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Calculating cooling load is always an important part in HVAC design since the major
equipment sizing such as chillers, AHUs, cooling tower and FCUs are based on the cooling
load. One of the program we usually use to perform cooling load estimation is E20. The
concept of cooling load will be discussed below.
Basically, the cooling load of a space is consisted of three elements: transmission load,
internal load and ventilation load. Transmission load is the external load which transfers
though the wall, glazing, roof and partition, etc. Solar irradiance, the U value of envelope
as well as the infiltration are always the major components contributing to transmission
load. Omitting the infiltration may be result of underestimation of cooling load. Therefore,
a good architectural passive design such as overhead shading, low e glazing, green roof or
air tight envelope would be helpful to reduce certain amount of cooling load. Internal load
mainly comprises lighting, equipment and people load. Lighting load would be large in
shops where spotlights are often used. In data center, equipment load will be dominating.
Lastly, ventilation load, as its name implies, is the cooling load required to treat the
outdoor air from outdoor condition to indoor condition. Thus, it depends on the occupancy
density and the fresh air required per person.
By understanding the meaning of cooling load, it helps to analyze the E20 cooling load
estimation result.
A basic steam system is shown below:
The major function of deaerator is to remove dissolved gases such as oxygen so as to
