编辑点评: GRE阅读的方法相信大家已经积累了很多了,本文就为大家提供一些GRE阅读的材料,大家来练一练,把平时学到的东西运用到实际中,也多多积累词汇和句子,提高自己的阅读能力。
每天做一些标准的GRE阅读练习,有助于大家在GRE考试的复习过程中不断地进行练习和总结。希望大家在进行GRE阅读练习时,充分运用平时所积累的知识,这样才能有效果。
The use of heat pumps has been held back largely by skepticism about advertisers claims that heat pumps can provide as many as two units of thermal energy for each unit of electrical energy used, thus apparently contradicting the principle of energy conservation . Heat pumps circulate a fluid refrigerant that cycles alternatively from its liquid phase to its vapor phase in a closed loop . The refrigerant, starting as a low-temperature, low-pressure vapor, enters a compressor driven by an electric motor. The refrigerant leaves the compressor as a hot, dense vapor and flows through a heat exchanger called the condenser, which transfers heat from the refrigerant to a body of air. Now the refrigerant, as a high-pressure, cooled liquid, confronts a flow restriction which causes the pressure to drop. As the pressure falls, the refrigerant expands and partially vaporizes, becoming chilled. It then passes through a second heat exchanger, the evaporator, which transfers heat from the air to the refrigerant, reducing the temperature of this second body of air. Of the two heat exchangers, one is located inside, and the other one outside the house, so each is in contact with a different body of air: room air and outside air, respectively.
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