Study On Cooling Performance And Durability Of Bamboo Packing In Cooling Tower

Cooling tower is a kind of cooling equipment which is widely used in industiral field and has the ability of energy saving and heat rejection.As the core component of cooling tower,the cooling packing is responsible for 60-70%of the heat dissipation in the cooling tower.The type of cooling packing has an important influence on its cooling performance.Currently the most popular cooling packing in market is PVC film packing,but it has a short service life,poor anti-fouling properties,environmentally-unfriendly and other shortcomings.It is urgent to find an alternative to PVC film packing with long service life,low production cost and friendly environment.In recent years,bamboo as a cooling packing has been used in many hyperbolic cooling towers in China.Practice has proved that bamboo packing?BP?has the advantages of long service life,good cooling performance,low cost and environmentally-friendly,it is a kind of cooling packing with great potential for development.Although the BP has been used in cooling towers,there was no report on the effect of hygrothermal environment in the cooling tower on the properties of the BP.Among them,the durability of BP is a core problem when it is applied,because it is closely related to the service life of cooling packing.In addition,there were few studies on the thermal performance,resistance characteristics and structural innovation design of BP.The lack of these studies significantly affected and limited the application and promotion of bamboo as cooling packing in industrial cooling towers.In order to fill the research gap mentioned above,bamboo as raw material,according to the relevant standards,was made into traditional BP in this research.The thermal and resistance characteristics of BP were tested.BP and several common PVC plastic film packing were compared and analyzed.Simulating the working environment in cooling tower,and the BP was treated with hydrothermal accelerated aging.The changes of mechanical properties,microstructure,chemical composition and structure of bamboo before and after aging treatment were analyzed,and compared with BP used in cooling tower for nine years.The degradation of mechanical properties,aging mechanism and durability of BP were studied.Finally,an innovative design of traditional BP was carried out.The main conclusions are as follows:?1?The thermal performance of BP is good,and its resistance characteristics,aging resistance,service life,physical and mechanical properties,anti-pollution ability,cost of production and environmental-friendliness were significantly better than PVC plastic film packing.So BP can be used as an excellent alternative to PVC plastic film packing.?2?The mass loss rate of bamboo increased with the increase of accelerated aging temperature and time,while the density and mechanical strength decreased with the increase of temperature and time.The maximum decrease of chord MOR and chord MOE reached 48.49%and 36.09%,respectively.The mechanical strength of bamboo could be predicted by exponential regression equations.?3?With the increase of aging temperature and time,the morphology of parenchyma cells changed from nearly round to irregular shape,the gap between the intercellular layer of parenchymal cells gradually expanded and the amount of starch in lumen of parenchymal cells was decreasing.The microstructure of bamboo changed most significant after accelerated aging under 90?and 64 cycles.?4?With the increase of aging temperature and time,the relative content of?-cellulose and lignin in bamboo was on the rise,and the relative content of hemicellulose and benzene alcohol extractives decreased.There was a strong correlation between mass loss rate and?-cellulose,hemicellulose and benzene alcohol extractives.The relative content of main chemical compositions of bamboo after accelerated aging could be inferred by the mass loss rate.Accelerated aging temperature and time had a significant effect on the chemical structure of bamboo.With the increase of aging time,the functional groups in hemicellulose decreased significantly,and the C-H bonds,C-O bonds in cellulose and aromatic nucleus in lignin were also hydrolyzed partially.The FTIR spectra of bamboo changed most significant after accelerated aging under 90?and 64 cycles.The surface color of bamboo also changed significantly after accelerated aging.?5?After being used for nine years in cooling tower,the density and mechanical properties of BP decreased to a certain extent,but it still could meet the normal application requirements of relevant standard.Its mechanical strength and service life could be calculated according to the exponential regression equation of accelerated aging.Although the microstructure and content of starch in the BP changed obviously,it was hardly affected by the corrosion of rot fungi.?6?The change of chemical composition of BP was consistent with that of accelerated aging bamboo.The relative content of?-cellulose and lignin in BP increased,while the relative content of hemicellulose and benzene alcohol extractives decreased.FTIR analysis results indicated that the aborption peaks of the BP at 1730 cm^-1,1370 cm^-1,1240 cm^-1 and 1048 cm^-1were significantly lower than that of the untreated control sample.The FTIR spectra of BP was similar to that of bamboo after accelerated aging under 60?and 24 cycles.Some functional groups of?-cellulose,hemicellulose and lignin were degraded by circulating cooling water.?7?The cooling number and bulk coefficient of bamboo weaving packing were lower than that of traditional BP,while its resistance characteristics was better than that of traditional BP.Through comprehensive analysis,the newly designed bamboo weaving packing has advantages over traditional BP in cooling performance,production process,service life,mechanized production and cost of production.In summary,this study preliminarily revealed the influence rule of heat treatment temperature and time on the related properties of bamboo packing.By comparing the artificial accelerated aging method and natural aging method in cooling tower,the degradation law of physical and mechanical properties and aging mechanism of bamboo packing were studied,the service life of bamboo packing in cooling tower was deduced and the gap in the research on the durability of bamboo packing was filled.Structure optimization of bamboo weaving paking,which has been simplified the production process,reduced production costs,improved the cooling performance,is expected to replace the traditional bamboo paking.