HVAC or Heating, Ventilation, and Air Conditioning provide comfort for people & maintains an effective Environment for surroundings. Proper HVAC Allows humans to exist under adverse conditions. The requirement of HVAC Systems is a must for critical areas like Control rooms, Electronic Equipment Rooms, switchgear hall, Battery room, workshop area, etc. in a petrochemical plant.
The Primary Intent of HVAC-Comfort:
- Comfort is the primary intent of HVAC systems.
- Increase in Productivity.
- Building & Equipment Durability.
- Increase Life & Health.
- Inside condition of 21–24 °C & 50–60 % Relative Humidity is most comfortable & purity of air.
Basic Refrigeration Cycle:
Air Conditioning Capacity – The “Ton”:
- One Ton of Refrigeration (TR) is defined as the quantity of heat removed to freeze 1 Ton (1 American short ton is 2000 pounds) of water into ice from and at 0°C in 24 hours.
- 1 Ton of Refrigeration = 12000 Btu/hr or 3024 Kcal/hr
TR = Q x Cp x (Ti – To) / 3024
- Q = mass flow rate of coolant in kg/hr
- Cp = coolant specific heat in KCal /kg deg C
- Ti = inlet, the temperature of the coolant to the evaporator (chiller) in °C
- To = outlet temperature of coolant from the evaporator (chiller) in °C
Major Work in HVAC (Fig. 2):
- The design HVAC system for plant buildings, which requires specific temp., humidity, internal pressure and cleanliness under various conditions.
- Preparation of Heat load Calculations, System Diagram and Duct/Piping Plan.
- Equipment Sizing & Selection.
HVAC Work Flow:
Tools and Products:
- System Capacity Report (Fan, Cooling, Heating, Humidification)
- Year Simulation (Power, Operation, Cost)
- Load Analysis by Each Room
Scope of work:
- Preliminary Design
- Vendor Print Checking
- Field Engineering
Basic HVAC Equipment:
- Fans / Blowers
- Air Handling Units (AHU)
- Condensing units
- Evaporator (cooling coil)
- Control System
- Air Distribution System
Common HVAC System Types:
- Window / Split AC
- Duct-able Splits
- Packaged Units
- Fan Coil Units
- VRV Units
- Direct Expansion System
- Chilled Water System
Air Handling Unit (AHU):
Equipments (Fig. 7):
- Heat Exchangers
- Cooling Towers
- Duct board
- Grilles, Louvers, & Registers
- Shut off
- ASHRAE – The American Society of Heating, Refrigerating and Air-Conditioning Engineers
- SMACNA – Sheet Metal & Air-conditioning National Contractor’s Association
- NBC – National Building Code
- IS – 12332 For Ventilation in Petrochemical Plants & Refineries
- IS – 3103 For Industrial Ventilation
- OISD – 163 Safety of Control room for the Hydrocarbon industry