Heat extraction or reclamation apparatus for refrigerating and air conditioning systems

MINISTRY OF INDUSTRY AND ENERGY 2D0CI

Industrial Property Registry

The Registry of aettfeíde has been granted with the data appearing in the ®F®-eente description and eogün the contents of the attached Report.

<img file="ES463581A1_D0001.tif" />

© ES § ©

NUMBER

463.581

DATE OF PRESENTATION

27.10.77

PATENT OF INVENTION

Θ Al

<td>(30) PRIORITIES: (countless</td><td>(£2) DATE</td><td>(33) COUNTRY</td>

<td> 736.004</td><td> 27.10.76</td><td>USA</td>

<td>ADVERTISING DATE</td><td>(^INTERNATIONAL CLASSIFICATION FZV7</td><td>(£2} PATENT OF WHICH IT IS DIVISIONARY</td>

@ TITLE OF THE INVENTION

A HEAT RECOVERY DEVICE FOR CONNECTION TO CONVENTIONAL REFRIGERATION OR AIR CONDITIONING EQUIPMENT

<td>(Ti) APPLICANT IS)</td><td> •</td>

<td>SUN-ECON, INC.</td><td>(P-635) ·'*&lt;/ • · ·</td>

<td>APPLICANT'S ADDRESS</td><td></td>

<td>Northway 10, Ushers Road, Ballston Lake, United States of America</td><td>New York 12019, •Es'fra- • · ·</td>

<td>^2) INVENTOR «YES</td><td> * ·«·</td>

<td>Kjartan A. Jonsson</td><td></td>

<td colspan="2">θ HOLDER(S)</td>

<td>θ REPRESENTATIVE Mr. Fernando of Elzaburu Marquez</td><td>(P.- 67.092)</td>

UNE A·4

MOD. 310«

USE AS FIRST PAGE OF THE REPORT

IFG lloja ηίπη. 2

The present invention relates to an apparatus particularly adapted for recovering otherwise wasted heat from refrigerant gas flowing through air conditioning and refrigeration equipment. The apparatus includes a countercurrent heat exchanger for transferring heat to a medium such as water, the heat exchanger being installed in the line between the compressor and the conventional condenser. A pump circulates water through one side of the heat exchanger. The hot refrigerant gas from the compressor is circulated through the other side of the heat exchanger. The various parameters of the heat exchanger are chosen so as to remove superheat from the refrigerant and also partially condense the refrigerant to such an extent that the refrigerant/ after emerging from the aforementioned heat exchanger, will be partially sub-cooled/ but generally not to a level where the quality of the refrigerant will be less than about 0/25.

The apparatus according to the present invention is readily adaptable for use as part of new air conditioning and refrigeration equipment or as an addition to existing equipment of various capacities without detrimentally affecting its performance and reliability in other respects. Furthermore, they will not only permit efficient use

-3sent of the excess heat recovered from the refrigerant gas, but will also make the air conditioning and refrigeration equipment run more efficiently on its own.

It is known in the prior art to provide an inter; heat exchanger that transfers heat from the refrigerant to a fluid transfer medium such as water. One approach is illustrated in U.S. Patent No. 3,922,876. That patent illustrates that refrigerant gas is passed through one side of a heat exchanger located upstream of the condenser to reject heat to water intermittently flowing through the other side of the heat exchanger. To control condensation in the heat exchanger, the patented device includes a temperature-sensitive valve that stops the flow of water when the inlet water temperature drops to the temperature at which an unacceptable portion of the refrigerant gas condenses. Thus, when connected to hot water heating equipment, the patented device will not operate for inlet water temperatures below approximately the 37.7 to 60°C range - at which most commercially available refrigerants completely condense. Because of this, however, until the inlet water temperature is sufficiently high, the conventional hot water heater must reheat the water. This results in rather long recovery times and very little savings from heat recovery, particularly during periods of high demand. Furthermore, most of the heat contained in the refrigerant gas is lost while waiting for the inlet water temperature to rise, leading to reduced efficiency.

