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# Wearable Engine-Driven Vapor-Compression Cooling System for Elevated Ambients

[+] Author and Article Information
Timothy C. Ernst

Cummins, Inc., Columbus, IN 47201

Srinivas Garimella1

George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0405srinivas.garimella@me.gatech.edu

1

Corresponding author.

J. Thermal Sci. Eng. Appl 1(2), 025001 (Aug 20, 2009) (10 pages) doi:10.1115/1.3159478 History: Received December 01, 2008; Revised April 18, 2009; Published August 20, 2009

## Abstract

The development of a wearable cooling system for use in elevated-temperature environments by military, fire-fighting, chemical-response, and other hazardous duty personnel is underway. Such a system is expected to reduce heat-related stresses, increasing productivity and allowable mission duration, to reduce fatigue, and to lead to a safer working environment. The cooling system consists of an engine-driven vapor-compression system assembled in a backpack configuration, to be coupled with a cooling garment containing refrigerant lines worn in close proximity to the skin. A 2.0 l fuel tank powers a small-scale engine that runs a compressor modified from the original air compression application to the refrigerant compression application here. A centrifugal clutch and reduction gear train system was designed and fabricated to couple the engine output to the refrigerant compressor and heat rejection fan. The system measured $0.318×0.273×0.152 m3$ and weighed 4.46 kg. Testing was conducted in a controlled environment to determine performance over a wide range of expected ambient temperatures $(37.7–47.5°C)$, evaporator refrigerant temperatures $(22.2–26.1°C)$, and engine speeds (10,500–13,300 rpm). Heat removal rates of up to 300 W, which is the cooling rate for maintaining comfort at an activity level comparable to moderate exercise, were demonstrated at a nominal ambient temperature of $43.3°C$. The system consumes fuel at an average rate of 0.316 kg/h to provide nominal cooling of 178 W for 5.7 h between refueling.

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## Figures

Figure 1

Air compressor details

Figure 2

Compressor intake and compression strokes

Figure 3

Compressor enclosure layout

Figure 4

Reduction gearing to compressor

Figure 5

Compressor test facility

Figure 6

Finalized portable cooling system

Figure 7

Isometric views of the system

Figure 8

Reduction gear train

Figure 9

Compressor layout

Figure 10

Test facility schematic

Figure 11

Cooling system performance summary

Figure 12

Heat duty versus engine speed (Tevap,coolant=28°C, Tambient=43.3°C)

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