Pass the Flower while beating drums activity (active participation, lots of rewards)
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This edition features a \"Pass the Flower while Drumming\" activity: Rules of the activity: Those on the lower floors are to answer the questions posted by those on the upper floors (for example, floor 2 answers the question in post from floor 1, floor 3 answers the question in post from floor 2). Regardless of whether their answers are correct or not, they must then pose new questions to complete a total of 6 questions; they need to answer as many as necessary. Scoring criteria: 5 wealth points are awarded for answering one question and creating one question. Those who answer two questions and create two questions will be rewarded with 10 wealth points. Those who answer three questions and create three questions will be rewarded with 15 wealth points. Note: Questions are limited to HVAC and thermal energy, as well as energy-saving technologies. Reply order: Step 1: Answer the question. The responder answers the post above them; for example, the 2nd floor replies to the post on the 1st floor, the 3rd floor replies to the post on the 2nd floor, and the 10th floor replies to the question on the 9th floor. When answering, indicate the question number, the answer, and any additional remarks, for example: Answering the second question on floor 9, the answer is B. Step two: Raise a new question. A few questions have been answered, so several new ones should be raised. Example: My new question: 1. If compressors A and B consume the same amount of energy when operating under standard wage conditions and air-conditioning conditions respectively, what are their cooling capacities under each of those conditions? A. A is greater than B ； B. B is greater than A ； equal ； D is related to the refrigerant. Step 3: Combine the unanswered questions from above with the new questions that have been raised. Example: Unanswered questions plus my new questions (questions that the responders should answer): 1. If compressors A and B consume the same amount of energy when operating under standard conditions and under air-conditioning conditions, what are their cooling capacities in each respective condition? A. A is greater than B ； B. B is greater than A ； equal ； D is related to the refrigerant. 2. After adopting a regenerative cycle, the coefficient of performance () A. definitely increases ； B. Must be reduced ； The change in C is related to the working fluid ； The increase or decrease in D is related to the refrigeration equipment used. 3. According to China’s classification of coal types, into which two categories can it be divided? Step four: Send the answers to the new questions you created to the moderator, so that they can grade them. It is recommended that everyone use the copy-and-edit method when replying! ! ! ! ! ! ! ! ! ! ! 1. A thermodynamic system with no heat exchange is called: A. Isolated system B. Closed system C. Adiabatic system D. Open system 2. The basic modes of heat transfer are: A. Conduction, convection, and radiation B. Conduction, convective heat transfer, and radiation C. Conduction, convection, and radiative heat transfer D. Conduction, convective heat transfer, and radiative heat transfer 3. A closed thermodynamic system undergoes a reversible process; it does 20 KJ of work on its surroundings, and 5 KJ of heat is added to the system from the outside. The entropy change of the system is: A. Zero B. Positive C. Negative D. Unable to determine This post was last edited by skybiue123 on 2009-4-2 at 16:40]
I’m not sure if CAA is right or not; they don’t set the questions. Take the next one.
Answering the second question, the answer is A. My question is: What are the two types of fluid flow patterns? The 2 unanswered questions will be answered by the next responder. The 2 unanswered questions plus my question: 1. A thermodynamic system with no heat exchange is called: A. Isolated system B. Closed system C. Adiabatic system D. Open system 2. A closed thermodynamic system undergoes a reversible process; it does 20 KJ of work on its surroundings, and 5 KJ of heat is added to the system. The entropy change of the system is: A. Zero B. Positive C. Negative D. Cannot be determined 3. What are the two types of fluid flow patterns? This post was last edited by njwsm8266 on 2009-4-1 16:59.]