Various other prior art equipment has included some form of supplemental heat exchanger for transferring heat from the refrigerant to a hot water device. U.S. Patent Nos. 2,516,093, 2,751,761, 3,188,829, 3,301,002, 3,308,877, 3,366,166, 3,563. 304, 3.916.638 and 3,926,008 present typical prior art cooling approaches including means for heating water by absorbing heat from the refrigerant with the use of a supplemental heat exchanger at a location upstream of the conventional condenser. In these cases, however, the teachings of the patents to those skilled in the art are quite clear that the supplemental heat exchanger, or pre-cooler for the refrigerant gas as it is sometimes called, must be placed in a large volume of water relative to the volume of refrigerant flowing through the heat exchanger at any given time. Because of this, at least until the water has been substantially heated beyond the !

usual temperature range for public service water

PItojn ηήιη.

from 1/6 to 12/7°C, the refrigerant would be expected to completely condense to a saturated liquid in the pre-cooler heat exchanger, leaving the conventional condenser with the task of subcooling the liquid refrigerant and the compressor with the increased work of circulating the liquid through the bulk of the equipment.

In equipment where compression rates; piping lengths; the relative height of the compressor and condenser; the presence of low points; flow-rate-reducing elements such as elbows and bends in the refrigerant piping; equipment insulation; The number of valves and related factors can be adjusted in the equipment installation procedure. The presence of such large quantities of liquid refrigerant upstream of the conventional condenser may be acceptable. However, when it is desired to modify an existing installation to include a supplementary heat exchanger for heating water, the equipment parameters are not easily or economically changed in most cases.

Since it is desirable to modify existing equipment as little as possible when providing a supplementary heat exchanger for hot water, the quantity of liquid coolant at the discharge of the supplementary exchanger is of considerable importance. Excess liquid may lead to the collection of pools of coolant mixtures.

29088

-6te liquid and lubricating oil generally carried with the refrigerant gas at low points in the piping of the refrigeration equipment leading to the conventional condenser, or even in the supplementary heat exchanger itself. If these puddles form clogs that block the refrigeration equipment's piping, the upstream piping becomes overpressured as the compressor continues to pump more gas; and the downstream piping becomes starved as the compressor continues to pump, draining the refrigerant. The cooling capacity of the equipment deteriorates until the pool or plug of liquid begins to move rapidly through the equipment under the influence of the higher upstream pressure. This movement continues at rifle-shot speed until another low point is reached, after which the process repeats. Should a plug be driven into the compressor or other vital component, serious damage can result. It has been known for such plugs to break the pipe. Otherwise, the plugs or other liquid entering the conventional condenser can first flood its inlet plenum and then the condenser itself, resulting in poor performance. Thus, following such teachings of the prior art regarding refrigeration and air conditioning equipment, supplementary heat exchangers for heating a medium such as water would not lead to satisfactory results when changing a

I f

-7existing equipment.

The present invention provides a supplemental hot water heat exchanger for installation in air conditioning equipment and refrigerators at a location between the conventional compressor and the conventional condenser. To prevent the formation of flow blockages, condenser flooding, and similar detrimental effects, the heat removal capacity of the heat exchanger is limited so that the quality of the refrigerant gas passing through the heat exchanger is reduced.¹ leaving the heat exchanger will be within specified limits. By ensuring that a specified amount of refrigerant gas vapor is flowing into the equipment even when fairly large amounts of liquid refrigerant condensate are present, the invention ensures that existing equipment can be modified by adding a heat exchanger to heat water without reducing the cooling or air conditioning capacity of the equipment. As will be discussed later, the addition of a heat exchanger for heating water in accordance with the present invention significantly improves the overall efficiency of the basic air conditioning or refrigeration equipment.

