The present invention relates as indicated to a heat exchanger, and more particularly to a heat exchanger finding particularly advantageous use in residential dwellings or commercial installations having an air-conditioner or heat pump. 
Inherent in the operation of an air-conditioning system or heat pump is the creation of waste heat which is normally dissipated to the atmosphere.  In a typical installation, a central air-conditioning system will have the compressor and finned condenser tubes located in a housing positioned in or near the dwelling, with the evaporator coil being positioned within the house for circulation of air thereover by a circulating fan to cool the entire enclosure.  A heat pump, which is finding increasingly greater uses due to the versatility thereof, is essentially the same except that the system is reversible whereby the interior coil can be cooled or heated as desired.  When the heat pump is used for air-conditioning purposes, the coil located outside of the house functions as the condensing coil and similarly creates heat, which is dissipated to the atmosphere by a fan. 
The basic objective of the present invention is to efficiently employ the waste heat from the refrigerant by providing heat exchange apparatus in which the hot refrigerant gas is passed in heat exchange relationship with water used interiorly of the house and which is normally heated by independent, energy-consuming means such as gas or electricity.  For example, the heat exchanger in accordance with the present invention is particularly adapted to augment the heat source for the domestic water heater thereby reducing the energy requirements for heating the water.  Concomitant with the reduced energy requirements for water heating is the reduction in temperature of the refrigerant due to such heat exchange, thereby making the refrigeration cycle more efficient and therefore less demanding on the compressor, a very significant commercial advantage. 
The basic concept of employing waste heat from a refrigerant compressor for heating water is well known in the art.  For example, U.S. Pat.  No.  2,690,649 to Borgerd discloses a coil which is tapped off from the high pressure side of the compressor 10 for passage through a water tank to heat the water therein.  U.S. Pat.  No.  1,937,288 to McGraw shows a similar arrangement, and this basic concept of employing the waste heat for a heat pump or compressor is also shown in U.S. Pat.  Nos.  2,716,866 and 2,125,842. 
A further aspect of the present invention involves the interpositioning of coiled tubes containing refrigerant and water in a generally cylindrical assembly thereby to enhance the heat exchange between the refrigerant contained in one coiled tube and the water passing through the adjacent coiled tube.  The basic concept of providing adjacently disposed tubes through which pass different materials for purposes of heat exchange is disclosed in U.S. Pat.  No.  1,965,533 to Lear and in U.S. Pat.  No.  3,285,334 to Pasternak, although the use environments are substantially different than in accordance with the present invention.  U.S. Pat.  No.  2,621,903 to Cohler also discloses adjacently disposed coils of tube through which differing liquids pass for heat exchange purposes.  However, the relevance of Cohler is limited to this feature inasmuch as there is no complete heat exchanger structure disclosed in the patent.