Патент USA US2116100код для вставки
May 3,1938. RJ. CRACKNÉLL REFRIGERATING APPARATUS Filed March 7, 1936 fM@ N.„FIV „è N 0mq .ma 5„0,1 n „w m ,[IL3„f. W6 1 „frAl 0 2,116,100 Patented May 3, 1938 f2,116,10() UNITED'STATES PATENT OFFICE 2,116,100 REFRIGERATING APPARATUS ‘ Richard John Cracknell, London, England, as-> signor to U. D'. Engineering Company Limited, London, England, a British company . Application March 7, 1936, Serial No. 67,672 In Great Britain A_ugustS, 1935 6 Claims. (Cl. 655-3) This invention comprises improvements'in or relating to refrigerating apparatus of the‘type in which the refrigerant evaporates in pipes or coils.It is known that the rate of heat transmission Ul in such evaporators is improved by increasing the relative amount of liquid refrigerant in the pipes or coils. This can be provided for by admitting the refrigerant ‘liquid after passing the expan 10 sion valve into a cylindrical vessel called a sepa rator which must be ñxed at a certain height heat exchanger so that its temperature when it enters the heat exchanger element will be higher than that of the liquid surrounding it and While still under the excess pressure it is cooled in the heat exchanger to such a temperature that 5 when it passes through the second pressure re ducing valve only a small amount of evaporation due to loss of pressure at the valve will take place. 'I'his ensures that the refrigerant entering the evaporator coils is mainly in the liquid form. 10 The heat exchanger receives from the evaporator _above the levell of 'the evaporator coils to which a mixture of still-liquid refrigerant and of re it is connected. In this vessel the gas formed frigerant which has been evaporated. In the when the liquid passes the expansion valve is heat exchanger such part of the refrigerant com 15 separated from the liquid and only the liquid ing from the evaporator as is still in the liquid 15 passes into the coils. The height above the evap >form will be gasiñed by receiving heat from the orator coils at which the separator must be fixed . refrigerant which is passing through the heat depends on the form or length of the coils, it exchanger to the evaporator. Consequently only being necessary to provide a sufficient head to the vapor will pass to the compressor which is used to deliver it to the condenser and there 20 feed the liquid to the coils >by gravity. In some cases owing to the length of theV coils in order to fore not only is the evaporator itself rendered Nl 0 provide a sufficient head to overcome the friction' more efficient by the reduction of vapor therein or resistance in the coils it would be necessary but the risk of knocking in the compressor is lto fix the separator at such a height above the obviated. ` ` The heat exchanger conveniently takes the 2A on coils as to make this method impracticable. In such cases a pump is sometimes used to force form of a separating vessel having an inlet for the liquid from the separator into the coils. a mixture of liquid and gases from the evapo This arrangement has the disadvantages that it rator, an outlet in the upper part to the sepa-_ involves the cost of a pump and motor to drive rator and a heat exchange element in the lower 30 it, also the cost of running the motor and in part through which the refrigerant from the 30 addition it involves a gland on the pump spindle condenser to the evaporator passes, said heat which must be kept gas tight. exchange element being so located as to be in Itis an object of the present invention to Contact with liquid refrigerant which separates provide means whereby the quantity of refrig 3 Gl erant in the evaporator coils is increased and at the same` time it is unnecessary to provide either a pump or a gravity head to ensure the < flow of the refrigerant through the evaporator. According to the present invention in an evap `4K0 orative refrigerator there is provided between the condenser and the evaporator a heat exchanger through which the refrigerant passes on its way to the evaporator, in‘combination. with a pres sure reducing expansion valve (for example, a 45 float-operated expansion valve) between the con denser and the heat exchanger and a second pressure reducing valve between the heat ex changer and the evaporator- and means to ref turn the refrigerantirom the evaporator to the 50 heat exchanger so as to extract heat from the refrigerant passing through the heat exchanger to the evaporator. In accordance with this arrangement the re frigerant from the condenser is not' allowed to 55 fall to the evaporator pressure while it