An Experimental Study on Thermal Hydraulic Characteristics of a Steam Condensation Flow in a Circular Microtube

At present, a microchannel heat exchanger is requested to achieve high efficiency in small size energy equipments. In order to clarify the heat transfer mechanism in a microchannel heat exchanger, knowledge on the thermal hydraulic characteristics of condensation flow in channels is essential. However, study on the thermal hydraulic characteristics of steam condensation flow in a microchannel is hardly conducted except visualization of flow patterns. Especially, the number of study on the correlation between the flow structure and heat transfer is small. The objective of the present study is to clarify the thermal hydraulic characteristics of condensation flow in a microtube through the observation of condensation behavior. In order to achieve the purpose, overall heat transfer coefficient in annular flow and slug flow is measured. As the results, the observed flow pattern is transformed from annular flow to bubbly flow through injection flow in a single capillary glassy tube as simulated unit microchannel. And the local overall heat transfer coefficient at slug flow is 10 to 25% lower than that at the annular flow under the particular condition in the present study.