1. The flow patterns of fluids are divided into laminar flow, turbulent flow, and transitional flow. The question asked is what are the two expressions of the second law of thermodynamics? A: Clausius statement and Kelvin-Planck statement B: Carnot statement and Clausius statement C: Carnot statement and Kelvin-Planck statement. 2. The answer to the first question on floor 3 is C. My next question is: What is the thermodynamic temperature scale defined by the International System of Units? A: Celsius scale B: Kelvin scale C: Fahrenheit scale Last edited by wode*aohei on 2009-4-1 16:46]
I’ll also get involved to boost the activity level. Answer: 1. A thermal system with no heat exchange is called an adiabatic system. Answer: 2. The second law of thermodynamics is a principle derived from numerous observations; it can be expressed in two ways: ① Heat always flows from hotter objects to colder objects, and it’s impossible for heat to flow in the opposite direction without causing some other change； ②Work can be completely converted into heat, but no heat engine can convert all the heat it receives into work in a complete and continuous manner (that is, a second kind of perpetual motion machine cannot be created) ； Question: 1. When calculating the heating load, the additional heat loss of the building envelope should be determined as a percentage of the basic heat loss, and the correction factor for south-facing surfaces is ( ). A 0~10% B +15% C -5% D -15%~-30% 2. Radiators in stairwells should be placed as far as possible in ( ). A: Top layer B: Bottom layer C: Any layer D: Middle layer. 3. Central heating systems do not include the following type of heating: ( ) A: Radiator B: Hot air C: Hot water radiation D: Ventilation. We hope everyone will participate actively – the rewards are very generous!
Since this event is being held for the first time, there are still some aspects that have not been thoroughly considered. The following questions can be answered by those who reply: 1. For a closed thermodynamic system that undergoes a reversible process, the system does 20 KJ of work on its surroundings, and 5 KJ of heat is added to the system from the outside. What is the entropy change of the system? A. Zero B. Positive C. Negative D. Cannot be determined 2. What is the thermodynamic temperature scale defined by the International System of Units? A: Celsius scale B: Kelvin scale C: Fahrenheit scale. 3. When calculating the heating load, the additional heat loss of the building envelope should be determined as a percentage of the basic heat loss, and the correction factor for south-facing surfaces is ( ). A 0~10% B +15% C -5% D -15%~-30% 4. Radiators in stairwells should be placed as far as possible in ( ). A: Top layer B: Bottom layer C: Any layer D: Middle layer. 5. The centralized heating system does not include the following type of heating: ( ) A Radiator B Hot air C Hot water radiation D Ventilation. Refer to the format on floor 3 for the correct format. Last edited by skybiue123 on 2009-4-1 17:46.]
Answering the second question on floor 6: the answer is C. My question is: What type of energy does natural gas belong to? ( ) A. Primary energy B. Secondary energy C. Renewable energy. The 4 unanswered questions will be answered by the next person who responds. The 4 unanswered questions plus my own question: 1. For a closed thermodynamic system that undergoes a reversible process, the system does 20 KJ of work on its surroundings, and 5 KJ of heat is added to the system from the outside. What is the entropy change of the system? A. Zero B. Positive C. Negative D. Unable to determine. 2. When calculating the heating load, the additional heat loss due to the building envelope should be determined as a percentage of the basic heat loss; what is the correction factor for south-facing surfaces? A 0~10% B +15% C -5% D -15%~-30% 3. Radiators in stairwells should be placed as far as possible in ( ). A: Top layer B: Bottom layer C: Any layer D: Middle layer. 4. The centralized heating system does not include the following type of heating: ( ) A. Radiator B. Hot air C. Hot water radiation D. Ventilation. 5. What type of energy source is natural gas? ( ) A Primary energy source B Secondary energy source C Renewable energy Source. Last edited by njwsm8266 on 2009-4-1 19:08]
My question is: According to China’s classification of coal types, into which two categories can it be divided? The 4 unanswered questions will be answered by the next responder. The 4 unanswered questions plus my own question: 1. For a closed thermodynamic system that undergoes a reversible process, the system does 20 KJ of work on its surroundings, and 5 KJ of heat is added to the system from the outside. What is the entropy change of the system? A. Zero B. Positive C. Negative D. Unable to determine. 2. When calculating the heating load, the additional heat loss due to the building envelope should be determined as a percentage of the basic heat loss; what is the correction factor for south-facing surfaces? A 0~10% B +15% C -5% D -15%~-30% 3. Radiators in stairwells should be placed as far as possible in ( ). A: Top layer B: Bottom layer C: Any layer D: Middle layer. 4. The centralized heating system does not include the following type of heating: ( ) A Radiator B Hot air C Hot water radiation D Ventilation 5. According to China’s classification of coal types, into which two categories can it be divided? This post was last edited by *e79 on 2009-4-1 21:48]
Answers to questions 2, 3, and 4 of floor 8: 2. When calculating the heating load, the additional heat loss of the building envelope should be determined as a percentage of the basic heat loss, with the southern orientation correction factor being (A). A 0~10% B +15% C -5% D -15%~-30% 3. Radiators in stairwells should be placed as much as possible in (B). A: Top layer B: Bottom layer C: Any layer D: Middle layer. 4. The centralized heating system does not include the following type of heating: (D) A. Radiator B. Hot air C. Hot water radiation D. Ventilation Unanswered: 1. A closed thermodynamic system undergoes a reversible process; the system does 20 KJ of work on its surroundings, and 5 KJ of heat is added to the system from the outside. The entropy change of the system is: A. Zero B. Positive C. Negative D. Cannot be determined. 2. For ( ) pipes, welding connections are suitable when the pipe diameter is greater than 32 mm, while threaded connections should be used when the diameter is 32 mm or less. A. Galvanized welding B. Ungalvanized welding C. Non-welding D. Ungalvanized 3.2. In China, the critical outdoor temperature for heating is set at 5°C as a standard. Mark “√” for correct and “×” for incorrect. 4. Depending on the way in which return air is utilized, central air conditioning systems can be classified into direct-type, mixed-type, and closed-type systems. Compared to DC systems, they have ( ). A. Lowest operating costs B. Best sanitary conditions C. Relatively low operating costs D. Better sanitary conditions E. Significantly reduced equipment investment. 5. According to China’s classification of coal types, into which two categories can it be divided?
