NZ200151A - Solar and convection assisted reversible heat pump system:perforated exterior coil panel - Google Patents

Description

2 001 5 Priority Date(s): Complete Specification Filed: 6^9.' Class: r^a&a®.)poj. )co Publication Date: , ...P.). APR jpm' P.O. Journal, No: •. 2 9 HA,? ; RECEIVED Patents Form No. 5 Patents Act 195 3 COMPLETE SPECIFICATION "SOLAR AND CONVECTION ASSISTED HEAT PUMP SYSTEM" We, Rheem International, Inc. of 59 Maiden Lane, New York, New York, 10038, United States of America, a Corporation organised and existing under the laws of the State of Delaware, hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in an by the following statement:- 2 0 01 5 ' This invention relates to an improved solar and convection assisted heat pump system.

Use of a heat pump for indoor heating and cooling is well known. Heat pump systems are especially useful in the temperature sections of, for example, the United States of America to transfer heat between the outdoors and indoors.

There are many types of heat pump systems. A description of various heat pump systems is set forth in the 1976 ASHRAE Handbook and Product Directory published by the 10 American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc., particularly at pages 11.1 through to 11.4. A bibliography in the ASHRAE Handbook . also references various papers which describe heat pump systems.

One common type of heat pump system utilises air as a heat source and sink and also uses air as the distribution fluid. The thermal cycle or transfer of heat between the outdoor and indoor air is accomplished by means of a gas, herein called refrigerant which is made to flow between an indoor coil and an outdoor coil in a refrigeration cycle. 20 A heat pump system, disclosed in the 1976 ASHRAE Guide and also discussed in a technical article by Sporn and Ambrose entitled "The Heat Pump and Solar Energy" (Association for Applied Solar Energy, Proceedings World Symposium on Applied Solar Energy, November 1955), teaches that the outdoor coil of a heat pump may be a solar panel. Various patents have also taught that a solar panel may be used as an outdoor coil in association with a heating or refrigeration system for a building. For example, Newton, in USA Patent Number 2,3 42,211, teaches such a system. However, the Newton 30 system does not contemplate a combined solar panel and heat 2 001 5 1 pump system.

Other patents and publications of the same general type and nature include the following:- USA Patent No. Inventor Title Issue Date 2,342,211 Newton Utilisation of Natural 22nd Feb. 1944 Heating and Cooling Effects 2,396,338 Newton Radiation Heating and Cooling System 12th Mar.1946 2,689,090 Wethe.rbee, et al Heating System 14th Sept.1954 2,713,252 Jackson, Temperature Control 19th July,1955 et al System 3,194,303 Haried Heat Pump System 13th July,1965 3,960,322 Ruff, Solar Heat Pump 1st June,1976 et al 3,991,938 Ramey Combination Heat Pump 16th Nov.1976 and Low Temperature Solar Heat Absorber 20 3,996,759 Meckler Environment Assisted 14th Dec.1976 Hydronic Heat Pump System 4,007,776 Alkasab Heating and Cooling 15th Feb.1977 System Utilising Solar Energy 4,012,920 Kirschbaum Heating and Cooling 22nd March,1977 System with Heat Pump and Storage 4,030,312 Wallin Heat Pumps with Solar 21st June,1977 et al 2 001 5 1 4th Oct. 19 77 3rd Jan.1978 1st Aug.1978 5th Sept.1978 18th Sept.1979 18th Dec. 1979 4,052,001 Vogt Heating System 4,066,118 Goettl Air. Conditioning System 4,103,49 3 Schoenfelder Solar Power System 4,111,259 Lebduska Energy Conservation System 4,16 7,965 Rogers Integral Water- Refrigerant- Air Heat Exchange System 4,178,989 Takeshita, Solar Heating and et al Cooling System Article entitled "Solar Energy Supplemented Rural-Home Heat Pump" by George R. Mowray, Solar Energy, Vol. 8, No. 1, 1964, pages 12 to 16.

Article entitled "Performance of a Solar Heated Office Building", by F.H. Bridgers, et al, Transactions American Society of Heating and Air-Conditioning Engineers, pages 83 to 110.

There are additional patents and publications which teach the use of solar panels or solar absorption for heating and cooling building structures. Typical among these are the following Title Issue Date USA Patent No. Inventor 3,935,897 2,030,350 2,221,971 Pulver 3rd Feb.1976 3,952,947 Method of Solar Heating and Cooling Solar Operated Refrig- 11th Feb.1936 erating System Solar-Absorption Cooling System for Building Structures 19th Nov.19 40 Saunders Heating & Ventilation System 27th Ap.1976 Bremser Haywood 200151 "The Hammer" - December, 1979, Page 3.

