Abstract
Heat loss from hot water in intermittently used supply pipeline, which is common in residencial building, was studied by numerical calculation. After checking the accuracy of the calculation method, the calculated heat losses were compared with those calculated by the approximated method proposed by Yoshino. As the results, it became clear that Yoshino's method overestimates the heat losses. However daily mean heat loss can be estimated within 2 or 3% of relative error by the approximated method. Moreover the economical thickness of thermal insulation material are considered. As the results, it became clear that the economical insulation thickness is 1/5〜1/10 of that of the continuously used hot water supply pipeline.
