Abstract

In the present study, the boiling flow of R1234yf refrigerant in a horizontal helically coiled tube is investigated to experimentally measure the heat transfer coefficient and pressure drop. A well-instrumented apparatus consisting of the test evaporator and other necessary equipment is used in this investigation. A preheater and a post-evaporator are used to achieve the required vapor qualities and test conditions. Experimental investigations are carried out for a straight tube of 8.7 mm inner diameter and 1,200 mm length as well as helically coiled tubes with three different coil diameters of 10.95, 13.45, and 15.95 cm. For each experiment, different characteristic parameters such as refrigerant flow rate, outside tube surface temperature at various locations, heat flux, and pressure drop within the test section are measured. The results reveal that under the flow conditions studied in this work, heat transfer coefficient is increased up to 299% for the helically coiled tube compared to the horizontal straight tube. In addition, it is observed that for a constant coil pitch, pressure drop increases up to 227% occurring at the minimum coil diameter of 10.95 cm. Moreover, it is found that among the available models, Gungor and Winterton correlation predicts the experimental data with the least error.

摘要

在本研究中，研究了 R1234yf 制冷剂在水平螺旋盘管中的沸腾流动，以实验测量传热系数和压降。在本次调查中使用了由测试蒸发器和其他必要设备组成的设备齐全的设备。预热器和后蒸发器用于达到所需的蒸汽质量和测试条件。对内径为 8.7 毫米、长度为 1,200 毫米的直管以及具有 10.95、13.45 和 15.95 厘米三种不同盘管直径的螺旋盘管进行了实验研究。对于每个实验，测量不同的特性参数，例如制冷剂流量、不同位置的管外表面温度、热通量和测试段内的压降。结果表明，在本文研究的流动条件下，与水平直管相比，螺旋盘管的传热系数提高了 299%。此外，据观察，对于恒定的线圈节距，压降增加高达 227%，发生在 10.95 厘米的最小线圈直径处。此外，发现在可用模型中，Gungor 和 Winterton 相关性对实验数据的预测误差最小。