Answer to Floor 9: 2. For pipe (B), when the diameter is greater than 32 mm, welding connections are recommended; when the diameter is 32 mm or less, threaded connections should be used. A. Galvanized welding B. Ungalvanized welding C. Non-welding D. Ungalvanized 3.2. In China, the critical outdoor temperature for heating is set at 5°C as a standard. Mark “√” for correct and “×” for incorrect. Unanswered: 1. A closed thermodynamic system undergoes a reversible process; the system does 20 KJ of work on its surroundings, and 5 KJ of heat is added to the system from the outside. The entropy change of the system is: A. Zero B. Positive C. Negative D. Cannot be determined. 4. Depending on how recycled air is utilized, central air conditioning systems can be classified as direct-flow, mixed-flow, and closed-system types. Compared to DC systems, they have ( ). A. Lowest operating costs B. Best sanitary conditions C. Relatively low operating costs D. Better sanitary conditions E. Significantly reduced equipment investment. 5. According to China’s classification of coal types, into which two categories can it be divided? New question 1: If compressors A and B consume the same amount of energy when operating under standard conditions and air-conditioning conditions respectively, what are their cooling capacities under each of those conditions? A. A is greater than B ； B. B is greater than A ； equal ； D is related to the refrigerant. 2. If the condensation temperature in a reverse Carnot cycle increases by 5 degrees or the evaporation temperature decreases by 5 degrees, what is the ratio of their cooling coefficients? A. The former is larger ； B. Equal ； C is larger ； The increase or decrease in D is related to the properties of the refrigerant. 3. After adopting a regenerative cycle, the coefficient of performance () A. definitely increases ； B. Must be reduced ； The change in C is related to the working fluid ； The increase or decrease in D is related to the refrigeration equipment used. Last edited by wu*nglong1 on 2009-4-2 at 15:21.]