Figure I is a block diagram of a conventional refrigeration or air conditioning equipment of the prior art;

Figure 2 is a temperature-entropy diagram: qualitatively comparing prior art equipment

-8with one in accordance with the present invention;

Figure 3 is a block diagram of a refrigeration or air conditioning equipment embodying the present invention;

Figure 4 is an elevation view of a heat extraction equipment according to the invention, the front cover panel having been removed to allow observation of the components of the invention;

Figure 5 is a view taken along line 5~5 from Figure 4;

Figure OA is a schematic representation of the preferred type of heat exchanger coil for use in the present invention including arrows to illustrate the movement of gas and liquids through the device;

Figure 6B is a sectional view taken along line 6-6 of Figure 6A;

Figure 7 is a schematic diagram of a device!

i for heating hot water which is an embodiment of two heat extraction equipment according to the present invention, including arrangement for local heaters using the hot water produced; ¡ i I Figure 8 is a table illustrating data for:

typical performances for an embodiment of the invention;

• !

ί t

Yo¹

Yo

-9!Figure 9A illustrates a plot indicating the time required to raise a given quantity of water by 55.5°C with the application of the invention;

Figure 9B illustrates a plot indicating the temperature increase of a given quantity of water in one hour with the application of the invention;

Figure 10 illustrates a plot indicating the percentage reduction in compressor power as a function of inlet water temperature; and

Figure II illustrates a plot indicating heat recovery as a function of inlet water temperature.

A detailed description of various embodiments of the invention is given below, with reference to the drawings in which like reference numerals identify the structural elements of the various figures.

Figure 1 illustrates a schematic block diagram of a conventional prior art refrigeration or air conditioning unit. Saturated or slightly superheated low pressure refrigerant is drawn into a compressor at point 1 and discharged as a high temperature, high pressure superheated vapor at point 2. From point 2, the refrigerant gas flows through a conventional condenser where it is condensed to a liquid.

-10saturated or sometimes slightly subcooled, which then typically passes to an intermediate vessel, although intermediate vessels are not included in all equipment. At point 3 on the downstream side of the intermediate vessel, the liquid refrigerant passes through an expansion valve; and from point 4, it passes through an evaporator in which heat is absorbed from the location or body to be cooled.

Figure 2 illustrates qualitatively and graphically, using a conventional temperature-entropy diagram, the performance of the prior art equipment. Thus, at point 1, the refrigerant is a slightly superheated, low-pressure gas. At point 2, the refrigerant is a superheated, high-pressure, high-temperature gas. As the refrigerant gas passes through the condenser, superheat and heat of condensation are removed, taking the refrigerant first through the saturated vapor stage and finally to a saturated liquid state at point 3. From there, the expansion device provides a non-reversible expansion to point 4, after which the refrigerant is evaporated at essentially constant temperature and pressure in the evaporator and flows as a low-temperature saturated gas to the compressor inlet.

Figure 3 illustrates a schematic block diagram.¹co of similar refrigeration or air conditioning equipment ¡ f

to that illustrated in Figure I; however, in this case, the equipment includes a supplementary heat exchanger according to the present invention located between the compressor outlet and the conventional condenser inlet. The various points in the equipment are identified by reference numerals corresponding to those in Figure I but enclosed in boxes. Referring again to Figure 2, the improved performance of an equipment which is an embodiment of the present invention can be seen in the dashed lines. From point 2, the refrigerant is partially condensed in the supplementary heat exchanger according to the present invention until it reaches point 3. The conventional condenser then takes over, completing the condensation of the refrigerant to a saturated liquid and, in many cases, further subcooling the liquid to point 3. The expansion valve then allows the refrigerant liquid to expand to point 4 at a significantly lower pressure and temperature than that obtained in conventional equipment. Thus, when the refrigerant has passed through the evaporator, it reaches the inlet I of the compressor as saturated vapor instead of a superheated vapor as in the case of figure I. Because the vapor is saturated or so

I only slightly overheated in the equipment that are embodiments of the present invention, its volume per unit mass is considerably lower and its temperature

Yo

Yo

Yo

-12 is lower. The lower temperature and volume mean that the compressor must make fewer strokes to move a given mass of gas. The lower temperature also means that the compressor operates at a lower temperature, assuming a conventional hermetic compressor is used in which the refrigerant cools the compressor. The net result of these effects is that the compressor operates more efficiently, as will be discussed later with reference to Fig. ra 10,

