US2427931A - Hygrometric means - Google Patents

Description

Sept. 23, 1947. E. F. SPANNER I HYGROMETRIC MEANS Filed Dec. 10, 1943 5 Sheets-Sheet 1 NVENTMB:

Edward. From POnnneY' k. ch ATT \I.

Sept.23, 1947. E.F.SPANNER 2,427,931 I HYGROMETRIC MEANS Filed Dec. 10, 1943- 5 Sheets-Sheet 2 IN E NT 0.2 dward. Frank Spanner Sept. 23, 1947. E. F. SPANNER 2,427,931

HYGROMETRIC MEANS Filed Dec. 10, 1943 5 Sheets-Shet 3 Edward From k Spqnn e/r \NVENTOR Sept. 23, 1947. E. F. SPANNER' 2;427,931,

HYGROMETRIC MEANS Filed Dec. 10, '1943 s. Sheets-Sheet 4 Edward Frank fipcmner \N vc N T o R m (QW M Sept. 23, 1947. E. F. SPANNER 2,427,931

HYGROMETRI C MEANS Filed Dec. 10., 1945 5 Sheets-Sheet 5 Edward Frank5pfl el' I \NVENTQK Patented Sept. 23, 1947 UNITED STATES PATENT OFFICE- Application December 10, 1943, Serial No, 513,799

In Great Britain August 30, 1943 This invention relates to hygrometric means and has for objects greater convenience, increased accuracy and more dependability than has been possible in the past with commercial and.

industrial contrivances. l

The invention has reference to hygrometric means of thatkind in which so-called Wet and dry bulb thermometers are used to ascertain the depression of temperature caused by the evaporation of water in a current of the ambient air.

The invention contemplates means by which the flow of ambient air past a remotely disposed and inaccessible wet bulb can be controllably aspirated, thus" enabling wet bulb temperature readings of unvarying. accuracy to be obtained by inducing effective evaporation from the wet bulb whenever desired.

p The invention also contemplates means by which a dry bulb temperature reading of reliable accuracy'can be obtained from a thermometer having a remotely disposed and inaccessible wet bulb bypositively preventing evaporation from said wet bulbon occasion.

The invention also contemplates means by which deleterious materials or substances are re-. moved 'from the current of ambient air flowing past the wetbulb so as to prevent any alteration in the absorptive or evaporative character of the wet bulb clothing. a 'The invention also contemplates the determination of the dew point in closed compartments or storag chambers which may havemetal walls exposed to varying temperature, such as the holds on board ship. i

"The invention also contemplates installations by which tests can be made and recorded every few hours so that adequate-precautions can be taken to protect the cargo or goods stored in closed compartments. v v

Generically the invention provides hygrometric means comprising a single thermal responsive element, an absorbent clothing for said element, means for wetting said clothing withwater, a chamber for said clothed element, sealing means for'said chamber, means for aspirating the air to be tested past said sealing means and over said clothed element temporarily for short periods'of time fully to depress the temperature of said element .and means connected to saidelementicrascertaining the therma1 condition of said element 'instagnant air and in flowing air.

J In the drawings: I

Figure ,1 is a schematic showing, partly in section, of one form oitest apparatus; Figure 2 is an exterior view of Figure 1;

2 Claims. (01. r3 -sas) 2 Figure 3 is a diagram showing an installation as an example of how the invention may be applied; t

Figure 4 is a view showing a fragment of a temperature graph chart obtained from the apparatus shown in Figure 1;

Figure 5 is a schematic showing, partly in section of a modified form of test apparatus.

Figure 6 is a' diagram somewhat similar to Figure 3 but in which only a single indicator is employed in conjunction with a multiple way switch.

Figure 7 is a diagram somewhat similar to Figure 6," but in which a multiple way valve is associated with the multiple way switch.

Figure 8 is a diagram of a three compartment installation operated automatically every three hours.