2. When calculating the heating load, the additional heat loss of the building envelope shall be determined as a percentage of the basic heat loss, with the south-facing correction factor being (D). A 0~10% B +15% C -5% D -15%~-30% 3. Radiators in stairwells should be placed as much as possible in (B). A: Top layer B: Bottom layer C: Any layer D: Middle layer. 4. The centralized heating system does not include the following type of heating: (D) A Radiator B Hot air C Hot water radiation D Ventilation 5.2. In China, the external critical temperature for heating is set at 5°C as a standard. Mark “√” for correct and “×” for incorrect. Answer: For general civil buildings and industrial buildings, 5°C is advisable. “Code for Design of Heating, Ventilation and Air Conditioning” 6. What is the thermodynamic temperature scale specified by the International System of Units? (B) A: Celsius scale B: Kelvin scale C: Fahrenheit scale
Wu*nglong1 answered the second question on floor 9; the answer is B. For the third question: 2. For pipe (B), when the diameter is greater than 32 mm, welding connections are preferred, while for diameters equal to or less than 32 mm, threaded connections should be used. A. Galvanized welding B. Ungalvanized welding C. Non-welding D. Ungalvanized 3.2. In China, the critical outdoor temperature for heating is set at 5°C as a standard. Mark “√” for correct and “×” for incorrect. Answer: For general civil buildings and industrial buildings, 5°C is advisable. New questions from the “Code for Design of Heating, Ventilation and Air Conditioning”: 1. If compressors A and B consume the same amount of energy when operating under standard conditions and air-conditioning conditions respectively, what are their cooling capacities under each of these conditions? A. A is greater than B ； B. B is greater than A ； equal ； D is related to the refrigerant. 2. If the condensation temperature in a reverse Carnot cycle increases by 5 degrees or the evaporation temperature decreases by 5 degrees, what is the ratio of their cooling coefficients? A. The former is larger ； B. Equal ； C is larger ； The increase or decrease in D is related to the properties of the refrigerant. 3. After adopting a regenerative cycle, the coefficient of performance () A. definitely increases ； B. Must be reduced ； The change in C is related to the working fluid ； The changes in D are related to the refrigeration equipment used. The 3 unanswered questions, along with my new question (questions that subsequent responders should answer): 1. If compressors A and B consume the same amount of energy when operating under standard conditions and under air-conditioning conditions, what is their cooling capacity in each respective condition? A. A is greater than B ； B. B is greater than A ； equal ； D is related to the refrigerant. 2. If the condensation temperature in a reverse Carnot cycle increases by 5 degrees or the evaporation temperature decreases by 5 degrees, what is the ratio of their cooling coefficients? A. The former is larger ； B. Equal ； C is larger ； The increase or decrease in D is related to the properties of the refrigerant. 3. After adopting a regenerative cycle, the coefficient of performance () A. definitely increases ； B. Must be reduced ； The change in C is related to the working fluid ； The change in D is related to the refrigeration equipment used. 4. A closed thermodynamic system undergoes a reversible process; it does 20 KJ of work on its surroundings, and 5 KJ of heat is added to the system from the outside. The entropy change of the system is: A. Zero B. Positive C. Negative D. Unable to determine. 5. Depending on how recycled air is utilized, central air conditioning systems can be classified as direct-type, mixed-type, and closed-type. Compared to DC systems, they have ( ). A. Lowest operating costs B. Best sanitary conditions C. Relatively low operating costs D. Better sanitary conditions E. Significantly reduced equipment investment. 6. According to China’s classification of coal types, into which two categories can it be divided? This post was last edited by njwsm8266 on 2009-4-2 16:04.]
Reply to Floor 10: 6. According to China’s classification of coal types, into which two categories can it be divided? Oita: There is bituminous coal and anthracite. It seems there are 14 categories now, right? 1. Anthracite: high fixed carbon content, high ignition point (approximately 360–420°C), high true relative density (1.35–1.90), low volatile matter content, and low hydrogen content. Apart from power generation, bituminous coal is mainly used as a gasification feedstock (fixed-bed gasifier) for the production of ammonia, domestic fuel, and briquettes. Some low-ash, low-sulfur, high-HGI anthracites are also used as raw materials for blast furnace injection. 2. Low-grade coal: It is the coal with the highest rank among bituminous coals. Its characteristics include a higher ignition point (350–360°C), high calorific value, and weak caking property or no caking at all. Low-grade coal is mainly used for power generation and as fuel in power plant boilers. When using low-volatile coal, mixing it with other coals with higher volatility is also a good approach. 3. Lean coal: It has a low volatility content and poor caking properties, and can be used alone for coke production. When mixed with other coal types suitable for coking, the inclusion of lean coal will increase the size of the coke products. Lean coal can also be used for power generation, power plant boilers, and as a domestic fuel. Typical lean coal is produced by the Xishan Coal and Electricity Company in Shanxi Province. 4. Thin coal: Moderate volatility and cohesion, mainly used for coking. Some gum-like substances may be produced during the coking process, with the thickness of the gum layer ranging from 6 to 10 mm. Coke produced by coking lean coal alone has high mechanical strength but relatively poor wear resistance. Apart from that portion of lean coal with high ash and sulfur content, lean coal is often mixed with other types of coal for coking. 5. Coking coal: It has strong coking properties and moderate volatile matter content (about 16%–28%). Coking coal is the main type of coal used for coking in China. Coke produced from coking coal possesses very excellent properties; coking coal is mainly produced in Shanxi Province and Hebei Province. 