GRE机经在哪里找？GRE阅读机经真题答案详细解析之：Passage 43-「GRE阅读真题」免费下载

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GRE阅读机经Passage 43

Constant variations in the amount of sunlight available on Earth at any given location make energy storage a necessary design feature of terrestrial solar-energy systems. For systems transforming solar to thermal energy, the thermal energy may be stored in matter as either latent heat or sensible heat. Latent heat is absorbed or released whenever matter changes phase, as when matter changes from liquid to gas, for example, or from gas to liquid. Large heat capacities are associated with certain materials, like salts, but in any substance this storage is available only at the unique fixed temperature at which the particular phase transition occurs in that substance. Moreover, materials that have transitions at the temperatures that terrestrial solar-energy systems are likely to encounter are usually destructively corrosive at those temperatures. The storage of sensible heat, on the other hand, allows flexibility as to temperature, in addition, safe substances like water and most rocks have large sensible heat capacities.

文章解析

第一部分：

Constant variations in the amount of sunlight available on Earth at any given location make energy storage a necessary design feature of terrestrial solar-energy systems. For systems transforming solar to thermal energy, the thermal energy may be stored in matter as either latent heat or sensible heat. 白话版讲解： 地球表面任意一个位置受到的阳光照射量会经常变化，这就要求地面的太阳能（接收）系统必须带能量存储的设计。（某一个地方，白天光照多，夜里没阳光；夏天光照多，冬天光照少。白天和夏天接收到的太阳能用不完，夜里和冬天接收到的太阳能又不够用，所以就需要太阳能接收系统，不光有用来接收太阳能的装置，比如太阳能板，还得带上能力存储的设计）。存储，就是先把接收到的太阳能转化为热能，然后存储热能。存储热能有两种方式，一种是以潜热的方式存储，一种是以显热的方式存储。

第二部分：

Latent heat is absorbed or released whenever matter changes phase, as when matter changes from liquid to gas, for example, or from gas to liquid. Large heat capacities are associated with certain materials, like salts, but in any substance this storage is available only at the unique fixed temperature at which the particular phase transition occurs in that substance. Moreover, materials that have transitions at the temperatures that terrestrial solar-energy systems are likely to encounter are usually destructively corrosive at those temperatures. 白话版讲解： 潜热的存储和释放，都是通过物质改变相性（液体变成气体或气体变成液体等）来实现。液体变成气体会吸收热量，气体变成液体会释放热量。有些物质具有很高的储热能力，但是要释放这种热能，只能在会促使该物质发生相变的唯一的一个固定的温度值时，才能实现。（这有什么问题和麻烦呢，比如这个温度值高于100度，或者低于零下40度，就得在太阳能接收系统再多加上专门用来实现这种不太容易实现的温度的设施）除此之外，潜热这种储热方式，还有一个问题。那就是，如果促使用于储热的物质发生相变的那个温度的值处于太阳能接收系统平常可能处于的温度区间，这些用于储热的物质在这个温度区间通常具有强腐蚀性，会破坏东西。(这是什么意思呢，举个例子，假如这个温度值是20度这种相对来说比较好实现的温度，而太阳能接收系统平常一般处于负15度到38度之间的环境中，比如中国北方某城市某市民家里装的太阳能板。而20度这个值处于这个区间内，那这种相变温度在20度的储热物质，在负15度到38度的温度区间，又有强腐蚀性，放在那里好好的，就会把太阳能接收系统这个装置给腐蚀掉)。

第三部分：

The storage of sensible heat, on the other hand, allows flexibility as to temperature, in addition, safe substances like water and most rocks have large sensible heat capacities. 白话版讲解： 如果是以显热的方式储存热量，获取热量或存储热量时的温度就不必固定为某一个特定的温度，另外，不需要用一些腐蚀性强、危险的物质来当储热介质，可以用水这样安全的物质来当储热介质。大部分岩石都可以通过显热存储方式储存大量热量。

题目解析

1.The primary purpose of the passage is to discuss which of the following? A. reasons for the necessity for developing solar-energy systems. B. different ways of storing solar energy as heat. C. new designs for devices that collect solar energy. D. procedures for transferring thermal energy between materials. E. differences between capacities of solids and liquids to store sensible heat.

白话版讲解：

问全文的主要目的？主要是介绍了吸收太阳能转换为热能，然后有两种储存热能的方式，潜热存储和显热存储。当然，文章对潜热存储的介绍多一点，但是对显热存储也介绍了。所以选B。文章不是在介绍必须发展太阳能系统的原因；不是在介绍用于收集太阳能的设施的新设计，而是在讲存储热；不是在介绍将热能在不同物质中传递的程序；不是在比较固体（比如岩石）和液体（比如水）存储显热的能力的不同。所以选项A、C、D、E错误。 本题答案：B Consider each of the choices separately and select all that apply. 2.According to the passage, solar-energy systems located on Earth must store energy for which of the following reasons? A. At any given location on Earth, the amount of sunlight available frequently changes. B. The operation of such systems depends on devices that require a power source other than solar energy. C. Demand for the energy produced by such systems varies in unpredictable ways.

白话版讲解：

问，根据文章，地球上的太阳能系统（除了能接收热之外，还）必须要能储热，这是为什么？根据文章第一句话，选项A正确。文章没有提到太阳能以外的热来源，所以B选项错误。 C选项是说对太阳能系统产生的热的需求的变化不可预测，就是说有时候一下子很多人想用太阳能洗澡，有时候又没什么人想用太阳能洗澡了。这是文章没有提到的，所以C选项错误。本题答案：A Consider each of the choices separately and select all that apply. 3.The author suggests that which of the following constitutes a potential disadvantage of using latent heat for energy storage? A. The circumstances under which phase transitions occur would limit the versatility of latent heat as a storage method. B. The supply of substances that possess the properties that are needed in a medium for latent heat storage is dwindling. C. The properties that are needed in a medium for latent heat storage are found in substances that have other, undesirable properties.

白话版讲解：

问使用潜热这种方式来存储热能，有什么潜在缺点？ A“”物质相变发生的环境会限制潜热这种储热方法的versatility” versatile的意思是“having many uses or applications”，所以versatility的意思是“多用途性”。选项中The circumstances under which phase transitions occur是指fixed temperature，如果这个fixed temperature太低或太高，比较难实现的话，latent heat这种储热方式就无法apply，就出现了versatility（application）被limit的情况。所以A选项正确。 B“用于潜热存储方法的储热介质的供应量在减少”。比如某种潜热存储方法需要用铜当介质，而铜越来越少了。文章没有提到。所以B选项错误。 C“某种潜热存储方法需要的介质的属性在某些情况下，又包含一些不好的属性” 就是说有的介质挺好，相变的温度值在比较好实现的温度区间内，但是这种介质在这个温度区间又有一些其他不好的属性，比如强腐蚀性。根据文章第二部分最后一句话，C选项正确。本题答案：AC