US2555812A

US2555812A - Thermocompressor

Info

Publication number: US2555812A
Application number: US9400A
Authority: US
Inventors: Jr John F Plummer
Original assignee: Ingersoll Rand Co
Current assignee: Ingersoll Rand Co
Priority date: 1948-02-19
Filing date: 1948-02-19
Publication date: 1951-06-05
Anticipated expiration: 1968-06-05

Description

June 5 1951` J. F. PLUMMER, JR 2,555,812

Tax-:RuocouPaEssoR Filed Feb. 19, 1948 Hl 5 ATTORNEY,

Patented June 5, 1951 UNITED STATES, PATENT orties.N

THERMOCOMPRESSOR John F. Plummer, J r., Phillipsburg, N. J., assignor to Ingersoll-'Rand Company, New York, N. Y., a

2 Claims.

l Ihisinvention relates to thermo-compressors ofthe steam ejector type which are capable of producing high vacuum pressures.

Ejectors of the type to which this invention appertains are normally used in the rst stages of a thermo-compressor comprising a plurality of steam ejectors which are connected in series, i. e. with one ejector discharging into the succeeding ejector, in order to produce a high vacuum. With this arrangement, the first and perhaps the second stage ejector will be operating below the pressure at which water freezes, that is', at or below 4.5 mm.mercury and, therefore, the nozzles of these ejectors are constantly subjected to icing conditions. It is apparent then that any mois- 'ti'represent in the propelling steam may condense and freeze in or on thenozzle and thereby impair itseliioientoperationz Y Experience has taught that this undesirable icingharacteristic may be eliminated b y superlocating the steam before it expands through the nozzle. Under normal circumstances, however, a sufficient amount of vsuperheat is not available in the steam header to provide a desired amount of superheat at the nozzle due to the radiant heat loss of the steam in passing from the header to the nozzle. That is, in the rst few stages of the thermo-compressor, only a very small weight of propelling steam is necessary to move a large volume of the fluid to be evacuated because of the low pressures to which such fluid is exposed. As a result of this low rate of steam flow, say for example five pounds per hour for the first stage, the per unit, i. e. B. t. u./1b., radiation loss of the steam in passing between the header and the nozzle may become excessive and the steam, though superheated in the header, becomes wet before or upon reaching the nozzle.

The practice has, therefore, been to superheat the steam by an auxiliary or external source of heat at some point near the nozzle thereby preventing icing of the nozzle. Another practice has been to allow the wet steam to expand through the nozzle and in some manner, as for example by an electric heater, heat the nozzle to prevent the formation of ice on its surfaces. These two methods, however, require an auxiliary source of power or heat.

The present invention is to reduce the per-unit heat loss of the steam passing from the header to the nozzle, to such a value that sufficient superheat is retained by the steam to prevent icing of the nozzle. Since the radiation loss of this steam is relatively constant for a given steam temperature, the per-unit heat loss is inversely proporcorporation of New Jersey Application February 19, 1948, Seriai No. 9,400

tional to the flow rate of the steam and, therefore, the per-unit heat loss of such steam may be reduced to the aforesaid Value by controlling its flow rate.

It is accordingly one object of my invention to prevent icing of the nozzle of a steam ejector by reducing the per-unit heat loss of the steam being delivered to the nozzle of a steam ejector.

Another object of my invention is 'to supply steam to the nozzle of a first stage ejector of an ejector series7 in excess of that required to operate said ejector and use such excess to operate the succeeding ejector.

Other objects will be in part obvious and in part pointed out hereinafter.

The drawing accompanying this application,`- in which similar reference numerals refer to similar parts, shows a side View in elevation, partly in section, of a pair of series connected steam ejectors embodying the present invention.

