ArmoredMedical Research Laboratory

Fort Knox, Kentucky

PROJECT NO. 2 - OPERATIONS AT HIGH TEMPERATURES

First Partial Report

On

Sub-Project No, 2-22, Determination of the Amount of Heat Transmittedto the Fighting Compartment of Tanks Under FieldConditions

Project No. 2-22 17 August 1943

1

ARMORED MEDICAL RESEARCH LABORATORYFort Knox, Kentucky

Project NTo. 2-22724-1 GNOML 17 August 1943

lo PROJECT: NOo 2 - Operations at High Temperatures * First PartialReport on: Sub-Project Mo, 2-22, Determination of the Amount of Heat Transmitted to the Fighting Compartment of Tanks Under Field Conditions.Authority - Letter Commanding General, Headquarters ArmoredForce, Fort Knox, Kentucky, 400o 112/6 GMOHD, dated September 24, 1942,

b 0 Purpose - To determine the adequacy, from the standpoint ofheat dissipation by the crew members, of the limited rate of ventilationwhich is provided through the gas canister in a gas-protected tanko

2o DISCUSSION:

a ® Owing to the space requirements of the gas canister and otherequipment required in the conversion of the ventilating system in U4 tanksto the positive-pressure type for gas-protection, the rate of ventilationthrough the canister is limited. At the present time it appears that arate of no more than 175 cfm is possible.

b 0 This limited rate of ventilation is in sharp contrast to thequantity of air flowing through the crew compartment of the standard M4tank (buttoned-up) which varies from 500 cfm'with engine idling to morethan 2000 cfm when the engine is operating at cruising speed. Because ofthe great reduction in ventilation, the question is raised as to whetheror not the air flow is sufficient to absorb and remove the heat releasedinside the tank and the moisture given off by the crew during the periodsof continuous operation with the tank buttoned-up.

c. Data with respect to the adequacy of the reduced ventilationfrom the standpoint of heat and moisture removal were obtained during actualdriving tests on the range with a full crew in the tank. Details of "thetest procedure and results are presented in the aopendix.

3o CONCLUSIONS:

a c A rate of ventilation of lr’5 cfm in the crew compartment ofthe experimental M4A3 tank (without special insulation of the transmissionand final drive housing) does not remove the heat or the moisture at suf-ficient rates to maintain a tolerable atmospheric environment within thetank during a continuous period of buttoned-up driving, even on a moderatelywarm summer day.

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b 0 If the anticipated combat conditions with respect to enemyuae of gas are such that the gas-protected tank must operate buttoned-upand be continuously prepared for attack by chemical warfare agents forprolonged periods in moderately warm areas (where, for example, the tem-perature and humidity exceed 85° F 0 and 60 percent H0 H 0 , respectively)then additional facilities for crew cooling will be required*

4o RECOMMENDATION:

That this report be distributed to the agencies concerned withthe development of gas-protection of tanks 0

Prepared by:

Lto Colo Theodore F e Hatch, SnCLto Robert H c Walpole, SnCLto Glasselle So Lawson, Info

/ -

s' / '/'

APPROVED . * c *'• s;

WILLARD VACHLEColonel, Medical Corps

Commanding

3 Incls.

#1 - Appendix#2 - Tables 1 thru 3#3 - Figures 1 thru 6

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APPENDIX

In the standard series Ml Medium Tank the rate of ventilation throughthe crew compartment with the tank buttoned-up varies from 500 cfm at idl-ing engine speed* up to rates in excess of 2000 cfm with the engine operat-ing at cruising speed* In contrast to this, in the experimental gas-pro-tected tank (MlA3) described in a recent report from the Laborstory**, arate of ventilation of only 175 cfm is provided through the gas canister.Owing to the limited space available in the tank for the canister and otherparts of the ventilation equipment it does not appear that a higher rate ofventilation during gas protection can be anticipatedo

Field observations and Laboratory measurements have shown that evenwith the high rate of ventilation provided in the standard tank, the solarheat absorbed and the heat given off by the transmission and final driveand the moisture released by the crew are sufficient-to raise the tempera-ture and moisture content of the air within the tank an appreciable amount.In view of this fact question may properly be raised as to the adequacy ofthe limited ventilation which would be available through the canister in agas-protected tank, from the standpoint of heat and moisture removals

