The bulb for the thermal expansion valve is located（）

单项选择题The thermal expansion valve responds to the（）

A.amount of superheat in the vapor leaving the coil
B.amount of superheat in the liquid
C.temperature in the evaporator coils
D.pressure in the evaporator coils

单项选择题The thermostatic valve has a throttling action, that is to say the valve can（）

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

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

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

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