Microclimate Cooling for Military Vehicle Crews

Transcription

1 Microclimate Cooling for Military Vehicle Crews SAFE Europe March 31 st 2010 Stephen Hunter Product Specialist

2 W. L. Gore & Associates Established 1958 Operations worldwide Famous GORE-TEX and WINDSTOPPER products 4 divisions Electronics Medical Industrial Fabrics Technically Oriented Fabrics Gore specializes in the development of high performance protective apparel for the harsh and demanding environments routinely encountered by military forces, fire services and outdoor workers throughout the world.

3 Heat Stress A Hot Topic Numerous countries have troops operating in very hot climates. Risk of disablement and even death due to heat stress is very real. Politically high profile. Recognised need for an effective personal cooling solution for foot mounted troops. Vehicles represent a particularly severe problem.

4 Heat Stress and Core Temperature Hypothermia Normal Hyperthermia Heat Stress 34 C C 39 C As exercise and exposure to heat increases, heart rate increases, blood flow to skin increases, skin temperature increases, body core temperature goes up.

5 Heat Stress Habitability and Performance Def Std 0035

6 Heat Stress Diminishes Vigilance Testing to quantify the Effects of Heat Stress Goal understand the influence of thermal stress on vigilance Conduction auditory signal detection while walking on a treadmill in different temperature conditions Finding Increasing body temperature impairs attention and vigilance Missed signals [%] Core Body Temperature [ C] Source: From et al, J. o. Occ. Med., Vol. 35, No 7, 1993, p 271 ff

7 Heat Stress Affects Performance Study Goal Find out why there are many more crashes in summer Investigation of temperature distribution of days with and without accidents and near miss occurrences Finding Higher heat stress on hot days significantly increases the chance of severe pilot errors C and lower 25 to 29 C 30 to 34 C 35 C and higher Source: Froom et al, J. o. Occ. Med., Vol. 35, No 7, 1993, p 271 ff Heat stressed helicopter pilots are more likely to crash

8 Conditions inside an Armoured Vehicle Crew-space Temperature Vehicle Engine Vehicle Electronic Systems Solar Radiated Heating Crew Outside air temperature (environmental conduction)

9 Interior Temperatures in AFVs Vehicle Type Location Ambient temp ( C) Interior Temperature Degrees above ambient (Average) (Max) M114 ARV Driver Crew M113 APC Crew LVTPX 12 Driver Commander Cargo M109 SPH Crew Driver M60 tank Turret Average temperature range Average temperature above ambient Potential temperatures in vehicle 39.3 C 58.7 C Data taken from Medical Aspects of Harsh Environments Vol. 1 (2001) Ralf Goldman Chapter 1 Introduction to Heat-Related Problems in Military Operations

10 The Cost of Traditional Cooling Goal is to avoid crew core temperature going above 37.5 C Traditional approach is to cool the whole crew space with an Environmental Control System. This has a direct impact on vehicle design and performance. Power required to cool crew space Weight, space and cost for ECS Range, speed & manoeuvrability of vehicle. Environmental temperature Hatches open or closed???

11 Cooling Strategy Efficiency Trade-off Power Required Def Std 0035 Ambient temp of 21 C Crew Core Temperature Maintained below 37.5C MACRO-CLIMATE Spot Cooling Directed Air Efficiency MICRO-CLIMATE (Individual Cooling Vest)

12 Individual Cooling Solutions Phase Change ICE / GELL Evaporative or Forced Air Wicking Materials Liquid Circulation

13 Body Thermal Control Process Depends on body weight ~80W for 75kg Basic metabolic heat production Metabolic heat production due to activity ~41 C Activity increases set point Ideal Set point 37 C Core Body Temperature ~30 C Depends on ambience conditions and clothing Dry / Conductive / Convective heat loss Evaporative heat loss. Sweating mechanism drives missing heat loss

14 Heat loss through Sweating Evaporating sweat Skin Surface Heat loss

15 Advantages of a forced air system Facilitates the Body s natural thermal control process Sweat evaporation Utilises systems already present in the vehicle ECS If not, the power, weight, space impact is least Practical in tethered and untethered format Very low logistic burden

16 The Gore Active Cooling Concept EFFICIENT COMFORTABLE SAFE Active Cooling Vest worn under body armour close to skin (typically over UBACS). The vest provides an efficient way of introducing air to the skin surface Cooling is achieved by removing saturated air, and enhancing the rate of sweat evaporation, at skin level.

17 Structure and Operating Principle Garment is a 2 layer construction. Both layers have Bump spacers to create air paths. Outer layer is impermeable. Inner layer is controlled permeability. Air, pumped between the layers passes through inner permeable layer to wearers torso. Sweat evaporation facilitated by removing saturated air. Blood cooled at skin level circulates and helps regulate core temperature. Cool Hot Skin Saturated Air out Dry Air in

18 Cooling Air Supply Untethered System Self contained rechargeable Blowers Tethered System Air from vehicle ECS

19 Tethered Variant Designed for fixed crew positions. (Predominantly in vehicle). Operates with air from vehicle ECS.

20 Cooling Performance Vehicle Crew Version This performance information was derived from independently conducted habitability testing for the Titan and Trojan (UK MOD armoured engineering vehicles). No cooling vest, no IPE The habitability requirement was considered failed in two crew positions even without IPE. With the Gore Active Cooling Vest worn, all crew positions passed, with full IPE being worn in both A1 and B2 conditions. A test with full IPE and no cooling vest was not conducted as the risk to participants was deemed too high. With cooling vest and full IPE

21 Untethered Variant. For dismounted troops or non-fixed crew positions. Self contained for out of vehicle use. Can charge in vehicle.

22 Cooling Performance - Foot Mounted Version Based on Def std C (10% RH), UK BDU + CBA + 19kg load, 5km/hr on treadmill Demonstrated stabilisation of core temperature and doubling of work-time (reduction in rest 6hrs in conditions Cooling Power and distribution maintained under compressive loading Excellent distribution of cooling effect Skin temperature in different body zones compared with non cooled

23 Longer Work Periods Shorter Rest Periods No Vest Work 120 mins Rest 134 mins With Vest Work 161 mins Rest 80 mins

24 Main Garment Features One Size Fits All Left Hand/ Right Hand Configuration Soft, Light Materials Comfortable to wear Non burn or melt Air transport layers Easy connection to vehicle ECS Snap in and easy release hose connectors Integrated Dual Blowers Convenient side location Low profile Dust Filtration 6 hour duration Very quiet in operation

25 Validation and Testing Tethered Habitation Trials by Qinetiq (2007) A1 A2 A3 and B2 conditions System met the requirements Failure with no vest Untethered Portsmouth University dept of Sports Physiology (July 2007) Met concept of doubling 6hrs in conditions Qinetiq March 2010 Field trials conducted in Turkey, Morocco and Iraq. Extensive in house laboratory testing.

26 Role Compatibility

27 The Challenges of System Evaluation Physiological effectiveness is proven Several trials have now demonstrated core temperature control under body armour using ambient air temperatures up to 46 C User perceptions are more challenging It s an extra layer Does it add more thermal burden when off? Cooling sensation can be subjective Body reacts to change Normalisation is unremarkable once achieved Side by side comparison not easy to make Education, expectation and briefing is key.

28 Cool The Man Directly With Air!! Vehicle Benefits Save power Save weight Save space Gain range Gain manoeuvrability Crew Benefits Control core temp Better performance Situational awareness Reaction Time Cognitive ability More comfortable

29 Current Status EFFICIENCY COMFORT SAFETY System now specified as part of Titan and Trojan ECS In trial and evaluation phase in several countries