Psychometric study and HVAC design and drafting

Psychometric study is a vast science and an integral part of HVAC design and drafting, MEP (mechanical, electrical and Plumbing). Psychometric means study of air properties. In literal sense of Air conditioning, air is the aspect to deal with. This air can be Supply air (SA), Return air (RA), Fresh air (FA) and Extract air(EA). SA and RA contribute to maintaining the temperature of the room as per the human comfort. FA and EA signify to the ventilation part. The outside air i.e. the ambient air varies from city to city and from variant time zone. The inside temperature or the desired temperature is universally considered to be between 21 deg C to 26 deg C; ideally 23 deg C. This indoor temp is universally accepted temperature range which is considered satisfactory for human comfort. Other factors which influence human comfort in HVAC system include the metabolic rate of the individuals, their physical activity, health conditions, clothing, food and drink etc. Generally speaking it is associated with individual metabolism rate which produces heat.

Psychometric analysis does not only signify to the temperature aspect but also to at Relative humidity ie RH and that means % of moisture content in air. For HVAC design and drafting, basically there are five major aspects:

• Dry Bulb Temp
• Wet Bulb Temp
• Dew Point Temp
• Relative Humidity
• Humidity Ratio

The preparation of psychometric table in HVAC design and drafting leads to the Heat Load Calculation which makes sure how much heat in unit of BTU/Hr needs to be dissipated and against that how much cooling in terms of TR needs to be entertained in the desired location. 

A Psychrometric Chart is very important tool for HVAC engineers which helps them to carry out heat load or cooling load calculations. This also helps HVAC design and drafting engineers find solutions to various air condition related problems. The psychrometric chart in overall shape looks like a shoe.

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