US 2042991 A
Description (OCR text may contain errors)
June 2, 1936- J. c. HARRIS, JR 2,042,991
METHOD OF AND APPARATUS FOR PRODUC ING VAPOR SATURATION Filed Nov. 26, 1934 Jeri/ 1,
Patented June 2, 1936 UNITED STATES METHOD OF AND APPARATUS FOR PRO- DUCING VAPOR SATURATION I James C. Harris, In, Baltlmore Md. Application November 26, 1934, Serial No. 754,920 3 claim. (or. 230-208) This invention relates to a method of and ap paratus for producing substantially constant saturation of a vapor under varying compresslon pressures and, among other objects, aims to provide improved means for injecting a liquid into a compressor during the compression stroke and controlling the injection automatically in response to both the temperature and the pressure of the vapor discharged from the compressor. The idea is to reduce the energy required to pump a given volume of vapor or gas from one temperature and pressure to a higher temperature and pressure by injecting liquid into the cylinder during the compression stroke so that the final state of the delivered vaporor gas is at a lower temperature than it would have been without liquid injection and nearithe saturated condition. In short, the vapor is compressed at constant quality and more vapor or gas is delivered from the cylinder discharge at the same pressure, but at lower temperature, with less expenditure of energy, on the same weight of vapor passing through the cycle. A unit weight of vapor has a definite latent heat capacity at a given pressure; therefore, the
' greater weight delivered per unit of expanded energy, the greater the heat pumping capacity of the compressor. i
Other aims and advantages of the invention will appear in the specification, when considered in connection with the accompanying drawing, wherein: r v
The figure is a diagrammatic illustratlonof one form of apparatus capable of practicing the method.
In many industrial processes, such as the manufacture of artificial ice using an ammonia compressor, for example, vapor is compressed to increase both its temperature and pressure. When the vapor is compressed to a very high pressure, it is superheated. This invention, therefore, aims to provide a novel method of and apparatusfor producing substantially constant saturation of the vapor while it is undergoing compression in order to reduce the power required to drive the compressor for a given operation. To this end, the method involves the injection of a liquid of' which the vapor undergoing compression is composed at a temperature preferably, though not necessarily, higher than the temperature of the vapor in the cylinder at its final compression pressure and controlling tne injection of said liquid in response to relative variations in the pressure andtemperature of the vapor as it isdischarged from the compressor. The liquid is preferably injected into the cylinder in the form of a fog or very fine mist and is introduced continuously during the compressionstroke so that it almost immediately evaporates and commingles with the vapor undergoing compression. For the purposes of this explanation, it will be assumed that the compression 5 is adiabatic.
Referring particularly to the illustrative apparatus for practicing the method, there is shown a vapor compressor l I) having a reciprocating piston II. The vapor is delivered from an evaporator to the cylinder through an intake conduit l2 and is discharged through an outlet conduit l3 leading to the heat exchanger. A spray nozzle ll, conveniently of the fuel injector type used in Diesel engines, is connected to dischargeinto the cylinder and is supplied with the saturating liquid through a conduit l5 by a variable discharge pump l6, also of the type generally employed in Diesel engines. The variable discharge pump is controlled in response to dlflerentials between pressure and'tem- 2o perature of the discharged vapor. In this instance, a pressurestat, including a cylinder I1, is connected to the discharge outlet l3 by a conduit l8. A piston IS in the cylinder is acted upon by the vapor and is normally held in the position shown by a coil spring 20 of the required compression strength. If desired, the strength of the spring may be varied in a well known manner to .vary the amount of delivered superheat. A piston rod 2| having rack teeth 22 meshing with a pinion 23 rotates or oscillates a cam 24, the surface of which is shaped to correspond with the pressure-temperature curve setting of the particular vapor at saturation. The cam will be different shapes for different vapors.
