CA1292214C - Heat pump heating system - Google Patents

Abstract

Abstract of the Disclosure A heating system employing a heat pump utilizes heat from the cows in a dairy barn as a low grade source of heat to heat a residence. A
closed loop circulation system between a heat ex-changer in a house and the heat exchanger in the barn employs a water-based heat transfer fluid.
This eliminates the need for long refrigerant lines running between the house and the barn. The heat exchangers in the residence convert the barn heat to Freon and transfer heat from the Freon to the residence. The house heat exchangers are divided into two sections connected in parallel to improve heat transfer and overall efficiency and reduce pressure losses.

Description

HEAT PUMP HEATING SYSTEM
Back~roun~ of the Invention The present invention relakes to heat pumps and the use of heat pumps to heat buildings. A dairy farm is disclosed herein as an example of a heat source. Other heat sources, such as solar or ground water, could be employed. It is known in the art to use a dairy barn as a source of heat to heat a resi-dence. U.S. Patent 4,263,785 is an example of the use 10 of heat from animals to increase the heat of Freon in a refrigeration circuit which is used with a heat pump for residential heating and other purposes. Commonly barns are located remote from the farm residence and very long refrigeration lines are required. Thesa 15 long lines use a substantial amount of expensive Freon and also are subject to freezing.
Climate control in dairy barns with uniform temperatures and humidity control are recogniæed ob-jectives for healthy and productive dairy cows. The 20 present system can be employed to assist in maintain-ing a desirable farm environment.
Su~mary of the Invention In accordance wikh the present invention there is provided a system for utilizing heat generat-25 ed by livestock in an agricultural operation to heat a residence, including a first heat exchanger located in the barn, a second heat exchanger located remote from the barn in a heat pump unit at the residence, a plumbing circuit for circulating a water-based trans-fer medium between the first and second heat exchang-ers in a closed loop, a third heat exchanger in the heat pump unit, a refrigerant circuit communicating with the second and third heat exchangers and includ-ing refrigerant coils in the sacond and third heat ex-:~Z~2~i~

changers, and a compressor associated with the refrig-eration circuit and a second closed loop plumbing cir-cuit for circulating water between the third heat ex-changer and a fourth heat exchanger which heats the residence; wherein each of the second and third heat exchangers in the heat pump unit is divided with sep-arate inputs and outputs for the divided units con-nected in parallel to the respective plumbing cir-cuits.
The heating system of the invention employs a heat exchanger system which avoids the need for re-frigeration circuits extending from the house to the barn. The input heat exchanger picks up the heat from the livestock or cows in the barn and the heat trans-fer fluid conveys the heat to the second heat exchang-er where the heat is given up to liquid Freon which is converted to a gas by the heat. The heat pump com-pressor increases the temperature and pressure of the gas which is released into a third heat exchanger where gaseous Freon converts to a li~uid and gives up its heat to a water-based transfer fluid in a second closed loop watar-based circulation systam which transers the heat from the Freon to an output or building air heat exchanger. Relatively short Freon refrigeration lines are involved between the second and third heat exchangers and the heat pump and asso-aiated components~ The long refrigeration lines to the barn in prior art barn-residence heating systems are eliminated. The use of water-based transf2r fluid improves the coefficient of performance of the system.
To further improve heat transfer and the co-efficient o~ performance, the second and third heat exchangers ara divided into two separate but adjacent units connected in parallel, with each unit having a separate input and output for both Freon and transfer fluid. This increases the residence kime of the transfer fluid in the heat exchangers to enhance heat transfer between the ~luid and Freon. The use of di-vided heat exchangers reduces the pressure loss which would occur in a continuous heat exchanger coil which would have the e~uivalent length o~ the two coils~
~he increased heat transfer ~rom the two closed loop water circuit~ to or ~rom Freon reduces the size com-pressor required and thus reduces the electrical ener-gy required to operate the system.
Other sources of heat such as a well, ground water or a solar collector can be employed. The in-vention also includes a control system operated by the building room thermostat and a transfer fluid conduit thermostat which allows the room heat exchanger to continue to give off heat to the room during the heat-ing cycle when the compressor is turned off and until the transfer ~luid drops in temperature within select-ed ranges. This mode of operation also increases the overall coefficient of performanae of the system.
Further objects, advantages and features of the invention will become apparent from the disclo~
sure.
Desoriptio~ of the Dra~in~
~ Fig. 1 is a diagrammatic perspective view o~
ths heating-cooling system of the invention.
Fig. 2 is a diagrammatic perspective view of the heating-cooling system of the invention and the heat pump circuit.
Des~ription o~ the Prererred Embodiment Although the disclosure hereof is detailed and exact to enable those skilled in the art to prac-tice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structure. The scope of the ~r ~?~

