US2993341A - Hot gas refrigeration system - Google Patents

Description

July 25, 1961 A B. NEWTON 2,993,341

HOT GAS REFRIGERATION SYSTEM Filed Feb. 5, 1958 I 5 Sheets-Sheet 1 IN l E N TOR BWQWMW/ZWYW ATTORNEYS. r u W July 25, 1961 A. B. NEWTON 2,993,341

HOT GAS REFRIGERATION SYSTEM Filed Feb. 3, 1958 5 Sheets-Sheet 2 ATTORNEYS.

July 25, 1961 A. B. NEWTON 2,993,341

HOT GAS REFRIGERATION SYSTEM Filed Feb. 5, 1958 5 Sheets-Sheet 3 ATTORNEYS.

This invention relates to an improvement in a hot gas refrigeration system, and more particularly, to a hot gas refrigeration system employing a thermo compressor.

This application is a continuation-in-part of mycopending application Serial No. 663,204 filed June 3, 1957, now Patent No. 2,909,902, October 27, 1959.

In the operation of hot gas refrigeration systems employing a thermo compressor, a distinct problem has arisen where the same fluid is employed as both the refrigerant and the energy producing gas. The thermo compressor heats the energy producing gas to an elevated temperature while the refrigerant operates at a reduced temperature. Providing a fluid that is stable at both of these extremes is a problem of long standing in the art. Particularly in the phase of the system where the fluid is subjected to high temperatures do problems arise. Many fluids currently employed as refrigerants lack the nec essary qualities for optimum operation in this phase. It is to be appreciated that because of the high temperatures employed in a thermo compressor, correspondingly high pressures are attained. Such being the case, it is of vital importance that the fluid be non-toxic since the chances of fluid escape are greatly magnified. Still further, the high temperatures promote decomposition of many fluids so that stability and resistance to explosion is a prime prerequisite in a fluid employed for this purpose.

Another desirable characteristic of a fluid to be employed in a system of the character described above is that it should always be at a temperature and pressure above the critical point while in the hot portion of the thermo compressor.

It is an object of this invention to provide an improvement in a hot gas refrigeration system that overcomes the problems set forth above. Another object is to provide an improved hot gas refrigeration system that possesses the desirable characteristics above described.

This invention is based in part upon my discovery that carbon dioxide uniquely possesses the characteristics necessary for optimum operation of a hot gas refrigeration system employing a thermo compressor.

This invention will be explained in conjunction with the accompanying drawing, in which- FIGURE 1 is a representation of a refrigeration system, the thermo compressor portion thereof being shown in section, and the remainder schematically;

FIGURE 2 is a view similar to FIGURE 1 in that a thermo compressor is shown in section and the remaining portion of the refrigeration system shown schematically but in which a modified form of thermo compressor is depicted;

FIGURE 3 is a view similar to FIGURES 1 and 2 but which employs yet another form of thermocompressor; and

FIGURE 4 is a schematic representation of a two-stage thermocompressor of the type shown in FIG. 3.

Referring now to the drawing, and in particular, FIG- URE 1, the letter A designates a casing which is divided into an upper power chamber and a lower work chamher by the transverse partition wall A. Extending below the bottom wall of the casing is a conduit part A which forms a suction manifold. The upper portion of the casing is formed in two parts, which may be secured together by bolts 1. Within the casing are two sets of pistons, one of which provides power in the upper chamber, and the other of which provides for the compressing ittes atent ice of a refrigerant. Power is supplied by pistons 2, 3 and 4, While refrigerant is compressed by the pistons numbored 5, 6 and 7. Each of the pistons operates in a chamber formed by casing walls, as illustrated in the drawing. The pairs of pistons 2 and 5, 3 and 6, 4 and 7, are each inter-connected by connecting rods 8, 9 and 10, respectively. Power thus transmitted directly from a power piston to a compressor piston. In addition each connecting rod is connected to a crankshaft M on which are located eccentrics (or cranks) which by means of connecting rods 12, 13 and 14 provide for the transmission of power from one set of pistons to another, and for their proper cycle relationship.

The power-producing cycle similar in operation to the more or less conventional hot air engine except that it employs a hot refrigerant gas. Heat is applied by means of burners 15 to the heads of each cylinder l6, l7 and r18. Below the heated area of each cylinder, regenerator sections 19, 20 and 21 are provided, together with cross connections or passages 19a and 20a so that the upper space above each piston is cross-connected to a lower space below an adjacent piston in the following order: 2 to 3, 3 to 4, and 4- to 2. The chamber 18 is connected to chamber 1 6 by means of a conduit 16a. The engine operates on a cycle comparable to hot air engines with the exception that refrigerant under pressure is used in place of air as the power producing medium.