Referring to the drawing, IB and Il indicate, respectively, the first two stages of a `thermocompressorthe nrst stage ejector I0 of which is adapted to operate at or below the freezing pressure of water. In furtherance of this end, the ejector Il) is provided with a non-icing nozzle unit I2 mounted on the ejector casing I3 adjacent the inlet I4 for the fluid to be evacuated. Connected between a steam source (not shown) and the outer end of the nozzle unit I2 is a conduit I5 which is designed to convey energizing fluid or steam to the nozzle unit I2 in excess of that discharged into the casing I3 by the unit I2. Such excess is conveyed from the nozzle unit I2 to the second stage ejector to act as the propelling fluid therefor.

In the form of the invention shown, the nozzle unit I2 comprises a nozzle housing I6 having an orifice I'I at the inner end thereof for introducing propelling steam into the mixing chamber I8 of the ejector, wherein the propelling fluid and the fluid to be evacuated are mixed and carried into the diffuser IS. Adapted to bear on the opposite end of the housingl is an abutting member 20 which forms an extension for the housing I6 and has an opening 2| therein, whereby a portion of the steam supplied to the nozzle housing is allowed to escape to a point external of the ejector Il).

The abutting member 20 is aligned and held in form relation with the nozzle housing I G` by an internally threaded Washer 22 which bears on a sealing ring 23 on the outer end 0f the housing I6 and is clamped thereto by any suitable means, such as the bolts 24.

.the ejector nozzles. vides `a simple and inexpensive means for pre- 3 In order to minimize the per-unit heat loss of the steam delivered to the orifice I1, means are provided within the nozzle unit I2 and spaced therefrom for conveying steam to a point adjacent the orice Il, thereby reducing to a minimum the distance traveled by the propelling steam moving at a low rate of ilow. In this instance, such means is a tube 25 that forms an extension for the conduit I5 and passes through the abutting member 2B and into the housing I6 to a point adjacent the orice I'I. The lower end of the tube 25 is closed and in the side wall of the tube adjacent the end are perforations 26 to permit steam to escape into the space between the tube 25 and the inner surface of the nozzle housing. wherefrom a portion of the steam is discharged into the ejector casing I3 and the excess thereof escapes through the opening 2i into a conduit 2'1 connected to the nozzle 28 of the succeeding ejector I I.

In; the arrangement shown, a three-way valve mechanism 2S is connected in thev conduits l5 and 21 to provide selective operation of the ejectors I 0 and I I.l To this end the valve element 3U of .the valve mechanism has two passages 3i whereby the conduits 21 and i5 may be commuwith the power supply through one of the passages 3 I. Rotation of the element 3B through an -arcof forty-live degrees in either direction from either of the above mentioned positions will eiectively cut-off the power source of both ej ectors.

- Itis now obvious to those. skilled in the art that the present invention permits the eiiicient operation of steam ejectors designed to develope high vacuums without the additional expense of auxiliary orv external heatsource to prevent icing of The present invention proper-unit heat loss of the energizing fluid-delivered to the ejector nozzle.

While I have shown 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. In a thermo-compressor, a plurality of steam ejectors connected in series, nozzles for the ejectors, a tube extending into the nozzle of the rst stage ejector and terminating in a plane adjacent the downstream end of said nozzle for supplying steam thereto in excess of that required for operation of the first stage ejector, an opening in the first stage nozzle, and a conduit connected between the said opening and the nozzle of the succeeding ejector for conveying said excess steam thereto.

2. In a thermo-compressor, a first stage ejector lconnected in. series with a second stage steam ejector, nozzles for the ejectors, a tube extending into the nozzle for the rst stagel ejector and having a closed end lying in the transverse plane of said nozzle adjacent the downstream end thereof, holes through the sides of the closedend portion of said tube for communicating saidtube JOHN F. PLUMMER, JR..

REFERENCES CITED The following references are of record inthe ille of this patent:

UNITED STATES PATENTS Number Name Date 11,810,873. Sims .Jl1ne 16,1931 1,819,366; Lorraine Sept. 27, .1932 Ross Feb. 11, 1941