Abstract
The exhaust heat from air conditioners is one of the main factors contributing to the heat island effect in urban areas. This study, taking an approach based on environmental load of the urban atmosphere, used numerical analysis to clarify heat discharge characteristics of air conditioning systems. First, typical air conditioning systems used in offices were classified based on construction and utilities data, then data were collected on coefficient of performance (COP) of those systems' heat sources and correlated. Next, an office building was hypothesized and the summertime air conditioning load was derived to estimate the energy consumed and amount of heat discharged by air conditioning systems, and system COP. The results were as follows: 1) The value of system COP was greatly affected by air temperature and sectional load in multi-systems for buildings, but it was relatively stable in the case of systems using heat and chilled water generators. 2) The cooling load of multi-systems for buildings accounted for 75% of sensible heat emitted by air conditioning systems, but in the case of systems using heat and chilled water generators sensible heat emitted was almost entirely caused by energy consumption by air conditioning systems. 3) Most of the heat emissions from cooling towers were in the form of latent heat, with very little sensible heat. However, to evaluate sensible heat, it is extremely important to estimate the temperature of the coolant. 4) The COP of multi-systems used in buildings decreased as the temperature went above 25℃. With an increase in cooling load came a very large increase in the energy consumption for air conditioning. 5) Artificial heat consumed by medium-rise office buildings was more than 66% the quantity of solar radiation; in the case of multi-systems for buildings, almost all was discharged in the form of sensible heat, meaning that its effect on the atmospheric environment cannot be ignored.