Associated with each combination cylinder space is a small low capacity piston driven through the medium of an eccentric on the main crankshaft or rockshaft 11. These pistons are located in cylinders so that refrigerants from the refrigeration portion of the system may be pumped into the engine portion. They may employ a limited compression ratio which will automatically limit the increase in pressure in the engine section as compared to the refrigeration section. The pistons are designated by the numerals 22, 23 and 24. Above the pistons are passages connecting the piston chambers with the regenerator sections 19, 20 and 21 through the valve means 22a, 23a and 24a which are effective in permitting refrigerants to flow into the engine section but which operate to prevent refrigerants from returning to the lower or compression portion of the structure. Each piston is equipped with a conventional suction valve (designated 22c, 23c and 240, respectively) which permits the flow of refrigerant from the lower refrigerant chamber into the work chamber, while preventing return flow into the refrigerant chamber. In the drawing, the eccentrics for operating the pistons 22, 23 and 24 are designated by the numerals 22b, 23b and 24b.

The limited compression ratio of the pistons 22, 23 and 24 may be used to limit the power of the engine by means of limiting the pressure in the power piston chambers. However, it is sometimes advantageous to operate the refrigeration cycle at less power input, and furthermore, an alternate manner of limiting the maximum power may be employed as follows:

A pressure limiting device 25 normally urged inwardly by spring 25a, is associated with bleed tubesr26, 27 and 28 so as to close the same, or, at a given pressure in the power chamber, to release refrigerants so that refrigerant is bled out of the tubes into the water cooled condenser 29 of the refrigeration system. The pressure at which this action occurs may be varied, as for example, by the use of temperature responsive bulb 30 which is responsive to the temperature in the refrigerated or air-conditioned space, and additionally, if desired, by an outside temperature responsive bulb 31 which serves to increase the capacity during periods of warm weather or decrease it during periods of cool weather. Other means of eifecting the bleed pressure may also be employed such, for example,

a reduction in pressure within chambers 16, 17 and 18.

A conventional refrigeration system is operatively associated with unit A, consistingof evaporator 32, suction manifolds 33, and discharge manifolds 34 communicating through a conduit indicated by the line 34a with the condenser 29. Flow of refrigerant occurs from condenser 29 through expansion valve 36 into evaporator 32, thence back to the compressor A for cyclic return to the refrigeration circuit through condenser 29. Thus, it is apparent that the same fluid circulates in the refrigeration cycle as in the power cycle.

The system may be started and stopped by means of a conventional thermostat 39 which operates through limit controls such as 49 responding to high refrigerant temperature and 41 responding to high engine temperature. Assuming that a demand for cooling has existed for some time, thermostat 39 will maintain valve 42 in an open position, allowing fuel to enter the burner and heat the engine chambers 16, 17 and 18. To further such heating, fins, as indicated by the numeral 43, may be employed. The flue gases may be expelled through one or more flues, 44, 45, etc. Furthermore, the gas may be lighted and controlled safety-wise by a conventional pilot, as at 46.

Provision is made for re-starting the engine after shutdown, and this provision is associated with the action at the time of shutting down. When the thermostat 39 is satisfied, it closes valve 42 and simultaneously, by means of a combination relay and timer 47, closes valve 35 and opens valve 48. The liquid refrigerant is then diverted from the expansion valve 36 into auxiliary receiver 49 during the cool-down or coasting period of the engine. The refrigerant enters check valve 50 (the use of which is optional), and receiver 49 may be supplied with a relief device 51 so that in the event excessive pressure is developed, the refrigerant will relieve or flow back into the water-cooled condenser 29 in sufficient quantity to remove the pressure hazard. During the coasting period of the engine, the refrigerant, carbon dioxide, can be accumulated in receiver 49 either as a liquid or as a super-critical gas. That this is possible can be appreciated from the fact that the critical temperature for carbon dioxide is within the realm of room temperatures and because the shape of the constant temperature and constant pressure lines on the T-S diagram make the sequence of pressure change during starting the same whether the carbon dioxide is accumulated as a liquid or as a gas.

