Characterizing the performance of alternative evaporative cooling pad media in thermal environmental control applications

This paper outlines the test procedure and describes how the alternative pad performance is affected by pad thickness and pad materials in the thermal environmental control applications. Many experimental pads were tested including one made of nonwoven fabric perforated pad and one made of coir fiber material. A wind tunnel experiment was performed to obtain equations for heat and mass transfer coefficients for the evaporative process through various thickness of alternative pad media. Heat and mass transfer coefficients are nondimensionalized and curve fitted to yield the working equations: (1) coir fiber pad: h(H)/h(M) = 0.32 rho(a)C(Pa)Le(2/3) (Le(s) / Le)(1/4),and (2) nonwoven fabric pad: h(H)/h(M) = 1.89 rho(a)C(Pa)Le(2/3)(Le(s) / Le)(1/4); where h(H) is heat transfer coefficient, h(M) is mass transfer coefficient, rho(a) is air density, C-pa is specific heat of air, Le is Lewis number, and Le(s) is Lewis number at water temperature. A determination for cooling efficiency in a wind tunnel system is also developed to relate efficiency, face velocity, and static pressure drop across pads. For a 15 cm pad, static pressure drops across the perforated pad and cooling efficiencies varied from 48 to 108 Pa and 81.19 to 81.89%, while 60 to 130 Pa and 89.69 and 92.86% for coir fiber material pads respectively under operating air velocities of 2.0 to 3.0 m/s.