While the referenced prior art teaches that solar collection coils may be used both for heating and cooling purposes in a building, none of the patents or known prior art appears to teach the combination of a solar assisted heat pump coil which relies simultaneously upon moisture evaporation or condensation on a coil, prevailing air flow in a geographical region over a coil, solar energy absorption by a coil, namely, radiation transfer, natural convection flow over a coil and the normal energy transfer mechanism associated with the cycles of a heat pump. The present invention constitutes what is believed to be an improved combination of all of these particular features and provides for significantly improved efficiency of heat pump operation, lower energy consumption and improved economies for a home heating and cooling system.

Thus, it is an object of the present invention to provide an improved solar and convection .assisted reversible heat pump system.

A further object of the present invention is to provide a heat pump system which has enhanced energy transfer characteristics.

A further object of the present invention is to provide a heat pump system having an outside coil which is mounted for co-operative heat transfer due to prevailing air flow conditions, natural convective air flow, and radiant heat exchange.

Yet a further object of the present invention is to provide an improved reversible heat pump system which is easy to maintain, has a reasonable cost, and which is more fuel 2 001 5 efficient than prior art systems.

According to the invention there is provided an improved solar and convection assisted heating and cooling reversible heat pump system for a building, the system comprising, in combination a coil outside the building for energy transfer and a coil inside the building for energy transfer; the surface area of the outside coil being oversized relative to the surface area of the inside coil in a ratio of at least 30 to 1, the outside coil comprising a black body tube forming an outside panel; mounting means for the outside panel, the mounting means including a mounting bracket for maintaining the panel oriented substantially transverse to prevailing air flow, and simultaneously substantially transverse to the prevailing incidence of radiant solar energy.

These and other objects, advantages and features of the present invention will be set forth in the following detailed description with reference to the accompanying drawings in which:- Figure 1 is a schematic circuit diagram of a conventional heat pump in the cooling cycle; Figure 2 is a schematic circuit diagram of a conventional heat pump in the high temperature heating rycle; Figure 3 is a schematic diagram of a conventional heat pump in the low temperature heating cycle; Figure 4 is a schematic diagram of the improved solar assisted heat pump of the invention in the cooling cycle; Figure 5 is a schematic diagram of the improved solar heat pump of the invention in the high temperature heating 200151 cycle; Figure 6 is a schematic diagram of the improved solar assisted heat pump of the invention in the low temperature heating cycle, and Figure 7 is a schematic diagram of the oversized outdoor coil associated with the improved solar assisted heat pump of the present invention as oriented with respect to prevailing air flow, sun direction and natural convection air flow.

Figures 1 to 3 represent schematically a conventional, 10.55 kW rating heat pump system which can provide for both cooling and heating for a building. An indoor coil 10 connects via line 12 with pump mechanism 14. The refrigerant is cycled or pumped by the pump mechanism 14 through the system. Mechanism 14 includes a compressor, various valves and controls (not shown) known to those skilled in the art. The opposite side of the pump 14 is connected by a line 16 to an outdoor coil 18. A second line 20 interconnects the coils 10 and 18. An indoor fan 22 causes air to flow over the indoor coil 10 in order to effect heat transfer. Likewise a fan 24 associated with the outdoor coil 18 drives air over that coil 18 in order to effect appropriate heat transfer.

Figure 1 represents the configuration of a conventional .55 kW rating heat pump when in the cooling mode. The 2 indoor coil 10 which typically will have a 0.3534m area receives relatively high pressure refrigerant which expands in the indoor coil 10 in the known manner to cause cooling by that coil 10. The refrigerant is subsequently transferred via line 12, pump 14 and line 16 to the outdoor coil 18 where the now pressurised refrigerant has energy removed. 200151 Typically the outdoor coil 18 will have an area of 1.395 sq.metres or approximately four times the surface area associated with the indoor coil. In the example shown in Figure 1, the various settings associated with the energy transfer are set forth in the first left hand column in the following Table 1.

Table 1 is to be read in conjunction with the following:- * With full sunshine, the data in parenthesis is observed.