When the thermostat again calls for an operation of the equipment, it opens valve 42 to ignite the main gas burners 15. It also opens auxiliary gas valve 52 to ignite burner 53, thus applying heat to auxiliary receiver 49. Valve 54 is also opened at the same time so as to apply higher pressure refrigerant to chamber 55. In chamber 55 is a disk 55a rotatably mounted on the main crankshaft 11 and provided with a valve passage 55b sequentially registering with tubes 56, 57 and 58, and communicating also with the space 550. This disk acts as a valve for permitting successive flow of refrigerant into the tubes for starting the operation of the pistons as the transverse opening 55b is brought sequentially into registry with the tubes. The rise of pressure brought about by the flow of highly heated refrigerant through the tubes starts the movement of the pistons, which is immediately augmented by the rise in pressure of the next appropriate space as well as by the heat input from the main burner 15. The combination of relay timer 47 soon closes valve 52 and somewhat later closes valve 54, and the engine then continues to operate under the heat input of the main burner 15. Alternately, the speed of rotation of the engine may be used to close valve 52 and valve 54 rather than the timing action of a relay such as 47.

Certain other pieces of equipment, such as fans and pumps, may frequently have to be operated in conjunction with refrigerant apparatus. This can be done by themain engine in the obvious manner of providing a shaft seal for crankshaft 11 and appropriate driving means external to the engine for fans, pumps, etc. However, an alternate method is shown in which a turbine or positive displacement engine 59 drives apparatus such as fan 60 or pump 61. This engine 59 obtains its energy from the high pressure refrigerant line 34a through valve 62 shown controlled by governor 63. This means for driving such auxiliary mechanism is provided without the necessity of using electrical connections of any kind, and even though this is accomplished in the refrigerant portion of the cycle, the low cost of fuels used for direct firing permits this action without excessively burdening the system with cost of operation.

In the operation of the foregoing structure, the use of carbon dioxide instead of a noncondensible gas, such as air, permits one to take advantage of a partial condensation cycle, if so desired. This is accomplished by adjusting the pressure levels in the chambers 16, 17 and 18, as controlled by the controller 25, to a point in which some of the refrigerant condenses as it passes through regenerator 19, 20 or 21 into the corresponding cold space below. This causes a marked further reduction in volume while raising the mean effective pressure. As the combined remaining gas and condensed refrigerant is forced back through the regenerator, the condensed refrigerant is re-evaporated as the condensed refrigerant comes into intimate contact with the heated exchanger. By control of the pressure in chambers 16, 17 and 18, it is thus possible to operate above the critical temperature of the refrigerant during the hot portion of the cycle and below the critical temperature during the cold portion of the cycle, in each set of chambers. This yields a mean effective pressure greater than that achievable in a cycle which did not cross the critical point.

Carbon dioxide is particularly adapted for operation in the engine and compressor system above described. Carbon dioxide has sufiicient stability at the elevated temperature in the hot end of the cylinder while always being at a temperature and pressure above the critical point, at the same time being effective as a refrigerant in the operation of the refrigeration system. .For these reasons, and others, carbon dioxide appears to be unique as a combined refrigerant and energy producing gas in the thermo compressor of hot gas systems. Carbon dioxide may be effectively employed for operation in the power cycle on both sides of the critical pressure. In fact, with sufficient cooling of the bottom end of the cylinder, there can be easily a zone of condensation which will limit the high pressure attainable by heating gases in the hot end of the cylinder, whereby some of the energy is transferred directly from the heat input at one end of the cylinder to refrigerant at the other end of the cylinder. Putting the matter in another way, the carbon dioxide compresses itself in the thermocompressor and then expands through an expansion valve in the evaporator without ever being subjected to an external power cycle, and in this operation the carbon dioxide has peculiarly excellent characteristics and is unique.

In FIGURE 2 of the drawing, a modified form of thermocompressor is designated generally with the letter B and the refrigeration system in which it is employed is designated generally with the letter C. The refrigeration system C is for the most part conventional, and provides a condenser and an evaporator coil 111, connected together through a conduit 112 having an expansion valve 113 interposed therein. A conduit 114 leads from the evaporator 111 to a manifold 115 through a pressure regulator valve 116, the inclusion of which in the system is optional. The condenser 110 is connected through a conduit 117 with a manifold 118. The condenser 110 is cooled by a Water coil 119 mounted in heat exchange relation therewith and that is" connected through a conduit 120 and control valve 121 with a source of water (not shown). Preferably, a bypass conduit 122 provided with a control valve 123 bypasses the control valve 121, and this bypass is utilized in initiating a refrigeration cycle in a manner that will be described hereinafter. It may be noted that a capillary tube 124 is connected at one end with the expansion valve 113 and at its other end is equipped with a thermally sensitive bulb in heat exchange relation with the flow conduit 114.

The compressor B is equipped with at least one cylinder, and preferably a plurality of cylinders. In the illustration of FIGURE 2, two cylinders are shown, and since these cylinders and their associated parts are identical in construction, only one will be described; and for purposes of identification cylinders and their associated components will be designated by the letters a and h following each numeral. Specifically then, the cylinder on the left in FIGURE 2 will be designated with the numeral and letter 125a while the cylinder on the right will be designated as 125b. Mounted for reciprocatory motion within the cylinders are the pistons 126a and 12612.

