Analysis of the heat-carrying performance of natural circulation loop using modified RELAP5/MOD3.4

Abstract

Since the successful manufacture of the separate heat pipe (also known as Two-phase Loop Thermosyphon or Natural Circulation Loop), it has been used in many applications, especially for waste heat recovery/remove and cooling systems. We use the modified system analysis program RELAP5 to study the medium-sized separated heat pipe setup MSL2 built by Seok-Ho Rhi. To better calculate heat pipe performance under low pressure, we have improved a series of models, including the bubble nucleation model, the heat flux partition model, the interfacial heat transfer, the drift flux model, the wall heat transfer model, etc. Then we use the low-pressure subcooled boiling experiment to verify the modified code. The validation results show that the modified code accurately captures the subcooling boiling phenomenon under low pressure and low flow conditions. We use the modified code to investigate the factors influencing heat-carrying performance and analyze their action mechanisms. The results show that heating power, volumetric filling rate, and cooling water temperature influence heat-carrying performance. Additionally, we analyze the heat pipe operating parameters over time to obtain the characteristics of the heat pipe at various stages.

Keywords

• Modified RELAP5
• Medium scale TLT
• Natural circulation loop heat transfer
• Low-pressure boiling