第27题: [单项选择]当燃气的密度为0.518kg/m3时,一座层高为3m的住宅,每上一层楼面,室内燃气立管中燃气的附加压头就增加多少 A. 18.25Pa B. 20.25Pa C. 21.25Pa D. 22.79Pa 参考答案:D 答案解析:[解析] 《三版教材》:计算室内低压燃气管道阻力损失时,应考虑因高程差引起的附加压头:ΔH=g(ρk-ρm) ΔH=9.8×(1.293-0.518)×3=
第33题: [单项选择]Questions 15 ~ 18 are based on the following conversation.How many years has it been since the last outbreak of foot-and-month disease in South Africa A. Over 40 years. B. Over 20 years. C. Over 30 years. D. Over 50 years. 参考答案:A