25 Industrial AC

Updated on 01/04/26 by Mananjay MahatoShare on WhatsApp

1. Vapor Compression Refrigeration System (VCRS)

This is the “heart” of most industrial RAC systems.

    • Four Main Components:

      1. Compressor: Increases pressure and temperature of refrigerant vapor.

      2. Condenser: Rejects heat to the medium (water or air); refrigerant changes from vapor to liquid.

      3. Expansion Valve: Reduces pressure and regulates refrigerant flow.

      4. Evaporator: Absorbs heat from the space; refrigerant changes from liquid to vapor.

    • COP (Coefficient of Performance): The ratio of Heat Removed to Work Input.

      $$COP = \frac{Q_2}{W}$$

    • Standard Cycle: Isentropic compression, Isobaric heat rejection, Isenthalpic expansion, and Isobaric heat absorption.

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2. Industrial Compressors

  • Reciprocating: Used for high-pressure applications; common in small to medium cold storage.

  • Screw Compressor: Widely used in large industrial chillers for continuous operation and high efficiency at part-load.

  • Centrifugal: Used for very large capacities (1000+ TR) in district cooling or massive industrial plants.

  • Scroll: Used for modular chillers and high-efficiency VRF systems.

3. Cooling Towers & Condensers

Industrial systems often use Water-Cooled condensers due to higher efficiency compared to air-cooled.

    • Cooling Tower: Cools the condenser water by evaporation.

    • Approach: Temperature difference between cold water leaving the tower and the ambient Wet Bulb Temperature (WBT).

    • Range: Difference between the hot water entering and cold water leaving the tower.

    • Evaporative Condenser: Combines the condenser and cooling tower into a single unit to save space.

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4. Refrigerants (ASHRAE Standards)

  • Ammonia ($NH_3$ – R717): Most common industrial refrigerant. High latent heat, zero ODP/GWP, but toxic and flammable. Avoid copper piping (use steel).

  • Secondary Refrigerants: Fluids like Brine (Salt solution) or Glycol used to carry heat from the evaporator to the final cooling area.

  • R-134a: Used in large centrifugal chillers.

  • R-404A / R-507: Common in commercial/industrial low-temperature freezing.

5. Specialized Industrial Systems

  • Vapor Absorption Refrigeration System (VARS): Uses heat energy (steam/waste heat) instead of mechanical work. Common pairs: Lithium Bromide-Water (for AC) and Ammonia-Water (for refrigeration).

  • Cascade System: Two separate VCRS cycles linked together to achieve ultra-low temperatures (below -70°C).

  • Central AC Plant: Uses an Air Handling Unit (AHU) to distribute conditioned air via ducts.

6. Maintenance & Safety Tools

  • Evacuation: Removing air and moisture using a vacuum pump (measured in Microns).

  • Leak Detection: * Halide Torch: Flame turns green in presence of Freon.

    • Electronic Leak Detector: Most sensitive.

    • Soap Bubble Test: For high-pressure leaks.

  • Psychrometrics: Industrial AC focuses on Dehumidification and Sensible Cooling.

    • Relative Humidity (RH): Controlled typically between 45%–55% for human comfort but varies for industrial processes (e.g., textiles need high RH).

Important Formulas & Units

  • 1 Ton of Refrigeration (TR): $3.517 \text{ kW}$ or $50.4 \text{ kcal/min}$ or $12,000 \text{ BTU/hr}$.

  • Sensible Heat: $Q = m \times C_p \times \Delta T$.

  • Latent Heat: $Q = m \times L$ (Change of state at constant temperature).

25 Industrial AC