A total heat exchanger is a ventilation device capable of heat recovery. It enables energy recovery from indoor exhaust air during ventilation, thereby reducing air conditioning load, as well as the capacity, investment cost, and operating expenses of air conditioning equipment. Its principle involves heat exchange between indoor air and outdoor fresh air through a heat exchange element, meaning it utilizes the residual heat of exhaust air to precondition fresh air. This effectively conserves energy while simultaneously addressing fresh air supply issues and improving comfort. A total heat exchanger consists of a heat exchange element, duct interfaces, a multi-blade fan, a fan motor, and an air filter.

   The amount of fresh air introduced into air conditioning systems, according to the "Energy Efficiency Design Standard for Public Buildings" GB50189-2015, using a typical office as an example—with an occupancy density of 4m2 per person and a fresh air volume of 30m3/h per person—generally accounts for about 30~40% of the total air conditioning load. This demonstrates that the fresh air load significantly impacts the capacity of air conditioning equipment. To minimize the effect of fresh air on the air conditioning system and achieve energy savings, the following two aspects can be considered during design:

 （1）Reduce the amount of fresh air introduced while ensuring indoor air quality. During preheating stages when fresh air demand is low or during periods of low occupancy, measures such as installing CO? concentration sensors can be used to limit fresh air intake, enabling energy-efficient operation.

 （2）Adopt bidirectional ventilation facilities with heat recovery functionality. Total heat exchangers play a significant role in reducing equipment capacity and achieving energy savings. By passing outdoor air through a total heat exchanger, it can be precooled and dehumidified in summer, and preheated and humidified in winter, leading to approximately 15~20% savings in air conditioning energy consumption.