Feature 2 | TANKER TECHNOLOGY Back to basics
When Hans Otto Holmegaard Kristensen, senior researcher at the Technical University of Denmark (DTU), decided to review the efficiency of tankers and bulkers over the last 20 years he expected a steady improvement, but the results startled the researcher and convinced him that naval architects must return to the basic principles of ship design.
S
hip design is supposed to improve as we learn new methods, technologies and design concepts, or so Kristensen
believed. So when he decided to calculate the Energy Efficiency Design Index (EEDI) numbers for tankers from 20 years ago up to the present day his expectation was that there would be discernible improvements to ship designs over the years. In fact what he discovered was that the
designs were getting less energy efficient as they progressed mainly because owners and economics were driving the design process, not hydro-dynamic knowledge. “It [ship design] was driven by more cargo and money rather than sound design principles,” he says. According to the DTU the most efficient
ships will have the lowest block coefficient (volume divided by length, beam and draught) possible, while the slenderness ratio (the length divided by the cubed root of the volume) will be as high as possible and the Froude number (velocity divided by the square root of ship length) should be as low as possible. In fact what Kristensen discovered when he
looked at the development of installed power on panamax tankers was that it had increased from a little under 9000kW in 1990 to over 12,000kW by 2010. In seeking a reason for the increase in power DTU discovered that vessel speeds have increased, the Froude numbers have increased, block coefficients have increased, but the slenderness ratios have decreased. Tis information led the DTU to conclude
that “common ‘naval architectural’ knowledge and guidelines have not been followed”. Essentially ships have become wider in
order to carry more cargo and extra installed power means they are faster, but the extra
The historic development of panamax tankers. 32 The Naval Architect March 2012
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52