Research on the Heat Transfer Performance of Novel Prefabricated Concrete Modular Unit Walls

Prefabricated concrete modular construction represents the highest level of integration in industrialized prefabricated building systems. Owing to its exceptional degree of standardization， it possesses inherent advantages in industrialized production， automated assembly， and digital operation and maintenance. It serves as a crucial pathway for advancing "intelligent construction" and facilitating the green， low-carbon transformation of the building industry. This paper focuses on a novel prefabricated concrete modular structural system. Using ANSYS software， a finite element analysis was conducted to evaluate the thermal performance of the exterior walls in a modular unit. This study revealed the influence of factors such as dry connectors and external insulation layers on the wall's thermal performance. It also analyzed the local thermal bridges induced by dry connectors under various external insulation configurations and investigated applicable calculation methods for the average thermal transmittance （U-value） of the modular unit's exterior wall. The results indicated that under cold climate conditions， box-type connectors create local thermal bridges， increasing the average U-value at the structural frame sections by 3.4%. As the thickness of the external insulation layer increased， the thermal bridge effect was gradually mitigated. The relative error between the one-dimensional area-weighted method and the three-dimensional simulation for calculating the average wall U-value decreased progressively. When the insulation thickness exceeded 30 mm， the error fell below 3%. When the external insulation thickness reached 70 mm， the average U-value of the exterior wall is 0.42 W/（m²·K），complying with the specified limit for the thermal transmittance of the external wall， as stipulated for buildings with more than 3 storeys in Design Standard for Energy Efficiency of Residential Buildings（DB 61/T 5033—2022）.