| Exhaust air energy recovery is an important energy-saving technology in fresh air handling. Among all kinds of fresh air handling equipment, direct evaporation all fresh air handling unit is widely used for convenient installation, long service life and stable performance. Applying a rotary air-to-air energy exchanger to the all fresh air handling unit is not only beneficial to make full use of their advantages,but also helpful to reduce energy consumption of fresh air and ensure handling performance of fresh air, which is of great significance to energy conservation and emission reduction. In this paper, experimental research on the energy-saving effect of joint operation of rotary air-to-air energy exchanger with all fresh air handling unit was carried out.Firstly, heat exchange mechanism and heat transfer performance of the rotary air-to-air energy exchanger were discussed in detail, and then theoretical analysis of handling effect of joint operation was carried out. The air handling process line under joint operation and curves of refrigerating capacity with the change of fresh air temperature were described, and the most prominent energy saving potential of the joint operation was found out.Based on the theoretical analysis, experimental study on joint operation in working conditions was conducted under cooling and heating operating mode, respectively. The variable fresh air working condition is mainly concerned about under cooling mode, and is only considered under heating mode. Energy-saving evaluation parameters include outlet air temperature, cooling capacity and comprehensive energy efficiency ratio. The experimental results showed that unit capacity increased at least 2kW, comprehensive energy efficiency ratio increased not less than 12.7% in the variable fresh air conditions. The fresh air temperature dropped as energy wheel recovered energy from exhausted air, which affected the performance of refrigeration system. The experimental results suggested that refrigerating capacity of whole system increased with the increasing fresh air temperature, but change of coil refrigerating capacity is not obvious. As to change return air conditions and wheel rotation speed, its essence was to change the amount of the energy which the energy wheel recovered from exhausted air. With return air temperature increasing, the energy which the energy wheel recovered decreased, but the coil refrigerating capacity increased. As a result, outlet air temperature difference was little. The change of wheel rotation speed had little influence on the whole refrigerating capacity. Under winter variable fresh air conditions, due to big air temperature difference between indoor and outdoor, energy-saving benefit using wheel heat recovery was obvious, and comprehensive energy efficiency ratio increased more than 11%.Finally, exergy cost of all fresh air handling unit was analyzed using principle of thermo-economics, calculation results showed that under nominal refrigeration operation condition, total exergy cost was reduced by 22.7% after turning on the energy wheel. Trend line of total exergy cost with the change of fresh air temperature under the refrigeration operation conditions was drawn, the data showed the total exergy costs significantly reduced when coupled with the energy wheel, and with fresh air temperature increasing, the total exergy cost reduced more obviously.In this paper, experimental research of the joint operation of rotary air-to-air energy exchanger and all fresh air handling unit were carried out which verified its energy saving potential and technical and economic feasibility. The study results could provide design reference for practical engineering application.
|
PDF Full Text Request