Chapter 17: HVAC in Special Applications

 

Chapter 17: HVAC in Special Applications

🔹 1. Hospitals & Clean Rooms

Hospitals and clean rooms require strict environmental control due to the presence of infectious agents, sensitive instruments, and immunocompromised patients.

✅ Key Features:

Air Filtration: HEPA filters to remove contaminants.

Laminar Air Flow: Smooth, unidirectional airflow to avoid turbulence.

Pressure Differentiation:

Positive pressure in operating theaters (keeps contaminants out).

Negative pressure in isolation rooms (keeps contaminants in).
Temperature & Humidity Control: For patient comfort and infection control.
Zoning: Different zones like OT, ICU, wards, labs require tailored HVAC strategies.

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🔹 2. Clean Rooms

Clean rooms are used in pharmaceuticals, electronics, and biotechnology where even microscopic particles can cause defects.

✅ Standards:

Classified by ISO standards (ISO Class 1 to 9) based on particle count.

Air Changes/hour (ACH): Often >100 ACH.
Filtered Air Supply: 100% fresh or high-quality recirculated air.
Materials: Ducts and interiors made from cleanable, non-shedding materials.

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🔹 3. Data Centers (Precision Cooling)

Data centers contain servers that generate massive heat and require 24/7 cooling.

✅ Key Features:

Precision Cooling Units (CRAC/CRAH): Computer Room Air Conditioning/Handling Units control temperature & humidity.

Hot Aisle–Cold Aisle Arrangement: Separates hot and cold air streams to enhance efficiency.
Humidity Control: Maintains ~50% RH to prevent static discharge and corrosion.
Redundancy (N+1, 2N): Backup cooling to ensure uptime.
Raised Flooring: For air distribution and cabling.

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🔹 4. Metro/Railway/Industrial HVAC

✅ Metro/Railway Stations:

High occupancy, need for ventilation and smoke extraction.

Platform Screen Doors (PSD): Reduce heat and pollutant entry.
Systems must function during fire/smoke emergencies.

✅ Industrial HVAC:

Custom designed based on processes.

May involve toxic fume extraction, explosion-proof designs, dust collection, etc.

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🛠️ Practical: Study HVAC Zoning in Hospitals

Study how HVAC is zoned into:

Critical Areas: OTs, ICUs (need HEPA, laminar flow, positive pressure).

Semi-critical: Patient rooms, labs.
Non-critical: Admin, cafeteria, corridors (basic ventilation).

• Each zone has different temperature, filtration, and airflow needs.

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📄 Important Questions & Answers

❓What is Laminar Flow?

✅ Answer:
Laminar flow is a type of smooth, unidirectional airflow that moves in parallel layers with minimal turbulence.
It is commonly used in operating theaters and clean rooms to prevent airborne contaminants from circulating and to maintain sterility.

🔬 In hospitals, vertical laminar flow is used over the operating table to push clean air down and keep bacteria away.

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❓What special care is needed in server rooms?

✅ Answer:

Special considerations for server rooms include:

1. Precise Temperature Control: Servers must be kept below 27°C.

2. Humidity Control: Maintain 40–60% RH to prevent static discharge or condensation.

3. Airflow Management: Use cold aisle–hot aisle configuration.

4. Uninterrupted Power Supply (UPS): HVAC must work during power outages.

5. 24/7 Operation: Systems must run continuously with backup cooling systems.

6. Dust-Free Environment: Filtration to avoid overheating and damage.

7. Monitoring Systems: Remote sensors and alarms for temperature, humidity, smoke, and airflow.