Keywords

1 Introduction of the Project Site

Zhengzhou, located in the cold area, has a continental monsoon climate of the north temperate zone [1]. The dominant wind direction in spring and summer is southerly wind with the average wind speed being 3.4 m/s and 2.8 m/s respectively. The dominant wind direction in autumn is northerly wind with the average wind speed being 1.8 m/s, while the average wind speed is 3.5 m/s (see Fig. 1) in winter (westerly wind or west-northwest).

Fig. 1.
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Zhengzhou exhibits distinctive traits, notably featuring its peak monthly total radiation during the months of May to July, with a radiation magnitude approximately reaching 550 MJ/m2. November sees the minimum radiation with the radiation amount being about 180 MJ/m2. The annual total radiation is about 4730 MJ/m2 (see Fig. 2). The area is hot in summer and cold in winter. The annual average temperature is about 14.5 ℃, and the average humidity is about 65%. The highest monthly average temperature is 27 ℃, while the lowest is 1.5 ℃. The highest monthly average humidity is 82.1% while the lowest is 51.1% (see Fig. 3 and Fig. 4). The average annual precipitation is about 610 mm. And the precipitation decreases in spring and increases in summer with July and August accounting for about 50% of the annual precipitation (see Fig. 5).

Fig. 2.
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Monthly total radiation in Zhengzhou

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Fig. 3.
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Monthly total radiation in Zhengzhou

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Fig. 4.
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Monthly total radiation in Zhengzhou

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Fig. 5.
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Monthly total radiation in Zhengzhou

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2 Passive Green Building Strategy

Through the analysis of the climate characteristics of Zhengzhou, the passive green building strategies such as sinking type, covered soil type and regular shape are suitable for the Central Plains area [2, 3], which is also the main feature of museum design.

2.1 Sinking Space

The site is a landfill formed many years ago with a depth of 6.4 m. There is a lot of construction waste and domestic waste with uneven nature, so they can not be used as the basic bearing layer. After concession, the excavation and clearance of waste can be carried out in an orderly manner to avoid disturbing the underground cultural relics. The height of the foundation is the same as the depth of garbage removal, which avoids the waste caused by the excessive amount of backfill earthwork and integrates with the atmosphere of the ruins park as a whole, dispelling the volume of modern buildings and avoiding the sense of outburst and pressure of ground buildings.

2.2 Soil-Covered Architecture

In order to further integrate into the landscape of the park and resolve the building volume, especially the sense of conflict between conventional building roof materials and landscape green space, planting roofing is adopted, which puts forward higher requirements for structural load, landscape maintenance, and roof waterproofing. To ensure the basic requirements of plant growth, the minimum thickness of soil cover should be 700 mm to ensure thermal insulation and save building energy consumption.

2.3 Regular Shape and Thermal Insulation Materials

The museum is a regular and square architecture to avoid excessive body changes and reduce the figure coefficient. The spatial scale meets the needs of site value interpretation and communication.

3 Outdoor Environment Study

3.1 Wind Condition Study

The number of tall buildings in the city is increasing with each passing day, and the completion of these buildings will greatly change the wind environment of the city. On the one hand, the tall and dense buildings reduce the ventilation and self-purification ability of the city, and aggravate the air pollution and heat island effect under the condition of low wind speed; on the other hand, when the wind speed is high, the local strong wind will be produced around the tall buildings, making outdoor activities uncomfortable and unsafe, and even causing pedestrian wind environment problems [4, 5]. The periphery of the park is a new urban area under construction, and the construction of high-rise buildings will gradually increase in the future. The sinking space of the museum will become an important wind environment adjustment node in this area. In this paper, the three-dimensional velocity field and temperature field inside and outside the building are accurately simulated by hydrodynamics (Computational Fluid Dynamics: CFD). The flow and heat transfer simulation software based on the CFD principle is used as a simulation tool to study the evaluation of the outdoor wind environment and the prediction of indoor natural ventilation potential [6, 7]. According to Fig. 1, the wind environment in Zhengzhou is conducive to the optimization of the wind environment control of the outdoor site of the project and does not affect the comfort of outdoor activities and building ventilation (see Fig. 6).