ls in the from gases’in the separator. The refrigerant, therefore, does not enter the body of the sepa- 35 rator until it has passed through the evaporator. Around the coil forming the heat exchange ele _ment within the separator is a free space which is ñlled with liquid refrigerant coming from the evaporator and the purpose of the separator is, 40 therefore, in part, to separate this liquid from the vapor which is going to the compressor. The pressure reducingv expansion valve for con trolling the outflow from the condenser is con veniently of known type comprising a iloat-op- 45 erated expansion valve capable of delivering liq uid refrigerant to the heat exchanger coil whilst stopping the passage of -gaseous refrigerant. At the outlet from the heat exchanger the coil is provided with an automatic pressure reducing 50 valve capable of maintaining a pressure of, say, by way of example, 60 lbs. in the heat exchanger when there is a pressure of, say, 20 lbs. in the evaporator. As a result the float valve will re duce from the condenser pressure to the inter- 55 2 . 2,116,100 mediate pressure of 60 lbs. or so which is main tained in the heat exchanger. This reduction advantage that the separator and heat exchanger can be located at any level in relation to the of pressure at the float valve will be accompanied evaporator. by a corresponding reduction of temperature and f by some evaporation but the vapor is recondensed in the heat exchanger and the temperature fur I claim: 1. In an evaporative refrigerator the provision between the condenser and the evaporator of a ther reduced to such a level that only a small heat exchanger comprising a conduit having a amount of vapor is produced at the second pres heat-exchanging wall through which conduit the sure reducing valve. refrigerant passes on its way to the evaporator As the liquid passes the 10 pressure reducing valve under considerable pres- . and a refrigerant space adjacent to said conduit, sure it is unnecessary to provide a pump or any gravity head to force the refrigerant through the evaporator, so that the separator and heat exchanger can be fixed at any level in relation 15 to the evaporator. The accompanying drawing illustrates dia grammatically and by way of example o'ne ar rangement of apparatus in accordance with the invention. In the drawing: I I is a pipe carrying a refrig 20 erant from the condenser to a float-operated ex pansion valve I2 which may, for example, be of the type described in my United States Patent SpeciñcationNo. 2,024,721. From the expansion 25 valve liquid refrigerant passesby the pipe I3 to a heat exchanger coil I4 disposed in the lower part of a separating vessel I5 so that it is immersed in liquid refrigerant I6 in the vessel. 'I‘he outlet of the heat exchanger coil I4 passes to the reduc 30 ing valve I'I and thence to the evaporator coil I8. The return pipe I9 from the evaporator coil enters the upper part of the separating chamber I5 and here the mixture of liquid and gaseous refrigerant which cornes from the evaporator separates out. Only gaseous refrigerant is re turned by the pipe 20 to the compressor. It will be appreciated that the liquid refriger ant I6 in the separating vessel I5 cools the re frigerant passing from the heat exchanger coil Il 40 and therefore is itself gradually evaporated, and also continuously replenished by the supply from the evaporator coil. In due course the liquid refrigerant in the separating vessel I5 strikes a balance of level and temperature at which it re 45 mains constant. As the evaporator coil is more filled with liquid than when the separator I5 and heat exchanger coil are omitted, it is necessary _to allow suflicent extra quantity of refrigerant in the system to keep the evaporator coil so filled and also to allow for the extra refrigerant which 50 occupies the lower part of the separator I5. The amount of heat removed from the liquid coming from the condenser will depend upon the difference of temperature between the condenser 55 and evaporator. Under average conditions with ammonia as the refrigerant' it may be sufficient to evaporate in the heat exchanger from 10 to 15% of the total flow of refrigerant passing .into the evaporator. In that case 10 to 15% of the total 60 amount of liquid entering the evaporator will pass through the evaporator coils unevaporated and return to the heat exchanger where it is sep arated from the vapor and used to cool the liq uid going into the evaporator. A continuous sup ply of liquid is thus maintained in the heat ex changer. There is no gain or loss in