MechanicalEngineer

  How Does an Air Conditioner "Think" to Heat Your Home? Many clients believe air conditioners "create" heat out of thin air, but as HVAC professionals, we know the truth: Heat isn't created—it’s moved. And the conductor of this entire process is the 4-Way Reversing Valve. 🔄The Heating Cycle: Step-by-Step In the image, we see the system in the Heating Cycle. Here is the refrigerant’s journey: The Compressor (Discharge): High-pressure, high-temperature refrigerant gas exits the compressor (red line). The Reversing Valve: This is where the magic happens. When the solenoid coil is energized, the internal slide moves, diverting that hot gas toward the Indoor Heat Exchanger. Condenser (Indoor): In heat mode, the indoor unit acts as the condenser. The gas releases its heat into the room and condenses into a liquid. Bi-Flow Expansion Valve: The liquid refrigerant passes through the expansion valve, dropping its pressure and temperature significantly. Evaporator (Outdo...

  Humidity vs. Relative Humidity – Why It Matters in HVAC Many people use the term humidity in general, but technically there is an important difference: Humidity (Absolute Humidity) → The actual amount of water vapor present in the air. Relative Humidity (RH) → The percentage of moisture in the air compared to the maximum amount the air can hold at the same temperature. The key point? Relative Humidity changes with temperature — even if the moisture content stays the same. 📌 Why these matters for HVAC engineers: • Condensation occurs at the Dew Point. • Impacts sensible & latent load calculations. • Affects equipment sizing. • Prevents moisture formation on ducts and chilled water pipes. • Improves indoor air quality and occupant comfort. Understanding this difference is not theoretical — it directly impacts design accuracy and system performance. hashtag Activate to view larger image,

  This image explains the step-by-step calculation of a Chilled Water Pump (CHWP) for a typical  HVAC project. First, the required chilled water flow rate is calculated using the cooling load and the design temperature difference (AT). In the example, a 1400 kW cooling load with a 5°C AT gives approximately 67 L/s flow. Second, the Total Dynamic Head (TDH) is determined by summing all system pressure losses including pipe friction, fittings, AHU/FCU coil drops, and chiller evaporator drop. The total pressure loss (165 kPa) is converted to head in meters, and a safety margin is added, resulting in about 19-20 meters head. Third, the pump is selected from the manufacturer's performance curve, so the operating point (67 L/s at 20 m) is close to the Best Efficiency Point (BEP) for optimal performance. Finally, the motor power is calculated using flow, head, and pump efficiency, resulting in approximately 17.5 kW, so the next standard motor size (18.5 kW) is selected. The design a...