In cold weather the water seals of gasholders need protection from freezing to avoid compromising the seal. These holders have a large reservoir of "tank water" at the base which is below ground. At present freeze-protection is achieved by external heating of the seal water which is in a slotted channel called a cup. Electrical heating or circulation of heated tank water to the cup are examples of systems presently used. The tank water has a large thermal capacity and National Grid wishes to investigate whether circluation of the tank water without external heating could provide su±cient energy input to avoid freezing. Only tanks in which the tank water is below ground are investigated in the report. The soil temperature under the reservoir at depth of 10m and lower is almost constant.

Problem presented by
Bridget Hartley, National Grid

Study Group contributors
Ian Hewitt (University of Oxford)
Michele Taroni (University of Oxford)
Anja Slim (University of British Columbia)
John Byatt-Smith (University of Edinburgh)
John Ockendon (University of Oxford)
Peter Howell (University of Oxford)
Robert Bauer (University of Oxford)
Sapna Somani (Royal Academy of Engineering)
Mark Blyth (University of East Anglia)
Emilian Parau (University of East Anglia)
Richard Purvis (University of East Anglia)
David Parker (University of Edinburgh)
Poul Hjorth (Technical University of Copenhagen)