6. Fat coal: It has moderate to high volatility (about 25%–35%) and strong cohesiveness; it is mainly used for coking (some fat coals with high ash and sulfur content are used for power generation). Compared to coals of other grades, fat coal generally has a higher sulfur content. 7. 1/3 coking coal: It lies between coking coal, gas coal, and fat coal; it has a high volatility (similar to gas coal), strong cohesiveness (similar to fat coal), and excellent coking properties (similar to coking coal), which is why it is called 1/3 coking coal. 1/3 coking coal is mainly used for coking and power generation due to its high production volume. 8. Gas-fertilizer coal: It has a high volatility (similar to gas coal) and strong caking property (similar to fertilizer coal). It is suitable for producing city gas through coking processes, as well as for mixing with other types of coal in coking operations in order to increase the yield of by-products such as gas and tar. The microscopic composition of gas-fertilized coal differs significantly from that of other coal types, with a relatively high content of the chitinous fraction. 9. Bituminous coal: high volatiles and moderate caking property, mainly used for coking and power generation. Typical gas coal is produced in Liaoning Province. 10. Medium-cohesion coal of 1/2 grade: Coal belonging to the over-coal category; in China, it has only a very small reserve and production volume. Its characteristics are similar to those of some bituminous coals and weakly caking coals. 11. Weakly caking coal: Coal with a low or moderate degree of coalification, which has very poor caking properties and cannot be used alone for coke production. Due to its special formation mechanism, weak coking coal has a high content of inert components. Typical weakly caking coal is found in Datong City, Shanxi Province. 12. Non-stick coal: It was oxidized during the early stages of coalification, which is why it has a low calorific value. It is mainly used for power generation, gasification, and domestic fuel, etc. Non-stick coal is mainly produced in the northwestern region of China. 13. Long-flame coal: Its degree of coalification is the lowest among all bituminous coals. It is called long-flame coal because of its long flame when burning. It is mainly used for power generation, as fuel for power plant boilers, etc. Liaoning Province has the largest reserves of long-flame coal in the country. 14. Lignite: The lowest grade of all coals, characterized by high moisture content, a high oxygen content (about 15%–30%), and the presence of some humic acids. It is mainly used for power generation and gasification. My question: No. The 3 unanswered questions plus my new question (questions that the following responders should answer): 1. If compressors A and B consume the same amount of energy when operating under standard conditions and under air-conditioning conditions, what are their cooling capacities in each respective condition? A. A is greater than B ； B. B is greater than A ； equal ； D is related to the refrigerant. 2. If the condensation temperature in a reverse Carnot cycle increases by 5 degrees or the evaporation temperature decreases by 5 degrees, what is the ratio of their cooling coefficients? A. The former is larger ； B. Equal ； C is larger ； The increase or decrease in D is related to the properties of the refrigerant. 3. After adopting a regenerative cycle, the coefficient of performance () A. definitely increases ； B. Must be reduced ； The change in C is related to the working fluid ； The change in D is related to the refrigeration equipment used. 4. A closed thermodynamic system undergoes a reversible process; it does 20 KJ of work on its surroundings, and 5 KJ of heat is added to the system from the outside. The entropy change of the system is: A. Zero B. Positive C. Negative D. Unable to determine. 5. Depending on how recycled air is utilized, central air conditioning systems can be classified as direct-type, mixed-type, and closed-type. Compared to DC systems, they have ( ). A. Lowest operating costs B. Best hygiene conditions C. Lower operating costs D. Better hygiene conditions E. Significant reduction in equipment investment
3. After adopting a regenerative cycle, the coefficient of performance (a) A. will definitely increase； B. Must be reduced ； The change in C is related to the working fluid ； The increase or decrease in D is related to the refrigeration equipment used. 5. Depending on how recycled air is utilized, central air conditioning systems can be classified into direct-type, mixed-type, and closed-type systems. Compared to DC systems, they have (c, e). A. Lowest operating cost B. Best hygiene conditions C. Lower operating cost D. Better hygiene conditions E. Significantly reduced equipment investment. The 3 unanswered questions along with my new question (questions that subsequent responders should answer): 1. If compressors A and B consume the same amount of energy when operating under standard conditions and air-conditioning conditions, what are their cooling capacities under each respective condition? A. A is greater than B ； B. B is greater than A ； equal ； D is related to the refrigerant. 2. If the condensation temperature in a reverse Carnot cycle increases by 5 degrees or the evaporation temperature decreases by 5 degrees, what is the ratio of their cooling coefficients? A. The former is larger ； B. Equal ； C is larger ； The change in D is related to the properties of the refrigerant. 3. A closed thermodynamic system undergoes a reversible process; the system does 20 KJ of work on its surroundings, and 5 KJ of heat is added to the system from the outside. The entropy change of the system is: A. Zero B. Positive C. Negative D. Cannot be determined. 4. The advantage of steam heating over hot water heating is (). A. High thermal inertia B. Lower initial investment C. Relatively lower operating and maintenance costs D. No need for vertical zoning. 5. The heating period specified in China’s standards is defined as the total number of days in a year when the average daily temperature is less than or equal to the critical outdoor temperature for heating. For general civil buildings and production facilities, auxiliary buildings use ( ) ℃ ； Mid-to-high-grade civil buildings use （） °C.