** The panel is aligned 70 deg from the horizontal and in a south/southwest heading (in Northern Hemisphere).

*** With 8 km/h. wind, the data in parenthesis is observed.

E.E.R. Energy Efficiency Rating C.O.P. Coefficient of Performance Note that Table 1 compares the described known system and 20 the system proposed in this invention in equal ambient conditions except as indicated by values in parenthesis. The tabulated values would be subject to several factors varying continually with time of day and season, such as wind velocity and direction, intensity of solar radiation as well as moisture precipitation whether as rain or dew. The scope of Table 1 (values in parenthesis excepted) is limited to a comparison at times when such factors are either equal in both cases or inapplicable in the comparison.

Figure 2 illustrates the conversi* " 8 1 3 JAN 1986 J 200151 standard heat pump system of Figure 1 into a heating system where the outdoor temperature is considered to be somewhat moderate; namely 8.3 deg C dry bulb temperature, 6 deg C wet bulb temperature. The energy requirements and other significant data associated with this typical arrangement are set forth in the second left hand column of Table 1 as well as in Figure 2. Note with this arrangement that the heat transfer efficiency at the indoor coil is equal to 4.2 to 4.6 Coefficient of Performance.

Figure 3 represents the situation when the outdoor temperature is significantly lower; namely -8.3 deg C dry bulb, -9.4 deg C wet bulb. In Table 1, the relevant data is set forth with respect to the arrangmenet of Figure 3 in the third left hand column.

So far the description has related to a conventional, 10.55 kW rating heat pump configuration of the type known to TABLE 1 Conventional 10^.55 kW Rating i 0 1 Indoor Ambient ( C) Heating Heating Cooling (High Temp.) (Low Temp.) 26.7 D.B. 19.4 W.B.

Outdoor Ambient ( C) 35 Indoor Refrigerant Temperature (°C) 5 Indoor Refrigerant Pressure (kPa) Outdoor Refrigerant Temperature ( C) Outdoor Refrigerant Pressure (kPa) 479 53.3 1992 Compressor Power (W) 3974 Indoor Pan Power (W) 454 Outdoor Fan Power (W) 380 Cooling (Heating) Output (kW) Energy Required (W) Efficiency Rating (E.E.R. or C.O.P.) Indoor Coil Size (m2) .48 4808 7.41E.E.R. 0.3534 21 8.3 D.B. 6.1 W.B. 50.6 1861 -3 348 3377 454 380 115 8 4211 21 -8.3 D.B. -9.4 W.B. 36.8 1310 -16 186 2437 454 380 6,55 3271 2.74 C.O.P. 2.13 C.O.P. 0.3534 1.395 0.3534 1.395 Outdoor Coil Size(irr) 1.395 Not applic. Not.applic. Not applic.

Outdoor Coil Orientation Solar (Radiation) and Wind (Convection) Assisted 10„ 53cW Rating Heat Pump Heating Heating Cooling (High Temp.) (Low Temp.) 26.7D.B. 21 21 19.4W.B. 8.3 D.B. 6.1,W.B. -8.3 D. -9.4 W.

B B • • -J • 00 43.3 32.2 545 1551 1165 40.6(37?8) 5.6(8.3)* -8.9 (- ■8 .3) 1448 493 1545) 269 2953 2408 1990 320 320 320 .59 1L77 7.65 3272 2728 2310 K) 11.0 E.E.R. 4.20C.O.P. (12.0)*** (4.6)* 3.30 C. (3.61* .0 0.651 0.651 0.651 O .71 .71 .71 70°** 70°** 70°** Ln those skilled in the art. Figures 4 to 7 and in particular Figures 4 to 6 represent in schematic diagrams the improved solar assisted heat pump of the present invention as arranged in a cooling, high temperature heating and low temperature heating configuration respectively.

Referring first to Figure 4, an indoor coil 30 is maintained in substantially the same configuration as with the conventional system. The indoor coil 30 is connected through a line 32 with the pump 34. The pump 34 also connects by line 36 with outdoor coil 38. An interconnecting line 40 connects indoor coil 30 with outdoor coil 38. An indoor blower 42 blows air over the indoor coil 30. Note, however, that a fan or blower is not required for the outdoor coil 38.

Additionally, the outdoor coil 38 has a significantly increased surface area relative to the indoor coil 30. In practice, the surface area of the outdoor coil 38 is at least thirty times greater than that of the indoor coil 39 and preferably is in the range of fifty to sixty times greater than that of the indoor coil 30.

