Simplified methods in the estimation of the K-value of insulated cargo holds on ships

摘要

The problem of buried steelwork in cargo hold insulation has been investigated by several using empirical methods. These efforts have resulted in correction factors that serve as a useful aid in the complex task of estimating the K-value of a ship's cargo holds for the correct dimensioning of the refrigeration plant. Today, the advent of the digital computer has established numerical methods of analysis as a common working tool among practicing engineers. For estimating the flow in cases of buried steelwork that cannot be handled by correction factors, this is an effective approach. This study is an analytical/numerical investigation of the effect that buried steelworks have on the heat leakage across cargo hold walls. It aims at providing enlightenment on the physical significance of the parameters influencing the problem and developing practically simple methods for predicting the heat leakage across the hold walls. The study is set in the steady temperature in a rectangular layer of insulation, and investigates the mechanisms by which changes are caused in this temperature as a result of penetration by a steelwork. This approach is used to explain some known characteristics of buried steelwork in hold insulation and develop simple equations for estimating the heat leakage across hold boundaries. The calculation procedure due to Joelson, which has been found to predict heat flow rates reasonably, is reviewed and discussed. The accuracies of equations deduced from this study are compared with numerical solutions, Joelson's method and the correction factors developed by Bo Pierre using electrical analogue techniques. For practical estimation of a ship's K-value, the calculation procedures presented should be simple to work with. 23 refs., 27 figs., 11 tabs.