Overview of HVAC: Heating, Ventilation and Air Conditioning

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:

Vapour Compression Refrigeration Cycle
Fig. 1: Vapour Compression 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:

HVAC System Design
Fig. 2: HVAC System Design

Tools and Products:

E20-II, Elite

  • System Capacity Report (Fan, Cooling, Heating, Humidification)
  • Year Simulation (Power, Operation, Cost)
  • Load Analysis by Each Room
Simulation of HVAC using tools
Fig. 4: Simulation of HVAC using tools

Scope of work:

  • Preliminary Design
  • Vendor Print Checking
  • Engineering
  • Field Engineering

Basic HVAC Equipment:

  • Fans / Blowers
  • Air Handling Units (AHU)
  • Filters
  • Compressor
  • 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

Split System:

An outline diagram of a typical split system
Fig. 5: An outline diagram of a typical split system

Air Handling Unit (AHU):

Diagram showing an AHU
Fig. 6: Diagram showing an AHU

Equipments (Fig. 7):

  • Chillers
  • Heat Exchangers
  • Cooling Towers
  • Humidifiers
Diagram Showing Major equipments
Fig. 7: Diagram Showing Major equipment

Air Distribution:

  • Ductwork
  • Metal
  • Flexible
  • Duct board
  • Grilles, Louvers, & Registers
  • Dampers
  • Shut off
  • Fire
  • Smoke
  • Sealants
  • Supports

HVAC Standards:

  • 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


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Anup Kumar Dey

I am a Mechanical Engineer turned into a Piping Engineer. Currently, I work in a reputed MNC as a Senior Piping Stress Engineer. I am very much passionate about blogging and always tried to do unique things. This website is my first venture into the world of blogging with the aim of connecting with other piping engineers around the world.

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