What is the Working Principle Of Air Cooled Chillers?
Air-cooled chillers remove heat from processes or spaces using refrigerant cycles and ambient air. Here’s a breakdown of their working principle with key components and values:
Compressor
You start with the compressor, which pressurizes refrigerant gas (e.g., R-134a or R-410A) to 100–300 psi, raising its temperature to 50–70°C. This high-pressure gas flows to the condenser.
Condenser Coil & Fans
In the condenser, ambient air blown by fans (at 1,500–3,000 CFM) cools the refrigerant. The gas condenses to liquid, releasing heat and dropping to 40–50°C. Heat rejection efficiency depends on air temperature (ideally ≤35°C ambient).
Expansion Valve
The liquid refrigerant passes through an expansion valve, reducing pressure to 60–100 psi and temperature to 5–10°C, creating a cold mixture of liquid and vapor.
Evaporator
In the evaporator, the refrigerant absorbs heat from process water (e.g., chilled water at 6–12°C), causing it to evaporate back into gas. This cools the water circulated to HVAC systems or machinery.
Heat Rejection
Unlike water-cooled chillers, air-cooled units rely solely on fans to expel heat, operating at 2.5–3.5 COP (Coefficient of Performance). They require 10–30% more energy than water-cooled systems but simplify installation.
Key Data:
Capacity range: 10–500 tons (1 ton = 12,000 BTU/hr).
Typical refrigerant charge: 5–50 kg, depending on chiller size.
Air-cooled chillers are ideal for small-to-medium applications (e.g., labs, hospitals) where water scarcity or cost limits water-cooled options. You control the cycle via thermostats or PLCs to maintain precise cooling demands.
What is the Process of the Air-Cooled Chillers ?
Air-cooled chillers remove heat using a closed refrigeration cycle. Here’s the step-by-step process:
Heat Absorption
You circulate warm process water (e.g., 12–18°C) through the evaporator. Inside, low-pressure refrigerant (e.g., R-134a, boiling point -26°C) absorbs heat, evaporating into gas and cooling the water to 6–12°C.
Compression
The refrigerant gas is sucked into the compressor, where it’s pressurized to 100–300 psi and heated to 50–70°C. This high-energy gas flows to the condenser.
Heat Rejection
In the condenser, outdoor air (blown by fans at 1,500–3,000 CFM) cools the refrigerant. The gas condenses into liquid, releasing heat and dropping to 40–50°C. Ambient air temperatures above 35°C reduce efficiency.
Expansion
The high-pressure liquid passes through an expansion valve, rapidly reducing pressure to 60–100 psi. This cools the refrigerant to 5–10°C, creating a cold liquid-vapor mix ready to absorb heat again.
Cycle Repetition
The refrigerant returns to the evaporator, repeating the cycle. Chilled water (6–12°C) is pumped to air handlers or machinery for cooling.
Key Details:
COP (Efficiency): 2.5–3.5 (1 kW electricity removes 2.5–3.5 kW heat).
Capacity: Typically 10–500 tons (1 ton = 12,000 BTU/hr).
Energy Use: Consumes 0.8–1.2 kW per ton, depending on load and ambient conditions.
Air-cooled chillers rely on ambient air for heat rejection, making them ideal for water-scarce areas but less efficient than water-cooled systems in high-heat environments. You control the process via thermostats or automated systems to maintain precise temperatures.
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