Vapor-jet heat pump

A heat pump for use in heating residential, commercial or industrial buildings, industrial and agricultural processes and heating of water to moderate temperatures such as may be required in swimming pools or as a water pre-heater for any other use. The system includes a fuel consuming refrigerant boiler for producing a refrigerant in vaporized form at relatively high pressure, the output of the boiler being connected to a superheater and then to the primary jet of an ejector-type compressor. An evaporator unit exposed to ambient temperatures has its output line connected to an inlet of the ejector such that as the high pressure gaseous refrigerant flows through the nozzle of the ejector, a low pressure is created and the refrigerant from the evaporator is also caused to flow through the ejector compressor to a condenser where the refrigerant is allowed to give up its heat. The condenser is coupled in circuit with a receiver which holds liquid refrigerant and delivers same to the boiler and evaporator, all under control of fluid level or pressure sensitive switches governing the operation of a liquid refrigerant pumping means.

BACKGROUND OF THE INVENTION 
I. Field of the Invention 
This invention relates generally to a heat pump apparatus and more 
specifically to the design of a fuel burning heat pump system which 
utilizes an ejector device as the compressor mechanism therein. 
II. Discussion of the Prior Art 
Many forms of heat pumps are known in the prior art for removing heat 
energy from one location and dissipating it in another location. As such, 
the same device may be used for either heating or cooling a particular 
enclosed volume, depending upon the direction of flow employed. In a 
typical, prior art, installation used for heating an enclosed volume, a 
refrigerant is made to flow from an evaporator disposed outside of the 
volume, through a compressor and to a condenser disposed within the volume 
to be heated. When operating in a cooling mode, however, the direction of 
refrigerant flow is reversed such that the heat exchanger formerly acting 
as the evaporator now becomes the condenser and the heat exchanger 
formerly acting as the condenser serves as the evaporator. In the majority 
of prior art heat pumps, the compressor comprises an electric motor driven 
pump which receives refrigerant vapors at a lower pressure and which 
delivers gaseous refrigerant at a substantially higher pressure to a heat 
exchanger where liquefaction of the refrigerant takes place. 
It is also well known in the art that motor driven pump-type compressors 
may be replaced with a so-called jet compressor in which the liquid 
refrigerant is introduced into a boiler where it generates a vapor under 
high pressure which is delivered to the ejector. As this high pressure 
fluid passes through the nozzle, it creates a low pressure zone within the 
nozzle effective to draw gaseous refrigerant from an evaporator heat 
exchanger where it becomes mixed with the primary flow and transferring 
heat energy picked up at the evaporator unit to the condenser heat 
exchanger. 
SUMMARY OF THE INVENTION 
The present invention is considered to be an improvement over known prior 
art heat pump systems. It is an improvement over prior heat pumps 
depending solely or mainly on electricity for power because it is powered 
principally by combustible fuels which cost substantially less per unit of 
heat energy delivered. It is an improvement over prior ejector type heat 
pumps in the use of a refrigerant superheater which increases the ejector 
performance. It is also an improvement over prior heat pumps requiring 
supplemental electrical heat during extreme weather because it can bypass 
hot refrigerant to the point of delivery at the condenser, thereby meeting 
the severe weather requirements without supplementary heat. Specifically, 
the system of the present invention includes an indirectly heated boiler, 
the primary heat source being a fuel burning water heater. The heated (and 
vaporized) refrigerant from the indirect boiler is passed through a 
superheater receiving heat from the exiting combustion gases resulting 
from the combustion of fuel firing the water heater and then to the 
primary jet of an ejector compressor. The ejector, itself, comprises a 
venturi into which a primary nozzle admits a high velocity refrigerant 
vapor jet creating a partial vacuum for drawing vaporized refrigerant from 
the evaporator heat exchanger. Thus, the primary and secondary 
(evaporator) flow mix in the ejector and enter the condenser at a pressure 
intermediate their individual pressures. The output from the ejector 
couples to the condenser heat exchanger where the vapor is allowed to give 
up its heat energy to the ambient whereby liquefaction of the refrigerant 
material takes place. The liquid refrigerant exiting from the condenser 
flows into a storage device termed the "receiver" where it becomes 
available to flow through suitable control valves to replace the 
refrigerant that is leaving the evaporator. A boiler feed pump also draws 
liquid refrigerant from the receiver and forces it through a check valve 
into the refrigerant boiler on a re-circulating basis. 
