蒸发器和冷凝器盘管的设计都需要确定制冷剂的传热和压力损失。通过使用数字计算机，设计计算的潜在精度大大提高，这主要是因为可以考虑盘管内传热和温差的变化。显然，对传热和压力drpp局部变化的详细信息的要求显著增加。蒸发器或冷凝器盘管内发生的两相压力变化可被视为由三个主要成分组成:直管内的摩擦和动量成分加上弯管内的总损失。已经进行了大量的研究，许多是实证或半实证的- 提出了计算直管内两相压力损失的理论方法。然而，文献中已知只有一个关于回流弯管引起的两相压力损失的参考文献。由于回流弯管对盘管总压降的贡献接近50%，因此其对盘管内温差的影响可能非常显著。显然，需要一种准确的方法来确定这些弯管中的压降。进行了一项实验研究，以确定回流弯管中制冷剂两相流动的压降。本研究的主要目的是开发设计应用结果的相关性。引用:ASHRAE交易，第81卷，第一部分，新泽西州大西洋城

The design of both evaporator and condenser coils requires a determination of refrigerant heat transfer and pressure loss. Through the use of digital computers, the potential accuracy of design calculations has greatly increased, largely because it is possible to account for variations in both heat transfer and temperature differential within the coils. Obviously, the requirements for detailed information on local variations in heat transfer and pressure drpp have increased significantly.The two-phase pressure change which occurs within an evaporator or condenser coil can be regarded as composed of three principal components: the friction and momentum components within the straight tubes plus the total loss in the bends. A great amount of research has been conducted, and many empirical or semi-theoretical techniques have been proposed for calculating two-phase pressure loss in straight tubes. However, only one other reference on two-phase pressure loss due to return bends is known to be available in the literature.Since the contribution of return bends to the total coil pressure drop can approach 50 percent, their influence on the temperature differential within a coil can be very significant. It is clear that there exists a need for an accurate means of determining the pressure drop in these bends.An experimental study was conducted to determine the pressure drop due to two-phase refrigerant flow in return bends. A principal objective of this study was the development of a correlation of the results for design applications.