问题 问答题 简答题

选择液化槽盐水时需考虑哪几项指标?

答案

参考答案:

液化槽内盐水,称载冷剂或称冷媒,它是传递热量的媒介,由搅拌机或输送设备将之在液化槽内循环,所以在工作温度范围内须始终保持液态,即凝面点尽可能低,而沸点尽可能高。传递一定的冷量时,其载冷剂的流量要小,这样可减少搅拌机的电耗,故载冷剂的比热即热容量和导热系数要大,密度、粘度要小。再者载冷剂应有较好的化学稳定性,对设备,管路腐蚀较小。

多项选择题 案例分析题
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The journey two naval (海军) officers made some time ago to tile very deepest point on the earth makes us realize how much of the world still remains to be explored (探测). The two men went down several miles to the bottom of the Pacific Ocean hiding in a small steel ball called a “bathy-scaphe” to find out if there are any ocean currents (急流) or signs of life.

It was necessary to set ont early, so that the bathyscaphe would come to the surfacc in daylight, and so be easily found by the mother ship which would be waiting for it. The divers began preparations at dawn and soon afterwards, when all was ready, the steel ball disappeared under the surface of the water.

In time, the temperature dropped to freezing-point and the men trembled inside the ball. They kept in touch with the mother ship by telephone describing how they felt. Then, at a depth of 3 000 feet, the telephone stopped working and they were quite cut off from the outside world. At 30 000 feet, the men were surprised by a sudden, loud noise-------even the smallest hole in the ball would have meant instant death. Luckily, though, it was only one of the outer windows that had broken. Soon afterwards, the bathyscaphe touched the soft ocean floor, raising a big cloud of “dust” made up of different kinds of small, dead sea animals. Here, powerful lights lit up the dark water and the men were surprised to see fish swimming just above them quite untroubled by thc very large wate-pressure. But they did not dare to leave the lights on for long, as the heat from them made the water boil. Quite unexpectedly, the telephone began working again and the weak but clear voices of the officers were heard on thc mother ship. After a stay of thirty minutes the men began their journey up, arriving three hours later, cold and wet through, but none the worse for their experience.

小题1:The officers started their journey at dawn___.  

A.because they wanted to return to the mother ship in twenty four hours

B.because the sea then was calm

C.when the sun was not too strong

D.so that they could return before dark小题2:What did the officers find out at the bottom of the sea?  

A.They only found different dead sea animals.

B.They did find signs of life.

C.There was no signs of any life.

D.There was only dust.小题3:The journey to the bottom of the sea helped us to realize that______. 

A.much of the world hasn’t yet been explored

B.there are not any signs of life at the bottom of the sea

C.strong water-pressure has great effect on fish

D.powerful lights can not be turned on at the ocean floor without killing fish小题4:Which of the following is closest in meaning to “They were cold and wet through, but none the worse for their experience”?   

A.They were cold and wet through, which was the worst thing of all.

B.They were even worse than cold and wet through at the bottom of the sea.

C.Considering what they had just experienced, being cold and wet through was not too

bad.

D.For such an experience, being cold and wet through was not bad for them at all.