TEST PROCEDURE

Data collected under summer climatic conditions at Fort Knox arereported herewith. The tests consisted in operating the tank on the high-way and cross-country in accordance with the standard schedule shown inTable 1. This schedule, which may be referred to as a "standard tank day",is not necessarily representative of a typical day under actual field con-ditions but contains the elements of such a day c In each test the tank wasfully manned and at intervals throughout the day temperature readings weretaken in the tank according to the schedule in Table 2 0 Observations onthe crew included initial and final body weights and temperatures, the bodytemperature at the end of the lo5 hours of buttoned-up driving in the after-noon and a record of the water consumption and excretion during the day c

Tests were run on the experimental tank on 3 different days, one a moderatelycool day with little sun, the second an average summer day with variable sun-shine and the third e day of moderately high temperature with substantiallycontinuous sunshine* For comparative purposes, a similar test was carriedout with a standard tank, also on a moderately warm day with fairly continuoussunshine* At half hour intervals during each day of test the following measurements were taken at the Laboratory central weather station: (1) dry bulb

� Approximately 500 cfm in the M4A2, liUAJ and MIA*; 1000 cfm in the M1A1.** Project No, 3° Toxic Gases in Armored Vehicles, Second Partial Report

on Sub-Project No, 3~9 - Determination of Ventilation Requirements forGas-Proofing Tanks of the Ml Series 0 23 June 1%3°

2

temperature in the shade, {2) wet bulb temperature in the shade, (3) windvelocity, (4) solar radiation on a horizontal surface„ The climatic datawere taken at a point approximately 3 miles from the driving range butsimultaneous check readings of temperature and humidity on the range re-vealed no differenceso Interior surface temperatures in the tank weredetermined by means of thermocouples attached to the metal under conven-iently located nuts 0 Dry bulb temperatures at the various crew positionswere measured by hanging thermometers and the moisture content of the airin the bow and turret was determined by means of an aspirating psychrometerwhich had been checked against the fan-operated psychrometer at the controlstation,.

RESULTS

The records of temperature and humidity within the experimentaltank and in the standard vehicle are shown in Figures 1 to 4o The climaticdata for the four days are also shown on the graphs„

ao Performance of experimental pressure tank compared withstandard aank, Figures 1 and 2 give the surface and air temperatures andthe humidity inside the standard and experimental tanks respectively, underclosely comparable outside conditions» Although the tests were run on twodifferent days, it will be observed that the outside dry and wet bulb tem-peratures and the solar radiation values were practically the same. Thewind velocity was somewhat lower in test 2 with the pressure tank. Atmos-pheric conditions inside the two tanks, however, were strikingly different.The dry bulb temperatures did not differ gre tly but there was a generalelevation of the wet bulb temperatures in the experimental tank as comparedwith the standard vehicle resulting from the increased moisture content ofthe air. This is shown clearly in Table 3 which gives the increase inraoisuire content of the tank air over outside air for both vehicles. Atthe end of the morning and afternoon periods of operation with the tanksbuttoned-up, the moisture content of the air in the standard tank averagedapproximately 30 percent in excess of that in the outside air* In thepressure tank, on the other hand, the excess moisture content averaged62 percent at the end of the morning period and 113 percent in the after-noon. These striking differences resulted from the fact that there wasinsufficient rate of air flow through the gas-protected vehicle to absorbthe moisture given off by the crew members. As a result, rapid deteriora-tion of the atmosphere from the standpoint of crew comfort occurred.Further indication of the effect of the limited ventilation is seen inFigure 5 which shows the increase in effective temperatures* in the two

* The effective temperature scale combines in one reading the effects oftemperature, humidity and air movement upon heat loss from the humanbody. An environment having a dry bulb temperature of 105° and a wetbulb of 85° F and zero air velocity, for example, has an effective tem-perature of 90° F, This is equivalent to a saturated atmosphere of 90°Fand zero velocity. It is also equal to an atmosphere having a dry bulbtemperature of 100°, wet bulb temperature of 90°, and an air velocity of

* 200 fpia0

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vehicles in comparison with the effective temperature level for the outsideair, assuming in the latter case the same air velocity as inside the tanks 0

Effective temperatures for the outside air were substantially the same duringthe two testso Inside the standard tank the effective temperature did notexceed 90°, whereas within the pressure tank and particularly in the bow.the effective temperature throughout most of the day was in excess of 90 ,

and at the end of the afternoon period of buttoned-up operation reached alevel of 96*5°o There was a steady rise in effective temperature duringthe morning and afternoon periods of operation which indicates that evenmore serious deterioration of the inside atmosphere would have occurred hadthe period of buttoned-up operation been continued;, It should be noted thatduring these tests the temperature of the transmission in the pressure tankran uniformly below the transmission temperature in the standard vehiclewith a corresponding lesser radiation heat load which is net included inthe effective temperature scale 0 This improvement resulted, no doubt, fromthe relocation of the transmission oil cooler on the engine compartment deckwhere it was more effectively ventilated. Bow and turret skin temperaturesdid not differ markedly in the two tanks c