1 ~?22-14 invention is defined in the claims appended hereto.
In the drawings, Fig. 1 shows a house 10 and a barn 12. A plurality of heat exchangers 14 - are arranged over the stalls of dairy cows in the barn 12. The heat from the cows heats the working fluid circulating in the heat exchangers. The heat transfer fluid which has absorbed heat is conveyed by pum~ 16 through conduit 18 to a heat pump system generally designated 17. The heat pump system 17 upgrades the heat of the transfer fluid circulating through conduit 18 in a first closed loop water cir~ulating system. ~he compressor 94 upgxades the heat from the first system and a second closed loop circulation system is employad including conduits 24 and 27 to convey heated fiuid through a building or room heat exchanger 26. The heat exchanger 26 re-leases the heat into the interior 30 of the building 1~ during the heating cycle.
When using the system in the air condition-ing mode to cool the house, an outdoor heat exchanger 31 may be e~ployed ~hich removes heat ro~ the txans-fer fluid circulated through conduits 18 and 19 from the house. Usually the heat exchanger 30 is not re-quire~
~S More specifically, and referring again to tlle hea~ e~changers 14 as iilustrated in Fig. 2, the heat exchangers 14 ea-h include a plurality oE hori~on~ally exten~ing inned condu~ts 40 arrangad in a ver~ical plane and connected in parallel by headers 41. The individual units 14 can be connected in series, as illustrated in Fig. 1, or in parallel. The heat ex-changPrs 14 are desirably positioned over each stall or in spacefl l~cations in a ree stall dairy barn~ The banks of fins and conduits are located over a drip trough 5G 50 that the moisture will drip in'o a gutt~

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or trough 50 for disposal. The heat exchangers are positioned so that they pick up the convected heated air above the cows and the airt with heat removed, flows downwardly by gravity around the cow.
S The heated transf r fluid is conveyed by conduit 18 to a first transfer fluid-refrigerant heat exchange assembly 60 which includes first and second conduit coil sections 62, 64O The heat exchange coils 62 and 64 have transfer fluid inputs 61, 63 connected in parallel to the conduit 18. During the building heating cycle the flow of the heated fluid goes in the direction of arrow 65 into the inlets 61, 63 of each heat exchanger section 62 and 64. The heat exchangers 62 and 64 have concentrically located lS inside and outside 50ils with the conduit 18 connected to the outside coil which can be 1-1/4 inch plastic tubing and which carries the transfer fluid pumped from the barn. The inside Freon conduit 70 in each coil is preferably a 3/4 inch copper nickel tubing. The heat exchanger is si~ed an overall 26 feet per ton of capacity as compared with typical and conventiona]. heat exchanger ratio of 11 feet per ton, as hereinafter discussed.

