管式换热器列管结垢导致传热系数上升，故换热效果降低。
参考答案：错
—What about your self-drive trip yesterday?
—Tiring! The road is being widened, and we ______ a rough ride.
A．had
B．have
C．would have
D．have had
BX-30型变压器的额定容量为（）VA。
A、40
B、30
C、35
D、10