Rapid deterioration of physiological function occurs whenthe effective temperature exceeds 90° and when it approaches body temperature(98 0 8), this deterioration will lead to complete collapse if exposure is pro-longed. At 1430 hours, in the case of the experimental pressure tank, thebody temperature of the driver and assistant driver had increased over 3c0°Fo

In the standard tank, on the other hand, the increase in body temperature wasless than lo0°F o The total water loss throughout the day amounted to 6 0 3pounds per man (9=35 pounds for driver) in the pressure tank, and 4*1 poundsin the standard vehicle (6 0 3 pounds for driver)„ At the end of the after-noon period of buttoned-up operation, the crew in the pressure tank showeddefinite signs of heat exhaustion 0

b. Atmospheric conditions inside gas-proof tank in relationto outside thermal conditiona 0 The atmospheric conditions within the gas-protected tank were found to vary with outside conditions, as would be ex-pected* In figures 2, 3 and 4, one notes progressive improvement in thethermal conditions within the vehicle as the outside temperature end amountof solar radiation decreased* Figure 6 shows the effective temperatures inthe bow during the three days together with the average outside climaticconditions* In contrast to the serious deterioration in the tank atmospherewhich was observed on a moderately warm day with continuous sunshine (Figo2), operation of the gas-protected tank on a cool day with low solar radiationdid not produce unacceptable interior conditions (Fig. 4). The effectivetemperature reached a maximum of 87*5° arid there was no significant rise inbody temperature* The total water loss throughout the day averaged 3<>5pounds per man. Attention should be called, however, to the fact that therewas a significant rise in moisture content of the tank air at the end of themorning and afternoon periods of buttoned-up operation, the average increasesbeing 50% and 7 0% respectively e This again attests to the li.nlted capacityof the quantity of air flowing through the tank to take up moisture,,

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On the intermediate day with irregular sunshine andaverage temperature (Fig 0 3), effective tempenatures in excess of 90°were encountered during the afternoon period of buttoned-up operationsonly, with an increase in moisture content over outside air of 75%o Thetotal water loss throughout the day was ? 0 2 pounds per man* and theaverage rise in body temperature at 1430 hours was lo 0° F 0

CONCLUSIONS

a Q It is evident from the findings of these tests that a rateof ventilation of 175 cfra is insufficient to remove the heat and moisturefrom the tank when the outside temperature is of the order of 90° andhigher and the relative humidity above 50% □ If the operation of thebuttoned-up tank is prolonged the crew will suffer serious deteriorationand collapse 0

b 0 At outside temperatures between 80° and 90° F the deteriorationin the tank atmosphere with prolonged buttoned-up operation, the crew willexperience definite fatigue and loss of efficiency.

Co At outside temperatures up to 80° F the tank atmosphere willbe acceptable from the standpoint of crew efficiency and fatigue.

do These findings are of considerable importance in connectionwith tile design and operation of so-called gas-protected tanks since theinstallation crew—cooling equipment would greatly complicate the problem0The need for such equipment depends upon two conditions: (l) climate inthe combat area and (2) the conditions under which the tank must operate,that is to say, the length of time it must be driven completely buttoned-up. The latter depends upon the anticipated nature of attack by chemicalagents o If, for example, the principal advantage of gas protection of theentire tank is to guard arainst ambush or other unexpected attacks thenthe tank must be prepared for attack at all times while in a combat areawhere the use of gas is expectedo If, at the same time, moderately hightemperatures are encountered there will be a need for crew cooling 0 Theseconsiderations must be kept in mind in the further study and developmentof gas protection by means of positive-pressure ventilation through a gascanister 0

* A different crew of higher average body weight were employed in thistesto

TABLE 1

Operating Schedule During "Standard Tank Day"

Legend ofOpero ScheduleIn Figs. 1 to 5 OperationTime*

Driving over highway to range, hatchesopeno

0900 to 1000

Tank stationary, hatches open, crew intank* Fan operating in gas-proof tank;engine idling in standard tanK0

1000 to 1030

Cross-country driving, tank buttoned-up1030 to 1130

Tank stationary, hatches open, enginedead, crew outside<>

1130 to 1230

Cross-country driving, hatches open 01230 to 1300

Cross-country driving, tank buttoned-upo

1300 to 1430

1430 to 1$00 Tank stationary, hatches open, engine

1500 to 1600 Cross-country driving, hatches open.