' In this example, the cam 24 acts on one end of a pivoted lever 25 which is pivotally connected at its other end to a link 26. The pivot is shown as being mounted on a compression spring 21. A temperature responsive device is also connected v to the link 26. It is shown as. being of the fluid pressure type having a diaphragm on a diaphragm casing 28 connected by a conduit 29 to a jacket 30 around the outlet pipe IS. The arrangement is such that movement is imparted to the link '26 in response to diiferentials in pressure and temperature. This link is connected to a control arm or member 3| of the variable discharge pump l6. As long as the pressure and temperature of the discharge vapor remain substantially constant, 59
the control mechanism will operate to deliver a constant quantity of liquid to'the cylinder through the discharge nozzle I. If the vapor should become superheated the quantity of liquid introduced will be increased. The pressurestat and 2. thermostat are so connected that they-respond almost immediately to changes in pressure and temperature of the discharging vapor. They are preferably arranged as near as is convenient to the discharge outlet of the compressor.
Assuming that the temperature remains substantially constant while the pressure varies, cam 24 moves the lever 25 up or down which in turn, lower or raise the link 26. when the is lowered, more liquid is discharged by the pump. When the pressure is constant and the temperature varies, the diaphragm moves lever 25 cordingly. Of course, the effect of the temperature changes is modified by thepressure. As the arm 3| is moved down, the quantity of the saturating liquid injected is increased. It will he understood that the pump is operated intermittently in the same manner as the fuel pump for 21. Diesel engine. The driving mechanism forms no part of the present invention.
In some instances, it is desirable to employ means to indicate the condition of the discharged vapor. For example, the liquid imector or the pump may fail to function and the vapor will be superheated, causing the normal troublsdue to excessive temperatures. In that case, an attendant should be notified of such condition. To that end, a suitable indicator, conveniently in the form of a pointer 32 on arm 3| cooperates with a scale 33 to indicate the quality of the vapor by the position ofthe pointer. Also,'a suitable remote signal, in the form of a lamp orbell 3| may be connected to the indicator to notify the attendant of an abnormal condition.
It will be apparent to those skilled in the art that the illustrative control mechanism is subject to wide variations and may takemany diflerent forms. However, in all cases, the action of the temperature responsive menu will be modified by the pressure responsive means to operate the control means. It is also contemplated that such control devices will have a very wide application to industrial processes wherein compressed vapors are employed and that, by maintaining the compressed vapors at substantially constant saturation an appreciable amount of power required for compression may be saved. For example, one
pound of ammonia vapor compremed adiabatiqally from a pressure of 34.28 pounds absolute and F. toa pressure of 170 pounds absolute will require approximately 5% more energy than when compressed from" the same condition to the same pressure and at a final temperature of 86 F. by injecting approximately .105 poimd of atomthe range of temperatures and pressures for a iaed liquid ammonia into the cylinder, lowering the superheat and taking up this energy by changing the liquid ammonia into vapor or by taking up the heat of superheat by the latent heat of the liquid ammonia.
While the particular apparatus shown necessarily practices the described method, it will he understood that the invention is not limited to such apparatus. Moreover, it is not indispensable that all the features of the illustrative embodi ment thereof he used conjointly, since they may be employed advantageously in various combine.- tions and sub-combinations.
What is claimed, is:
1. That method of producing substantially constant saturationof a vapor in a compression chamber under varying compression pressures which comprises injecting saturating liquid at a temperature above the temperature due to final compression pressure into the vapor while it is undergoing compression and controlling the injection. automatically in response to both the temperature and pressure of the vapor immediately after it leaves the compressor, throughout saturated condition of the discharging vapor.
2. In combination with a vapor compressor of the character described, a spray nozzle connected to inject a saturating liquid in the form of a fine mist into the compressor; a variable delivery pump connected to the nozzle; a thermostat responsive to the temperature of the vapor as it is discharged from the compressor and connected to exercise a controlling effect on the variable delivery pump; means responsive to the pressure of 35 the discharging vapor; and means connecting the pressure responsive means to modify the controlling action of the thermostat in accordance with the pressure temperature curve at saturation of the particular vapor acted upon.
3. In combination with a vapor compressor of the character described, means connected to inject saturating liquid in the form of a fine mist into the compressor; a variable delivery pump connected to supply said saturating liquid; temperature and pressure responsive devices connected to the discharge side of the compressor and both arranged to control the variable delivery pump in response to relative changes in pressure and temperature; and a signal device connected to signify an abnormal condition of the vapor.
JAMES c. mums, JR.