Referring to Figures 1 and 2, a. is the casing containing the thermal responsive element of a thermometric device, such for example as an electrical resistance, b is a tube of textile or other absorbent material which encloses the operative end of the casing a and continues as a wick b that passes through the perforated guard 0 into the tank d that contains distilled water.

The casing 11 and enveloping tube 12 are sealed into a small closed chamber e having an exhaust pipe 1 and an inlet valve that may consist of a thin metal disc g'having guide legsh and which normally, for example' by the action of gravity, covers the perforations in the seating k that forms part out the bottom of a chamber Z having a plug of non-hygroscopic dust collecting material n of known kind supported therein.

In the installation shown in Figure 3 there are three compartments X, Y and Z, each of which is fitted with a test apparatus of the kind shown in Figures 1 and 2, the thermal responsive elements in the casings a being connected to the thermometric indicators, shown by way of example as recorders 0, located at testing stations at, y and adisposed remotely in convenient positions whilst the exhaust pipes are connected to the suction pipe line p through control cocks :0 y and 2 located at the stations as, y and 2 respectively.

In Figure 3 the pipe line 10 is shown as connected to a direct acting aspirator q by way of example only, it being obvious that any kind of air suction means providing the requisite head, may be used.

Recorders such as 0 usually are provided with means by which the graphic record can be interrupted, such as pen-lifting contrivances, and in the present instance it is assumed that when recorders are used,normal1y the pens 1' of all the air from the compartment X through the filter 4 is extremely small since the means provided en= sure that this is reduced to the mini-mum necessary to depress the temperature fully and in a reliable way.

Owing to the presence of the filter material n the aspirated air is freed of solid particles before it contacts with the tube b and owing to the use of distilled waterthere is substantially no deposition of foreign substance on the absorbent material clothing the bulb or on the surface of the bulb so that the effectiveness of the evaporation material n, past the valve disc 9 and through the chamber e over the wet tube b enveloping the casing a. g M x The evaporation of the water saturating the tube b, by the abstraction of heat in'iknownj man ner, depresses the temperature of the casing' ii temporarily, thus causing the pen 1 to tracethe;

downwardly tending oblique line 1: on the chart as thedrum sis rotated by the clockwork relativelyto time and this obliquitycontinues'until the temperature due to the'v'aporation ceases to change, thereafter the line w parallel with the hori ontallines' of the chart is traced and thetest isfinished.

To economise in timeian'd .to enable a cnumber of readings in museums? relation tov be taken by one person-making the test, as soon-as the cock 3: is opened,'the inspector maygo to the second station, say y,-drop the pen r on tothe chart on the drum of'the recorder o atthat station to obtain a test line it parallel withthedatum line, open the cocky mango totheLthird station a, drop the pen ton to the charton the drum 8 of the recorder 0 at that station to o b'tain'atestlline u parallel with the datum line, open the cockz then go to the-neststation and-so on, returning to station a: in froin about iive to ten minutes ora se. m c a d l we 9 the stations 21, 2 andso on in proper order to obtain a set of charts similar to' that shown in F l c fenefor-each; of; the compartments X, l Z .c ,7 I c,

On e char hawn inflisifia wi d at a value precisely similar to the readingof a dry luth rme e n nd in ca e-sea .va ue, e ci e y; imil the sadine ia et blllbt b rons e the c nd ons und r t t hus. aalblilfigj-the relative humidity; and dewpoint of the mb n ai to; e sce t in ds r efe rin these wet and dry bulb readings to'astandard dew pointchart. I N a is to be obse ed:thatial ho shoelra in he mqm tr c. is cuss jtad term n 99t wear bulb a t bul a in s. th a u a of the r a s is elia eceuseythe reta evaporation can be regulated from zero for the dry bulb reading to a predetermined and effective rate of evaporation byfcreatingand main taining a head of negative pressure in the pipe line pwhilst taking a wetbulb reading. 7 e A particular advantage that accrues from the apparatus shown in Figures 1 and 2 is that it can :be-so proportioned'that it can be stowed or placed in a position that is accessible only atlong intervals of time say every tw threeormore months. g

