Stacket-up type heat exchanger for a gas boiler

A stacked-up type heat exchanger for a gas boiler comprising a bottom plate, a first plate, a fourth plate and a top plate wherein:

• the bottom plate includes one or more combustion gas flue(s) for carrying exhaust gas burned in a burner, a return heating-water outlet for concentrating heating-water and expelling it, and a cold-water inlet for delivering cold-water;
• the first plate includes a combustion gas flue communicating with the combustion gas flue of the bottom plate, one or more heating-water inlets for delivering heating-water, annular cavity which faces downward, is concave in cross-section and which forms a ring-type pipe by fitting together with a fourth plate illustrated below, and a cold-water supply pipe, one end of the cold-water supply pipe being connected to the cold-water inlet and the other end of the cold-water supply pipe communicating with a lower part of a curved portion formed by the annular cavity;
• the fourth plate includes a combustion gas flue communicating with the combustion gas flue of the first plate, one or more heating-water inlets for carrying heating-water, annular cavity which faces upward, is concave in cross-section and which forms a ring-type pipe by fitting together with the annular cavity of the first plate, a hot-water delivery pipe disposed at an upper part of a curved portion formed by the annular cavity and communicating with a hot/cold-water flowing tube formed by the annular cavity being fitted together with each other;
• and
• the top plate includes a combustion gas flue communicating with the combustion gas flue of the fourth plate, a return heating-water inlet for delivering return heating-water into a heat exchanger, and a hot-water outlet connected with the hot-water delivery pipe.