1. If compressors A and B consume the same amount of energy when operating under standard wage conditions and air-conditioning conditions respectively, then their cooling capacities under their respective conditions are (B). A. A is greater than B ； B. B is greater than A ； equal ； D is related to the refrigerant. 3. The advantages of steam heating over hot water heating are (B, C). A. High thermal inertia B. Lower initial investment C. Relatively lower operating and maintenance costs D. No need for vertical zoning. The 3 unanswered questions, along with my new question (questions that subsequent responders should answer): 1. If the condensation temperature in a reverse Carnot cycle increases by 5 degrees or the evaporation temperature decreases by 5 degrees, what is the ratio of their cooling coefficients? A. The former is larger ； B. Equal ； C is larger ； The change in D is related to the properties of the refrigerant. 2. A closed thermodynamic system undergoes a reversible process; it does 20 KJ of work on its surroundings, and 5 KJ of heat is added to the system from the outside. The entropy change of the system is: A. Zero B. Positive C. Negative D. Cannot be determined. 3. According to Chinese standards, the heating period is defined as the total number of days in a year during which the average daily temperature is less than or equal to the critical outdoor temperature for heating. For general civil buildings and production facilities, auxiliary buildings use ( ) ℃ ； Mid-to-high-grade civil buildings use （） °C. 4. A centralized hot water heating system for new residential buildings should be equipped with ( ) and a room temperature control device. A. Individual household heat metering B. Unit-level heat metering C. Centralized heat metering D. Community-wide heat metering 5. Multi-split air conditioning systems can be used in the following ( ) situations. A. The indoor air contains a high amount of cooking fumes. B. There is significant vibration inside the room. C. There are devices in the room that generate strong electromagnetic waves or high-frequency waves. D. The air quality, as well as temperature and humidity, do not need to be strictly controlled
4. A centralized hot water heating system for new residential buildings should be equipped with (a) and a room temperature control device. A. Individual household heat metering B. Unit-level heat metering C. Centralized heat metering D. Community-wide heat metering 5. Multi-split air conditioning systems can be used in the situation described in (d). A. The indoor air contains a high amount of cooking fumes. B. There is significant vibration inside the room. C. There are devices in the room that generate strong electromagnetic waves or high-frequency waves. D. The air quality, as well as temperature and humidity, do not need to be strictly controlled. The 3 unanswered questions have been added to my new set of questions (questions that those who reply should answer): 1. If the condensation temperature in a reverse Carnot cycle increases by 5 degrees or the evaporation temperature decreases by 5 degrees, what is the ratio of their cooling coefficients? A. The former is larger ； B. Equal ； C is larger ； The change in D is related to the properties of the refrigerant. 2. A closed thermodynamic system undergoes a reversible process; it does 20 KJ of work on its surroundings, and 5 KJ of heat is added to the system from the outside. The entropy change of the system is: A. Zero B. Positive C. Negative D. Cannot be determined. 3. According to Chinese standards, the heating period is defined as the total number of days in a year during which the average daily temperature is less than or equal to the critical outdoor temperature for heating. For general civil buildings and production facilities, auxiliary buildings use ( ) ℃ ； Mid-to-high-grade civil buildings use （） °C. 4. When the air conditioner is operating in cooling mode, the outdoor ambient temperature should not exceed ( ). A. 14℃ B. 28℃ C. 37℃ D. 43℃ 5. In areas where vehicles pass by, the installation height of gas pipelines should not be less than ( ). A．2.2m B．2.0m C．4.5m D．4.0m Last edited by wbp on 2009-4-5 16:53]