The Study And Effect Testing On Air Distribution Of Multi-zone Air-conditioning In The Printing Industry With Large Space

Printing industry has a long history.Since the printing was invented in ancient China,printing industry has experienced constant changes,and now it has become an important part of the national economy.The printing plant is a typical large space building,in which the equipment covers a huge area and releases a large amount of heat,so that the air conditioning system should not only bear the hot and cold load from the envelopes and the staffs,but also bear the heat produced by the printing machine,as a result of significant energy consumption.Because of the form of heat source in the printing plant and the specificity of the process,it is especially urgent to find an air distribution,which can meet the cooling requirements of the upper part of the printing machine,but also the environmental condition in the lower staffs operating area,especially the demand for thermal environment when supplying hot air in winter.Based on the theoretical guidance of jet characteristics,thermal stratification and similarity,this paper starts with air distribution of stratified air conditioning mostly used in buildings with large space and adopts model test,numerical simulation and field measurement,focusing on air distribution modes of different heat source in the printing industry in summer and winter.The main contents are as follows:Firstly,adopting PIV(Particle Imaging Velocimetry)technology,the reduced scale test was taken to study the air distribution characteristics and air supply efficiency of stratified air-conditioning in the large space printing plant in summer.How do the variation of the air supply height,speed and the type of air outlet affect the air distribution of stratified air conditioning were analyzed.And the parameters for the air distribution simulation of printing plants are obtained.The results show that the airsupply effect is the best when the air supply outlet height and the building height ratio is1/3 in the summer condition.The optimum stratification effect can be formed when the air supply speed is 1.5 and 2.0m/s.The axial velocity of the rectangular air outlet decreases slowly and the range is far,but it is similar to the circular air outlet characteristic when the height-width ratio W/H is less than 5.However,present study shows that traditional stratified air conditioning has a poor air distribution performance in winter.Secondly,based on the different form of heat source of the printing plant,a new air distribution of multi-zone air-conditioning with modular air supply outlet was proposed.The influence of the changing temperature,form and angle on the air-conditioning effect in winter and summer was studied using numerical simulation method.The temperature distribution characteristics of the plant are discussed when the air conditioning supplies cold air in summer and hot air in winter.The results show that for surface heat source-based printing plants,using the lateral supply shutters and swirl diffuser with declining angle of 30° is the best solution both in the winter and summer;for high body heat source-based printing plant,using lateral supply shutters and swirl diffuser with declining angle between 45° and 60° is the best solution in summer;using lateral supply shutters and swirl diffuser with declining angle between 30° and 45° is the best solution in winter.Finally,based on an engineering project of a newspaper printing center in Xi’an,the field tests have been carried out in winter and summer.The horizontal and vertical air distribution characteristics in printing plant under three operating conditions including natural conditions,air conditioning supplying hot air in winter and supplying cold air in summer were analyzed,and the engineering application feasibility of air distribution of multi-zone air-conditioning was estimated.It is found in this paper that for the air conditioning operating condition in winter,this new type of air distribution effectively breaks the thermal stratification under the natural convection,and the average vertical temperature gradient in the plant is only 0.07 ℃ /m,solving the problem caused by present air-conditioning system in winter of unreasonable temperature distribution in the plant,which is hot in the upper zone and cold in the lower part.For the operating condition in summer,it forms an effective thermal stratification and is conducive to theeffective discharge of heat from the printing press.The multi-zone air-conditioning mode proposed in this paper provides an alternative and effective form of air distribution for the design of air conditioning system in printing plants;meanwhile it can provide design basis and technical reference of air-conditioning system for other types of large space buildings.