First of all, Phoenics is selected as the simulation tool, and the site-building model is established by Autocad [8, 9]. In the process of establishing the site model, the building model and the selection of the calculation area are reasonably simplified. Second, according to the Special Meteorological data set for Building Thermal Environment Analysis in China, the evaluation scene of wind speed and wind pressure is determined, and according to the meteorological characteristics of the project site, three typical working conditions in summer, winter and transition season are analyzed respectively. Finally, the evaluation of the outdoor wind environment of the site mainly takes the Beaufort wind grade as the standard, and the potential of indoor natural ventilation takes the wind pressure difference of the building facade as the standard. The greater the pressure difference is, the more beneficial it is to indoor ventilation [10], but if the wind pressure difference is too large, it will cause damage and shedding of doors, windows and exterior decoration, and the project location is close to cold areas. Excessive wind pressure difference will also increase cold air infiltration, increase heating energy consumption and indoor discomfort. Therefore, the potential of natural ventilation should be moderate.

Fig. 6.
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Monthly total radiation in Zhengzhou

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Table 1. Season condition simulation in outdoor wind environment.
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A large area of vortex area appeared in the inner courtyard in summer. In most other areas, the wind speed is low, which is about 0.3–1.8 m/s. The maximum wind speed is 2 m/s, and the ventilation condition is good (see Table 1/Fig. 7 and Fig. 8).

Fig. 7.
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Vector diagram of wind speed at the altitude of 1.5 m in summer

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Fig. 8.
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Cloud map of wind speed at an altitude of 1.5 m in summer

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The distribution of the flow field around the area is balanced in winter. The wind speed in most areas is 0.3–2.5 m/s, with the maximum wind speed being about 3.7 m/s, the average wind speed about 1.4 m/s, and the maximum wind speed in the central rest area 1.5 m/s, which will make people feel comfortable. The winter wind speed magnification factor of the project pedestrian area is less than 2. The overall situation is good with only one large part of the wind speed magnification factor appearing at the ascending ramp. The area is very small, and the wind speed amplification factor is not more than 2, which does not affect the outdoor comfort of the pedestrian area (see Fig. 9, Fig. 10 and Fig. 11).

Fig. 9.
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Vector diagram of wind speed at the altitude of 1.5 m in winter

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Fig. 10.
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Cloud map of wind speed at an altitude of 1.5 m in winter

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Fig. 11.
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Cloud map of wind speed magnification factor at the altitude of 1.5 m in winter

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The distribution of the flow field around the transition season is relatively uniform, with the local wind zone and eddy current zone. The wind speed in most areas is 0.3–1.8 m/s with the maximum wind speed being 3.7 m/s, which is conducive to outdoor heat dissipation and pollutant dissipation (see Fig. 12 and Fig. 13).

Fig. 12.
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Vector diagram of wind speed at the altitude of 1.5 m in transition season

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Fig. 13.
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Cloud map of wind speed at an altitude of 1.5 m in transition season

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In summer, the wind pressure on the facing surface of the building is between 2.5–4.5 Pa, and the windward pressure of more than 50% of the facades exceeds 0.5 Pa, which is a prerequisite for the formation of good indoor natural ventilation (see Fig. 14 and Fig. 15).

Fig. 14.
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Pressure distribution on the windward side of buildings in summer

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Fig. 15.
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Distribution map of leeward pressure of buildings in summer

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The maximum pressure difference between the front and leeward sides of the building in winter is about 1.6–4.9 Pa. The building is a single-row building with moderate ventilation capacity and no excessive cold air penetration (see Fig. 16 and Fig. 17).

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Pressure distribution on the windward side of buildings in winter

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Fig. 17.
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Distribution map of leeward pressure of buildings in winter

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During the transition season, the wind side of the building surface is about 0.6–3.1 Pa, and the windward pressure of more than 50% of the facades exceeds 0.5 Pa, which is a prerequisite for the formation of good indoor natural ventilation (see Fig. 18 and Fig. 19).

Fig. 18.
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Pressure distribution on the windward side of buildings in transition season

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Fig. 19.
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Distribution map of leeward pressure of buildings in transition season

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To sum up, the outdoor wind environment of the site is relatively comfortable. In summer and transition season, the indoor and outdoor pressure difference in 50% of the building opening area exceeds 0.5 Pa, so it is suitable to adopt natural ventilation measures.

3.2 Thermal Environment Study

According to software simulation and analysis, the gray-black part of the shaded area of the building is shown in the following picture, and the non-shaded area is shown by the red line (see Fig. 20 and Fig. 21). The outdoor activity area is 14,231 square feet, of which the shaded area is 7,220 square feet, and the shaded area of trees in the non-shaded area is 67.51 L. The coverage rate of the shaded area of outdoor activity area is 51.21% (see Fig. 22 and Fig. 23).

