Experimental study on solidification of PCM around vertical finned tube

• Main Author: Leow, Brandon Kok Kian.
• Other Authors: Tan Fock Lai
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Mechanical engineering
• Online Access: http://hdl.handle.net/10356/16120
• Institution: Nanyang Technological University

An experimental investigation on heat transfer enhancement by using a vertical finned brass tube in the cold thermal storage system is presented in this paper. Heat transfer fluid (HC-50) flows through the finned tube which is surrounded by phase change material (water). The solidification of the water is described by a temperature transforming model coupled to the heat transfer from the transfer fluid. The objective of this project is to predict the temperature distribution, the phase front distribution along the tube and to analyze the effect of fin density on the dynamic performance of the system. In the experimental arrangement of the tube configuration, three different fin spacing, 10 mm, 20 mm and 30 mm, of similar fin diameter, 30 mm, and length, 140 mm are considered. All experiments performed with HTF temperature at approximately 5 oC and flow rate of 6 litre/ min. The present project obtained solid volume of ice through CAD modeling from captured images of the solidification phase front. Data digitization program, Digitize it! ‘2004, was used to obtain the coordinates along the solid-liquid interface of the solidification whose data was transferred to SolidWorks for modeling ice volume in the test vessel. Total thermal energy stored in the vessel and frozen volume fraction was computed from the approximated volume through this methodology. This methodology accounts for an error of 1.1 %. The temperature distribution along the finned tube was obtained from the temperature-time recorded data of a set of thermocouples fixed at the base and tip of the finned tube. The ice layer growth at the first instants of solidification process is much higher. Thereafter, it decreases gradually according to the increasing thermal resistance of ice layer. The spread of solidification across the finned tube with greater fin spacing (lower fin density) is more uniform than finned tube with smaller fin spacing. Formation of ice layer is relatively proportional throughout compared to those produced by horizontal finned tubes. Solidification of PCM tends to delay more significantly in finned tube with higher fin density as more homogenous temperature between fin surfaces and PCM temperature is promoted. Based on experimental results, regardless of time delay in energy creation or solidification around finned tube with different fin densities, all systems will eventually follow a limiting curve of total energy created with respect to time.