Study on the impact of buildings on the outdoor thermal environment based on a coupled simulation of convection, radiation, and conduction

ASHRAE Transactions, July, 2007 by Hong Chen, Ryozo Ooka, Hong Huang, Madoka Nakashima

[FIGURE 6 OMITTED]

[FIGURE 7 OMITTED]

Comparison of Sensible Heat Flux Volumes from Each Building Wall. Table 3 shows the mean surface temperature of each wall and the amount of sensible heat flux from the building walls in Case 1. The total amount of sensible heat flux from the walls of one building is 263.31 kW, and these values are of almost the same order as for artificial heat release (378 kW) from the same building.

Table 3. Mean Surface Temperature of Each Wall and the Amount
of Sensible Heat Flux from the Building Walls

               North  South  East   West    Rooftop

Mean surface   34.53  36.59  34.48   52.38    52.39
temperature,
[degrees]C

Mean surface
temperature,
[degrees]C
(by the
Monte
Carlo method
[Yoshida et
al. 2000b])    35.40  37.70  35.60   53.00       --

Sensible heat   6.59  19.81  13.13  108.44   115.34
flux, kW

                Entire   Artificial
                            Heat

               Building  Release
               Walls

Mean surface
temperature,
[degrees]C

Mean surface
temperature,
[degrees]C
(by the
Monte
Carlo method
[Yoshida et
al. 2000b])

Sensible heat    263.31   378 (Case
flux, kW                         2)

Impact Factor Indices. Table 4 shows the mean impact factor index of each building wall and artificial heat release (i.e., the average value within canyon spaces of 30 m height). The horizontal and vertical distributions of the impact factor index of all building walls and the artificial heat release from the buildings are shown in Figures 8 and 9, respectively. For the impact factor index of the building walls, compared to Case 1, the impact factor index of the west wall and rooftop demonstrate an increase in Case 4. In the three cases where artificial heat release is considered (Cases 2, 3, and 5), the impact factor index for the artificial heat release in Case 3 is the largest. The impact factor index for artificial heat release in Case 2 is -0.032[degrees]C, and this is thought to be due to the cool air in the upper region flowing into the dwelling region because of mixing between the upper and bottom regions that occurs as described above. The impact factor index for the artificial heat release in Case 5 is 0.354[degrees]C in the vicinity of the ground (height 1.5 m), and this is about 40% of the impact factor index in Case 3, where artificial heat is released from the ground. This is thought to be due to the artificial heat released from the rooftop flowing into the canyon space due to the circulatory flow caused by the heterogeneous building block configuration. The impact factor index for all building walls shows a very large value (0.888[degrees]C) in Case 4, indicating that the total influence of all the building walls depends on the configuration of the building block.

Table 4. Mean Impact Factor Index [[degrees]C]

                                 Plan    A-A'    B-B'
                                       Section  Section

                  North         0.012    0.027   0.007
                  South         0.027    0.062   0.019
Middle-Rise       East          0.042    0.050   0.027
Building Block    West          0.088    0.078   0.137
(Case 1)          Rooftop       0.083    0.200   0.081
                  Total walls   0.252    0.417   0.270

                  North         0.035    0.034   0.030
                  South         0.093    0.098   0.083
Heterogeneous     East          0.074    0.049   0.053
Mixed Block       West          0.342    0.278   0.312
(Case 4)          Rooftop       0.344    0.428   0 400
                  Total walls   0.888    0.888   0.878

                  Case 2       -0.032    0.095   0.004
Artificial        Case 3        0.863    2.078   0.476
Heat Release      Case 5        0.354    0.805   0.716