Mounted below the cylinder is a crankcase 127 that is mounted for rotation therein upon the bearings 128 and 129 and a crankshaft 130 that may be rotatably supported intermediate the ends thereof in a main bearing assembly 131 suitably supported or secured to the casing 127. The crankshaft 130 is coupled to the pistons 126a and 1261) respectively through the connecting rods 132a and 13212, and the piston rods 133a and 133b. At their upper ends the piston rods are secured to the pistons and at their lower ends are secured at the joints 134a and 134b to the connecting rods in a conventional manner as are the connecting rods secured to the crankshaft. Thus when the crankshaft is rotated, the pistons are reciprocated in their cylinders.

Preferably, a low energy power source is employed for rotating the crankshaft 130 so as to reciprocate the pistons within their cylinders. Since the energy for compression is obtained from means to be subsequently described and that is apart from the power source, only sufiicient power need be provided to the crankshaft 130 for overcoming the friction of the moving parts and for overcoming whatever friction may appear as refrigerant flows from one end to the other end of the cylinders and over the reciprocable distance therein. A number of different arrangements might be provided for reciprocating the pistons through rotation of the crankshaft 130; and one example arrangement is illustrated in FIGURE 2.

Shown in FIGURE 2 is a small motor 135 having a driving member 136 fixed to the shaft 137a thereof. The driving member 136 is semi-cylindrical and receives therein an armature 137 that is directly connected to the crankshaft 130. As the motor 135 rotates, the driving member 136 is rotated and thereby causes the armature 137 to rotate which then in turn drives the crankshaft 130. The members 136 and 137 might be a magnetic clutch, or if desired, the number 136 could be the field windings of a motor while the number 137 could be the rotor of the motor.

It is desired to provide the crankcase 127 as a sealed unit and for this purpose a seal member 138 is provided about the rotor 137. The member 138 is sealingly secured to the casing 127 and is preferably formed'of a non-magnetic material that will not interfere with the operation of the driving member 136 and the rotor 137. It will be apparent that a lubricant will ordinarily be provided within the crankcase chamber 139 for lubricating the crankshaft 130, as well as the connecting rods 132a and 1321) and the piston rods 133a and 133k. Lubricant is not required within the cylinders 125a and 125k and, therefore, the piston rods 133a and 133b, where they eX- tend through the bosses 140 and 141 of the casing 127, are preferably provided with packing glands so as to prevent the admission of lubricant from the crankcase chamber-139 and into the cylinders.

Provided about the upper end portions of the cylinders 125a and 125b is a casing 142 that is rigidly secured to the cylinders at approximately the mid-portions thereof. The casing 142 is provided with spaced-apart openings 143 and 1144 through the top wall thereof that are in alignment, respectively, with the upper ends of the cylinders 125a and 125b. A manifold 145 adapted to be secured to a source of combustible gas through a control valve 146 is equipped with burners 147 and 148 that are aligned, respectively, with the upper ends of the cylinders 125a and 1125b. About the burners 147 and 148, the casing 142 provides an inwardly-tapered annular flange 149 equipped at its lower end with an outwardly-extending annular skirt 150. The casing provides a similar flange 151 and skirt portion 152 about the burner 148. The burners function in a conventional manner to burn a combustible fuel supplied thereto, secondary air for combustion entering the casing 142 through the apertures 143 and 144, and primary air being entrained in the fuel. The casing 142 is provided with an exhaust port 153 through which the products of combustion are removed from the chamber defined by the casing 142. It is to be appreciated that either the combustion air or the gas itself may be preheated by heat exchange with the flue gases in order to even further improve the efficiency of the system described.

While the upper end portion of the cylinders are heated, the lower end portions are cooled. To accomplish this result, preferably cooling coils 154a and 154b are provided, respectively, about the cylinder ends, and these coils are connected together in series by a conduit 155. Liquid for cooling the cylinders is supplied to the coil 154 b through the conduit 156 that is connected with the cooling coil 119 and the condenser 110. The liquid, which ordinarily will be water, may be discharged to waste through the outlet conduit 157 that is connected to the coil 154a. While the cooling coils are shown connected in series, it will be appreciated that a parallel arrangement might be provided, although ordinarily a series waterfiow path will be preferable.

