单选题A solenoid valve used in a refrigeration system should be installed ().Awith the axis of the solenoid horizontal, sensing temperature of the box, and upstream of the thermal expansion valveBupright, sensing temperature of the box, and upstream of the thermal expansion valveCupright, sensing temperature of the box, and downstream of the thermal expansion valveDupright, sensing heat of the tail coil, and upstream of the thermal expansion valve

单选题
A solenoid valve used in a refrigeration system should be installed ().
A

with the axis of the solenoid horizontal, sensing temperature of the box, and upstream of the thermal expansion valve

B

upright, sensing temperature of the box, and upstream of the thermal expansion valve

C

upright, sensing temperature of the box, and downstream of the thermal expansion valve

D

upright, sensing heat of the tail coil, and upstream of the thermal expansion valve


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If the head pressure of a reciprocating refrigeration compressor is excessiveA.the relief valve should open before the high pressure cutoutB.the relief valve should open and allow the excess refrigerant to flow to the receiverC.the high pressure cutout switch should operate before the relief valve opensD.you should close the discharging valve

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材料:At 1800,the hydraulic steering system failed once again.The master realized he would require shore assistance to rectify the problem,and diverted towards Portland using the thruster to steer by.The weather at this time was south-south-west force 5.At about three hours later,the thruster drive unit failed due to a leaking fuel injector pipe on the power unit.This was replaced using the spare carried on board.Immediately following the engine restart,an adjacent fuel line failed causing shut down of the unit.With no fuel line spares available,the thruster power unit could not be used.The failure of this unit,and that of the main hydraulic steering system,left the vessel without any steering capability.At 2155,with the weather deteriorating and no steering,the master contacted the Portland Coastguard and a“Pan pan”message was broadcast.A tow to Portland Harbor was arranged and she arrived alongside at 0240 the following morning.The subsequent investigation found that the main hydraulic steering system failure was due to a seized shuttle valve in the main hydraulic solenoid valve block.The solenoid valve had been recently overhauled.It was thought that the“O”rings fitted to the shuttle valve were of either the wrong type or a defective one.The valve had seized in such a position that hydraulic pressure by-passed the system preventing use of the hand steering.问题:The vessel was steered by thruster because ________ failed.A.the hydraulic steering systemB.the solenoid valveC.the thruster driving unitD.the hand steeringThe time that the thruster drive unit failed was ________ hrs.A.1800B.2100C.2155D.0240When the hydraulic steering system failed,________.A.the hand steering system could still be usedB.the auto steering system could still be usedC.both hand and auto steering system were out of useD.neither and steering system nor auto steering system was out of useThe real reason that caused the hydraulic steering system to fail was that ________.A.no fuel line spare were availableB.the weather was deterioratingC.the“O”rings fitted to the shuttle valve were of either the wrong type or a defective oneD.the thruster power unit failed请帮忙给出每个问题的正确答案和分析,谢谢!

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