I have to make ppt on "Applications of HVAC industries." Please help me What should I write in dis matter. I think I found an answer. HVAC (pronounced either "HVAC" or "H-vak" is an acronym that stands for the closely related functions of "Heating, Ventilation and Air Conditioning." – Technology of indoor environmental comfort design of the HVAC system is one of major subdiscipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics and heat transfer. Refrigeration is sometimes added to the field abbreviation as HVAC & R or HVACR, or ventilating is dropped as in HACR (such as the designation of HACR-rated circuit breakers). HVAC is particularly important in the design of medium to large industrial and office buildings such as skyscrapers and in marine environments such as aquariums, where safe and hygienic construction are regulated with temperature and humidity as well as "fresh air" from outdoors.