MechanicalEngineer

  FCU Coil and Duct Humidity (Moisture) & Water Condensation Problem 1. What is Condensation? When a cold surface (like a coil, duct, or diffuser) temperature drops below the room’s dew point temperature, the moisture present in the air turns into water droplets. This is called condensation or sweating. Example: If room dew point = 16°C And duct surface temperature = 14°C Then water droplets will definitely form. 2. How Does Condensation Occur in an FCU Coil? ✓. Normal Condition Chilled water temperature in FCU coil = 7–12°C Warm air passes over the coil Moisture turns into water Water collects in drain tray Water goes out through drain pipe This is normal operation. What is FCU Coil Block Problem? When the Fan Coil Unit (FCU) cooling coil gets blocked due to dust, dirt, sludge, or scale, airflow or water flow becomes disturbed. Two Main Reasons for Blockage: 1. Air Side Blockage Dust accumulates on coil fins Filter becomes dirty Airflow reduces When Does the Problem Occur? 1. ...

  Air Handling Unit (AHU) Working Principle The Air Handling Unit (AHU) is the central device in large buildings that cleans, heats/cools, humidifies/dehumidifies, and distributes air. Let’s explain the typical AHU sections and airflow shown in the diagram. Outdoor fresh air (outside air) enters the system and first passes through filters. These filters capture dust, pollen, and airborne particles. In some models, UV lamps (antibacterial) destroy bacteria and viruses. The air then enters the mixing chamber (mixing box), where it is blended with return/relief air coming back from the building. This mixing is important for energy savings. Next, the air passes through the heat recovery wheel (heat wheel). The heat or cooling energy from the exhaust air is transferred to the incoming fresh air, significantly reducing the load on the chiller or boiler. After that, the air goes through cooling coils (cooling coil) where it is cooled using chilled water. When needed, a steam humidifier ad...

  Air Terminals in HVAC Systems Selecting the proper Air Terminal is essential for achieving good air distribution and occupant comfort in HVAC systems. -Common Types Square Diffuser – Round Diffuser – Slot Diffuser – Perforated Diffuser – Swirl Diffuser – Jet Diffuser – Grilles & Registers – Door Cut / Under Cut – Fresh Air Louver – Disk Valve. -Selection Based on Ceiling Height 1-Square / Round Diffusers: typically used with suspended ceilings up to ~4 m. 2-Swirl Diffusers: suitable for heights up to ~5 m due to better air mixing. 3-Jet Diffusers: used for high ceiling spaces such as halls and large areas. 4-perforated Diffuser: in hospitals and surgery rooms Understanding L and Throw Distance L = distance between two diffusers, or half the distance between a diffuser and a wall. Many engineers assume this is the throw distance, but actually it is the Critical Length (L). The relationship between L and T (Throw) depends on the diffuser type,and sometimes T = L. After determin...