1600 to 1630 Driving over highway to motor park,hatches open.

* Schedule followed approximately. Time varied slightly in several tests 0

TABLE 2

Location and Scheduleof

Temperature Measurements in Tank

1= Surface Temperatures (Contact thermocouple readings at beginningand end of every halting period)

a« Bow; on front slope midway between two seats.b 0 Turret; roof over gun and on rear walloc. Transmission: front, next to final drive housing 0

2 0 Air Temperatures (Readings every one-half hour)

a c Bow: four locations - driver's left at chest height; asst0

driver*s right at chest height; over transmission, midwayto roof (shielded)*; to rear of and above transmission nextCo turret basket.

b. Turret: four locations - at chest height at each crew position(gunner, conuaander, loader); center of turret directly undergun0

3« Moisture content (wet bulb temperature readings every one-half hour)

a Q Bow: to rear of an above transmission next to turret basketob. Turret: center, directly under guno

* Always higher than other bow temperatures„ Mot included in obtainingaverage bow temperature 0

TABLE 3Rise in Moisture Content

ofTank Air in Experimental and Standard M4A3 Tanks

* End of period of buttoned-up driving,,

TimeMoisture Content - Crains Per Lbo Dry Air

Experimental Tank Standard Tank

Outside BowPercentIncrease Turret

PercentIncrease Outside Bow

PercentIncrease Turret

PercentIncrease

0830 — — —— — 129 134 4 135 5

0900 118 132 12 132 12

0930 —— — —

— 124 134 8 144 16

1000 119 143 20 139 17 119 132 11 134 131030 121 150 24 141 17 119 125 5 126 6

1130* 128 214 62 202 12 112 112 M in 121230 120 152 27 154 28 no 140 27 135 231300 115 173 50 156 35 111 n5 8 131 18

1330 112 197 76 200 79 no 143 30 133 21

1400 108 215 99 204 89 118 151 28' 140 191430* 105 220 -119 218 108 112 i41 22 m ii1500 106 153 44 169 60 108 133 23 136 261530 106 146 38 155 46 103 127 23 129 251600 105 170 62 155 47 103 135 31 142 381630 105 137 30 140 33 — — — —

—

Fig, ITEMPERATURES IN STANDARD M4A3 TANK

MODERATELY HOT DAY

SOLARRADIATION~BTU/SQ

FT/HR.

od

ro

WINDVELOCITY-MPH,

TEMPERATURE°F

Fig. 1

Fig 2TEMPERATURES IN EXPERIMENTAL M4A3 TANK ( 175 CFM)

MODERATELY HOT DAY

SOLARRADIATION-BTU/SO.FT/HR co

rv>

WINDVELOCITY~MPH.

TEMPERATURE°

F

Fig. 2

Fig. 3TEMPERATURES IN EXPERIMENTAL M4A3 TANK (175 CFM)

AVERAGE WARM DAY

SOLARRADIATION-BID/

SOFT/HR

cp

£

MNDVELOCITY-MRH

TEMPERATURES°F

TIME - HOURS

Fig. 3

Fig. 4TEMPERATURES IN EXPERIMENTAL M4A3 TANk(|75CFm)

COOL DAY

SOLARRADIATION-BTU/SQ

FT/HR

-C-

OD

WINDVELOCITY-M.PH

TEMPERATURE°F

Fig. 4

Fig. 5

EFFECTIVE TEMPERATURES IN TURRET AND BOW OF EXPERIMENTALM4A3 TANK (175 CFM)

AS COMPARED WITH STANDARD M4A3 TANK, SHOWING EFFECT OF LIMITEDVENTILATION. MODERATELY HOT DAY WITH CONTINUOUS SUNSHINE.

EFFECTIVETEMPERATURE°

F

Fig 5

Fig. 6

EFFECTIVE TEMPERATURES IN BOW OF EXPERIMENTAL M4A3 TANK(175 CFM)

ON COOL, WARM AND MODERATELY HOT DAYS

EFFECTIVETEMPERATURE°F

TIME - HOURS

AVERAGE CLIMATIC CONDITIONSTEST td tw WIND VELOCITY SOLAR RAD.

I 07.0 75.5 3.6 230

II 81.5 74 0 5.4 145

HI 75.5 68 6 4.5 130

FIG. 6