Fig. 20.
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Distribution map of building shadow area

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Fig. 21.
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Planting Map of Yangshao Culture-themed Courtyard

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Fig. 22.
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VIP courtyard planting map

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Office planting map

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Table 2. Season condition simulation in outdoor wind environment.
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The total roof area is 13,339.7 m2, the green space area is 12,254.7 m2, the roof greening rate is 91.87%, and the total roof area with horizontal projection area and solar radiation reflection coefficient is more than 75% (see Table 2).

4 Indoor Environment Study

4.1 Sunlight Analysis

The amount of radiation in summer is relatively large, and the use of shading measures in summer is beneficial to reduce the energy consumption of air conditioning [5]. In order to maintain the integrity of the appearance of the museum, the appearance of the offices uses the same decorative concrete louver as the main curtain wall material of the museum, which is analyzed by the project team to ensure the office requirements.

According to the statistics of the above results, the space area of the first floor and the second floor of the project to participate in daylighting calculation is 1,863 square meters, with 1,159 square meters, or 62.2% of the total, meeting the standard. The statistical results are shown in the table below. Office and conference rooms can avoid direct sunlight, and the lighting is mainly through the diffuse reflection through the external decoration of the concrete grille. In addition, the louver of the office area avoids window direct light, indoor lighting is mainly diffuse light, and the staff background can face the window (see Fig. 24).

Fig. 24.
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Simulation results of annual dynamic natural lighting in main functional space

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4.2 Anti-condensation and Thermal Bridge Analysis

In order to maintain a comfortable indoor environment in summer and winter, air conditioning and heating are needed most of the time. At the same time, the transition season has the temperature and humidity conditions of making good use of natural ventilation. The internal space of this scheme is relatively complete, and there is a skylight in the hall of the exhibition hall, so anti-condensation measures are adopted in the construction of the outer wall and roof to ensure that when the inner surface temperature ‘twn’ of the outer structure is higher than the indoor dew point temperature tl in winter, which will not lead to condensation on the inner surface of the outer structure (see Table 3, 4, 5, 6, 7, 8, 9 and Fig. 25, 26, 27, 28, 29, 30, 31, 32).

Table 3. Calculation table of the inner surface temperature of a roof
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Table 4. Inner surface temperature of exterior wall
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Table 5. Inner surface temperature of exterior window
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Table 6. Inner surface temperature of thermal bridge column
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Table 7. Inner surface temperature of thermal bridge beam
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Table 8. Inner surface temperature of the thermal bridge floor
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Table 9. Inner surface temperature of thermal bridge joint of external floor slab
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Fig. 25.
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Temperature field distribution map of RO1 roof (the most disadvantageous) XTimn = 17.2 ℃

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Fig. 26.
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Distribution diagram of temperature field of W01 exterior wall XTimn = 17.1 ℃

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Fig. 27.
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Temperature distribution on the inner surface of C01 outer window XTimn = 16.4 ℃

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Fig. 28.
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Temperature distribution of the most unfavorable inner surface of the thermal bridge column XTimn = 16.1 ℃

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Fig. 29.
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Temperature distribution of the most unfavorable inner surface of the thermal bridge beam XTimn = 16.6 ℃

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Fig. 30.
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Temperature distribution of the most unfavorable inner surface of the thermal bridge floor XTimn = 18.5 ℃

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Fig. 31.
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Temperature distribution of the most unfavorable inner surface of the thermal bridge joint of the external floor slab XTimn = 16.8 ℃

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Fig. 32.
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Temperature distribution of the most unfavorable surface

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4.3 Change of Inner Surface Temperature

According to Fig. 5, there is abundant precipitation in Zhengzhou, which provides better conditions for planting roofs. The thickness of the roof of the museum is more than 700 mm, and the thermal insulation of the external wall is also thickened, so the main rooms and corridors of the office area adopt natural ventilation. After simulation, it is confirmed that the indoor temperature changes with the outdoor temperature in a reasonable range to reduce the energy consumption of air conditioning. The heat transfer process of the exterior wall and roof of the enclosure structure is usually regarded as a one-dimensional unsteady heat conduction problem without an internal heat source. The numerical analysis method is used to calculate the boundary conditions and calculation parameters according to the provisions and appendices of the Code for Thermal Design of Civil Buildings GB50176-2016 (see Fig. 33 and Fig. 34).

Fig. 33.
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Temperature distribution of the most unfavorable surface

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Fig. 34.
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Indoor and outdoor wall temperature distribution of the wall

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5 Conclusion

This project combines the interpretation and communication of site value, urban negative space regeneration, and passive green building strategy. During the scheme design phase, CFD and other software were used to simulate and evaluate key indicators such as wind environment, light environment, and thermal environment, providing clear and accurate guidance for scheme deepening. This paper provides an example and reference for the passive green ecological building design in the Central Plains.