Marine Engineering test #2 material || 100% Verified Answers.
What are the 4 parts of a refrigerator system? correct answers Compressor, condensor,
expansion valve, evaporator
What are the stages of the refer cycle? correct answers 1) low pressure warm gas to
compressor
2) high pressure hot gas to condenser to be cooled , still high pressure
3) expansion valve with thermal bulb that is after the evap. Pressure after evap with thermal
bulb will move the evap valve. Reduce amount of refrigerant after valve, allows it to expand
towards evap low pres low temp
4) evap pulls warm air in room over cool evap pipes and boils refer where it goes back to
compressor
The expansion valve removes _______ from liquid refer to allow the refer to change state to a
_________ correct answers Pressure, vapor
What does the expansion valve do? correct answers Controls the amount of refer releases into
evap section
How does the sensing bulb work for evap valve correct answers Sits at outlet of evap section.
High temp and press of refer at this location causes refer in bulb from expansion valve to
expand and boil, tracked through capillary tube and opens the valve and increases refer flow
into evap.
The surface temp of the pipe on the condenser must be _______ than the outside temp correct
answers Hotter so that the heat on the confessor pipes will go to the outside. The condenser
ensure the pipes are hotter
WHAT TYPES OF HEAT EXCHANGERS DO WE PRIMARILY
FIND ABOARD SHIPS? correct answers Plate, air cooled / radiator, shell and tube
Shell and Tube Heat Exchanger correct answers a heat exchanger that has a cylindrical shell
surrounding a tube bundle
parallel flow correct answers occurs in a heat exchanger when the shell flow and the tube
flow are parallel to one another
Counter flow correct answers cooling medium and the cooled medium flow in opposite
directions
Mixed Flow correct answers process and coolant cross, parallel and counter
U-Tube Heat Exchanger correct answers
What percent of tubes can be plugged without a noticeable loss in efficiency? correct answers
10%
Advantages of Plate Type Heat Exchangers correct answers SIMPLE AND COMPACT IN
SIZE
, •
TURBULENT FLOW HELPS TO REDUCE DEPOSITS
WHICH PROHIBITS HEAT TRANSFER
•
NO EXTRA SPACE IS REQUIRED FOR DISMANTLING
•
CAPACITY CAN BE INCREASED BY INTRODUCING
PLATES IN PAIRS TO THE HEAT EXCHANGER
•
A PLATE TYPE HEAT EXCHANGER IS MAINTENANCE
SIMPLE AND CAN BE EASILY CLEANED
Disadvantages of plate type HE correct answers DISADVANTAGES
•
O-RING/SEALING MATERIAL BETWEEN
PLATES LIMITS OPERATING TEMPERATURE OF
THE COOLER
•
OVER TIGHTENING OF THE CLAMPING BOLTS
RESULTS IN INCREASED PRESSURE DROP
ACROSS THE COOLER
•
INITIAL COST IS HIGH SINCE TITANIUM
PLATES ARE EXPENSIVE
Advantages of Shell and tube Has correct answers LESS EXPENSIVE THAN PLATE TYPE
EXCHANGERS
•
CAN BE USED WITH HIGHER OPERATING
TEMPERATURES AND PRESSURES
•
PRESSURE DROP ACROSS A TUBE COOLER IS LESS
THAN A PLATE COOLER
•
TUBE LEAKS ARE EASILY LOCATED AND PLUGGED
•
USING SACRIFICIAL ANODES PROTECTS THE WHOLE
COOLING SYSTEM AGAINST CORROSION
•
TUBE COOLERS ARE PREFERRED FOR LUBRICATING
OIL COOLING BECAUSE OF THE PRESSURE
DIFFERENTIA
Disadvantages of shell and tube HEs correct answers HEAT TRANSFER IS LESS
COMPARED TO A
PLATE TYPE COOLER
•
CLEANING AND MAINTENANCE IS DIFFICULT
SINCE A TUBE COOLER REQUIRES ENOUGH
CLEARANCE AT ONE END TO REMOVE THE
What are the 4 parts of a refrigerator system? correct answers Compressor, condensor,
expansion valve, evaporator
What are the stages of the refer cycle? correct answers 1) low pressure warm gas to
compressor
2) high pressure hot gas to condenser to be cooled , still high pressure
3) expansion valve with thermal bulb that is after the evap. Pressure after evap with thermal
bulb will move the evap valve. Reduce amount of refrigerant after valve, allows it to expand
towards evap low pres low temp
4) evap pulls warm air in room over cool evap pipes and boils refer where it goes back to
compressor
The expansion valve removes _______ from liquid refer to allow the refer to change state to a
_________ correct answers Pressure, vapor
What does the expansion valve do? correct answers Controls the amount of refer releases into
evap section
How does the sensing bulb work for evap valve correct answers Sits at outlet of evap section.
