| This paper takes a practical project as an example,studies the energy-saving problem of heat recovery of fresh air ventilator.Firstly,theoretical analysis is carried out.The applicability of heat recovery method for fresh air ventilator is analyzed.Considering the climatic characteristics of Shenzhen,the outdoor air temperature and enthalpy are higher than the indoor design value,which belongs to the third zone of applicability of heat recovery from fresh air exchange.After analysis,the heat recovery mode of fresh air exchanger should adopt total heat recovery mode.Through theoretical calculation,the energy-saving capacity of the commercial part of the building is 36.6 kW,and the energy-saving rate of the commercial part is 2.4%.The energy-saving capacity of office is 311 kW,and the energy-saving rate of office is 4.5%.The energy-saving rate of office is higher than that of business.The energy-saving capacity of the whole building is 347.6 kW,and the energy-saving rate of the building is 4.1%.The economy of heat recovery of fresh air ventilator is calculated.The refrigeration operation period of the whole year can save 869000 kWh and 76.1 million yuan,and the investment of equipment can be recovered in about 1.3 years.Then the simulation analysis of energy consumption is carried out.Using DeST software to establish the model,the local outdoor hourly dry-bulb temperature is obtained by simulation.The average dry-bulb temperature of each month is calculated and the hottest month is July,and the average monthly temperature is 28.81℃.When the control temperature of air conditioning is 26℃,the accumulated air conditioning degree days are 282.35 day and the air conditioning degree hours are 8542 hour.The energy consumption saved by heat recovery of fresh air ventilator is simulated and analyzed.The energy-saving capacity of the whole building is 387.5 kW,the energy-saving rate is 4.5%,and the energy-saving rate is close to the theoretical value of 4.1%.The economy of heat recovery of fresh air ventilator is calculated.The refrigeration operation period of the whole year can save 766921 kWh,save 67.2 million yuan of electricity,and the equipment investment can be recovered in about 1.4 years.The running time of the simulation calculation is generated automatically according to the local outdoor meteorological conditions and indoor design temperature,which is closer to the actual operation of the project.At last,two different structures of heat exchanger of fresh air exchanger,counter flow heat exchanger core and cross and counter flow heat exchanger core,are simulated and analyzed by Fluent software,and the temperature field,velocity field and pressure field of the heat exchanger under the two structures are obtained.The results show that the sensible heat exchange efficiency of counter flow heat exchanger core is 69%,and that of cross and counter flow heat exchanger core is 75%,which is better than that of counter flow heat exchanger core.The counter flow heat exchanger core has the advantages of simple air passage structure,small pressure drop loss,convenient processing,easy mechanization and pipeline operation,simple maintenance and low cost.If the energy recovery efficiency of cross and counter flow heat exchanger core is higher from the point of view of energy saving,priority should be given to cross and counter flow heat exchanger core.At the same time,the energy recovery efficiency of cross-countercurrent plate heat exchanger at different flow rates is analyzed.It is concluded that the energy recovery efficiency of fresh air exchanger tends to decrease with the increase of flow rate.The research content of this paper can provide theoretical guidance for the application of fresh air ventilator in practical engineering and the development of practical products. |
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