've discussed water chillers that use the vapor-compression refrigeration cycle. Absorption water chillers are a proven alternative to vapor compression chillers. The absorption refrigeration cycle uses heat because the primary drive . The heat could also be supplied either within the sort of steam or predicament (indirect-fired), or by burning oil or gas (direct-fired).

There are two fundamental differences between the absorption refrigeration cycle and therefore the vapor-compression refrigeration cycle. The first is that the compressor is replaced by an absorber, pump, and generator. The second is that, additionally to the refrigerant, the absorption refrigeration cycle uses a secondary fluid called the absorbent. The condenser, expansion device, and evaporator sections, however, are similar.

Warm, high-pressure liquid refrigerant (D) passes through the expansion device and enters the evaporator within the sort of a cool, low-pressure mixture of liquid and vapor (A). Heat is transferred from the relatively-warm system water to the refrigerant, causing the liquid refrigerant to boil. Using an analogy of the vapor compression cycle, the absorber acts just like the suction side of the compressor—it draws within the refrigerant vapor (B) to combine with the absorbent.

The pump acts just like the compression process itself—it pushes the mixture of refrigerant and absorbent up to the high-pressure side of the system. The generator acts just like the discharge of the compressor—it delivers the refrigerant vapor (C) to the remainder of the system.

The refrigerant vapor (C) leaving the generator enters the condenser, where heat is transferred to cooling system water at a lower temperature, causing the refrigerant vapor to condense into a liquid. This high-pressure liquid refrigerant (D) then flows to the expansion device, which creates a pressure drop that reduces the pressure of the refrigerant thereto of the evaporator, repeating the cycle.

Absorption water chillers generally have a better first cost than vapor compression chillers. The cost difference is thanks to the extra heat-transfer tubes required within the absorber and generator(s), the answer heat exchangers, and therefore the cost of the absorbent. This initial cost premium is usually justified when electric demand charges or real-time electricity prices are a big portion of the electrical utility bill. Because electric demand charges are often highest at an equivalent time as peak cooling requirements, absorption chillers are often selected as peaking or demand-limiting chillers.

Because the absorption chiller uses only a small amount of electricity, back-up-generator capacity requirements may be significantly lower with absorption chillers than with electrically-driven chillers. This makes absorption chillers attractive in applications requiring emergency cooling, assuming the alternate energy source is out there .

Some facilities, like hospitals or factories, may have excess steam or predicament as a results of normal operations. Other processes, like a turbine , generate waste steam or another waste gas which will be burned. In such applications, this otherwise wasted energy are often wont to fuel an absorption chiller.

Finally, cogeneration systems often use absorption chillers as a neighborhood of their total energy approach to supplying electricity additionally to comfort cooling and heating.

There are three basic types of absorption chillers. They are typically available in capacities starting from 100 to 1,600 tons [350 to five ,600 kW].

Indirect-fired, single-effect absorption chillers operate 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 0.6 to 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 because the lead chiller to form use of the “free” energy which may rather 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 work 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, instead of counting on an external heat source. Common fuels wont to fire the burner are gas , fuel oil, or liquid petroleum. Additionally, combination burners are available which will switch from one fuel to a different . Typical COPs for direct-fired, double-effect chillers are 0.9 to 1.1 (based on the upper heating value of the fuel). Higher energy efficiency and elimination of the boiler are largely liable for the increasing interest in direct-fired absorption chillers. These sorts of absorption chillers have the added capability to supply predicament for heating. Thus, these “chiller–heaters” are often configured to supply both chilled water and predicament simultaneously. In certain applications this flexibility eliminates, or significantly down-sizes, the boilers.

About Admin MC3

This is dummy text. It is not meant to be read. Accordingly, it is difficult to figure out when to end it. But then, this is dummy text. It is not meant to be read. Period.