Figures 5 and 6 represent the configuration of the improved heat pump of the present invention in the high temperature and low temperature modes respectively which are analogous to the modes of the heat pump shown in Figures 2 and 3. The right hand columns of Table 1 also set forth the significant data with respect to a 1D,.S5 kW rating heat pump configured in accordance with the schematic diagrams set forth in Figures 4, 5 and 6. For purposes of comparison, Table 1 also includes the energy outputs associated with a typical 10,. 55 kW rating conventional heat 2 001 5 pump as shown in Figures 1, 2 and 3 as well as the arrangement of Figures 4, 5 and 6. This comparative data illustrates the improvement in the efficiency of heating or cooling of the heat pump of the present invention.

As stated before, no fan is needed for the outdoor coil of the heat pump of Figures 4 to 6. Also, in testing the device shown in Figures 4 to 6 and particularly at the low temperature configuration of Figure 6, it has been found that defrosting of the coils in extreme weather conditions is not necessary.

Figure 7 illustrates an important feature of the present invention; namely, the orientation and arrangement of the outdoor coil 38. The outdoor coil 38 is formed from a wound tube 44 which has a plurality of fin members (not shown) preferably made from aluminium affixed thereto. The tube 44 is retained on a bracket 48 and thus forms a large panel through which air may flow and upon which light may radiate. An inlet 36 and outlet 40 from the coil 38 connect with the remainder of the heat pump system.

In operation, the bracket 48 is supported appropriately above ground level or above grade level by means of a support member, for example, support member 50 which is schematically illustrated. The orientation of the panel 38 is quite important to the practice of the invention. Thus, depending upon the geographical location of the panel 3 8 on the earth, the orientation is determined in accordance with a number of factors. First, the orientation must take into account the impingement of the rays of the sun represented by the lines 52. An object of the invention is to maximise the radiant energy 2 0 01 5 transfer from the rays of the sun. To maximise radiant energy transfer, the panel should approach a horizontal position adjusted for latitude. Thus, if the panel 38 is located for example, in the midwest portion of the United States of America, the panel 38 should be adjusted at a slight incline toward the south in order to accommodate the path of the sun. Such solar energy design data is published by Reynolds Metals Company, Product Development Division, USA, and teaches that at a latitude of about 45° north, the panel should be tilted in the range of 20° to 40° from the horizontal toward the south to maximise radiant energy transfer. However, significant energy transfer can be effected at angles up to 75° from the horizontal. In the winter heating season, at the same 75° angle radiant energy will be minimised during the summer cooling season when heat is being rejected from the panel.

Second, the panel 38 must be oriented in order to intercept the prevailing wind or air flow in the region involved. Again, in the midwest of the United States of America for example, this is generally a west to east air flow. Thus, to satisfy this requirement, it is desired to stand the panel 38 substantially vertical and transverse to the east/west direction.

Third, it is desirable to maximise the effect of natural convection flow in the immediate region of the panel 38. Typically, natural convection causes hot air to rise and flow through and over the fins (not shown) and tube 44. Thus, for natural convection flow, the most preferred orientation of panel 3 8 is in the horizontal plane. This will accentuate heat transfer due to natural ^ U01 5 1 convection in the immediate area of the panel 38.

Fourth, the effect of moisture evaporation and condensation must be accentuated. Mounting the panel toward I the horizontal inclination is desired with respect to this consideration.

In an effort to maximise these four types of heat transfer in addition to the radiant transfer due to the placing of the panel 38 in the atmosphere, both sides of the panel are free and the panel is oriented, for example, in the midewest of the United States of America in a south/ southwest inclination of approximately 50-70° with the horizontal. It is possible to calculate the maximum efficient exposure angle utilising solar elevation tables and weather information. Alternatively, the panel 38 may be positioned by empirical or experimental means to maximise its effect. Preferably the fins (not shown) and tube 44 are coated to act as a black body. In order to improve efficiency, the effect of the energy associated with the sun upon the desired operation of the panel 38 can be diminished by shading, for example, and convection and radiation heat transfer phenomena will become more predominant.

In review, the system of the invention comprises a heat pump in which the outdoor coil is a relatively low cost, thin tube or plate coil. This coil is incorporated as the air heat source or heat rejection (outdoor coil) of the heat pump and serves as an energy collector or rejector by virtue of various physical phenomena including radiation, convection and conduction. Conduction takes place to the extent that moisture collects or is dissipated 200151 from the coil thereby utilising or acquiring the energy of condensation, evaporisation or change of state of water. The outdoor air heat source or heat rejection coil thus uses natural convection as opposed to a forced convection outdoor coil. This means the coil face area is relatively large and can therefore serve also as a solar collector. It also acquires the capability of collecting or rejecting large amounts of moisture. Preferably the outdoor coil is coated with material designed to absorb solar energy. It is also located and oriented to maximise solar energy or radiation transfer particularly in the winter months to permit good natural convection, to take advantage of natural wind currents and for exposure to natural precipitation. The coil location may be on a roof or on ground level. It can be mounted to a vertical wall of a structure or it can even take the form of a fence.

