Delta T (ΔT) in HVAC Systems – Complete Explanation In HVAC, Delta T (ΔT) means: Difference between two temperatures Formula: ΔT=T1−T2 Where: ΔT = Temperature difference T₁ = First temperature T₂ = Second temperature Why Delta T is Important in HVAC Delta T tells us: • How much cooling or heating is happening • Whether equipment is working properly • Energy efficiency of system • Water flow and air flow condition • Coil performance • Chiller efficiency In HVAC mainly two Delta T are used: • Water Side Delta T • Air Side Delta T 1. Water Side Delta T (Chilled Water / Hot Water) This is the temperature difference between: • Supply water temperature • Return water temperature Usually used in: • Chillers • FCU • AHU • Heat exchangers Chilled Water Delta T In cooling system: • Chiller sends cold water → called CHWS (Chilled Water Supply) • Water absorbs room heat • Warm water returns → called CHWR (Chilled Water Return) Formula: ΔTwater = Treturn−Tsupply Example 1 – Normal ...
Gul Bahar Shah
Gul Bahar Shah
How Air-Cooled Chillers Work | HVAC Cooling Explained
Air-cooled chillers are one of the most widely used cooling solutions in commercial and industrial HVAC systems. They remove heat from water and reject it directly to the atmosphere using ambient air — eliminating the need for cooling towers.
Working Principle of an Air-Cooled Chiller:
An air-cooled chiller operates based on the vapor compression refrigeration cycle, which includes four main components:
1. Evaporator – Heat Absorption
Warm return chilled water from the building enters the evaporator. Inside the evaporator, refrigerant absorbs heat from the water and evaporates into a low-pressure gas. This process cools the water (typically to 7°C), which is then circulated back to AHUs or FCUs for space cooling.
2. Compressor – Pressure Increase
The low-pressure refrigerant gas enters the compressor, where its pressure and temperature increase significantly. This prepares the refrigerant for heat rejection in the condenser.
3. Air-Cooled Condenser – Heat Rejection
The high-temperature refrigerant flows through the condenser coils. Fans blow ambient air across the condenser, removing heat from the refrigerant. As heat is rejected to the air, the refrigerant condenses into a high-pressure liquid.
4. Expansion Valve – Pressure Drop
The liquid refrigerant passes through the expansion valve, where its pressure and temperature drop suddenly. It then enters the evaporator again, and the cycle repeats.
Key Advantages of Air-Cooled Chillers:
• No cooling tower required
• Lower installation complexity
• Reduced maintenance cost
• Ideal for areas with limited water supply
• Suitable for commercial buildings, factories, and offices
Typical Applications:
Office buildings, shopping malls, hospitals, factories, data centers, and industrial cooling processes.
Air-cooled chillers provide efficient, reliable, and cost-effective cooling, especially where water availability and maintenance simplicity are important considerations.
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Working Principle of an Air-Cooled Chiller:
An air-cooled chiller operates based on the vapor compression refrigeration cycle, which includes four main components:
1. Evaporator – Heat Absorption
Warm return chilled water from the building enters the evaporator. Inside the evaporator, refrigerant absorbs heat from the water and evaporates into a low-pressure gas. This process cools the water (typically to 7°C), which is then circulated back to AHUs or FCUs for space cooling.
2. Compressor – Pressure Increase
The low-pressure refrigerant gas enters the compressor, where its pressure and temperature increase significantly. This prepares the refrigerant for heat rejection in the condenser.
3. Air-Cooled Condenser – Heat Rejection
The high-temperature refrigerant flows through the condenser coils. Fans blow ambient air across the condenser, removing heat from the refrigerant. As heat is rejected to the air, the refrigerant condenses into a high-pressure liquid.
4. Expansion Valve – Pressure Drop
The liquid refrigerant passes through the expansion valve, where its pressure and temperature drop suddenly. It then enters the evaporator again, and the cycle repeats.
Key Advantages of Air-Cooled Chillers:
• No cooling tower required
• Lower installation complexity
• Reduced maintenance cost
• Ideal for areas with limited water supply
• Suitable for commercial buildings, factories, and offices
Typical Applications:
Office buildings, shopping malls, hospitals, factories, data centers, and industrial cooling processes.
Air-cooled chillers provide efficient, reliable, and cost-effective cooling, especially where water availability and maintenance simplicity are important considerations.
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