【正文】 ator is determined to be the cause. It may be necessary to _____. A. change the expansion valve adjustment B. readjust the water regulating valve to increase the flow of water C. purge air from the condenser D. clean the waterside of the condenser 1830 On small, low pressure, air pressors, the cylinders are usually lubricated by the _____. A. splash method B. mechanical force feed lubricators C. detached sump method D. internal cooling passages in the crankshafts and connecting rods 1831 To correct the condition of slugging and flooding back in a refrigeration system, it may be necessary to_____. A. readjust the discharge pressure B. clean the expansion valve screen C. add refrigerant D. adjust the expansion valve 1832 Power is defined as the_____. A. rate of doing work做功的速率 B. amount of force needed to overe friction C. amount of work acplished D. distance through which an object is moved *1833 Which of the listed devices would be installed at a control system air pressure reducing station? A. Moisture separator B. Vacuum breaker C. Lubricator D. Nonreturn valve 1834 Air line lubricators are used in pressed air systems to lubricate_____. A. the suction and discharge valves B. tools and equipment served by pressed air主要是汽缸和活塞的上部 C. air line reducing valves D. all of the above 1835 When a vessel is in drydock, the vessel39。s steering wheel on the navigation bridge is turned, the difference existing between the position of the wheel and that of the rudder is known as_____. A. proportional band B. the error signal(偏差信號） C. the reset signal D. feedback 1804 Which of the conditions listed represents the greatest effect of excess frost accumulation on the evaporator coils（蒸發(fā)器結(jié)霜能導(dǎo)致的最大影響） ? A. Keeps the refrigerated space cooler. B. Reduces the efficiency of the plant. C. Takes the load off the pressor. D. Has no affect on the system. 1805 In the design of hydraulic piping and equipment consideration is given to minimize turbulence in the hydraulic fluid, as this will cause_____. A. molecular fluid vibration B. energy losses C. wide pressure variations D. mechanical damage to control valves 1806 If a refrigeration pressor is running continuously without lowering the temperature in the refrigerated space, the trouble may be_____. A. a shortage of pressor oil B. warm food in the refrigerator C. excessive condenser cooling water D. a shortage of refrigerant 1807 Which of the valves listed should be used either in the fully opened or the fully closed position? A. A gate valve 閘門閥 B. A globe valve C. Any check valve D. Any needle valve 1808 Which of the following modes of heat transfer does NOT require any physical contact between a warmer and a cooler substance? A. Radiation B. Conduction C. Natural convection D. All of the above 1809 A gate valve installed in a pipeline should be_____. A. used in either the fully dosed or fully opened position B. installed with the stem down C. used for steam service only D. used to throttle or regulate the flow of liquid 1810 The movement of heat within a fluid, caused by the application of thermal energy, is called_____. A. radiation B. conduction C. convection對流 D. condoradiation 1811 Air pressor cylinder unloaders enable the pressor to_____. A. vary their speed according to temperature and load B. start and e up to speed before air pression begins C. change speed according to overload demands D. reduce pressed air charge density 1812 Which of the conditions listed will cause a refrigeration pressor to run constantly without simultaneously decreasing the temperature in the refrigerated space? A. Shortage of refrigerant oil. B. Slight shortage of refrigerant. C. Excessive condenser cooling water flow. D. Faulty expansion valve. 1813 Which of the listed methods of heat transfer takes place when two substances of different temperatures are in physical contact with each other? A. Radiation B. Conduction C. Convection D. Each of the above 1814 The unloading system on an air pressor will_____. A. increase pressor discharge pressure on demand B. increase pressor operating speed as necessary C. allow the motor to turn the pressor opposed only by friction D. reduce the pressor frictional load when starting 1815 A warmer than normal pressor suction line might be caused by_____. A. insufficient lubrication B. insufficient refrigerant C. excess refrigerant D. excessive opening of the expansion valve 1816 Which of the following conditions must exist for heat to flow from one object to another? A. The two objects must be in physical contact. B. The two objects must be the same size. C. There must be an existing temperature differential. D. There must be an existing weight differential. 1817 In the refrigeration system, a shortage of refrigerant is indicated by_____. A. the pressor short cycling on high pressure cut out switch B. high suction pressure C. high head pressure D. bubbles in the sight glass 1818 Condensate must be drained from the intercooler and aftercoolers of an air pressor because_____. A. the cooling effect of the condensate reduces the pressor39。39。s length B. be greatest in a single pass 單向 counter flow heat exchanger C. remain constant throughout