The outlets 65, 67 of the transfer fluid conduit are connected in parallel to return line 75 by conduits 71, 73. Re urn line 75 returns the trans-fer fluid to the barn heat exchanger 14 or other heat source. The division of flow of the transfer fluid colls in heat exchange assembly 60 results in reducinq the velocity of the transfer fluid flow caused by circu-lation of pump 15, which thus causes an increase in residence time of the barn transfer fluid in heat ex-change relationship in the coil assembly 60. Because of the increased residence time, more heat can be transferred to the Freonv Similarly, the divided Freon coil increases the residence time of the Freon by reducing the velocity o~ the Freon. The increased residence ime of the ~'reon results in elevating the temperature of the Freon above that which would result from a lesser residence time in the heat exchange coils. The increased temperature increment also causes greater expansion of the Freon and higher Freon pressures delivered to the co~pressor. Hence the Freon introduced into the compressor has ~ higher temperature and prsssure than that introduced with the undivided coil. This reduces the amount of electrical energy required to operate the compressor and circulation pumps, thus increasing the efficiency over prior art heat pump constructions.
For example, with an undivided heat exchange coil the Freon entering the coil may have a pressure of 40 psig and that exiting the ooil a pressure of 45 p~ig.
The temperature of the entering Freon may be 18 F
and the exit temperature may be 28 F. With the divided coil asse~bly 60, as shown in Fig. 2, the pressure increase may be for example from 40 psi to 49 to 50 psi and the temperature increase from 18 F to 38 ~. To obtain a super heat of 20 F with an un-divided prior art coil, an increase in compre~sorcapacity and increase in circulation pump capacity would be required.
Based on actual tests with entering wat~r tempe~:atures of 50 F in a single heat exchanger coil v9. divided heat exchanger, the output with the singLe heat exchanger coil was 64,300 btuh and a COP of 3.61 and with a divided coil the output was 81,250 btuh and a significantly imp.o~ed COP of 4.9.
These benefics cannot be achieved by merely increa~ing the length o~ an ~ndivided heat exchange coil. The length of the conduit or coil through which Freon is circulated has to be matched with the com-pressor capacity or design back pressure for that com-pressor. A certain minimum pressure is required to S achieve return of all of the compressor oil which gets into the Freon pl~mbing system. Increasing khe length of the coil would result in increasing the total pressure drop and require a larger compressor to produce a lesser heat output which would decrease rather than increase the COP. Also, a larger circulating pump would be required. Dividing the heat exchange coil rgduces v810city and causes only a minimal pressure drop. Furthermore, the total pressure drop through the divided coil is less than that through a single coil of the same length because of the paralleling o~
flow and the reduction of the length of conduit the fluids must flow through. This minimization of pressure drop can enable use of even greater lengths of conduit to increase heat exchange between the transfer fluid and ~reon without causing an imbalance between com-pressor capacity and tot~l conduit length. For example, a conduit length of 26 to 28 feet per ton of compressor capacity is typically employed in commercial embodiments of the invention. Various prior axt units with an undivided coil employ 11 to 18 ~eet per ton. The divided heat exchangers and the reduction of pressure drop otherwise encountered also reduces the size of the circulatory pump required to move the transfer fluid betwee~ the input and output heat exchangers. This reduces the electrical power consumption of the total system.
During the building heating cycle ~Fig. 2), the liquid Freon is introduced into the heat ex-changers through conduit 72, with the Freon flowing in the direction of the ~rrow 74. The Freon flow i~

resulated b-~ an exparlsion va],ve 77 and one-way valve 78. The expansion valve has r~ temperature sensor control 80 and a tap 82 in line 84. The tap ~2 senses pressure and equali~es the system after shut-down. Duriny tlle heating cycle 9 the output Erom theheat excharlgers 52 and 6A is in the form o~ gaseous Freon which i~ conveyed by conduit 84 in the clirec~ion of arrow 86 to a reversinc3 valve 88. In the heating mode the gaseous Freon corlventicnally goes thrc~ugh a suctic-~n accumlllator 90 via conduit 92 and then to a compressor 94 where the temperature and pressure of the gas is xaised. The heated Freon leaves ~he heat pump t~hrou~h concluit 96 and goes through the revers-ing valve 88, throuyh conclui~ ~8 in thQ direction cf arrow 100, where it is lntroduced into a second divided h~a~ exchatlger asGe~bl~,~ having two coils 102 and 104.
Thi~ heat exchanger has similar dividecl coils with an inner Fxeon co~l and an out~r wa'er-alcohol coil.
The hea~ecl Freon is intro~ucecl to the inner coil 106 in which the E'reon giv9s OLf its heat to the water based .rall~f~r flu;.~ contai.ed in the outer coils 108.
The hea~ ~ransfer flui.d is m~ed through th~ wate~
co,.ls 108 b~ a pump 110 il~ line 24 which continuously ~irc~la~.es t:~le water du~inc3 the hea~ing moce througl-.
a water--to-air heat exchanger 26 anâ lines 24, 27 whic~, have a Einne~ co~duit 111 w.ith a blower 112 wrli.cl~ OWS ~ir through tl~e heated I ins into t};e room.
Tl~ reell soes thrc)ugh the recei~Je.r 114 a~.d .llen th2 expan6ion valve 77 an~ is returned to t,he he~.t exchanger~ 6~2 and 64 ~.~ia lin~ or ccnduit 7?. where it:
a~ain is gasi~ied.
The heating tnode is controlled b~ a roor~
thermos~at 123 and associated switche.s which contrG
~l7~ ~,ump llQ and heat e~char.ger ~lowers 112. The roo~l ; ~ 35 therm~stat puts thc revelsing valve it. the heating mode.