In accordance with the preferred embodiment to be described, the 
refrigerant boiler receives its heat input from the flow of hot water 
through an indirect heat exchanger, the water being circulated by a small 
electric pump from a fuel burning water heater. The pressure in the 
refrigerant boiler is maintained by cycling the water circulating pump on 
and off. A suitable flow check valve prevents gravity circulation of water 
when the pump is de-energized. 
OBJECTS 
Accordingly, it is the principal object of the present invention to provide 
a new and improved heat pump unit for residential, commercial or 
industrial applications. 
Another object of the invention is to provide a heat pump utilizing the 
so-called jet pump compressor in which the performance of the jet pump is 
improved by the use of a refrigerant superheater. 
Another object of the invention is to provide a heat pump which is 
energized by the burning of conventional fuels. 
Still another object of the invention is to provide an improved heat pump 
having improved operating cost-effectiveness over known prior art designs. 
These and other objects and advantages of the invention will become 
apparent to those skilled in the art from the following detailed 
description of the preferred embodiment considered in conjunction with the 
accompanying drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the drawing, indicated generally by numeral 10 is a schematic 
representation of the heat pump system of the present invention. Included 
in the system 10 is an ejector unit 12 having a primary input jet 14, a 
secondary input tube 16, a throat section 18 and a diffuser section 20. 
The primary input jet 14 is adapted to be connected to a source of 
vaporized refrigerant which may conveniently be developed within a 
refrigerant boiler as at 22. The gaseous refrigerant is made to pass by 
way of the piping 24 through a superheater 50 which is a heat exchanger 
receiving heat from the exiting combustion gases and then to the inlet 
jet. The superheater performs the important function of additional heat 
recovery from the exiting combustion gases while also adding energy to the 
refrigerant entering the primary jet. This increases the enthalpy of the 
refrigerant, improving the efficiency of the ejector and reducing the 
probability of liquid droplet formation in the primary jet which reduces 
performance. 
In accordance with the present invention, the refrigerant boiler 22 is 
preferably of the indirectly heated type. That is to say, it includes a 
heat exchanger 26 in the form of many tubes through which the hot water is 
circulated and having a plurality of fins affixed thereto for providing an 
increased heat transfer surface. The heat exchanger 26 is arranged to 
receive hot water via tubing 28 from a water heater or boiler 30 which is 
preferably heated by burning any one of a number of possible fuels which 
may, for example, include heating oil, LPG coal, or natural gas. While 
convection currents may be sufficient to cause the flow of heated water 
from the water heater unit 30 through the heat exchanger 26 of the 
refrigerant boiler 22, it has been found expedient to include an electric 
motor driven pump as at 32 to ensure adequate flow rates. It is possible 
to control the temperature and pressure of the refrigerant in the boiler 
22 by modulating the output from the pump 32 by a temperature responsive 
control circuit 33 or, more conventionally, by thermostatically 
controlling the temperature of the water in the heater unit 30. A check 
valve 35 is used to prevent gravity flow in the lines when the pump 32 is 
deenergized. 
The high pressure vaporized refrigerant leaving the jet nozzle 14 creates a 
low pressure at the secondary inlet 16 to which an evaporator unit 34 is 
connected. The evaporator may be of conventional design and in that manner 
may comprise a heat exchanger in the form of thermally conductive tubing 
through which the liquid refrigerant is allowed to enter. A suitable 
blower or fan (not shown) may be associated with the evaporator for 
causing ambient air to pass over the heat exchange surface contained 
therein to thereby vaporize the refrigerant which, as can be seen, would 
be at a relatively low pressure and therefore would have a low boiling 
point. 
The vaporized refrigerant entering the ejector 12 via the secondary inlet 
16 mixes with the high pressure stream entering via the inlet jet 14 and 
passes through the ejector diffuser 20 to a condenser 36. Condenser 36 
typically includes a heat exchanger in the form of a predetermined length 
of tubing which may be bent in serpentine fashion or may comprise a 
plurality of tubes extending in parallel between an input header and an 
output header. It is also common practice to include a plurality of 
conductive fins which are in contact with the heat exchanger tubing to 
provide additional surface from which heat energy may transfer. Further, 
the condenser unit 36 may involve the use of a motor driven fan (not 
shown) for aiding in the dissipation of the heat energy contained within 
the refrigerant flowing through it. In this fashion, the refrigerant is 
converted from a gaseous phase to a liquid phase, the liquid being passed 
into a reservoir or receiver 38. Thus, the liquefied refrigerant becomes 
available to maintain the refrigerant level within the evaporator 34 and 
the refrigerant boiler 32. A pump, as at 40, facilitates the transfer of 
the liquid refrigerant. A solenoid valve 42 may be used to control the 
flow of liquid refrigerant into the evaporator 34 and, in this regard, the 
valve 42 may be float controlled to maintain a desired level therein. A 
check valve 44 connected between the outlet of the pump 40 and the inlet 
of the refrigerant boiler 22 may be utilized to prevent flow back from the 
boiler when the pump is off. An expansion valve 49 reduces the pressure of 
the liquid to the level desired in the evaporator. 
