US2631774A - Thermocompressor - Google Patents

Description

March 17, 1953 J. F. PLUMMER, JR 2,631,774

THERMOCOMPRESSOR Filed March'18, 1948 ms ATTORNEY.

Patented Mar. 17, 1953 UNITED? STATES PATENT OFFICE 1 2,631,774 THERMOCOMPRESSQR John F.-Plummer, Jr., Phillipsburg, N. J assignor to Ingersoll-Rand Company, New York, N. Y., a corporation of New Jersey Application March 18, 1948, Serial No. 15,681

7 (claims. (01. 230-95) This invention relates to thermo -c'ompressors of the steam ejector type which are adapted to develop'relatively high vacuum pressures.

Ejectors of the type to which this invention appertain-s are normally used in the first few stages of a thermo-com-pressor system in which a plurality of steam ejectors are connected in series, i. e. with each ejector discharging into the succeeding ejector. In such a system at least the firststage ejector operates at or below the freezing pressure of water, namely 4.5 mm. of mercury. A t this pressure any moisture entrained in the propelling steam will condense and freeze at the ejector nozzle tip and on the surface of the difiusor passage, thereby causing erratic operation of the ejector and in some instances complete l-oss of the'inlet pressure.

In order to obviate this diflicul-ty the practice has been to either warm the'nozzlebody and the throat portion of the diffuser by some external means, such as steam coils O lectrical heating devices, or to superheat the energizing steam immediately before it enters the ejector nozzle. Although these practices are to a great extent satisfactory, there are, however, inherent disadvantages and limitations associated with these methods. For example, in either method an auxiliary source of heat or power is necessary and in the latter method, though effective in preventing the formation of ice on the nozzle surface, it does not always prevent the'formation of ice on the inner surface of the diffusor. i

In the present invention the icing problem is solved in a simple and highly eflicient manner by utilizing characteristics inherent in the operation of a steam ejector.w During the operation of a steam ejector, there is a temperature differential between the inlet and discharge ends of the nozzle and of the diifusor due to the change in pressure of the fluids flowing therethrough. The magnitudes of these temperature differentials are, of course, dependent on the amount of pressure drop, in the first case, or pressure rise, in the latter instance, of the fluids. In any case there is a flow of heat in the material surrounding the fluid being expanded or compressed. Thus, by providing a flow path of suflicient area in these materials, an adequate amount of heat is conducted, in the one case, from the inlet or warmer end portion of the nozzle to the nozzle tip to prevent the formation of ice thereon, and in the other case from the outlet end portion of the diffuser to the icing zone, i. e. the zone or portion of the inlet end of the difiuso-r where experiments have shown that particles of ice are most likely to adhere.

It is accordingly one object of my invention to prevent the formation of ice on surface areas of steam ejectors by utilizing a portion of the heat which is normally radiated to the atmosphere from the energizing steam.

Another object of my invention is to conduct a Other objects will be in part obvious and in part pointed out hereinafter.

In the drawings accompanyin this specification and in which similar reference numerals refer to similar parts,

Figure 1 is a longitudinal view, in section, of a steam eject-or constructed in accordance with the practice of the invention,

Figure 2 is a similar view of a steam ejector embodying an alternate construction of the present invention, and

' Figure 3 is a transverse view taken through Figure 2 on the line 3-3.

Referring to the drawings and more particularly to Figure 1, I0 designates, in general, a steam ejector having a non-icing nozzle unit II mounted on the inlet [2 of the ejector casing l3. Secured to the inlet I2 is a difiuso-r I4 which, in this instance, has a converging-diverging diffusor passage 15 with the converging orinlet section It being adjacent the inlet passage H in the inlet l2 for the fluid to be evacuated, whereas the" diverging section I'B serves as a discharge passage for the propelling steam and the evacuated fluid.

In order toconduct a portion of the heat available in the fluid flowing through the diverging section I8 to the icing zone l9 in the converging section It, the d'iifusor is constructed so that the thickness of its wall varies inversely with the width of the difiusor passage.

