:numerical Simulation Of Tunnel Pasteurization Of Bottled Beer

It is very important for the guarantee of beer quality to maintain the biological stability of beer. The pasteurization is usually used to kill the microorganism inside the bottled beer in the industry, which keeps the biological stability of beer. For the pasteurization of beer, in our country the most widely used method is tunnel pasteurization that has the advantage of low requirement for brewing and package.The superheat phase of tunnel pasteurization of bottled beer was numerically simulated,investigating the effect of different process parameters on the slowest heating zone（SHZ） and the temperature distribution inside the bottled beer. The influence of the three parameters, i.e.the temperature of spray water, the turbulent intensity of spray water at spray nozzles and the running velocity of bottles, on the temperature distribution inside the bottled beer was analyzed, using L₉（3⁴） orthogonal experiments. And then the single factor tests of the temperature of spray water, the turbulent intensity of spray water at spray nozzles and the the running velocity of bottles were conducted, on the basis of the results of orthogonal experiments, analyzing the effect of the three parameters on the slowest heating zone（SHZ）and the temperature distribution uniformity inside the bottled beer, respectively. Besides, the impact of the bottles spacing and the vertical distance between the nozzles and the mouth of the bottles on the SHZ and the temperature distribution inside the bottled beer was investigated too.The results of L₉（3⁴） orthogonal experiments indicated that only the temperature of spray water was the significant parameter affecting the temperature distribution inside the bottled beer while analyzing the temperature difference inside the bottle, and both of the turbulent intensity of spray water at spray nozzles and the temperature of spray water had obvious effect on the temperature distribution inside the bottled beer while analyzing the ratio of SHZ area.The results of single factor tests signified that the temperature of spray water had little influence on the position of SHZ, however, the uniformity of temperature distribution inside the bottled beer became worse and worse as the rise of the temperature of spray water. Both ofthe position and size of SHZ were not affected by the turbulent intensity of spray water at spray nozzles. However, it had effect on temperature distribution inside the bottled beer.When the turbulent intensity was 4.0%, the uniformity of temperature distribution inside the bottled beer was the best; When the turbulent intensity was 4.2%, the uniformity of temperature distribution inside the bottled beer was the worst. The running velocity of bottles had no influence on the position and size of SHZ, but not temperature distribution inside the bottle. In the uniformity of temperature distribution inside the bottled beer, the running velocity of bottles of 1 and 4 mm/s were preferable to others and that of 5 mm/s was worse than others.For the impact of the bottles spacing and the vertical distance between the nozzles and the mouth of the bottles on the SHZ and the temperature distribution inside the bottled beer, it could be inferred from the results that the position and the temperature of SHZ changed with bottles spacing. When the bottles spacing was 0 mm⁵ mm, 10 mm and 15 mm, their SHZ located at 1/3 filling height, the bottom of the bottle and 1/2 filling height respectively.Besides, the larger the bottles spacing was, the lower the temperature of SHZ inside the bottled beer was. When bottles spacing was 0, 5 and 10 mm（or 15mm）, the temperature difference inside the bottled beer become more and more large as the increase of bottles spacing. And the temperature difference of 15 mm was less than that of 10 mm, but its temperature was lower. Furthermore, the ratio of SHZ area was less inside the bottled beer for the bottles spacing of 0 mm. The vertical distance between the nozzles and the mouth of the bottles had no impact on the position of SHZ, but affected the its size greatly, i.e. the larger the spaces was, the larger the area of SHZ was. The distance of 200 mm got the temperature distribution inside the bottled beer more homogeneous than that of 300 and 400 mm.