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What is HVAC Heat Load Calculations? Part 1

written by: Haresh Khemani • edited by: Lamar Stonecypher • updated: 11/26/2008

The heat load calculations is very important part of the HVAC designer or HVAC consultant. Let us first try to understand what are heat load calculations? You know that we use the air-conditioners to keep our room or offices cool when the surroundings or atmospheric temperature is high.

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    The heat load calculations is very important part of the HVAC designer or HVAC consultant. Let us first try to understand what are heat load calculations? You know that we use the air-conditioners to keep our room or offices cool when the surroundings or atmospheric temperature is high. Due to high atmospheric temperature lots of heat is generated inside the room. The heat load calculations are the process of calculating the total heat generated inside the room by various sources. There are various sources of heat inside the room and all these are considered during heat load calculations.

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    Various Sources of Heat

    Now what are the various sources of heat considered under heat load calculations? All the sources that directly or indirectly lead to generation of heat inside the room and which causes the increase in temperature of the room are considered under heat load calculations.

    Let us see some important sources of heat inside the room:

    1) Heat from the sun: Heat from the sun enters the room by different ways. It enters inside the room by process of conduction through the walls and roof of the rooms. It enters by convection process due to flow of the hot atmospheric air inside the room. The heat of the sun also enters the room by process of radiation via the open and closed glass windows of the room. The heat generated by the room is the major source of heat inside the room.

    The total heat of the sun entering the room greatly depends on the direction or alignment of the room. The maximum heat of the sun in the morning is from the east direction it is absorbed by the walls and windows in the eastern direction. During noon and late noon maximum heat is absorbed by the walls and the windows in south and west directions respectively. The least amount of sun heat is absorbed by the walls in the north direction.

    The heat of the sun entering via glass windows by the process of radiation leads to heating of the room immediately, while the heat entering the room via walls is stored in the walls for long-time and it is released in the room at night, thus heating the room at that time.