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_ 9 _ If the room thermostat calls for heat, pump 110 and blower 112 are energized and thermostat 200 is enabled.
If the temperature in the water line 27 is less than the set point of for example 86 F, the compressor 94 will be energized. The pump 16 in the barn circuit is connected by a circuit so that it is simultaneously energized with the compressor. The compressor will run until the high sstting for thermostat 2no ~ of for instance 90 F, is sensed and the circulating pump 16 will be shut down. However, the circulating pump 110 and blower 112 will continue to operate and int-oduce heat into the room even though the compressor is not drawing power until the selected room temperature is attained and sensed by thermostat 121. This signi-ficantly increases the COP.
Cooling Mode The room thermostat will switch the revers-ing valve to the cooling cycle when the room air conditioning unit is switched to air condition-ing mode. If the room thermostat 121 calls for cooling,the circulating pump 110 and blower 112 will be energized.
A thermostat and hulb 210 control temperature o ~he transfer fluid in condui~ 109. If the temperature in conduit 27 is above a set point of for example 40 F, the compxessor 94 will be energized and the compressor 94 will run until the 40 F is sensed in conduit 27 and the compressor 94 and airculating pump 16 are de-energized. The blower 112 and pump 110, however, will co~tinue to operate until the temperature of the room as sensed by ~hermostat 121 drops to the control setting of thermostat 121 and de-energizes pump 110 and blower 112.
In the cooling mode, the pump 110 circulates transfer f]uid through the heat exchangers 102 and 104.
Heat is picked up in the building by the transfer fluid and transferred to the Freon and the exchangers ].02 and ].04 and the Freon yoes to the compressor to increase its heat and pressur~. Freon then travels to the source water heat exchangers 62 and 64 where it releases its heat into the source water which is con-veyecl by pwnp 16 to the barn heat exchangers. The Freon flow route i.s illustrated in Fig. 2 by broken arrows for the cooling mode.
In the cooling mode, the heat exchanger 30 can be optionally used, but tests indicate that it is not nec~ssary. A valve 120 in li.ne 19 can be employe~
to prevent circu.lation through the heat ~xchangers 14 in the barn but provide circulation of the transfer fluid throuqh the outside heat exchanger 30 where buildlng heat is released as the blower removes heat from the transfer fluid.
The adva~tages obt.~ined using the divided and para'lel :~!ow .,or the heat exchanyers 60, 62 are a].so obt.~ined wi~h the heat ~cchangers 14. The use of the di~ided ~low m.inimizes the pressure drop through each heat xchan~et.~ 14 and increases the residence time of the ~ransfe.r f.uid i.n the exchanser. A preferred embodiment of the heat exchangers 14 would .include hea~ers hav~.ng an inside diameter of 1-1/2 inches with conduit5 of inside diameter of 1/2 inch. Tne fins each consist of a single apartured plate with conduiis 40 extendillg through the aper~ures. The fins 43 dasirably : hava a heisht o~ lQ inches anc~ wi.dth of at least 1 incn.
Bi~hi, ccnduits 40 .in sach heat e~changer has worked well.
30 :~n ail~ vent 45 and ~he to~ o a heade.r 41 assists in ini.ti.al.ly ~ill.i.ng the heat exohanger wit.h transi-.er fiuid.
The use of water-methano:l. rather than e~h~Lene ~gl~col also requires a pump of less capacity, an~l a smai..Ler Inotor ~ecatlse of the les.se.r ~-iscosity of l:h~
water-methanol mlx.

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Claims (11)