To facilitate heat exchange with a refrigerant within the cylinders 125a and 125b, the upper end portions of these cylinders are provided with external fins 158a and 1531). Each of the cylinders internally is provided with internal fins 159a and 15% that extend longitudinally of the cylinders. The internal heat exchange fins are oriented about the cylinder in spaced apart relation, and overlapping the same in intermeshed and nesting relation therewith are the external fins 1611a and 16% that are provided by each of the pistons. The pistons are freely fitted within the cylinder so that they reciprocate therein without engagement between the internal and external fins being provided. Therefore, fiuid within the cylinder is free to pass from one end to the other end thereof as the pistons reciprocate. Preferably, the cylinders and their pistons are cylindrical throughout the central portion thereof, and as shown in FIGURE 2, and have end sections attached thereto of conical configuration.

At their lower ends, the cylinders are provided with ports arranged to produce a two-stage compression. Cylinder 125b communicates with manifold through a port 16115 in which is positioned a control valve 162b, the cylinder a having an inlet port 161a. Similarly, each of the cylinders is provided respectively with outlet ports 163a and 16312. The outlet port 16% of cylinder 125bcommunicates with outlet 161a of cylinder 125a through valve 164]). In this arrangement the second stage cylinder needs no inlet valve. An outlet valve 164a controls flow from cylinder 125a to manifold 118. Refrigerant is admitted into the lower end portions of the right-hand cylinder 1251: through an inlet port that communicates with manifold 115, which in turn communicates with the conduit 114 and evaporator 111. Compressed refrigerant is expelled from the left-hand cylinder 125a through the discharge port that communicates with the manifold 118, which in turn is connected to the condenser 115 In the operation of the apparatus, it is necessary to initiate rotation of the compressor, ignition of the burners, and start of water flow. These may occur simultaneously or in any sequence suitable for a given engine. For example, the motor 135 can be first energized to rotate the crankshaft 130 and to reciprocate the pistons 1216a and 12Gb Within their respective cylinders. At approximately the same time, the control valve 146 is opened to supply combustible gas to the burners 147 and 14-8 which are then ignited. The auxiliary water control valve 123 is then opened to permit water to flow through the coil 119 to cool the condenser no and also permit the water to flow through the cooling coils 154a and 1514b to cool the lower end portions of the cylinders. The purpose of the by-pass 122 and its flow control valve 123 is to assure that a relatively small amount of water will flow initially while the refrigerant cycle is placed in operation, the purpose of this water being to cool the lower end of the cylinders during the starting procedure. With these steps taken, the upper end portions of the cylinders are heated while the lower end portions thereof are cooled, and at the same time the condenser 110 is cooled. If the mass is very high in cylinders 125a and 125b, it might be desirable to start heating the cylinders first, followed by water flow and then compressor rotation. This sequence has been found particularly applicable when carbon dioxide is employed as the refrigerant.

Energizing of the motor 135 causes the pistons to reciprocate within their cylinders, and such reciprocation causes a displacement of the refrigerant carbon dioxide within their cylinders, first from one end thereof to the other, and thereafter to the first end. Reciprocation of the pistons causes cyclic repetition of this fluid flow or fluid displacement within the cylinders. In one position of the pistons, refrigerant is drawn into the cylinders from the evaporator 111, and after the compression of that refrigerant and following a reciprocation of the pistons", the fluid is discharged through the outlet ports and is pumped into the condenser 110.

In the position of the pistons as is shown in FIG. 2, the piston 126a is in substantially its uppermost position within its cylinder, While the piston 12611 is in its lowermost position within its cylinder. Assuming the positon of piston 126a, the cavity of the cylinder 125a beneath the piston is filled with cool carbon dioxide that has been admitted through the cylinder 125b which has performed the first stage of compression. As the piston 126a moves downwardly to fill the cylinder cavity therebelow, it displaces the cold carbon dioxide and causes it to flow upwardly in heat transfer contact with the internal fins 159a of the cylinder and the external fins 160a of the piston. The fins are progressively warmer toward the top of the cylinder, and as the refrigerant flows upwardly, the temperature thereof is raised, and correspondingly its pressure is raised so that a portion of the refrigerant carbon dioxide in expanded condition is forced outwardly through the discharge valve 164a and the discharge port 163a and into the manifold 118, and from there into the condenser 110.

To permit the achievement of maximum efliciencies, it may be desirable to increase the displacement of the first stage cylinder. This can be done by making the diameter or stroke, for example, of cylinder 12517 greater than that of cylinder 125a. V

Stated another way, the refrigerant gas leaves and enters the cylinder from the cold end there of. The gas entering the cylinder from the evaporator is cooled and must be heated many hundreds of degrees in' the upper end of the cylinder toincrease the pressure. Discharging it at this high temperature into the condenser would require a very much oversize condenser, and to avoid this, the carbon dioxide is discharged at the bottom of the cylinder, and it is important that the portion of the gas which is discharged has never been heated, or, if it was partially heated, becomes cooled as it flows past the fins on the piston and cylinder.

