GRE陈虎平阅读36套-08-智课网.pdf

智课网GRE 备考资料 Exercise 8 Heat pumps circulate a fluid refrigerant that cycles 1. According to the passage, the role of the flow alternatively from its liquid phase to its vapor phase in a restriction in a heat pump is to closed loop. The refrigerant, starting as a low- (A) measure accurately the flow rate of the Line temperature, low-pressure vapor, enters a compressor refrigerant mass at that point 5 driven by an electric motor. The refrigerant leaves the (B) compress and heat the refrigerant vapor compressor as a hot, dense vapor and flows through a (C) bring about the evaporation and cooling of heat exchanger called the condenser, which transfers refrigerant heat from the refrigerant to a body of air. Now the (D) exchange heat between the refrigerant and the refrigerant, as a high-pressure, cooled liquid, confronts air at that point 10 a flow restriction which causes the pressure to drop. As (E) reverse the direction of refrigerant flow when the pressure falls, the refrigerant expands and partially needed vaporizes, becoming chilled. It then passes through a second heat exchanger, the evaporator, which transfers heat from the air to the refrigerant, reducing the 15 temperature of this second body of air. (126 words) 40 Traditionally, the study of history has had fixed 2. Which of the following best states the main point of boundaries and focal points—periods, countries, the passage? dramatic events, and great leaders. It also has had clear (A) The approach