单项选择题
A.stop the refrigerant from flowing B.force the refrigerant to flow C.cause the refrigerant pressure to rise D.cause the refrigerant pressure to fall
When the refrigeration demand is small,（）A.the expansio...
单项选择题When the refrigeration demand is small,（）
A.the expansion valve will move toward the wide open position B.the expansion valve will move toward the closing position C.the feeler bulb will conveys the high temperature D.the superheat degree will raise
When the heat load begins to increase, the needle valve...
单项选择题When the heat load begins to increase, the needle valve of an expansion valve will（）
A.move in an opening direction B.move in a closing direction C.either open or close D.not move at all
One of the main purposes of refractories in a boiler fu...
单项选择题One of the main purposes of refractories in a boiler furnace is to（）
A.help preheat the air for the furnaces B.help preheat the feedwater C.protect economizer from excessive heat D.prevent excessive furnace heat losses
