Functions of HVAC

Fittings, Fixtures And Services 3(1+2)

Lesson 11 : Heating, ventilation and air conditioning (HVAC)

Functions of HVAC

The three major functions of HVAC are:

Electric Heating- Electric heating is a process where electric energy is converted to heat. Common applications used are Space Heating, Cooking, Water Heating and many more. Heating is significant in maintaining adequate room temperature during winter. Basically there are two types of Heating: Local and Central. The Central heating is mainly used as it is cheaper. Furnace or Boiler, Heat Pump and Radiator make the heating system.

Thermal Comfort- Thermal comfort is that state of mind where satisfaction is expressed with the thermal environment. In terms of body sensations, it is a sensation of hot, warmth, neutral and Cold. From the physiological point of view thermal comfort occurs when there is heat exchange between the body and the environment.

Factors affecting Thermal Comfort:
The factors affecting thermal comfort are:

  1. Air Temperature
  2. Relative Humidity
  3. Air Velocity
  4. Radiation
  5. Metabolic Rate
  6. Clothing Insulation

Active Solar Energy Systems – Active solar energy systems are the most cost effective and are mostly used in cold areas. These systems basically use focusing mirrors and metal plates to capture the sun’s energy. Solar rays are absorbed by these collectors and then transferred on to heat, air and water. The solar collector is a black absorber and it absorbs radiation and converts to heat. This heat is then transferred to liquids, through a heat exchanger to heat water in tank and then can be later used as storage. They can be used in commercial as well as industrial. They are also used as space heating where in glazed collectors is used and they absorb the heat through radiant flooring and then it is circulated through fans, or pumps. In both the liquid and air based system, the rays are collected and absorbed and then the heat is transferred directly to the interior space or to a storage system from where the heat is distributed. Liquid systems are basically used for radiant heating systems, boilers with hot water radiators and even absorption heat pumps and coolers. Both the systems can supplement forced air systems.


Active Solar Energy System

Ventilation – This is basically associated with air movement. Ventilation is necessary to allow the foul air to go out and the fresh air to come in. Therefore it is essential to maintain proper ventilation. Insufficient ventilation causes the growth of bacteria because of high humidity thereby hampering the health of members at home. It also decreases the effectiveness of rafter and roof sheathing insulation because of water evaporation.

Last modified: Monday, 13 February 2012, 10:14 AM