Abstract: A hot water boiling apparatus includes a hot water storage tank. The storage tank has an inner tank storing water therein, an outer tank surrounding the inner tank, and a vacuum heat insulation layer defined between the inner and outer tanks and surrounding the inner tank. An electrically heated bubble pump unit is arranged outside the storage tank and used for drawing water from the inner tank through a water supply port formed at the bottom of the inner tank and, after heating the water, supplying it into the inner tank through a hot water supply port formed at the top of the inner tank. First and second connecting pipe respectively connect the bubble pump unit to the top and bottom water supply ports of the inner tank. The portions of the connecting pipes extending through the vacuum insulation space are oriented horizontally to minimize convection heat losses. The portion of the connecting pipe which passes through the vacuum heat insulation space is oriented horizontally.

Abstract: A hot water boiling apparatus includes a hot water tank filled with water. A water supply pipe and a hot water supply pipe are connected to the bottom and top of the tank, respectively. A bubble pump unit is arranged in parallel with the tank. The pump unit includes a body having a boiling chamber, electric heaters for heating the water in the chamber, a first connecting pipe for guiding water from the tank to the body, a guide pipe for feeding the water, guided through the first connecting pipe, into the boiling chamber, and a second connecting pipe for guiding the water heated in the boiling chamber into the upper portion in the tank. The guide pipe is arranged so that heat is exchanged between the water in the boiling chamber and the water flowing through the guide pipe.