1.In heating design, the outdoor design temperature means the:
1.在供暖设计中，室外设计温度是指：
2.Unit heaters are categorized based on:
2.单元式加热器（Unit heaters）通常根据以下因素进行分类：
3.Modern homes are typically designed for a winter indoor temperature of:
3.现代住宅通常设计为冬季室内温度保持在：
4.Gas-fired unit heaters must meet local regulations regarding gas type, volume, and allowable line pressure ______.
4.燃气单元式加热器必须符合当地关于燃气类型、用气量以及允许的管路压力______的法规要求。
5.The “design temperature difference” represents the variance between:
5.“设计温差”是指以下两者之间的差异：
6.Appliances are divided into Category I and II. Category I units operate with non-positive vent pressure and flue gas temperatures at least ______°F above the dew point.
6.燃气器具通常分为第一类（Category I）和第二类（Category II）。第一类器具运行时，其排气管内压力为非正压（负压），且烟气温度至少比露点高出______°F。
7.The first step when designing a heating system is to:
7.设计供暖系统的首要步骤是：
8.Heat exchangers, introduced around 1930, are widely used for transferring heat between fluids like water and steam. Common uses include:
8.换热器（Heat exchangers）于1930年左右问世，现已广泛用于水、蒸汽等流体之间的热量交换。其常见应用包括：
9.Over time, depending on fluids and usage, heat exchanger performance may ______.
9.随着时间的推移，视所处理的流体类型及使用工况而定，换热器的性能可能会______。
10.The most efficient duct system design keeps each run:
10.最高效的风管系统设计应确保每一段风管：