Figures 4 and 5 illustrate front and side elevational views of a hot water heat exchanger according to the invention. A sheet metal casing 10 encloses a coaxial countercurrent heat exchanger 12 located within a compartment 14 defined by a central wall 16. Compartment 14 is insulated on all interior surfaces by layers of insulating material such as a 1/2 inch (1.27 cm) matte surface fiberglass pad material, 1500 gram density, available from Johns-Manville Company. Heat exchanger 12 is preferably a tube-within-a-tube cylindrical coil. A coil clamp 20 secures heat exchanger 12 within compartment 14.

There are inlet/outlet projections 22 and 24 attached to the ends of the heat exchanger 12 and extend beneath the central web 16 into a pump compartment 26. At the junction 28, the refrigerant gas flows through the projection 22 and into the heat exchanger portion 12. At the other end, the hotter refrigerant flows out through the projection 24 and into the casing 10. union adapter 28 connected, as will be described subsequently, to the pipe leading from the discharge side of an air conditioning or refrigeration compressor. From there, pipe 30, from the heat exchanger shell, flows to pipe 32 and through a union adapter 34 connected to the pipe leading to the conventional condenser of an air conditioning or refrigeration equipment.

The water for cooling the refrigerant gas flows into the box 10 through the pipe 36 connected to a hot water tank or other hot water device, which will be examined later. A plastic bushing 38 retains the pipe 36 where it passes through the wall of the box 10. A temperature sensing switch 40 is connected to the conduit 36. The switch 40 is set to open or close the power circuit at a temperature of about 82°C or other water temperature appropriate to that required for a particular application. The temperature is chosen so as to prevent excessively high temperature in the hot water using device, such as a hot water storage tank, and to provide a safety margin. When the heat exchange medium is water, a set point of 82°C is preferred. Pipe 36 is connected by a fitting 42 to the suction port of a pump 44 having a magnetic coupling so that the heat exchange medium is not contaminated by the pump. Pump 44 is driven by an electric motor 46, as shown in Figure 5, which operates only when the compressor is operating and switch 40 is closed. The discharge of pump 44, which is typically within a range

from 4.5 to 11.3 liters per minute, depending on expected pressure drops in the equipment, is connected by a fitting 48 and short pipe 5θ to the boss 24. The water thus flows through the boss 24, the central pipe portion of the heat exchanger 12, the boss 22 and into the pipe 52 which passes out of the box 10 through a bushing 54 and is connected to a hot water tank use device or other point of use.

In practice, the box 10 is closed by a metal cover, not illustrated in Figures 4 and 5. The cover closing compartment portion 14 is insulated as previously described to minimize heat losses from the compartment 14. Due to the insulation layers 18, the temperature in the pump compartment 26 is kept well below that of the compartment 14. This is necessary to prevent the temperature detection switch 40 from opening due to the effect of a high ambient temperature in the pump compartment 26, which could result in premature stoppage of the water flow and consequent waste of heat contained in the re-gas;

coolant. Furthermore, the pump motor 46 is protected from operation in an uncomfortably hot environment, To further ensure that an appropriate temperature is maintained in the pump compartment 26, vent plugs 55/56 and 58 are provided to allow the flow of air.

vetive through the compartment and thus assist in maintaining the temperature at a convenient level.

Figure 6A schematically illustrates a fragmentary view of the hot refrigerant gas inlet/hot water outlet of a heat exchanger 12 of the type preferred for the invention. The boss 22 is sealed to an outer steel cylindrical shell 60 through which the refrigerant gas flows; and an inner soft copper tube 62 through which water or other heat exchange medium flows, preferably in a countercurrent direction. The wall of tube 62 has spiral convolutions as also indicated in Figure 6B to induce a type of oppositely rotating motion of the hot coolant and the cooler water, whereby the heat transfer area is improved and a desirable turbulent flow is provided in tube 62. Heat exchangers can also be used with other forms

Yo

-Interior geometric shapes without departing from the scope of the present invention»