7 Referring now to the cylinder 12517 in the position of the piston 126b therein, the major volume of the carbon dioxide refrigerant in that cylinder is in the hot end thereof, and is thereby heated to a high temperature since the upper end portion of the cylinder is heated by the burner 148. Thus, the pressure of the heated refrigerant will increase. As the pressure increases, refrigerant carbon dioxide is forced out of the cylinder through the discharge port 1639b and its discharge valve 16% into cylinder a. As the piston 126b rises in its cylinder, the heated refrigerant is displaced to the cool end of the cylinder, and its movement passes in heat transfer contact with the internal fins 15% of the cylinder and the external fins 16011 of the piston. Since these pistons are progressively cooler toward the cold end of the cylinder, the refrigerant is cooled thereby as it flows thereover. It will be appreciated that the fins 16Gb of the piston are progressively colder toward the bottom end thereof because those fins have been cooled by direct heat transfer at the cold end of the cylinder during the time the piston is within the lower or cooled end portion of the cylinder. During the time the refrigerated carbon dioxide is transferring to the cold end of the cylinder, the refrigerant is cooled and the pressure thereof is reduced until a sufficiently low pressure is reached to open the suction regulating valve 116, and refrigerant will then be drawn in from the evaporator 111 and the evaporator will be cooled by this movement of the refrigerant.

This cyclic operation is carried on repetitiously, with the result that the temperature changes within the cylinder 125 b serve to draw suction refrigerant in through the suction valve 162!) and to discharge it through the discharge valve 16% tocylinder 125a, which discharges refrigerant back to the condenser. Thus, the heat energy of the burners 147 and 148 is transferred directly into the compression of therefrigerant canbon dioxide through the utilization of the extremely small amount of power which is supplied by the external power source or specifically the motor 135. Actually, the only power that needs be supplied by the external power source is that which is suflicient to overcome the friction of the mechanical components and of the flow. of the refrigerant carbon dioxide past the pistons 126a and 12612.

There is a gradual change in temperature from the hot end portions of the cylinders to the cold end portions thereof. This temperature gradient is constantly maintained so that the heat transfer may be augmented by the fins, as described. In addition, the moving fins, or the fins provided by the pistons 126a and 12611, serve as moving regener'ators with respect to the refrigerant carbon dioxide, and as heat transfer units which alternately come in contact with the cold and hot end portions of the cylinder for further facilitating heat transfer.

The degree of cooling of the lower end portions of the cylinders 125a and 1251) may be varied as desired. Variations may be provided by controlling the volume of liquid flowing through the coils 154a and 154k (which are in good heat exchange relation With the cylinders and are preferably in contact therewith), and might also be provided by varying the temperature of the liquid flowing therethrough. The greater the amount of cooling of the lower end portions of the cylinders, the greater will be the tendency for some of the refrigerant carbon dioxide to condense within the lower portions of the cylinders. However, no harm will be done by such condensation, and in the most extreme case where the lower end portions of the cylinders are cooled to a very low temperature, all of the condensation of the refrigerant may occur within the cylinders; This is possible since clearances between the sidesof the piston and the cylinder are such as to provide passages for the escape of any liquid which would be inadvertently trapped at the end of the piston stroke. In this case, the condensed refrigerant may be removed from each cylinder as it condenses during the compression stroke.

Yet another form of thermocompressor in a conventional refrigeration system and which provides extremely satisfactory results when carbon dioxide is employed as both the energy producing gas and refrigerant fluid, is shown in FIG. 3. In FIG. 3, the letter D designates generally a thermocompressor, while the letter E desig- ,nates a refrigeration system. The refrigeration system designated by the letter E includes a condenser 210, an expansion valve 211, and an evaporator 212, all connected in series through conduit 213 through which flows the refrigerant carbon dioxide. Also interconnected in conduit 213 is refrigerant-distributing valve 214 which is coupled to evaporator 212 through port 215. Valve 214- is coupled to the conduit communicating with condenser 210 through port 216 and with thermocompressor D through conduit 217 and port 218. High pressure carbon dioxide within thermocompressor D flows into chamber 219 of valve 214 and opens discharge valve 220 while closing intake valve 221. This permits refrigerant to flow into condenser 21%. Refrigerant from condenser 210 flows to evaporator 212 and then reenters thermocompressor D by passing through intake valve 221.

The thermocompressor unit D is provided with a closed compressor cylinder 222 having an upper hot end of conical or other surface of revolution for conducting large amounts of heat from a burner 223 to the interior of the cylinder 222. As in the structure shown in FIG. 2, the compressor cylinder 222 may be provided with fins to aid the transfer of heat from burner 223 to the interior of cylinder 222.

