In order to the evaluate heat loss from hot water supply lines in a residential building, hot water demand in a house in Chiba prefecture was measured and analyzed. The following results were obtained.
1. The heat loss of the hot water supply line was about 132kJ for the shower and 110kJ for the bathtub in winter. Since the temperature difference between the inlet and outlet of the hot water supply line is small, the measured heat loss from the hot water supply line sometimes becomes negative.
2. In order to estimate the heat loss under various conditions, a thermal model was proposed.
3. The calculated daily heat loss of the hot water supply line was 122kJ for the shower and 689kJ for the bathtub in winter. The average daily heat loss from the hot water supply line during use and after use was 1774.7KJ in winter. This heat loss amounts to 4.7% of the total daily energy use for hot water supply.
4. For reducing the heat loss, thermal insulation of the hot water supply line and the use of thinner pipes are effective