第一章 单元测试

1、单选题：
The concentration of N2O in the atmosphere of a farmland is 3.2×10-9(volume fraction), then the mass concentration of N2O at an atmospheric pressure of 1.013 × 105Pa and 25°C is （ ） μg/m3.
选项：
A:15.7
B:21.0
C:5.75
D:90.7
答案: 【5.75】

2、单选题：
13.6 g/cm3=()kg/ m3<span style="font-family: -apple-system, "system-ui", "SF Pro SC", "SF Pro Text", "Helvetica Neue", Helvetica, "PingFang SC", "Segoe UI", Roboto, "Hiragino Sans GB", arial, "Source Han Sans CN", sans-serif;">（ ）</span>
选项：
A:13.6
B:13.6×10-3
C:13.6×106
D:13.6×103
答案: 【13.6×103】

3、单选题：
The power of the heating element of the water heater is 5 kW. Under ideal conditions, to heat 20 L of water from 15 ° C to 85 ° C, the specific pressure heat capacity of water is 4.18 kJ ·kg-1 ·℃-1. The required time is （ ）
选项：
A:0.201 h
B:1170 h
C:0.777 h
D:0.325 h
答案: 【0.325 h】

4、单选题：
The upstream flow of a certain section of river is 36000 m3/d, and the concentration of pollutants in the river is 3.0 mg/L. There is a sub-stream with a flow of 10000 m3/d, in which the pollutant concentration is 30 mg/L. It is assumed that the pollutant is completely mixed, and no volatilization, chemical or biological reaction and other processes occur. Then what is the pollutant concentration in the downstream? （ ）
选项：
A:11.3 h
B:24.1 h
C:15.6 h
D:8.87 h
答案: 【8.87 h】

5、单选题：
There is 1 m3 of sewage containing total nitrogen 20 mg/L in a pool. It is now replaced with surface water. The flow rate of surface water entering the pool is 10 m3/min and the total nitrogen content is 2 mg/L. At the same time, the same amount of water is discharged from the pool. Assuming that the mixing in the pool is good and the biodegradation process can be ignored, how long will it take for the total nitrogen content in the pool to become 5 mg/L? （ ）
选项：
A:0.5 h
B:0.18 min
C:0.18 h
D:0.5 min
答案: 【0.18 min】

第二章 单元测试

1、判断题：
There is only heat convection in the convective heat transfer process. （ ）
选项：
A:对
B:错
答案: 【错】

2、单选题：
Which is not the mechanism for heat transfer: （ ）
选项：
A:Heat conduction
B:Local heat transfer
C:Heat radiation
D:Heat convection
答案: 【Local heat transfer】

3、单选题：
For the following statement about the heat conduction coefficient, which is wrong： （ ）
选项：
A:It decreases with temperature for most kinds of liquids, except water and glycerin.
B:Graphite has low heat conduction coefficient so it is usually used as the material for thermal insulator.
C:It is related to the type, temperature, and pressure of the substance.
D:For the same substance, the heat conduction coefficient in different directions or facets can be different.
答案: 【Graphite has low heat conduction coefficient so it is usually used as the material for thermal insulator.】

4、多选题：
Regarding thermal insulation materials, the correct statements are: （ ）
选项：
A:Porous materials are not suitable as insulation materials.
B:Gases are conducive to thermal insulation.
C:The thermal conductivity limit value for insulation materials specified in GB4272 is 0.12 W/(m·K).
D:The thermal insulation performance of insulation materials will significantly decrease after they become damp.
答案: 【Gases are conducive to thermal insulation.;
The thermal conductivity limit value for insulation materials specified in GB4272 is 0.12 W/(m·K).;
The thermal insulation performance of insulation materials will significantly decrease after they become damp.】

5、单选题：
For the following statement about the total heat transfer coefficient K in a tube heat exchanger, which is wrong （ ）.
选项：
A:It indicates the strength of a heat transfer process, so it is not related to the physical properties of the cold and hot fluids.
B:in order to increase
C:It is actually an average value.
D:we should start by reducing the highest thermal resistance in the heat transfer
E:Its value depends on the heat transfer surface selected.
答案: 【It indicates the strength of a heat transfer process, so it is not related to the physical properties of the cold and hot fluids.】