The relative sizes of the components of the heat exchanger 12 are determined in accordance with the teachings of the present invention. Since the entire heat exchanger device enclosed within the housing 10 is particularly well adapted for addition to existing air conditioning and refrigeration equipment already having a refrigerant gas condenser and buffer tank intended to serve the needs of waste heat and heat storage, liquid refrigerant of the equipment, it is vital for optimal efficiency of the operation and breeding that the addition of the heat exchanger to extract heat that would otherwise be wasted, does not reduce the air conditioning or cooling capacity of the equipment. The conventional condenser in air conditioning and refrigeration equipment of the prior art is designed for a flow at a relatively high velocity; Thus, the formation of condensate puddles or plugs that could block the flow of gaseous refrigerant is minimized since the small droplets of condensate are quickly carried to the buffer tank of the equipment located immediately downstream of the condenser when the buffer tank is used. Compressor flow capacities in such equipment are reasonably well matched with the expected flow resistance of the condensate. the expansion device and the evaporator, so the addition of substantial flow resistance in the equipment is very inconvenient. For example, the presence of plugs of condensed refrigerant in the piping leading to the condenser would impose an additional load on the compressor since the heavier liquid would be more difficult to move through the equipment. The plugs would also be detrimental to the integrity and reliability of the equipment. If such plugs were to collect in low locations upstream of the condenser, a complete blockage of flow could result during the time that the compressor builds pressure upstream of the plug. Downstream of such a plug, the condenser and evaporator would be overpumped with a consequent loss of cooling capacity. Finally, a situation may arise where the dowel is rapidly propelled through the equipment, which could result in serious damage.

Since the refrigerant gas temperature is at its maximum between the compressor and the condenser in an existing unit, it is desirable to remove excess heat { at this location. For a refrigerant flowing at a mass flow rate of M., the quantity of heat Q. available for recovery can be defined by the following relationship:

Q = M /“h^! - h^and + (lX)h® _/ ,

I 19 9 f 9 .-18where hg^is the enthalpy of the refrigerant gas entering the enclosed flow volume defined between case 60 and tube 62; Y is the enthalpy of the refrigerant gas exiting this flow volume; X is the quality, or ratio of mass of vapor to mass of liquid plus mass of vapor, of the refrigerant exiting this flow volume; y is the difference in enthalpy between saturated liquid and saturated vapor exiting this flow volume. Applicant has determined that when X is in the range of 0.25 to 1.0, at the exit of the heat exchanger coolant flow volume, the gas remaining in the system will have sufficient velocity to move the liquid coolant and the small oil droplets through the equipment without the apparent formation of the previously mentioned inconvenient plugs. During start-up transitions when the inlet water temperature is very low, X may be as low as 0.04 without serious side effects; however, continuous operation under these conditions is not considered desirable. Another way of looking at this aspect of the invention is to consider the flow area that remains for the gas when small liquid droplets or small puddles begin to form in the cooling line. The applicant has found that as long as the flow area is approximately 1/4 to 1/3 of the total area, adequate gas flow would be obtained to prevent or greatly minimize any plugging.

Γ·

Hojn ΗίΊπι.

The amount of heat that can be recovered from the refrigerant and still not have the refrigerant quality drop less than 0.25 at the exchanger outlet!

Heat is determined by the heat absorption capacity of ca ii

heat of the water or other heat exchange medium flowing in tube 62. The heat Qg Q^{that is} can be extracted by water or other heat exchange medium can be represented by the following relationship:

Q₂ = ⁿ2^(hf -^hF^} ’

Θ i where is the enthalpy of the water at the outlet and is the enthalpy of the water at the inlet of the heat exchanger. Obviously the amount of heat transferred to the water is at its maximum when the inlet water temperature is at its minimum. Therefore, if the coolant quality is not to be lower than 0.25 (except perhaps briefly during start-up conditions) then Qg ¿1 maximum must be limited to a value which ensures that X remains at 0.25 or higher under minimum inlet water temperature conditions.

