求翻译：亚临界自然循环锅炉水冷壁的安全性较好，有自补偿特性，而直流炉没有这种特性，因此，直流炉水冷壁管壁的冷却条件较差，较易出现过热现象。是什么意思？

Subcritical natural circulation boiler water wall of security is better, a self-compensation feature, but no such boiler characteristics, therefore, the wall of the cooling water wall boiler poor conditions, are prone to overheating.

subcritical boiler water-cooled walls of the natural cycle of security features is better, and have since compensation, and DC furnace is not the kind of properties, and therefore, DC heater water-cooled squash pipe wall cooling conditions are worse in overheating prone.

The subcritical natural circulation boiler water cooling wall security is good, has from the compensation characteristic, but directs current stove not this characteristic, therefore, directs current the stove water tubes wall cooling condition to be bad, easy to appear the superheat phenomenon.

Asia security critical natural circulation boiler water wall of good, since compensation characteristics, and once-through boiler does not have this characteristic, therefore, once-through boiler water-wall tube wall of the poor cooling conditions, more susceptible to overheating.

Subcritical natural circulation boiler water wall of security is better, a self-compensation feature, but no such boiler characteristics, therefore, the wall of the cooling water wall boiler poor conditions, are prone to overheating.