US1942934A

US1942934A - Hygrometer

Info

Publication number: US1942934A
Application number: US519754A
Authority: US
Inventors: Reeve Lewis
Original assignee: AO Smith Corp
Current assignee: AO Smith Corp
Priority date: 1930-03-04
Filing date: 1931-03-03
Publication date: 1934-01-09
Anticipated expiration: 1951-01-09
Also published as: GB349941A

Description

Jan. 9, 1934. REEYE 1,942,934

HYGROMETE'R Filed March 5, 1931 INVENTOR.

Lewis Reeve A TTORNEY.

Patented 9, 1934 PATENT OFFICE 1.942.934 Y HrGaoME'rEa Lewis Reeve, Milwaukee, Wis., assignor to A. 0.

Smith Corporation, Milwaukee, Win, a corporation of New York Application March 3, 1931, Serial No. 519,754,

and in Great Britain March 4, 1930' This invention relates to devices for making hygrometric measurements, the object, of the invention being to provide means for recording or indicating the absolute humidity of a gas.

In industrial installations wherein air, other gases or mixtures of gases and air are employed, it is often desirable to know the absolute percentage of water vapor in the gas. Knowledge of the moisture content of the gas is important in operating apparatus and processes which are 1 affected by moisture, and especially when the moisture content of the gas has a detrimental effect upon the results desired.

For example, in operating a blast furnace or cupola, it is the common practice to heat the air for combustion to a relatively high temperature before injecting it into the furnace. If water vapor is present in the air, it is detrimental to the reactions which take place in the cupola or blast furnace, and it is necessary to use a greater volume of air for each ton of material treated. Thus heat is required to preheat the excess of air to the desired temperature and still more heat is required to preheat the undesired watervapor in the air prior to its injection into the furnace. 7

The operation of the open hearth and other types of furnaces in which gaseous combustibles are used may be adversely affected 'by'the presence of water vapor in the combustion gases. It is desirable to regulate and control the water vapor or moisture content of gases used as reagents in various chemical processes wherein the moisture content may produce side reactions-pr otherwise adversely affect the desired chemical reactions. a

For the above reasons, it has heretofore been proposed to remove the moisture from the gases prior to their use in the above mentioned in- 'dustries. I

In order to provide a check upon the emciency of the moisture removing apparatus, the present invention makes it possible to determine and record directly the absolute humidity of thegas being employed.

In carrying out thisinvention, the gases, having an undetermined absolute humidity, are first brought to a predetermined constant or dry bulb temperature and are thereafter caused to contact'with a wet bulb thermometer at a velocity which will tend to remove the saturated gases in the vicinity of the wet bulb wick so that the. wet bulb temperature will be accurately obtained. The wet bulb thermometer is provided with any suitable and well known mechanism and recordture.

ing chart for recording. the temperature thereof. This chart is graduated for absolute humidity readings in place of or in addition to the wet bulb temperature readings. This is made possible by the fact that the gases passing in contact with the wet bulb thermometer are at a definite, predetermined and constant dry bulb temperature and. the absolute humidity will therefore vary only with the wet bulb tempera- In lieu of the recording instrument or in addition thereto the wet bulb thermometer may be graduated in absolute humidity units for the predetermined dry bulb temperature.

The accompanying drawing illustrates diagrammatically the' preferred apparatus for carrying out the above described method.

In the drawing, the numeral 1 refers to a constant temperature bath in which a tubular coil 2 is disposed. A gas supply pipe 3 conducts the gas of undetermined absolute humidity into the coil.

The constant temperature bath is provided with a heating element 4 and/or. a cooling coil 5 which may be automatically controlled in any desired manner to maintainthe bath at a constant temperature. Located within the bath or immediately adjacent thereto is a cell or. receptacle 6 in which is disposed a bulb 7 of a wet bulb thermometer. The cell 6 is connected with 8 the outlet of the coil 2 and the gas, after passing through the coil, is conducted through the cell past the wet bulb 7. The cel1'6 is connected with a water reservoir 8 through a pipe which connects the lower portion of cell 6 and reservoir 8 and extends through the bath which is main- 'tained at constant temperature. {The water in the reservoir and cell levels off and water is provided to the water chamber in the receptacle 6 at the temperature of the gas in the gas chamber of receptacle 6 andat the temperature of the constant temperature bath 1. The wick 9 is disposedor'i or over the bulb '7 of the thermometer so as to maintain moisture on or around the bulb, and the free end of the wick is extended through a constricted opening in a wall between the gas chamber and the liquid chamber. The wick being threaded and extending more or less loosely through the constricted opening maintains a uniform wetting of the bulb '7' and supplements the wall or. partition between the gas chamber and the water chamber so that the main supply of water is isolated from the gas stream. This arrangement prevents undue evaporation and loss of water and an undue or material no humidification oi the gas. The wet bulb 7 of the thermometer is connected to a suitable recording instrument 10 having a chart 11 so graduated as to record the absolute humidity. The temperature of the bath 1 should be above the dew point temperature of the gas and for this reason, for gases which are nearly saturated, it is desirable that the bath be maintained at a temperature above the temperature 01 the incoming gas.

The invention provides an arrangement whereby the thermometer is materially unaffected by conditions except the cooling which is produced by the evaporation of the water which is supplied to thebulb 7 in constant quantity, at constant temperature and at the temperature of the 1 v desirable, however, that the bath temperature be dew point, a recep acle having a chambered 'portion for gas and a chambered portion for containing liquid constituting a part of said conduit, a wet bulb thermometer having its bulbous end disposed in said receptacle, and means to maintain a supply of liquid in the liquid containing portion of said receptacle.

2. A device for determining humidity which comprises means including a gas conduit for bringing gas to a constant temperature, a receptacle having a chambered portion for gas constituting a part of said conduit and another enclosure communicating with said chambered portion constituting a liquid container, a thermometer having its bulbous end disposed in said chambered portion, a liquid supply tank connected with the liquid container to maintain a supply of liquid in the container, and means to supply the liquid to said container at constant temperature. 4

3. A-device for determining humidity of a gas which comprises means including a gas conduit for maintaining the gas at a constant temperature, a receptacle having a gas chamber communicating with said conduit and a liquid chamher, a wet bulb thermometer having its bulbous end disposed in the gas chamber, a wick carried by the thermometer for maintaining moisture on and around its bulbous end, means forming a constricted opening between said chambers for receiving the wick of said wet bulb thermometer, and means to maintain a supply of liquid in the liquid chamber at a predetermined level and temperature.

4. A device for determining humidity of a gas which comprises means including a gas conduit for maintaining the gas at a constant temperature, a receptacle having a gas chamber communicating with said conduit and a liquid-- chamber, a wet bulb thermometer having its bulbous end disposed in the gas chamber, a wick carried on and around said bulbous end having a free end disposed to be extended into said liquid chamber, means forming a constricted opening between said chambers for receiving the free end of the wick, and a liquid leveling tank for maintaining a supply of liquid in the liquid chamber at a predetermined level.

, 5. A device for determining humidity of a gas eter having its bulbous end disposed in the gas.

chamber, a leveling tank disposed to maintain a constant level of liquid in said liquid chamber, q

and a conduit leading from said leveling tank to said liquid chamber through the bath for supplying liquid at constant temperature.

LEWIS REEVE.