Analysis Of The Applicability Of Heat Recovery Ventilators In Different Climatic Zones Of China Under Unconventional Conditions

In recent years, indoor air quality has increasingly become the focus of people's attention, therefore, the fresh air level has been recommended by the new national standards for design of heating, ventilating and air conditioning. As a consequence, larger amounts of energy must be consumed to adjust outdoor ventilation air so as to keep building space remains within the thermal comfort zone. Besides, the same amount of indoor air, which has already been set to indoor set point should be exhausted outside directly, and thus causing energy waste. Therefore, air-to-air heat exchanger is used to save energy through preheating the fresh air.The total heat exchanger is a high effective heat recovery equipment. It uses a part of the energy of return air to preheat fresh air. Under the same conditions, the energy recovered by the total heat exchangers is greater than by sensible ones. However, the surface for heat exchange requires a good thermal performance and wet-nature, and the investment and maintenance costs of the total heat exchanger are higher than that of the sensible. i.e., the total heat exchanger is not an universal heat recovery set. The air-to-air total energy recovery system should be chosen reasonably in different climatic zones by considering the composition of sensible and latent heat in fresh air.With the improvement of people's life, indoor thermal comfort has receiving more and more attention recently, especially for public buildings. Although researches on temperature and humidity of indoor air are reported by many studies, the effect on the thermal comfort, such as clothing and age should be taken into account for improving indoor environment. Therefore the indoor thermal features were monitored and analyzed systematically during winter in Shanghai. The suitable temperatures for indoor thermal comfort of five typical cities was calculated and suggested by a computing program.In winter, for those large public buildings, indoor moisture and heat production is relatively high. If we still adopt the air heat recovery unit to preprocess the fresh air, it is possible to increase air conditioning loads. By choosing five typical cities in different climate zones in China, the variations of climate parameters and the fresh air load were calculated and analyzed based on the outdoor air temperature and humidity series monitoring. Then the application of the exchanger in different climatic zones was estimated. In summer, as the fresh air required to be dehumidified, the process is more complex than the case in winter and summer without dehumidification requirements. The different ways to handle fresh air to different parameters, make the different effections by varied heat recovery way. Considering the investment of the heat recovery unit, using expensive recovery units is unsuitable. In the present study, the characteristics of fresh air loads in different climatic regions for two combined systems, i.e., the cooled ceiling/displacement ventilation system and cooled ceiling/top-supply system, were discussed and obtained. Furthermore, the effects on energy recovery in different cities of four different conditions were compared, that is, use HRV only, ERV only and use the different combinations of the two ventilators, then a proposal of choosing air-to-air energy recovery system was recommended.