The lower cold end or head of cylinder 222 has a water jacket 224 having an inlet 225 and a discharge port 226. Water for this purpose may be conveniently taken from condenser 21%, as indicated at 210a, the flow rate of water in condenser 210 being regulated by a pressureresponsive valve 21Gb in the refrigerant line between valve 214 and condenser 21%). Valve 21Gb actuates valve 210a in the water supply line 210d to condenser 210, the valve 2100 being provided with a conventional by-pass 210a. The central portion of cylinder 222 is equipped with a heat regenerator 227 provided with passages for the flow of gas. A cylinder liner 22% is concentrically placed within cylinder 222 and spaced with a narrow gas passage 229 leading from the upper hot space 230 through regenerator 227 to the bottom cold space 231. A gas-moving or transfer plunger 232 is reciprocably mounted within cylinder 222 and has its ends constructed to conform with the ends of cylinder 222 and the cylinder liner 228, the plunger 232 operating in close approximation to cylinder liner 228 but without touching the same. The stroke of the transfer piston 232 is controlled by piston 233, piston rod 234, connecting rod 235, crank 236, shaft 237, and flywheel 238.

The piston 233 serves to furnish the power to operate the compressor by utilizing the variation of pressure in the compressor cylinder 222, as is hereinafter discussed. A surge chamber 239 communicates with the bore 240 which receives piston 233. Surge chamber 239 serves to furnish power for the suction stroke by storing. the excess power from the compression stroke. Thus, the embodiment presented in FIG. 3 provides an alternative means for moving the piston in a thermocompressor as compared to the motor 135 shown in FIG. 2.

As transfer piston 232 moves from the hot space 230 to the cold space 231, it displaces the cold carbon dioxide from space 231 through the regenerator 227 and annular space 229 to the hot space 236. During this transfer, the gas is heated by the regenerator 213 and the hot cylinder walls, the heat being derived from burner 223. This latter heating is assisted by the narrow annular space 229 between cylinder 222 and liner 228. The heating of the gas raises the pressure until the back or differential pressure valve 214 opens. Thereafter, as pointed out above, the pressure remains constant while gas is being discharged through discharge valve 220 to refrigeration system E. On the return or suction stroke, the hot gas in the space 230 flows through the annular space 229 and regenerator 227 to the cold space 231 leaving heat in regenerator 227 and being further cooled by the water jacket 224. This cooling of the gas causes the pressure to fall during the first part of the stroke and then the pressure remains constant while the gas flows from evaporator 212 through intake valve 214 to the cold end 231 of compressor cylinder 222. Since the pressure in cylinder 222 rises during the first part of the compression stroke and remains high during the latter part of the stroke while it falls during the first part of the suction stroke and remains low during the latter part of the suction stroke, the mean pressure on the compression stroke is higher than the mean pressure on the suction stroke.

If no refrigerant is taken from evaporator 212, the discharge from the compressor continues to decrease and the compressor would stop except for the fact that the piston 233 has two reduced sections 241 and 242 which act as ports for the transfer of gas from the cylinder 222 to the surge tank 239. If the valve 243 in conduit 244 is opened when reduced section 241 moves adjacent to the top port of by-pass line 244 at the end of the compression stroke, the high pressure gas in cylinder 222 flows through the by-pass conduit 244 to the surge tank 233. On the return or suction stroke, the high pressure gas in surge tank 239 acts on piston 233 to overcome the more rapidly falling pressure in section 222 and also furnish power to operate the compressor. At the end of the suction stroke, the reduced section 242 moves adjacent to the port of by-pass conduit 244, allowing the high pressure gas in surge chamber 239 to flow into cylinder 222 so that on the compression stroke the rapidly rising pressure in cylinder 222 serves to compress the gas in surge chamber 239 and furnish power to operate the compressor. By adjusting the manually-operable valve 243, the idling speed of the compressor may be controlled. When the refrigerant gas is drawn from the evaporator 212, the thermocompressor speed automatically increases to meet the increased demand. The thermocompressor thus serves as a self-contained unit.

It is tobe appreciated that the thermocompressor of FIG. 3 can be supplemented by a second cylinder to pro vide a two-stage compression cycle of the nature seen in FIG. 2.