The heat transferred through the wall of tube 62 from the coolant to the water can be represented by:

Qj = UA ΔT where U is the total heat transfer coefficient for tube 62, A is the surface area of tube 62 and

Sheet no.

T is the average temperature difference across the tube walls separating the refrigerant from the water. By selecting heat exchanger sizes according to the foregoing relationships taught by the present invention, the present invention can be easily added to existing refrigeration and air conditioning equipment without producing excessive condensation as previously analyzed. Thus, the present invention contemplates that the total heat transfer coefficient XJ of the tube wall separating the coolant from the water (as determined, of course, by the nature of the material used, its surface characteristics and the velocity of fluid flow over their opposing surfaces), the heat transfer area A of the tube wall, the average temperature difference ΔT and the mass flow rate f¡2 of the water in the heat exchanger will together be effective to ensure that, for given equipment parameters of the refrigeration equipment, the quality of the coolant leaving the heat exchanger will not be less than 0.25. Of course, the invention can also be included in new equipment

The present invention may be practiced with the total cross-sectional flow area in the shell 60 equal to the flow area of the line 30 from the refrigerant compressor; however, it has been found that certain significant variations are achieved by increasing the size of the flow area in the shell 60 relative to the line 30. This increase in flow area results in a drop in the velocity of the coolant as it flows through the heat exchanger 12. This increase in volume in the shell 60 and its consequent drop in velocity produces some opposing effects. For example, the residence time of each volume of coolant in the heat exchanger 12 is increased, which tends to increase the heat transfer to the tube 62. Furthermore, the total mass in the shell 60 and the total heat available for transfer without total condensation are increased. Furthermore, the heat transfer coefficient through the tube 62 decreases due to the velocity drop, which tends to reduce the heat transfer through the tube 62. In the present invention, the velocity of the coolant through the shell 60 is adjusted by selecting a flow area in the shell high enough to enhance heat transfer to the water or other heat transfer medium in the tube 62 without reducing the temperature of the coolant to levels where excessive liquid will be present. In practice, the flow area of the shell 60 may be up to 4-5 times larger than the flow area in the pipe 30 or even more, depending on the operating regime of the compressor. When the heat exchanger 12 is to be used with all compressors in the capacity range of, for example, 5 to 10 tons, the flow area of the shell would be

-22that it be sized to operate optimally with a 7.5 ton unit since if it were sized for the 10 ton unit, the 5 ton unit would likely completely condense the refrigerant in the shell 60 due to an excessively low velocity and low amount of refrigerant gas in the heat exchanger shell.

Additional advantages are achieved in the present invention by shot peening or shot peening the outer surface of tube 62 as indicated at 64 of Figures 6A and 6B. This surface treatment increases the heat transfer area of the copper tube by up to 20 percent, thereby greatly improving the heat transfer capacity of the heat exchanger 12. The techniques of forming the shell 60 and tube 62 can be used for this purpose. For example, The use of 1.0 to 1.7 nm diameter steel pellets has been found to be effective, operating at approximately 12.2 kg/cm2 with the use of shot blasting equipment. Heat transfer is also enhanced by scribing grooves 66 on the inner surface of tube 62 at indicated small diameter locations opposite the valleys formed between the spiral protrusions on surface {-.

external tube 62,

Based on actual operating experience with heat exchangers that are embodiments of the present invention, heat can be efficiently extracted from

-23 equipment having compressors with capacities of 1 to 100 tons and operating with conventional refrigerants such as R-22. The flow rate in such cases is generally between 1.27 and 127 kilograms per minute through a hull area of between 2.19 and 24.96 square centimeters. Water flow rates of 3.7 to 113.5 liters per minute can be served with water tube flow areas of 0.90 to 4.99 square centimeters, assuming a tranj area.

heat difference from 0.051 to 2.55 square meters.