1. The embodiment of the invention in which an exclusive property or privilege 16 claimed are defined as follows:
   l. A system for utilizing heat generated by livestock in an agricultural operation to heat residence, including a first heat exchanger located in the barn, a second exchanger located remote from said barn, in a heat pump unit said residence, a plumbing circuit for circuiting a water-based transfer medium between said first and second heat exchangers in a closed loop, third heat exchange in said heat pump unit, a refrigerant circuit circulating with said second and third heat exchangers and including refrigerant coils in said second and third heat exchangers, and a compressor associated with said refrigeration circuit and a second closed loop plumbing circuit for circulating water between said third heat exchanger and fourth heat exchanger which heats the residence and wherein each of said second and third heat exchangers in said heat pump unit is divided with separate inputs and outputs for the divided units connected in parallel to the respective plumbing circuits.
2. 2. The system of claim 1 in which each of said second and third heat exchangers is divided with separate inputs and outputs connected in parallel to the respective plumb-ing circuits.
3. 3. The improvements of claim 1 which said barn heat exchangers comprise inlet and outlet manifolds con-nected to the first water circulation circuit, and heat exchangers having a plurality of conduits connected in parallel between said manifolds and fins on said conduits.
4. 4. The improvement of claim 3 in which the heat ex-changer conduits are arranged in two angularly related banks, with the fins similarly oriented to afford collec-tion of condensate along a line intermediate the banks and at the juncture of the banks.
5. 5 . The improvement of claim 1 including a heat ex-changer located adjacent said barn for removing heat from the heat transfer fluid in said first circuit when said system is in a building cooling mode.
6. . A heating system including a compressor, an input heat exchanger, an output heat exchanger. first and second transfer fluid-refrigerant heat exchange assemblies each of said assemblies including first and second conduit coil sections with an inner refrigerant line located within the outer transfer fluid conduit, the inputs of said refriger-ant and transfer coil sections being connected in parallel to divide the input flow and reduce the velocity of flow from a first velocity to a second velocity through said conduits and said conduit output being connected in paral-lel to rejoin the divided fluid flow from the first and second coil sections to return the flow to a velocity high-er than said second velocity and a refrigerant plumbing circuit connecting said compressor and said input and out-put exchangers and said first and second heat exchange assemblies .
7. 7. A heating system in accordance with claim 6 where-in said transfer fluid employed in the pluming circuits is a water methanol mix with more than 50% methanol
8. 8. A heating system including a compressor, an input heat exchanger, and output heat exchanger having a blower, first and second transfer fluid-refrigerant heat exchange assemblies and a plumbing circuit connecting said compres-sor and said input and output exchangers and said first and second heat exchange assemblies, said circuit including a circulating pump in said circuit between said output heat exchanger and its associated transfer fluid-refrigerant heat exchange assembly and a return transfer fluid conduit from said output heat exchanger to said transfer fluid-refrigerant assembly, and including a room thermostat and a circuit electrically connecting said thermostat to said circulating pump and said blower, a line thermostat having a sensor in sensing relation to said transfer fluid return conduit and circuit means electrically connecting said line thermostat to said compressor and connected room thermostat so that when said room thermostat enables said line thermo-sat said compressor can be enabled if required to provide the selected room air temperature and said circulating pump continuing to circulate transfer fluid until said room thermostat attains a selected setting.
9. 9. The heating system of clam 8 wherein and trans-for fluid employed in the plumbing circuit between said output heat exchanger and the associated transfer fluid-refrigerant heat exchange assemblies is a water-methanol mix with more than 50% methanol.
10. 10. a system for utilizing a remote source of heat by including a first heat exchanger located in heat exchange relationship with a source of heat, a heat pump unit in-cluding a second heat exchanger located remote form said source, a plumbing circuit for circulating a water-based transfer medium between said first and second heat exchangers, said heat pump unit including a third heat exchanger in close proximity to said second heat exchanger, a refrigerant circuit including relatively short freon lines communicating with said second and third heat ex-changes and including refrigerant coils located within said second and third heat exchangers, and a compressor asssoci-ated with said refrigeration circuit and a second closed loop plumbing circuit for circulating water between said third heat exchangers includes first and second helical conduit coil sections with a refrigerant line located with-in the outer transfer fluid conduit, the inputs of said refrigerant and transfer fluid conduit, the inputs of said refrigerant and transfer coil sections being connected in parallel to divide the input flow and reduce the velocity of flow from a first velocity to a second lower velocity to increase the residence time and the heat transfer relative to the working fluid through said conduits and said conduit outputs being connected in parallel to rejoin the divided fluid flows from the first and second coil sections to return the flow to a velocity higher than said second va-locity and a plumbing circuit connecting said compressor and said input and output of said heat exchangers.
11. 11. The heating system of claim 10 including a room thermostat and a circuit electrically connecting said ther-mostat to said circulating pump and said blower. a line thermostat having a sensor in sensing relation ion to said transfer fluid return conduit and electrically connecting to said compressor and connected to said room thermostat so that when said room thermostat enables said line thermostat said compressor can be enabled if required to provide the selected room air temperature and. said circulating pump continuing to circulate transfer fluid until said room thermostat attains a selected setting