平行流换热器在提高性能和减少制冷剂加注量方面为暖通空调行业提供了很多帮助。阻碍其更广泛应用的一个障碍是其作为室外蒸发器的未知性能。大多数大型住宅暖通空调原始设备制造商（OEM）都在同一家工厂制造热泵和冷凝机组，并且更愿意在这两个系统中使用相同的热交换技术。在许多原始设备制造商能够应用平行流技术之前，它必须适用于热泵和冷凝机组。在将其应用于热泵之前，必须更多地了解其作为室外蒸发器的性能，包括其结霜和除霜特性。另外一个问题是平行流换热器的长期完整性，因为它经历了许多霜冻/除霜循环。目前，文献中没有关于这个主题的已知信息。本研究项目的目标是: 1） 在室外机中测试采用传统板翅式热交换器的热泵；2） 在室外热交换器作为冷凝器运行的情况下，量化上述系统在冷却模式下的性能；3） 在室外热交换器作为蒸发器运行的情况下，量化上述系统在结霜条件下加热模式下的性能；4） 测量盘管清除霜负荷和恢复加热功能所需的时间；5） 重复目标2-4，更换了不同翅片间距管方向的板翅式热交换器。

Parallel flow heat exchangers have much to offer the HVAC industry in improved performance and reduced refrigerant charge. An obstacle to their more widespread application is their unknown performance as an outdoor evaporator. Most large residential HVAC original equipment manufacturers, (OEMs) build both heat pumps and condensing units in the same factories and would prefer to use the same heat exchange technology in both systems. Before many OEMs can apply parallel flow technology, it must be applicable to heat pumps as well as condensing units. Before it can be applied to heat pumps, more must be known of its performance as an outdoor evaporator including its frosting and defrosting characteristics. An additional concern is the long-term integrity of the parallel flow heat exchanger as it undergoes many frost/defrost cycles. Currently, there is no known information in the literature on this topic.The objective of this research project is: 1) To test a heat pump employing a conventional plate-fin heat exchanger in the outdoor unit; 2) To quantify the above system's performance in cooling mode with the outdoor heat exchanger operating as a condenser; 3) To quantify the above system's performance in heating mode under frost accumulation conditions with the outdoor heat exchanger operating as an evaporator; 4) To measure the time required for the coil to clear its frost load and resume its heating function; 5) To repeat objectives 2-4 having replaced the plate-fin heat exchangers of various fin pitch tube orientations.