Abstract
The heating of liquids in tanks by means of heating-coils is very common. However, little is known precisely about the heat-losses and the required heating-surface, but the general opinion is that on the whole the heating-surface fitted at present is too big. To obtain the necessary information a test was carried out during the trial-trip of a 50,000 DWT tanker and measurements were performed in three heated cargo-tanks..
The heat-flow through the tank-walls was measured with heatflow meters. The mean cargo-temperature was determined by a pneumatic level measurement system. Furthermore the temperature was measured at many points, including various points in two longitudinal bottom frame compartments, one heated and the other non-heated. The heat supplied was determined by measurement of the steam-flow.
The measurements yielded much valuable information, including heat-transfer coefficients for all important tank interfaces. Heatbalances were prepared and gave a good idea of the distribution of heat-losses over the various tank-walls. Temperature-measurements showed that there is a stationary layer of cold oil on the bottom of the tank which restricts the heat-flow through the bottom. The coating of paint on the hull proved to be a factor that should not be overlooked in thermal resistance.
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