this ex change of heat but it provides a simple means of increasing the amount of liquid in the evapora tor coils. This arrangement has, furthermorefthe ad 70 vantage that it can readily be lincorporated in existing refrigerating systems of the evapora tor type without modification of the evaporator or condenser units and will serve to increase the 75 capacity of the plant. It also has the important in combination with a pressure reducing expan sion valve between the condenser and the conduit of the heat exchanger and a second pressure re ducing valve between the conduit of the heat ex changer and the evaporator and means to return the spent refrigerant from the evaporator to the refrigerant space of the heat exchanger so as to extract heat from the refrigerant passing through the heat exchanger to the evaporator. 2. In an evaporative refrigerator the provision between the condenser and the evaporator of a heat exchanger comprising a conduit having a heat-exchanging wall through which conduit lthe refrigerant passes o_n its way to the evaporator and a refrigerant space adjacent to said conduit, 25 in combination with a pressure reducing float operated expansion valve between the condenser ' and the conduit of the heat exchanger and a sec ond pressure reducing valve between the conduit of the heat exchanger and the evaporator and means to return the spent refrigerant from the evaporator to the refrigerant space of the heat exchanger so as to extract heat from the refrig erant passing through the heat exchanger to the evaporator. . - 3. Apparatus as claimed in claim 1 wherein the heat exchanger takes the form of a separat ing vessel having an inlet for a mixture of liquid and gases from Ithe evaporator, an outlet in the upper part to the compressor and a heat exchange element in the lower part through which the re-frigerant passes from the condenser to the evap orator, said heat exchange element being so lo cated as to be in contact with liquid refrigerant which separates from gases in the separator. 4. Apparatus as claimed in claim 2 wherein the heat exchanger takes the form of a separating vessel having an inlet for a mixture of liquid and gases from the evaporator, an outlet in the upper part to the compressor and a heat exchange ele ment in the lower part through which the refrig erant passes from the condenser to the evapora tor, said heat exchange element being so located as to be in contact with liquid refrigerant which separates from gases in the separator. 5. In an evaporative refrigerator, the combina tion of a condenser, a pressure-reducing valve at the outlet yof the condenser such as to retain un condensed gases and pass condensed liquid there from, a heat exchange vessel, a conduit passing 60 through the lower part of the heat exchange ves sel ,from the pressure reducing valve, a second pressure-reducing valve _beyond the heat ex change vessel in the said conduit, an evaporator beyond the second pressure-reducing Valve, a 05 connection from the return pipe of the evapora tor to the heat exchanger so as to return unevap orated liquid refrigerant thereto, a compressor, a connection from the upper part of the heat ex change vessel to the compressor, and a connec tion from the compressor to the condenser. 6. An evaporative refrigerating system includ ing a compressor, a condenser, a float-operated expansion valve, a heat exchange element.- a pressure-reducing valve, a separator vessel in the 70 \ 3 2,116,100 lower part of which said element is disposed and the passage of unevaporated liquid refrigerant an evaporator, a conduit for the passage of liquid and gas to the separator, the quantity of said re frigerant in the system being in excess of the nor mal capacity of the evaporator so that the ex cess returns to the separator with the gas, the excess being sufficient to submerge said heat ex change element, a conduit from the upper part of said separator vessel for the passage of spent refrigerant from said condenser through said ñoat-operated expansion'valve to said heat ex QI change element, a conduit from said heat ex change element for the passage of liquid refrig erant from said element through said pressure reducing valve to said evaporator, said- pressure reducing valve being adapted to maintain a pres 10 sure in said element greater than the evaporator pressure but less than the condenser pressure, a conduit from said evaporator to aid separator for gas to said compressor and a conduit‘from said compressor for delivery >of compressed gaseous 1U refrigerant to said condenser. RICHARD JOHN CRACKNELL.