High temp and press of refer at this location causes refer in bulb from expansion valve to
expand and boil, tracked through capillary tube and opens the valve and increases refer flow
into evap.
The surface temp of the pipe on the condenser must be _______ than the outside temp correct
answers Hotter so that the heat on the confessor pipes will go to the outside. The condenser
ensure the pipes are hotter
WHAT TYPES OF HEAT EXCHANGERS DO WE PRIMARILY
FIND ABOARD SHIPS? correct answers Plate, air cooled / radiator, shell and tube
Shell and Tube Heat Exchanger correct answers a heat exchanger that has a cylindrical shell
surrounding a tube bundle
parallel flow correct answers occurs in a heat exchanger when the shell flow and the tube
flow are parallel to one another
Counter flow correct answers cooling medium and the cooled medium flow in opposite
directions
Mixed Flow correct answers process and coolant cross, parallel and counter
U-Tube Heat Exchanger correct answers
What percent of tubes can be plugged without a noticeable loss in efficiency? correct answers
10%
Advantages of Plate Type Heat Exchangers correct answers SIMPLE AND COMPACT IN
SIZE
, •
TURBULENT FLOW HELPS TO REDUCE DEPOSITS
WHICH PROHIBITS HEAT TRANSFER
•
NO EXTRA SPACE IS REQUIRED FOR DISMANTLING
•
CAPACITY CAN BE INCREASED BY INTRODUCING
PLATES IN PAIRS TO THE HEAT EXCHANGER
•
A PLATE TYPE HEAT EXCHANGER IS MAINTENANCE
SIMPLE AND CAN BE EASILY CLEANED
Disadvantages of plate type HE correct answers DISADVANTAGES
•
O-RING/SEALING MATERIAL BETWEEN
PLATES LIMITS OPERATING TEMPERATURE OF
THE COOLER
•
OVER TIGHTENING OF THE CLAMPING BOLTS
RESULTS IN INCREASED PRESSURE DROP
ACROSS THE COOLER
•
INITIAL COST IS HIGH SINCE TITANIUM
PLATES ARE EXPENSIVE
Advantages of Shell and tube Has correct answers LESS EXPENSIVE THAN PLATE TYPE
EXCHANGERS
•
CAN BE USED WITH HIGHER OPERATING
TEMPERATURES AND PRESSURES
•
PRESSURE DROP ACROSS A TUBE COOLER IS LESS
THAN A PLATE COOLER
•
TUBE LEAKS ARE EASILY LOCATED AND PLUGGED
•
USING SACRIFICIAL ANODES PROTECTS THE WHOLE
COOLING SYSTEM AGAINST CORROSION
•
TUBE COOLERS ARE PREFERRED FOR LUBRICATING
OIL COOLING BECAUSE OF THE PRESSURE
DIFFERENTIA
Disadvantages of shell and tube HEs correct answers HEAT TRANSFER IS LESS
COMPARED TO A
PLATE TYPE COOLER
•
CLEANING AND MAINTENANCE IS DIFFICULT
SINCE A TUBE COOLER REQUIRES ENOUGH
CLEARANCE AT ONE END TO REMOVE THE