In FIG. 4, a schematic representation is given of a modified form of hot gas refrigeration system employing the type of thermocompressor shown in detail in FIG. 3. For that reason, it is believed unnecessary to show the system in detail. In FIG. 4, the letter F designates a thermocompressor of the type shown in FIG. 3 and designated by the letter D. In FIG. 4, the letter G designates a second such thermocompressor, the two compressors being interconnected in series through a valve designated by the numeral 314 and which is similar to valve 214 of FIG. 3. In FIG. 4, a conduit line 313 interconnects valve 314 with an evaporator 312. A second conduit 316 connects valve 314 with thermocompressor G, while conduit 317 connects valve 314 with thermocompressor F, much the same as conduit 217 communicates valve 214 with thermocompressor D in FIG. 3. A second outlet port is provided in thermocompressor G and is interconnected through line 345 with a valve 346 such as a float or expansion valve. Valve 346 in turn is connected to evaporator 312. It is preferred to locate valve 346 as close as possible to thermocompressor G so as to keep the clearance volume at as low a value as possible. Cooling jackets are provided thermocompressors F and G, similar to the jacket 224 of FIG. 3 and cooling water is sent through the staged thermocompressors F and G in countercurrent flow, -i.e.,

. 11 first to thermocompressor G and then to thermocompressor F.

As in the embodiment of the invention illustrated in FIG. 2, it is possible to obtain maximum efliciency of operation through providing a different displacement in the two or more cylinders making up the thermocompressor. In the embodiment of the invention shown in FIG. 4, it is possible to connect the piston of thermocompressor G to the same crankshaft as that connected to the piston of thermocompressor F but providing a different diameter or stroke in thermocompressor G than in thermocompressor F. Further, if a common crankshaft for the two thermocompressors is employed, it is possible to use only one driving piston such as piston 233. On the other hand, if separate cranks and crankshafts are employed, each with its own driving piston, the differences in displacement in the various thermocompressor cylinders can be obtained by allowing the respective pistons to travel at different speeds. In this manner, the number of reciprocations per unit of time in the low stage cylinder could easily be 40% or 50% greater than that in the higher stage cylinder.

Valve 346 only perm-its the outflow of refrigerant from thermocompressor G to evaporator 312 when the carbon dioxide is in a liquid state. This, therefore, eliminates the need for a condenser and an expansion valve such as are shown in FIG. 3. Where, however, carbon dioxide is employed as the refrigerant, the critical temperature being in the range of ordinary ambient temperatures, requires cooling water sufficiently low in temperature so as to condense all of the refrigerant. When this is unavailable, or otherwise unfeasible, an expansion valve 346 can beemployed that is equipped with a sensing bulb 346a located in the outlet line 313. Expansion valve 346 can thus measure the super heat in the refrigerant circulation system and operate to allow super-critical gas to leave thermocompressor G.

While, in the foregoing specification, embodiments of the invention have been set forth and described in considerable detail for the purpose of adequately illustrating and describing the invention, it will be apparent to those skilled in the art that numerous changes may be made in these details without departing from the spirit and principles of this invention. i

I claim:

1. In the operation of a refrigeration system including a thermocompressor, the improvement comprising condensing a refrigerant in the thermocompressor and limiting the refrigerant discharged from said thermocompressor to that in liquid form, whereby the need for a condenser in the refrigeration system is eliminated.

2. The method of claim 1, in which the said refrigerant is carbon dioxide.

3. In a refrigeration system, evaporator means, and thermocompressor means operatively connected to circulate a refrigerant, the said thermocompressor means comprising a closed cylinder heated at one end and cooled at the other end, piston means reciprocably mounted in said cylinder with flow passage means in said cylinder permitting fluid to by-pass said piston means, and conduit means communicating said cylinder with said evaporator means, said conduit means including valve means normally operative to pass only liquid refrigerant whereby liquid refrigerant is delivered from said thermocompressor means to said evaporator means.

4. The structure of claim 3, in which said valve means is equipped with means responsive to the refrigerant super heat and selectively permit the outflow of refrigerant in a super-critical gas phase from said thermocompressor means to said evaporator means.

5. In a refrigeration system, evaporator means, and at least two thermocompressor units interconnected in series to provide staged compression, the said evaporator means and thermocompressor units being operatively connected to circulate carbon dioxide as a refrigerant, conduit means communicating one of said thermocompressor units with a second of said thermocompressor units and said evaporator means, and second conduit means including valve means communicating the said sec- 0nd of said thermocompressor units with said evaporator means.

References Cited in the file of this patent UNITED STATES PATENTS 2,272,925 Smith Feb. 10, 1942 2,468,293 Du Pre Apr. 26, 1949 2,484,392 Heeckeren Oct. 11, 1949 2,621,474. Dros Dec. 16, 1952 2,721,728 Higgins Oct. 25, 1955 2,734,354 Kohler Feb. 14, 1956 2,771,751 Jonkers Nov. 27, 1956 2,803,951 Newton Aug. 27, 1957 2,824,430 Rinia Feb. 25, 1958 t

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