Continued service dependsentirely on the supply of waterandit is one-feature-of; the invention that in the apparatus shown in Figures 1 and 2, evaporation and hence-loss of water cannot take place except duringtest, owing to; the valve disc g, and the cocks r1, y} and: winch positively shut off all accessof "air. Furthen-Ithe quantity of water evaporated during each test is always maintained at a high standard; also, it is to be noted that although the quantity of waterevaporated during each test will vary with the dew' point of the ambient air, it is quite easy 'to; assume a worst possible condition and to calculate the volume of water necessary to make attest-say, every four hours for sixty days, that is three hundred and ixty tests and add a safety margin of a generous kind to ensurereliable rv c -s;

Allthe, results can be obtained on aflsin gle chartby using a, multiple way switch for con-v necting the thermal responsive element of 'any testapparatustoa single recorder 0, providing a multiple way valve for connecting the exhaust pipe j of that test apparatus tof the exhausting pump g and-operating the switch and valve by hand-atjproper time intervals'to obtain readings from the thermal responsive elements. in se-' quenee, the switch and valve in some cases being mechanically coupled to eliminate all risk of ir 'slllarmam q -k When it is desired to maintain continued 0b servationof the conditions irithe several com partments or enclosures automatically, the switch and the valve maybe linked together mechanically and operated'by power means at stated intervals of time suificientlyseparated (say by 40 more than two hoursl'to enable the thermal responsive elements to acquire the temperature of the ambient atmosphere ineach compartment.

The initial step in every test is, topbserve if the indicator remains steady for about; say,

thirtysconds or to obtain the tracing'of ailine similai to the l ineu of Figure 4 for, say, about one half-minute andthe final tfiip is to, observe if the indicator remains steady for about, say, sixty seconds or to obtain the tracing oi aline s mi etfioJth ne. w of ur fo sa about e. i ute and the. s i a i m s be tained; until the; penr tra'ces a1ine'such as w parallel to the datum line for at least one min ute, thusshowingthat the Wet bulbtemperature has' fallen to a. steady level proper h 1 Inidity of thearnbient air, thatis, the air being drawn past the wet bulbto cause evaporation.

In the arrangement shown in Figure 5 the tube 1), of textil or. other absorbent r'nater ialenvel- 0 oping'thje casingja of the thermal responsive lem t, a t i d' d normally du in tes s 11 the; pre u l descr ede m e casingJ-A with its envelopin tube b is sealed 6 intoiafclosedchamber, ehaving an exhaust pipe 7o saturateditemporarilywith. a small quantity of.

water which may be deliveredto'i't nomawater supply, pipe 15 through the measuring 'valve't included in thefwaterl'supp'ly, said valve be operated after the? dry bulb reading-has been taken.

over the tube b to the pipe Land thence'tot the pipeline p; The flow of ambient air ove'rthe wet bulb' causes efiective evaporation and afall of temperature similar to that indicated by the line iv in Figure 4, the terminal line to parallel with the datum line being dependent upon the dew point of the ambient air.

- In Figure tithe exhaust pipes fare so disposed that the cocks x 11 and 2 are in juxtaposition and the electrical conductors from the casings a are led to the multiple way switch A and connected to the contacts I, 2, 3 and II, l2, I3 so that when the mechanicall connected pivoted contact arms 4 and 5 co-operate with the contacts I and H respectively, the indicator is electrically connected to the temperature responsive resistance in the casing a in the compartment X and the cock 2 has to be opened, when the contact arms 4 and co-operate with the contacts 2 and I2 respectively, the indicator 0 is electrically connected to the temperature responsive resistance in the casing a in the compartment Y and the cock g has to be opened and so on.