Figure 7 illustrates a schematic diagram of an application of the supplementary heat exchanger according to the present invention. An existing air conditioning or refrigeration compressor 68 discharges high pressure, high temperature refrigerant past a heat and pressure controller 70, after which the refrigerant gas flow is split to flow through line 30 to a pair of parallel heat exchangers in accordance with the present invention, located within leaf 10. After the heat has been recovered from the refrigerant gas, the gas exits the box 10 through line 32, recombines and flows to an existing air conditioning or refrigeration condenser coil 72 after which it flows to the evaporator coil (not illustrated).

On the water or other heat exchange medium side of the equipment a reservoir tank 74 is provided which

-v,jI

-24 loads water by passing a hose bib 76, through gate valve 78 to an auxiliary pump 80 which pumps the water or, if desired, other heat exchange medium through parallel gate valves 82 and 84 in heat inlet pipe 36. After flowing through the heat exchanger located in box 10, the water exits through pipe 52 and passes air inlets 86 and 88, gate valves 90 and 92, air inlet 94 and gate valve 96 before returning to storage tank 74.

Of course, the invention can be used in equipment that does not have a storage tank. An auxiliary equipment comprising a pump 98, gate valve 100, use location 102 and gate valve 104 serves to circulate heated water from storage tank 74 to a location for the proposed use. Use location 102 may be a unit heater located in a room to be heated, a coil located in an air duct, a baseboard heat exchanger, a pump. water source heat, a radiant heat panel, a radiator and the like,

Numerous embodiments of the disclosed invention have been extensively tested to determine their specific performance characteristics. Figure 8 illustrates in tabular form various test data that were generated in a test of a refrigeration unit that included

-25a supplemental heat exchanger in accordance with the present invention. The supplemental heat exchanger used during testing was sized for use in refrigeration and air conditioning equipment of 5 to 10 cubic feet capacity. This testing was conducted at an outside or ambient air temperature equivalent to 35°C, dry bulb. Additional testing at ambient temperatures of 29.4 to 37.7°C has been conducted with similar results. The dry bulb temperature of 35°C corresponds to the rating temperature used to evaluate refrigeration and air conditioning equipment in the United States of America under these API standards. Among other things, the data illustrated in Figure 8 indicate that the heat exchanger according to the invention is capable of heating water with an inlet temperature close to Ι7.7°θ to a temperature of 48.3°C in a very short time, i.e., in a single pass. Also, the heat exchanger recovered a maximum of 71.2 /£ of I heat that would have otherwise been wasted to the atmosphere during first-pass operation. During these tests, the water was continuously recirculated through a storage tank so that as its temperature rose during the course of the test, the percentage of heat recovered decreased as illustrated in Figure 8 as the inlet water temperature approached its limit of 82.2°C.

-26Figure 9A illustrates the time required for an actual production model according to the invention to raise the temperature of a given quantity of water by 55°C. Thus, using a 7.5 ton compressor unit, 151 tonnes of water were heated.

liters of water at 55°C in approximately one hour without auxiliary heating. When using a conventional hot water heater, it is often unnecessary to leave the conventional heating coils or gas in service when the present invention is in use; however, recovery times will be faster if the conventional hot water heat source and the invention are used. Figure 98 presents a similar plot indicating the temperature changes of a given quantity of water in one hour for various compressor sizes.

The percentage of energy reduction in the compressor is illustrated as a function of the inlet water temperature in Figure 10. When the equipment is operated with inlet water temperatures in the lower ranges, the refrigerant passing through the hot water heat exchanger according to the present invention is cooled substantially more than at the higher inlet temperature ranges. Consequently, the compressor inlet temperature is lower, which reduces compressor energy requirements and wear, as previously studied. However, even at the highest inlet water temperatures, the compressor's energy requirements are reduced.

Figure II shows a graphical representation of how the percentage of heat recovered depends on the inlet water temperature to the heat exchanger. Although the data presented in Figure II were generated in small capacity air conditioning and refrigeration equipment, the tendency towards a reduction in the percentage of heat recovered as the inlet water temperature increases

And it is clearly demonstrated, Of course, for a given size of heat exchanger, the efficiency of the equipment decreases as the capacity of the air conditioning or refrigeration equipment increases.

<img file="ES463581A1_D0002.tif" />

I tcij>i No. 28