Research On Operation Strategy Of Ventilation System Of Low Profile Cross Ventilated Barn In Summer

As an important part of the Low Profile Cross Ventilated(LPCV)barn,the fan-pad cooling system plays an important role in regulating internal environment of the barn.However,its operation regulation mode is still based on manual operation.Automatic control can better respond to the outdoor temperature changes and ensure economic,energy saving and reliable operation of LPCV barn.How to make a reasonable and efficient operation regulation scheme to realize automatic control according to the outdoor temperature changes,the characteristics of the fan-pad system and the requirements of the thermal comfort of the dairy cattle has become a problem worth studying.There is randomness and blindly copy of the fan-pad system operation scheme used in the existing LPCV barns at present,and it lacks a systematic study on the operating strategy of fan-pad cooling system.According to the current application situation of LPCV barn in the northern area of China,as well as the working principle and cooling effect of fan-pad cooling system,Shenyang region which is known as north latitude 40° gold pasture belt and gold milk source zone was taken as study site,while the fan-pad cooling system of more commonly used 6-row LPCV barn in local area was research object.The working conditions were divided for the whole summer.The fan-pad system model was built on the goal of the constant thermal comfort of the dairy cattle.The automatic control system was designed to ensure the high milk yield and the best enterprise benefit,and the summer operation strategy of the fan-pad system was formulated.The main work of the paper is as follows:Under the design condition,extreme hot condition and partial working condition in Shenyang in summer,the computational fluid dynamics(CFD)method was used to proceed numerical simulation of LPCV internal environment.Taking the range of thermal comfort of dairy cattle as a criterion and under the premise of full fan opening,the spray water temperature has been adjusted according to the simulation results.Then the fan-pad system operating parameters for any working conditions was determined and a set of relatively reasonable operation regulation scheme of wet pad spray water system of Shenyang 6-row LPCV barn was put forward.Then automatic temperature control design and economic analysis for the fan-pad system was carried out.Based on numerical simulation,the relationship between the spray water temperature and the ambient temperature inside barn has been obtained.The result shows that the wet pad spray water system should be closed when the outdoor temperature is not more than 23?under all fans turned on and the indoor environment can meet the thermal comfort requirements of the dairy cattle.When the outdoor temperature is greater than 23? and no more than 31.4?(design conditions),the wet pad spray water temperature should be 20?.When the outdoor temperature is greater than 31.4?and no more than 34?,the spray water temperature should be 18?.When the outdoor temperature is greater than 34? and no more than 36.1?(extreme hot condition),the spray water temperature should be 16?.The fan-pad cooling system summer operation scheme in Shenyang 6-row LPCV barn is determined according to the research results.At the same time,according to the operation scheme,the automatic temperature control design of the fan-pad system is carried out.The economic feasibility of the automatic control scheme is proved by the economic analysis.The research results can be applied to the automatic control and manual control of the fan-pad system of Shenyang 6-row LPCV barn,which can provide reference for the construction and operation regulation of LPCV barn in other areas and different rows.