Sensible heat

Heat island which is the most documented phenomenon of climatic change is related to the increase of urban temperatures compared to the suburban. Among the various urban heat island mitigation techniques, green and cool roofs are the most promising since they simultaneously contribute to buildings’ energy efficiency. The aim of the present paper is to study the mitigation potential of green and cool roofs by performing a comparative analysis under diverse boundary conditions defining their climatic, optical, thermal and hydrological conditions.

Convective heat transfer coefficient on the air side of direct expansion evaporator under low airpressure is studied by theory and experiment respectively. Results show the convective heat transfercoefficient will diminish along with the density of air under low-pressure. The lower absolute humidity ofair under lower pressure will reduce the difference of water vapor pressure between the air supply andair return. And the quantity of latent heat transfer between the evaporator and the air will decreaseaccordingly.