When the heat pump is in the heating mode of operation, refrigerant is evaporated in the outdoor coil and heat is absorbed in the refrigerant. The referigerant circulating through this coil may change temperature under the effect of several potential heat transfer mechanisms. In the heating mode the coil may gain or lose heat by radiation. Other heat gain or loss may occur by convection. In the latter case the effects of wind velocity and direction and the presence of moisture on the coil surface would be capable of playing significant roles. In the event of substantial solar radiation impinging on the coil, the temperature of the refrigerant in the outdoor coil may conceivably - 15 200151 exceed the temperature of the surrounding ambient air, this degree of heat gain providing a useful and significant improvement to the coefficient of performance of the system when in heating mode.

Note that a fan and fan motor is not required on the outdoor coil. performance and efficiency is expected over and above forced convection outdoor coils because defrost cycles as required on such prior' art coils is reduced or eliminated. Ice build-up on the outdoor coil is thus reduced because of the relatively large coil base area, wide fin spacings, small temperature difference between the coil and the air, and also solar heating. In the event of the ice build-up, natural convection will still occur over the iced coil surface to maintain system performance. A separate system for solar or radiation collection is not needed as in various prior art systems. for space heating or it may be used for heating water or placed iri' some type of storage facility for future use. In this manner the system may be used as an off peak system for collecting energy. Also, domestic hot water may be obtained from the heat pump when the heat pump is either in the space heating or space cooling modes of operation. This again is another manner in which to improve system performance.

When the heat pump is in the cooling mode, refrigerant is condensed in the outdoor coil and heat is given up by the refrigerant to the coil surface. Thte-^ This is an energy saving. Further improved The energy or heat collected is used directly 16 | I J> .1AMIQ8A ,OI ZUU1D1 coil then becomes warmer than ambient air temperature.

Heat is transferred to the air and the change in air density will promote natural convection air flow through and over the coil. Natural wind currents that occur will help move the air through the coil and improve heat transfer. During periods of precipitation, the coil performance and total system efficiency will be improved due to evaporation of moisture on the coil surface.

Since the coil temperature is above collection temperature, the effect of solar energy is diminished.

Most rejection can be improved by a shade positioned over the coil. Performance will improve during the evening and night when heat is radiated more easily. Again, there is no forced convection with respect to the outdoor coil. Thus, energy savings are realised with respect to the elimination of an outdoor fan.

While in the foregoing a preferred embodiment of the invention has been set forth, the invention is limited only by the following claims.

Claims (4)

200153 What we claim is:

1. A solar and convection assisted heating and cooling reversible heat pump system for a building, the system comprising, in combination:- a coil outside the building for energy transfer and a coil inside the building for energy transfer; the surface area of the outside coil being oversized relative to the surface area of the inside coil in a ratio of at least 30 to 1, the outside coil comprising a black body tube forming an outside panel;and mounting means for the outside panel for maintaining the panel, when installed for use oriented (a) distant from other structures so that both sides of the panel are within, and somewhat transverse to, an unobstructed path of prevailing region air flow, (b) with both sides of the panel open to air flow through the panel, (c) with one side of the panel oriented for solar incidence, and (d) in position to miximise heat transfer due to the simultaneous effects of (A) prevailing region air flow through the panel, (B) natural convection air flow around and through the panel, (G) moisture evaporation and condensation, and (D) radiant energy incidence on the panel wherein the panel position is a combination of a direction transverse to the prevailing region air flow, a horizontal position for maximum natural convectio^^^&cl A? JL. h ^ - is - -I 134AM 200151 evaporation and condensation energy transfer, and a direction transverse to the incidence of solar energy.

2. The system of claim 1 wherein the surface area ratio is in the range of 50:1 to 60:1.

3. The system of claim 1 or 2 where the panel mounting means includes a mounting bracket surrounding the periphery of the outside coil to prevent obstruction of the path of prevailing region air flow through the outside coil.

4. A solar and convection assisted heating and cooling reversible heat pump system substantially as hereinbefore described with reference to Figures 5, 6 and 7 of the accompanying drawings. DATED this 8th day of January, 1986 RHEEM INTERNATIONAL INC. by RHEEM AUSTRALIA LIMITED