OPERATION 
Now that the overall construction of the unit has been described, 
consideration will be given to its operation. 
In the heating mode, the heat pump transfers useful heat from a relatively 
low temperature source such as outside air or ground or water by reducing 
the refrigerant pressure in the evaporator and making its temperature 
lower than that of the heat source. Under these conditions, then, heat 
energy is drawn into the refrigerant at the evaporator and is then pumped 
to a higher pressure level existing at the condenser 36 by operation of 
the ejector compressor unit 12. Specifically, high pressure refrigerant 
vapor is made to flow from the refrigerant boiler 22 through the 
superheater 50 to the primary nozzle or jet 14 into the 
converging-diverging throat 18. The high velocity vapor exiting from the 
primary nozzle 14 which is also a converging-diverging nozzle in proximity 
to the secondary inlet 16 creates a partial vacuum at that location 
tending to draw the vaporized refrigerant from the evaporator unit 34 
where it mixes with the vaporized refrigerant exiting the jet 14 and 
enters the condenser 36 at a pressure part way between their individual 
pressures. In flowing through the condenser unit 36, the refrigerant 
vapors are cooled and the heat given off is used to warm the volume in 
which the condenser unit is disposed. Ultimately, the refrigerant is 
converted back to its liquid phase and is fed into the reservoir 38 where 
it again becomes available to flow through the pump 40 and the valves 42 
and/or 44 to replace the refrigerant that is leaving the evaporator 34 or 
the refrigerant boiler 22. 
Thus, as the system is illustrated in the drawing, the refrigerant boiler 
22 receives its heat input from the flow of hot water through an indirect 
heat exchanger 26, the water being circulated by an electric pump 32. The 
pressure in the refrigerant boiler 22 is maintained by the controller 33 
cycling the water circulating pump 32 on and off. 
The fuel burning water heater 30 may burn any one of a number of fuels, 
including, but not limited to, natural gas, manufactured gas, liquefied 
petroleum gas, coal, fuel oil, etc. The fuel burner 30 is controlled to 
maintain the required water temperature by an immersion thermostat (not 
shown) contained therein. The water circulating pump 32 may be controlled 
by a space thermostat as at 31. For safety purposes, it may also be 
desired to include a pressure sensor in the refrigerant boiler 22 for 
controlling the temperature of the water in the unit 30. 
Any one of a number of common refrigerants may be utilized in the system of 
the present invention. Commercially available fluorocarbon refrigerants 
such as R-11, R-114 and R-113 are all useful, R-11, however, appearing to 
be the most compatible with practical requirements of the system, such as 
heat exchanger pressure ratings, pipe diameters and pressure ratios. 
While the system of the present invention is illustrated as utilizing a 
water heating unit as the source of heat for the refrigerant boiler, it is 
also possible to make the present invention operate effectively with a 
single high pressure fuel burning boiler wherein the refrigerant boiler 22 
would be directly heated by the burning fuel. The use of an indirect 
heating approach such as is illustrated in the drawings and described 
herein is preferred in that it obviates the need for special purpose 
components, especially high pressure fuel-fired heat exchangers and, in 
addition, provides a convenient means of controlling the vapor pressure in 
the refrigerant boiler. 
It is to be further noted that a bypass branch 46 is coupled between the 
output from the boiler 22 to the output of the ejector 12. When the valve 
48 is open, additional vaporized refrigerant can be made to flow for 
satisfying extremely high heating demand conditions, thereby eliminating 
the need for supplementary heat in the building in which the present 
invention may be utilized as the heating system. 
It can be seen, then, that the system of the present invention affords the 
advantage that the heat available from the burning of the fuel is 
delivered directly to the point of application in the condenser. In 
addition, the heat taken from the lower temperature source, i.e., at the 
evaporator, is also delivered directly to the desired point of application 
at the condenser. The "free" heat obtained from the atmosphere or other 
heat source with which the evaporator unit cooperates can substantially 
reduce the fuel consumption of the overall system, especially when 
compared to a conventional fuel burning furnace. A savings of 30% to 50% 
or more in fuel costs appear to be feasible. 
The foregoing detailed description has been given for clearness of 
understanding only, and no unnecessary limitations should be understood 
therefrom as modifications will be obvious to those skilled in the art.