Abstract
This paper reports the influence of the presence of a water canal on the cooling load calculation for an air-conditioned recreation centre in Macao, and investigates the condensation issue of lower floor ceiling caused by the relatively low temperature of canal water. Different canal surface water activities (water activity factor) cause different evaporation rates of canal water and result in the changes of cooling load. It is found that the design of the large indoor water canal leads to the increase of design cooling load of the upper floor of the centre, for example 304 kW (when water temperature is 20°C and surface activity factor equals 1, which is the function of evaporation rate), and condensation of the lower floor ceiling under canal occurs after an operation break of the air-conditioning system. To minimise the cooling load increase due to the presence of a water canal, the water activity of the canal should be lowered as much as possible, and several energy saving measures are recommended. Furthermore, to avoid the possible condensation phenomena and issue of water drop from the ceiling under the canal, the air humidity of the space under the water canal should be controlled strictly according to the design conditions.
Practical application: Heat and mass transfer between the large water surface and the air-conditioned space results in the change of space cooling load in the spaces with large indoor water canal. The influences of the presence of the water canal, due to its evaporation and heat loss, on the cooling load estimation of the space should be investigated for accurately evaluating the cooling load and properly sizing the air conditioning systems in such types of buildings with large interior water facilities. As the evaporation rate changes due to the water activity level of the canal, the change of cooling load should be estimated considering the water activity levels.
On the other hand, for the air-conditioned spaces under the canal, there is the arising issue of condensation due to the low temperature of the canal water. Condensation will occur when the external surface temperature of canal wall is lower than the dew point temperature of the nearby air. The process of the possible condensation issues of the lower floor has been analysed and recommendations are proposed according to the simulation results. This paper is useful in the design of air conditioning system for such types of complexes.
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