With this construction the portions of the easing wall having the maximum cross sectional area form the opposed end portions of the converging and diverging sections I 6 and I8 and the restricted or throat section 20 therebetween. Since the rate of change in temperature along the diffuser is roughly constant, the rate of heat flow in the casing wall is directly proportional to the cross sectional area presented to such flow and the maximum flow of conducted heat will occur in said end portions and the section 20 of the diffuser casing and, therefore, a suflicient amount of heat will be conducted a relatively short distance to the icing zone 19 from the restrioted and diverging sections 20 and Hi, to prevent the formation of ice particles on the inner surfiace of the inlet section [6. This form of the invention also lends itself particularly to ease in fabrication and an exterior of uniform construction, due to the converging-diverging diifusor passage.

Icing of the discharge end or tip 2| of the nozzle II is prevented in a somewhat similar manner by constructing the inlet end or Warmer portion 22 of the nozzle wall somewhat thicker than the discharge end. The actual thickness of the nozzle wall is, of course, dependent on the temperature differential between the inlet, and discharge ends of the nozzle, and it is merely necessary to provide a flow path of suflicient area to permit a rate of heat transfer which will raise the temperature of the nozzle tip 2| to at least 32 F. In order to restrict the flow of conducted heat toa path along the nozzle and difiusor, they are encased by an insulating material 23.

In an alternate form of difiusor construction,

shown in Figure 2-, an ejector 24 of conventional type, that is, with a relatively thin walled diffuser is provided with a non-icing nozzle unit LI and the diffuser is encased by a jacket 25 which encircles the diffusor casing 25 and forms a fluid containing chamber 2'! therewith. An opening 28 having a removable plug 29 therein, is provided at one end of the housing 25 so that the chamber 21 may be filled with water or any fluid of relatively good heat conducting characteristics to serve as a means for conducting heat from relatively warmer sections of the diffusor toa relatively cooler section, that is, from the sections 20 and I8 to the section It.

In principle, the, alternate form of the diffuser is similar to that of the first mentioned d-iffusor except, of course, in the latter case the thermal circulation of the fluid is the basis for thetransfer of heat. However, it is to be understood that the thickness of the diffuser wall or depth. of the chamber 2 required to prevent icing in the diflusor, is dependent on the thermal characteristics of the. wall or the fluid, as the case may be, and the temperature differential which exists between the warmer and cooler :portions of the. nozzle or diiiusor.

' In any case, it is now. obvious to. those skilled in the art that the. present invention provides a steam; ejector which is capable of operating at orbelow the. freezing pressure of water by utilizing: a, portion of the heat which. was normally radiated to the. atmosphere. Also, by. virtue of its, construction the eflicient operation of the 5 ejector under all conditions is entirely independent, of any external source of heat or power other thanthe energizing. fluid.

While I havejshown and described one form of my invention it is to be understood that various changes and modifications may be made therein without departing from the spirit of the invention as set forth in the appended claims.

I claim:

1. A steam ejector comprising a casing having an inlet and a difiusor, a steam nozzle adapted to said casing for dischargingsteam into the difiusor, and means for conducting heat from relatively warm portions of said diffusor to relatively co.ol portions, said means comprising a closed jacket encircling the difiusor and having a liquid therein.

2. In a steam ejector adapted to operate at or below the freezing pressure of water, a casing having an inlet and a diffuser, a water jacket encircling the difiusor, and a nozzle for discharging propelling steam into said diffusor, the wall of said nozzle being of sufiicient thickness to conduct heat absorbed from steam flowing therethrough to the discharge end of said nozzlefor preventing the formation of ice on the surface thereof,

3. In a steam ejector adapted to operate at very low absolute pressures, the combination of an ejectorcasing forming a converging-diverging difiusor passage, an ejector nozzle for discharging steam into the diffusor passage of the ejector casing, insulation on the external surfaces of the nozzle to force the flow of conductive heat outwardly toward the end of the nozzle, and external means on the ejector casing for inducing the conductive heat of the steam to flow from the diverging section of the ejector casing to. the converging section.

4. In a steam ejector adapted to operate at ver-ylow absolute pressures, the combination of of the casing so as to force the conductive heat of the steam toflow from the diverging section of thecasing to, the converging section.

JOHN F. PLIJMMER, J R.

ERENCES TED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date,

1,521 ,729 Suczek Jan. 6, 1925 2 ,074,480 MacLean Mar. 23, 1937 2,231,090 Ross Feb. 11, 1941

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