Operational Performance And Applicability Analysis Of Dual Cold Source New Fan Units For THIC Air Conditioning System In Hot And Humid Areas

In response to a series of problems existing in traditional air conditioning,domestic and foreign scholars have proposed a new analysis and design method for air conditioning systems——temperature and humidity independent control air conditioning system?referred to as THIC air conditioning system?.However,the THIC air conditioning system has high requirements on the room humidity control system,the new fan group needs to bear all the latent heat load and part of the sensible heat load,so the requirements for the new fan unit are higher.The direct use of cooling and dehumidifying new fan units has the advantages of simple system,low cost,and convenient operation and management;however,its low dehumidification performance limits its use.Therefore,many experts and scholars have proposed dual-cooling fresh air units.The main forms are dual-temperature surface-cooled new air units?using high and low temperature chillers as the cold source?,pre-cooled direct expansion new air units?the cold source of the pre-cooling section is high temperature chiller?etc.The current research on the dual cold source fresh air unit mainly focuses on the internal structure of the fresh air unit and the heat exchange efficiency of the surface cooler,and the performance of the dual cold source new air unit under different operating conditions and different outdoor air conditions throughout the year,and the applicability of the dual cold source new fan unit is still lack of systematic research.In this paper,in view of the above problems combined with the meteorological conditions in the hot and humid area?Guangzhou area?and the use requirements of the THIC air-conditioning system,a study on the dual cold source new fan unit is carried out.The details are as follows:Part ?:Based on the climatic characteristics of the hot and humid area,the wet load characteristics of the four different types of rooms in the area are analyzed.The four types of rooms in the office,high school teaching building,shopping mall,and hotel are compared with each other.It is large,and its requirements for the moisture content((9)of the fresh air supply unit are 5.52?10.83g/kg,5.29?10.29g/kg,2.79?7.84g/kg,6.18?11.59g/kg.The performance requirements of the new fan units when the four representative air-conditioned rooms adopt independent temperature and humidity control air-conditioning systems:shopping malls>high school teaching buildings>offices>hotels.Part ?:Through experiments on the dual-temperature surface-cooled fresh air unit and the pre-cooled direct-expansion new air unit?the pre-cooled direct-expansion new air unit is mainly for the pre-cooling section cooler?,the inlet temperature of the surface cooler and the water in the pipe are obtained the influence of flow velocity and oncoming wind speed on the operating performance and energy-saving potential of the double-cooling source new fan unit.The results show that the enthalpy difference and the moisture content difference of the inlet and outlet air of the two new fan groups decrease with the increase of the inlet water temperature and the frontal wind speed;increase with the increase of the water flow rate in the surface cooler tube;The water flow rate in the cooler tube has the greatest influence on the enthalpy difference and the moisture content difference of the inlet and outlet air,but it does not change linearly,but as the water flow rate in the surface cooler tube gradually increases,the inlet and outlet air enthalpy difference and The trend of increasing moisture content difference is becoming more and more gentle.For the dual-temperature surface-cooled new fan group,the adjustment of the operating conditions of the dehumidification section and the adjustment of the pre-cooling section operating conditions,the former has a greater influence on the total enthalpy difference between the import and export of the new fan unit and the total moisture content difference;The operating conditions of the pre-cooling section can better increase the ratio of the enthalpy difference and the moisture content difference assumed by the pre-cooling section.Under the experimental operating conditions,the enthalpy difference of the pre-cooling section of the dual-temperature surface-cooled fresh air fan unit accounted for 37.99?50.88%of the total enthalpy difference,and the enthalpy difference of the pre-cooling direct expansion unit accounted for 33.23?42.94%,with high energy saving potential.Part ?:According to the experimental results,the air supply moisture content of the dual-temperature surface-cooled new fan unit is about 7.52?9.82g/kg,and the air supply moisture content of the pre-cooled direct expansion fresh air fan group is about 5.98?8.80g/kg;pre-cooling the dehumidification capacity of the direct-expansion type new fan group is stronger than that of the dual-temperature surface-cooled type new fan group,and the application range is wider.And put forward two operation control modes of pre-cooling section variable outlet working condition and pre-cooling section fixed outlet working condition.Through simulation analysis,it can be seen that the dual-temperature surface-cooled new fan unit and the pre-cooled direct expansion new fan unit are in two operation control modes Both can meet the annual operating requirements;and after energy consumption analysis,it is found that the energy consumption of the pre-cooling section in the export condition is 5.42%lower than the energy consumption of the pre-cooling section in the fixed outlet condition;and the dual-temperature surface-cooled fresh air The energy consumption of the unit is 7.81%lower than the energy consumption of the pre-cooled direct expansion fresh air unit.