Heat-transfer considerations for large liquefied-natural-gas storage tanks

Natural gas is used worldwide as a practical energy source. In order to have a concentrated form of energy, natural gas is liquefied and stored under a pressure slightly above atmospheric and at a corresponding temperature just above its normal boiling point (112 K). This investigation presents a general steady-state study of the heat transfers into such a storage tank. Two mathematical models are proposed in order to help improve the thermal design process for such a tank. It is concluded that the aspect ratio (i.e. height-to-radius) of such a tank for the minimum rate of heat gains should be approximately unity. This value differs from the economically most favourable aspect ratio, i.e. that leading to the least total financial expenditure over the lifetime of the tank. However, the two models allow a complete simulation of the thermal costs. As the unit cost of fuel rises relative to other costs (e.g. for the construction of the tank), the overall most economic tank design approaches that of the optimal thermal design of tank as deduced in this investigation.