Characteristics of vertical temperature gradient in offices and its impact on air conditioning energy consumption.

• The vertical temperature gradient were analyzed in offices. • An evaluation index for air-conditioning energy consumption was proposed. • The energy-efficiency advice on air-conditioning for offices is given. Installing curtains on windows prevents direct sunlight from entering the indoor working space. It also alters the direction of solar heat radiation and the spatial distribution characteristics of indoor heat gain. This paper analyzes the relationship between the change of heat gain in the working and non-working spaces of the room under the effect of curtains. Meanwhile, it proposes an index of The Useless Cooling Capacity Ratio (UCCR) of the room to analyze its useless cooling capacity. In the hot summer and cold winter region, this study employs experimental and simulation methods to investigate the influence of solar radiation intensity, curtain thermal characteristics, and other factors on the vertical temperature gradient and heat flux indoor during the summer. The results showed that installing curtains on the windows reduced the vertical temperature gradient of the working space and improved the thermal comfort. The vertical temperature gradients in the working and non-working zones under the experimental conditions were 0.24 °C/m and 0.66 °C/m for the room with curtains and 0.62 °C/m and 0.57 °C/m for the room without curtains, respectively. Curtains can regulate the spatial distribution of heat loads and UCCR in a room and make the room more energy efficient. The UCCR for rooms with and without curtains were 24 % and 18 %, respectively, with curtains adding 120 kJ of useless cooling capacity to the work area. [ABSTRACT FROM AUTHOR]