Boiling-water geothermal heat exchanger and boiling-water geothermal power generation equipment

A geothermal heat exchanger comprising:

• a water injection pipe installed underground and receiving water supplied from above ground;
• and
• a steam extraction pipe installed underground and contiguous to the water injection pipe, wherein the steam extraction pipe comprises a plurality of gushing ports;
• wherein pressure in the steam extraction pipe is decreased to an approximate pressure required by a turbine;
• an underground geothermal region supplying heat to water present in the water injection pipe to convert said water into a high-pressure hot water, wherein said high-pressure hot water is converted into a steam single-phase flow via the plurality of gushing ports and subsequently extracted from underground via the steam extraction pipe;
• wherein the steam extraction pipe is disposed inside the water injection pipe, and the steam extraction pipe is formed such that a diameter of the steam extraction pipe decreases in a downstream direction between the underground geothermal region and a ground surface;
• and
• a heat insulating portion in a region contiguous to a low-temperature region closer to the ground surface, wherein the heat insulating portion is created by formation of an air layer at an upper part of the water injection pipe by lowering a water level of the water that is supplied to the water injection pipe.