An ocean-going tanker is to transport liquefied natural gas at about -160 C. To
ID: 2995787 • Letter: A
Question
An ocean-going tanker is to transport liquefied natural gas at about -160 C. To reduce the rate
of cargo evaporation, a complex arrangement to integrate insulation, liquefied natural gas
containment to prevent leakage, and pressure-resisting structure usually is provided in addition
to a hull. In this case, the complex arrangement might not be needed since without it an
insulating ice will form between the hull and the seawater. An objection to the ice-layer concept
is that with ice at 0C, seawater at about 15C, and substantial heat transfer coefficient between
them, the resulting heat flow would evaporate the cargo at a rate far in excess of that needed to
fuel the propulsion engines.
Is there a way around this objection? Could a refrigeration machine be installed in the
hull (or at an intermediate position in the ice layer) to pump out inflowing heat in excess of that
needed to evaporate natural gas for propulsion and refrigeration-drive engine fuel? What could
be done to provide a
Explanation / Answer
The most appropriate way for this situation is to introduce a material with very less heat transfer coefficent so as by that heat transfer will be very low and hence no evaporation can take place.
Yes a refrigerator can be used in this place.
To obtain stagnant layer adjacent to ice proper material selection corresponding to low heat transfer coefficent and hence low temperature will be maintained inside and hence stagnant layer of ice will be obtained.
Optimum cruise speed corresponding to this situation will be very low since heat transfer coefficent will be very low.