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A hot water storage tank (also called a hot water tank, thermal storage tank, hot water thermal storage unit, heat storage tank and hot water cylinder) is a water tank that is used for storing hot water for space heating or domestic use. A heavily insulated tank can retain heat for days.〔 Hot water tanks may have a built-in gas or oil burner system, or electric immersion heaters, or may use an external heat exchanger to heat water from another energy source such as a wood-burning stove or a district heating system. Water is a convenient heat storage medium, because it has a high specific heat capacity. Compared with other substances it can store more heat per unit of weight (and volume). Water is non-toxic and in many countries available free of charge or at low cost. Water heaters for washing, bathing, or laundry have thermostat controls to regulate the temperature, in the range of , and are connected to the domestic cold water supply. Where the water supply has a high content of dissolved minerals such as limestone, heating the water causes the minerals to precipitate in the tank; a water tank may develop leaks due to corrosion after only a few years. Dissolved oxygen in the water can also accelerate corrosion of the tank and its fittings. A hot water storage tank is wrapped in heat insulation to reduce heat loss and energy consumption. == Insulation == In general, the more ''thermal insulation'' the better, since it reduces standby heat loss. Water heaters are available with insulation ratings ranging from R-6 to R-24. It may be possible to add an extra insulating blanket or jacket on the outside of a poorly insulated water heater to reduce heat loss. The most common type of water heater blanket is fiberglass insulation with a vinyl film on the outside. The insulation is wrapped around the tank and the ends are taped together. It is important that the blanket be the right size for the tank and not block air flow or cover safety and drainage valves, the controls, or block airflow through the exhaust vent, if present. In very humid locations, adding insulation to an already well-insulated tank may cause condensation leading to rust, mold, or other operational problems. Modern water heaters have polyurethane foam (PUF) insulation. In countries where serviceability is very important, PUF capsules are kept between the inner tank and the outer body. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hot water storage tank」の詳細全文を読む スポンサード リンク
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