Performance and Applications of Run‐Around Coil Heat Recovery System in Heating, Ventilation, and Air Conditioning—A Review

ABSTRACT Exhausting treated and conditioned air without any recovery wastes money, as air is costly to treat and deliver. Heat recovery techniques allow recovering a portion of the energy in the exhaust air, which reduces the required input power and saves operational costs, and even initial costs. As the world moves toward lower energy consumption, the focus is increasingly on heat recovery techniques. One of these techniques is the run‐around coil system, which consists of two heat exchangers coupled by a liquid loop. Compared with other types of heat recovery systems, the run‐around coil has received the least attention from researchers. This paper reviews most of the relevant and influential studies related to run‐around coil heat recovery systems. However, it was found that the effectiveness of the run‐around coil system is generally lower than that of other systems; therefore, most studies focus on improving system performance. Reviewing the literature shows that the most important factors affecting effectiveness and recovery capacity are the liquid flow rate and the antifreeze agent (glycol) concentration. Besides, it was found that integrating a run‐around coil system into a vapor compression refrigeration cycle is promising, as the coefficient of performance can be increased. Finally, further studies are required to test the effectiveness of this system in recovering power in cooling applications, as most studies have been conducted in cold climates.