In Figure 7 the exhaust pipes from the easings a in the compartments X, Y and Z are connected to the branches m 1 and 2 respectively,

of the body f containing a revoluble plug 1 having a portway f so that the pipe line 20 from the air suction means q can be connected to any of the chambers e by moving the handle F appropriately. To obtain indications 01' recordings of the thermal conditions in the compartments X, Y, Z, the contact arms 4 and 5 of the multiple way switch A are extended backwardly and connected to the handle F by the connecting rod 20 so that when the aspirator q is connected to the chamber e in the compartment X the indicator 0 or the recorder o is electrically connected to the temperature responsive resistance in casing a located in the same chamber and similarly for the chambers e in the compartments Y or Z, selection between the recorder o and indicator 0 being effected by the two way switch B.

In Figure 8 the branches :0 y and a as well as the contacts 1, 2, 3 and II, l2, I3 are equiangularly spaced, the spindles of the plug F, the contact arm 4 and the contact arm 5 having worm wheels 2|, 22 and 23 respectively mounted thereonly. These worm wheels co-operate with worms 24 mounted on the spindle 20 rotated by the electro-motor 25. The electro-motor 25 operates intermittently, say for example, every hour, under the control of the clock switch 26 having a contact arm 21, rotated by clockwork (not shown) once in every twelve hours, and contacts 28, of which twelve are provided with the electromotor 25 is to be operated every hour. The contact arm 21 and contacts 28 are connected in electrical circuit with the local battery 29 and relay 30 to close the power contacts 3| and complete the circuit of the mains through the electromotor 25 for a sufficient period of time to move the portway f and the contact arms 4 and 5 accurately and positively to the next succeeding operative position.

It is to be understood that the multiple way" valve, the multiple way switches and the clock controlled relay power switch shown are meant to represent only ordinary known devices capable; of -operating to produce the required result and may be replaced by any other known'contrivances for the same purpose.

data as to the dew point'of the ambient air'in proximity to the thermometer which are of par;- ticular value in enabling the ventilating conditions of the stored goods or substances to be modified so as to preserve said goods orsubstances from damage by heat: and moisture.

This invention is especially applicable to conditions on board ship where condensation in a hold causes wetting of the cargo and irretrievable damage to grain (by providing conditions favourable to germination or mildew or decay) to metal (by rust and corrosion) to ammunition (by decomposition) and indeed to most stowage.

To avoid condensation on the ship's side, deck and bulkheads bounding a hold, it is necessary that the dew point of the air in the hold should be kept below the atmospheric temperature outside of the holds and to avoid condensation on cargo in the holds, it is necessary that the dew point of the air in the hold should be kept below the lowest temperature to which the cargo has been exposed until the cargo has warmed up.

Knowledge of the dew point in a hold is an essential preliminary to obtaining control of the dew point, and this invention is concerned with methods of accurately securing this knowledge.

Certain knowledge, frequently, of the dew point in the holds is therefore of supreme importance and this knowledge can be obtained from published charts when the wet and dry bulb temperatures have been ascertained by the means described hereinbefore.

The present invention is sharply distinguished from known arrangements for a similar purpose in that the condition of the air in the closed space is measured in the space itself, although the value of measurement is recorded at a considerable distance away, thus avoiding the inaccuracies due to the changes that arise in known installations when air is tested after having been aspirated through long pipes, the temperature of which varies at different parts, thus modifying the moisture content and temperature of the sample sufficiently to render it comparatively valueless for testing purposes.

I claim:

1. Hygrometric means comprising a single thermal responsive element, an absorbent clothaspirating the air to be tested through said chamber and over said clothed element temporarily for short periods of time fully to depress the temperature of said element, a controlling valve for said inlet closed by gravity when aspiration ceases and means connected to said element for ascertaining the thermal condition of said element in stagnant and in flowing air.

2. Hygrometric means comprising a single electrical resistance thermometric element, a remotely located recorder for said thermometric element, an absorbent clothing for said thermometric element, means for Wetting said clothing with water, a chamber for said clothed element, an air inlet to said chamber, remotely located

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