Performance analysis of the refrigerant-cooling radiant terminal: A numerical simulation

The existing radiant cooling systems have the drawback of low energy efficiency due to its secondary heat exchange via chilled water. To overcome this dilemma, a novel refrigerant-cooling radiant terminal (RCRT) system utilizing the refrigerant as direct medium is proposed. A detailed numerical model is established to describe the heat transfer characteristics of this system and validated with the experimental data. The influences of the operating parameters and indoor ambient parameters on thermal performance of the RCRT system are analyzed based on the numerical model. Results show that the proportion of sensible, latent and radiant cooling capacity of this system is 55.5%, 17.3% and 27.2%, respectively, which indicates that natural convection is the main contributor in the heat transfer process. Additionally, a method for design parameters determination of the RCRT system is provided and a simplified characteristic equation is proposed to conveniently evaluate the cooling performance of this system in engineering application. The comparisons of cooling performance are conducted by an assessment index between the RCRT system and other cooling systems. Results show that the cooling capacity per unit projected area of the RCRT system is superior to chilled water radiant cooling systems, while inferior to forced-convection air-conditioning systems.